# Exploratory Use of Stable Mercury Isotopes to Distinguish Dietary Sources of Methylmercury and Their Relation to Neurodevelopment

> **NIH NIH R21** · OREGON STATE UNIVERSITY · 2021 · $191,107

## Abstract

Project Summary
 For most populations, fish consumption is considered the main dietary source for methylmercury, a
potent neurotoxin. Fish tissue is also a rich source for beneficial nutrients. Rice is a staple food for more than
three billion people. Where rice is a dietary staple, it can also be an important dietary source of methylmercury,
without the same beneficial nutrients as fish. There is evidence that methylmercury toxicity is modified by diet
(rice versus fish). As diet is the primary pathway for methylmercury exposure, analyses of mercury in hair and
blood reflect dietary methylmercury exposure, however, these biomarkers do not differentiate between
methylmercury sources. Rice and fish consumption are usually estimated using self-reported food frequency
questionnaires; however food frequencies are often inaccurate due to recall bias. To characterize the
relationship between methylmercury and neurodevelopment (independent of modification by nutrition), it is
critical to characterize the dietary source of methylmercury, with less measurement error. Stable mercury
isotopes have been used to track dietary methylmercury sources in food webs, and may be used to distinguish
between rice and fish methylmercury intake in human populations. Briefly, mercury is comprised of seven
isotopes; all seven isotopes are subject to mass dependent fractionation (MDF), while mass independent
fractionation (MIF) occurs mainly for the two odd-isotopes. Unlike MDF, MIF is conserved during trophic
transfer and metabolism. We measured stable mercury isotopes in a subset of 21 maternal hair samples from
our birth cohort in rural China, where most mothers ingested rice daily, and more than 40% of the mothers
rarely or never ingested fish. Our findings indicated that MIF in human hair can be used to distinguish
methylmercury intake from rice versus fish in our cohort. Thus hair MIF is a promising novel biomarker, which
should be further validated. We propose to analyze mercury isotopes in banked third trimester maternal hair
samples for those participants, whose offspring completed the 12-month neurodevelopmental assessment
(n=264 hair samples). We propose the following aims: Aim 1. Determine how the isotopic composition of
mercury in maternal hair varies depending on diet, among pregnant mothers in rural China, after controlling for
potential confounders (e.g., maternal education, etc.). Aim 2. In models investigating prenatal methylmercury
exposure and children's neurodevelopment, we will explore whether the source of methylmercury exposure,
determined from maternal hair MIF, modifies its effect on children's neurodevelopmental outcomes. In
summary, use of hair MIF will improve our understanding of methylmercury toxicity by accounting for modifying
effects of diet with better sensitivity and precision than has been possible previously.

## Key facts

- **NIH application ID:** 10271302
- **Project number:** 5R21ES032600-02
- **Recipient organization:** OREGON STATE UNIVERSITY
- **Principal Investigator:** Sarah E Rothenberg
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $191,107
- **Award type:** 5
- **Project period:** 2020-09-28 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10271302

## Citation

> US National Institutes of Health, RePORTER application 10271302, Exploratory Use of Stable Mercury Isotopes to Distinguish Dietary Sources of Methylmercury and Their Relation to Neurodevelopment (5R21ES032600-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10271302. Licensed CC0.

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