CHAPTER TWO Using science to address environmental problems Tragedy of the Commons Garrett Hardin ( ) 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 Skip to LD50 Scientific Method Repeatability and repetitions and large sample size Control vs constants Variables Independent dependent 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 Assessing Environmental Problem Case Study: Lake Washington Large, freshwater pond Suburban sprawl in 1940s 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 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 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) Assessing Environmental Problem Case Study: Lake Washington Results! The Precautionary Principle Advocated by many environmental activists If new technology/chemical is suspected of harming human health (even if theres 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) 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 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. 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) 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 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 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. 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)