Special Report on Ingested Inorganic Arsenic
Risk Assessment Forum
Arsenic exposure has long been associated with several different forms of human cancer. The association between inhaled arsenic and an elevated risk of lung cancer is well documented (Enterline and Marsh, 1980; Lubin et al., 1981; Welch et al., 1982; Lee-Feldstein, 1983). Other studies have reported an association between ingested inorganic arsenic and an increased incidence of nonmelanoma skin cancer in a Taiwanese population (Tseng et al., 1968; Tseng, 1977; hereafter Taiwan study) (Appendix A). Also, exposure to ingested arsenic is associated with an elevated but unquantifiable risk for cancer of internal organs (e.g., liver, kidney) in some studies (Chen et al., 1985, 1986).
The U.S. Environmental Protection Agency's Health Assessment Document (HAD) for Inorganic Arsenic (U.S. EPA, 1984a) contained qualitative and quantitative carcinogen risk assessments for both inhalation and ingestion routes of exposure. Several EPA offices raised questions about the assessment for the ingestion exposure, including: the validity of the Taiwan study and applicability of the dose-response assessment to the U.S. population, the interpretation and use of arsenic-associated skin lesions, and the role of arsenic in human nutrition (the essentiality issue).
A Technical Panel was convened by the Risk Assessment Forum to address these issues. In the course of its deliberations, the Technical Panel examined several other issues relating to hazard identification and dose-response assessment for arsenic-induced skin cancer, including some aspects of the pathology of arsenic-associated skin lesions, the genotoxicity of arsenic, the metabolism, body burden, and distribution of this element, and the possibility of threshold effects. The Technical Panels findings are summarized in the Executive Summary (Part II) and detailed in the remainder of this report. Additional technical analyses appear in the five appendices.
A draft of the Technical Panels Special Report was peer reviewed at a public workshop held in Hunt Valley, Maryland, on December 2-3, 1986. The Panel revised its report in line with many helpful peer review comments andpresented a revised document to the Risk Assessment Forum on March 27, 1987. The Forums comments and recommendations have been incorporated.
This report is designated as a Special Report to distinguish this analysis, which is deliberately limited to the skin cancer and nutritional essentiality issues identified above, from comprehensive risk assessments that fullyanalyze all indicated health effects and fully conform with EPAs Guidelines for Carcinogen Risk Assessment (U.S. EPA, 1986; hereafter cancer guidelines). The Special Report addresses many of the hazard identification, dose-response assessment (Appendix B), and risk characterization parameters called for in the cancer guidelines, but it does not fully assess orcharacterize arsenic risks for skin cancer nor does it analyze the othercancers associated with exposure to this element.
U.S. EPA. Special Report on Environmental Endocrine Disruption: An Effects Assessment and Analysis. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, DC, 630/R-96/012, 1997.