Chapter 14, Risk and
Toxicology
Know the different types of hazards
Understand the role of disease
Know 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 exist

Biological 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
Indoor environmental health
hazards

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
Lead poisoning = caused by
lead
Damages 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
hazard

Polybrominated 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 cancer

Concentrations 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
countries

Money 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
Disease


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 care

Education 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
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
In the 1960s, untested
pesticides were sprayed
over public areas, with
assumption they would do
no harm
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
Toxicants come in different types


Neurotoxins = assault the nervous system
Allergens = 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 indicators

Contaminants 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 exposure

Breakdown 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
tissues
Bioaccumulation = toxicants build up
in animal tissues
 Biomagnification = 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 harmful

Some scientists feel that natural
toxicants dwarf our intake of synthetic
chemicals
◦ Natural defenses are effective against
synthetics

Environmentalists say synthetic
toxins:
◦ Are harder to metabolize and excrete
◦ Persist and accumulate
◦ Enter people in ways other than in food