Chapter 14, Risk and ToxicologyKnow the different types of hazardsUnderstand the role of diseaseKnow what toxicology is

Types of Hazards

Environmental health = assesses environmental factors that influence human health and quality of life◦ Including natural and human-caused factors

Physical hazards = occur naturally in our environment◦Earthquakes, volcanoes, fires, floods,

droughts◦We can’t prevent them, but we can prepare

for them◦We increase our vulnerability by deforesting

slopes (landslides), channelizing rivers (flooding), etc.

◦We can reduce risk with better environmental choices

Types of Hazards

Chemical hazards = synthetic chemicals such as pharmaceuticals, disinfectants, pesticides◦Harmful natural chemicals (e.g., venom)

also existBiological hazards = result from

ecological interactions◦Viruses, bacteria, and other pathogens◦Infectious disease = species parasitize

humans, fulfilling their ecological roles◦Vector = an organism that transfers a

pathogen to a host◦We can’t avoid risk, but we can reduce

infection

Types of Hazards

Cultural = result from where we live, our socioeconomic status, our occupation, our behavioral choices◦We can minimize some, but not all, of

these hazards◦Smoking, drug use, diet and nutrition,

crime, mode of transportation◦Health factors (e.g., living near toxic

waste) are often correlated with poverty

Radon = a highly toxic, radioactive gas that is colorless and undetectable ◦It can build up in basements

Asbestos = a mineral that insulates, muffles sounds, and resists fire

Indoor environmental health hazards

Indoor environmental health hazards

Lead poisoning = caused by leadDamages the brain, liver, kidney, and stomach

Causes learning problems, behavior abnormalities, and death

Exposure is from drinking water that flows through lead pipes or from lead paint

A recently recognized hazardPolybrominated diphenyl ethers

(PBDEs) = has fire-retardant properties◦Used in computers, televisions, plastics, and

furniture◦Persist and accumulate in living tissue◦Mimic hormones and affect thyroid

hormones◦Also affect brain and nervous system

development and may cause cancerConcentrations are rising in breast milk

◦Now banned in Europe, concentrations have decreased

◦The U.S. has not addressed the issue

Disease is a major focus of environmental health

Despite our technology, disease kills most of us

Disease has a genetic and environmental basis◦Cancer, heart

disease, respiratory disorders

◦Poverty and poor hygiene foster illnesses

Infectious diseases kill millions

Infectious diseases kill 15 million people/year◦Half of all deaths in developing

countriesMoney lets developed countries

have access to hygiene and medicine

Infectious and noninfectious diseases

Lifestyles in developed nations affect diseases◦U.S. smoking dropped 38%◦But obesity has doubled

Public health decreases some infectious diseases◦Some (AIDS) are

spreading ◦Some develop

resistance to antibiotics

Diseases, the environment, and society

• Our mobility spreads diseases - West Nile Virus spread

from Africa to all lower 48 U.S. states in 5 years

• New diseases are emerging- H5N1 avian flu, H1N1

swine flu• Climate change will expand the range

of diseases• To predict and prevent diseases, experts deal

with complicated interrelationships - In technology, land use, and ecology

The best way to reduce disease? Improve the basic living conditions of the

poor◦Food security, sanitation, clean drinking water

Expanded access to health care◦Health clinics, immunizations, pre- and

postnatal careEducation campaigns work in rich and poor

nations◦Public service and governments give advice◦Packaging and ads advise us on smoking, etc.◦Sex and reproductive health education slows

population growth and spread of HIV/AIDS

Disease

Toxicology studies poisonous substances

Toxicology = the study of the effects of poisonous substances on humans and other organisms

Toxicity = the degree of harm a toxicant can inflict

Toxicant = any toxic substance (poison)◦ “The dose makes the poison” = toxicity

depends on the combined effect of the chemical and its quantity

Environmental toxicology = deals with toxic substances that come from or are discharged into the environment◦Studies health effects on humans, other animals,

and ecosystems

Balancing risks and rewards

There is a tradeoff between the risk and reward of most hazards◦We must judge how these compare◦We use Bisphenol A despite its health risks◦Are safer and affordable alternatives available?

Don’t forget, chemicals have given us our high standard of living◦Food, medicine, conveniences

Toxic substances in the environment

The environment contains natural chemicals that may pose health risks

Toxins = toxic chemicals made in tissues of living organisms

But synthetic chemicals are also in our environment◦Every human carries traces of

industrial chemicals

The U.S. makes or imports 250 lb of chemicals for every person in the country

Chemicals are in the air, water, and soil

80% of U.S. streams contain 82 contaminants◦Antibiotics, detergents, drugs, steroids,

solvents, etc.92% of all aquifers contain 42 volatile

organic compounds (from gasoline, paints, plastics, etc.)◦Less than 2% violate federal health standards

for drinking water

Pesticides are present in streams and groundwater in levels high enough to affect aquatic life

Synthetic chemicals are in all of us

Every one of us carries traces of hundreds of industrial chemicals in our bodies◦Including toxic persistent organic

pollutants restricted by international treaties

Babies are born “pre-polluted” – 232 chemicals were in umbilical cords of babies tested

Not all synthetic chemicals pose health risks◦But very few of the 100,000 chemicals

on the market have been tested

Silent Spring began the debate over chemicals

Rachel Carson’s Silent Spring (1962) showed DDT’s risks to people, wildlife, and ecosystems

Chemical companies challenged the book◦Discrediting Carson’s personal reputation

DDT was banned in the U.S. in 1973◦But is still made in the U.S. and exported

In the 1960s, untested pesticides were sprayed over public areas, with assumption they would do no harm

Toxicants come in different types

Neurotoxins = assault the nervous systemAllergens = over stimulate the immune system

Toxins may concentrate in water

Runoff carries toxins from land to surface water

Chemicals in the soil can leach into groundwater◦Contaminating drinking water

Chemicals enter organisms through drinking or absorption◦Aquatic organisms (fish, frogs, etc.) are good

pollution indicatorsContaminants in streams and rivers enter

drinking water and the air

Routes of chemical transport

Airborne substances can travel widely

Chemicals can travel by air◦Their effects can occur far from the site of use

Pesticide drift = airborne transport of pesticides

Synthetic chemicals are found globally◦In arctic polar bears, Antarctic penguins, and

people in Greenland

Some toxicants persist

Toxins can degrade quickly and become harmless◦Or they may remain unaltered and persist for

decades◦Rates of degradation depend on the substance,

temperature, moisture, and sun exposureBreakdown products = simpler products

that toxicants degrade into◦May be more or less harmful than the original

substance◦DDT degrades into DDE, which is also highly

persistent and toxic

Toxicants can accumulate and biomagnify

Toxicants in the body can be excreted, degraded, or stored◦Fat-soluble toxicants are stored in fatty

tissuesBioaccumulation = toxicants build up

in animal tissuesBiomagnification = concentrations of

toxicants become magnified◦Near extinction of peregrine falcons and

bald eagles

Not all toxicants are synthetic

Toxic chemicals also exist naturally and in our food◦Don’t assume natural chemicals are all

healthy and synthetic ones are all harmfulSome scientists feel that natural

toxicants dwarf our intake of synthetic chemicals◦Natural defenses are effective against

syntheticsEnvironmentalists say synthetic

toxins:◦Are harder to metabolize and excrete◦Persist and accumulate◦Enter people in ways other than in food