Regulation of Perchlorate


California has set a state Public Health Goal (PHG) for perchlorate of six ppb, but because there is still disagreement among the medical, scientific and regulatory communities on the science, state regulators will carefully review the findings of the NAS panel when they are released and revise the PHG as necessary.

The disagreement comes, in part, from a University of California (UC) peer review of California's draft PHG, and particularly a risk assessment upon which the draft was based, issued in 2002. Three UC researchers conducted the peer review. Each disagreed with Cal/EPA's Office of Environmental Health Hazard Assessment and one another on how the state should proceed.

If California acts before the review by the National Academy of Sciences is complete, the result could be a drinking water standard that is overly restrictive and has staggering economic for Californians, while offering no public health benefit.

The PHG is only a goal, not a standard, but now that it has been set, California can move forward to consider setting a formal standard, also known as a Maximum Contaminant Level (MCL), for perchlorate. Importantly, the PHG is supposed to be based on the best and most current science available. In light of the disagreement among the UC peer reviewers, it is appropriate that California will consider the NAS findings and revise the PHG as necessary.

Currently, if the level of perchlorate in drinking water exceeds 6 ppb — the "Action Level" set by the California Department of Health Services (DHS) — water system operators are required to notify local government agencies. The DHS also recommends that consumers be notified, and that the drinking water source be removed from service, if perchlorate is found at levels 10 times the Action Level. Some drinking water purveyors have already stopped serving drinking water that contains any amount of detectable perchlorate, thereby preventing potential exposures.

Next steps for California:

    Establish a state drinking water standard, following review of the NAS findings and revising the Public Health Goal as necessary. State law requires that this standard be as close to the Public Health Goal as economically and technologically feasible, but does not require the state to investigate the science any further.

Consequences of Unnecessarily Strict Regulations

To best protect the public, regulatory standards should be based on the best available science.

The California Environmental Protection Agency, in recently setting its Public Health Goal at 6 ppb, emphasized that the state would take into account the forthcoming report of the National Academies of Science on health effects of perchlorate. In so doing, the agency committed to seeking the best available medical and scientific information in its consideration of a drinking water standard.

It is clearly important that standards be set at a level low enough to assure public health protection, including a margin of safety. It is also important that regulatory standards not be set at an unnecessarily low level.

U.S. EPA and the State of California are considering drinking water standards for perchlorate that are far more restrictive than what credible scientific research suggests is necessary to protect human health.

Unnecessarily restrictive regulatory standards-that is, standards more restrictive than indicated by the best available scientific data-could result in a number of direct and indirect adverse consequences. The economic costs potentially could be staggering - especially in the Colorado River Basin states of California, Nevada, and Arizona - resulting in citizens incurring significant expenses in their capacities as taxpayers, ratepayers and consumers. Water purveyors and those who rely on them for personal and business usage have particular reason for concern.

Some people suggest that economic costs imposed by a standard that is more stringent than indicated by the best scientific data would nonetheless be justifiable; they assume that any reduction in pollution is beneficial. However, all risks are not equal; greater resources should be applied greater risks. Regulatory decision-makers routinely must choose between one risk and another, in the same way that legislatures, companies and families must set budget priorities. Moreover, additional increments of reduction tend to have dramatically increasing costs-inevitably diverting resources that would otherwise be available for more significant environmental and health challenges, or other needs (e.g., retrofitting of facilities for protection against terrorist incidents; pre-natal care, etc.).


Reference Dose (RfD): The amount of a particular substance in drinking water that U.S. EPA considers "safe" if consumed every day.

Public Health Goal: California's version of the U.S. EPA's Reference Dose, it is the level of a particular substance in drinking water that Cal/EPA considers safe for daily consumption.

Maximum Contaminant Level (MCL): Drinking water standard, or how much of a particular substance is allowed in drinking water. The drinking water standard must be as close to the reference dose as possible, while taking into account economic and technological feasibility.


U.S. Environmental Protection Agency

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