Contribution of gestational exposure to ambient traffic air pollutants to fetal cord blood manganese

Abstract

Motor vehicle emissions have become a major source of air pollution. Contributions of motor vehicle emissions to exposure to toxic metals such as manganese remain inconclusive. This study investigates the relationship between the concentration of manganese in cord blood and exposure to criteria air pollutants during pregnancy. A total of 1526 mother-newborn pairs were recruited by stratified sampling between April, 2004 and July, 2005. The newborns' mothers completed questionnaires that collected information on their demographic characteristics, medical histories, and living environments. Cord blood samples were collected at birth and analyzed by inductively coupled plasma mass spectrometry for manganese. Information about criteria air pollutants which included CO, NO(2), ozone, SO(2), and PM(10) was obtained from monitoring stations run by the Taiwan Environmental Agency. Using the Arc9 Geographic Information System's kriging method, the concentration of each criteria pollutant was estimated at each newborn's residence. The geometric mean for cord blood manganese concentrations was 47.0 μg/L (GSD=1.4). After adjusting for confounding factors such as family income, maternal education, maternal smoking, alcohol drinking during pregnancy, maternal age, child gender, parity, gestational age, and birth season, the results of a multiple linear regression model indicated that cord blood manganese concentration was significantly associated with NO(2) concentration in each trimester, as well as the whole duration of gestation. Between the pregnant women exposed to the highest and those to the lowest quartile of NO(2), a 6 μg/L difference in cord blood manganese concentration was found. This finding suggests that despite other sources of manganese exposure, maternal exposure to ambient NO(2), a surrogate for traffic emission, significantly contributed to fetal cord blood manganese level. Further study is warranted to determine whether the contribution of manganese due to traffic emission causes adverse health effects in fetuses.