Chapter 17 Environmental Hazards and Human Health

RISKS AND HAZARDS  Risk is a measure of the likelihood that you will suffer harm from a hazard. Risk = hazard x vulnerability Risk = hazard x vulnerability  We can suffer from: Biological hazards: from more than 1,400 pathogens. Biological hazards: from more than 1,400 pathogens. Chemical hazards: in air, water, soil, and food. Chemical hazards: in air, water, soil, and food. Physical hazards: such as fire, earthquake, volcanic eruption… Physical hazards: such as fire, earthquake, volcanic eruption… Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty. Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty.

BIOLOGICAL HAZARDS: DISEASE IN DEVELOPED AND DEVELOPING COUNTRIES  Diseases not caused by living organisms cannot spread from one person to another (nontransmissible disease), while those caused by living organisms such as bacteria and viruses can spread from person to person (transmissible or infectious)

Transmissible Disease  WHO estimates that each year the world’s seven deadliest infections kill 13.6 million people – most of them the poor in developing countries. Figure 18-5

Case Study: Growing Germ Resistance to Antibiotics  Rabidly producing infectious bacteria are becoming genetically resistant to widely used antibiotics due to: Genetic resistance: Spread of bacteria around the globe by humans, overuse of pesticides which produce pesticide resistant insects that carry bacteria. Genetic resistance: Spread of bacteria around the globe by humans, overuse of pesticides which produce pesticide resistant insects that carry bacteria. Overuse of antibiotics: A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily. Overuse of antibiotics: A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily.

Case Study: The Growing Global Threat from Tuberculosis  The highly infectious tuberculosis (TB) kills 1.7 million people per year and could kill 25 million people  Recent increases in TB are due to: Lack of TB screening and control programs especially in developing countries due to expenses. Lack of TB screening and control programs especially in developing countries due to expenses. Genetic resistance to the most effective antibiotics. Genetic resistance to the most effective antibiotics.

Viral Diseases  Flu, HIV, and hepatitis B viruses infect and kill many more people each year then highly publicized West Nile and SARS viruses. The influenza virus is the biggest killer virus worldwide. The influenza virus is the biggest killer virus worldwide. Pigs, chickens, ducks, and geese are the major reservoirs of flu. As they move from one species to another, they can mutate and exchange genetic material with other viruses.Pigs, chickens, ducks, and geese are the major reservoirs of flu. As they move from one species to another, they can mutate and exchange genetic material with other viruses.

Viral Diseases  HIV is the second biggest killer virus worldwide. Five major priorities to slow the spread of the disease are: Quickly reduce the number of new infections to prevent further spread. Quickly reduce the number of new infections to prevent further spread. Concentrate on groups in a society that are likely to spread the disease. Concentrate on groups in a society that are likely to spread the disease. Provide free HIV testing and pressure people to get tested. Provide free HIV testing and pressure people to get tested. Implement educational programs. Implement educational programs. Provide free or low-cost drugs to slow disease progress. Provide free or low-cost drugs to slow disease progress.

Core Case Study: The Global HIV/AIDS Epidemic  According to the World Health Organization (WHO), in 2005 about 42 million people worldwide (1.1 million in the U.S.) were infected with HIV. India is now AIDS capital of the world followed by South Africa.  There is no vaccine for HIV – if you get AIDS, you will eventually die from “it”.  Drugs help some infected people live longer, but only a tiny fraction can afford them.

Core Case Study: The Global HIV/AIDS Epidemic  AIDS has reduced the life expectancy of sub- Saharan Africa from 62 to 47 years – 40 years in the seven countries most severely affected by AIDS. Projected age structure of Botswana's population in Figure 18-2

Core Case Study: The Global HIV/AIDS Epidemic  The virus itself is not deadly, but it cripples the immune system, leaving the body susceptible to infections such as Kaposi’s sarcoma (above). Figure 18-1

Case Study: Malaria – Death by Mosquito  Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought. Figure 18-7

Case Study: Malaria – Death by Mosquito  Economists estimate that spending $2-3 billion on malaria treatment may save more than 1 million lives per year. Figure 18-6

 Spraying insides of homes with low concentrations of the pesticide DDT greatly reduces the number of malaria cases. Under international treaty enacted in 2002, DDT is being phased out in developing countries. Under international treaty enacted in 2002, DDT is being phased out in developing countries. Case Study: Malaria – Death by Mosquito

Fig. 18-8, p. 424 Solutions Infectious Diseases Increase research on tropical diseases and vaccines Reduce poverty Decrease malnutrition Improve drinking water quality Reduce unnecessary use of antibiotics Educate people to take all of an antibiotic prescription Reduce antibiotic use to promote livestock growth Careful hand washing by all medical personnel Immunize children against major viral diseases Oral rehydration for diarrhea victims Global campaign to reduce HIV/AIDS

Ecological Medicine and Infectious Diseases  Mostly because of human activities, infectious diseases are moving at increasing rates from one animal species to another (including humans).  Ecological (or conservation) medicine is devoted to tracking down these connections between wildlife and humans to determine ways to slow and prevent disease spread.

CHEMICAL HAZARDS  A toxic chemical can cause temporary or permanent harm or death. Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations in DNA. Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations in DNA. Teratogens are chemicals that cause harm or birth defects to a fetus or embryo. Teratogens are chemicals that cause harm or birth defects to a fetus or embryo. Carcinogens are chemicals or types of radiation that can cause or promote cancer. Carcinogens are chemicals or types of radiation that can cause or promote cancer.

CHEMICAL HAZARDS  A hazardous chemical can harm humans or other animals because it: Is flammable Is flammable Is explosive Is explosive An irritant An irritant Interferes with oxygen uptake Interferes with oxygen uptake Induce allergic reactions. Induce allergic reactions.

Effects of Chemicals on the Immune, Nervous, and Endocrine Systems  Long-term exposure to some chemicals at low doses may disrupt the body’s: Immune system: specialized cells and tissues that protect the body against disease and harmful substances. Immune system: specialized cells and tissues that protect the body against disease and harmful substances. Nervous system: brain, spinal cord, and peripheral nerves. Nervous system: brain, spinal cord, and peripheral nerves. Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream. Endocrine system: complex network of glands that release minute amounts of hormones into the bloodstream.

Effects of Chemicals on the Immune, Nervous, and Endocrine Systems  Molecules of certain synthetic chemicals have shapes similar to those of natural hormones and can adversely affect the endocrine system. Figure 18-9

Case Study: A Black Day in Bhopal, India  The world’s worst industrial accident occurred in 1984 at a pesticide plant in Bhopal, India. An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas. An explosion at Union Carbide pesticide plant in an underground storage tank released a large quantity of highly toxic methyl isocyanate (MIC) gas. 15,000-22,000 people died 15,000-22,000 people died Indian officials claim that simple upgrades could have prevented the tragedy. Indian officials claim that simple upgrades could have prevented the tragedy.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Factors determining the harm caused by exposure to a chemical include: The amount of exposure (dose). The amount of exposure (dose). The frequency of exposure. The frequency of exposure. The person who is exposed. The person who is exposed. The effectiveness of the body’s detoxification systems. The effectiveness of the body’s detoxification systems. One’s genetic makeup. One’s genetic makeup.  Check out suplement 22 in back of book to understand LD50.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation. Figure 18-10

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Estimating human exposure to chemicals and their effects is very difficult because of the many and often poorly understood variables involved. Figure Explain LD50

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Children are more susceptible to the effects of toxic substances because: Children breathe more air, drink more water, and eat more food per unit of body weight than adults. Children breathe more air, drink more water, and eat more food per unit of body weight than adults. They are exposed to toxins when they put their fingers or other objects in their mouths. They are exposed to toxins when they put their fingers or other objects in their mouths. Children usually have less well-developed immune systems and detoxification processes than adults. Children usually have less well-developed immune systems and detoxification processes than adults.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Under existing laws, most chemicals are considered innocent until proven guilty, and estimating their toxicity is difficult, uncertain, and expensive. Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S. Federal and state governments do not regulate about 99.5% of the commercially used chemicals in the U.S.

Protecting Children from Toxic Chemicals  The U.S. Environmental Protection Agency proposed that regulators should assume children have 10 times the exposure risk of adults to cancer-causing chemicals.  Some health scientists contend that regulators should assume a risk 100 times that of adults.

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Some scientists and health officials say that preliminary but not conclusive evidence that a chemical causes significant harm should spur preventive action (precautionary principle).  Manufacturers contend that wide-spread application of the precautionary principle would make it too expensive to introduce new chemicals and technologies.

Perceiving Risk  Most individuals evaluate the relative risk they face based on: Degree of control. Degree of control. Fear of unknown. Fear of unknown. Whether we voluntarily take the risk. Whether we voluntarily take the risk. Whether risk is catastrophic. Whether risk is catastrophic. Unfair distribution of risk. Unfair distribution of risk.  Sometimes misleading information, denial, and irrational fears can cloud judgment.

RISK ANALYSIS  Scientists have developed ways to evaluate and compare risks, decide how much risk is acceptable, and find affordable ways to reduce it. Figure 18-12

Becoming Better at Risk Analysis  We can carefully evaluate or tune out of the barrage of bad news covered in the media, compare risks, and concentrate on reducing personal risks over which we have some control. Figure 18-3 Discuss morbidity versus mortality

RISK ANALYSIS  Annual deaths in the U.S. from tobacco use and other causes in Figure 18-A

RISK ANALYSIS  Number of deaths per year in the world from various causes. Parentheses show deaths in terms of the number of fully loaded 400-passenger jumbo jets crashing every day of the year with no survivors. Figure 18-13

RISK ANALYSIS  Comparisons of risks people face expressed in terms of shorter average life span. Figure 18-14

Who Decides??  CDC, WHO, EPA  Precautionary Principle vs risk based policy  Problems with risk assessment Uncertainty Uncertainty Employed after a product or process is already in use Employed after a product or process is already in use Burden of proof of harm Burden of proof of harm  Precautionary (ex. Europe) Burden of proof on proponent of idea Burden of proof on proponent of idea Before it is used or in place Before it is used or in place