Chapter 14

Environmental Hazards

& Human Health

What major health hazards do we face?

RISK - is the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage. (normally expressed in terms of probability)

Lung cancer kills 1 in 250 who smoke a pack per day.

RISK ASSESSMENT - is the process of using statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment.

RISK MANAGEMENT - involves deciding whether

or how to reduce a particular risk to a certain level and at what cost.

Different Hazards Include :

BIOLOGICAL HAZARDS - bacteria / viruses / parasites / protozoa / fungi...

CHEMICAL HAZARDS - harmful chemicals found in air / water / soil / food / human made products...

PHYSICAL HAZARDS - include fires / earthquakes / volcanic eruptions / floods / storms...

CULTURAL HAZARDS - include unsafe working conditions / unsafe highways / criminal assaults / poverty...

LIFESTYLE CHOICES - such as smoking / poor food choices / drinking too much alcohol / having unsafe sex...

What types of biological hazards do we face?

Danga

NONTRANSMISSIBLE DISEASE - is caused by something other than a living organism and does not spread from one person to another; they tend to develop slowly.

INFECTIOUS DISEASE - is caused when a pathogen such as a bacterium, virus or parasite invades the body and multiplies it's cells and tissues.

TRANSMISSIBLE DISEASE - (also called a contagious disease) is an infectious disease that can be transmitted from one person to another.

INFECTIOUS DISEASES ARE STILL MAJOR HEALTH THREATS

A growing problem is that many disease-carrying bacteria have developed genetic immunity to widely used antibiotics.

Diseases, especially in developing countries are spread through air, water, food, and body fluids like feces, urine, blood and droplets sprayed by sneezing and coughing.

PNEUMONIA AND FLU

HIV/AIDS TUBERCULOSIS

DIARRHEAL DISEASES

MALARIA HEPATITIS B

MEASLES

3.2 MILLION

2.0 MILLION

1.8 MILLION

1.6 MILLION

1 MILLION

1 MILLION

800,000

DEATHS PER YEAR

viruses :-evolve quickly -are not effected by antibiotics-can kill large numbers of

peopleBiggest killer = influenza or the flu virus;

transmitted by body fluids or airborne emissions of an infected person.

influenza pandemic of 1918 --->

MALARIA : Spread by certain mosquito species

Malaria killer at least 2,700 people per day. 90% who die are under the age of 5, and those who survive suffer brain damage or impaired learning ability.

It infects red blood cells, causing : -fever-chills-drenching sweats-anemia-severe abdominal pain-vomiting-extreme weakness-greater susceptibility to other diseases.

You can greatly reduce your chances of getting infectious disease by practicing good hygiene:

-washing hands thoroughly and frequently-avoid touching your face -stay away from people who have the flu or other viral diseases

Good News :

"According to WHO, the global death rate from infectious diseases decreased by more than 2/3 between 1970 and 2006 and is projected to continue dropping."

What types of chemical hazards do we face?

A chemical that can cause temporary or permanent harm or death to humans and

animals

Top 5 toxic substances according to the EPA:

• arsenic• lead• mercury• vinyl chloride (PVC plastics)• polychlorinated biphenyls (PBCs)

Toxic Chemicals

Chemicals, types of

radiation, or certain viruses that can cause

or promote cancer

(arsenic, choloroform,

formaldehyde, gamma radiation, x-

rays, etc.)

Carcinogens• In 2007 there were at least

12 million new cancer cases and 7.6 mission cancer deaths.

• time gap (10-40 years)

Chemicals or forms of radiation

that cause mutations in DNA

or that increase the frequency of such

changes

(nitrous acid - food preservative)

Mutagens

Chemicals that cause harm or birth defects to a fetus or embryo

Tetragens

(benzene, lead, mercury, PCBs

phthalates, formaldehyde,

cadmium, vinyl cholride)

How Are We Affected?

• Immune system weakened against bacteria, viruses, and protozoa

• Nervous system (brain, spinal cord, peripheral nerves) affected by nuerotoxins such as nethyl mercury, arsenic, and some pesticides o behavioral changeso learning disabilitieso ADDo paralysiso death

• Endocrine system (hormones) affected by chemicals shaped similarly to hormones that fit in their relative receptors, which messes with hormonal balance. these molecules are called hormonally active agents or hormone blockers (gender benders)o turn on and off bodily systems controling sexual reproduction,

growth, development, learning ability, and behavior

How can we evaluate chemical hazards?

• Toxicology: The study of harmful effects of chemicals on humans and other organisms

• Toxicity: A measure of the harmfulness of a substance (ability to cause illness)

• If you ingest a large amount of anything, it becomes toxic.

• Dose: the amount of harmful chemical that a person has ingested

Factors leading to hazardous chemical effects

• Genetic Makeup

• Age

• "Multiple Chemical Sensitivity"

• How well the body's detoxification organs function

• Chemical solubility

• Persistence

• Biological Magnification (Toxins increase as they pass through trophic levels)

Response to Chemicals

Damage to health resulting from exposure to chemicals is called response.

• Acute effects: Sudden

• Chronic effects: Long-lasting

Testing for Toxicity

• Lab animals and organisms

• 2-5 years, hundreds of animals and cost millions.

• Toxicity estimated on dose-response curve

• Dose=x-axis

• percentage killed=y-axis

Methods to replace animal testing

• Computer simulations

• Using tissue cultures of cells instead of actual animals

• Controversy behind animal testing is huge

Problems estimating toxicity

• It is difficult to determine what single substance is toxic in a compound of many substances

• Separating these harmful chemicals from others takes time and money

• Case reports provide info about people suffering illness after exposure to a chemical

• Can be inaccurate because all info is not known (dose size, etc)

Trace Levels of chemicals

• Trace levels of chemicals are in almost anything

• Not enough data to determine if harmful or not

Knowledge About Harmful Effects of Chemicals

• "Toxicologists know a great deal about a few chemicals, a little about many, and next to nothing about most"

• Only 10% of 100,000 registered chemicals have been tested for toxicity and only 2% have been ID'd as carcinogens, mutagens, or teratogens

• Because of insufficient data and high costs, the US government doesn't regulate 99.5% of chemicals

Protection from Chemicals

• Many scientists are currently pushing for pollution prevention, which means testing everything before releasing it.

• Precautionary Principle is when there is not enough data or research and reasonable doubt that the chemical is harmful, we shouldn't release it.

• Ethical responsibility

• Too expensive to produce any new products

• Controversy on how far we should take this

How do we perceive risks & how can we avoid the worst of them?

Risk Analysis

- Identifying hazards and evaluating their associated risks

- Statistical probabilities based on past experience, animal testing, and other tests are used to calculate risks

Risks Today- The biggest risk right now in the United States

is poverty.

- Smoking cigarettes is the world's most preventable cause of suffering and premature deaths today.

People do a poor job of risk evaluating

1. Fear effects the way people think of risks, and can make them overestimate the risks.

3. The degree of control we have also effects how we perceive risks.

2. We feel more impacted by a single catastrophic event than less significant but more total death events like the death toll from smoking every year.

Optimism Bias: the belief that risks that apply to other people do not apply to them.

- We take some risks for instant gratification. For example, eating bad foods and smoking.

Evaluate and Reduce Risks

- Compare risks: ask yourself "how risky is it compared to other risks?"

- Determine how much risk you are willing to accept: 1 in 100,000 chance of dying may be too risky, but 1 in 1,000,000 may not be.

Determine the actual risk involved: Most people believe the world is more risk filled than it

really is due to the media.

We face tons of infectious and hazardous diseases such as the flu, AIDS, tuberculosis and malaria. We are exposed to chemicals that can cause cancers and birth defects and disrupt the human immune, nervous, and endocrine systems.

Since we can't fully evaluate the harm caused by exposure to chemicals, many health scientists call for greater emphasis on pollution prevention.

- Being informed, thinking critically about risks, and making careful choices can reduce major risks.