1. Chapter 17 Human Health and Environmental Risks

2. Norco, Louisiana
Old Diamond district: Four city blocks between A Shell Oil chemical plant and a refinery. Minority neighborhood.
1973-pipeline explosion: 2 dead
1988-refinery accident 7 workers killed, 70 mill. Kg of toxic chemicals released into air, nearly 1/3 of all children suffered asthma, many cases of birth defects and cancers after.

3. 1989- middle school teacher Margie Richard takes action.
Set up a “bucket brigade” to collect air samples.
Fight against shell withstood large resistance from the company. 13 year fight.
2002- Shell pays $5 million to community for development, buys resident houses at fair market price, committed to reducing air emissions by 30%
2007- pays an addition $6.5 million in penalties to the state for violation of air pollution regulations

4. Three categories of human health risks
Physical
Natural disasters, excessive exposure to UV radiation, exposure to radioactive substances like radon.
Biological
Risks associated with disease
Chemical
Exposure to chemicals ranging from naturally occurring arsenic to synthetic chemicals and pesticides

5. Biological risk causes the greatest number of deaths: (both greens, red & purple sections)

6. Biological Risks
Infectious diseases- those caused by infectious agents, known as pathogens.
The pathogens that cause most infectious diseases are viruses, bacteria, fungi, protists, and a group of parasitic worms called helminths.
Examples: pneumonia and venereal diseases

7. Biological Risks All diseases fall into two categories:
Chronic disease- slowly impairs the functioning of a person’s body.
Acute diseases- rapidly impair the functioning of a person’s body.

8. Substantial difference in the top 10 risk factors for death/chronic disease between low-income and high-income countries…

9. Methods of Transmission
Environmental Scientists are interested in diseases caused by environmental factors (not genetic diseases)
Many pathways to infecting humans, including transmission of pathogens from other humans, other animals, the food we eat, the water we drink…

10. Epidemic/Pandemic Epidemic: rapid increase in a disease.
Pandemic: when an epidemic occurs over a large geographic region.

11. Historical Diseases Plague Carried by fleas found on rodents
Modern antibiotics highly effective.
Malaria
Transmitted by several species of plasmodium.
One cycle of life in mosquito, one cycle in humans.
1951- malaria eradicated from US. Traditional approach: DDT.
Tuberculosis
Caused by bacterium M. tuberculosis . Primarily affects lungs
Can persist in air for several hours, may be infected without signs or symptoms
Drug resistant strains are a problem.

12. Emergent Diseases
Infectious diseases that have not been seen within the last 20 years.
Many of these new diseases have unexpectedly jumped from one species to another through mutation.
HIV/AIDS: origin remained a mystery until 2006 when the original host was found to be chimpanzees. Antiviral drugs have held it in check where available.
Ebola: Caused by ebola virus. Originated in the Congo. Kills most that are infected with it.
Mad Cow Disease: Damages cow’s nervous system. Small beneficial proteins called prions mutate into deadly proteins that act as pathogens. Passed from cow to cow when fed with ground up cows infected with disease as an extra source of protein. Passed to humans who eat infected cows.

13. Bird Flu: Avian influenza. Caused by H1N1
Bird Flu: Avian influenza. Caused by H1N1. similar to an Asian virus known as H5N1 that had jumped from bird to human. Because there is no evolutionary history for humans, they tend not to have defenses against it.
West Nile Virus: Transmitted among birds via mosquitoes. Increasing reports that horses and humans could be infected if bitten by the mosquitoes.

14. Five categories of harmful chemicals:
Chemical Risks
Five categories of harmful chemicals:
Neurotoxins- chemicals that disrupt the nervous system. Insects and other invertebrates are extremely sensitive to neurotoxins. Lead, Mercury.
Carcinogens- chemicals that cause cancer. Interrupt the normal metabolic function of a cell, damaging the genetic material. Carcinogens that damage cells are called mutagens
Teratogens- chemicals that interfere with the normal development of embryos or fetuses. Modern teratogen: Alcohol.
Allergens- chemicals that cause allergic reactions. Chemicals naturally found in Milk, Peanuts, and drugs such as penicillin and codeine.
Endocrine disruptors- chemicals that interfere with the normal functioning of hormones in an animal’s body. Scientists are finding many fish, reptiles, and amphibians that are male but have low sperm counts or are producing eggs and sperm.

15. Human Health and Environmental Risk
Lecture day 2

16. Dose-Response Studies
LD50- lethal dose that kills 50% of the individuals
Short duration (1-4 days) called acute studies.
The dose at which an effect starts to be seen is called the threshold.
ED50- effective dose that causes 50% of the animals to display the harmful but nonlethal effect
Mice and rats used to represent mammals, pigeons and quail used for birds, trout for fish, water fleas for invertebrates.

18. Regulation of testing
In the US the effects of chemicals on humans and wildlife are regulated by the EPA.
Toxic Substances Control Act 1976 (excludes food, cosmetics, and pesticides).
Pesticides are regulated under the Federal Insecticide, Fungicide, and Rodenticide Act of 1996
Since no chemical can be tested on every animal, scientists have devised the system of using representatives of those species.
Reptiles and amphibians have not been species of interest in the past and so aquatic reptiles and amphibians have been represented by fish and terrestrial by bird tests.

19. Determining the concentrations
To determine the concentration which will cause no harm, scientists use the LD50 value divided by 10.
For humans, they use the LD50 value (obtained from mice and rats) divided by 1000.

20. Chronic studies For studies lasting longer than a few days.
Retrospective studies: monitor people who have been exposed to a chemical at some time in their past.
Prospective studies: monitors people who might become exposed to harmful chemicals in the future. (select 1000 people and follow them for 40 years monitoring their tobacco, alcohol, etc. and future health affects.)

21. Smoking and Sunbathing
Synergistic interactions- when two risks come together and cause more harm that one would. For example, the health impact of a carcinogen such as asbestos can be much higher if an individual also smokes tobacco.
Smoking
and
Sunbathing

22. Routes of Exposure

23. Bioaccumulation
Bioaccumulation- an increased concentration of a chemical within an organism over time Solubility- how well a chemical can dissolve in a liquid Some are water soluble: pervasive in ground water and surface water. Some are oil-soluble: pervasive in soils (especially benthic soils). Readily stored in the body fat of animals.

24. Biomagnification
Biomagnification- the increase in a chemical concentration in animal tissues as the chemical moves up the food chain.

25. Scientists often measure persistence in its half-life.
Persistence- how long a chemical remains in the environment
Scientists often measure persistence in its half-life.

26. Human Health and Environmental Risk
Lecture day 3

27. Environmental Hazard
Anything in our environment that can potentially cause harm.
Pollutants, human activities, natural catastrophes.
When assessing risk of different environmental hazards, regulatory agencies, environmental scientists, and policy makers usually follow a three step process:

28. Risk Analysis Identify the hazard and magnitude.
2 types: qualitative and quantitative

29. Qualitative Risk Assessment
We tend to categorize our decisions based on having low, medium, or high risk.
Based on judgments rather than actual data.
These judgments often do not match the actual risk.
Lack of familiarity, extent to which the act is Voluntary, public impression (big events imprint in our minds), overselling of safety, morality, control, fairness (knowing who benefits).

31. Quantitative Risk Assessment
The approach to conducting a quantitative risk assessment is:
Risk= probability of being exposed to a hazard X probability of being harmed if exposed

32. Risk Acceptance The level of risk that can be tolerated.
Personal preferences always play a part in complicating the decision. Environmental scientists, policy makers, economists, etc. help to weigh the options objectively.

33. Risk Management
Seeks to balance possible harm against other considerations.
Integrates the scientific data and the acceptable levels of risk with a number of additional factors including economic, social, ethical, and political issues.
Regulatory activity usually carried out by local, national, or international government agencies.

34. Standards of Risk
Innocent-until-proven-guilty principle: gets chemicals to public faster but may introduce a potential hazard to fast and therefore cause harm to the public or environment.
US policy.
Precautionary principle: when a hazard is plausible but not yet certain. Delays the chemical getting to the public in a timely manor. Cost manufacturer more money. Many of the chemicals are never researched or found because the time and money investment is not worth the time.
Policy used by the European Union.

35. Stockholm Convention
In 2001, a group of 127 nations gathered in Stockholm, Sweden, to reach an agreement on restricting the global use of some chemicals
12 chemicals were to be banned, phased out, or
reduced
These include DDT, PCBs, and certain chemicals
that are by-products of manufacturing processes.
All are endocrine disruptors.
In 2009, 9 additional chemicals were added to the original list of 12 and several more have been suggested.

36. REACH
2007, the 27 nations of the European Union put into effect an agreement on how chemicals should be regulated within the European Union. Registration, evaluation, authorization, and restriction of chemicals.
Embraces the precautionary principle.