Sex-specific associations between early-life microplastic exposure and children’s physical development: Evidence from a study in China

Microplastics (MPs) are widely present in the human world. This study aimed to explore the sex - specific associations between early-life MPs exposure and BMI as well as BMI z-scores in children. We enrolled 1,080 children aged 10 years from the Ma'anshan Birth Cohort in China. A Laser Direct Infrared instrument was used to detect the presence of 19 types of MPs in the children's urine. Children's height and weight were measured to calculate BMI and BMI z-scores. Linear regression, logistic regression, restricted cubic spline regression, and Quantile g-computation regression were employed to investigate the associations between the MPs and children's BMI and BMI z-scores. The results demonstrated the overall detection rate of MPs was 91.1%, with PTFE exhibiting the highest rate at 49.9%. Elevated levels of PE, PAM, and small-size MPs in urine were associated with increased risks of overweight/obesity in boys (OR = 1.156, 95% CI: 1.048, 1.274; OR = 1.278, 95% CI: 1.159, 1.409; OR = 1.114, 95% CI: 1.007, 1.233). PA and PE levels were associated with an increased risk of girls' overweight/obesity (OR = 1.150, 95% CI: 1.055, 1.252; OR = 1.226, 95% CI: 1.126, 1.335). PAM and PE exposures were associated with underweight risk in boys and girls, respectively. Moreover, PTFE levels were positively associated with higher BMI z-scores in boys (β = 0.052, 95% CI: 0.003, 0.101). Significant sex-specific associations were observed between exposure to specific MPs and both BMI categories and BMI z-scores in children.