What Major Health Hazards Do We Face? We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.
Risks Are Usually Expressed as Probabilities Risk 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)
Types of Hazards 1. Biological: Pathogen: an organism that causes disease in other organisms (bacteria, viruses, parasites, protozoa) 2. Chemical In air, water soil, food, and human-made products 3. Physical 4. Cultural 5. Lifestyle choices
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
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
Infectious Diseases Are Still Major Health Threats Infectious diseases spread through Air Water Food Body fluids Epidemics and pandemics Resistance of bacteria and insects to drugs and pesticides
Pathways for Infectious Diseases in Humans 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
What Types of Chemical Hazards Do We Face? There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine system.
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
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
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
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.
How Can We Evaluate and Deal with Chemical Hazards? Many health scientists call for much greater emphasis on pollution prevention to reduce our 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 Biomagnification
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 Mice and rats Systems are similar to humans Small, and reproduce rapidly Is extrapolation to humans valid?
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
Two Types of Dose-Response Curves Fig. 17-14, p. 454
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)
How Do We Perceive Risks and How Can We Avoid the Worst of Them? We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.
Health Risks Risk analysis Risk assessment Risk management Risk communication Greatest health risks Poverty Gender Lifestyle choices
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
Annual Deaths in the U.S. from Tobacco Use and Other Causes Fig. 17-19, p. 460
Estimating Risks from Technologies Is Not Easy System reliability (%) = Technological reliability (%) x Human reliability (%) Example: 95% Technology reliability x 75% human reliability = 71% system reliability To err is human…
Most People Do a Poor Job of Evaluating Risks 1. Fear 2. Degree of control 3. Whether a risk is catastrophic or chronic 4. Optimism bias 5. Want instant gratification without thinking of future harm
Several Principles Can Help Us to Evaluate and Reduce Risk 1. Compare risks 2. Determine how much you are willing to accept 3. Determine the actual risk involved 4. Concentrate on evaluating and carefully making important lifestyle choices
Three Big Ideas 1. 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. 2. 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.