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Interpreting ecological effects; Ecological risk assessment
1.) biomonitoring - using biological systems to evaluate status of ecosystem
(a.) exposure monitoring looks for residues of toxicants in tissues
-- concentrations of toxicants at various trophic levels
-- DDT bioconcentration
-- example of PCBs in Lake Ontario
(b.) effects monitoring - evaluate status of the community
-- problem of effect/cause
-- specific effect (molecular) vs. effect at the community level
(c.) hormone disrupters - “effects” seen in the environment?
-- mink fed Lake Michigan fish
-- Florida alligators in a lake contaminated with chlorinated solvents
-- rats exposed to PCBs in utero
-- p-nonylphenol
-- Florida panther that feed on animals contaminated with DDT
-- indicative of a pattern linked to hormone disruptive chemicals
2.) Biomarkers - molecular and physiological indicators of exposure
(a.) markers used:
-- inhibition of acetylcholinesterase
-- induction of specific cytochromes P450
-- induction of stress proteins
-- induction of metallothioneins
-- chromosome breaks
-- elevation of PCK in macrophages
-- enzyme levels specific for tissues and indicative of damage
(b.) limitations of biomarker approach
3.) use of sentinel organisms
(a.) mussels helds in enclosures and exposed to water column
(b.) bird boxes in suspected contamination zone for generalist species
4.) analysis of community parameters
(a.) species abundance and diversity curves
5.) Risk assessment
(a.) approach to identifying hazards and evaluating associated risks
-- determine types of hazards
-- estimate probability of occurrence of each hazard
-- estmate how many organisms are likely to be exposed
-- estimate how many organisms will suffer harm
-- estimate seriousness of harm
(b.) perception of risk
(c.) quantification of risk
-- uncertain “science” at best
-- professional risk assessors - risks differ by 103-104
-- quantitative risk values provide a “safety” factor
(d.) despite its limitations, risk-benefit analysis is useful to:
-- organize available information
-- identify “significant” hazards
-- focus on areas that need more research
-- help decide how money for reducing risks should be allocated
-- stimulate public discussion for making informed decisions
(e.) public’s willingness to accept certain types of risks
-- risk of serious debilitating health problems or death from smoking
1 pack of cigarettes per day is 1 -in-300 by age 65
-- risk of serious debilitating health problems or death from
exposure to TCE in domestic water is 1-in-2 billion by age 65