1. Environmental Science PowerPoint Lecture
Principles of Environmental
Science - Inquiry and Applications,
2nd Edition
by William and Mary Ann Cunningham
After studying this chapter you should be able to:
*define health and disease in terms of some major environmental hazards that affect humans
*identify some major infectious organisms and hazardous agents that cause environmental diseases
*distinguish between toxic and hazardous chemicals, and between chronic and acute exposures and responses
*compare the relative toxicity of some naturl and synthetic compounds, and report on how such ratings are determined and what they mean
*evaluate the major environmental risks we face and how risk assessment and risk acceptability are determined

2. Acute effects – caused by single exposure
Bioaccumulations – selective absorption and storage of great variety molecules, dilute in environment but concentrated
Biomagnification – effect toxins magnified through food webs
Cancer – invasive out of control cell growth
Carcinogens – substances cause cancer
Chronic effects – single exposure very toxic or continuous exposure
Emergent disease – one never known before or absent at least 20 years
Fetal alcohol syndrome – a teratogen causing craniofacial abnormalities, development delays, behavior problems, mental defects
Hazardous – dangerous, can be diluted to not be dangerous
Health – state of complete physical, mental, social well being, not just an absence of disease
Morbidity – illness
Mutagens – chemicals alters genetic materials
Prospective study – identify study group and control and monitor long-term and see what affects health
Retrospective study – identify group exposed to risk factor and compare to control
Risk – probability of harm and probability of exposurre
Synergism - 1 substance multiplies effects of another, occupational asbestos increases lung cancer or smoking increases cancer
Toxins – poisonous reacts with specific cellular components to kill cells, not dilute to make less poisonous
Teratogens – cause abnormalities during growth of embryo. Thalidomide was a sedative used as sleeping pill resulted in fetal alcohol symptoms.

3. Chapter 8 - Topics Types of Environmental Health Hazards
Movement, Distribution, and Fate of Toxins
Mechanisms for Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment and Acceptance
Establishing Public Policy

4. Objectives of Chapter 8
Define health and disease in terms of major environmental factors that affect humans
Identify some major infectious organisms and hazardous agents that cause environmental diseases
Distinguish between toxic and hazardous chemicals, between chronic and acute exposure and responses
Compare toxicity of natural and synthetic compounds and how these are determined
Evaluate major environmental risks and how determine susceptibility

5. Rachel Carson - A Voice for Nature
In 1962, Silent Spring alerted the public to the dangers of indiscriminate pesticide use.
Carson called for selective, ecologically sound use of pesticides.
All 12 of the most toxic agents in her book were banned or severely restricted.
Between 1945 and 1960, aerial spraying of pesticides increased 5 fold in US
Rachael Carson, marine biologist, alerted public to dangers of indiscriminate release of toxic chemicals into the environment
Used facts and had good scientific foundation for her arguments
Silent Spring created big controversy especially with the chemical industry that spent lots of money to picture her as a hysterical spinster
Book became big best seller and within a year more than 40 bills were introduced in state legislator bodies to regulate pesticide use.
All 12 of the most toxic agents described in the book were banned or severely restricted
Caused a major shift in our environmental consciousness and started the environmental movement

6. Part 1: Types of Environmental Health Hazards
Polish mothers giving oxygen treatments to their children who are suffering from air pollution related respiratory diseases.
In Poland, people have been known to go to spas but not in our typical model of a spa of warm weather with palm trees but in caves. The air in caves is clean and does not have all the pollutants that are found in areas outside of the caves.
In some parts of Eastern Europe and the former USSR, up
to 90% of all children suffer from air pollution related respiratory diseases.

7. What is Health?
The World Health Organization defines health: state of complete physical, mental, social well-being – not just absence of disease.
Disease - a deleterious change in the body’s condition in response to an environmental factor
Morbidity - illness
Mortality - death
Disease – an environmental factor can affect could be due to nutritional, chemical, biological or psychological factors.
Link between disease and
poor nutrition
Sanitary systems non-existent
No vaccination against diseases
Chapter shows links between the above
Most people are healthier than before and they live longer

8. Nutrition-unrelated (genetic) Nutrition-related
Iron-deficiency anemia
Vitamin deficiencies
Mineral deficiencies
Toxicities
Poor resistance to disease
Down syndrome
Hemophilia
Sickle-cell anemia
Adult bone loss
Cancer
Infectious diseases
Diabetes
Hyper-tension
Heart disease
Adult bone loss = osteoporosis
Some health problems humans have to deal with are strongly nutrition based while others have more of a genetic control. The nutrition based health problems can be dealt with by changing people’s nutrition or food type and amount. Some of the health problems are both modified by the individual genetics of a person which can determine the impact of a nutrient based problem.
Nutrition-unrelated (genetic)
Nutrition-related

9. 1997 data
Ex: Tuberculosis
Deforestation causes insect vectors to move to cities
WHAT KNOWLEDGE DO YOU HAVE FROM KNOWNING WHAT ARE THE LEADING CAUSES OF DEATH? IN THE OLDEN DAYS, CHRONIC LUNG DISEASES WERE THE HIGHEST CAUSE OF DEATH AND WAS RELATED TO INDUSTRIAL DEVELOPMENT, POOR NUTRITION AND HEALTH. TODAY, OUR LIFESTYLE IS HAVING AN IMPACT ON THIS SINCE CARDIOVASCULAR DISEASES AND CANCERS ARE RELATED TO LIFESTYLE.
43% of all deaths related to disease are due to infectious diseases. Most of the deaths are in the poorer parts of the world where (1) nutrition is poor, (2) sanitary systems may be non-existent and (3) vaccinations against diseases is not common. Infectious diseases used to be the primary cause of death in the past and has been replaced by cardiovascular diseases and cancers. FIRST TWO (CARDIOVASCULAR DISEASE, CANCERS) NOT CONTRACTED BY SPREAD BY HUMANS BUT WHAT WE EAT OR ARE EXPOSED TO IN THE ENVIRONMENT. CHRONIC LUNG DISEASE LIKE TB IS A COMMUNICABLE DISEASE SPREAD BY HUMANS.
PERINATAL CONDITIONS – BIRTH BABIES; DIARRHEA – HIGH, MAINLY CHILDREN 5 YEARS OLD
Even though we talk about all of the bad diseases that are causing mortality,most people on average are healthier than ever as can be seen with people living longer than before (life expectancy has increased from 40 years to 65 years during the past century).
Acquired immune deficiency syndrome (AIDS) was virtually unknown 15 years ago and has become the firth greatest cause of contagious deaths. 2/3 of the AIDS patients are in the sub-Sahara Africa – many of these countries have not been willing to acknowledge that they had AIDS patients (this was attributed to evil spirits) so that no treatment was available and the cost of the medicine has been too high (treating a single patient can cost $10,000 / year).
The second most deadly communicable disease is malaria. Any of you who have traveled to distance parts of the world where mosquitoes are commonly found have had to take medicine for malaria prevention. Sometimes the medicine is really bad causing people to sun burn easily and to have nightmares. DON’T HAVE CURE BUT HAVE PREVENTION. ONCE FELT WAS ERADICATED IS RESURGING
How many of you have traveled outside of the US and not had any health problems? Diarrhea is not uncommon when people visit another area because you are not adapted to the microorganisms
SMALLPOX ERADICATED IN 1977, POLIO IN 2000 BUT RESURGING

10. Morbidity and Quality of Life in Poor Households
Problems people live in crowded conditions –new global mega cities - poor at managing human generated wastes etc
Death rate does not tell everything, many people are sick and the quality of life is diminished
Recent but controversial approach to measure disability or loss of quality of life is the Disability-Adjusted Life Year or DALY. This measure combines premature deaths and loss of a healthy life resulting from illness or disability. It attempts to determine the total burden of a disease not just death. THIS DEFINES THE # OF YEARS LOST DUE TO PREMATURE DEATH AND DISABILITY. About 90% of DALY losses occur in the developing world. The women in sub-Sahara suffer 6 X the disease burden per 1,000 population as women in most European countries.
10-40% reduction in DALY burden with if better garbage and human waste disposal, clean water, childhood inoculations
Death rates not total picture but quality of life severely diminished important

11. Elephantiasis – caused by parasitic worm
Elephantiasis is caused by a parasitic worm that blocks lymph vessels and cause fluid accumulation in various parts of the body.
QUALITY OF LIFE DIMINISHED.
SOME PROGRESS ERADICATING PARASITIC DISEASES SUCH AS RIVER BLINDNESS (NEMATODES SPREAD BY BITE OF THE BLACK FLY). DEAD WORMS ACCUMULATE IN EYE BALL DESTRYOING VISION. SOME AFRICAN VILLAGES, EVERY ADULT OVER 30 YEARS OF AGE ARE BLIND.
CONTROLLED BY INSECTICIDE SPRAYS – HOW BALANCE USE OF CHEMICALS AND DISEASE REDUCTION
At any given time, about 2 billion people (1/3 global population) suffer from worms, protozoans, other internal parasites

12. Recent outbreaks of lethal infectious diseases
At least 30 new infectious diseases have appeared in the past two decades while many well-known have reappeared in more virulent, drug-resistant forms. For example, the Ebola virus is thought to have originated in monkeys or other primates and is very contagious and often kills 90% of the people who are exposed to it. This increased incidence has been attributed to a greater frequency and more prolonged contact of humans with the primates as humans move into habitats where they might not have been as common.
This map shows that no part of the world is immune to a lethal outbreak of infectious diseases.
At least 30 new infectious diseases appeared in past two decades while many well-known reappeared in more virulent, drug-resistant forms.

13. High population densities Settlers pushing into remote areas
Factors Contributing to the Appearance and Spread of Contagious Diseases
High population densities
Settlers pushing into remote areas
Human-caused environmental change (use of fertilizers, pesticides etc)
Speed and frequency of modern travel
Contact with water or food contaminated with human waste
High pop densities – much higher pop clusters enabling germs to spread faster
Settlers pushing into remote areas – expanding populations push into remote areas & coming contact with new pathogens and parasites
Human caused environmental change (1) causing environmental change at massive scale (deforestation, mosquitoes), (2) nutrients, pesticides causing blooms of toxic algae in lakes and near shores, (3) habitat change and elimination favor disease carrying organisms (mice, rats – big problem in NYC, cockroaches, mosquitoes)
Speed of travel – few place that can’t reach in 24 hours by plane
Contact with water, food contaminated – Peru problem with contaminated fish, severe diarrhea disease, with bacteria, Sewage contaminated water dumped in harbors of cities is a big international problem. Waters become warmer with El Nino which increases the prevalence of bacteria.
This year the ocean liners have been having huge problems with contaminated food and surfaces causing cancellations of trips, cruise ships fined for dumping waste into ocean.

14. Antibiotic and Pesticide Resistance
Indiscriminate use antibiotics, pesticides - perfect recipe for natural selection
Protozoans cause malaria now resistant to most antibiotics, & mosquitoes developed resistance to many insecticides
Drug resistance: TB, Staph A, flesh-eating bacteria
Why are organisms resistant to pesticides and antibiotics (drug resistance): (1) organisms adapt – esepcially microbial group where life can be over in 24 hours, (2) human carelessness in use of chemicals.
Malaria was once thought to be nearly totally gone that has now resurfaced to kill many people (~ 3 million/yr) – 90% of this is occurring in Africa. The protozoan parasite that causes the disease is now resistant to most antibiotics while the mosquitoes that transmit the parasite have developed resistance to many insecticides. Spraying with DDT in India, Sri Lanka reduces malaria from millions / year to thousands in
Many examples of drug resistance to pathogens. Tuberculosis (TB) used to be the leading cause of death in the world and was mostly eliminated by the 20th century. However, drug resistant varieties are spreading rapidly. A problem has occurred in Russia where crowded prisons with poor sanitation, little medical care, and inadequate nutrition serve as a breeding ground for this deadly disease. Inmates who are treated with antibiotics rarely get a complete dose over time that would really cure them. Inmates with TB are not separated from healthy individuals so that it spreads. Patients with active TB are sent home and then spread this even further. ESKIMOS IN ALASKA CURED OF TB BUT NEEDED 6 MONTHS FOR CURE AND WOULD NOT CONTINUE TO USE FOR THIS TIME PERIOD.
Another bad problem is the appearance of drug-resistant strains of Staphylococcus aureus, the most common form of hospital-acquired infection. One strain of Staphylococcus is the flesh-eating bacteria that causes massive necrosis that destroys skin, connective tissue, and muscle.
A significant problem is that at least half of the antibiotics prescribed to humans in the US are unnecessary or are the wrong ones. Antibiotics are fed to cattle in low doses to stimulate weight gains which means these get into the human food chain.

15. Hazardous and Toxic Chemicals
Allergens – activates immune systems (formaldehyde, sick building syndrome)
Immune system depressants – pollutants suppress immune system (linked to pesticides – seals, dolphins)
Neurotoxins – metabolic poisons attack nerve cells (chloroform, ether, lead, DDT)
Mutagens – chemicals, radiation damage, alter DNA (birth defects, tumors)
Teratogens – chemicals cause abnormalities during embryonic growth, development (thalidomide, alcohol)
Carcinogens- cancer (uncontrolled cell growth)
Hazardous means dangerous. Many chemicals are hazardous in high concentrations but relatively harmless when diluted.
Toxins are poisonous – they react with specific cellular components to kill cells. Because of this specificity they are harmful even in dilute concentrations. Example of toxin is Ricin a protein found in castor beans and is one of the most toxic organic compounds known – this is 200 times more lethal than dioxin which is typically described as being one of the most toxic compounds around.
Aflatoxins are produced by microbes and has been a big problem in food or grain products. If hay is collected from the field and is not dried properly and the fungi start growing on it, you can be killed by inhaling minute amounts of the compounds produced. Farmers have been recorded through time to have died from this by going into their barns where hay was stored. You can see why this has been off interest in wars because of the high toxicity.
Allergens substances that active the immune system. They are perceived of by the body as a foreign body and cause the immune system to kick in. Formaldehyde is a good example of this. Some people are exposed to formaldehyde in plastics, wood products, insulation, glue, fabrics that have made people sensitive – sometimes called the sick building syndrome.
Immune system depressants – are pollutants that suppress the immune system rather than activating it, disrupt normal endocrine function so susceptibility to diseases increases. Not much is known about this and how this works but thought to have played a major role in widespread death of seals in the North Atlantic and dolphins in the Mediterranean. These dead animals has high levels of pesticide residues, polychlorinated biphenyls (PCBs) that may disrupt normal endocrine hormone functions and make the animals susceptible to infections.
Neurotoxins are a special class of metabolic poisons that attack nerve cells. Heavy metals, lead and mercury, kill nerve cells and cause permanent neurological damage. Anesthetics (ether, chloroform, etc) and chlorinated hydrocarbons (DDT, Dieldrin, Aldrin) disrupt nerve cell membranes necessary for nerve function. Most neurotoxins are acute and extremely toxic. More than 850 compounds recognized in this. GOLD MINING IN AMAZON.
Mutagens – agents (chemicals, radiation) that damage or alter genetic material (DNA) in cells. Result in birth defects, tumors,
Teratogens – chemicals or other factors that specifically cause abnormalities during embryonic growth and development. Ex. In the 1960s was thalidomide used as a sleeping pill in Europe. No effect except for pregnant women where caused abnormal fetal development causing sea-like limbs). Was never allowed to be sold in the US. Another example of a teratogen is alcohol – drinking during pregnancy can lead to fetal alcohol syndrome (behaviro problems, mental defects, developmental delays, craniofacial abnormalities)
Carcinogens – substance that cause cancer (invasive out of control cell growth that result in tumors). Cancer rates closely linked to industrialization.

16. Lead in industrialized countries one of the best cases showing a reversal in the use and damage due to lead. It was banned in US and levels dramatically decreased. Residues still left in old house with paint used in the past.
Remember Cassava and cyanides.
Poisonous – highly specific and kills cells, harmful even when dilute.
Gas, paint
Gold mining

17. Lung cancer Breast cancer
Age-adjusted cancer death rates in the US. When adjusted for an aging population, mortality for most major cancers has been stable or falling.
The total incidence of cancer is up but better treatment means more people survive. When age adjusted since live longer, cancer rates are going down.
Mortality rate most major cancers stabilized or falling in recent years. One exception is lung cancer (90% blamed on increased smoking esp women)

18. Importance of Diet
At least half of all Americans considered overweight
Strong correlation between cardiovascular disease and amount of salt and animal fat in diet
Fruits, vegetables, whole grains, complex carbohydrates, dietary fiber have beneficial health effects (anti-cancerous)
Eating too much food negative effects on health.
Selenium is a great example of an element that is needed by humans and humans get from eating plants. However, selenium is also the cause of all the abnormalities that were reported for birds who were living on agricultural retention ponds used to store irrigation water runoff in California. It was not the ponds themselves but that forming ponds where they did not naturally occur made the selenium that was naturally present in the soil to become solubilized and go into solution in the pond water. Many of aquatic birds started having abnormalities such as malformed wings etc.
Bio 2 example with rats and live longer but really cranky.
Some people live to (not well documented if correct) in the Mountains of the Caucasus, Pakistan Mtn – longest lived in world
Reasons for long-lived: (1) live at high elevation where climate is cool, dry and sunny, (2) lead active lives in low pressure non-industrialized settings (stress low and life predictable), (3) simple diet (low salt, fat, little meat and lots of fruits and vegetables)

19. Part 2: Toxins: Movement, Distribution, Fate
Movement, fate of chemicals in environment (processes that modify, remove or sequester compounds)
Knowing the fate and movement of chemicals in the environment tells us a lot about its potential impact on humans. Most chemicals are divided into two major groups: those that dissolve in water and those that dissolve more readily in oil. Water soluble compounds move more rapidly and widely through the environment because water is so ubiquitous and most human body cells contain water so they move easily within a human body. In contrast, oil or fat soluble compounds need a carrier to move them through the environment and into the human body. However once oil soluble compounds are in the body, they mover readily into tissues and cells because membranes in the body are made of similar oil-soluble chemicals. Oil soluble compounds accumulate in lipid deposits and can persist for years. There has been a concern for people loosing weight too rapidly and having chemicals stored in the lipid deposits being released too quickly at short time periods.
Solubility one of most important characteristics in determining how, where, and when a toxic material will move through the environment or through the body to its site of action. Chemicals separated into those chemicals that dissolve more readily in water and those in oil. Water-soluble compounds move rapidly and widely through the environment because water is ubiquitous and body cells are bathed in an aqueous solution. Oil soluble generally need a carrier to move through the environment and into the body. However, once inside the body, they penetrate readily into tissues and cells because membranes are made of similar oil-soluble chemicals. Oil soluble tend to accumulate and be stored in lipid deposits.

20. Part 2: Toxins: Movement, Distribution, Fate
Routes by which chemicals enter body determine toxicity
Solubility in fats or water
Problem with people loosing weight and rerelease of toxins stored in fatty tissues so need to go on diet slowly.

21. Bioaccumulation and Biomagnification
Bioaccumulation – selective absorption / storage of molecules; dilute toxins in the environment can reach dangerous levels inside cells and tissue
Biomagnification - the effects of toxins are magnified through food webs
Top carnivores: game fish, fish-eating birds, birds, humans accumulate toxic levels; adverse health effects
Bioaccumulation – selective absorption and storage of molecules. Toxins that are present at dilute levels in the environment can reach dangerous levels inside cells and tissues through this process.
Fungi with mushrooms with heavy metals and needing Geiger counters in markets in Moscow because of the radionucleotides from the Chernobyl accident.

22. to Humans” “DDT - Powerful Insecticide, Harmless
This was not an uncommon sight back in the 1950s where keeping the population level of insects down was done by directly spraying people. Pictures of spraying pesticides directly into the clothes of school kids. The sign on the truck says powerful insecticide harmless to humans

23. Top predator accumulated toxic levels of pesticides that was biomagnified through the food webs.
Pelegrine falcons disappeared from the eastern US in 1960s due to excess pesticide use

24. Not just in olden days – happening today
A Farm Worker Sprays Disinfectant onto the Shoes of Two Girls on a Quarantined Farm During an Outbreak of Avian Flu in Middleton South Africa, SOUTH AFRICA: August 10, 2004
A farm worker sprays disinfectant onto the shoes of two girls on a quarantined farm during an outbreak of Avian (bird) Flu near the town of Middleton in the eastern Cape region of South Africa August 6, 2004.
An estimated 1500 ostriches have died of the highly infectious H5N2 strain with authorities deciding to cull up to 6000 in the next few days. The country's large ostrich industry is threatened by the outbreak as 90 per cent of production is exported.
Story by HB/MD, Photo by HOWARD BURDITT, REUTERS NEWS PICTURE SERVICE
Not just in olden days – happening today
A Farm Worker Sprays Disinfectant onto the Shoes of Two Girls on a Quarantined Farm During an Outbreak of Avian Flu in Middleton South Africa, SOUTH AFRICA: August 10, 2004 , Story by HB/MD, Photo by HOWARD BURDITT, REUTERS NEWS PICTURE SERVICE

25. Chemical Interactions -
Children more susceptible than adults –accumulate environmental contaminants in higher concentrations in body, eat more food with higher contaminant loads (apple products etc)
Persistence –
Chemical Interactions -
This is a table from the book and identifies some of the factors that are important in determining the toxicity of chemicals in the environment.
Sensitivity and developmental stage: Children are especially susceptible to environmental contaminants. Found that children eat a lot of apples and other similar products that have been sprayed with chemicals and accumulate higher levels of these chemicals than adults.
Farm children in Mexico exposed to high levels of crop pesticides exhibited abnormal social behavior – high level of anger, aggression, autism, and attention deficit disorder.
Persistence: What makes some of the compounds valuable for controlling pests is their persistence in the environment. Most modern pesticides and herbicides loose their toxicity quickly.
Chemical Interaction: some materials have antagonistic reactions – interfere or stimulate breakdown of other chemicals. Some positive with Vitamins E and A reducing responses to carcinogens. While other are synergistic and multiplies the effect of one another. Ex – occupational asbestos exposure increases lung cancer rates 20-fold. Smoking increases lung cancer rates.

26. Part 3: Minimizing Toxic Effects
Every material can be poisonous under some conditions
Taken in small doses, most toxins can be broken down or excreted before they do much harm – belief in 1800s, arsenic (Napoleon)
Liver - primary site of detoxification
Tissues and organs - high cellular reproduction rates replace injured cells - down side: tumors, cancers possible
Most chemicals have safe level not toxic but everything can be toxic. Eat too many carrots and cause health problems.
Even salt can be poisonous so it is the amount that you consume that determines whether it is bad or not. You need salt (vegemite in Australia – yeast with high salt). If you were forced to ingest a kilogram of salt, you would become sick and if this amount was injected into your bloodstream it would be lethal.
Two mechanisms: 1) metabolic degradation and excretion; 2) repair mechanisms – repair injured cells, however high repair most likely develop into cancer
Liver – enzymes process waste products and environmental poisons to reduce toxicity

27. Part 4: Measuring Toxicity
Animal Testing
Used to be most commonly used and widely accepted but now less common
Expensive - hundreds of thousands of dollars to test one toxin at low doses
Time consuming
Often very inhumane
Difficult to compare toxicity of unlike chemicals or different species of organisms
Expose a population of laboratory animals to measured doses of a specific substance under controlled condition.
Animal testing being replaced by computer simulations of model reactions, cell cultures and other substitutes. Artificial skin to test cosmetics now.
Difficult to compare toxicity since tobacco effect as an insecticide but humans not killed by it but purported to reduce quality of life and length of life.

28. A Typical Dose/Response Curve – toxin sensitivity among members of a population
Toxin sensitivity among members of a specific population. Bell shaped curve.
Other problems in laboratory animal testing troubles toxicologists and policymakers: differences in toxin sensitivity among members of a specific population. The curve above is a hypothetical scenario of response to a toxin. Some individuals are really sensitive while others are not. Most fall in the middle category so get a bell shaped curve. The problem is do we set pollution levels that will protect everyone including the most sensitive people or only protect the average person. It may cost billions of dollars to protect people at the extreme end of the curve. Do resources exist to do this.
Big question for regulators is whether to set pollution levels to protect everyone or average person. Costs billions dollars to protect most sensitive part of the population.

29. LD50 - the dose of a toxin that is lethal to half the test population
Dose curve not always symmetrical making it difficult to compare toxicity of unlike chemicals or different species of organisms. Convenient way to describe toxicity is to determine the dose to which 50% of the test population is sensitive. This is called the lethal dose.
Difficult to compare different chemicals or different species or organisms so standardize to describe toxicity.

30. Useful to group materials according to their relative toxicity.
mouse
rat
Here you can see the different sensitivities of different animals being tested for their sensitivity to particular chemicals. Note the LD50 for dioxin for the guinea pig (600 ng/kg) versus the hamster (3 mg/kg) which tolerates a higher amount of dioxin before reaching the LD50 (the dose of a toxin that is lethal to half the test population). So hamsters are 5,000 less sensitive to dioxin than guinea pigs.
Of the 226 chemicals that are carcinogenic to rates and mice, 95% cause cancer in one but not in the other.
Useful to group materials according to their
relative toxicity.

31. Acute Versus Chronic Doses and Effects
Acute effect - immediate health effect caused by a single exposure to a toxin (can be reversible)
Chronic effect - long lasting or permanent health effect caused by (1) a single exposure to a very toxic substance or (2) continuous or repeated sublethal exposure to a toxin
To study effect – give larger doses to measure maximum tolerance.

32. Part 5: Risk Assessment and Acceptance
Risk - the probability of harm times the probability of exposure
A number of factors influence how we perceive relative risks associated with different situations
Accepting risks - we go to great lengths to avoid some dangers, while gladly accepting others (ACCEPT HIGHER RISK WHEN ENJOY SOMETHING)
Even when we know that something is toxic, assessing the risk – the probability of harm- from exposure of harm is difficult to determine. Many factors contribute to the magnitude of risk as a chemical moves through the environment and public perceptions of relative danger can be skewed so that some risks are seen as being more important than others. SOPHISTICALED ABILITY OF DETECTING CHEMICAL MAY MAKE US THINK IS RISK WHEN MAY NOT BE IN FACT.
How we perceive risk is affected by:
People with social, political or economic interests tend to downplay certain risks and emphasize others that suit their agenda.
Many people have difficulty understanding and believing probabilities.
Our personal experiences are often misleading. If we have not personally experienced a bad outcome, we tend to think it is rare.
We have an exaggerated view of our abilities to control our fate. We think we are above average drivers, safer than most when using appliances or power tools, and less likely than others to suffer medical problems.
News media give us a biased perspective on the frequency of certain kinds of health hazards – over reporting some accidents or diseases while downplaying others. Gory or sensational causes of death get undo attention such as murders, plane crashes, fires or terrible accidents. Heart diseases, cancers and strokes kill nearly 15 X as many people as accidents in the Us and 75 X as many people as do homicides.
We tend to have an irrational fear or distrust of certain technologies or activities that leads us to overestimate their dangers. Nuclear power is viewed as very risky while coal-burning power plants seem familiar and relatively benign – coal plants cause an estimated 10,000 deaths yearly in US while nuclear none so far.
People are more accepting of risk that occurs at a low frequency. For most people, a 1 in 100,000 chance of being injured or dying over some event is a threshold for changing what they do. At this risk, we won’t change behavior. For activities we enjoy we are willing to accept far greater risks than this general threshold. For example your risk of dying in a motor vehicle in any given year is 1 in 5,000 but that does not deter people from driving. IF ENJOY, WILLING TO ACCEPT HIGHER RISK.

33. WHEN MORE CONTROL RISK – LEFT OR RIGHT OF FIGURE?
This figure shows the actual deaths that have occurred with a particular activity. The activities that have the lowest deaths are in fact those that our perceptions of risk are higher that we could die from that activity or scenario.
PERCEPTIONS OF RISKS AFFECTED BY (1) WHETHER RISKS ARE KNOWN OR UNKNOWN, (2) HOW MUCH IN CONTROL OF OUTCOME, (3) HOW DREADFUL RESULTS. More emotions than statistics drive public perception of risk.

34. Even though actual number of deaths from automobile accidents, smoking or alcohol are thousand times greater than from pesticides, nuclear energy, or genetic engineering, the latter preoccupy us far more than the former.
Table 8.6 gives some activities that are estimated to increase your changes of dying in any given year by 1 in 1 million. What is interesting how readily we accept some risks but not others. For example, living 2 days in New York or Boston and dying from air pollution (in fact, Seattle ranks very poorly in terms of air quality in the bottom 5% of a ranking system where 100% is good). It is hard to think of all of these issues and what do you do about it. You can’t worry about all of these things because you won’t be able to live or do anything with your life – you can’t lock yourself in your house and do nothing (you will probably die from the bad air in the house). The public perception of risk is emotionally based. Even though the actual number of deaths from automobile accidents, smoking or alcohol are thousand times greater than those from pesticides, nuclear energy, or genetic engineering, the latter preoccupy us far more than the former.

35. The apparent differences in the perceptions of risk by the public and by the agency mandated to regulate risk to various chemicals. Note the risk for chemical plant accidents that is low for EPA but high for the public. Only outdoor air pollution and accidental oil spills do we have agreement on the level of risk perceived by the public and EPA. For indoor air pollution, safety of drinking water, worker exposure to chemicals on the job are the perceived risks higher by EPA than the public. How much does this reflect the use of science or the fact that we don’t have adequate science to defend our perceived risk to health?

36. Part 6: Establishing Public Policy
In setting standards for environmental toxins, we need to consider:
Combined effects of exposure to many different sources of damage
Different sensitivities of members of the population
Effects of chronic as well as acute exposures
Saccharin example of uncertainties in risk assess
-link saccharin and bladder cancer in male rats (U. Wisconsin study)
-Critics, humans have to drink 800 cans of diet drink / day to get equivalent dose.
In 2000, no association found between saccharin and risk.

37. Regulatory Decisions – EPA framework
Risk assessment organizes and analyzes data to determine relative risk. This is the framework used by EPA to assess risk. This ranking reflects a concern that our exclusive focus on reducing pollution to protect to protect human health has neglected risks to natural ecological systems. The case by case approach that is used to evaluate risk to humans misses the broader ecological problems that may be of great importance and also ignores the fact that the causes of risks interact with one another and may aggravate the real risk (multiple factors ignored).
SETTING STANDARDS NEED TO CONSIDER: IS CASE BY CASE BASIS AND IGNORES MULTLIPLE EFFECTS AND INTERACTIONS.
Other Factors Not Specific to the Problem
The Science Specific to the Problem

38. How much of ranking is based on our values – do they reflect science?
How determine what risk is from human compared to naturally occurring physical/ chemical changes in the environment?
How much of ranking is based on our values – do they reflect science?
Lots uncertainty
This ranking reflects a concern that our exclusive focus on reducing pollution to protect human health has neglected risks to natural ecological systems. The case by case approach that is used to evaluate risk to humans misses the broader ecological problems that may be of great importance and also ignores the fact that the causes of risks interact with one another and may aggravate the real risk (multiple factors ignored).