Association of Ambient NO 2 Concentrations during Pregnancy

1. Association of Ambient NO2 Concentrations during Pregnancy with Fetal Cord Blood Manganese in Taiwan Ying-Ying Lin, Yaw-Huei Hwang, Pau-Chung Chen, Jyung-Hung Liu, Hui-Chen Wu, Yue-Liang Leon Guo Institute of Occupational Medicine and Industrial Hygiene, College of Public Health, National Taiwan University, Taipei, Taiwan, R.O.C. Study aim Results Methylcyclopentadienyl manganese tricarbonyl (MMT) has been widely used as a substitute for lead containing anti-knocking additives in gasoline since 1990 in Taiwan. In our previous study, it was demonstrated that exposure to MMT-containing gasoline might have lead to fetal exposure to elevated manganese. This study was further conducted to investigate the relationship between the concentration of manganese in cord blood and the ambient air NO2 concentration during pregnancy, a surrogate for traffic related air pollution. The average maternal age was 28 years, and most of them were educated at or above junior high school. The boy proportion of neonates was 51%. Approximately a half of the newborns were the first children of their mothers. The geometric means of cord blood manganese concentration was 47.0 μg/L. After adjusting for the potential confounders by using multiple regressions, ambient NO2 concentration during all trimesters was associated with cord blood manganese (β= 0.008, p< 0.0001) (table 1). To determine which gestational period was the most important, we found that cord blood manganese was most associated with ambient air NO2 in early stage of pregnancy (Table 2). There appeared to be cumulative effect of exposure to traffic air pollution during the whole period of gestation on cord blood manganese level (Figure 3). Materials and Methods • Study population • In total, 1526 newborns were recruited by stratified sampling from May 2004 to July 2005. Among them, 1407 mothers (92.2%) filled out questionnaires and had cord blood samples collected. Informed consents were obtained from the newborns’ parents before they were included in the study. • Data collection • Questionnaire was administered to the mothers after childbirth to collect basic information, including date of delivery, parental ages, occupations, education, family income, nationality, etc. Additionally, gestation information, history of pregnancy, home environment information, and use of western and herbal medicine were collected in this study. Nurses were responsible for the measurements of neonates, including birth weight, height, gender, head circumference, etc. • Sample collection and analysis • Cord blood samples were collected at birth and stored in EDTA tubes. The level of manganese and lead concentration were determined using inductively coupled plasma mass spectrometry (7500C, Agilent Technologies, Japan). All the measurements were checked for accuracy with standard reference materials. If the concentration of a cord blood metal was not detectable, a half of the detection limit was assigned to it for further statistical analysis. • Exposure assessment • The final birth cohort consisted of 1343 mother-newborn pairs (Fig.1). With the data from Taiwan Environmental Protection Administration air quality monitoring stations, the Ordinary Kriging method was used to estimate the pollutant levels of each subjects’ residents during pregnancy by month from May 2004 to July 2005 for NO2 concentrations (Fig.2). In general, the Kriging method was used as a statistical mapping technique using data collected at each point location, to predict concentration in each grid cell over a spatial domain. All geostatistical analyses were performed using ArcView GIS (version 9.3). β estimate (95% CI) * Fig. 3. β estimate for cord blood manganese levels by average ambient air NO2 concentrations during periods of pregnancy *: 1-10: Average ambient air NO2 concentration from 1st month to 10th month during pregnancy. 2-10, to 9-10, similar average NO2 concentration as of 1-10. Discussion and Conclusion After adjusting for potential confounders, it was found that fetal cord blood manganese concentration was associated with ambient air NO2 concentration in early stage of pregnancy. Further study is warranted to explore whether traffic-resulted manganese exposure causes potential adverse health effect in fetus. Fig. 1. Geographical locations of study subjects’ residence. Fig. 2. Ambient air NO2 concentration and air monitoring sites. E-mail address: R97841015@ntu.edu.tw