Central Case Study: Poison in the Bottle: Is Bisphenol A ... · Cells grow uncontrollably, damaging the body Prevalence of environmentally induced cancer has been underestimated Hard

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© 2014 Pearson Education, Inc.

Lecture Outlines

Chapter 14

Environmental Health

and Toxicology

Withgott/Laposata

Fifth Edition


Central Case Study: Poison in the Bottle: Is

Bisphenol A (BPA) Safe?

BPA is linked to cancer, nerve damage, and miscarriages

In extremely low doses

Used to make hard plastic found in hundreds of products

Cans, utensils, baby bottles, laptops, toys

BPA leaches into food, water, air, and bodies

93% of Americans have it in their bodies

Negative effects occur at extremely low doses

BPA mimics estrogen, a female hormone

In lower levels than set by regulatory agencies

© 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc.

Central Case Study: Poison in the Bottle: Is

Bisphenol A (BPA) Safe?

Numerous scientific panels have examined the health risk of BPA

Some have found no concern (U.S. FDA in 2008)

Other have found reason for concern (U.S. FDA’s science advisory panel in 2009)

Numerous countries had banned the use of BPA in baby bottles by 2011

Public and scientific opinion wanted BPA regulated in the United States

In 2012, the FDA rejected a proposed ban on its use

Other countries have banned BPA for some uses

Some industries are removing BPA on their own


Environmental Health

Environmental health = field that assesses

environmental factors that influence human health

and quality of life

Including natural and human-caused factors

Practitioners seek to prevent adverse effects on

human health and ecological systems

Many environmental health hazards exist in the

world around us


We face four types of environmental hazards

Physical hazards = hazards that occur naturally in

our environment

Exposure to ultraviolet (UV) radiation from sunlight

Earthquakes, volcanoes, fires, floods, droughts

We can’t prevent them, but we can prepare for them

We increase our vulnerability by deforesting slopes

(e.g., landslides), channelizing rivers (e.g., flooding),

etc.

We can reduce risk with better environmental choices

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Chemical hazards = synthetic chemicals such as

pharmaceuticals, disinfectants, pesticides

Harmful natural chemicals (e.g., venom) also exist

and chemicals that we take from nature and process



Biological hazards = result from ecological

interactions

Viruses, bacteria, and other pathogens

Infectious disease = disease occurring when species

parasitize humans, fulfilling their ecological roles

Vector = an organism that transfers a pathogen

We can’t avoid risk, but we can reduce infection



Cultural hazards = result from where we live, our

socioeconomic status, our occupation, our

behavioral choices

Smoking, drug use, diet and nutrition, crime, mode of

transportation—some we control, others we can not

Health factors (e.g., living near toxic waste) are often

correlated with poverty


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 have

some genetic basis

Air pollution, poverty, and poor hygiene foster

illnesses

Noninfectious diseases cause over half of the

world’s deaths

Infectious diseases account for 1 in 4 deaths

15 million people/year



health

Where you live helps determine your disease

Infectious disease causes half of all deaths in

developing countries

Money lets developed countries have access to

hygiene and medicine to combat these diseases

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health

Lifestyles in developed nations affect diseases

U.S. smoking dropped 42%

But obesity has more than doubled

Public health efforts decrease some infectious

diseases

But some (AIDS) are spreading

Some develop resistance to antibiotics



Social and environmental factors can influence

the spread of infectious disease

Our mobility spreads diseases worldwide

Severe acute respiratory syndrome (SARS) in 2003

H1N1 swine flu in 2009–2010

Climate change will expand the range of diseases

New disease threats may arise

Some pathogens evolve rapidly

Humans can alter existing diseases to make them more

deadly—bioterrorism is a growing concern

To predict and prevent diseases, experts deal with

complicated interrelationships between technology, land

use, and ecology © 2014 Pearson Education, Inc.


We are fighting disease with diverse

approaches

One of the best way to reduce disease is to improve

the basic living conditions of the poor

Food security, sanitation, clean drinking water

Also, provide expanded access to health care

Health clinics, immunizations, pre- and postnatal care


We are fighting disease with diverse

approaches

Education campaigns work in rich and poor nations

Agencies, organizations, and governments work

together

The United Nations, the World Health Organization,

U.S. Agency for International Development, etc.

Private organizations donate millions of dollars

The Bill and Melinda Gates Foundation has donated

over $15 billion to global health programs since 1994

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Toxicology is the study of chemical hazards

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


Toxicology is the study of chemical hazards

We have been adding increased amounts and

numbers of chemicals into the environment

around us

Environmental toxicology = deals with toxic

substances that come from or are discharged into

the environment

Studies health effects on humans, other animals, and

ecosystems


Many environmental health hazards exist

indoors

Americans spend roughly 90% of their lives indoors

Indoor spaces can be rife with hazards

Radon = a highly toxic, radioactive gas that is colorless

and undetectable

Can build up in basements

Found in areas with certain types of bedrock

Asbestos = a mineral that insulates, muffles sounds, and

resists fire

Asbestosis = disorder that occurs when inhaled crystals of

asbestos cause scarred lungs that cease to function

Can lead to lung cancer



indoors

Lead poisoning = caused by lead, a heavy metal

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

Efforts in the United States have led to declines in

poisoning, but China still used lead paint in toys until

recently

In 2012, the Centers for Disease Control (CDC) cut the

danger threshold for lead in children’s blood from 10 to 5

micrograms/deciliter

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indoors

Polybrominated diphenyl ethers (PBDEs) = a group of chemicals with 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 that they’re banned in Europe, concentrations have decreased

The United States has not addressed the issue © 2014 Pearson Education, Inc.

Risks must be balanced against rewards

As with most hazards, there is a tradeoff between

the risk of harm and reward

We must judge how these compare

We use bisphenol A despite its health risks

Are safer and affordable alternatives available?

Chemicals have given us our high standard of living

Food, medicine, conveniences


Toxic Substances and Their Effects on

Organisms

The environment contains natural chemicals that

may pose health risks

Toxins = toxic chemicals made in tissues of living

organisms

Chemicals plants use to defend themselves

But synthetic chemicals are also in our environment

Many thousands of different chemicals have been

manufactured

The United States makes or imports 113 kg (250 lb) of

chemicals for every person in the country each year



Synthetic chemicals are all around

us—and in us

A 2002 study found that 80% of U.S. streams

contain 82 contaminants

Antibiotics, detergents, drugs, steroids, solvents, etc.

A 2006 study of groundwater found 18% of wells and

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 not high enough to affect human health

But high enough to affect aquatic life © 2014 Pearson Education, Inc.

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Synthetic chemicals are in all of our bodies

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

Nine out of 10 umbilical cords contained BPA

Not all synthetic chemicals pose health risks

But very few of the 100,000 chemicals on the market

have been thoroughly tested


Silent Spring began the public debate over

synthetic chemicals

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

Gathered and presented scientific studies, medical cases, and other data

Chemical companies challenged the book

Attacked Carson’s science and personal reputation

DDT was banned in the United States in 1973

But is still made in the United States and exported

Used to control disease vectors in developing countries (reward is greater than risk)

New technologies may stop disease without DDT


Not all toxicants are synthetic, and not all

synthetic chemicals are toxic

Toxic chemicals also exist naturally and in our food

It would be a mistake to assume natural chemicals

are all healthy and synthetic ones are all harmful

Plants produce toxic chemicals to defend

themselves

Most crop plants have had the level of toxic chemicals

reduced by artificial selection, but not eliminated

Eating animals may expose us to the plant chemicals

they ate


Toxic substances come in different types

Carcinogens = substances that cause cancer

Cells grow uncontrollably, damaging the body

Prevalence of environmentally induced cancer has been underestimated

Hard to identify because of the long time between exposure and onset of cancer and because not everyone exposed gets cancer

Mutagens = substances that cause DNA mutations

Most mutations have no effect, but some can cause cancer

If they occur in sperm or eggs, can impact offspring



Teratogens = chemicals that cause birth defects in

embryos

Thalidomide caused birth defects in the 1960s

Neurotoxins = toxicants that assault the nervous

system

Animal venoms, heavy metals, pesticides, and

chemical weapons



Allergens = toxicants that overactivate the immune

system

Cause an immune response when one is not needed

Increase in asthma in recent years may be due to

increased prevalence of allergenic chemicals

Not universally considered toxicants since they only

affect some people and not others

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Pathway inhibitors = toxicants that interrupt vital

biochemical processes by blocking one or more

steps in pathway

The herbicide atrazine blocks steps in photosynthesis

Endocrine disruptors = toxicants that affect the

endocrine (hormone) system = chemical messenger

system



Hormones stimulate growth, development, sexual

maturity

Work with extremely small concentrations

Synthetic chemicals interfere with normal signals

Block hormones, preventing signals from working

Mimic hormones, causing a change

Many mimic female sex hormones


Organisms have natural defenses against toxic

substances

Organisms were exposed to toxic substances before humans

starting producing them

Heavy metals occur naturally; plants and animals produce toxic

chemicals

Exposure has driven selection for organisms that can tolerate

these toxins

Barriers (skin, scales, feathers) prevent uptake

Biochemical pathways break down toxicants or are changed for

easier excretion

Some toxicants can not be broken down and are instead

stored in fatty tissue (DDT)

Defenses only work at low levels of toxicants


Individuals vary in their responses to hazards

Different people respond differently to hazards

Affected by genetics, surroundings, etc.

People in poor health are more sensitive

Sensitivity also varies with sex, age, and weight

Fetuses, infants, and young children are more

sensitive


Individuals vary in their responses to hazards

The Environmental Protection Agency (EPA) sets

standards for responses based on adult responses

Extrapolate adult responses to smaller size for

children, infants

Scientists argue that standards are not low enough to

protect babies

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The type of exposure affects the response

Acute exposure = high exposure to a hazard for short periods of time

Easy to recognize

Stems from discrete events: ingestion, oil spills, nuclear accident, etc.

Chronic exposure = low exposure for long periods of time

More common but harder to detect and diagnose

Affects organs gradually: lung cancer, liver damage

Cause and effect may not be easily apparent due to

time between onset of exposure and symptoms


Toxic Substances and Their Effects on

Ecosystems

Toxicants concentrated in the environment can harm

the health of many individuals of a species

Population size decreases

If the species is a predator, their prey may see

population growth

If the species is prey, its predator population may

suffer

Cascading impacts can cause changes in the

composition of biological communities

Can threaten ecosystem functioning


Airborne substances can travel widely

Chemicals can travel by air

Their effects can occur far from the site of use

Synthetic chemicals are found globally

Pristine lakes in the Canadian wilderness are

contaminated with industrial toxicants


Airborne substances can travel widely

Because of global air patterns, the poles are

particularly contaminated with industrial toxicants

Found in tissues of Arctic polar bears, Antarctic

penguins, and people in Greenland

Effects can occur over shorter distances

Pesticide drift is the airborne transport of pesticides to

land near agricultural fields


Toxic substances may concentrate in water

Toxic substances are not evenly distributed in the

environment

Move in specific ways

Runoff carries toxins from land to surface water

Chemicals in the soil can leach into groundwater,

contaminating drinking water

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Toxic substances may concentrate in water

Chemicals enter organisms through drinking or

absorption

Aquatic organisms (fish, frogs, etc.) are good pollution

indicators, giving early warnings of contamination

Contaminants in streams and rivers enter drinking

water and travel through the air



Some toxicants persist in the environment

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

Many persistent chemicals are designed to last in

the environment (paints, plastics)


Some toxicants persist in the environment

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 may accumulate and move up the

food chain

Toxicants in the body can be excreted, degraded, or

stored

Fat-soluble toxicants are stored in fatty tissues

Bioaccumulation = process of toxicants building up

in animal tissues to greater concentration than in the

environment


Toxicants may accumulate and move up the

food chain

Biomagnification = process that occurs when

concentrations of toxicants become magnified in

higher levels of the food chain

Each individual consumes multiple individuals from

lower trophic levels, getting the toxicants from each

Caused the near extinction of peregrine falcons and

bald eagles from the 1950s to 1970s

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Toxic substances can threaten ecosystem

services

Toxicants can alter the composition of ecosystems

and species interactions

Can threaten ecosystem services

Pesticide exposure has been implicated in in

declines of honeybee populations

Honeybees pollinate over 100 economically important

crops

Decomposers and detritivores break down organic

matter and improve soil

Pesticides and antifungal agents may disrupt nutrient

cycling


Wildlife studies integrate work in the field and

lab

Wild animals can serve as an early warning system

for human health threats of toxicants in the

environment

Museum collections provide data from times before

synthetic chemicals were used

Can be used to assess changes seen today

Measurements from animals in the wild can be

compared to controlled experiments in the lab

Work on alligators and frogs shows reproductive

abnormalities due to endocrine disruption from

pesticides and the herbicide atrazine © 2014 Pearson Education, Inc.


Human studies rely on case histories,

epidemiology, and animal testing

Case histories = studies of individual patients; e.g.,

autopsies tell us about lethal doses

Don’t tell about rare, new, or low-concentration toxins

Don’t tell about probability and risk

Epidemiological studies = large-scale comparisons

between exposed and unexposed groups

Can last for years

Yield accurate predictions about risk

Measure an association between a health hazard and an

effect—but not necessarily the cause of the effect


Human studies rely on case histories,

epidemiology, and animal testing

Since epidemiological studies can not establish causation, manipulative experiments are needed

Animals are used as test subjects

Mammals share evolutionary history

Substances that harm rats and mice probably harm us

Some people object to animal tests

Medical advances would be far more difficult without them

New techniques may replace some live-animal testing

Human cell cultures, bacteria, etc.

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Dose-response analysis is a mainstay of

toxicology

Dose-response analysis = testing method that

measures the effect a toxicant produces or the number

of animals affected at different doses

Dose = amount of substance the test animal receives

Response = the type or magnitude of negative effects

Dose-response curve = the dose plotted against the

response

LD50/ED50 = the amount of toxicant required to kill (lethal

dose) or show symptoms in (effective dose) 50% of the

test subjects

A high number indicates low toxicity


Dose-response analysis is a mainstay of

toxicology

Threshold dose = the level of toxicant where certain

responses start to occur

Organs can metabolize or excrete low doses of a

toxicant; DNA damage can be repaired slowly

Sometimes a response decreases as a dose increases

U- or J-shaped or inverted-U curves

Counterintuitive curves occur with endocrine disruptors

The hormone system is geared to respond to minute

concentrations (e.g., hormones)

Scientists give large doses in animal studies and

extrapolate downward to estimate the effect on humans


Mixes may be more than the sum of their parts

Determining the impact of mixed hazards is difficult

They may act in ways that cannot be predicted from the

effects of each in isolation

Mixed toxicants can sum, cancel out, or multiply each

other’s effects

New types of impacts may result from mixtures

Synergistic effects = interactive impacts that are greater

than the sum of their constituent effects

New impacts may arise from mixing toxicants

DDE may cause or inhibit sex reversal, depending on the

presence of other chemicals

The interactive effects of most chemicals are unknown

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Endocrine disruption pose challenges for

toxicology

Unconventional dose-response curves are hard to study or use to set safety standards for toxic substances

Theo Colburn’s Our Stolen Future (1996) describes how

synthetic chemicals may be altering hormones

Thousands of studies linked endocrine disruptors to

effects on reproduction, development, immune functions,

nervous systems, etc.

Evidence is strongest in non-human animals

Evidence in humans is growing

Uncertainty in studying endocrine disruptors exists

Negative findings pose economic threats to manufacturers


We express risk in terms of probability

Exposure to health threats doesn’t automatically

produce an effect

Rather, it causes some probability (likelihood) of harm

A substance’s threat depends on its identity and

strength, the chance and frequency of an encounter,

and an organism’s exposure and sensitivity to the

threat

Probability = description of the likelihood of a certain

outcome

Risk = the probability that some harmful outcome

will result from a given action, event, or substance


Our perceptions of risk may not match reality

Every action involves some element of risk

We try to behave in ways that minimize risk, but

perception may not match reality

People worry about negligibly small risks while engaging

in high-risk activities

Flying is perceived as riskier than driving

The chance of dying from an automobile accident is 73

times higher than in an airplane crash

We feel more at risk when we do not control a situation

We fear nuclear power and toxic waste

But not smoking or overeating



Risk assessment analyzes risk quantitatively

Risk assessment = the quantitative measurement of risk

Compares risks involved in different activities or

substances

Identifies and outlines problems



Risk assessment has several steps. If assessing a chemical

substance:

Conduct a scientific study of toxicity

Assess an individual or population’s exposure to the

substance (frequency, concentrations, length)

Teams of scientific experts review hundreds of studies

Regulators and the public benefit from informed

summaries

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Endocrine disruptors pose regulatory problems in

relation to their risk assessment

Scientific panels were convened to review research on

BPA

A government panel initially found that BPA posed an

intermediate health risk

Panel used mix of research with 70% coming from

academic laboratories

Industry protested that academic labs did not use the

correct lab procedures

Panel removed many academic studies and found no

evidence of health impact © 2014 Pearson Education, Inc.

Risk management combines science and other

socil factors

Risk management = decisions and strategies to

minimize risk; encorporates results of risk assessment

Federal agencies manage risk

The United States has the Centers for Disease Control

and Prevention (CDC), the EPA, the FDA

Scientific assessments are considered with economic,

social, and political needs and values

Comparing costs and benefits is hard

Benefits are economic and easy to calculate

Health risks (costs) are hard-to-measure probabilities of a

few people suffering and lots of people not


Two approaches exist for determining safety

We can not know a substance’s toxicity until it is tested

Two philosophies exist about determining safety

The “innocent-until-proven-guilty” approach assumes a

substance is harmless until shown to be harmful

Helps technological innovation and economic

advancement by limiting initial testing

But allows dangerous substances to be used

The precautionary principle approach assumes a substance

is harmful until it is shown to be harmless

Identifies troublesome toxicants before being released

May impede the pace of technology and economic

advance


Philosophical approaches are reflected in

policy

Different nations use different policies for regulating synthetic substances

Europe incorporates the precautionary principle

The United States uses the innocent-until-proven-guilty approach

But for some uses the precautionary principle is used

Federal agencies involved in tracking and regulating synthetic chemicals include:

The FDA: monitors food, food additives, cosmetics, drugs,

medical devices

The EPA: regulates pesticides and chemicals not covered

by other laws

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EPA regulation is only partly effective

The Toxic Substances Control Act (1976) directs the

EPA to monitor thousands of chemicals made in or

imported into the United States

The EPA can ban substances that pose excessive risk

Many health advocates think the TSCA is too weak

Of 83,000 chemicals, only five have been restricted

To push for more testing, toxicity must already be proven,

but the EPA can not do testing to show this

Only 10% of chemicals have been tested for toxicity

Fewer than 1% are regulated

Almost none have been tested for endocrine, nervous, or

immune system damage


EPA regulation is only partly effective

The Federal Insecticide, Fungicide, and Rodenticide Act

(FIFRA) charges the EPA with “registering” new

pesticides manufacturers want to market

The EPA asks the manufacturer to provide information

on safety assessments

The EPA examines ingredients, use, etc. to determine

risks to people, other organisms, water, or air

It approves, denies, or sets limits on the chemical’s sale

and use and approves language used on the label

Hazardous chemicals can be approved if economic

benefits outweigh hazards


Toxicants are regulated internationally

The EU’s REACH program (Registration, Evaluation,

Authorization, and Restriction of Chemicals) shifts the burden

of proof for safety to industry

Precautionary principle

Chemicals produced in amounts over 1 metric ton must be

registered

Helps industries research and develop safer products

Chemicals will be approved, deemed unsafe, or tested

further

Estimated that 30,000 substances will be registered

REACH will cost industry $3.8–7 billion over 11 years

Health benefits will be $67 billion over 30 years



Toxicants are regulated internationally

The Stockholm Convention on Persistent Organic

Pollutants (POPs) was enacted in 2004 and ratified

by over 150 nations

POPs = toxic, persistent chemicals that

bioaccumulate and biomagnify and can travel long

distances

The Stockholm Convention sets guidelines for

phasing out the “dirty dozen” = the 12 most

dangerous POPs

Encouraging transition to safer alternatives


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Conclusion

International agreements show that governments are

working to protect society, wildlife, and ecosystems from

toxic chemicals and environmental hazards

But solutions need more than government regulations

Consumer choice affects industries

Once scientific results are in, society’s approach to risk

management determines what policies are enacted

A safe and happy future depends on knowing the risks

some hazards pose and then replacing those substances

with safer ones

Documents

Central Case Study: Poison in the Bottle: Is Bisphenol A ... · Cells grow uncontrollably, damaging the body Prevalence of environmentally induced cancer has been underestimated Hard