It is time for the federal Environmental Protection Agency to
set a safe drinking-water standard for perchlorate. The nation
cannot afford to wait around for EPA action while perchlorate
pollution threatens public health.

During her visit to Riverside Tuesday, Senator Dianne Feinstein
pledged to introduce legislation that would direct the EPA to
set the national drinking-water standard without delay.

Feinstein's course is correct. There is no good reason to drag
the process out. The EPA already has a National Academy of
Sciences study that set a safe total intake level of perchlorate
for adults: the equivalent of 24.5 parts perchlorate per billion
parts of water a day. That provides a solid basis for developing
national standards.

The scientists' report, however, sets a daily perchlorate dose
for all sources, not just water. Since perchlorate has been
found in milk, lettuce and even breast milk, the safe intake
from water will have to be less than 24.5 parts per billion.

California is working toward a safe drinking-water standard for
the chemical, based on the state's goal of 6 parts per billion.
That number may change when the state's analysis of the Academy
of Sciences report comes out, as soon as this week. Finalizing a
state standard will boost efforts to clean up the 58 contaminated wells in Riverside and San Bernardino counties.

But a state standard will only apply in California, and perchlorate contamination has also emerged in 34 other states. And the chemical shows up in Colorado River water, which flows to several states, including California - another dynamic that requires a national response.

The toxin, which can harm thyroid functions that govern growth
and metabolism, is used in manufacturing explosives and rocket
fuel. Because the federal government is the primary customer of
products with perchlorate, Washington must help finance the
cleanup and ensure that the actual polluters - primarily defense
contractors - also help pay.

An EPA standard would give regulatory force to the cleanup
drive, and remove an excuse for delay. But until the agency sets
a benchmark, cleanup efforts will lag, and the public health
threat will grow.