1. CHAPTER TWO Using science to address environmental problems

2. Tragedy of the Commons  Garrett Hardin (1915-2003)  Solving Environmental Problems is result of struggle between:  Short term welfare  Long term environmental stability and societal welfare  Garrett used Common Pastureland in medieval Europe to illustrate the struggle  Global commons – parts of the environment available to all, but owned by none (shared resources)  Outcomes: private ownership, government ownership/regulation

3.  Skip to LD50

4. Scientific Method  Repeatability and repetitions and large sample size  Control vs constants  Variables  Independent  dependent

5. Five Stages to Addressing An Environmental Problem  Five steps are idealistic  Real life is rarely so neat  Following Slides are Case Study Using the Five Stages

6. Assessing Environmental Problem Case Study: Lake Washington  Large, freshwater pond  Suburban sprawl in 1940’s  10 new sewage treatment plants dumped effluent (containing phosphorous) into lake  Effect = excessive cyanobacteria growth which when decomposing consume oxygen. No more oxygen for fish. Sad.   Called eutrophication

7. Assessing Environmental Problem Case Study: Lake Washington  Scientific Assessment  Aquatic wildlife assessment done in 1933 was compared to the 1950 assessment  Hypothesized treated sewage was introducing high nutrients causing growth of cyanobacteria  Risk Analysis  After analyzing many choices, chose new location (marine water) and greater treatment for sewage to decrease nutrients in effluent

8. Assessing Environmental Problem Case Study: Lake Washington  Public Education/Involvement  Educated public on why changes were necessary to convince sanitation authorities.  Political Action  Difficult to organize sewage disposal in so many municipalities  Changes were not made until 1963!  Evaluation  Cyanobacteria slowly decreased until 1975 (gone)

9. Assessing Environmental Problem Case Study: Lake Washington  Results!

10. The Precautionary Principle  Advocated by many environmental activists  If new technology/chemical is suspected of harming human health (even if there’s scientific uncertainty) – it should not be introduced until proven that  risks are small  the benefits outweigh the risks  Places burden of proof on the manufacturer and not waiting until people get ill. (absolute proof is impossible)

11.  opposing view:  Scientists fear decisions will be made without the input of science  Could reduce trade  Limit technological innovations  Examples: European ban on US beef due to use of growth hormones (or to protect their own beef industry); use of genetically modified food

12. How do we know if a chemical is toxic to humans?  Acute vs chronic toxicity  Acute toxicity (determined by using lab animals and predicting the human response):  LD 50 (lethal dose – 50%): the dose that is lethal to 50% of test animals (mg of toxicant per kg body weight)  ED 50 (effective dose – 50%): the dose that causes 50% of a population to have the response tested.

14. Is the dose that is safe for adults always safe for children?  NO – why?  Children are smaller  Substance with LD50 of 100mg/kg and an adult weighing 68 kg: 100 mg/kg (68 kg) = 6800 mg (2 teaspoons)  Substance with LD50 of 100mg/kg and a child weighing 11.3 kg 100 mg/kg (11.3 kg) = 1130 mg (1/4 teaspoon)

15. How scientists figure out if substance is cancer-causing or toxic in other ways:  Expose rats to extremely large doses and see effects.  If cancer-causing then scientist work backwards from the dose and amount of cancer to determine maximum safe levels for humans  Positives: proves if substance is safe  Problems: different species and may respond differently, body may respond differently when exposed to low levels

16. Chemical mixtures  Scientists assume chemicals are additive to assess risk.  BUT – some chemical mixtures are synergistic and some are antagonistic  Examples of mixtures: air, water, food, cigarette smoke, vehicle exhaust

17. Human impacts on the environment may increase disease  Malaria – transmit parasitic protozoa by mosquitoes. Water is needed for breeding  Human contact with disease causing organisms may increase:  Newly cleared forests form water pools  Drainage ditches built alongside roads  Areas away from tropics have warmed (global warming) and some populations of mosquitoes have expanded their territory.

18. Assessing risk to environment  Complex: many different portions of the environment may be affected  Cost-benefit analysis: how much will it cost to fix and how beneficial will the results be?  Positives:  Allows governments to tackle problems with lowest cost and most benefit  Negatives:  Ineffective if data is bad; risk assessment based on assumptions  How do you put a price tag on human health? (if something is expensive but improves health)