1. Environmental Health and Toxicology
Chapter 22

2. Outline: Environmental Health Hazards Distribution and Fate of Toxins
Infectious Organisms
Emergent Diseases
Antibiotics and Pesticide Resistance
Toxic Chemicals
Distribution and Fate of Toxins
Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment
Public Policy

3. ENVIRONMENTAL HEALTH HAZARDS
Health - A state of complete physical, mental, and social well-being.
Disease - A deleterious change in the body’s condition in response to an environmental factor.
Diet and nutrition, infectious agents, toxic chemicals, physical factors, and psychological stress all play roles in morbidity (illness) and mortality (death).

4. Infectious Organisms
For most of human history, the greatest health threats have been pathogenic organisms.
Infectious diseases are still responsible for about 33% of all disease-related deaths.
Majority of deaths in poorer countries with poor nutrition, sanitation, and vaccination programs.

5. Morbidity and Quality of Life
Death rates do not tell everything about burden of disease.
Total economic and social consequences of diseases are difficult to obtain.
Disability-Adjusted Life Year (DALY) combines premature deaths and loss of healthy life resulting from illness or disability.

6. Disability-Adjusted Life Year
WHO reports communicable diseases are responsible for nearly half of all 1.2 billion DALY’s lost each year.
About 90% of all DALY losses occur in developing world where one-tenth of all health care dollars are spent.
Malnutrition exacerbates many diseases.

7. Emergent Diseases
An emergent disease is one never known before, or has been absent for at least 20 years.
An important factor in the spread of many diseases is speed and frequency of modern travel.
Foot and Mouth Disease
Ebola

8. Emerging Ecological Diseases
Domestic animals and wildlife also experience sudden and widespread epidemics.
Distemper (Seals)
Chronic Wasting Disease (Deer and Elk)
Transmissible Spongiform Encephalopathies
Black Band Disease (Coral)

9. In the News….

10. Infectious Disease Outbreaks

11. Antibiotic and Pesticide Resistance
Protozoan parasite that causes malaria is now resistant to most antibiotics, while the mosquitoes that transmit it have developed resistance to many insecticides.
Short life spans.
Speeds up natural selection and evolution.
Human tendency to overuse pesticides and antibiotics.

12. Antibiotic and Pesticide Resistance

13. Antibiotic Use
At least half of the 100 million antibiotic doses prescribed in the US every year are unnecessary or are the wrong drug.
Many people do not finish full-course.
More than half of all antibiotics manufactured in the US are routinely fed to farm animals to stimulate weight gain.

14. Vivian Vermillion
Vivian picked up a strain of antibiotic resistant E. coli at the Vet Hospital
This strain is resistant to six antibiotics!!!

15. Antibacterial Mustard Introduced by French’s
ROCHESTER, NY—In response to increasing American demand for tangier, more hygienic meals, condiment giant French's has introduced a new antibacterial mustard.

16. Toxic Chemicals
Dangerous chemicals are divided into two broad categories:
Hazardous - Dangerous
Flammable, explosive, irritant, sensitizer, acid, caustic.
Toxic - Poisonous
Can be general or very specific. Often harmful even in dilute concentrations.

17. Toxic Chemicals
Allergens - Substances that activate the immune system.
Antigens - Allergens that are recognized as foreign by white blood cells and stimulate the production of specific antibodies.
Other allergens act indirectly by binding to other materials so they become antigenic.

18. Toxic Chemicals Sick Building Syndrome
Headaches, allergies, and chronic fatigue caused by poorly ventilated indoor air contaminated by molds, carbon monoxide, nitrogen oxides, and other toxic chemicals.
Worker absenteeism and reduced productivity.
EPA estimates $60 billion annual loss.

19. Toxic Chemicals
Neurotoxins - Special class of metabolic poisons that specifically attack nerve cells.
Different types act in different ways.
Heavy Metals kill nerve cells.
Anesthetics and Chlorinated Hydrocarbons disrupt nerve cell membranes.
Organophosphates and Carbamates inhibit signal transmission between nerve cells.

20. Toxic Chemicals
Mutagens - Agents that damage or alter genetic material.
Radiation
Teratogens - Specifically cause abnormalities during embryonic growth and development.
Alcohol - Fetal Alcohol Syndrome
Carcinogens - Substances that cause cancer.
Cigarette smoke

21. US Age-Adjusted Cancer Death Rates

22. Endocrine Hormone Disrupters
Chemicals that disrupt normal endocrine hormone functions.
Hormones are chemicals released in blood by glands to regulate development and function of tissues and organs elsewhere in the body.
Environmental Estrogens and Androgens

23. Diet
Strong correlation between cardiovascular disease and the amount of salt and animal fat in an individual’s diet.
Highly-processed foods, fat, and smoke-cured, high nitrate meats appear to be associated with cancer.
Nearly 2/3 of all Americans are considered overweight.

24. DISTRIBUTION AND FATE OF TOXINS
Solubility - Chemicals are divided into two major groups:
Dissolve more readily in water.
Dissolve more readily in oil.
Water-soluble compounds move rapidly through the environment, and have ready access to most human cells.
Oil-soluble molecules generally need a carrier to move through the environment.

25. Bioaccumulation and Biomagnification
Cells have special mechanisms for Bioaccumulation - Selective absorption and storage.
Dilute toxins in the environment can build to dangerous levels inside cells and tissues.
Biomagnification - Toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level.

26. Sensitivity and Developmental Stage
Many factors help determine reaction of an individual to a given dose.
Age
Sex
Body Weight
Nutritional / Immunological Status
Repair Mechanisms

27. Persistence
Some chemical compounds are very unstable and degrade rapidly under most conditions, thus their concentrations decline quickly after release.
Others are more persistent.
Stability can cause problems as toxic effects may be stored for long period of time and spread to unintended victims.
(DDT)

28. Bioaccumulation

29. Chemical Interactions
Antagonistic Reaction - One material interferes with the effects, or stimulates the breakdown, of other chemicals.
Aluminum and phosphate ions form solid
Additive Reaction - Effects of each chemical are added to one another.
Xenoestrogens + estrogens
Synergistic Reaction - One substance multiplies the effect of the other.
Nitrate ion and phosphate ion

30. MECHANISMS FOR MINIMIZING TOXIC EFFECTS
Every material can be poisonous under certain conditions.
Most chemicals have a safe threshold under which their effects are insignificant.
Metabolic Degradation
In mammals, the liver is the primary site of detoxification of both natural and introduced poisons.

31. Excretion
Effects of waste products and environmental toxins reduced by eliminating via excretion.
Breathing
Kidneys
Urine

32. MEASURING TOXICITY Animal Testing
Most commonly used and widely accepted toxicity test is to expose a population of laboratory animals to measured doses of specific toxins.
Sensitivity differences pose a problem.
Dose Response Curves
LD50 - Dose at which 50% of the test population is sensitive (dies).

33. LD50

34. Population Sensitivity Variations

35. Acute vs. Chronic Effects
Acute Effects - Caused by a single exposure and result in an immediate health problem.
Chronic Effects - Long-lasting. Can be result of single large dose or repeated smaller doses.
Very difficult to assess specific health effects due to other factors.

36. RISK ASSESSMENT Factors influencing risk perception:
Rating risks based on agendas.
Most people have trouble with statistics.
Personal experiences can be misleading.
We have an exaggerated view of our abilities to control our fate.
News media sensationalizes rare events.
Irrational fears lead to overestimation of certain dangers.
Fear of the unknown.

37. Accepting Risks
Most people will tolerate a higher probability of occurrence of an event if the harm caused by that event is low.
Harm of greater severity is acceptable only at low levels of frequency.
EPA generally assumes 1 in 1 million is acceptable risk for environmental hazards.

39. ESTABLISHING PUBLIC POLICY
Biggest problem in making regulatory decisions is that we are usually exposed to many sources of harm, often unwillingly.
May not be reasonable to demand protection from every potentially harmful contaminant in our environment, no matter how small the risk.

40. ESTABLISHING PUBLIC POLICY
In setting standards for environmental toxins, need to consider:
Combined effects of different exposures.
Individual sensitivities within population.
Effects of chronic and acute exposures.

41. Food for Thought

42. From the Star - Tribune

43. Summary: Environmental Health Hazards Distribution and Fate of Toxins
Infectious Organisms
Emergent Diseases
Antibiotics and Pesticide Resistance
Toxic Chemicals
Distribution and Fate of Toxins
Minimizing Toxic Effects
Measuring Toxicity
Risk Assessment
Public Policy