Perchlorate in Drinking Water:
Scientific Collaboration in Defining Safety
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Since the mid-1990s, there has been an increasing amount of research effort
aimed at evaluating the potential human health risk of perchlorate (ClO4) because
of its presence at trace levels in some water systems. Concern over potential
effects on the thyroid gland in humans from perchlorate exposure and whether
environmental levels pose a risk to human health have surfaced recently. In
response to this concern, a broad collaborative effort spanning both private
and government sectors has been engaged in extensive toxicological testing of
perchlorate to add to our knowledge about how and under what exposure conditions
perchlorate may cause effects in laboratory animals and in humans. The collaboration
between the U.S. Environmental Protection Agency (EPA), the Department of Defense
(Air Force) and an inter-industry Perchlorate Study Group (PSG) is unique in
its focus on development of state-of-the art science for accurately determining
what constitutes a safe level for humans.
Because of its mission to identify significant public health threats and to
bring sound scientific analysis to environmental health concerns, the American
Council on Science and Health (ACSH) has (a) evaluated the allegations of health
risk from perchlorate as alleged by the Environmental Working Group (EWG); (b)
reviewed the current regulatory process that is ongoing with respect to the
establishment of a safe environmental exposure level; and (c) highlighted some
of the recent scientific studies that have further characterized the toxicity
of perchlorate in both animals and humans.
With respect to the EWG's Report entitled "Rocket Science" which alleges
human health risk from perchlorate in drinking water, ACSH concludes the following:
- The EWG report encompasses
a selective and limited use of the scientific data for perchlorate and does
not represent the totality of our current knowledge regarding its toxicity.
- Many of the claims
of health risk are not supported through the inclusion of scientific references
and as such cannot be construed to represent the scientific facts.
- The EWG report mischaracterizes
the current regulatory efforts underway aimed at defining a safe exposure
level and fails to recognize the scientific process at work.
- The EWG report has
prematurely forecast what it believes to be a safe environmental exposure
level without consideration of the significant amount of toxicological data
that have been generated in the last few years or without regard for the
scientific process at work.
Over the course of the last
10 years, the EPA has worked to define a safe exposure level for perchlorate
in the environment, although a final value has not been established owing to
data gaps for perchlorate.
- In reviewing the history
of the regulatory response in establishing a safe level for perchlorate
in the environment, the ACSH concludes the following:
There has been a concerted effort to identify those studies and data gaps that
would facilitate the establishment of a safe exposure level and significant
testing has resulted in a much improved toxicological database for perchlorate.
There has been a cooperative strategy and effort amongst both government and
industry groups aimed at improving the scientific database for perchlorate for
the protection of public health.
As a result of the extensive toxicological testing, the EPA is expected to release
its proposed Reference Dose (RfD, the safe exposure level for humans) in 2002,
at which time all interested parties and stakeholders can publicly comment on
In reviewing the recent scientific studies that have enhanced our knowledge
of perchlorate's toxicity, ACSH concludes that:
- Both animal and human
studies have appreciably contributed to our understanding of dose-response
relationships for perchlorate such that the process of defining a protective
RfD will be accompanied by less uncertainty and increased confidence.
- Both animal and human
studies have contributed to our knowledge about the mechanism of action
by which perchlorate exerts toxicity and under what exposure conditions.
This knowledge will aid in the identification of sensitive subpopulations
and in our increased ability to set a safe level for all humans.
It is the intent of this
ACSH report to provide readers with a perspective on how the concern over perchlorate
arose, what the regulatory response has been over the last 10 years, and how
the scientific process can be extremely beneficial in establishing safe exposure
levels for humans in order to safeguard public health.
- Because the number
and types of toxicological studies that have been conducted for perchlorate
has increased significantly, there is less uncertainty that accompanies
the establishment of a safe exposure level and as such, the need for conservatism
in the absence of knowledge has been reduced.
downloading the full report (in Acrobat .pdf format, 96 K),
please go to ACSH home page http://www.acsh.org/
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