Submitted to: Proceedings Workshop on Managing Arsenic for our Future
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2001
Publication Date: November 23, 2001
Technical Abstract: Because of new estimated risks for internal cancers from ingested inorganic As, potential risks from all sources of soil As are being re-evaluated. Arsenic is a natural constituent of soils, plants, and waters, making the development of limits complex. It is clear that high As ingestion in drinking water has caused internal and skin cancers in exposed humans. But the basis for extrapolation of the high dose adverse effects to low dose exposures seems weak to many who have reviewed these data. Perhaps the low soil As limit suggested (0.8 to 3.0 mg As/kg soil) is so extreme that many question the validity of such limits which are lower than background As levels in US soils. The extensive enrichment of soil As by agriculture in previous centuries (orchard, cotton, and potato soils; tick treatment soils), use of Cr-Cu-As-treated lumber, and extensive redistribution of As by Cu and Au mining and smelting, indicates that over 50% of US surface soils would need to be removed, disposed as a hazardous waste, and replace by low As soils (presuming that low As replacement soil will be available). On the other hand, it is likely that As is essential for humans based on research on several species. Crops generally absorb soil As weakly, so the main potential risk from soil As is by ingestion. Fortunately, As in soil has lower bioavailability than presumed by toxicologists considering soil As limits. Monkey feeding studies have found soil As bioavailability to be about 10% of Na arsenate added to the same diet. Soil As risk assessment assumes that an individual consumes soil at the rate of a 2-year-old child for one's lifetime. But testing children who lived in the vicinity of a stack source showed no increase in urinary As resulting from inorganic As intake, until soil As exceeded 40-100 mg As/kg.