Chapter 17Human Health and Environmental Risks

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.

• 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

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

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

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

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.

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

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…

Epidemic/Pandemic

• Epidemic: rapid increase in a disease.• Pandemic: when an epidemic occurs

over a large geographic region.

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.

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.

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.

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.

LECTURE DAY 2Human Health and Environmental Risk

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.

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.

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.

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.)

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.

Smokingand

Sunbathing

Routes of Exposure

BioaccumulationBioaccumulation- an increased concentration of a

chemical within an organism over time

Solubility- how well a chemical can dissolve in a liquidSome 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.

Biomagnification Biomagnification-

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

PersistencePersistence- how long a chemical remains in the

environment

Scientists often measure persistence in its half-life.

LECTURE DAY 3Human Health and Environmental Risk

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:

Risk Analysis

Identify the hazard and magnitude.

2 types: qualitative and quantitative

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).

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

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.

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.

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.

Stockholm ConventionIn 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.

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.