USING SCIENCE TO ADDRESS ENVIRONMENTAL PROBLEMS Chapter 2

Scientific Method General steps followed Purpose Hypothesis (If…. then…) Procedure Data collection Analysis Conclusion

Scientific Method continued Variables Independent (X axis) Dependent (Y axis) Controls Constants

Feedback Loops Positive Feedback: continues or increases

Feedback Loops Continued Negative Feedback Loop: Corrective Process Example: Body Temperature Control Excess temperature Perceived by the Brain Sweat production By skin Heat loss from air Causes cooling of skin Heat from the sun

Gaia Hypothesis First formulated in the 1960s during his work for NASA on methods of detecting life on Mars, Dr. James Lovelock named this self-regulating living system the Gaia Hypothesis after the Greek goddess, using the suggestion of novelist William Golding, who lived in the same village as Lovelock at the time. According to Lovelock, Gaia is: A complex entity involving the Earth’s biosphere, atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet.

Risks Assessment ◦ What is a risk? ◦ Table 2.1 ◦ What is risk Assessment? ◦ Fours steps of Risk Assessment for Adverse Health Effects ◦ Which is scarier – risk we can control or the ones we can’t???

What is the probability of a Risk? 0 = No Risk 1 = Risk Closer to 0 the better = 1 in 1 million chance ChemicalLD 50 (mg/kg) Cocaine17.5 Nicotine60 Caffeine200.0

Toxicology The study of chemicals with adverse effects on health. Terms to know: toxicants dose response Acute toxicity vs. chronic toxicity

Toxicology continued lethal dose – 50% (LD 50 ) (die) ◦ usually reported in mg of chemical toxicant per kg of body weight mg/kg ◦ the smaller the LD 50, the more toxic the chemical ◦ the greater the LD 50, the less toxic the chemical ◦ Table 2.3

Toxicology continued Effective dose-50% (ED 50 ) ◦ show response under study ◦ dose-response curve ◦ threshold ◦ Figure 2.4

Hypothetical Dose-Response Curves No Threshold Level Threshold Level Dose Harmful effect

LD 50 Curve

Percent of Population Showing Response

The concentration of DDT in the fatty tissues of organisms in a food chain.

Chemical Interaction Antagonistic interaction: reduce their harmful effects or those of others Example: Vitamin A and E reduce the effect of cancer treatments Synergistic interaction: increased harmful effect Example: Nitrogen oxide and ground level ozone react with allergens to increase the frequency and severity of asthma attacks

Chemical Hazards Mutagens: cause random mutations Example: sickle cell, hemophilia Teratogens: cause birth defects while embryo is developing Carcinogens: promote growth of malignant tumors Neurotoxins: attack nerve cells Examples: DDT, metals such as Pb, Hg, A

Chemical Hazards continued Hormone disrupters (endocrine disrupters): control sexual reproduction, growth, development, behavior Examples: dioxin (unwanted byproduct when chlorine containing compounds are incinerated), lead, mercury, PCB, some plastics, some pesticides. Affect the reproduction of fish, birds, reptiles, and mammals.

Natural Hormone and Human-made Hormone Behavior

Ecological Risk Assessment Environmental Stressors Precautionary Principle Cost – Benefit Analysis of Risk of Ecological Risk Five steps in addressing an environmental problem: 1. Scientific assessment 2. Risk analysis 3. Public education and involvement 4. Political action 5. Evaluation

Review: Which value represents the most substantial risk? What is the difference in a negative and a positive feedback loop? Easter Island is best described using what type of feedback (s)? Endocrine disrupters affect ……………?