Chapter 15

Environmental Health, Risk, Pollution and Toxicology

Risks and Hazards

• risk expressed as a probability;

• risk assessment using data, hypotheses and models to estimate the probability of harm to human health, society, or the environment that may result from exposure to specific hazards

Risk: possibility of suffering harm from a hazard that can cause injury, disease, economic loss or environmental damage.

Risk Analysis

Risk analysis involves:

• identifying hazards

• evaluating associate risks (risk assessment)

• ranking risks (comparative risk analysis)

• determining options (risk management)

• informing decision makers and the public (risk communication)

What are the greatest risks to humans in the US?

• Please create a list with your table.

• Please rank the risks as best you can.

Risk Analysis• What are the greatest risks to humans in the U.S.?• poverty poses the greatest risk (shortens lifespan by 7–10

years);• smoking and being overweight pose the next greatest risk

(each shortens lifespan by 6 years);• being born male poses a greater risk than being female

(shortens lifespan by 7.5 years);• being unmarried is associated with risk (shortens lifespan by

5 years);• other significant risks in the U.S. include second-hand

smoke, driving, air pollution, alcohol use and drug abuse

Risk AnalysisWhat are the limitations of risk assessment?• inaccuracy of models;• inadequate data;• bias because of who does the analyses;Major questions?• Which risks are worth evaluating?• How reliable are analyses?• How much risk is acceptable?• How much will it cost to reduce each risk?• How can a risk management plan be communicated?

Major Hazards

There are four major types of hazards:• cultural hazards, such as unsafe working conditions,

smoking, poor diet, drugs, drinking, driving, criminal assault, unsafe sex and poverty;

• chemical hazards from harmful chemicals in air, water, soil and food;

• physical hazards, such as noise, fire, tornadoes, hurricanes, earthquakes, volcanic eruptions, floods and ionizing radiation;

• biological hazards from pathogens, pollen and other allergens and animals, such as bees and poisonous snakes

Causes of DeathTobacco use is the leading cause of preventable death (data from 1993.

•© Brooks/Cole Publishing Company / ITP

Risk Assessment

• 4 steps1. Identification of the hazard

2. Dose-Response assessment

3. Exposure assessment

4. Risk characterization

ToxicologyToxicology is the study of the adverse effects of chemicals on

health. • toxicity is a measure of how harmful a substance is;• the amount of a potentially harmful substance that is

ingested, inhaled, or absorbed through the skin is called the dose;

• the resulting type and amount of damage to health are called the response;

• • two types of responses:– acute effect: immediate or rapid harmful reaction, e.g., dizziness,

rash, death;– chronic effect: permanent or long–lasting consequence, e.g., asthma,

kidney damage, heart

Bioaccumulation & BiomagnificationThe pesticide DDT becomes increasingly concentrated high in the food chain because it is stored in fatty tissue and not easily broken down or excreted

Bioaccumulationresults when theconcentration of achemical in specificorgans or tissues ishigher than wouldnormally be expected.

Biomagnificationinvolves magnificationof concentrations asthey pass through thefood chains and webs.

Pollution

Pollution: introduces harmful materials or produces harmful conditions to the environment

Introduced Through:

a) Point Sources:

b) Area Sources:

c) Mobile Sources:

Measuring Pollutants

• Measuring depends on the substance

• Common Units– ppm: Parts per million– ppb: Parts per billion– Micrograms per cubicle meter (measures air)

Categories of Pollutants• Infectious Agents• Toxic Heavy Metals Organic Compounds • Radiation• Thermal Pollution• Particulates• Asbestos• Electromagnetic Fields• Noise Pollution• Voluntary Exposure

Toxic Heavy Metals

• Travel through toxic pathways

• Biomagnifications: the accumulation or increase in concentration of a substance in living tissue as it moves through a food web.

Organic Compounds

• Organic Compounds: composed of carbon, making up living tissue

• Synthetic Organic Compounds: used in industrial processes

• Persistent Organic Pollutants: Synthetic organic compounds often containing chlorine, that do not easily break down in the environment.

• Hormonally Active Agents: Chemicals in the environment able to cause reproductive and developmental abnormalities in animals

General Effects of Pollutants

• Changes in Abundance

• Changes in Distribution

• Changes in Birth Rates

• Changes in Death Rates

• Changes in Growth Rates

Ecological Gradients• Changes in vegetation with distance from a toxic

source

Tolerance: The ability to resist or withstand stress resulting from exposure to a pollutant or harmful condition- Behavior vs. Physiological

Acute and Chronic Effects

Determining Toxicity

Three methods of determining toxicity:1. case reports (usually to physicians) about health effects

after exposure to a chemical;2. epidemiology, involving studies of populations exposed to

certain chemicals or diseases3. laboratory investigations (usually with test animals);

1. LD 50 - is the median lethal dose, the amount of a chemical received that kills 50% of animals;

2. a poison is legally defined as a chemical that has an LD 50 of 50 milligrams or less per kilogram of body weight.

3. You may also see ED-50 and TD-50

Dose–Response Curves

The left dose–response curve shows increasing harmful effects with dose, And no dose is considered safe.

The right example has a threshold, such that low doses are considered safe. •© Brooks/Cole Publishing Company / ITP

•Dose–response curves show the adverse effects of various doses of a toxic agent on a test population by plotting harmful effect as a function of dose.

Concept of Dose and Response• The effect of a certain chemical on an individual

depends on the dose.• Individuals differ in their response to chemicals

Threshold Effects: - the level below which effects are not observable and above which effects become apparent

Chemical HazardsWhat are toxic vs. hazardous chemicals?• toxic chemicals are generally defined as substances that

are fatal to over 50% of test animals (LD50) at given concentrations.

• hazardous chemicals cause harm by– being flammable or explosive (e.g., gasoline);– irritating or damaging the skin or lungs (e.g., strong acids or

alkalines such as oven cleaners);– interfering with or preventing oxygen uptake and distribution (e.g.,

carbon monoxide, CO);– inducing allergic reactions of the immune system (allergens).

Mutagens, Teratogens, and Carcinogens

• mutagens are agents, chemicals and radiation, that cause random mutations, or changes in the DNA;

• teratogens are agents (chemicals, radiation, or viruses) that cause birth defects;– e.g., PCBs, steroid hormones, heavy metals;

• carcinogens are agents (chemicals, radiation, or viruses) that cause cancer;– over 100 types of cancer (depending on cells involved);– e.g., cigarette smoke.

Each type of hormonehas a unique shape thatallows it to attach tospecial receptors ofcells. Hormone mimics,such as estrogen-likechemicals, attach toreceptors and disruptnormal activity (upperright). Hormone blockersprevent hormones suchas androgen fromattaching to receptors(lower). Examples includedioxin and PCBs. © Brooks/Cole Publishing Company / ITP

Hormone Disruptors

Physical Hazards

Earthquakes are among various types of natural physical hazards. Other physical hazards include volcanoes and ionizing radiation.

© Brooks/Cole Publishing Company / ITP

Physical HazardsIonizing radiation, a form of electromagnetic radiation, has enough energy to damage body tissues.

• examples include X rays and ultraviolet radiation, and various types of radiation emitted by radioactive isotopes; no safe dosage

© Brooks/Cole Publishing Company / ITP

Physical Hazards

• background sources include about 82% of the exposure;

• human–caused exposure include medical X rays (10%), nuclear medicine (4%), and consumer products (3%);

• harmful effects include burns, miscarriages, eye cataracts and certain cancers;

Each year people are exposed to some radiation from natural or background sources, as well as from human–caused exposure.

Biological Hazards

• Non-transmissible diseases are not passed from one person to another, e.g., cardiovascular disorders, most cancers, diabetes, emphysema and malnutrition;

• transmissible diseases are caused by bacteria, viruses, protozoa, or parasites, and can be passed from one person to another, e.g., colds, flus, hepatitis, sexually- transmitted diseases, malaria;

• some transmissible diseases are spreading over broad geographic areas as the result of human activity;– e.g., Lyme disease carried by ticks and spread by people is now

widespread over North America.

Biological hazards include both non-transmissible and transmissible diseases.

Biological Hazards

• reduce overcrowding, unsafe drinking water, poor sanitation, inadequate health care systems, malnutrition and poverty;

• increase funding for disease monitoring;• sharply reduce antibiotic use to prevent evolution

of resistant organisms;• protect biodiversity as a means of reducing disease

spread;• increase research.

What are some ways we can reduce infectious diseases?

Additional Terminology

Contamination: making something unfit for a particular use through the introduction of desirable material

Synergism: the interaction of different substances resulting in a total effect greater than the sum of the effects of the separate sources

Precautionary Principle

• The idea that in spite of the fact that full scientific certainty is often not available to prove cause and effect, we should still take cost-effective precautions to solve environmental problems where there exists a threat of potentially serious and/ or irreversible environmental damage