Radioactive Materials Techniques Course

OESO Radiation Safety Division Duke University Medical Center

1

Purpose To give laboratory technicians useful and practical information on the basic principles of radiation and how to handle radioactive materials in order to maintain safety and compliance Table of Contents Topic Page Radiation & Radioactivity 2 Radiation Interactions and Bioeffects 11 Radiation Sources and Background Radiation 17 Fundamentals of Radiation Protection 18 Radiation Dose Limits and Radiation Dosimetry 21 Radiation Detection & Measurement 25 Practical Aspects Radioactive Material Handling 33 Nuclide-Specific Information 35 Radiation Safety Program 39 Conclusion, Radiation Safety Contacts, and Resources 44

2

I. RADIATION AND RADIOACTIVITY Ionizing Radiation

What Is Radiation?

Ionizingionizes [strips electrons from] atoms; includes:

Non-Ionizingmany other modes of interaction; includes:

Particulate-alpha-beta-neutron- etc.

Electromagnetic

3

Radioactive vs. Radiation

Radiation Source

[radioactivematerial or X-ray

device] Radiation

Irradiated Material

4

Ionizing radiation is radiation having sufficient energy to strip electrons from (or ionize) atoms or molecules. Ionization forms ion pairs consisting of free electrons and a positively charged nucleus. To strip an electron from an atom or to break a chemical bond requires a minimum amount of energy, depending on the location of the electron or bond. To ionize a hydrogen atom requires 13.6 electron-volts (eV) of energy. Nuclear transformations release energies in the thousands to millions of eV and thus can cause many ionizations per transformation. Nuclear Stability

Why Some Atoms Decay:Nuclear Forces and Stability

p proton

p

p

neutron

Beryllium Atom [6Be]

Forces acting on 6Be nucleus

n n

n

electrostatic repulsion

nuclear force

nucleus electrons

* 5

This figure illustrates the electrostatic forces on a stable, non-radioactive 6Be nucleus. The protons and neutrons in the atomic nucleus are held together by the nuclear force. The nuclear force is very strong, but only acts over very short distances, roughly a couple of times the radius of a proton. Electrostatic forces also act on the nucleus, pushing the positively charged protons away from each other. The electrostatic force is much weaker than the nuclear force, but acts over much longer distances. Like charges repel and opposites attract; hence the positively charged protons repel each other and attract the negatively charged electrons in the electron shells.

Neutrons have no electric charge, and therefore exert no electrostatic forces. Neutrons can be thought of as the glue that holds the nucleus together, because without them, the protons would fly apart. This is why all atoms larger than hydrogen have at least one neutron, and why a stable nucleus must have about as many neutrons as protons. In fact, as the atomic number Z increases, it requires more neutrons than protons to make the nucleus stable, so that the

3

heaviest stable nuclides have about 1.5 neutrons per proton. Although the decay of a radioactive atom is a random process, the probability of its occurrence can be predicted. The Curve of Nuclear Stability

The Curve of Nuclear Stability

Z (n

umbe

r pro

tons

)

N (number of neutrons)

N = Z

N ? 1.5 Z

Unstable too many protons

Unstable too many neutrons

* 6

Chart of the Nuclides

Z (n

umbe

r pro

tons

)

N (number of neutrons)

Unstable too many protons

Unstable too many neutrons

*7

Stable nuclides have an ideal ratio of protons and neutrons to balance the competing nuclear and electrostatic forces. If the ratio of protons to neutrons differs from this ideal ratio, the nucleus becomes unstable and will undergo radioactive decay in order to achieve a more stable ratio. Some nuclides must decay through a whole chain of radionuclides to reach a stable configuration of protons and neutrons (e.g. radon progeny). Radionuclide and Half-Life

Nuclide vs. Radionuclide

Nuclide - general term referring to any known isotope, whether stable (about 290) or unstable (about 2200), of any chemical element Radionuclide an unstable (radioactive) nuclide

- Shleien (1998)Nuclide Designation:Where:

A = the atomic mass (no. protons + no. neutrons)Z = the atomic number (number of protons)X = the symbol for the chemical element

Note: Physical/Chemical properties depend on Z!

ZA X

* 8

Radioactive Decay & Half-Life [T]

A(t)/Ao

0

___

___

___

___

___

___

___

___

Negative Exponential Decay Curve

Ao Decay Constant [] = 0.693/TA(t) = Aoe-t = Aoe-(0.693/T)t

= Ao()t/T

1.0

1T 2T 3T 4T 5T 6Ttime

09

Each radionuclide (a.k.a. radioisotope) decays at a specific rate per unit time. This rate can be represented mathematically by a term called the half-life (T), which is not effected by physical or chemical factors and has the units of time (e.g., seconds, days, years, etc.). A half-life is the time required for half the original number of radioactive atoms in a sample to decay into atoms of a different chemical element. Hence, the radioactivity of the sample will be half its initial value in one half-life. The half-lives for some radioactive nuclides used in research are listed in Table 1.

4

TABLE 1: Half-lives and Decay Constants for Selected Nuclides

ISOTOPE HALF-LIFE (T) DECAY CONSTANT ()

Hydrogen-3 12 years 0.0578/yr

Carbon-14 5730 years 0.000121/yr

Sulfur-35 88 days 0.00788/day

Iodine-125 60 days 0.0116/day

Phosphorous-32 14 days 0.0495/day

Phosphorous-33 25 days 0.0277/day

Chromium-51 28 days 0.0248/day

Activity

Radioactivity Units

Activity Amount of radioactive materialcurie (Ci): 3.7x1010 disintegration/second

1 Ci = a lot of of activity [based on 1 g radium] adult human has ~0.1 Ci 14C

1867-1934

1859-1906

1852-1908

becquerel (Bq): 1 disintegration/second

1 Ci = 37 kBq = 2.22x106 dpm [disintegration/minute]

1 Bq = tiny amount of activity [SI unit] adult human has ~3,700 Bq 14C

10

Amount of radioactive material is not generally measured in common units of mass or volume. Instead, a quantity of radioactive material is measured in a unit based on the number of atoms decaying per unit time or activity. The conventional unit for quantity of activity in the United States is the curie (Ci), defined as that quantity of radioactive material in which 3.7 1010 (37 billion) atoms disintegrate per second. This definition was originally based on the decay rate of one gram of radium-226. Note that like all units of activity, the curie specifies an amount of radioactive material based on the number of radioactive disintegrations per unit time it produces, not by mass or volume of material. Further, the term disintegrations per second (dps) is not necessarily synonymous with the number of particles emitted by the radioisotope per second, since some decays produce more than one type of radiation or particle per decay. Since the curie is a large unit of activity, the terms millicurie (mCi) or microcurie (Ci) are most often used, as shown below.

5

Another unit for quantity of activity is the disintegration per minute (DPM). The DPM designation is very common in technical literature and facilitates conversion from radiation detection instrumentation readouts in counts per minute (CPM) into units of activity (DPM). It is important to distinguish between these units since a costly mistake can be made if units and/or prefixes are confused.

1 Curie (Ci) = 3.7 1010 dps = 2.22 1012 DPM = 1000 mCi 1 millicurie(mCi) = 3.7 107 dps = 2.22 109 DPM = 1000 Ci 1 microcurie (Ci) = 3.7 104 dps = 2.22 106 DPM

The scientific community generally uses units of the metric or International System (SI). The SI unit for activity is the becquerel (Bq), defined as one (1) disintegration per second (dps). The conversions between Bq and Ci are shown below.

1 Ci = 3.7 1010 Bq or 37 GBq 1 mCi = 3.7 107 Bq or 37 MBq 1 Ci = 3.7 104 Bq or 37 kBq

Decay Equation The activity (A) of a radioactive sample is related to the number of radioactive atoms (N) by the decay constant () from the general decay equation:

A = N Where

= (ln 2)/T The following examples illustrate the decay equation: Example 1: Find the activity of 38 billion 32P atoms No = 38,000,000,000 atoms; (32P) = 0.0495 d-1 Ao = No = (0.0495 d-1)(3.8E10 atoms) = (1.88E9 decays/d) / [(24 hrs/d) (3600 s/hr)] = 22,000 decays per second (Bq) To convert to Ci, (22,000 Bq) (1 Ci / 37,000 Bq) = 0.59 Ci The decay of the radioactivity is then described by the same equation as the decay of the number of radioactive atoms (see side 9):

A(t) = Ao e-t or, equivalently A(t) = Ao (1/2)(t/T)

6

Example 2: Find the activity of a P-32 sample on August 1 if the original activity (Ao) was 1.5 mCi on July 6 of the same year. (T = 14 days). The elapsed time has been 26 days.

A(26 d) = 1.5 mCi e-(0.693/14 days) (26 days) A(26 d) = 1.5 mCi (1/2)(26d/14d) = 0.41 mCi = 0.41 mCi Specific Activity Recall that the curie does not mention anything about the mass or volume of the radioactive material in which the specified number of disintegrations per second occur. The concentration of radioactivity (amount of activity per unit volume or mass) is called the specific activity. The specific activity is used to determine the activity of a known volume withdrawn from the stock bottle of radioactive material. When radioactive material is ordered from a supplier, the specific activity as well as the total activity being ordered is normally given. Many radiolabeled compounds are offered for sale in two or more specific activities. Generally higher specific activity compounds are more expensive for a given isotope. Radioactive contamination is generally more difficult to control when using higher specific activities. Work with the lowest specific activity compounds possible for a given experiment. The maximum specific activity possible for a given radionuclide is proportional to the decay constant () for that nuclide and inversely proportional to the half-life. This is why for example P-32 compounds (half-life = 14 days) can be produced with much higher specific activities than C-14 compounds (half-life = 5730 years). Commonly used expressions for specific activity include mCi/mg, mCi/ml, mCi/mMole, and DPM/ml. Radiation Types

Principal Types of Ionizing Radiation

Gamma () - photon X-ray (X) photon

Alpha () helium nucleus- comes from heavy nuclei [Z > 82]Beta () electron250 keV max: "High Energy Beta"Neutron (n) uncharged

ELECTROMAGNETICPARTICULATE

Custom: categorize radionuclides by type of radiation emitted

11

Ionizing Radiation Types & Penetrating Abilities

ALPHA

01

42 ++

00, X

BETA

GAMMA & X-RAYS

NEUTRON

Paper [or dead layer of skin]Plastic

Lead or Concrete

10n

Waterhigh E

low E

Radiation Source

12

7

Alpha Particle () An alpha particle originates in the nucleus of the atom and is composed of two protons and two neutrons; basically, it is a helium nucleus. It is a fairly large particle and results from the decay of relatively large atoms having 82 or more protons (Z > 82). When an isotope undergoes alpha decay, the atomic mass (A) of the nucleus will be reduced by four and the atomic number (Z) by two. An example of alpha decay is: 88

22686

22224Ra Rn He +

Radium-226 emits an alpha particle and is transformed into Radon-222. The Radon-222 is also unstable and emits an alpha particle. Usually after emitting an alpha particle, the new progeny nucleus is left in an excited state and emits gamma rays as the nucleus progresses to the resting state. The decay of radium leads to a chain of radioactive progeny products that eventually produces a stable isotope of lead. Alpha particles are mono-energetic (approximately 4 to 9 MeV each). The range (distance that the radiation will travel) of an alpha particle is quite short, i.e., only a few centimeters in air. Due to their short range and weak penetrating ability, detection of alpha particles requires specially designed instrumentation. Alpha-emitting radioactive material is not generally used in the research lab, except in consumer products such as smoke detectors and static control devices.

Beta Particle () A beta particle originates in the nucleus. In the most common type of beta decay, a neutron decays into a proton plus an electron. Because the mass of the parent neutron is slightly higher than the mass of the proton/electron pair, the difference in mass is converted to energy (E = mc2). This mass difference is shown in Table 2.

TABLE 2: Masses of Sub-atomic Particles1

PARTICLE

ATOMIC WEIGHT UNITS

Proton 1.007276

Electron 0.000549

Proton + Electron 1.007825

Neutron 1.008665

Changes in the nuclear forces before and after the decay release additional energy. The electron created in beta decay acquires some of this energy and is ejected from the nucleus as what we call beta radiation; a beta particle is simply an energetic (high speed) electron.

n p + ++ 1 1

1 From 1986 Recommended Values of the Fundamental Physical Constants as listed in Table 2.10 of Shleien, B.

ed. The Health Physics and Radiological Health Handbook, Silver Spring, MD, 1992, pp. 31-35.

DellHighlight

8

Beta emission is accompanied by a neutrino () or an anti-neutrino () massless, uncharged forms of radiation that carry off a random fraction of the transformation energy. Betas are not mono-energetic like alphas. A sample of beta emitting radioactive material will emit a continuous spectrum of beta energies from zero up to some maximum value (E-max) characteristic of the specific radioisotope. Text references generally quote the E-max values, but the average beta energy is approximately 1/3 of E-max. Most beta decays are accompanied by gamma emission. However, the radioisotopes used in biomedical research are usually pure beta emitters which do not emit gammas. Several of these pure beta emitters are shown in Table 3.

TABLE 3: Some Pure Beta Emitting Radionuclides2

ISOTOPE

E-MAX (KEV)

E-AVG (KEV)

Hydrogen-3 18.6 5

Carbon-14 156.5 49

Sulfur-35 167.5 48

Phosphorous-33 248 76

Phosphorous-32 1710.4 694

All Together Now:14C 14N + (low energy; 156 keV max) [T=5730

y]

32P 32S + (high E; 1,710 keV max) [T= 14.3 days]

- values taken from Shleien (1998)

* 13

Beta Decay An example of beta decay is the transformation of carbon-14 into nitrogen-14. The 14C beta may have any energy from zero to 156 keV; the anti-neutrino carries off the difference between the beta energy and 156 keV. A beta particles range in air is approximately 3.69 meters (12 feet) per MeV. Betas have a much shorter range in denser material such as tissue.

Gamma Rays() Gamma radiation is not itself a mode of radioactive decay, as are alpha and beta decay. Instead, gamma emission accompanies some forms of radioactive decay. Gamma radiation is a form of electromagnetic radiation which originates in the nucleus as a result of radioactive decay. Like all electromagnetic radiation, gamma rays travel at the speed of light and have no mass and no electric charge. In contrast to the continuous energy spectra created by beta and some X-ray emission, gamma radiation is mono-energetic and emitted at characteristic 2 Shleien, B., ed. The Health Physics and Radiological Health Handbook, Silver Spring, MD, 1989, p. 165.

DellHighlight

DellHighlight

DellHighlight

DellHighlight

9

energies. The gamma energy spectrum of a given radioactive decay is analogous to a persons fingerprint and can be used to identify a particular radioisotope. Gamma-emitting material, like beta emitters, finds prevalent use in medical and research procedures as labeled chemical compounds (tracers) and as the basis for various treatment techniques. Due to the lack of charge and mass, gamma radiation is highly penetrating and has an extremely long range. For example, electromagnetic radiation formed in the sun can reach the earth.

What About X-rays?

high speed electron

X-rays

target nucleus[e.g. tungsten]

BREMSSTRAHLUNG X-RAYS

X-ray

CHARACTERISTIC X-RAYShole at lower orbital

electron falls into lower orbital

* 14

X-rays X-rays are electromagnetic radiation photons similar to gamma rays except they originate in the electron cloud surrounding the nucleus rather than the nucleus itself. X-ray radiation takes two forms: characteristic X-rays and bremsstrahlung radiation. X-ray radiation is considered penetrating radiation because it does not have a charge or mass. The range of X-ray radiation, like gamma radiation, can be a quite long.

Characteristic X-rays Electrons are constantly orbiting an atom at specific energy levels called shells. When an electron is ejected from an inner energy shell (particularly the K or L shells) an electron from a higher energy level will drop into the vacancy. An electron vacancy in the K-shell is filled by another orbital electron, resulting in the emission of an X-ray equal to the difference between the two energy levels. Characteristic X-rays are mono-energetic.

CharacteristicX-ray photon

Nucleus

Lower energy orbital

Higher energy orbital Characteristic X-ray Production

Bremsstrahlung Radiation Bremsstrahlung or braking radiation are X-rays emitted when high-speed, charged particles suffer rapid change in speed or direction. When a beta particle passes close to a nucleus of an absorbing material, the strong attractive forces cause the beta particle to deviate sharply from its original path. This change in direction causes the emission of bremsstrahlung X-ray radiation. As the atomic number (Z) of the absorbing material increases, more bremsstrahlung

DellHighlight

10

X-ray radiation will be emitted. This form of X-ray radiation is not mono-energetic, but forms a continuous energy spectrum.

Bremsstrahlung

- X-ray photon

+ Nucleus

Bremsstrahlung X-ray Production

Positron Emitters Another form of beta decay occurs when a proton plus some nuclear binding energy transforms to a neutron and a positively charged beta particle called a positron (+).

11 1 01 1p n+ + + + {2-5}

The positron (positively charged electron) has the same mass as a negative electron, but has a positive charge. Positron emission is always accompanied by the emission of neutrinos () and may be accompanied by gamma emission. Sodium-22 is an example of a radionuclide which decays by positron emission, as shown below.

1122 1022 1Na Ne + + ++ {2-6}

A positron is often called anti-matter because it disappears when it encounters an electron (normal matter). This is annihilation and results in the creation of two 511 keV photons emitted in opposite directions, as the mass of the two particles is converted completely into electromagnetic energy by Einsteins formula E = mc2. These characteristic 511 keV annihilation photons indicate the presence of positrons.

Neutron Activation In general, radiation cannot make a non-radioactive substance become radioactive. Thus, the presence of radioactive materials or receiving an X-ray will not make surrounding materials radioactive. However, exposure to a neutron source such as a nuclear reactor or Californium-252 can make materials radioactive via neutron activation. This process involves the absorption of one or more neutrons by the target nucleus, thereby creating a different (usually unstable) nuclide. Nuclear reactors use neutron activation to produce many of the radioactive materials used in medicine and research.

11

II. RADIATION INTERACTIONS AND BIOEFFECTS Radiation Interactions

Interactions of Radiation with Matter

Ionization: ejection of orbiting electrons from the atom - Gollnick (1994)

Excitation: raising of orbital electrons to higher energy levels within the atom - Gollnick (1994)

Activation: the process of making a material radioactive by bombardment with neutrons, protons, or other nuclear radiation - Shleien (1998)

15

Radiation Interaction: Main Chemical Effects in Tissue

Primary reactions [within ~10-10 seconds of passage of ionizing radiation] - Water molecule dissociates into free radicals:

H2O H + OH Secondary reactions [subsequent 10-5 seconds]

H + H H2 (gas) H + OH H2O (water) OH + OH H2O2 (hydrogen peroxide) from Gollnick (1994) 16

In addition to ionizing atoms in the target material, ionizing radiation may also cause excitation, in which an electron is merely raised to a higher energy level within the excited atom rather than torn from the atom entirely, as with ionization. Excited atoms then emit a photon as the electron drops back down into the lower energy state. Activation is covered in Chapter I. These radiation interactions occur very rapidly in tissue, with ionized and excited atoms or molecules returning to their ground state almost instantaneously. The effects on a molecular or cellular level are dominated by chemically reactive species, primarily those created by the dissociation of water molecules (e.g. hydrogen peroxide). Because many natural physiological processes create these same reactive chemicals, the effects of low radiation doses are indistinguishable from effects of many other normal cellular metabolic activities. Fortunately the body has naturally developed mechanisms to repair the damage caused by these naturally occurring metabolic and radiation-induced chemicals. Only when the amount of damage exceeds the bodys natural repair capability are negative health effects possible. Radiation Dose Units

Units of Radiation Dose

For latent effects (e.g. cancer, genetic effects); if dose 100 rad(1 Gy)

Old: [rad] = 100 erg/gSI: gray [Gy] = 1 J/kg 1 Gy = 100 rad

Absorbed Dose: energy absorbed per unit mass

Obsolete but still on many direct reading instruments;

1 R 1 rad

Old: roentgen [R] = 2.58x10-4 C/kgair(C = coulomb) SI: no SI unit

Exposure: ionization per unit mass air; only for gamma & X-ray

ApplicabilityUnitQuantity

- Shleien (1998); Gollnick (1994); NCRP 138 (2001)17

U.S NRC Quality Factors (Q)

10High-energy protons10Neutrons of unknown energy

20Alpha particles, multiple-charged particles, fission fragments & heavy particles of unknown charge

1X-, gamma, or betaQType of radiation

- from 10 CFR 20.1004; weighting factors from other organizations ( e.g. ICRP, NCRP, ICRU) may differ

*18

12

The roentgen was one of the earliest (1928) units used to measure exposure and measures the amount of ionization produced in air by X-ray or gamma rays. By definition, 1 R = 2.58 10-4 coulombs/kilogram at standard temperature and pressure. It is important to note that the unit of exposure is defined only for X or gamma rays and only for exposure in air. Thus, the roentgen is a measure of the ability of photons to ionize air. One roentgen (R) is a rather large exposure, so frequently the milliroentgen (mR) unit is used (1000 mR = 1 R). Many Geiger counters and most ion chambers are calibrated to read out in terms of exposure rate, e.g., milliroentgen per hour (mR/hr). There is no international system (SI) unit for exposure. Radiation deposits energy when absorbed by matter. This energy deposition leads to the biological effect of ionizing radiation. By definition, the absorbed dose is the energy deposited per unit mass. The unit of radiation absorbed dose is called the rad. One rad represents the deposition of 100 ergs per gram of material. Unfortunately, the rad is difficult to measure and must often be calculated from other measurements. However, for radiation protection purposes, 1 R = 1 rad, for X-rays or gamma rays. But, for beta radiations, 1 R equals some constant times 1 rad, where the constant is dependent upon the beta energy. For example: 1 R 2.6 rad for P-32. Therefore, beta measurements with survey meters which read in R/hr or mR/hr must be interpreted with care. The international system (SI) unit for absorbed dose is the gray (Gy) one Gy = 100 rad. The ultimate aim of a dose measurement system, from a radiation safety viewpoint, is to arrive at a quantity appropriate for predicting biological response independent of the source of the radiation. This goal is only partially achieved with the rad. For example, the biological effect is much greater for alpha radiation than for beta or gamma radiation for a given absorbed dose (in rad) to the biological system. This difference in the biological effectiveness of the radiation has been attributed primarily to the fact that alpha radiation releases more energy and ionizes more particles per unit path length traversed than beta or gamma although the path length is shorter than that for beta or gamma radiations. In order to account for the different biological effects of different radiation types, a quality factor (QF) has been introduced which is used to convert the absorbed dose to a dose equivalent. Quality factors are shown in slide 18. The unit of dose equivalent is the rem (Roentgen - Equivalent - Mammal.). Most biomedical research laboratory situations involve only beta, gamma, or X-ray radiations. For these radiations, the QF is equal to 1 so the dose equivalent (in rem) is equal to the absorbed dose (in rad). The dose to tissue in air from exposure to one Roentgen is about 0.95 rad. Therefore, for X-ray and gamma radiation exposure, the following expression approximates the dose equivalent:

1 R 1 rad = 1 rem [Low LET radiation] One rem is a large unit; so, we usually work in terms of millirem (mrem), where 1000 mrem = 1 rem. The SI unit for rem is the sievert (Sv) one Sv = 100 rem.

13

Radiation Bioeffects

Radiation Bioeffects

DETERMINISTICSeverity increases with radiation doseThreshold ~50 - 100 remDose & dose rate dependent

Examples:Cataract inductionEpilation (hair loss)Erythema (skin reddening)Blood changesSterility

STOCHASTICProbability of occurrenceincreases with radiation doseThreshold ~10 rem, but regulatory models assume no threshold [ALARA!]

Examples: Cancer Induction Genetic MutationsDevelopmental Abnormalities

- NCRP 138 (2001); HPS (1995) Risk Assessment*

19

Among the acute (immediate) effects generally associated with high radiation exposure are acute radiation sickness and skin erythema (reddening) or desquamation (peeling). This type to bioeffect (severity increases with dose) is called deterministic. Long-term effects may include increased incidence of cancer, leukemia, birth defects, cataracts, and shortening of life span. This type to bioeffect (probability increases with dose) is called stochastic.

Radiation is energy moving through space. Radiation dose occurs when that energy is deposited in living cells. The chemical reactions and molecular changes caused by the addition of this energy in turn effects our bodies. The dose, dose rate, type of radiation, exposure to other hazardous materials, health, age, and even genetic predisposition may all contribute to degree of bioeffect. Generally, the higher the dose and dose rate, the higher the probability of biological effects. Therefore, all doses should be kept as low as possible, and it would be better to receive any exposure gradually over a long period of time rather than all at once. In biomedical research, the doses are generally so small that it is not possible to detect any effect. A tremendous research effort has occurred over the last 40 years to determine the effects of radiation on humans. Arguably, more research has been done on the effects of radiation than on any other toxic or hazardous agent. All types of radiation (gamma, X-ray, beta, and alpha) have been studied for both their internal and external hazards. Many groups of people with known exposures (Hiroshima and Nagasaki atomic-bomb survivors, early radiologists, patients treated with radiation for ankylosing spondylitis and other diseases, radium dial painters, and uranium miners) have been followed, and their health status reviewed. This research has provided a large body of data covering radiation health effects. Radiation Dose-Response Relationships

Deterministic Radiation Effects

500 600SkinSkin erythema350TestisPermanent sterility

300 500SkinTemporary hair loss300GIVomiting

250 600OvariesPermanent sterility200SkinReversible skin effects50Bone MarrowBlood cell depression

Dose (rad)OrganHealth Effect

- [Acute, low LET dose] NCRP 138 (2001)

*20

Stochastic Effects

Cancer: incidence begins to increase in populations acutely exposed to >10 rem [0.1 Sv], continues to increase with increasing dose. BEIR V, 1990Genetic Effects: 100 rad of low-dose rate, low LET radiation needed to double the incidence of genetic defects in humans. -BEIR V, 1990; no human hereditary effects seen at gonadal doses

14

Much of the known dose-effect data derives from rather high doses (on the order of 100 rad) where the effects are well known and documented. At these high doses, health effects depend not only on the total absorbed dose but also on the rate at which the dose is received and the type of radiation. The effects of radiation exposure at low doses (say 10 mrad to 5 rad) are less well known and probably masked by other factors. Unlike higher doses, there are no acute (immediate) effects of small radiation doses, and the long-term effects (e.g., increase risk of cancer) are difficult to clearly attribute to a specific cause. Because they are nearly impossible to unambiguously detect, low dose-effects can only be estimated through extrapolation of high dose-effect data. The National Academy of Sciences BEIR V (Biological Effects of Ionizing Radiation 1990) report represents the scientific communitys consensus view on low-dose effects. The position of the Health Physics Society (a nonprofit scientific professional society dedicated to radiation safety) is that any quantification of health risks below an individual (above natural background) dose of 5 rem in one year or 10 rem lifetime is scientifically unsupportable because there is simply no compelling evidence of harmful health effects at lower doses3. To be on the safe side, we assume extrapolation of high-dose data into the low-dose region such that any exposure produces some effect; i.e., there is no threshold dose below which no effects occur. In assuming that any amount of radiation dose, no matter how small, may be harmful, we are obliged to keep our occupational radiation dose As Low As Reasonably Achievable (ALARA). This no threshold theory of radiation dose-effect has driven the ALARA concept which now forms the basis of radiation protection regulations. Ionizing radiation is a weak carcinogen, and ample evidence shows increased incidence of cancer in populations exposed to high doses. The BEIR V report estimates an increased risk of cancer death of 0.8% (0.008) following an acute whole body radiation exposure of 10 rad (10,000 mrad). The normal incidence of cancer death is about 16% (0.16) in the US. Hence an acute radiation absorbed dose to the whole body of 10 rad would theoretically increase the risk of cancer death from 16% to 16.8%. The report cautions that this estimate includes a large degree of uncertainty, noting that ...the probability that cancer will result from a small dose can be estimated only by extrapolation from the increased rates of cancer that have been observed after larger doses, based on assumptions about the dose-incidence relationship at low doses.4 In other words, any increase in cancer incidence following a dose as low as 10 rad is so small it has not yet been clearly detected; so, the increased risk of cancer is based on extrapolating the discernible increases at higher doses down into the low-dose region. Genetic effects are abnormalities occurring in the future children of individuals and in subsequent generations. The BEIR V committee concluded that, based on available data, at least 100 rad of low-dose rate, low LET radiation would be needed to double the incidence of genetic defects in humans. The committee was careful to err on the side of safety in coming up with this estimate, noting that their interpretation ...has the advantage of leading to risk

3 Health Physics Society Radiation Risk in Perspective Position Statement (2001),

http://hps.org/documents/radiationrisk.pdf 4 Committee on the Biological Effects of Ionizing Radiations, Board on Radiation Effects Research, Commission

on Life Sciences, National Research Council, Health Effects of Exposure to Low Levels of Ionizing Radiation [BEIR V], National Academy Press, Washington, DC, 1990, pp. 161, 162.

15

estimates that, if anything, are too high rather than estimates that subsequent data may prove to be too low.5 Pregnant Radiation Workers

Pregnant Workers

You are not officially pregnant until you declare your pregnancy at Employee Health.

Radiation Dose limit to fetus for entire gestation period is 500 mrem.

Fetal badge will be issued to you, if requestedit is changed out monthly.

A consultation about radiation doses to the fetus can be set up with Dr. Robert Reiman (668-3186).

No need to stop radiation work. Can be confidential.

22

Weve known since 1906 that rapidly dividing cells which are undifferentiated in their structure and function, such as embryo/fetus cells, are generally more sensitive to radiation. The embryo/fetus stage is the most radiosensitive part of our life cycle, especially during the first three months after conception, when a woman may not know shes pregnant. When a pregnant woman is exposed to radiation sources, her unborn baby may also be exposed. Because of these factors, the National Council of Radiation Protection and Measurements (NCRPM) and the International Commission on Radiological Protection (ICRP) recommend that an occupationally exposed woman who may be pregnant take special precautions to limit exposure, with a maximum permissible dose equivalent of 0.5 rem during the pregnancy. Nuclear Regulatory Commission (NRC) and North Carolina regulations also establish dose limits of 0.5 rem during the pregnancy. Fortunately occupational doses from the biomedical research use of radioactive material generally fall far below this limit. It is up to the female radiation worker to evaluate the possible risks of occupational radiation exposure to a known or potential unborn child. The NRC recommends that she consider the following facts to help make her decision: 1) The first three months of pregnancy are the most critical for radiosensitivity.

5 Ibid., p.68, 69.

16

2) In most work situations, the actual dose received by an unborn child would be less than the mothers because her body provides some shielding.

3) The dose to the unborn child can be reduced by: a) Decreasing the amount of time she spends in a radiation area b) Increasing the distance between her and the source of radiation c) Shielding her abdomen 4) If she becomes pregnant, she may ask her employer to reassign her to areas involving less

exposure to radiation.

5) When her occupational exposure is below the 5 rem/year limit, the risk to an unborn child may be small in relation to the other day-to-day risks to the unborn during pregnancy. Experts disagree on the exact amount.

6) There is no need to be concerned about sterility, i.e., loss of ability to bear children. The radiation dose required to produce this effect is 40 times greater than the NRCs basic dose limits for radiation workers (5 rem/year).

For more information on this important topic, contact Radiation Safety.

17

III. RADIATION SOURCES AND BACKGROUND RADIATION

Radiation Sources

Natural BackgroundIndustrial UseResearch UseMedical UseMilitary UseNuclear Power Plants

23

Annual Dose to Member of the U.S. Population

[NCRP 93 (1987)]

Other< 1%

Radon55%

Consumer Products

3%Nuclear Medic ine

4%

Cosmic(Outer Space)

8%

Terrrestrial(Rocks & Soil)

8%

Internal(Inside Human

Body)11%

Medical X-rays11%

Other Includes: Occupational 0.3% Fallout < 0.3% Nuclear Pow er 0.1% Miscellaneous 0.1%

Natural 82%

Artificial 18%

Natural (mrem)Radon 200Cosmic 27Terrestrial:-external 28-internal 39Artificial (mrem)-Diag. X-rays 39-Nuc. Med. 14-Consumer Pro. 10-Other ~1TOTAL ~360

*24

Ionizing radiation sources have many beneficial uses. Such sources are widely used to diagnose and treat many diseases, including cancer. Radiolabeled compounds are indispensable in research, and radioactive sources are used to measure tank levels, paper and steel thickness, and other industrial quality control parameters. Other uses include sterilization of surgical equipment, verifying pipe and weld integrity, food irradiation, airport and building security, power production (with less CO2 emission than fossil fuel plants), etc. However, use of ionizing radiation sources creates the potential for large occupational radiation doses. All radiation workers have an obligation to prevent any unnecessary occupational radiation dose. People have been exposed to ionizing radiation since first appearing on this planet. The sources of this natural background radiation include cosmic rays, terrestrial radiation, and internally deposited radioisotopes. The values for the first two depend upon where you live. Cosmic radiation dose is larger at higher altitudes since there is less of the Earths atmosphere for shielding. Areas with large local deposits of uranium or thorium entail a higher than average terrestrial radiation component. The food we eat, the water we drink, and the air we breathe contain such radioisotopes as tritium (hydrogen-3), carbon-14, and potassium-40, among others, as well as uranium, thorium, and their radioactive progeny. The radioactive materials are then deposited in our bodies. Slide 24 illustrates that 82% of the annual radiation dose to the average member of the U.S. population comes from natural sources, and only 18% as a result of human activities.

Radon Radon is a naturally occurring, odorless, colorless, radioactive gas produced by the radioactive decay of uranium and radium that occur in trace amounts in soil and rocks. Radon is chemically inert which allows it to easily move through soil, rock, and building materials. Radon also produces radioactive by-products (progeny) which adhere to dust particles in the air. These decay products are part of the natural decay chain (progeny of Uranium 238, the most abundant isotope of uranium found in nature). The lower part of this decay chain is shown in below. 226Ra 222Rn 218Po 214Pb 214Bi 214Po 210Pb 210Bi 210Po 206Pb

Radium-226 Progeny to Lead-206, the stable (nonradioactive) end-product of the Uranium-238 series.

18

IV. FUNDAMENTALS OF RADIATION PROTECTION Protection Against External and Internal Radiation Hazards

Internal vs External Radiation Hazards

Irradiation [external source]

Contamination [still external, but can be absorbed]

Intake [incorporation via inhalation, ingestion, skin absorption, or via wounds, etc.]

*

25

Radiation Protection Fundamentals

ALL RADIOACTIVE MATERIAL:CONTAMINATION CONTROLUniversal Precautions & monitoring; block intake

EXTERNAL RADIATION HAZARDS:TIME

DISTANCE

SHIELDING

*26

A key concept needed for understanding radiation protection is the distinction between internal and external hazards. An internal hazard arises once radioactive material gets inside the body, while an external hazard comes from radioactive material outside the body. All radionuclides become internal hazards if taken into the body by inhalation, ingestion, or skin absorption. However, whether a particular radiation source can pose an external hazard hinges on a very practical consideration: the ability of the radiation to penetrate the bodys dead layer of skin. Slide 12 (page 5) shows the penetrating ability of various ionizing radiation types. Note that alpha particles and low energy (250 keV) beta emitting nuclides (e.g. 32P), gamma emitters (e.g. 125I), and X-ray devices can penetrate the dead layer of skin and damage the living tissue underneath. Therefore these radiation sources pose an external radiation hazard, i.e. can cause harm even when the material is outside of the body. Protection against external radiation hazards is afforded by the appropriate use of time, distance, and shielding.

19

Radiation Protection: Time

Limit time near source

Dose = (dose rate)x(time)

Reducing the time by will reduce the dose by

27

Time The total dose received from a source presenting an external radiation hazard will depend on the total time spent near the source. Therefore, the time spent near such a source should be as short and effectively used as possible.

Distance

Radiation Protection: Distance

Increase distance from source

Inverse square law: D2=D1(d1)/(d2)

Doubling the distance will reduce the dose rate by

28

Using Distance to Reduce Dose Rate

Example:100 uCi 125I gives 274 mrem/hr @ 1 cm

Whats the dose rate at 10 cm?D = [(274 mrem/hr)*(1cm)2]/(10 cm)2

= 2.74 mrem/hr @ 10 cm (4 inches)

If a source contains an external radiation, NEVER handle it with your fingers; ALWAYS use tongs or forceps

29

A good way to reduce the exposure to external radiation is to use distance. Much of the time, distance alone is enough to reduce the exposure rate from beta emitters to a background level. X-ray and gamma ray radiation usually approximate point sources, and the radiation from such a point source will obey what is called the inverse square law. This law means that, as the distance to a point source is doubled, the exposure rate is reduced by a factor of four.

20

Radioactive Material Handling: Additional Precautions

Secondary Containment

Good practice: Handle RAM only on absorbent paper in spill traysStore RAM in primary and secondary containment (e.g. stock vial inside ziploc bag)

31

Pipetting Techniques

No mouth pipetting Make sure tip is securely attached Hold tip at an angle, against the inside

wall of the vessel, if possible Glide the control button smoothly and

slowly Place, do not shoot, contaminated tips

into waste containers32

Tiny volumes of radioactive material can contain large amounts of activity. This is particularly true of some high specific activity compounds routinely used in biomedical research, for which aerosol droplets too small to be seen by the unaided eye can carry millions of DPM. Radioactive material handlers unfamiliar with this aspect of radioactive material use often find themselves mystified by the appearance of radioactive contamination where there was no visible indication of a spill or leak. Some key principles for preventing the spread of this invisible radioactive contamination include:

Secondary containment: Handle radioactive material on absorbent (diaper) paper in spill trays to prevent contamination of lab benchtops. Store radioactive material containers inside secondary containers (e.g. Ziploc bags or snap seal plastic containers).

Proper liquid transfer techniques: Pipetting creates tiny micro aerosols, clouds of

liquid droplets too small to be seen yet potentially carrying detectable amounts of radioactive material. Ensure that the tip of the pipette is inside, rather than simply above, the container the material is being transferred to. Similarly, eject disposable pipette tips into the inside of an appropriate radioactive waste container rather than ejecting from above the waste container and letting the tips drop some distance into the waste container.

Disposable glove use: Check gloved hands frequently for contamination, while working

with radioactive material, and change disposable gloves often. Remove disposable gloves and wash hand BEFORE touching telephones, keypads, doorknobs, light switches, lab notebooks & pens, or any other commonly handled items.

21

V. RADIATION DOSE LIMITS AND RADIATION DOSIMETRY Annual Occupational Dose Limits and ALARA

Annual Dose Limits (rem)10 CFR 20.1201

0.1General Public [TEDE]0.5Embryo/Fetus (Declared Pregnant) & Minor [TEDE]15Lens of the Eye [LDE]50Skin [SDE,WB & SDE,ME]50Total Organ Dose Equivalent [TODE]: Sum of DDE and

CDE to any single organ or tissue other than eye lens

OR

5Total Effective Dose Equivalent [TEDE]: Sum of DDE, WB for external & TODE for internal, to the whole body[head/neck/torso region of the body]

33

ALARA: NRCs view

ALARA (acronym for "as low as is reasonably achievable") means making every reasonable effort to maintain exposures to radiation as far below the dose limits in this part as is practical consistent with the purpose for which the licensed activity is undertaken

10 CFR 20.1003 34

Occupational dose (of ionizing radiation) means the dose received by an individual in the course of employment in which the individuals assigned duties involve exposure to radiation or licensed radioactive material. Occupational dose does not include dose received from background radiation, as a patient from medical practices, from voluntary participation in medical research programs, or as a member of the general public. The Occupational Dose Limits (see slide 33) are set well below radiation levels known to produce acute health effects. Under normal operating conditions, State and Federal regulations do not permit individual occupational exposure to exceed the occupational dose limits. Although regulations specifying maximum occupational dose limits are intended to minimize risk of injury or ill effects, occupational radiation exposure must be kept As Low As Reasonably Achievable (ALARA). External Radiation Dose Monitoring

Dosimetry Monitoring -External

Laboratories using H-3, C-14, P-33, S-35, and/or Ca-45 - no monitoring required.

Laboratories using P-32 - a finger ring dosimeter is required.

Laboratories using gamma emitters (Cr-51, I-125, I-131, etc), irradiator(s), and/or analytical x-ray equipment - whole body dosimeter is required.

35 36

External dose is that portion of the dose equivalent received from sources outside the body.

22

NOTE: Only radiation having sufficient energy to penetrate the dead layer of skin can contribute to external radiation exposure. For this reason, low-energy beta radiation (such as that emitted by hydrogen-3 {tritium}) and alpha radiation do not contribute to external radiation dose. Four basic principles for reducing external exposure are time, distance, shielding, and contamination control. Therefore, follow these simple rules to minimize your external radiation exposure:

a) Minimize exposure time to radiation sources. b) Maximize distance from the radiation source. c) Place shielding material between you and the radiation source. d) Minimize radioactive contamination of work areas by employing rigorous contamination

control techniques. Measurement of external radiation dose can be accomplished by means of personnel dosimetry monitors such as thermoluminescent dosimetry (TLD) badges, film badges, and pocket ion chambers. External dose can also be estimated by measuring exposure or dose rate using direct reading instruments such as ion chamber or microrem survey meters and calculating dose from exposure time.

Three categories of external radiation exposure are defined: a) Deep-Dose Equivalent [DDE]: For whole body [head, trunk (including male gonads),

arms above the elbow, and legs above the knees] external exposure, the dose equivalent at a tissue depth of 1 cm (1000 mg/cm)

b) Shallow-Dose Equivalent [SDE]: For external exposure of the skin of the whole body [SDE, WB] or the maximally exposed extremity [SDE, ME], the dose equivalent at a tissue depth of 0.007 cm (7 mg/cm)

c) Lens of the Eye Dose Equivalent [LDE]: For external exposure of the lens of the eye, the dose equivalent at a tissue depth of 0.3 cm (300 mg/cm)

Internal Radiation Dose Monitoring

Dosimetry Monitoring -Internal

Thyroid Bioassay - after radioiodine use:

Urine Bioassay - after using 100 mCi/month of 3H (tritium) in unsealed form

You must contact Radiation Safety to conduct urine bioassays!

100 mCi10 mCiFume Hood1000 mCi100 mCiGlove Box

10 mCi1 mCiBenchtopNon-volatileVolatile formsUsage

37

23

Internal radiation dose is that portion of the dose equivalent received from radioactive material taken into the body through inhalation, ingestion, skin absorption, or entry through cuts or wounds. To minimize internal exposures, prevent the deposition of radioactive material in the body by strict observance of good lab procedures and by keeping the work environment within the permissible levels of contamination specified in this manual.

Internal radiation dose assessment results should be expressed in terms of committed dose equivalent [CDE] and/or committed effective dose equivalent [CEDE] when determining compliance with occupational dose limits.

a) Committed Dose Equivalent [CDE]: The dose equivalent to organs or tissues of reference that will be received from an intake of radioactive material by an individual during the 50 year period following the intake

b) Committed Effective Dose Equivalent [CEDE]: The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent [CDE] to these organs or tissues

Several techniques are available for measurement of internal radiation dose. These methods include measurement of radionuclides in air, the body, and excreta.

a) Measurement of Airborne Radioactive Material Concentrations in Work Areas: Registered Radiation Users are generally prohibited from handling volatile, gaseous, aerosolized, or otherwise airborne radioactive material outside of specially designated and properly operating fume hoods. Therefore, the concentration of airborne radioactive material in the workplace is normally not significantly different from background, and measurements of airborne radioactive material concentrations is generally not appropriate for the assessment of internal dose.

b) Measurement of Quantities of Radionuclides in the Various Organ Systems Using Sophisticated Radiation Detection Equipment: An example of this technique is measurement of the quantity of radioactive iodine in the body by means of a thyroid scan. The measured activity is then converted into a committed dose equivalent, which in turn is used to calculate the committed effective dose equivalent. Typically, radiation workers must conduct a thyroid scan any month their use of radioactive iodine [e.g. 125I or 131I] exceeds 1 mCi.

c) Measurement of Quantities of Radionuclides Excreted from the Body: The quantity of radioactive material excreted from the body can be measured by means of urine bioassays. The measured concentration of radioactivity in the urine can be used to calculate the effective dose equivalent for the corresponding intake of radioactive material. Typically, radiation workers must submit bioassay samples any month their use of radioactive material in a volatile form exceeds 5 mCi of 14C or 35S, or 100 mCi of 3H.

Summation of Internal and External Radiation Dose Monitoring Results If regulations require that a worker have both internal (committed effective dose equivalent [CEDE] and external (deep dose equivalent [DDE]) exposures monitored, then the workers internal and external occupational radiation doses must be added together to calculate the Total Effective Dose Equivalent [TEDE]. If only internal monitoring is required or if only external monitoring is required, then the internal and external doses need not be summed.

24

a) Internal dose must be monitored if the worker is likely to receive in one year an intake in excess of 10 percent of the applicable ALIs (Annual Limit on Intake) in Table 12-1, columns 1 and 2, of Appendix B to 10 CFR 20.1001 20.2401, or for declared pregnant women, if they are likely to receive, in one year, a committed effective dose equivalent [CEDE] in excess of 50 millirem.

b) External dose must be monitored if the worker is likely to receive in one year, from sources external to the body, a dose in excess of 10 percent of any of the applicable occupational dose limits, or if the individuals enter a high (dose rate in excess of 100 millirem/hr @ 30 cm from the source/surface) or very high (500 rads/hr @ 1 m from the source/surface) radiation area.

Because this institutions policy on dosimetry monitoring often meets or exceeds the regulatory criteria above, this policy may specify monitoring of workers who do not meet the regulatory criteria. In such cases, the act of monitoring a workers external and/or internal dose does not necessarily constitute a requirement that these doses must be summed when calculating the Total Effective Dose Equivalent [TEDE]. The Radiation Safety Officer will determine whether an individual users Total Effective Dose Equivalent [TEDE] is required to include both external and internal occupational dose.

25

VI. RADIATION DETECTION AND MEASUREMENT Radiation Detection Mechanisms

Means of Detecting Ionizing Radiation

Ionization (e.g. gas-filled detectors)

Chemical Changes (e.g. film)

Physical Changes (e.g. track etch)

Calirometric Changes (calorimeter)

Activation [for neutrons]

38

Because ionizing radiation cannot be detected by the unaided senses, various types of detection instruments must be used to evaluate the level of radiation and/or amount of radioactive material in an area. The proper instrumentation is essential for the accurate measurement of these quantities. For most applications, ionization detectors (such as the gas-filled and scintillation detectors discussed below) suffice.

Common Detector Types

Over responds @ low E [< ~100 keV]; non-linear photon E response; saturation

Reliable, easy to use; prompt response; very common

Geiger Mueller [GM]

Counting gas; rarely used [unfamiliar]

Good energy resolution, etc.

Proportional Counter

Warm up ~ 5 min Response time ~10s Sensitive ~0.1 mR/hr[high pressure helps]

Reliable/simple; detects low E [~20 keV] photons; meas. exposure; high range

Ion Chamber

ConsProsType

Gas Filled Detectors

39

Fragile, less sensitive than NaI

dose equivalent rate (rem/hr,Sv/hr)

Tissue Equiv. Organic

Compromises on sensitivity, energy dependence, ruggedness

Optimize specific performance characteristic

Various Others

Fragile; hydroscopic; does NOT provide dose rate information

Reliable, easy to use; detects low E photons [~2 keV], very sensitive

NaIConsProsType

Scintillation Detectors

40

Gas-Filled Detectors

This design includes ion chambers, gas flow proportional counters, and Geiger-Mueller detectors. These instruments rely on the detection of ionization in gases by radiation to provide charge carriers within the gas-filled chamber. These charge carriers (ions) then carry an electric current between the anode and cathode of the detector. The instruments electronics convert this measured current flow to appropriate units, such as CPM or mR/hr. These systems generally consist of a gas-filled chamber containing an electrode, a voltage supply, a resistor, and an ammeter (current flow meter).

Ion Chambers: The simplest and lowest voltage instruments of this type are ionization chambers or ion chambers. These portable instruments usually use regular air at atmospheric pressure as gas in the detector, although some special designs may use other gases. Ion chambers are primarily used to measure radiation exposure or exposure rate.

26

Proportional Counters: Proportional counters operate at somewhat higher voltages than ion chambers and employ special gases such as argon-methane mixtures. The name of this detector type is derived from the fact that, although the current flow measured by the meter electronics is greatly amplified by an avalanche effect within the gas-filled chamber, the response nonetheless remains proportional to the initial ionization in the detector. Proportional counters are available in both portable and fixed installations, but they are rarely used in biomedical research labs. Geiger-Mueller Detectors: The popularity of Geiger-Mueller (GM) detectors stems from this designs sturdiness, reliability, and low cost. The typical thin-end window GM or pancake GM (PGM) survey meter is adequate for detecting high-energy beta particles and high-energy gamma rays. Some of the radionuclides that may be adequately monitored by use of a GM survey meter are P-32, I-131, Co-57, Tc-99m, Sr-90, Cr-51, and Na-22. While the GM survey meter can detect larger quantities of radioactive material, it is not sensitive enough for smaller amounts of some radionuclides. For example, large amounts of C-14, S-35, or P-33 in a small area may be detected by a thin-end window GM survey meter; but when the amount of activity is spread over a large area or there is a small quantity of the material in one spot, the survey meter may not detect the activity. Similarly, GM meters can only detect relatively large quantities of I-125; therefore, I-125 users are encouraged to use more sensitive (i.e., higher efficiency) instruments. Finally, in very high radiation fields, GM tubes become saturated and stop responding at all. Such intense radiation fields are very unlikely in the biomedical research environment; but users should remember to turn the meter on prior to entering a radiation area so as to recognize this saturation effect in the unlikely event such high radiation levels are ever encountered.

Scintillation Detectors A variety of solid scintillator detectors are available as portable radiation detection instruments and in larger, more sensitive stationary designs such as gamma counters. These devices are useful for low-energy gamma radiation and are becoming more popular for monitoring beta radiation. They are much more efficient than GM meters. Low-energy gamma detectors are recommended for monitoring such gamma emitters as I-125. Liquid scintillation counters are highly recommended for monitoring C-14, S-35, and P-33. The most sensitive radioactive material detection technology readily available to biomedical researchers is liquid scintillation counting. In contrast to small portable systems, liquid scintillation counters are generally relatively large, immobile, and expensive. This technology involves putting the radioactive sample (e.g., research compound, metabolism product, or wipe test) into a vial containing liquid scintillation cocktail. The cocktail contains chemicals that convert some of the radioactive decay energy into light pulses (scintillations), which are then detected by very sensitive photomultiplier tubes within the counter. Because the radioactive sample is in intimate contact with the detection medium (the liquid scintillant), even very weak radiation can be readily detected. Radionuclides which may be detected by a survey meter, but which are more adequately measured in a liquid scintillation unit in order to obtain adequate sensitivity, include C-14, S-35, P-33, and Ca-45. Radionuclides that may only be detected by liquid scintillation counting methods include H-3 and Ni-63. Only non-RCRA [Resource Conservation and Recovery Act - USEPA] regulated LSC cocktails should be used; ensure your LSC fluid is on the list of non-RCRA LSC cocktails on the NCHPS page at:

www.nchps.org/HPsandRadusers.htm

27

Radiation Instrumentation Configuration & Selection

Configurations of Radiation Detectors

Portable Survey Meters: Geiger counters, ion chambers, hand-held scintillators, etc.

Personal Dosimeters TLD & film badges, pocket ion chambers, electronic personal dosimeters [EPD]

Fixed Instruments liquid scintillation counters, gamma counters, gas flow proportional counting chambers, multi-channel analyzer spectroscopy systems, well counters, whole body counters, portal monitors, gamma cameras

*41

Instrument Selection

Step 1: Decide why measurement taken!Dose Rate Measurement

Contamination Survey

Quantifying Radioactivity

Nuclide Identification

Note: Standardize facility instrumentation if possible!

*42

Before selecting the correct instrument, the application must be considered:

1) Type of radiation and the energy range of the radiation to be monitored; i.e.: alpha or beta particles; gamma rays or X-rays; low energy or high energy

2) The purpose for which the measurement results will be used, such as: a) Locating contamination b) Evaluating external radiation hazard (i.e., checking for adequate shielding) c) Measurement of radiation absorbed doses, exposure rates, dose equivalents, etc., from

a source or in a specified area d) Quantifying the amount (activity) of radioactive material in a sample e) Nuclide identification

Efficiency For locating contamination or quantifying activity, knowing the efficiency of the detector for the radiation(s) of interest is critical. Efficiency CPM/DPM; a detector with 50% efficiency would produce 100 CPM per 200 DPM of activity in the measured sample. Table 4 shows approximate efficiencies of various detectors reported by manufacturers for various nuclides.

28

TABLE 4: Detector Efficiencies for Various Radiation

TYPE OF RADIATION DETECTOR TYPE EFFICIENCY/NUCLIDE

Low Energy Gamma NaI (TI) Scintillator 80 - 90% / I-125

Gamma Geiger-Mueller (GM) 5 - 10%

Beta Thin End Window GM 10% / C-14 45% /Sr-90

Pancake GM 10% / C-14, S-35 60% / Sr-90

Plastic Scintillator 16-20% / C-14, S-35 85-88% / Sr-90

Liquid Scintillator 30-60% / H-3 67-85% / C-14, S-35 90-98% / P-32

The efficiency is a conversion factor to convert measurements (in CPM) performed on an instrument to an activity (in DPM). Remember that the efficiency will be both instrument and isotope specific. Also, background must be subtracted from the measured CPM value of the sample, and consistent units must be used throughout all calculations. The following equation integrates all of these concepts and can be used to convert from CPM to Ci. Activity (Ci) = [(CPMsample CPMBackground)/efficiency] x (4.505x10-7 Ci/dpm) It is important to subtract the background count rate (CPMBackground) from the sample count rate (CPMSample), particularly when attempting to measure the radioactivity in very low level (near background) samples. To determine the background count rate B (CPMBackground), a blank or background sample must be prepared and counted. When conducting contamination survey wipe tests, for example, a clean (unused) wipe is counted, and the results of this measurement are used for B.

Dose Rate Measurements and Contamination Surveys

Dose Rate Measurement

Best: Ion Chamber or Tissue equivalent organic scintillator [a.k.a. microrem, microsievert] OK for Emergency Response: PGM [pancake Geiger counter] High Dose Rate or precise X & gamma radiation: ion chamber Beta Dose Rate: complex; accurate measurement requires special instruments. GM gives ballpark

*43

Contamination Survey

Purpose: to locate any possible areas of unwanted radioactive material

GM will detect: P-32, I-125 (large quantities), S-35, P-33, C-14

H-3: a wipe test must be performed

44

A survey meter used to measure radiation dose-related quantities (e.g., mR/hr, rem, mrem/hr, etc.) must not only be capable of such measurements, it must also be properly calibrated and

29

measurement results must be interpreted with care to arrive at meaningful conclusion. Given the complexity of dosimetric measurements, they should normally be left to Radiation Safety staff, who maintain the appropriate instrumentation and expertise. Contamination Surveys are discussed in greater detail in the discussion of wipe test analysis later in this chapter. Quantifying Activity, Nuclide Identification and Geiger Mueller Detectors

For Quantifying Activity & Nuclide ID

Liquid Scintillation Counter: Alpha, beta & gamma emitting nuclides; e.g. urine bioassayGamma Counter: gamma emitting nuclidesWell Counter [NaI]: gamma emittersLow E Gamma Detector: thyroid bioassayNewer Portable MCAs: on site, real time analysis 45

More on Geiger Counters

Most common portable survey meterPancake GM: large detector faceEnd Window: less popular but OKSide Window: [energy compensated] rare but handyDetects alpha, beta & gamma but not technically a dose rate instrumentGMs over respond to low E photons

46

Pancake GMs good for contamination survey but not the best for dose rate

Energy compensated GMs are not for low energy photons

Instruments calibrated for photons are not calibrated for betas unless specifically indicated

- from Shleien (1998), p. 11-17 Survey Meter Operation

Before Use: Dont use an unfamiliar instrument; always "learn" an instrument in a non-operational setting

and become comfortable with it's peculiarities.

Dont use an out-of-calibration instrument; if it's out of date, put it out of service. Survey meters are calibrated (or given operational check) annually by Radiation Safety; fixed instruments are calibrated by user per manufacturers recommendations.

Dont cover detector with disposable glove, cling wrap or plastic to prevent contaminating it (slide 47)

30

Turn it on

before entering suspected radiation area

Perform battery check

Perform HV check if present

Perform operational check [check source]; ideally, compare meter reading with reference value written on meter to verify check source reading hasnt changed.

(slide 48) Using the Instrument:

Turn to proper setting; note [background] reading in area known to be free of radiation sources Turn speaker on if so equipped

Hold the detector about 1 inch from the surface to be surveyed and move about 1 inch/second

During prolonged use, regularly check the condition of the batteries

Notify area users of results; emphasize changed or extraordinary conditions (slide 49)

After Meter Use:

When finished, repeat battery, HV, & operational [check source] checks to verify meter is still working properly; Then turn the meter OFF!

If documentation is required: Record all results - if not on paper, it wasn't done! Include date, location, instrument model & S/N, and your name; Develop pre-printed forms

(slide 50)

Portable survey meters equipped with Geiger Mueller or solid scintillator detectors are generally very reliable and simple to operate. Following the guidance above to obtain useful and credible measurement results.

Removeable Contamination

Removable vs Fixed Contamination

Removable contamination refers to contamination that is deposited on the surface of structures, areas, objects or personnel that can readily picked up or wiped up by physical or mechanical means during the course of a survey or decontamination efforts (i.e. it come up on wipe test)Fixed contamination is bound to the contaminated surface and not easily removed.Labs using low-energy (

31

How to Conduct a Wipe Test Survey

Wipe an area that is 100 square centimeters, approx. 4 x 4 inches.

Store the wipes in an envelope or vial and count them as soon as possible.

Be SURE to wear gloves!

53

Collection Efficiency

Depends on surface and molecule (e.g. glucose easily removed, nucleotides adhere strongly), NOTradionuclide

In most cases, collection enhanced by wetting wipe (factor of 2+)

No significant difference between solvents(Klein et al, 1992; study involving 14C-glucose, 32P-GTP, & 3H2O)

If collection efficiency unknown, assume 10%(ISO 7503, 1988)

54

Counting Efficiency

(Klein et al, 1992)

73.42.367.95.82.80.6Dirty Swab

87.71.383.70.85.80.8Clean Swab93.20.584.84.87.60.2Dirty Filter94.60.694.24.829.15.6Clean Filter

101.31.497.51.643.11.8None

32P14C3HMedia

55

Duke Removable Contamination Limits

Net DPM on wipe per 100cm

Action taken by lab personnel

less than 220 No action required

220-11,000 Clean area; repeat wipe(s)

11,000-110,000 Clean area; repeat wipe(s), notify RSO to verify clean-up

>110,000Cease RAM. Notify RSO.

Immediate cleanup under RSO supervision.

56

Analysis of Removeable Contamination (Wipe Test) Samples

How to Conduct a Wipe Test Survey

Make a map of the area you intend to wipe test. Number each point you wish to wipe.Obtain absorbent material, i.e. filter paper, cotton swab, and number each piece. Wipe bench-tops, door knobs, ref/frz handles, floor, sinks, equipment, anything that could be contaminated.Count wipes in liquid scintillation counter [LSC will detect ALL nuclides] or (for gamma emitting nuclides only) gamma counter

57

Liquid Scintillation Counter [LSC]

Sample Preparation Use labeled filter paper or other absorbent

material and wipe area (100 cm2 minimum) Place wipe in a LSC vial, fill with LS fluid

(enough to cover wipe) & cap Place an unused wipe (blank) into a vial, add

LS fluid, & cap to make a background vial Load sample vials & background vial into LSC

rack and place in the counter Select proper LSC program & count samples 58

32

LSC Pitfalls

Negative result (sample count rate similar to background) means No significant radioactivity in sample

Positive result (sample count rate above background) may mean:

Photoluminescence (in CPMA; fades in minutes)or

Chemoluminescence (in CPMA; fades over hours)or

Radioactivity - channel depends on radiation energy; for biomedical research nuclides, T long enough that counts will be about the same a day later

59

Gamma Counter

ONLY good for gamma-emitting nuclides (e.g. 125I, 131I, 51Cr)

No LS fluid required (easier & cheaper to prepare & dispose of samples!)

Still need a background vial [unused wipe (blank) in a vial]

Load sample vials & background vial into gamma counter

Select proper program & count samples NO false positives with gamma counter

60

Counting Statistics Counting statistics and error estimation are beyond this texts scope, but some general rules can reduce the counting error (standard deviation) of measurement results. Note that since counting error is proportional to the square root of the total number of counts acquired, a good rule of thumb is to count long enough to accumulate 10,000 counts, thereby reducing counting error to ~1%. For example, a sample producing ~1,000 cpm in a liquid scintillation counter should be counted for 10 minutes to accumulate ~10,000 counts. The counting error is then:

Counting Error (counts) = (total counts) = (10,000 cts) = 100 cts Counting Error (CPM) = (100 cts)/(10 minutes) = 10 CPM

Percent Error = (100 cts/10,000 cts) or (10 CPM/1,000 CPM) = 0.01 = 1% As noted on page 25, in the real world background must be subtracted from measurement results to find the actual count rate. If S is the net count rate due to the sample alone (i.e. S = CPMSample CPMBackground) and the count time for the sample and background blank are Ts and Tb respectively, then the count rate error is given by:

Counting Error = {[(S + B)/Ts] + (B/Tb)} Total count time T is optimized (error minimized) when divided between Tb and Ts as follows:

Ts/Tb (optimal) = [(S+B)/B] If T is optimized this way, then the counting error is given by:

Counting Error (CPM) = {[(S+B) + (B)]/ST} When S is much larger than B (high count rate), the counting error (in CPM) for a given optimized counting time (T) is approximated by:

Error (CPM) 1/(ST) [for S >> B] If S >> B, design experiments to maximize S to minimize counting error (and/or reduce T). If B >> S (low count rate), the counting error (in CPM) for a given counting time (T) is approximately:

Error (CPM) (4B/ST) [for B >> S] If B >> S, experiments should be designed so as to maximize the ratio of S/B.

33

VII. PRACTICAL ASPECTS OF RADIOACTIVE MATERIAL HANDLING Specific Activity Revisited

Sense of Scale: How many dpm can fit in a microliter?

Max. specific activity inversely proportional to TSp. Act. = [(ln2)xmass(g)]/[Tx atomic mass]

- Pure 3H (12.3 y): 9,650 Ci/g (2.1x1016 dpm/g)- Pure 32P (14.3 d): 286,500 Ci/g (6.4x1017 dpm/g)Average adult: ~0.1 Ci (220,000 dpm) each 14C & 40KTypical Northern/Southern blot probe specific activity: 2 x 109 dpm/g [www1.amershambiosciences.com]smallest visible speck (unaided eye) ~1 g

61

Radioactive Contamination: The Invisible Menace As noted in Chapter IV, volumes of radioactive material that are too small to see with the naked eye can nonetheless lead to easily detectable contamination. For example, an invisible droplet of material with the readily available specific activity of the Amersham blot probe noted in this slide could contain a billion dpm of activity easily detectable and far exceeding the allowable contamination limits of this institution!

Many radioactive material users have accidentally discovered a subtle characteristic of high specific activity radiolabeled compounds: contamination of work surfaces can occur even when there was no visible indication of a spill or leak. Awareness of this aspect of radioactive material use helps in understanding the importance of the practical guidance in Chapter IV on how to avoid such contamination. Knowing the ease with which radioactive contamination can occur and spread also underscores the necessity of monitoring the workplace both during and after radioactive material use. Finally, a discussion of radioactive contamination leads well into the next topic: Decontamination.

Spills and Decontamination

Is it a Minor or Major Spill?

Depends on number & severity of people affected, nuclide & amount spilled,and likelihood of spreading of contamination

Contact Radiation Safety if: - wipe test indicates >110,00 dpm on a wipe- accidental RAM intake- personal contamination

See AUs SOP for other requirements When in doubt call Radiation Safety

62

Before Clean-up of Spills[Decontamination]

Attend to injured or contaminated persons & extinguish fires FIRST before cleaning up spill

Alert people in immediate area and close off the spill area; Keep uninvolved people OUT!

Volatile radioactive materials: close room windows & doors; leave fume hoods on to exhaust contaminated air

Monitor all individuals before they leave the area; pay close attention to shoes

Assemble clean up supplies & PPE63

The final Chapter of the Duke Radiation Safety Manual covers emergency procedures, including injuries or accidents, major spills, and fires:

www.safety.duke.edu/RadSafety/manual/chap12.asp#SecA All radioactive material users should be familiar with this brief, one-page part of the Radiation Safety Manual. Printing and posting that Manual page in radioactive material use areas is also a good practice.

34

Materials Needed for Decontamination

Decontamination Supplies

Plastic bags Caution Radioactive Material tape Absorbent material (paper towels, blue pads) Decon detergent (rad con) Rope or Tape Portable survey meter (must have) Materials for taking wipes (must have)

64

PPE for Decontamination

Disposable gloves Shoe covers Lab coat Safety goggles

65

Assemble all necessary supplies before beginning a major decontamination project.

Decontamination Techniques

Decontamination

Work from the outside of the spill inward [least contaminated to most contaminated areas]

Place absorbent material (e.g. paper towels or blue pads) over liquid spills.

Place dampened towels over spills of solid materials; be careful NOT to breathe any dust coming from the spilled material.

Be sure towel dampening solution will not react chemically with the spilled material

Wipe test/survey and repeat cleaning until no contamination found 66

Decontamination Waste

Use forceps to pick up paper towels Place towels in a plastic bag Seal the bags for transfer to a rad waste

container. Be sure to add contaminated gloves or

other contaminated disposable material to rad waste container.

67

Documenting Clean-up of Spills

DOCUMENT EVERYTHING! Draw a map and take extensive wipes

of the entire area, remembering to include floors, equipment, handles, etc.

Document final survey, showing area free of contamination

Keep all documentation in your labs files

68

Spill Clean Up Spill clean up can be a difficult and tedious chore, particularly if large volumes of liquid or high specific activity material is involved. Often effective clean up involves repeated cleaning of the contaminated surface many, many times to get the contamination below the levels specified in the Radiation Safety Manual. However, following these procedures will make the job easier, and as always, when in doubt you can contact Radiation Safety for advice and assistance.

35

VIII. NUCLIDE-SPECIFIC INFORMATION

Nuclide-Specific Information

3H14C32P33P35S125I

For more Information on these and other nuclides, Nuclear Safety Data Sheets[NSDS] at:

http://www.nchps.org/HPsandRadusers.htm

69

This chapter provides radiation safety guidance about some of the most commonly used radionuclides in biomedical research. For additional information on these and other nuclides, check the on line Nuclide Information Library at the NC Health Physics Society web site shown in slide 69.

Hydrogen-3 [3H]; also known as Tritium

3H [Tritium]

Least Radiotoxic Nuclide (~60 rem/Ci THO water); ~10 pCi/L naturally in surface watersWeak (18.6 keV max) Beta:- Not external hazard- Not detected by survey meter; need LSC12.3 year T; persistent contamination & wasteHydrogen can change position on labeled molecule, exchange with solvent & migrateRadiochemical decomposition ~1-3%/month (may be faster if frozen); compounds good for ~1 year

70

Tritiums weak beta radiation provides both enhanced safety and practical problems. 3H has very low radiotoxicity; the average adult would have to drink about 80 mCi of tritiated water to approach the 5 rem annual occupational dose limit for radiation workers. The lack of an external radiation hazard eliminates any shielding concerns with 3H; its only a hazard if taken internally. However, tritiums very weak beta radiation cannot be easily detected, obliging users to increased vigilance against contamination. Finally, hydrogen is a fairly mobile chemical element, so contamination eventually appears outside of almost any sealed high activity container, creating chronic contamination issues.

36

Carbon-14

14C [Carbon-14]

Low Radiotoxicity (~2 mrem/uCi ingested); naturally ~0.7 pCi 14C per gram C in live tissueLow Energy (156 keV max) Beta:- Not external hazard- Detectable with survey meter & LSC5730 year T; persistent contamination & wasteStably bound to labeled compoundsRadiochemical decomposition ~1-3%/year; stored compounds good for several years

71

14Cs beta radiation is energetic enough to allow surface contamination detection by GM survey meters, yet too weak to present an external radiation hazard for all practical purposes. Carbon -14 Radiolabeled research compounds tend to be quite stable chemically. 14Cs long half-life limits maximum specific activity but gives these compounds much a longer shelf life than most other nuclides. The long half life also makes contamination issues more severe (they will NOT simply decay away) and significantly increases the cost of waste disposal.

Phosphorous-32 [32P]

32P [Phosphorous-32]

Moderate Radiotoxicity (ingestion: ~30 mrem/Cito bone marrow, 9 mrem/Ci CEDE)High Energy (1,710 keV max) Beta:- External hazard; 3/8 inch plastic stops beta but may also need to shield Bremsstrahlung X-rays- Easily detectable with survey meter & LSC14.3 day T; use quickly - gone in ~5 monthsStably bound to labeled compounds; non-volatile; white vinegar cleans up most contaminationRadiochemical decomposition ~2%/week; stored (-20C) compounds good for several weeks. pH 1%/day 72

32Ps high-energy beta makes this nuclide very easy to keep track of in the lab but also necessitates shielding. Use low atomic number (Z) materials ( inch plastic) for shielding 32P to minimize the intensity of the resulting bremsstrahlung X-rays. Additional high Z material (e.g. lead) may be needed outside the plastic to stop the resulting X-rays (note: the plastic stops ALL of the betas; any radiation detected outside the plastic is X-rays, so additional plastic wont help much). Wear a ring dosimeter and use time & distance (e.g. forceps to manipulate stock vials) when handling this nuclide.

Phosphrous-33 [33P]

33P [Phosphorous-33]

Low to Moderate Radiotoxicity (ingestion: ~2 mrem/Ci to bone marrow, 1 mrem/Ci CEDE)Low Energy (248 keV max) Beta:- Not quite an external hazard; no need to shield or wear dosimetry badges- Easily detectable with survey meter & LSC25.3 day T; use soon - gone in ~10 monthsStably bound to labeled compounds; non-volatile; white vinegar cleans up most contaminationRadiochemical decomposition ~1%/week; stored (-20C) compounds good for several weeks. pH 1%/day 73

33Ps medium-energy beta offers a good compromise between ease of detection and safety. This nuclides 248 keV beta is near the conventional definition of a high-energy beta (250 keV) so intimate contact with stock vials should be avoided. That said, 33P is easily detected with a GM survey meter yet requires no shielding or dosimetry monitoring.

37

Sulfur-35 [35S]

35S [Sulfur-35]

Low Radiotoxicity; ingested ~0.7 mrem/Ci CEDELow Energy (167 keV max) Beta:- No external hazard; no shield/dosimetry badges- Easily detectable with survey meter & LSC87 day T; fairly longLabeled compounds slightly volatile during - 35S-methionine & -cysteine metabolism (cover cell culture with charcoal-impregnated paper)- Thawing (open stock vial in hood)Radiochemical decomposition ~2%/week @-80C but >10%/week @ (-20C); colder is better 74

35Ss beta radiation is energetic enough to allow surface contamination detection by GM survey meters, yet too weak to present an external radiation hazard for all practical purposes. Some 35S compounds (e.g. amino acids cysteine & methionine) tend to volatilize slightly over time; thaw and open these compounds in a fume hood. Similarly, volatile metabolites from 35S-labeled cells can produce small but bothersome contamination in incubators, etc; cover such cell cultures with carbon-impregnated filter paper to eliminate this problem.

Iodine-125 [125I]

125I [Iodine-125]

High Radiotoxicity due to thyroid uptake (ingestion: ~1273 mrem/Ci to thyroid)Low Energy (35 keV max) Gamma:- External hazard; Shield (0.02 mm Pb HVL) & wear dosimetry badges for mCi amounts- Detectable with survey meter & LSC60 day TVolatile if pH 7!) tend to volatilize over time. Iodinations must be conducted only in designated fume hoods specified in the AUs SOP for that purpose.

General Precautions 1. Maintain your occupational exposure to radiation As Low As Reasonably Achievable

[ALARA]. 2. Ensure all persons handling radioactive material are trained and authorized by the AU. 3. Review the nuclide characteristics on (reverse side) prior to working with that nuclide.

Review the protocol(s) authorizing the procedure to be performed and follow any additional precautions in the protocol. Contact the responsible AU to view the protocol information.

4. For nuclides presenting external hazards (e.g. 32P, 125I), plan experiments to minimize external exposure by reducing exposure time, using shielding and increasing your distance from the radiation source. Reduce internal and external radiation dose by monitoring the worker and the work area after each use of radioactive material, then promptly cleaning up any contamination discovered. Use the smallest amount of radioisotope possible so as to minimize radiation dose and radioactive waste.

38

5. Keep an accurate inventory of radioactive material, including records of all receipts, transfers & disposal. Perform and record regular lab surveys.

6. Provide for safe disposal of radioactive waste by following institutional Waste Handling & Disposal Procedures. Avoid generating mixed waste (combinations of radioactive, biological, and chemical waste). Note that lab staff may not pour measurable quantities of radioactive material down the drain.

7. If there is a question regarding any aspect of the radiation safety program or radioactive material use, contact Radiation Safety.

Good Laboratory Practices 1. Wear disposable gloves and a lab coat when handling radioactive material. Remove &

discard potentially contaminated gloves & lab coats prior to leaving the area where radioactive material is used.

2. Clearly outline radioactive material use areas with tape bearing the legend "radioactive". Cover lab bench tops where radioactive material will be handled with plastic-backed absorbent paper; change this covering periodically and whenever it's contaminated. Alternatively cover benches with thick plastic sheeting (i.e., painters drop cloth), periodically wipe it clean and replace it if torn.

3. Label each unattended radioactive material container with the radioactive symbol, isotope, activity, and, except for waste, the unique inventory control number (from the web-based inventory system). Place containers too small for such labels in larger labeled containers.

4. Handle radioactive solutions in trays large enough to contain the material in the event of a spill.

5. Never eat, drink, smoke, handle contact lenses, apply cosmetics, or take/apply medicine in the lab; keep food, drinks, cosmetics, etc. out of the lab entirely. Do not pipette by mouth.

6. Never store [human] food or beverag