Industrial Hygiene

An Introduction

For

Chemical Engineers

Goal of Industrial Hygiene

Worker safety and well-being Anticipation Recognition Evaluation Control

Workplace Hazards

Chemical Physical Ergonomic Biological

Chemical Hazards

Irritants Asphyxiants CNS Agents Specific organ agents Genetic activity

Acute versus Chronic

Irritants

Respiratory Skin Eye

Irritants

Primary/Secondary Primary – at source of contact Secondary – travels through blood to another

area Reversible/Irreversible Sensitization

Irritant that has a delayed reaction on subsequent exposure

Asphyxiants

Simple Asphyxiants N2

CO2

He CH4

Dilute air so oxygen content is low

Chemical Asphyxiants CO HCN H2S

Interact at cellular level to inhibit oxygen uptake.

Central Nervous System Depressants

Narcotics Anesthetics Depressants

CNS Depressants

Aliphatic Hydrocarbons Increased chain length enhances effect Addition of an alcohol group (i.e. ethanol) Addition of a halide group enhances the effect

Specific Organ Attack

May be reversible or irreversible Blood - Hemotoxic Liver – Hepatotoxic Lungs – Pulmonotoxic Kidneys – Nephrotoxic Skin – Dermatotoxic Nerves & Brain - Neurotoxic

Genetic Activity

Typically is irreversible Causes cancer – Carcinogen Causes chromosome damage – Mutagen Causes birth defects – Teratogen Causes damage to reproductive system -

Reproductive Hazard

Anticipation of Chemical Hazards

Consider the following: Raw materials Intermediates formed Final products Disposal of used products Maintenance materials

“Cradle to Grave” thought process

Anticipation of Chemical Hazards

Occupational Safety and Health Administration (OSHA) has established Permissible Exposure limits They are defined in time weighted average, TWA, for

most working conditions. Short Term Exposure Limits, STEL, for 15 minute exposure. Ceiling, C, for maximum allowable concentration.

American Council of Government Industrial Hygienists (ACGIH) has established Threshold Limit Values, TLV.

Anticipation of Chemical Hazards

Material Safety Data Sheets, MSDS

Recognition of Chemical Hazards

Odors Not all agents have detectable odor

Frequent headaches Dermatitis Drowsiness Personality changes Clusters of problems

Workplace Hazards

Chemical

Physical Ergonomic Biological

Physical Hazards

Dusts and Fibers Noise Corrosives Temperature Extremes Ionizing Radiation Non-Ionizing Radiation

Dusts and Fibers

Concerned about particle size and penetration into pulmonary track D > 0.5 micron – does not reach lungs (but may

ingest) 0.2 < D < 0.5 micron – respirable and gets stuck

in lungs D < 0.2 micron – are exhaled

Noise Hazard Recognition

Need to shout Ringing sensation Degraded hearing after work Auditory testing

Noise Hazard

Sound level measurement L = 10 * Log (I/I0)2

L = Sound intensity, decibels (dB)

P = Sound pressure, rms (Pa)

I0 = Reference sound pressure, rms (20 Pa)

Typical Noise Sources

Source Sound Level (dB)Rocket 195Jet Engine 160Rock Band 115Power Lawn Mower 95Factory 90Noisy Office 80Conversation 65Quite Room 40Whisper 20

OSHA Sound Level PEL’s

Sound Level (dB) Exposure Time Limit (hr)< 90 No Limit 90 8 95 4 100 2 105 1 110 ½ 115 ¼> 115 0

Noise Control

Enclose equipment Enclose operator Slower rotational speed Intake/Exhaust mufflers Padded mountings

Corrosive Hazards

Usually concerned with the affect of corrosives on process equipment

Concern for contact of workers with corrosives Usually involves necrosis, the death of local

tissue due to contact of agent

Temperature Extremes

Heat Stress Heat Stroke Heat Exhaustion

Cold Stress Frostbite Hypothermia

Heat Stress

Body’s Energy Balance Metabolic rate Radiation Convection Sweating

External Conditions Temperature Humidity Air movement Radiation

In a typical healthy individual the internal core bodytemperature may rise as much as 3°C during heat stress

Cold Stress

Less Common in Industrial Situations Cold climates Refrigerated space Wind chill

Responses to Cold Stress Body core temperature is typically 37°C Shivering when body Tc < 36°C

Lose Consciousness at Tc < 34°C

Temperature Stress Control

Hot Stress Air movement Periodic rest Remove to cooler

location

Cold Stress Limit exposure time Protective clothing

Ionizing Radiation

Physical damage to cells Possible genetic damage Types of Radiation

Alpha – emitted from nuclei of radioactive particles Beta – similar to but with more penetrating (~ 1 cm) X-ray – produced from high speed electrons striking

material Gamma – originates from nucleus, produces burns Neutrons – emitted from disintegration of isotopes, very

penetrating

Common Units to Measure Radiation

Rad – the unit of absorbed dose of ionizing radiation equal to the absorption of 100 ergs/g

Roentgen – exposure to x-rays or gamma rays equal to absorption in 1 cm3 of air to produce 1 electrostatic unit of charge

Rem – the dosage of ionizing radiation that will cause the same biological effect as 1 rad of x-, gamma or beta

Curie – the rate at which radioactive material emits particles, 3.7x1010 disintegrations per second

Protection from Ionizing Radiation

Alpha, Beta - Little protection required

X-ray, Gamma - Extensive high density shielding

Neutrons - Special shieldingtechniques

Non-Ionizing Radiation

Low frequency - ~ 3 m wavelength

Microwaves - 3 m to 3 mm

Infrared - 3 mm to 750 nm

Visible light - 750 nm to 400 nm

Non-Ionizing Radiation

Ultraviolet Radiation UV-A 400 to 320 nm

Harmful only to eyes, causes sun tan

UV-B 320 to 280 nmCauses skin damage (sun burn), source arc welding

UV-C 280 to 220 nmSevere damage, source germicidal lamps

Laser Light

Especially dangerous for eyes Retinal burns Corneal burns

Workplace Hazards

Chemical Physical

Ergonomic Biological

Ergonomic Hazards

Physiological Hazards Awkward movements Muscle strain

Psychological Hazards Boredom Concentrated attention Simulated inputs

Ergonomic Hazards

Increasing emphasis due to repetitive nature of some industrial manufacturing jobs.

Also with more operators working at computers or workstations there are ergonomic concerns.

Workplace Hazards

Chemical Physical Ergonomic

Biological

Biological Hazards

Pathogenic organisms Five levels of classification

1 least dangerous 5 most dangerous

Pathogenic organisms are typically not found in a chemical processing facility

Possible biological hazards in an industrial setting AIDS Hepatitis B

Biological Hazards

Industries with possible biological hazards Pharmaceutical Manufacturing Food processing or agricultural products

Typically hazards are well contained

Chemical Engineer’s Responsibility

Be aware of industrial hazards and possible effects.

Design inherently safer systems that minimize worker exposure to hazards.

As a manager encourage proper safety procedures and good housekeeping to minimize employees exposure to hazardous situations.