Building a Dynamic Model Linking Mercury Emission Regulations to Risk to Susceptible PopulationsEPA Grant Number: FP917117
Title: Building a Dynamic Model Linking Mercury Emission Regulations to Risk to Susceptible Populations
Investigators: Chan, Mary Caroline
Institution: University of Louisville
EPA Project Officer: Michaud, Jayne
Project Period: August 23, 2010 through August 22, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Human Health: Risk Assessment and Decision Making
To predict the results of regulatory decisions requires a broad range of knowledge that incorporates the interactions of physical, chemical, and biological systems with human exposures. When many systems interact, complex problems result and proposed solutions often lead to unexpected results. Dynamic models can be used to address such complex problems by breaking down the systems into their component parts and evaluating the relationships between these parts. This project will explore the reduction in human risk that can be achieved by simulating the environmental and human health impacts from various regulatory decision scenarios at the local level that link mercury emissions to human exposure from the consumption of contaminated fish.
Low levels of mercury exposure through fish consumption can cause nervous system deficits in the developing fetus. A major source of contamination of fish comes from emissions into the atmosphere, with subsequent deposition and transport of mercury into waterways. As a tool for decision makers to gain insight into this system, a model will be developed that tracks mercury from emission sources through environmental compartments and the food web to the exposure of susceptible populations.
A systems thinking approach will be used to model mercury dynamics downwind from emission sources. A dynamic model will be developed in three stages: human disposition, bioaccumulation through the food web, and environmental compartments. The human disposition sector will predict common biomarkers of methylmercury exposure from fish consumption for select populations. Calibration and validation will be from literature sources. Subsequently, biomagnification of mercury through the food web will forecast predatory fish tissue concentrations at chosen sites by calibrating and validating with site-specific data collected for regulatory purposes. Finally, the characterization of mercury from emission source, to deposition and movement through terrestrial and aquatic compartments will be simulated for these sites. The sub-models will be connected, linking local emissions to human exposure. Upon completion, the model can be used to determine if proposed regulatory scenarios are adequate in bringing fish tissue mercury levels into compliance with water quality standards, and more importantly, in reducing risk to susceptible populations.
The fully developed model will be used to evaluate various policy choices that may result in reduction in risk to specified populations. The distribution of maternal and fetal blood mercury levels will be compared to the level that the U.S. Environmental Protection Agency has determined to be protective of health. Regulators can decide if a proposed regulation is satisfactory by assessing the magnitude of decrease in the population at risk. Of particular importance is the time frame to reach the desired reduction in risk. Because certain environmental compartments act as sinks for mercury, particularly soil and sediment, a biphasic decline may occur after emission reduction policies are implemented as the mercury stored in soil and sediments may continue to release stored mercury before reaching steady state with the new loading scenario. A longer time to reach desired levels may suggest the need for larger reductions in emissions in order to reach reduction goals in a reasonable amount of time.
Potential to Further Environmental/Human Health Protection:
Efforts to regulate mercury emissions by the U.S. government have been unsuccessful as a consensus on legislation to address this problem has not been found. The stalemate at the federal level has led some states to consider implementing their own regulations to reduce mercury emissions. To do so, states must demonstrate that local reductions in emissions would result in reduced levels of mercury in local waterways with a subsequent reduction in risk to susceptible populations. The finished model will be a tool for states to project the impact of local regulations on local populations.