Prenatal exposure to multiple toxic heavy metals and neonatal neurobehavioral development in Shanghai, China

Background

Epidemiological studies examining the effects of prenatal toxic heavy metals exposure on neonatal development at the population-based level are limited.

Objective

To explore prenatal exposure levels to toxic heavy metals and examine whether exposure is associated with neonatal development.

Methods

A stratified multi-stage cluster sampling methodology was used to investigate 1652 mother-infant pairs from 2008 through 2009 in Shanghai. Cord blood concentrations of Pb, Hg, Cd, As, Tl and NBNA (Neonatal Behavioral Neurological Assessments) were tested. We defined three different exposure levels (low, medium and high) according to the considered safe values.

Results

The median blood Pb, Hg, Cd, As and Tl concentrations were 41 μg/L, 1.88 μg/L, 0.03 μg/L, 0.86 μg/L and 0.02 μg/L, respectively, which all were in the level considered safe. Increasing exposure to Cd, Hg, As and Tl during pregnancy was associated with decreasing NBNA scores. High level-exposure (exceeding the level considered safe) of Hg, Cd and Tl had lower NBNA scores compared to medium and low levels (both in the level considered safe), which implied that the level considered safe of these heavy metals was safe for the newborns' development. The mean decreasing scores of NBNA was 0.61, 1.50 and 0.84 (total score = 40) with high-level exposure of Hg, Cd and Tl, respectively. The medium-level exposure (in the level considered safe) to As had lower NBNA scores compared to low-level exposure, which implied that level of considered safe for As was not safe to the newborns' development. However, prenatal Pb high-exposure did not affect NBNA scores either by single or multiple factor analysis. In addition, important contribution factors for heavy metals pollutants were diet, lifestyle and housing renovation.

Conclusions

Prenatal heavy metals except Pb exposures were associated with NBNA. The adverse effect of medium-level As warrants the need to further investigate the safe range of As.