Comprehensive study finds widespread mercury contamination across western North America

"Mercury is widespread in the environment, and under certain conditions poses a substantial threat to environmental health and natural resource conservation," says Collin Eagles-Smith, Ph.D., USGS ecologist and team lead.

The research team gathered decades of mercury data to examine patterns of mercury and methylmercury in numerous components of the western landscape. The results show where mercury occurs in western North America, how it moves through the environment, and the processes that influence its movement and transfer to aquatic food chains.

"This integrated effort provides critical information on mercury pathways to humans and wildlife that government regulators, lawmakers, and the public can use to make decisions," says David Evers, Ph.D., executive director and chief scientist of Biodiversity Research Institute and co-organizer of the project. "The Western mercury synthesis builds upon our Northeastern and Great Lakes regional efforts through which we collected and analyzed environmental mercury data that were often separated by sample type." The initiative for the western region of the continent continues BRI's efforts to assess environmental mercury deposition across North America in the Institute's series of studies called Mercury Connections.

Complete findings for the Western North America Mercury Synthesis (the Western Synthesis) have been published in a 2016 special issue of Science of The Total Environment: Mercury in Western North America -- Spatiotemporal Patterns, Biogeochemistry, Bioaccumulation, and Risks. Dr. Evers is co-author on five out of the 17 papers published in the Virtual Special Issue. All of the papers will also be published in the October issue of the journal.  

Papers co-authored by Dr. Evers include:

1. Mercury in western North America: A synthesis of environmental contamination, fluxes, bioaccumulation, and risk to fish and wildlife

2. Mercury risk to avian piscivores across western United States and Canada

3. Assessing potential health risks to fish and humans using mercury concentrations in inland fish from across western Canada and the United States

4. Avian mercury exposure and toxicological risk across western North America: A synthesis

5. Spatial and temporal patterns of mercury concentrations in freshwater fish across the Western United States and Canada

Summary of Key Findings and Implications (related to fish and wildlife) include:

● Methylmercury contamination in fish and birds is common in many areas throughout western North America, and large-scale ecological attributes, such as climate and land cover, are important factors influencing mercury contamination and availability to animals.

● Fish and birds in many areas were found to have mercury concentrations above levels associated with toxicity.

● Patterns of methylmercury, the most toxic form of mercury, exposure in fish and wildlife across western North America do not overlap with patterns of inorganic mercury on the landscape, indicating a disconnect between inorganic mercury distribution and exposure in fish and wildlife

● Land and water management activities can strongly influence how methylmercury is created and transferred to fish, wildlife, and humans.

● Effective management of environmental health risks associated with mercury goes beyond controlling sources of inorganic mercury, and would be improved with tools for controlling the production of methylmercury and its introduction to animal and human food sources

The Western Synthesis results suggest that effective management of environmental health risks associated with mercury goes beyond controlling sources of inorganic mercury, and could be improved by development of tools to control the production of methylmercury and its bioaccumulation through the food web, ultimately affecting animals and humans.