APES

• Get out Ecological Footprint Assignment

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 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)

Risk Assessment & Management

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 products3. 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

ToxicityDose-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 Risk1. 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.