GENERAL SECTION

Reduced Arsenic Drinking Water Standard
Implications for Site Assessment

INTRODUCTION
The U.S. Environmental Protection Agency (USEPA) recently removed its proposed final rule on arsenic for further review. The proposed final rule would have reduced the drinking water maximum contaminant level (MCL) from 50 to 10 ug/l and would have presented a substantial compliance issue for many drinking water suppliers, particularly small distributors or those in areas with natural background levels above the proposed standard. The proposed reduction creates potential health versus cost benefit issues requiring scientific and social-economic analyses. In addition, a complementary environmental issue is raised, which involves adequate and appropriate investigation of site conditions for identifying arsenic as a potential contaminant of concern relative to the reduced standard.

BACKGROUND
Arsenic is one of eight Resource Conservation and Recovery Act (RCRA) and one of thirteen priority pollutant metals. As such, it is commonly analyzed for when assessing sites with known usage of metals or of unknown or incompletely known historic operations. Arsenic occurs naturally in rocks, soil, water, air, plants, and animals. It is released into the environment through natural activities such as erosion, volcanic action, biodegradation, forest fires, or through human activities. Industrial uses of arsenic include wood preservatives, paints, dyes, metal compounds, drugs, soaps, and semi-conductors. Historically, it was used in embalming. Agricultural, mining, and smelting operations also release arsenic into the environment.

POTENTIAL HEALTH RISKS
Toxic effects from arsenic may result from short-term or long-term exposure depending on dose and duration. Various studies link arsenic ingestion to cancerous effects on the skin, bladder, lungs, kidneys, nasal passages, liver, and prostate. Non-cancerous effects have been linked to cardiovascular, pulmonary, immunological, neurological, and endocrine systems. The existing MCL was designed to be protective of potential short-term higher concentration exposures. The proposed MCL was expected to address the potential long-term lower concentration concerns from ground water, which has been the recent focus and debate. A well-known longstanding fact is that naturally occurring (i.e., non-contaminant) background levels of arsenic are commonly above potential levels of concern in many parts of the country. Consequently, careful consideration should be given when investigating a site to determine whether arsenic should be listed as a potential contaminant of concern.

INVESTIGATION AND EVALUATION
Arsenic investigation may be required by the particular regulatory framework, which governs the site. If not, a thorough understanding of current/historic site operations may justify including or excluding arsenic from the list of contaminants to be tested. Site justification for testing may include: known use of arsenic-bearing compounds; presence of operations that are known to typically use arsenic-bearing compounds (e.g., wood preserving, glass or pesticide manufacturing, smelting); or use of compounds, which may serve to concentrate existing arsenic if released to the environment (e.g., acids or bases). Site uses that do not include the potential for creating an arsenic issue may be used as justification for excluding testing for arsenic. When arsenic is tested for, comparative analyses such as background testing may be necessary to assess whether arsenic may be a contaminant or naturally occurring. If a contaminant, arsenic may require ground water treatment through precipitative, membrane, or adsorptive processes, or ion exchange, or other alternative technologies to attain the MCL or other applicable standards. Soil treatment may be achieved through removal or in situ stabilization processes. Treatment to a lower standard will be longer and more costly, if necessary.

SUMMARY
Arsenic is a commonly detected substance with serious health risks and significant potential implications for site assessment. To discuss whether arsenic may be an issue at a particular site, please contact Michael Woodruff, Maria Vieth, or Dan Woody at (513) 489-2255 or (800) 229-1443 or by e-mail at mlw@paynefirm.com, mrav@paynefirm.com, or dtw@paynefirm.com.