Within-person reproducibility of red blood cell mercury over a 10- to 15-year period among women in the Nurses’ Health Study II

Kioumourtzoglou, Marianthi-AnnaRoberts, Andrea LNielsen, FlemmingTworoger, ShelleyGrandjean, PhilippeWeisskopf, Marc2018-01-102014Kioumourtzoglou, Marianthi-Anna, Andrea L Roberts, Flemming Nielsen, Shelley S Tworoger, Philippe Grandjean, and Marc G Weisskopf. 2014. “Within-Person Reproducibility of Red Blood Cell Mercury over a 10- to 15-Year Period Among Women in the Nurses’ Health Study II.” Journal of Exposure Science and Environmental Epidemiology 26 (2) (December 10): 219–223. doi:10.1038/jes.2014.82.1559-0631http://nrs.harvard.edu/urn-3:HUL.InstRepos:34623031Background Most epidemiologic studies of methylmercury (MeHg) health effects rely on a single measurement of a MeHg biomarker to assess long-term exposures. Long-term reproducibility data are, therefore, needed to assess the reliability of a single measure to reflect long-term exposures. In this study we assessed within-person reproducibility of red blood cell (RBC) mercury (Hg), a marker of methyl-mercury, over 10–15-years in a sample of 57 women. Methods Fifty-seven women from the Nurses’ Health Study II provided two blood samples 10–15-years apart (median:12 years), which were analyzed for mercury levels in the red blood cells (B-Hg*). To characterize within-person reproducibility we estimated correlation and intraclass correlation coefficients (r and ICC) across the two samples. Further, we compared different prediction models, including variables on fish and seafood consumption, for B-Hg* at the first sample using leave-one-out cross-validation to assess predictive ability. Results Overall, we observed strong correlations over 10–15 years (r=0.69), as well as a high ICC (0.67; 95%CI: 0.49, 0.79). Fish and seafood consumption reported concurrently with the first B-Hg* sample accounted for 26.8% of the variability in that B-Hg*, giving a correlation of r=0.52. Conclusions Despite decreasing B-Hg* levels over time, we observed strong correlations and high ICC estimates across B-Hg* measured 10–15 years apart, suggesting good relative within-person stability over time. Our results indicate that a single measurement of B-Hg* likely is adequate to represent long-term exposures.en-USreproducibilityNHSIImethylmercuryWithin-person reproducibility of red blood cell mercury over a 10- to 15-year period among women in the Nurses’ Health Study IIJournal Article2018-01-1010.1038/jes.2014.82