Mercury levels in pregnant women in Japanese general population and child birth size

Abstract

In Japan, approximately 80-90% of human mercury (Hg) exposure is derived from fish consumption. In Japan, a methyl-Hg (MeHg) poisoning due to intake of contaminated fish, Minamata Disease occurred in 1956. Since then, Japanese government established environmental standards and emission reduction and guidelines to maintain fish intake. Consequence, MeHg intake remained unchanged since 1994, as mean levels of 8.4 µg/person/day among Japanese general population. In this presentation, we introduce birth cohort studies conducted in Japan, and discuss their association to children’s birth size.We have conducted the Hokkaido study on Environment and Children’s Health: Sapporo cohort. Pregnant women were enrolled in 2002 to 2005, with total 514 agreement. The maternal hair Hg levels of 1.41 µg/g at delivery. Prenatal exposure to MeHg has no association with newborn anthropometric measurements, although the incidence of babies born small-for gestational age by weight may reduce with higher concentrations of Hg in hair. Fish is the main exposure source of Hg but also of long-chain polyunsaturated fatty acids. High frequency of fish consumption may mask the adverse effects of MeHg on birth size with the beneficial effect of essential nutrition. Other studies in Japan are 1. Tohoku region of Japan with 486 infants in 2001-2003. Median total Hg in whole cold blood is 10.1 ng/g and found no association with a reduction of birth weight among all infant. 2. Japan Environment and Children’s Study with approximately 100,000 mothers enrolled from 2011-2014. Total Hg in maternal blood were median 3.66 ng/g. Only slight association was found that compared to infants of lowest maternal Hg quartile, infants of highest maternal Hg quartile had a reduced birth head circumference. Consider as a whole, the results suggest that there are no associations with prenatal Hg exposure and birth size at this level.