[CPEO-MEF] EPA memo reaffirms 4-18 ppb interim perchlorate standard

[Lenny Siegel <lsiegel@cpeo.org>]

On  January 22, 2003, Marianne Lamont Horinko U.S. EPA Assistant
Administrator in the Office of Solid Waste and Emergency Response
(OSWER), signed a memo designed to clarify the status of EPA's position
on cleanup standards for perchlorate in water. Horinko reaffirmed the
applicability of the agency's June 18, 1999 Interim Guidance, in which
EPA's Office of Research and Development (ORD) "recommended that Agency
risk assessors and risk managers continue to use the standing
provisional reference dose ('RfD') range of 0.0001 to 0.0005 mg/kg-day
for perchlorate-related assessment activities." This translate into
provisional clean-up action levels ranging from 4 to 18 parts per
billion (ppb).

Based upon ongoing health assessment activities, Horinko suggests that
risk assessors and managers "carefully consider the low end of the
provisional 4-18 ppb range." The document states, "the 4 to 18 ppb range
is considered to be protective based on recent, ongoing analyses and
taking into account the most sensitive receptors, and therefore no
additional adjustment for childhood exposure is needed."

Though EPA might determine a final reference dose within a few months,
it may be years before it establishes a Maximum Contaminant Level (MCL)
for perchlorate. Horinko's memo describes that process in detail.

The memo explains what it expects EPA staff to do until new guidance is
provided: "In selecting the appropriate cleanup level at specific sites,
the regions should consider the factors that are typically addressed in
setting groundwater cleanup levels, such as practicability, the
reliability of exposure data, whether the groundwater is used as a
source of drinking water, as well as other routes of exposure. Before a
region, for site-specific reasons, chooses a cleanup level either below
or above the 4 to 18 ppb range, it must consult with OSWER, ORD, and OW
[EPA's Office of Water]."

In other words, EPA is discouraging the use of the more stringent 1 ppb
standard, which is based upon the new, draft health assessment. Because
the legal process is long and complex, EPA is sticking with the less
stringent range, even though it appears to be based on less scientific
review than the new, draft assessment.

The higher numbers are unlikely to influence dramatically the
installation of remedies at sites with perchlorate concentrations at or
above the 4 to 18 ppb range, but it could delay sampling and analysis at
sites at the lower end of that range, or below. That is, it could wipe
them off the map.

This appears to be a short-term victory for perchlorate polluters,
including the Department of Defense. However, assuming the current
scientific conclusions hold up through the remainder of the review
process, it means that they will have a larger mess to deal with later.
Contamination will have spread. It will be necessary to start cleanup
project from scratch. More water will be unsafe to drink.

Lenny
-- 


Lenny Siegel
Director, Center for Public Environmental Oversight
c/o PSC, 278-A Hope St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/961-8918
<lsiegel@cpeo.org>
http://www.cpeo.org

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