U.S. Geological Survey - Environmental Health

Ecologically-Driven Exposure Pathways

Photograph showing white-faced ibis nesting
U.S. Geological Survey (USGS) scientists evaluated a nonlethal method to estimate mercury in the embryos of 23 bird species using mercury content in eggshells. Scientists collected eggs from 23 bird species, such as these white-faced ibis nesting at Bear River Migratory Bird Refuge, Great Salt Lake, Utah, at several locations around the Great Salt Lake, for the study. Photo Credit: Josh T. Ackerman, USGS.

Contaminant and pathogen exposure alone will not necessarily result in adverse health outcomes in animals or humans. There are numerous ecological and physiological pathways and processes that can alter the toxicity of environmental contaminants. U.S. Geological Survey (USGS) Scientists in the Ecological Pathways Team of the USGS Environmental Health Mission Area work to identify the environmental processes that affect the actual health risk to animals caused by environmental contaminants and pathogens. Understanding the complexities associated with the movement of contaminants and pathogens through the environment and their ultimate toxicity to humans and animals, requires broad scientific expertise in multiple key disciplines. No other federal or state agency has the complete set of scientific capabilities and geographic breadth to provide the needed composite findings and robust science. As such, USGS is in a unique position to address these issues because it is a world leader in expertise ranging from hydrology and geochemistry to biology and toxicology.

Current Science Questions and Activities

  • Does the maternal transfer of mercury to eggs differ among bird species and result in differential toxicity risk to offspring?
  • How does maternal transfer of mercury vary among fish species with different reproductive life-history strategies?
  • How are contaminant concentrations in an animal's body influenced by their annual life history strategies and specific physiological events such as molting, growth dynamics and metabolism?
  • Does selenium play a protective role in mercury toxicity to fish and wildlife?
  • Do multiple types and mixtures of chemicals present in the sediment and water of the Great Lakes' ecosystem have additive, synergistic, or antagonistic effects that impact the health of resident birds?
  • How have the concentrations of halogenated contaminants in osprey eggs from Delaware Bay and River changed since 2002?
  • Does contaminant exposure and productivity of ospreys exhibit geographic gradients and relationships along the Delaware Bay and River that are related to osprey health?
  • What is the molecular basis for species-specific sensitivity to mercury in birds?
  • What is the role of environmental media such as soil, water, and vegetation in host movement, pathogen/disease agent characteristics and life cycles, and other factors that affect wildlife health and disease such as Chronic Wasting Disease?
  • The wild-domestic bird interface is an important transmission nexus for avian influenza viruses. What are the key environmental factors that control the viability of virus shed by wild birds and what are the key environmental pathways of exposure and transmission of the virus in wild birds?
  • What are the environmental conditions that foster transmission of Lyme spirochetes, resulting in wildlife epizootics and human cases of Lyme disease?
  • What are the biologically mediated fluxes of stream metals to riparian food webs in the Colorado Mineral Belt?
  • What are the contaminant and resource fluxes from aquatic to terrestrial ecosystems?
  • What are the mechanisms and fates of metal transfer across metamorphosis?
  • Can a model predict the concentration of selenium in fish from dissolved selenium concentrations in water?
  • Over 90 percent of human exposure globally to toxic methylmercury is through the consumption of marine fish and shellfish. Can a tool be developed to help better understand the spatial and temporal trends of marine fish mercury levels, the drivers, and to anticipate future level in recognition of major anticipated changes globally for mercury use and emission rates?
  • Can census information collected as part of a study on human exposure from diet be used to assess the public health significance of mercury in fish consumed from the Great Lakes?
  • Working in collaboration with the Medical Schools at the University of Wisconsin-Madison and University of Nevada to secure human organ samples from cadavers (heart, liver, kidney, Sartorius, brain, and teeth if they have amalgam) can we determine the pharmacokinetics of mercury in the human body?
  • What are the major intrinsic and extrinsic drivers of mercury exposure and risk to humans and wildlife at a global scale?
  • What are the drivers of variation in mercury exposure of key transport biosentinels (dragonflies) from aquatic ecosystems in National Parks across the continental U.S. and Alaska?
  • How do mercury concentrations in aquatic food webs in protected lands vary throughout the continental U.S. and Alaska, and what are the key variables the influence mercury bioaccumulation?
  • Can wetland restoration and management practices reduce methylmercury bioaccumulation and subsequent health effects to aquatic organisms?
  • What are the drivers of mercury cycling, bioaccumulation, and risk to humans and biota in arid-land reservoirs of the western U.S.?
  • How does timber harvest influence the transport and bioaccumulation of mercury in headwater forests?
  • How do invasive species influence the timing and magnitude of mercury, selenium and cadmium uptake and bioaccumulation in native predators?
  • How do landscape alterations (for example levee breaches, the introduction of wetland deep open-water cells, and settling basins) affect wetland hydrology and the subsequent mobilization, transformation and bioaccumulation of contaminants of concern (for example mercury) into the food web of aquatic biota?

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Page Last Modified: April 18 2018