An epidemiologic study of a community shows an increased incidence of basal cell and squamous cell carcinomas in adults. These lesions are distributed predominantly on palms and soles. Analysis of groundwater pumped from wells for drinking shows increased levels of heavy metal used in pressure-treated lumber (with a greenish hue), insecticides, and herbicides. Which of the following metals is most likely implicated by this study?

Chronic exposure to arsenic-containing compounds can increase the risk for nonmelanoma skin cancers in a distribution different from those linked to the most common cause, ultraviolet light exposure. Beryllium inhaled as a gas can produce acute toxicity to the respiratory tract; chronic exposure can produce sarcoid like granulomas. Cadmium toxicity can lead to renal tubular necrosis, osteopenia, and chronic pulmonary disease. Lead toxicity acutely produces renal and gastrointestinal damage, and chronically it causes anemia, neuropathy, and encephalopathy. Mercury poisoning leads to central nervous system damage.