Chapter 17 Environmental Hazards & Human Health

What Major Health Hazards Do We Face? We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices we make.

What is a hazard? Anything that can cause Injury, disease, death to humans Damage to personal or public property Deterioration or destruction of environment

Risks Are Usually Expressed as Probabilities Probability of suffering harm from a hazard Probability vs. Possibility Risk Assessment Process of using statistics to estimate how much harm a particular substance can cause to human health or environment Risk Management How to reduce risk (to what level and cost) Risk = probability of suffering harm from a hazard usually mathematical – example 1 in 250 or percentage 30%

Risk Assessment & Management

Leading Global Risk Factors

Types of Hazards Biological: Pathogen: an organism that causes disease in other organisms (bacteria, viruses, parasites, protozoa)

Types of Hazards 2. Chemical In air, water soil, food, and human-made products

Types of Hazards 3. Physical Earthquakes, floods, tornadoes, fire solar radiation

Types of Hazards 4. Cultural Smoking Working conditions Diet Drugs Drinking Assault Unsafe sex Poverty

Biological Hazards The most serious biological hazards we fade are infectious diseases Flu AIDS tuberculosis diarrheal diseases malaria.

Some Diseases Can Spread from One Person to Another Infectious disease Pathogen invades the body and multiplies Transmissible disease Contagious or communicable disease Infectious disease transmitted between people Flu, tuberculosis, measles Transmissible = type of infectious. Nontransmissible – develop slowly not spread – heart disease

Some Diseases Can Spread from One Person to Another Nontransmissible disease Not caused by living organisms Heart disease, most cancers, diabetes Since 1950, death from infectious diseases have declined due to Better health care Better sanitation Antibiotics Vaccines As age suffer from nontransmissible

Infectious Diseases Are Still Major Health Threats Infectious diseases spread through Air Water Food Body fluids Resistance of bacteria and insects to drugs and pesticides Epidemic = Large Scale Outbreak Pandemic =Global Epidemic Epidemic = large scale outbreak Global epidemic = pandemic Infectious disease and genetic resistance

Pathways for Infectious Diseases in Humans Figure 17.3: Science. There are a number of pathways on which infectious disease organisms can enter the human body. Question: Can you think of other pathways not shown here? Fig. 17-3, p. 439

Major Causes of Death from Infectious Diseases in the World, 2007

Three College Students Have Saved Thousands of Lives North Carolina State seniors Developed a device that can detect TB bacteria on a slide – glowing bacteria! Very useful in less-developed countries Pg 441

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 Oral rehydration = fluid replacement as a treatment for dehydration – drink water mixed with salt and sugar and continue to eat

What Types of Chemical Hazards Do We Face?

Toxic Chemicals Carcinogens Mutagens Teratogens 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

How Can Chemicals Affect Humans? Some natural and synthetic chemicals in the environment can weaken and harm Immune system Nervous system Neurotoxins: PCBs, arsenic, lead, some pesticides Endocrine system Endocrine: Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior

Hormones and Hormones Mimics or Blockers Hormonally active agents have similar shapes and bind to hormone receptors Figure 17.11: Hormones are molecules that act as messengers in the endocrine system to regulate various bodily processes, including reproduction, growth, and development. Each type of hormone has a unique molecular shape that allows it to attach to specially shaped receptors on the surface of, or inside, cells and to transmit its chemical message (left). Molecules of certain pesticides and other synthetic chemicals have shapes similar to those of natural hormones, allowing them to attach to the hormone molecules and disrupt the endocrine system in people and various other animals. These molecules are called hormonally active agents (HAAs). Because of the difficulty in determining the harmful effects of long-term exposure to low levels of HAAs, there is uncertainty about their effects on human health. Fig. 17-11, p. 449

How Can We Evaluate and Deal with Chemical Hazards? Scientists use live laboratory animals case reports of poisonings epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations. Pollution prevention to reduce exposure to potentially harmful chemicals.

Many Factors Determine the Harmful Health Effects of a Chemical Toxicology – study of harmful effects of chemicals on humans & other organisms Toxicity – measure of harmfulness of substance. Dependent on: Dose Age Genetic makeup Multiple chemical sensitivity (MCS) Solubility Persistence Bio magnification Toxi

Many Factors Determine the Harmful Health Effects of a Chemical Persistence Chemical’s resistance to breakdown Response Acute effect: immediate or rapid Chronic effect: permanent or long-lasting

Estimating Human Exposure to Chemicals and Measuring Their Effects

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity Dose-response curve: median lethal dose (LD50) - Acutely lethal to 50% of animals tested (14 days) Nonthreshold dose-response model Threshold dose-response model Nonthreshold = any dosage of toxic chemical causes harm that increases with dosage. Threshold = certain level of the chemical must be reached before any detectable harmful

Two Types of Dose-Response Curves Figure 17.14: Science. Scientist use two types of dose-response curves to help them estimate the toxicity of various chemicals. The linear and nonlinear curves in the left graph apply if even the smallest dosage of a chemical has a harmful effect that increases with the dosage. The curve on the right applies if a harmful effect occurs only when the dosage exceeds a certain threshold level. Which model is better for measuring the effects of a specific harmful agent is uncertain and controversial because of the difficulty in estimating the responses to very low dosages. Fig. 17-14, p. 454

Precautionary Principle With significant uncertainty about potential serious harm from chemicals or technologies, decision makers act to prevent harm to humans and the environment 2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs) 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

Health Risks Risk analysis Greatest health risks Risk assessment Risk management Risk communication Greatest health risks Poverty Gender Lifestyle choices

Number of Deaths per Year in the World from Various Causes Figure 17.16: Global outlook: Scientists have estimated the number of deaths per year in the world from various causes. Numbers in parentheses represent death tolls in terms of the number of fully loaded 200-passenger jet airplanes crashing every day of the year with no survivors. Because of the lack of media coverage of the largest annual causes of death and its sensational coverage of other causes of death, most people are misinformed and guided by irrational fears about the comparative levels of risk. Question: Which three of these items are most likely to shorten your life span? (Data from World Health Organization, 2007) Fig. 17-16, p. 458

Comparison of Risks People Face in Terms of Shorter Average Life Span Figure 17.17: Global outlook: This figure compares key risks that people can face, expressed in terms of an estimated shorter average life span (Concept 17-5). Excepting poverty and gender, the greatest risks people face come mostly from the lifestyle choices they make. These are merely generalized relative estimates. Individual responses to these risks differ because of factors such as genetic variation, family medical history, emotional makeup, stress, and social ties and support. Question: Which three of these factors are most likely to shorten your life span? (Data from Bernard L. Cohen) Fig. 17-17, p. 459

Annual Deaths in the U.S. from Tobacco Use and Other Causes Figure 17.19: Smoking is by far the nation’s leading cause of preventable death, causing more premature deaths each year than all the other categories in this figure combined. (Data from U.S. National Center for Health Statistics, Centers for Disease Control and Prevention, and U.S. Surgeon General) Fig. 17-19, p. 460

Estimating Risks from Technologies Is Not Easy System reliability (%) = Technological reliability (%) x Human reliability (%) To err is human... Example: 95% Technology x 75% Human = 71% System Reliability

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

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 Willing to accept = most people = 1 in 100,000 for env. hazards