Analytical capability is only one aspect considered in setting an MCL, so the MCL is not set purely on the basis of the lowest value that can be measured. All approved analytical methods, when revised with the proposed modifications, should be able to meet the PQL and remain on the approved list of methods. The PQL derivation will be peer reviewed. People vary in their metabolic ability to excrete arsenic, and animals respond differently according to species. Noncarcinogenic effects include effects on the cardiovascular system, gastrointestinal tract, and diabetes.
Studies confirm skin, bladder, and lung cancer.
A stakeholder noted that a 1983 NAS report said that arsenic was an essential nutrient. The 1999 NRC report has not determined arsenic to be an essential nutrient, even though some forms are used as a growth promoter for animals. A form of arsenic is being used to treat leukemia. EPA's risk characterization will be done in the fall. A stakeholder wanted EPA to make the NRC report available for free.