central case: lake apopka alligators


Central Case: Lake Apopka alligators

• In 1985, alligators in Lake Apopka, Florida, had bizarre reproductive problems

- Non-viable eggs, depressed or elevated hormone levels

• The lake had high levels of agricultural chemicals and fertilizers that were disrupting the endocrine systems of alligators during development in the egg.

- Endocrine disruptors: compounds that mimic hormones and interfere with the functioning of animals’ endocrine (hormone) systems

• Because alligators and humans share the same hormones, chemicals can affect people, too.


Activity:

• Read the short article Alligators and Endocrine Disruptors in Lake Apopka, Florida

• Short Class Discussion

• Louis Guillette’s article: Silent Reading in class

• Handout assignment attached to article

- Due typed 11/30

• HW: Outline pg. 212-222

• Reduction in Penis Size and Plasma Testosterone Concentrations in Juvenile Alligators Living in a Contaminated Environment


Activity: 4/24/12

• Outline pg. 223-230


“The dose makes the poison”What does this mean?

Ecotoxicology, Continued


There are many types of environmental hazards

• Environmental health: assesses environmental factors that influence human health and quality of life

• There are 4 major types of environmental hazards:

- Take a minute and list them on a sheet of paper: explain what it is and give several examples of each

• Much of environmental health consists of taking steps to address the impacts and risks of hazards.

- We can’t avoid risk, but we can minimize its effects.


Four types of environmental hazards


Chemical and biological environmental hazards

• Physical hazards: occur naturally in our environment

- Earthquakes, volcanoes, fires, floods, droughts

- Ultraviolet radiation from sunlight damages DNA.

- We increase our vulnerability by deforesting slopes (landslides), channelizing rivers (flooding), etc.

- We can reduce risk by making better environmental choices.

• Chemical hazards: synthetic chemicals such as pesticides, disinfectants, pharmaceuticals

- Harmful natural chemicals also exist.


Cultural environmental hazards

• Biological hazards: result from ecological interactions

- Viruses, bacteria, and other pathogens

- Infectious (communicable, or transmissible) disease: other species parasitize humans, fulfilling their ecological roles

- We can reduce the likelihood of infection.

• Cultural (lifestyle) hazards: result from the place we live, our socioeconomic status, our occupation, our behavioral choices

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


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

- Malnutrition, poverty, and poor hygiene can foster illnesses.


Infectious diseases kill millions

• Infectious diseases kill 15 million people per year.

- Half of all deaths in developing countries

- Developed countries have better hygiene, access to medicine, and money.

• Vector: an organism that transfers pathogens to a host


Many diseases are increasing

• Tuberculosis, acquired immunodeficiency syndrome (AIDS), and the West Nile virus are increasing.

- Our mobility spreads diseases.

• Some diseases are evolving resistance to antibiotics.

• Climate change will expand the range of diseases.

• Habitat alteration affects the abundance, distribution, and movement of disease vectors.


We are exposed to many hazards


Environmental health hazards exist indoors

• Radon: a highly toxic, colorless, undetectable radioactive gas

- Builds up in basements

- Can cause lung cancer

• Lead poisoning: from lead pipes, paint

- Damages organs, learning problems, behavior abnormalities, death

• Asbestos: insulates against heat, cold, sounds, and fire

- Asbestosis: scarred lungs don’t function

- Also causes a type of lung cancer

Asbestos removal can also be dangerous


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

- Affect thyroid hormones, may cause cancer, and affect brain and nervous system development

- The European Union banned them in 2003.

- The U.S. has not addressed this issue.


Toxicology is the study of poisonous substances• Toxicology: the study of the effects of poisonous

substances on humans and other organisms

• Toxicity: the degree of harm a chemical substance can cause

- “The dose makes the poison”: toxicity depends on the combined effect of the chemical and its quantity

• Toxicant: any toxic or poisonous agent

• During the past century, we have produced many new chemicals.

- Public concern for health and the environment


Environmental toxicology

• Deals with toxic substances that come from or are discharged into the environment

• Focuses mainly on humans, using other animals as test subjects

- Animals can serve as indicators of health threats.

• Don’t forget: chemicals have played a crucial role in giving us our high standard of living.

- Food, medicine, materials, convenience


Toxic agents in the environment

• The environment contains countless natural chemicals that may pose health risks.

• But synthetic chemicals are also in our environment.

- Every human carries traces of industrial chemicals.

• Very few chemicals have been thoroughly tested.

- 100,000 chemicals are on the market today.

- We don’t know the effects, if any, they have.

80% of U.S. streams contain at least trace amounts of 82 wastewater contaminants.


Silent Spring began public debate over chemicals

• Rachel Carson published Silent Spring in 1962.

- Brought together studies to show DDT risks to people, wildlife, and ecosystems

- In the 1960s, pesticides were mostly untested and were sprayed over public areas, assuming they would do no harm.

• The book generated significant social change.


Activity: Define and explain how they effect the body:• Carcinogens:

• Mutagens:

• Teratogens:

• Neurotoxins:

• Allergens:

• Endocrine disruptors:

• Watch the Video: And the Band Played On:

• And the Band Played On

• For extra Credit:


Types of toxicants based on health effects

• Carcinogens: cause cancer

• Mutagens: cause DNA mutations

- Can lead to severe problems, including cancer

• Teratogens: cause birth defects

• Neurotoxins: assault the nervous system

- Heavy metals, pesticides, chemical weapons

• Allergens: overactivate the immune system

• Endocrine disruptors: interfere with the endocrine (hormone) system


Endocrine disruption may be widespread

• Theo Colburn wrote Our Stolen Future in 1996.

- Synthetic chemicals may be altering hormones.

- This book integrated scientific work from various fields.

- Shocked many readers and brought criticism from the chemical industry


Chapter 5 - How They Get Into Water - YouTube


Evidence for hormone disruption

• Frogs also have gonadal abnormalities.

- Male frogs exposed to very low levels of atrazine became feminized.

- Levels were below EPA standards for human health.

• The shocking drop in men’s sperm counts may be due to endocrine disruptors.


Endocrine disruption research is controversial

• Scientific uncertainty is inherent in any young field.

• Negative findings pose economic threats to chemical manufacturers.

- Bisphenol-A, used in plastics, causes birth defects, but the plastics industry protests that the chemical is safe.

- Pthalates affect male fetuses but are still used in toys and makeup in the U.S.


Toxicants are found in water and air

• Water carries toxicants from land areas to surface water.

- Chemicals can leach through the soil into groundwater.

- Chemicals enter organisms through drinking or absorption.

- Aquatic organisms (fish, frogs, stream invertebrates) are effective pollution indicators.

• Because chemicals can travel by air, their effects can occur far from the site of use.

- Pesticide drift: airborne transport of pesticides

- Synthetic chemical contaminants are found globally.

- Arctic polar bears, Antarctic penguins, and people living in Greenland

- Article:


Routes of chemical transport


Activity:

• Read Article in Class

• Answer Questions in groups

• Each group will present their findings to class

• Calculate your dose!!


Some toxicants persist• Toxins can degrade quickly and become harmless.

- Or they may remain unaltered and persist for decades.

- Rates of degradation depend on temperature, moisture, and sun exposure.

• Persistent chemicals have the greatest potential for harm.

• Breakdown products: toxicants degrade into simpler products

- May be more or less harmful than the original substance

- i.e., DDT degrades into DDE, which is also highly persistent and toxic


Toxicants can accumulate and biomagnify

• Some toxicants can be excreted or metabolized.

- Fat-soluble toxicants are stored in fatty tissues.

• Bioaccumulation: toxicants build up in animal tissues- the mvmt

• Biomagnification: toxicants concentrate in top predators- the result

- Near extinction of peregrine falcons, bald eagles, and brown pelicans


Bioaccumulation:Polar Bear accumulates more toxins due to diet

Biomagnification: Term used to describe the way in which toxins move; more in polar bears than algae


Activity:• Biomagnification Lab in Class

• Bald Eagle Migration Count

- On your graph, include the following:

1. The year Rachel Carson’s Book Silent Spring was published

2. The year the Bald Eagle was placed on the Endangered Species Act

3. The year the Endangered Species Act was passed

4. The year Richard Nixon banned DDT use in the US

5. The year Paul Muller wins Nobel Prize for DDT

6. The year the Bald Eagle Act was passed

7. The year the Bald Eagle was officially taken off the Endangered Species List


Timeline for Graph:

• 1) 1940: Bald Eagle Act passed

• 2) 1948: Paul Muller wins Nobel Prize for DDT

• 3) 1962: Rachel Carson’s Book Silent Spring is published

• 4) 1972: US Bans the Use of DDT (in the US)

• 5) 1973: The Endangered Species Act is Enacted

• 6) 1976: The Bald Eagle is Placed on the Endangered Species List (in the lower 48)

• 7) 1995: The Bald Eagle moves from Endangered to Threatened


Not all toxicants are synthetic

• Chemical toxicants also exist naturally and in our food.

- Don’t assume natural chemicals are all healthy and synthetic ones are all harmful.

• Scientists are debating just how much risk natural toxicants pose.

- Plants produce toxins to ward off herbivores.

- When we consume meat, we take in toxins the animals have ingested.


Studying the effects of hazards

• Animals in the wild are observed to determine the cause of sickness or death.

• In human health studies, researchers study and treat sick individuals.

• Epidemiological studies: large-scale comparisons between groups of people

- Studies between exposed and unexposed people last for years.

- AIDS and the Bubonic Plague

• Animals are used as subjects to test toxicity.

- Rats, mice, other mammals


Dose-response analysis

• Dose-response analysis: measures how much effect a toxicant produces at different doses

- Animal testing

- Dose: the amount of toxicant the test animal receives

- Response: the type or magnitude of negative effects

- Dose-response curve: the plot of the dose given against the response

- Looks at lethal doses (LD50) or effective doses (ED50)


Dose response curves

• LD50/ED50: the amount of toxicant required to kill (affect) 50% of the study animals used

- A high LD50/ED50 indicates low toxicity.

• Threshold: the dose level where certain responses occur

- Organs can metabolize or excrete low doses of a toxicant.

- Some toxicants that work at extremely low levels show a J-shaped, U-shaped, or inverted curve.

• Scientists extrapolate downward from animal studies to estimate the effect on humans.

- Regulatory agencies set allowable limits well below toxicity levels from lab studies.


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.

- Increased sensitivity in fetuses, infants, and children

• Standards for responses are set by the Environmental Protection Agency (EPA).

- Often, standards are not low enough to protect babies.


The type of exposure affects the response

• Acute exposure: high exposure for short periods of time to a hazard

- Easy to recognize

- Stem from discrete events: ingestion, oil spills, nuclear accident

• Chronic exposure: low exposure for long periods of time to a hazard

- More common but harder to detect and diagnose

- Affects organs gradually: lung cancer, liver damage

- Cause and effect may not be easily apparent.


Mixes may be more than the sum of their parts• It’s hard to determine the impact of mixed hazards.

- They may act in ways that cannot be predicted from the effects of each in isolation.

• Synergistic effects: interactive impacts that are more than or different from the simple sum of their constituent effects

- Mixed toxicants can sum, cancel out, or multiply each other’s effects.

- New impacts may arise from mixing toxicants.

• Single-substance tests receive priority but this is changing.


Activity Today: • Testing Your Comprehension Questions:

- 1-10

• Homework: Take home lab and do first part over the weekend

• Read the Pesticides and Childhood Development article on page 224-225.

- Write a short paper explaining:

- Why this was a perfect design for an experiment

- What the actual experiment was

- What the date revealed

• Lab on Monday!!!!!


Lab Day Tomorrow

• Toxicology Lab• LD50 and MSDS

• 2 parts:

- Take lab home and complete part 1

- Bioassay tomorrow in class w/Brine shrimp

- You will then have 2 days to bring back a completed lab write up

- Must be typed, graphs need to be completed in EXCEL


Risk assessment

• The steps between obtaining scientific data and policy formulation involve assessing and managing risk.

• Risk: the probability that some harmful outcome will result from a given action, event, or substance

- Exposure to a health threat doesn’t always produce an effect.

- Rather, it causes some probability (likelihood) of harm.

• Probability entails:

- Identity and strength of threat

- Chance and frequency of an encounter

- Amount of exposure to the threat

- An organism’s sensitivity to the threat


Perceiving risks

• Everything we do involves some risk.

• We try to minimize risk, but we often misperceive it.

- Flying versus driving

• We feel more at risk when we cannot control a situation.

- We fear nuclear power and toxic waste, but not smoking or overeating.


Analyzing risk quantitatively

• Risk assessment: the quantitative measurement of risk and the comparison of risks involved in different activities or substances

- It is a way of identifying and outlining problems.

• Assessing risk takes several steps:

- Scientific study of toxicity (dose-response analysis)

- Assessing an individual or population’s extent of exposure to the substance, including frequency, concentrations, and length of exposure


Risk management

• Combines decisions and strategies to minimize risk

• Scientific assessments are considered with economic, social, and political needs and values.

• Federal agencies in developed nations manage risk.

- The U.S. has the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA).

• 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 being affected.


The process of risk management


Approaches to determining safety

• Two philosophies categorize a substance as safe or harmful.

- Are businesses required to prove a product is safe, or are the government, scientists, or citizens required to prove danger?

• Innocent until proven guilty approach:

- Assume products are harmless until proven harmful.

- Benefits: not slowing down technological innovation and economic advancement

- Disadvantage: putting into wide use some substances that may turn out to be dangerous


Another approach to determining safety

• Precautionary principle approach:

- The government, scientists, and the public are required to prove a product is dangerous.

- Assume substances are harmful until they are proven harmless

- Identifies troublesome toxicants before they are released

- But this may impede the pace of technology and economic advance


Two approaches for determining safety


Philosophy affects policy

• Most nations use a mix between the “innocent until proven guilty” principle and the precautionary principle.

- Europe is shifting more toward the precautionary principle.

- The U.S. generally follows the “innocent until proven guilty” approach.


The EPA regulates many substances

• Federal agencies share responsibility for tracking and regulating synthetic chemicals.

- FDA: food, food additives, cosmetics, drugs, medical devices

- EPA: pesticides

- Occupational Safety and Health Administration (OSHA): workplace hazards

• Many public health and environmental advocates fear it isn’t enough.

- Many synthetic chemicals are not actually tested.

- Only 10% have been tested for toxicity.

- Fewer than 1% are government regulated.


International regulation of toxicants

• Nations address chemical pollution with international treaties.

• Stockholm Convention on Persistent Organic Pollutants (POPs) is nearing ratification.

- Ends the release of the 12 most dangerous POPs (“dirty dozen”)

• EU’s Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) Program (2007)

- Aims to evaluate and restrict dangerous chemicals while giving industries a streamlined regulatory system

- It will cost the chemical industry 2.8–5.2 billion euros (U.S. $3.8–7.0 billion), but public benefits will exceed 50 billion euros ($67.0 billion).


Conclusion

• International agreements represent a hopeful sign that governments are working to protect people, wildlife, and ecosystems from toxic chemicals and environmental hazards.

• Once all the scientific results are in, society’s philosophical approach to risk management will determine what policies are enacted.

• A safe and happy future depends on knowing the risks that some hazards pose and on replacing those substances with safer ones.


QUESTION: ReviewWhich of the following is a physical hazard?

a) Earthquakeb) Smokingc) Virusd) A pesticidee) All of the above are biological hazards.


QUESTION: ReviewAn organism that transfers pathogens to a hose is a(n):

a) Neurotoxinb) Vectorc) Cultural hazardd) Endocrine disruptore) Risk


QUESTION: ReviewA toxicant is:

a) The study of the effects of poisonous substancesb) Any toxic or poisonous agentc) Any substance that causes environmental

degradationd) The degree of harm a substance can causee) The amount of chemical an organism is exposed to


QUESTION: ReviewA “carcinogen” causes:

a) Cancerb) Mutationsc) Birth defectsd) Problems in the hormonal systeme) Nerve damage


QUESTION: ReviewWhy is research into endocrine disrupters controversial?

a) Negative findings threaten the industry’s economics

b) Research is still only beginningc) Industry protests that their products are safed) All of these are reasons why research is

controversial.e) None of these is true. This type of research is not

controversial.


QUESTION: ReviewIf a dose-response analysis has a low LD50, this means:

a) The substance has a low lethal toxicityb) The substance has a low effective toxicityc) The substance has a high lethal toxicityd) The substance has a high effective toxicitye) This type of substance does not exist


QUESTION: Interpreting Graphs and DataRefer to this graph that shows the real risk of various activities, and compare it to what our society feels about smoking versus flying. Which statement is correct?

a) Smoking is very dangerous and we are more anxious about it than flying.

b) Smoking is not dangerous, but we are more anxious about it than flying.

c) Airplane accidents are dangerous, and we are more anxious about flying than smoking.

d) Airplane accidents are not dangerous, but we are more anxious about flying than smoking.


QUESTION: Interpreting Graphs and Data

What conclusion can we draw about human male sperm production from this figure?

a) Sperm counts have increased in the past 50 years.

b) Sperm counts have decreased in the past 50 years.

c) Sperm counts have decreased, but women are still getting pregnant.

d) You can’t tell anything from the graph.


QUESTION: ViewpointsShould a country that has banned a chemical be able to still manufacture and export it to other countries?

a) No, if we won’t have it in the U.S., we shouldn’t make it.

b) Probably not, but the money we get from selling it will help our economy.

c) Yes, let other people decide what they want to do.d) Yes, in fact, chemicals should not be banned in

the U.S. either.e) I don’t care, since I’m going to live in the U.S.

anyway.


QUESTION: Viewpoints

Should a government follow the precautionary principle and force industries to prove their products are safe?

a) Absolutely. It is up to the industry to prove its chemicals are safe.

b) Maybe, if it is not too expensive.c) No, force the government and scientists to prove

a chemical is dangerous before it is taken off the market.

d) No, as long as the product makes money and jobs for the industry, it should be allowed.

central case: lake apopka alligators

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