Arsenic is a semi-metal that occurs naturally in rocks and soil, water, air, and plants and animals. It can be further released into the environment through natural activities such as volcanic action, erosion, forest fires, or through human activities.

Agricultural and industrial practices also contribute arsenic to the environment through smelting, mining and coal burning and through the production of paints, dyes, metals, drugs, soaps, and semi-conductors. Wood preservation accounts for nearly 90 percent of industrial arsenic usage in the United States.

Arsenic has been linked to cancer of the bladder, lungs, skin, kidney, nasal passages, liver, and prostate. Non-cancer effects can include thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea, numbness in hands and feet, partial paralysis, and blindness.

The EPA has set the arsenic standard for drinking water at 10 parts per billion to protect consumers served by public water systems from the effects of long-term, chronic exposure to arsenic. This limit was reduced from 50 ppb to 10 ppb in January 2001, with compliance required by January 2006. This decrease in Maximum Contaminant Levels is expected to provide additional protection for approximately 13 million Americans.

For the EPA quick reference guide to the Arsenic Rule see: http://www.epa.gov/safewater/arsenic/pdfs/quickguide.pdf