Question:
something was bothering me about the claims of deaths from various cancers linked to arsenic in water, and the problem is this - the numbers are too small to be statistically significant

Answer: Arsenic exposure can cause a variety of adverse effects. Acute high-dose oral exposure typically leads to gastrointestinal irritations and difficulty in swallowing, thirst, abnormally low blood pressure, and convulsions. Death may occur from cardiovascular collapse at very high doses. . Evidence exists that long-term exposure to high arsenic levels increases the risk of cancer. When exposure is by inhalation, the primary effect is increased risk of lung cancer. When exposure is by ingestion, the clearest effect is increased risk of skin cancer. Evidence also exists that the risk of internal cancer (liver, lung, bladder, and kidney) is also increased through ingestion. . For most people, the most significant route of exposure to arsenic is through food since it is a normal component of diet. Studies by the Food and Drug Administration have found that fish and seafood are higher in arsenic content than any other foods. . Ingestion of drinking water can be a source of arsenic exposure. Several national surveys of drinking water systems have found arsenic in 3 to 39 percent of all samples averaging less than 10 parts per billion. . Arsenic concentrations are generally highest in groundwater. Surface water concentrations also may be at levels of regulatory concern.