Chapter 2

Using Science to Address Environmental Problems

Super Topic 1: The Scientific Method

*Never PROVES anything, only removes INCORRECT POSSIBILITIES

1. Recognize Question2. Research what is already known3. Develop a hypothesis to explain problem4. Design & Perform a testable experiment5. Analyze & Interpret data6. Reach conclusions & report own data

Super Topic 2: Experimental Controls

1. Variable: a FACTOR that influences a processa. Independent: WHAT YOU’RE TESTING EFFECTS OF

b. Dependent: WHAT IS BEING MEASURED (the results)

c. Controls: WHAT REMAINS CONSTANT

2. Groups: a. Control: variable that is NOT ALTEREDb. Experimental: Independent variable is ALTERED IN A

KNOWN WAY

Super Topic 3: Types of Reasoning

1. Inductive Reasoning: SPECIFIC TO GENERALa. Asks, “What does the grouped information have in

common?”b. Can produce NEW KNOWLEDGE, but is prone to

ERRORc. Ex. “Gold is a metal that is heavier than water

Iron is a metal that is heavier than water Silver is a metal that is heavier than water.”

Conclusion: All metals are heavier than water.

Super Topic 3: Types of Reasoning (cont.)

2. Deductive Reasoning: GENERAL TO SPECIFICa. Adds NO NEW knowledge, but makes relationships

more APPARENT

b. Helps determine the type of EXPERIMENT or OBSERVATION necessary to test a hypothesis

c. Example: General Rule: All birds have wings Specific Example: Robins are birds Deduction: All robins have wings.

3. Theories: Integrated explanations of NUMEROUS HYPOTHESES*There is no ABSOLUTE TRUTH in science, only varying degrees of UNCERTAINTY!

Deductive Reasoning v. Inductive Reasoning

Super Topic 4: Risk & Risk Management

• Risk: PROBABILITY OF HARM• Risk Assessment: using STATISTICAL METHODS to

quantify the risk involved in a particular action so they can be COMPARED & CONTRASTED w/other risks.

• Risk Management: Determines whether a particular risk should be REDUCED or ELIMINATED, and if so, what should be done.– Considers the risk in terms of relevant POLITICAL,

SOCIAL, & ECONOMIC considerations

Super Topic 4: Risk Management (Cont.)

• Varying Views:A. If we have control, it’s no big deal even though the

risk is high (ie, a diet)B. If we don’t have control, it’s a huge deal (pesticide

residue) even though the risk is low (ie, DDT is a cheap pesticide)

Super Topic 4: Risk Assessment (cont.)

Four Steps of Risk Assessment:1. HAZARD IDENTIFICATION: does exposure cause an

increased likelihood of adverse health effect?2. DOSE-RESPONSE ASSESSMENT: the relationship b/w

amount of exposure and the seriousness of the health effect

3. EXPOSURE ASSESSMENT: how much, how often, how long is the exposure?

4. RISK CHARACTERIZATION: what is the probability of an individual population having an adverse health effect?

The Steps of Risk Assessment

Super Topic 5: Determining the Health Effects of Environmental Pollutants

• TOXICANTS: chemicals w/adverse health effects

• TOXICOLOGY: the study of toxicants• Two types of effects of toxicants on living

organisms:1. ACUTE: Immediately or closely following

exposure (ie, dizziness & and nausea)2. CHRONIC: Long-term effects such as damage to

vital organs (ie, kidney & lung damage)

Super Topic 5 (cont.)

Dose and Response:1. Lethal Dose- 50%- (LD50): CAUSES DEATH IN 50% OF

TEST POPULATIONa. LD50 and toxicity are INVERSELY related:

As LD50 , toxicity (and vice versa)

2. Sub-Lethal Dose: causes harm, not death3. Threshold: maximum dose w/no measurable effect

a. Any dose less than threshold is safe4. Effective Dose- 50% (LD50): causes a specific reaction

within the BULK OF THE POPULATION

Super Topic 5 (cont.)

Super Topic 6: Cancer-Causing Substances & Risk Assessment of Chemical Mixtures

• CARCINOGEN: cancer causing substance • How to determine if chemicals are the cause– EPIDEMIOLOGICAL evidence of carcinogen

exposure– ANIMAL TESTING: very controversial and not

effective (animals react differently than humans)• Risk Assessment of Chemical Mixtures:

toxicology studies are usually performed on ONE CHEMICAL, not mixtures

Super Topic 6 (cont.)

• Chemicals can interact in 3 ways:1. Additive: CHEMICALS ADD UP(1+1=2)2. Synergistic: GREATER COMBINED EFFECT (1+1=3)3. Antagonistic: SMALLER COMBINED EFFECT

(1+1=1)*Additive approach sometimes over/under

estimates the actual risk, but is still most accurate

Super Topic 7: Ecological Risk Assessment

Ecological Risk Assessment: “Quantifying the PROBABLE EFFECTS of a wide range of human activities on

ECOSYSTEMS.”Analysis of ERA is difficult because…1. Many effects may be FELT ON A WIDE SCALE 2. Environmental Stressors like HUMAN INDUCED CHANGES3. Ecological efforts are INCOMPLETELY

UNDERSTOOD/HARD TO MEASURE4. Scientific knowledge in environmental decision making is

filled with UNCERTAINTY

Super Topic 7 (cont.)

• Example: Snake River (Idaho)– Provided irrigation for agriculture1. Human-made changes: DAMS FOR ELECTRICITY2. Caused: NUTRIENT ENRICHMENT, WATER

TEMPERATURES, WATER FLOW3. Effects: algae and aquatic blooms FISH

POPULATION 4. Ecological risk assessment helps sets priorities to

meet the common goal of managing & protecting biological communities in the Snake River watershed.