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.
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.
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
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
This Team in the News
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, Ecotoxicology & Environmental Health
Jacqueline Gerson, Ecology-PHD
Christian Lara, MIDP 2 Year Masters
Tatiana Manidis, Master of Environmental Management, Ecotoxicology & Environmental Health
/undergraduate Team Members
Kelsey Lansdale, Environmental Sci/Policy (AB)
/zcommunity Team Members
Gabriela Salmon-Mulanovich, PRISMA, Peru