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Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide, with ∼80% of CVD-related deaths occurring in low- and middle-income countries. Growing evidence suggests that chronic arsenic exposure may contribute to CVD through its effect on endothelial function in adults. However, few studies have examined the influence of arsenic exposure on cardiovascular health in children and adolescents. To examine arsenic's relation to preclinical markers of endothelial dysfunction, we enrolled 200 adolescent children (ages 15–19 years; median 17) of adult participants in the Health Effects of Arsenic Longitudinal Study (HEALS), in Araihazar, Bangladesh. Participants' arsenic exposure was determined by recall of lifetime well usage for drinking water. As part of HEALS, wells were color-coded to indicate arsenic level (<10 μg/L, 10–50 μg/L, >50 μg/L). Endothelial function was measured by recording fingertip arterial pulsatile volume change and reactive hyperemia index (RHI) score, an independent CVD risk factor, was calculated from these measurements. In linear regression models adjusted for participant's sex, age, education, maternal education, land ownership and body weight, individuals who reported always drinking water from wells with >50 μg/L arsenic had a 11.75% lower level of RHI (95% CI: −21.26, −1.09, p = 0.03), as compared to participants who drank exclusively from wells with ≤50 μg/L arsenic. Sex-stratified analyses suggest that these associations were stronger in female participants. As compared to individuals who drank exclusively from wells with ≤50 μg/L arsenic, the use of wells with >50 μg/L arsenic was associated with 14.36% lower RHI (95% CI: −25.69, −1.29, p = 0.03) in females, as compared to 5.35% lower RHI (95% CI: −22.28, 15.37, p = 0.58) in males for the same comparison. Our results suggest that chronic arsenic exposure may be related to endothelial dysfunction in adolescents, especially among females. Further work is needed to confirm these findings and examine whether these changes may increase risk of later adverse cardiovascular health events. • Arsenic exposure may contribute to CVD through its effect on endothelial function. • Few have examined the influence of arsenic on cardiovascular health in adolescents. • Higher lifetime As exposure was related to significantly reduced endothelial function. • Endothelial dysfunction in adolescence may be a risk factor for later life disease. [ABSTRACT FROM AUTHOR]

• 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 < 30 years; however, we did not observe a statistically significant interaction. Our study suggests that As influences RTL, with detectable associations in early to mid-childhood. Further studies are needed to confirm our findings and investigate the potential long-term impacts of telomere shortening in childhood on later life health outcomes. Additional studies exploring how dose and timing of exposure may relate to RTL are critical to understanding As's relationship to telomere length. [ABSTRACT FROM AUTHOR]