Chapter 17 Environmental Hazards and Human Health

Risks Are Usually Expressed as Probabilities Risk Probability of suffering harm from a hazard Probability vs. possibility

Science: Risk Assessment and Risk Management Fig. 17-2, p. 437

We Face Many Types of Hazards Biological: – Pathogen: an organism that causes disease in other organisms Chemical Physical Cultural Lifestyle choices

Nitrates

Some Diseases Can Spread from One Person to Another Infectious disease Pathogen invades the body and multiplies Transmissible disease Infectious disease transmitted between people Flu, tuberculosis, measles Since 1950, death from infectious diseases have declined due to Better health care Better sanitation Antibiotics Vaccines

Infectious Diseases Are Still Major Health Threats Infectious diseases spread through Air Water Food Body fluids Epidemics and pandemics

Science: Pathways for Infectious Diseases in Humans Fig. 17-3, p. 439

Major Causes of Death from Infectious Diseases in the World, 2007 Fig. 17-4, p. 439

Genetic Resistance to Antibiotics Is Increasing Bacteria: rapid reproduction, easily spread Overuse of antibiotics Overuse of pesticides

Genetic Resistance to Antibiotics Is Increasing Methicillin-resistant Staphylococcus aureus (MRSA) Resistant to most antibiotics Symptoms of MRSA How will it be controlled?

The Growing Global Threat from Tuberculosis One in ten will become sick with TB 1.8 million deaths each year, primarily in less- developed countries Why is tuberculosis on the rise? Not enough screening and control programs Genetic resistance to a majority of effective antibiotics Person-to-person contact has increased AIDS individuals are very susceptible to TB

Lung Tissue Destroyed by Tuberculosis Fig. 17-5, p. 440

Viral Diseases Kill Large Numbers of People Influenza or flu virus #1 Killer HIV #2 Killer Hepatitis B virus (HBV) #3 Killer Emergent diseases: West Nile virus

Viral Diseases Kill Large Numbers of People Viruses that move form animals to humans West Nile virus Ecological medicine Reduce chances of infection: 1.Wash your hands 2.Avoid touching your face 3.Avoid sick people

Ecological Medicine: How Humans Get Infectious Diseases from Animals Human practices that encourage the spread of diseases from animals to humans Emerging infections HIV Avian flu Hepatitis B Lyme virus

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

Global HIV/AIDS Epidemic 25 million deaths, so far #1 killer globally of women 15-49 Most prevalent in sub-Saharan Africa Life expectancy dropped from 62 to 47 Alters age structure of population

Malaria — The Spread of a Deadly Parasite Malaria Caused by Plasmodium sp. carried by Anopheles mosquitoes Tropical and subtropical regions Spread Symptoms Malarial cycle

Malaria — The Spread of a Deadly Parasite Malaria on the rise since 1970 Drug resistant Plasmodium Insecticide resistant mosquitoes Clearing of tropical forests AIDS patients particularly vulnerable

Global Outlook: Distribution of Malaria Fig. 17-6, p. 444

A Boy in Brazil’s Amazon Sleeps Under an Insecticide- Treated Mosquito Net Fig. 17-7, p. 445

We Can Reduce the Incidence of Infectious Diseases Good news Vaccinations on the rise Oral rehydration therapy Bad news More money needed for medical research in developing countries

Solutions: Infectious Diseases Fig. 17-8, p. 445

Some Chemicals Can Cause Cancers, Mutations, and Birth Defects Toxic chemicals Carcinogens Chemicals, types of radiation, or certain viruses the cause or promote cancer Mutagens Chemicals or radiation that cause mutations or increase their frequency Teratogens Chemicals that cause harm or birth defects to a fetus or embryo

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. 17-9, p. 447

Some Chemicals May Affect Our Immune and Nervous Systems Some natural and synthetic chemicals in the environment can weaken and harm Immune system Nervous system Neurotoxins: PCBs, arsenic, lead, some pesticides Endocrine system

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 How are humans exposed? Inhalation: vaporized Hg or particulates Eating fish with high levels of methylmercury Eating high-fructose corn syrup

Mercury’s Toxic Effects Effects of Hg on humans Who is most at risk? Damage nervous system, kidneys, lungs Harm fetuses and cause birth defects Who is most at risk? Pregnant women 75% of exposure comes from eating fish

Solutions: Mercury Pollution Fig. 17-10, p. 449

Some Chemicals Affect the Human Endocrine System Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior Hormonally active agents have similar shapes and bind to hormone receptors Gender benders Thyroid disruptors BPA? Phthalates in plastics

Hormones and Hormones Mimics or Blockers Fig. 17-11, p. 449

Many Factors Determine the Harmful Health Effects of a Chemical Toxicology Toxicity dependent on Dose Age Genetic makeup Multiple chemical sensitivity (MCS) Solubility Persistence Biomagnification

Many Factors Determine the Harmful Health Effects of a Chemical Response Acute effect: immediate or rapid Chronic effect: permanent or long-lasting

Science: Estimating Human Exposure to Chemicals and Measuring Their Effects Fig. 17-12, p. 452

Protecting Children from Toxic Chemicals Analysis of umbilical cord blood: significance Infants and children more susceptible Eat, drink water, and breathe more per unit of body weight than adults Put their fingers in their mouths Less well-developed immune systems and body detoxification processes Fetal exposure may increase risk of autism, asthma, learning disorders

Scientists Use Live Lab Animals and Non-animal Tests to Estimate Toxicity Mice and rats Systems are similar to humans Small, and reproduce rapidly Is extrapolation to humans valid? Dose-response curve: median lethal dose (LD50) Nonthreshold dose-response model Threshold dose-response model

Scientists Use Live Lab Animals and Non-animal Tests to Estimate Toxicity More humane methods using animals Replace animals with other models Computer simulations Tissue culture and individual animal cells Chicken egg membranes What are the effects of mixtures of potentially toxic chemicals?

Hypothetical Dose-Response Curve Showing Determination of the LD50 Fig. 17-13, p. 453

Toxicity Ratings and Average Lethal Doses for Humans Table 17-1, p. 453

Science: Two Types of Dose-Response Curves Fig. 17-14, p. 454

There Are Other Ways to Estimate the Harmful Effects of Chemicals Case reports and epidemiological studies Limitations of epidemiological studies Too few people tested Length of time Can you link the result with the chemical? Cannot be used for new hazards

Are Trace Levels of Toxic Chemicals Harmful? Insufficient data for most chemicals We are all exposed to toxic chemicals Are the dangers increasing or are the tests just more sensitive?

Some Potentially Harmful Chemicals Found in Most Homes Fig. 17-15, p. 455

Why Do We Know So Little about the Harmful Effects of Chemicals? Severe limitations estimating toxicity levels and risks Only 2% of 100,000 chemicals have been adequately tested 99.5% of chemicals used in the United States are not supervised by government

Pollution Prevention and the Precautionary Principle Those introducing a new chemical or new technology would have to follow new strategies A new product is considered harmful until it can be proved to be safe Existing chemicals and technologies that appear to cause significant harm must be removed 2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs) 2007 REACH program in the European Union

The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices Risk analysis Risk assessment Risk management Risk communication Greatest health risks Poverty Gender Lifestyle choices

Global Outlook: Number of Deaths per Year in the World from Various Causes Fig. 17-16, p. 458

Comparison of Risks People Face in Terms of Shorter Average Life Span Fig. 17-17, p. 459

Death from Smoking Most preventable major cause of suffering and premature death Premature death of 5.4 million per year globally and 442,000 in the United States Could be linked to increased dementia and Alzheimer’s disease Nicotine: addictive Effects of passive smoking (secondhand smoke)

Case Study: Death from Smoking How to reduce smoking Taxes Classify and regulate nicotine Bans on smoking in public places Education

Normal Lung and Emphysema Lung Fig. 17-18, p. 459

Annual Deaths in the U.S. from Tobacco Use and Other Causes Fig. 17-19, p. 460

Most People Do a Poor Job of Evaluating Risks Fear Degree of control Whether a risk is catastrophic or chronic Optimism bias Want instant gratification without thinking of future harm

The Probability of Suffering Harm from Various Hazards Cause of Death Heart Disease Cancer Stroke Accidental Injury Motor Vehicle Accident* Intentional Self-harm (suicide) Falling Down Assault by Firearm Fire or Smoke Natural Forces (heat, cold, storms, quakes, etc.) Electrocution* Drowning Air Travel Accident* Flood* (included also in Natural Forces above) Legal Execution Tornado* (included also in Natural Forces above) Lightning Strike (included also in Natural Forces above) Snake, Bee or other Venomous Bite or Sting* Earthquake (included also in Natural Forces above) Dog Attack Asteroid Impact* Tsunami* Fireworks Discharge Lifetime Odds 1-in-5 1-in-7 1-in-23 1-in-36 1-in-100 1-in-121 1-in-246 1-in-325 1-in-1,116 1-in-3,357 1-in-5,000 1-in-8,942 1-in-20,000 1-in-30,000 1-in-58,618 1-in-60,000 1-in-83,930 1-in-100,000 1-in-131,890 1-in-147,717 1-in-200,000** 1-in-500,000 1-in-615,488 http://www.livescience.com/environment/050106_odds_of_dying.html

Several Principles Can Help Us to Evaluate and Reduce Risk Compare risks Determine how much you are willing to accept Determine the actual risk involved Concentrate on evaluating and carefully making important lifestyle choices

Three Big Ideas We face significant hazards from infectious diseases, malaria, and tuberculosis, and from exposure to chemicals that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems. Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention.

Three Big Ideas 3. Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.