The Biomarkers of Exposure to Arsenic (BEAR) Pregnancy Cohort in Mexico: Maternal Arsenic Methylation Linked to Poorer Birth OutcomesAbstract Number:2571 Jessica Laine*, Kathryn Bailey, Marisela Rubio-Andrade, Andrew Olshan, Lisa Smeester, Zuzana Drobná, Amy Herring, Miroslav Stýblo, Gonzalo Garcia-Vargas, and Rebecca Fry Jessica Laine* University of North Carolina, Chapel Hill , United States, E-mail Address: [email protected] Search for more papers by this author , Kathryn Bailey University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Marisela Rubio-Andrade Universidad Juarez del Estado de Durango, Mexico, E-mail Address: [email protected] Search for more papers by this author , Andrew Olshan University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Lisa Smeester University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Zuzana Drobná University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Amy Herring University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Miroslav Stýblo University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author , Gonzalo Garcia-Vargas Universidad Juarez del Estado de Durango, Mexico, E-mail Address: [email protected] Search for more papers by this author , and Rebecca Fry University of North Carolina, Chapel Hill, United States, E-mail Address: [email protected] Search for more papers by this author AbstractBackground:Exposure to inorganic arsenic (iAs) from drinking water is a global public health problem yet much remains unknown about the extent of exposure in susceptible populations.Objectives: To establish the Biomarkers of Exposure to ARsenic (BEAR) prospective pregnancy cohort in Gómez Palacio, Mexico, in order to better understand the effects of iAs exposure on pregnant women and their children.Methods: Two hundred pregnant women were recruited for this study. Concentrations of iAs in drinking water (DW- iAs) and maternal urinary concentrations of iAs and its monomethylated and dimethylated metabolites (MMAs and DMAs, respectively) were determined. Birth outcomes were analyzed for their relationship to DW-iAs and to the concentrations and proportions of maternal urinary arsenicals.Results: DW-iAs for the study subjects ranged from <0.5 to 236 µg As/L. More than half of the women (53%) had DW-iAs that exceeded the World Health Organization’s recommended guideline of 10 µg As/L. DW-iAs was significantly associated with the sum of the urinary arsenicals (U-tAs). While DW-iAs and U-tAs were not associated with any birth outcomes, both maternal urinary concentrations and proportions of MMAs were associated with a decrease in newborn birth weight.Conclusions: Biomonitoring results demonstrate that pregnant women in Gómez Palacio are exposed to potentially harmful levels of DW-iAs. The data support a relationship between iAs metabolism in pregnant women and adverse birth outcomes. The results underscore the risks associated with iAs exposure in vulnerable populations.