Project Abstract
Artisanal small-scale gold mining (ASGM) communities are at extremely high risk for heavy metal / metalloid
exposure including mercury (Hg), lead (Pb), arsenic (As), and manganese (Mn) with potential irreversible
effects on the developing central nervous system (CNS). Exposure to these metals in childhood could lead to a
lifelong reduction in educational and job opportunities. Early identification of heavy metal neurotoxicity has
been challenging, but preliminary work suggests central auditory processing (CAP) may correlate with heavy
metal exposure and correlate with early neurocognitive changes. Through our previous work we have: 1)
developed a wireless, field deployable peripheral and central hearing assessment system suitable for the
developing world, 2) established research collaborations in Nicaragua and 3) demonstrated that central
auditory testing can be used to assess brain function. This study will determine whether portable, mobile
central auditory testing can identify children with significant heavy metal neurotoxicity. Minimally trained
technicians will utilize an innovative mobile tablet-based platform to perform audiometry and comprehensive
CAP tests [Dichotic Digits (DD), antiphase noise and signal testing (N0Spi), Gap Detection Threshold (GDT),
Latin American Spanish Hearing in Noise Testing (LASHINT), and Fixed Level Frequency Testing (FLFT)] on a
large cohort (200) of children (6 – 18 years) living in a Nicaraguan ASGM communities. Data will be uploaded
to a mobile database platform (REDCap) along with detailed socioeconomic and risk factor data. In addition,
toenail and dried blood spot (DBS) samples will be collected and analyzed for concentrations of 5 heavy
metals (Pb, Hg, As, Mn, and Al) using inductively coupled plasma mass spectrometry (ICP-MS) analysis. The
concentrations of these metals will be correlated with CAP test performance using regression analysis and
non-parametric ANOVA (Kruskal-Wallis) analysis will be used to assess differences between children with
metal levels above compared to those within the reference range. The proposed work will build upon existing
research capacities and collaboration with two major collaborating institutions in Nicaragua by: 1) developing
research capabilities and providing instruments that are ideally suited to remote impoverished environments, 2)
adapting and training research personnel in database (REDCap) design and implementation, 3) providing a
foundation for future comprehensive epidemiological studies through training, 4) mentoring Nicaraguan
researchers in advanced research design and methodology, 5) providing additional expertise in specialized
areas of interest (e.g. central auditory processing disorders, heavy metal neurotoxicity), 6) facilitating the
research partnership between MMO and UNAN-Leon CISTA. This project will provide preliminary data on
heavy metal exposure and central auditory test performance that would form the basis for a follow-up grant
submission from our Nicaraguan colleagues to address this important environmental health issue.