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Human - Ecosystem Interactions: The Case of Mercury
Citation:
MANGIS, D. R., C. D. KNIGHTES, AND D. A. VALLERO. Human - Ecosystem Interactions: The Case of Mercury. Presented at 17th Annual Conference of the International Society of Exposure Analysis, Durham, NC, October 14 - 18, 2007.
Impact/Purpose:
We will discuss how ecosystem exposure modeling studies completed for input into the US Clean Air Mercury Rule (CAMR) to evaluate the response of aquatic ecosystems to changes in mercury deposition will be used to improve human exposure modeling for methylmercury.
Description:
Human and ecosystem exposure studies evaluate exposure of sensitive and vulnerable populations. We will discuss how ecosystem exposure modeling studies completed for input into the US Clean Air Mercury Rule (CAMR) to evaluate the response of aquatic ecosystems to changes in mercury deposition will be used to improve human exposure modeling for methylmercury. Results from the five freshwater case studies showed that most freshwater systems will achieve 90% of the benefits of the mercury emissions reductions as the result of CAMR in 2-3 decades. Some systems may respond faster (5-10 years), and watershed dominated systems will likely take 50 years or more to respond. Attenuation of methylmercury after load reductions are calculated for northern pike and yellow perch by size class to illustrate body burdens across species and size classes that are cost prohibitive to sample effectively. The time lag in ecosystem response has a major effect on the benefits of regulations and how quickly these benefits are translated into human health benefits. By coupling ecosystem process models developed to evaluate the impacts of mercury reductions on sensitive ecosystems with atmospheric source models, and human consumption models, we can improve our human exposure risk analyses of mercury control scenarios, and better evaluate the impacts of local mercury hotspots to ecosystems and local fish consumptive human populations. The next step is to take this to the coastal and oceanic systems to determine how much reduction of mercury is needed to protect coastal and ocean ecosystems, and humans, since most mercury exposure comes from ocean fish consumption.