Chronic arsenic exposure from ingesting contaminated drinking water is a global public health concern with the Ganges Delta region the most heavily impacted. Upon ingestion, inorganic arsenic (InAs) is methylated to monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA). An individual's ability to methylated arsenic is considered a risk factor for arsenic-induced disease. This study quantifies the risk of arsenic-metabolism on skin lesions in a population chronically exposed to arsenic-contaminated drinking water in Pabna, Bangladesh.
First void urine samples were collected in sterile, single use containers and frozen until analysis. Urinary arsenic species [arsenite (As3), arsenate (As5), MMA, and DMA] were detected using High Performance Liquid Chromatography Hydride Generated Atomic Absorption Spectrometry (HPLC-HGAAS). Conditional logistic regression was used to investigate the effect of arsenic methylation, as measured by the percentage of each urinary arsenic metabolite (%InAs, %MMA, and %DMA), among 900 case-control pairs. Cases were defined based upon a clinical diagnosis of one or more of the following conditions: keratosis of the extremities, spotted melanosis, Bowen's disease, or squamous cell carcinoma. Controls were individuals without any visible skin lesions selected from the DCH catchment area and matched one-to-one on gender, age (within 3 years), and area of residence. Each metabolite was centered at its mean of 12.9%, 13.2%, and 73.9% for %InAs, %MMA, and %DMA, respectively.
The %InAs was not significantly associated with the odds of skin lesions (OR 1.0, 95%CI 0.99–1.02). However, the %MMA was significantly associated with an increased odds of skin lesions (OR 1.03, 95%1.01–1.04) and the %DDM was significantly associated with a decreased odds of skin lesions (OR 0.98, 95%CI 0.98–0.99). Thus, for every 1% increase in MMA above the mean, the odds of skin lesions increased by approximately 2.8%. This finding contributes to the growing body of research that supports the theory that individuals with diminished methylation capacity who are chronically exposed to arsenic have an increased risk of disease.
While reducing exposure must remain the priority for addressing arsenic toxicity, improving nutrition, particularly folate intake which has been shown to improve arsenic methylation, may help lower the risk of negative health effects such as skin lesions amongst exposed individuals.