Environmental Hazards and Human Health Chapter 17

17-1 What Major Health Hazards Do We Face?  Concept 17-1 People face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.

Science: Risk Assessment and Risk Management Fig 17-3

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. Chemical hazards: in air, water, soil, and food. Physical hazards: such as fire, earthquake, volcanic eruption… Cultural hazards: such as smoking, poor diet, unsafe sex, drugs, unsafe working conditions, and poverty.

Using Risk Assessment (Benefit/Cost Analysis) 1.Benefits > Risks, then behavior or process should continue 2.Benefits < Risks, then behavior or process should not continue. Every behavior or process involves RISK.

17-2 What Types of Biological Hazards Do We Face?  Concept 17-2 In terms of death rates, the most serious infectious diseases are flu, AIDS, diarrheal diseases, malaria, and tuberculosis; most of these deaths occur in developing countries.

Core Case Study: The Global HIV/AIDS Epidemic  Acquired immune deficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV); many secondary infections  No vaccine to prevent or cure AIDS  Expensive drugs—live longer  25 Million deaths, so far; alter country’s age structure

Global Outlook: Worldwide, AIDS Is the Leading Cause of Death for Ages 15–49 Fig 17-2

Some Viral Diseases Kill Large Numbers of People  Global strategy to slow down the spread of HIV Reduce the number of new infections Concentrate on those most likely to spread HIV Free testing Education for prevention Provide free or low-cost drugs Research United Nations HIV/AIDS

Major Causes of Death in the World and in the United States in 2005 Fig 17-3

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. Methicillin-resistant Staphylococcus aureus (MRSA) Overuse of antibiotics: A 2000 study found that half of the antibiotics used to treat humans were prescribed unnecessarily.

Science: Pathways for Infectious Diseases in Humans Fig 17-5

The World’s Seven Deadliest Infectious Diseases Kill 12.5 Million People Fig 17-6

Malaria – Death by Mosquito  Malaria kills about 2 million people per year and has probably killed more than all of the wars ever fought.

Global Outlook: Distribution of Malaria

A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net

Infectious Disease Control  Here are some link to International and U.S. organizations that deal with disease control:  UNICEF UNICEF  WHO – World Health Organization WHO – World Health Organization  CDC – Center for Disease Control CDC – Center for Disease Control  Department of Health & Human Services Department of Health & Human Services  NIH – National Institute of Health NIH – National Institute of Health

Solutions: Infectious Diseases, Ways to Prevent or Reduce Their Occurrence Fig 17-10

17-3 What Types of Chemical Hazards Do We Face?  Concept 17-3 There is growing concern about chemicals that can cause birth defects and cancers and disrupt the human immune, nervous, and endocrine systems.

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. 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.

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

Case Study: PCBs Are Everywhere—A Legacy from the Past  Class of chlorine-containing compounds Very stable Nonflammable Break down slowly in the environment Travel long distances in the air Fat soluble Biomagnification Food chains and webs  Banned, but found everywhere

Potential Pathways on Which Toxic Chemicals Move Through the Environment Fig 17-10

Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems  Some natural and synthetic chemicals in the environment can weaken and harm Immune system Nervous system Endocrine system Hormonally active agents (HAAs) Gender benders Thyroid disrupters

Hormones and Hormones Mimics or Blockers Fig 17-12

Science Focus: Bisphenol A  Estrogen mimic  Found in many common products - Plastics  NIEHS link to info NIEHS link to info

Science Focus: Mercury’s Toxic Effects  Hg: teratogen and potent neurotoxin Once airborne, persistent and not degradable 1/3 from natural sources 2/3 from human activities Enters the food chain: biomagnification

Science: Cycling of Mercury in Aquatic Environments Fig 17-A

Fig. 17-B, p. 451 SOLUTIONS Mercury Pollution PreventionControl Phase out waste incinerationSharply reduce mercury emissions from coal-burning plants and incinerators Remove mercury from coal before it is burned Tax each unit of mercury emitted by coal-burning plants and incinerators Switch from coal to natural gas and renewable energy resources such as wind, solar cells, and hydrogen Require labels on all products containing mercury Convert coal to liquid or gaseous fuel Phase out use of mercury in batteries, TVs, compact fluorescent lightbulbs, and all other products unless they are recycled Collect and recycle mercury- containing electric switches, relays, and dry-cell batteries

17-4 How Can We Evaluate and Deal with Chemical Hazards?  Concept 17-4A Scientists use live laboratory animals, non-animal tests, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations.  Concept 17-4B Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful candidates.

Many Factors Determine the Harmful Health Effects of a Chemical  Toxicity dependent on Dose Frequency of exposure Age Genetic makeup = the effectiveness of the body’s detoxification systems Multiple chemical sensitivity (MCS) Solubility and persistence of the chemical Biomagnification  Response Acute effect Chronic effect

TOXICOLOGY: ASSESSING CHEMICAL HAZARDS  Typical variations in sensitivity to a toxic chemical within a population, mostly because of genetic variation.

Science: Estimating Human Exposure to Chemicals and Measuring Their Effects Fig 17-13

Hypothetical Dose-Response Curve Showing Determination of the LD50 Fig 17-14

Toxicity Ratings and Average Lethal Doses for Humans

Science: Two Types of Dose- Response Curves Fig 17-15

Toxicity Ratings LD50 is the dose at which 50% of the population die Household product risk Dept Health & Human Services

Toxicology and Risk Assessment Careers  Society of Toxicology Society of Toxicology  Environmental Health and Toxicology Environmental Health and Toxicology  EPA – risk assessment EPA – risk assessment  Risk Management Careers Risk Management Careers

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.

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.

Some Potentially Harmful Chemicals Found in Most Homes Fig 17-16

17-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them?  Concept 17-5 We can reduce the major risks we face if we become informed, think critically about risks, and make careful choices.

Comparative Risk Analysis: Most Serious Ecological and Health Problems

Fig , p. 461 Stepped Art

Global Outlook: Number of Deaths per Year in the World from Various Causes Fig 17-18

Comparison of Risks People Face in Terms of Shorter Average Life Span

Annual Deaths in the U.S. from Tobacco Use and Other Causes in 2004 Fig 17-20

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%.

Characteristics of Risk (Factors on Right Increase Perception of Riskiness) Voluntary Driving a car Involuntary Breathing air polluted by a factory Natural Radon in basement Man Made Industrial chemicals Familiar Household cleaners Exotic Genetically engineered organism Chronic Routine small releases of chemicals from a facility Catastrophic (Acute) Large release of chlorine gas from a plant Visible Benefits Dying hair No Visible Benefits Incinerator effluents Controlled by Individuals Driving Controlled by others Industrial pollution FairUnfair

Using Risk Assessment (Benefit/Cost Analysis) 1.Benefits > Risks, then behavior or process should continue 2.Benefits < Risks, then behavior or process should not continue.

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. Fig 17-3