Association of urinary cadmium concentration with intellectual development among 1-year-old infants in a county of Jiangsu Province

Background Cadmium pollution is increasingly serious, and a growing number of studies suggest that cadmium exposure may affect intellectual development of children.

Objective This study is designed to evaluate urinary cadmium exposure levels of infants aged 1 year living in a county of Jiangsu Province, and explore the association between cadmium exposure and infant intellectual development.

Methods A total of 483 1-year-old infants were enrolled from a county in Jiangsu Province in 2010. Self-made questionnaires were distributed to obtain basic information of the infants. At the same time, the Developmental Screening Test (DST) for Children Aged 0-6 Years was used to quantitatively evaluate mental index (MI) and development quotient (DQ) as indicators of infant intellectual development. Spot urine samples were collected and cadmium concentrations in urine were measured by inductively coupled plasma mass spectrometery (ICP-MS). A multiple linear regression model was used to analyze the correlation between infants' urinary cadmium concentrations and DST scores, and the differences of MI and DQ scores were compared among different urinary cadmium exposure groups divided by tertiles.

Results The median (P₂₅, P₇₅) of creatinine-adjusted urinary cadmium concentration was 0.235 (0.125, 0.492) μg·g^-1. The mean ±standard deviation of MI and DQ scores were 84.19±12.43 and 86.80±11.82, respectively. In the multiple linear regression analysis, MI was negatively correlated with urinary cadmium concentration (b=-1.55, 95% CI: -2.68﹣-0.42, P=0.007), but there was not a significant correlation between DQ and urinary cadmium concentration (P=0.052), and no significant difference in DST scores was observed among different urine cadmium exposure groups (P>0.05). In the sex-stratified analysis, a negative correlation between urinary cadmium concentration and MI was found in girls (b=-1.84, 95% CI: -3.62﹣-0.05, P=0.043), but not in boys (P=0.092).

Conclusion Exposure to cadmium may affect the intellectual development of infants, especially of girls.