The study, commissioned by AWWA, showed that up to 2,200 of the 56,000 U.S. water supply systems would be affected if the allowable level of arsenic were lowered from 50 ppb to 10 ppb. Arsenic occurs naturally in the environment. It is added to the environment by weathering of rocks, burning of fossil fuels, smelting of ores and manufacturing. It is widely distributed in nature and is mainly transported in the environment by water. The highest exposure to arsenic is in drinking water from wells as opposed to areas, including most urban areas, that get drinking water from lakes and streams, officials said.
Arsenic exposure can cause a variety of adverse effects.
Evidence exists that long-term exposure to high arsenic levels increases the risk of lung cancer, skin cancer and other internal cancers. Although the most significant route of exposure to arsenic is through food, drinking water can be a significant source of arsenic exposure.