Effect of Arsenic Exposure during Pregnancy on Infant Development at 7 Months in Rural Matlab, Bangladesh

Article excerpt

BACKGROUND: Exposure to arsenic-contaminated drinking water during pregnancy is associated with low birth weight and fetal loss, and there is concern that the infants' development may be affected.

OBJECTIVE: We assessed the effects of in utero arsenic exposure during pregnancy on infants' problem-solving ability and motor development.

METHODS: We conducted a large population-based study of nutritional supplementation with 4,436 pregnant women in Matlab, Bangladesh, an area of high-arsenic-contaminated tube wells. We measured arsenic concentration in spot urine specimens at 8 and 30 weeks of pregnancy. We assessed a subsample of 1,799 infants, born to these mothers, at 7 months of age on two problem-solving tests (PSTs), the motor scale of the Bayley Scales of Infant Development--II, and behavior ratings.

RESULT: Arsenic concentrations in maternal urine were high, with a median (interquartile range) of 81 [micro]g/L (37-207 [micro]g/L) at 8 weeks of gestation and of 84 [micro]g/L (42-230 [micro]g/L) at 30 weeks. Arsenic exposure was related to many poor socioeconomic conditions that also correlated with child development measures. Multiple regressions of children's motor and PST scores and behavior ratings, controlling for socioeconomic background variables, age, and sex, showed no significant effect of urinary arsenic concentration on any developmental outcome.

CONCLUSION: We detected no significant effect of arsenic exposure during pregnancy on infant development. However, it is possible that other effects are as yet unmeasured or that effects will become apparent at a later age.

KEYWORDS: Bangladesh cognitive function, infants, motor development, problem-solving tests, urinary arsenic. Environ Health Perspect 117:288-293 (2009). doi:10.1289/ehp.11670 available via http://dx.doi.org/[Online 24 October 2008]

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Arsenic is a widely distributed environmental pollutant with known carcinogenic and neurotoxicant effects [World Health Organization (WHO) 2001]. More than 100 million people worldwide have been estimated to be chronically exposed to drinking water containing high arsenic levels (Alaerts et al. 2001; National Research Council 2001). In Bangladesh, a nationwide survey initiated in 1998 indicated that about 35 million people were exposed to > 50 [micro]g/L arsenic, which is the drinking water standard in Bangladesh, whereas 57 million had water exceeding the WHO guideline value of 10 [micro]g/L (British Geological Survey 2001). Studies in school-age children have reported that arsenic exposure due to living near smelters in Mexico (Calderon et al. 2001; Rosado et al. 2007) and the United Sates (Wright et al. 2006) or drinking contaminated water in Taiwan (Tsai et al. 2003) and India (von Ehrenstein et al. 2007) is associated with deficits in children's cognitive function. Two recent studies in Bangladesh in children 6 and 10 years of age (Wasserman et al. 2004, 2007) showed that arsenic concentration in their drinking water was related to deficits in global and performance IQ that were larger at 10 than at 6 years of age.

We are unaware of any prospective study examining the effect of exposure in pregnancy on offspring development. During pregnancy, transplacental transfer of arsenic occurs both in animals (Golub et al. 1998) and in humans (Concha et al. 1998). In animals, a high dose of arsenic is associated with detrimental effects on the developing embryo (Golub et al. 1998; National Research Council 1999; Wlodarczyk et al. 1996). In humans, exposure to high arsenic levels in drinking water is associated with reduction in birth weight (Hopenhayn et al. 2003; Huyck et al. 2007) and increase in fetal loss (Ahmad et al. 2001; Rahman et al. 2007). Considering the above, we hypothesized that arsenic exposure during pregnancy would be neurotoxic to the developing brain and would lead to behavioral changes in the offspring.

We conducted a large community-based randomized trial of the effects of food and micronutrient supplementation in pregnant women [Maternal and Infant Nutritional Intervention at Matlab (MINIMat) study] on birth outcomes and the development of their children in Matlab, a rural area of Bangladesh. …