Is prenatal arsenic exposure associated with salivary cortisol in infants in Arica, Chile? An exploratory cohort study

INTRODUCTION: In animal models, gestational exposure to inorganic arsenic has been associated with higher corticosterone concentration and consequent impairment of stress control in offspring. An equivalent association relating cortisol, a glucocorticoid hormone, in humans has not been previously studied. OBJECTIVE: The aim of the study was to explore the association between prenatal inorganic arsenic exposure and salivary cortisol in infants from Arica, Chile. MATERIAL AND METHODS: A cohort study of 168 mother-child dyads was recruited. In the 2nd trimester of pregnancy, urinary inorganic arsenic was assessed; 18-24 months after delivery, salivary cortisol was measured in the children. Maternal cortisol, maternal depression, stress, and socio-economic status were also evaluated. RESULTS: The adjusted association was estimated with multiple linear regression after evaluating confounding through a directed acyclic graph. Median urinary inorganic arsenic in pregnant women was 14.1 µg/L (IQR: 10.4-21.7) while salivary cortisol in the children was 0.17 µg/L (IQR: 0.11-0.38). Among children from the highest income families (> 614 USD/month), arsenic exposure was associated with salivary cortisol. Children in the third quartile of arsenic exposure had -0.769 units of the logarithm of salivary cortiso, compared with those in the first quartile (p = 0.045). CONCLUSIONS: In this sample, prenatal exposure to arsenic was associated with salivary cortisol (third quartile of inorganic arsenic), only in infants belonging the highest income strata (> 614 USD). More studies are needed to confirm these preliminary results.