Agency to Regulate Perchlorate

• Author: Nancy Stoner
• Position: Assistant Administrator in the Office of Water at the U.S. Environmental Protection Agency
• Pages: 53-53

NOVEMBER/DECEMBER 2011 ❧ Page 53

Copyright © 2011, Environmental Law Institute®, Washington, D.C. www.eli.org.

Reprinted by permission from The Environmental Forum®, Nov./Dec. 2011

Th e F o r u m

Agency to

Regulate

Perchlorate

N S

L

ast February, EPA Ad-

ministrator Lisa Jackson

announced the agency’s

decision to regulate per-

chlorate in drinking water

to better protect public health for

millions of Americans. Perchlorate is

a naturally occurring and man-made

chemical that is used to produce

rocket fuel, reworks, ares, and

explosives. Perchlorate can also be

present in bleach and in some fertil-

izers. Research indicates perchlorate

may disrupt the thyroid’s ability to

produce hormones that are critical

to developing fetuses and infants.

e administrator’s decision is

based on an extensive review of

the best available science. e Safe

Drinking Water Act requires EPA to

promulgate a drinking water regula-

tion, if EPA determines that a con-

taminant meets three criteria. First,

the contaminant may have an ad-

verse eect on the health of persons.

Second, the contaminant is known

to occur or there is a substantial

likelihood that the contaminant will

occur in public water systems with

a frequency and at levels of public

health concern. ird, in the sole

judgment of the administrator, regu-

lation of such contaminant presents

a meaningful opportunity for health

risk reduction for persons served by

public water systems.

Based on evaluation of the avail-

able peer reviewed science on per-

chlorate health eects, EPA deter-

mined that the chemical may have

an adverse eect on the health of

persons by inhibiting the transport

of iodide into the thyroid, resulting

in a deciency of iodide. yroid

hormones play an important role

in the regulation of metabolic pro-

cesses throughout the body and are

also critical to developing fetuses

and infants, especially with respect

to brain development. Because the

developing fetus depends on an ad-

equate supply of maternal thyroid

hormone for its central nervous

system development during the rst

and second trimester of pregnancy,

iodide uptake inhibition from low-

level perchlorate exposure has been

identied as a concern in connec-

tion with increasing risk of neurode-

velopmental impairment in fetuses

of hypothyroid mothers. Poor iodide

uptake and subsequent impairment

of the thyroid function in pregnant

and lactating women have been

linked to delayed development and

decreased learning capability in their

infants and children.

EPA collected monitoring data

on perchlorate from 3,865 public

water systems from 2001 to 2005

under the agency’s Unregulated

Contaminant Monitoring Regula-

tion, or UCMR. EPA found that

160 (approximately 4.1 percent) of

the public water systems reported at

least 1 detection of perchlorate at or

above the minimum reporting level

of 4 micrograms per liter. To deter-

mine if perchlorate was occurring

at levels of public health concern in

these water systems, EPA compared

the reported drinking water concen-

trations to Health Reference Levels

for perchlorate.

EPA calculated HRLs based

upon the perchlorate Reference

Dose recommended by the National

Research Council and adopted by

EPA in 2005. (e RfD is an esti-

mate of a daily oral exposure that is

likely to be without an appreciable

risk of adverse health eects.) EPA

accounted for the dierences in

body weight, drinking water con-

sumption, and the amount of per-

chlorate in the diet at 14 dierent

stages of life to calculate the HRLs

that range from 1 microgram per

liter to 47 micrograms per liter.

ese HRLs are concentrations

of perchlorate in drinking water that

may result in total perchlorate expo-

sures (from food and water) greater

than the RfD for individuals at each

life stage. Given the range of poten-

tial alternative HRLs and the occur-

rence of perchlorate in water systems

above these levels, EPA determined

that perchlorate is known to occur

or there is a substantial likelihood

that it will occur with a frequency

and at levels of public health con-

cern.

EPA estimated the population

served by public water systems

(PWSs) monitored under UCMR

for which the highest reported per-

chlorate concentration was greater

than thresholds ranging from 4 to

23 micrograms per liter. For ex-

ample, EPA estimated that 5.1-16.6

million people are served by PWSs

that are above the Minimal Risk

Level of 4 micrograms per liter. EPA

determined that a National Primary

Drinking Water Regulation for per-

chlorate could reduce exposures for

these populations to levels below the

range of thresholds and that such

exposure reductions present a mean-

ingful opportunity for the reduction

of health risks for persons served by

PWSs.

EPA’s decision initiated devel-

opment of a drinking water stan-

dard for perchlorate which will be

proposed for public review and

comment by no later than Febru-

ary 2013. EPA will continue to

evaluate the science as we develop

the proposed rule which must be

promulgated within 18 months of

the proposal. For more detailed in-

formation about EPA’s decision, see

http://water.epa.gov/drink/contami-

nants/unregulated/perchlorate.cfm.

Nancy Stoner is Assistant Administrator in

the Ofce of Water at the U.S. Environmen-

tal Protection Agency.