Environmental Epidemiology in Latin America: Impacts of Artisanal Gold Mining in the Peruvian Amazon (2018-2019)


In 2013, Bass Connections helped launch one of the largest and most comprehensive studies of mercury exposure due to artisanal and small-scale gold mining (ASGM) anywhere on the planet, in Madre de Dios, Peru. ASGM is the largest source of global mercury (Hg) pollution and the leading cause of deforestation in the Peruvian Amazon. ASGM emits large amounts of Hg directly into atmospheric, terrestrial and aquatic ecosystems via burning of mercury-gold amalgams and disposal of mercury-laden tailings. Hg is a potent neurotoxin that impacts human and wildlife health. When Hg enters aquatic systems, it is transported downstream, and the concentration of Hg near mining and downstream should be higher than in upstream areas. However, Duke research in Madre de Dios suggests that average hair Hg concentrations (a standard biomarker of total Hg exposure) in communities more than 150 km upstream of ASGM are 115% that of mining communities and 145% that of downstream communities. These high concentrations upstream of ASGM are also apparent in top predators, as one study has shown elevated mercury concentrations in giant otters (a protected species) within Manu National Park in Peru.

There are several viable hypotheses that could explain why human and wildlife mercury levels are high in a region that is otherwise physically, socially and economically disconnected from ASGM. These include fish migration, atmospheric deposition and land use/land cover change. Deforestation patterns due to ASGM, oil exploration and agricultural expansion may underlie many of these hypotheses, and, if true, forest conservation near ASGM could be crucial to protecting human and wildlife populations from high mercury concentrations and the resultant toxic impacts. Unfortunately, little is known about the influence of forest cover on mercury cycling.

Project Description

The primary research goal for this Bass Connections project is to understand and communicate how Hg enters upstream communities and wildlife, and whether deforestation is altering this movement of Hg. To address this goal, the team will:

  • Identify how Hg is entering the environment in communities upstream of ASGM (atmospheric deposition, migration of fish upstream, natural geogenic source of Hg in soils)
  • Measure variability of mercury methylation processes across the landscape
  • Determine the impact of forest cover and deforestation on mercury deposition and microbial methylation processes.

Team members will receive training on biogeochemical cycling of mercury and forest ecology (specific to Madre de Dios), design a research strategy for environmental data collection and travel to the Madre de Dios region to collect environmental samples (wet deposition, dry deposition, leaves, tree cores, soil, crops, fish). These samples will be collected along a minimum of two parallel transects running upstream from ASGM sites: one along the streambank and the other within the forest.

Anticipated Outcomes

Over 400 environmental samples collected and analyzed for total mercury and methylmercury concentrations, with a subset analyzed for mercury isotopes; results published and used as a basis for future research

Student Opportunities

Students will gain experience collecting environmental samples, conducting research internationally, communicating research plans with local populations and improving Spanish language abilities. Students of all levels are expected to be involved in the process of data analysis and interpretation, with the goal of ultimately submitting the results for publication.

The field team will consist of at least one master’s student and approximately three undergraduates from a variety of fields, such as ecology, environment, biology, global health, toxicology, international or environmental policy, sociology and statistics. Students should have at least an intermediate level of Spanish if they intend to go to the field; however, if a particular student has skills that would complement those of the rest of the team and does not meet the Spanish requirement, team leaders will still consider his/her application. Two Ph.D. students (Jacqueline Gerson, Axel Berky) will help with training, plan sampling and conduct experiments. Master’s and undergraduates students will be encouraged to choose areas of particular interest to focus on for improving their expertise and in analyzing the data.

Prior to the summer field season, the team will meet biweekly, led and organized by the Ph.D. students. Following the summer field season, the team will continue to meet biweekly to discuss data analysis and additional field sampling.

Duke undergraduates and graduate students can apply for this project team beginning on January 24. The priority deadline is February 16 at 5:00 p.m.


Summer 2018 – Spring 2019

  • Summer 2018: Team-building exercises; biweekly meetings to clarify team goals and finalize sampling plan; obtain required supplies; students attend language training, if necessary; visit offices of Regional Ministries of Health; Field Visit 1: identify sampling sites, obtain first set of environmental samples (end of wet season sample)
  • Fall 2018: Run Hg analyses on samples collected; plan for field collection 2 of environmental samples; biweekly meetings to discuss data analysis progress; Field Visit 2: round two of environmental samples (end of dry season); present round one results and study design to Mercury Foro
  • Spring 2019: Run Hg analyses on samples collected; biweekly meetings to discuss data analysis progress; compile any ancillary data collected from national databases


Independent study credit available for fall and spring semesters; summer funding

See earlier related team, Environmental Epidemiology in Latin America: Impact of an Oil Spill in the Peruvian Amazon (2017-2018).

Faculty/Staff Team Members

Emily Bernhardt, Arts & Sciences-Biology*
Heileen Hsu-Kim, Pratt School of Engineering-Civil & Environmental Engineering
Ernesto Ortiz, Duke Global Health Institute
William Pan, Nicholas School of the Environment-Environmental Sciences and Policy*
John Terborgh, Nicholas School of the Environment-Environmental Sciences and Policy

Graduate Team Members

Axel Berky, Master of Environmental Management, Ecotoxicolgy & Environmental Health
Jacqueline Gerson, Ecology-PHD

Community Team Members

Gabriela Salmon-Mulanovich, PRISMA, Peru

* denotes team leader


Active, New