© 2014 Pearson Education, Inc. Lecture Outlines Chapter 14 Environmental Health and Toxicology...

© 2014 Pearson Education, Inc.

Lecture Outlines

Chapter 14

Environmental Healthand Toxicology

Withgott/Laposata

Fifth Edition


This lecture will help you understand:

Environmental health and hazards

Toxic substances in the environment and factors that affect their toxicity

Defenses organisms posses against toxic substances

Movement of toxic substances and their affect on ecosystems

Hazards and their effects

Risk assessment and risk management

Philosophical approaches to risk

Regulatory policy in the United States and internationally


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


Central Case Study: Poison in the Bottle: Is Bisphenol A (BPA) Safe? Numerous scientific panels have examined the health

risk of BPA 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



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


Disease is a major focus of environmental 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


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


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


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


Many environmental health hazards exist 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


Many environmental health hazards exist 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


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

Toxins = toxic chemicals made in tissues of living organisms Chemicals plants use to defend themselves

But synthetic chemicals are also in our environment 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


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


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

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


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


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


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)


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


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


Human studies rely on case histories, epidemiology, and animal testing

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.


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

The interactive effects of most chemicals are unknown


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 analyzes risk quantitatively

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


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

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 Europe incorporates the precautionary principle The United States uses the innocent-until-proven-guilty

approach 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


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


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



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


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


QUESTION: Review

Which of the following is a cultural hazard?

a) Earthquake

b) Smoking

c) Viruses

d) A pesticide

e) All are cultural hazards.


QUESTION: Review

Toxicology is

a) the study of the effects of poisonous substances.

b) any toxic substance.

c) any substance that causes environmental degradation.

d) the degree of harm a substance can cause.


QUESTION: Review

Which of the following damages the brain and liver, causes learning problems, and comes from water flowing through certain pipes?

a) Radon

b) Asbestos

c) Lead

d) Polybrominated diphenyl ethers


QUESTION: Review

A “carcinogen” causes

a) cancer.

b) mutations.

c) birth defects.

d) problems in the hormonal system.


QUESTION: Review

A study that observes individual patients (e.g., autopsies) uses

a) an epidemiological study.

b) a case history approach.

c) mainly private funding sources.

d) probability and risk as major components of the study.


QUESTION: Review

Which statement about endocrine disruptors is NOT true?

a) They may show unconventional dose-response curves.

b) They affect reproduction, development, and immunity.

c) It is easy to study their effects and show causation.

d) The endocrine system is vulnerable to very low levels of these disruptors.


QUESTION: Viewpoints

Should the United States be able to manufacture and export chemicals that have been banned to use in the United States?

a) No; if we won’t use it in the United States, we shouldn’t be able to make and export it to others.

b) Yes, because the money we get from selling it will help our economy.

c) Yes; let people decide what they want to do.

d) Yes; in fact, chemicals should not be banned in the United States, either.


QUESTION: Viewpoints

How should the U.S. government regulate chemicals?

a) The government should force industries to prove their products are safe.

b) The government should prove a chemical is dangerous before it is taken off the market.

c) Industry knows chemicals best, so decisions such as this should be left up to the industry.

d) As long as the product makes money and jobs for the industry, it should be allowed, even if some people get sick or die from it.


QUESTION: Interpreting Graphs and Data

Which of the following can we say about the rates of smoking and obesity in the United States based on this graph?

a) Obesity has risen faster than smoking has declined.

b) Decreased smoking has caused increased obesity.

c) Obesity rates havefallen.

d) There has been a 75% drop in smoking rates.


QUESTION: Interpreting Graphs and Data

If the “low” dose = 5 units of a chemical, the “medium” dose = 10 units, and the “high” dose = 15 units, how much of the chemical is required to kill 50% of the study population?

a) About 5 units

b) About 10 units

c) About 15 units

d) You can’t tell from the graph.

© 2014 Pearson Education, Inc. Lecture Outlines Chapter 14 Environmental Health and Toxicology...

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