Background & Significance: Inorganic arsenic is a heavy metal naturally found in soil and human exposure to this heavy metal causes adverse effects. Exposure risks are particularly high in developing children. Arsenic is mainly found in bedrock. It is also a by-product of smelting, it is used in cement production, and historically is has been found in crop pesticides. Among other ill-effects, arsenic exposure in humans can cause respiratory diseases, peripheral neuropathy and liver fibrosis. In particular arsenic has been shown in many studies to be a contributing factor in the risk for hypertension in adults however no studies have yet examined possible associations between blood arsenic and blood pressure in children.
Aims & Objectives: The aim of this study was to investigate possible associations between arsenic and systolic and diastolic blood pressure in children. To examine whether possible effects were specific to arsenic, secondary analyses also tested associations between blood lead levels and blood pressure and blood cadmium levels and blood pressure.
HypoThesis: It was hypothesized that blood arsenic predicts systolic and diastolic blood pressure. Because previous studies have not been conducted, no direction of association was predicted.
Methods: This was an observational study of 204 children from two far west Texas rural communities. Children were recruited from two elementary schools and were between the ages of 4 and 11. Parents completed informed consent prior to testing and provided child and family demographic and medical information. Anthropometric measurements were taken for each child and blood pressure was automatically recorded using an electronic sphygmomanometer. Finger stick blood samples were collected, analyzed using Inductive-Coupled Plasma Spectrometry (ICP-MS) and tested for arsenic, lead, cadmium, and iron in whole blood. For the primary analysis, a generalized linear model was calculated predicting systolic and diastolic blood pressure (in separate models) controlling for sex and age, with school included as a random effect.
Results: Blood arsenic level predicted decreased systolic blood pressure (F=8.19, p=.0047). For every 1 µg/dL of arsenic, child systolic blood pressure decreased by 3.99 mmHg. A positive association was found between blood cadmium level and blood pressure. Cadmium blood level in children predicted an association between cadmium and systolic blood pressure (F=5.45, p=.0205).
Conclusion: Low-level arsenic exposure as determined by blood arsenic level linearly predicts a decrease in blood pressure in young children. This might be explained by arsenic-induced over production of nitric oxide in the endothelium and interference of nitric oxide synthase leading to vasodilation. Moreover, low-level cadmium exposure as determined by blood cadmium levels predict hypertension (increased systolic and diastolic blood pressure) in young children. The effects might reflect secondary effects of cadmium on kidney function. These and other explanations for the findings are discussed. The findings provide further evidence that very low-level heavy metal exposure has detrimental effects on early critical physiological functions. Additional studies are needed to replicate and expand these findings.
Recommendations: Children must be consistently and frequently monitored for low detectable levels of heavy metal exposure. Although not the focus of this study, is should be noted that relatively high levels of prehypertension and hypertension were observed. Physical activity can improve metabolism which may promote toxin clearance in young children while also promoting normal blood pressure and lower body weight. Several physical activity programs currently in use throughout the country have been proposed and should be incorporated into vulnerable childrenâ??s daily school regiments
