Chapter 18 Environmental Hazards and Human Health

RISKS AND HAZARDS  Risk is a measure of the likelihood that you will suffer harm from a hazard.  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.

The Pollution Within  NPR and David Duncan NPR and David Duncan NPR and David Duncan

RISK ASSESSMENT  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

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)  Epidemic-large-scale outbreak  Pandemic-global epidemic

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

Transmissible Disease  Pathway for infectious disease in humans. Figure 18-4

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.

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

Sporozoites penetrate liver and develop into merozoites Female mosquito bites infected human, ingesting blood that contains Plasmodium gametocytes Merozoites enter blood-stream and develop into gametocytes causing malaria and making infected person a new reservoir Female mosquito injects Plasmodium sporozoites into human host Plasmodium develops in mosquito Fig. 18-7, p. 423 Stepped Art

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).  West Nile Virus, Avian Flu, SARS, Hantavirus, Lyme Disease  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.

Teratogens  Examples: Rubella Rubella Mercury in water Mercury in water Fetal alcohol syndrome Fetal alcohol syndrome Crack babies Crack babies Methamphetamine Methamphetamine

Ocean Pollution: Mercury and Minamata Disease  Mercury has many industrial uses but is extremely toxic  A chemical plant released large quantities of mercury into Minamata Bay, Japan  Residents who ate highly contaminated fish suffered neurological disease and birth disorders bss.sfsu.edu/ehines/geog600/ Freshwater%20and%20ocean%20Pollution.ppt

Carcinogens  Causative agents Chemicals – Tobacco smoke Chemicals – Tobacco smoke Radiation – Pilots and cosmic radiation Radiation – Pilots and cosmic radiation Viruses – HPV and cervical cancer Viruses – HPV and cervical cancer Texas Governor mandated vaccination of all School females with Merck’s HPV vaccineTexas Governor mandated vaccination of all School females with Merck’s HPV vaccine  Promote growth of malignant tumors

Carcinogens  Latent Period Long time lapse between exposure Long time lapse between exposure SmokingSmoking EatingEating Lifestyle choices – laying in sunLifestyle choices – laying in sun Symptoms Symptoms Lung cancerLung cancer AIDSAIDS MelanomaMelanoma

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.

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 18-11

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.

Definition An LD50 represents the individual dose required to kill 50 percent of a population of test animals. It is an index determination of medicine and poison’s virulence. The lower the LD50 dose, the more toxic the pesticide.An LD50 represents the individual dose required to kill 50 percent of a population of test animals. It is an index determination of medicine and poison’s virulence. The lower the LD50 dose, the more toxic the pesticide. 19.8

Fig. 16.5, p Percentage of population killed by a given dose Dose (hypothetical units) LD 50

Laboratory Investigations Validity ChallengedValidity Challenged –Human physiology is different –Different species react different to same toxins Mice die with aspirinMice die with aspirin –Species can be selected depending on physiological area Pigs circulatory very similar to humansPigs circulatory very similar to humans

Toxicity ToxicityLD 50 Lethal DoseExamples Super < 0.01less than 1 drop dioxin, botulism mushrooms Extreme <5less than 7 drops heroin, nicotine Very drops to 1 tsp. morphine, codeine Toxic tsp. DDT, H 2 SO 4, Caffeine Moderate 500-5K1 oz.-1 pt. aspirin, wood alcohol Slightly5K-15K 1 pt. ethyl alcohol, soaps Non-Toxic>15K>1qt. water, table sugar (LD50 measured in mg/kg of body weight)

Hazardous Chemicals Why so little is known of toxicityWhy so little is known of toxicity –Only 10% of at least 75,000 commercial chemicals have been screened – ~ 2% determined to be carcinogen, teratogen or mutagen – >1000 new synthetic chemicals added per year – >99.5% of US commercial chemicals are NOT regulated

RISK ANALYSIS  Estimating risks from using many technologies is difficult due to unpredictability of human behavior, chance, and sabotage.  Reliability of a system is multiplicative: If a nuclear power plant is 95% reliable and human reliability is 75%, then the overall reliability is (0.95 X 0.75 = 0.71) 71%. If a nuclear power plant is 95% reliable and human reliability is 75%, then the overall reliability is (0.95 X 0.75 = 0.71) 71%.

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

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

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