Effects of low-level environmental pollutants exposure to fetal infant and baby on his development at after birth

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 14570343
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Public health/Health science
• Research Institution: Kagoshima University
• Principal Investigator: ANDO Tetsuo Kagoshima University, Graduate school of Medical and Dental Sciences, Research Associate, 大学院・医歯学総合研究科, 助手 (10107865)
• Project Period (FY): 2002 – 2005
• Keywords: Mercury levels / Maternal hair / Lactation period / Fish consumption / Baby's development

Research Abstract

We examined 202, 29, and 113 mothers and their children in M town, I City and A Islands in Kagoshima, Japan, respectively. The geometric mean concentrations (95%Cl) of maternal hair samples in those three areas were 1.66ppm (95%Cl=1.55-1.77ppm), 4.43ppm (95%=3.78-5.19), and 3.23ppm (95%Cl=2.87-3.63), respectively. We examined the relationship between the mothers' mercury exposure levels and the age at which their children started to walk alone, using a multiple regression analysis that adjusted for the gender of babies, maternal age at delivery, and gestational age. Since the distribution of total mercury was skewed and had a long upper tail, we used log-transformed values in the calculation of the mean concentrations and statistical analysis. In M town, we were able to interview 81 mothers at the time of the 1.5-year-old well-child care check-ups to obtain information on the age (in days) at which the children starting walking, and found no relation between this data and maternal hair mercury levels. In I City, we interviewed 22 mothers in the same manner, and found that the age (in months) when children started walking tended to be delayed among children delivered by mothers with higher mercury concentrations in their scalp hair (p=0.042). In A Islands, we interviewed 22 mothers and found no statistically significant relationship between those two variables. Next, we conducted a logistic analysis where the objective variable was whether or not a baby had started walking by the first birthday, and the explanatory variable was the mercury concentration of maternal hair samples. The sex of babies, mothers' ages and gestational ages were included in the logistic models as covariates. In this analysis all the mothers had mercury levels lower than 10ppm. The proportion of children who started walking after their first birthday increased with [increasing] maternal hair mercury concentration, but the tend was not statistically significant (p=0.091). Those findings suggest that maternal hair Hg concentrations as low as 10ppm may cause locomotors developmental delays in children.