Urinary arsenic and relative telomere length in 5–7 year old children in Bangladesh

•Early childhood is a critical period for telomere biology.•Prior studies of urinary As and telomere length in children have had mixed findings.•We examined urinary As and telomere length in 5–7 year old Bangladeshi children.•Urinary As was associated with significant decreases in relative telomere length.•Arsenic exposure may be related to telomere shortening in early to mid-childhood. Telomere length has been associated with the occurrence and progression of common chronic and age-related diseases, and in younger populations, may represent a biomarker of disease susceptibility. Early childhood is a critical period for telomere biology as this period is characterized by a rapid decline in telomere length due to a large turnover of highly proliferative cells and may represent a period of unique sensitivity to environmental insults. Arsenic (As) exposure has been associated with both telomere lengthening and shortening in adults and children and some evidence suggests the effects may differ by level and timing of exposure. Given the lack of clarity across studies, we investigated the association between urinary As and leukocyte telomere length among 476 five- to seven-year-old children enrolled in the Bangladesh Environmental Research in Children's Health (BiRCH) cohort. In a series of multivariable models, adjusted for key covariates, we examined associations between urinary As and relative telomere length (RTL) of whole blood DNA. We observed small but consistent, negative associations between urinary As and RTL, such that a doubling of urinary As was associated with a −0.017 (95% CI: −0.030, −0.005; p = 0.0056) decrease in RTL, in fully adjusted models. We also observed a somewhat stronger inverse relationship between urinary As concentration and RTL among children born to fathers ≥ 30 years of age at the time of birth, than those