Prenatal thallium exposure and child neurodevelopment at 2 years: a birth cohort study in China

Thallium, a highly toxic heavy metal, is well-documented for causing neurodevelopmental toxicity in animal models. However, epidemiological evidence regarding the effects of early-life thallium exposure on human neurodevelopment remains limited.

To investigate the trimester-specific associations of maternal thallium exposure with early childhood neurodevelopment.

A total of 423 mother-child pairs, with trimester-specific urinary samples, were followed up until the children reached 2 years of age. Thallium concentrations were measured using inductively coupled plasma mass spectrometry, while mental and psychomotor development indexes (MDI and PDI) were evaluated using the Chinese version of Bayley Scales of Infant Development (BSID-CR). Trimester-specific associations of specific gravity (SG)-adjusted urinary thallium concentrations with neurodevelopment were estimated using a multiple informant model.

After adjusting for potential confounders, each unit increase in thallium exposure during the third trimester was associated with 6.55-point reduction in MDI domain (95 % CI: -12.88 to -0.22) and 7.13-point reduction in PDI domain (95 % CI: -13.51 to -0.74). When performing stratified analyses by child sex, the associations of third-trimester thallium concentrations with PDI were more prominent in boys (β: -9.57; 95 %CI: -17.51 to -1.64) than in girls (β: -0.87; 95 %CI: -14.51-12.76).

This birth cohort study suggests that prenatal thallium exposure during the third trimester, but not during other periods, had detrimental effects on early childhood mental and psychomotor development.