The former is based on health concerns, while the latter is based on economic feasi-
bility and is the level that is enforceable by law. Currently, the EPA has set standards
for seventy-eight different contaminants, twenty-nine of which are pesticides. That
leaves another 271 pesticide ingredients for which no standards have been set.^40
Even when MCLs have been established, the EPA does not base them on health
factors but rather on economics. As a result, health problems do occur when people
drink water contaminated with pesticides below the ‘‘acceptable’’ level. For instance,
researchers studied Iowa communities served by a reservoir that was contaminated
with 2 parts per billion of the herbicide atrazine, which isbelowthe 3 ppb MCL set
by the EPA. Overall, researchers found twice as many birth defects in communities
that consume pesticide-contaminated water. Heart defects increased threefold, as did
defects of the urinary and genital systems. Limb-reduction defects, arms or legs that
do not develop to their normal length, increased almost sevenfold.^41
Drinking-water standards also do not take into account health effects on the most
vulnerable populations, such as children, the elderly, or people with immune system
compromising diseases, such as AIDS. Moreover, drinking-water standards do not
account for the effects of chemicals in combination when evidence demonstrates that
mixtures of common pesticides—even at so-called low concentrations in drinking
water—are implicated in damage to the nervous, immune, and hormone systems.^42
The point that should be stressed is that treatment of drinking water does not neces-
sarily solve the problem because the technology is designed to remove only certain
chemicals for which an MCL has been established.
Tracking Pesticide Use
In 1996, Congress amended the Safe Drinking Water Act to require the develop-
ment of Source Water Assessment Plans (SWAPs). The amendments were meant to
supplement the traditional approach of relying on water treatment with stronger
efforts to protect drinking-water quality at its source. The heart of the amendment
requires that states undertake more complete reviews of potential contaminants, and
also requires that communities take action to prevent pollution.
To inventory the potential contaminants within a source-water area as required by
SWAPs, communities need detailed information on which pesticides are used, and
where, when, and in what amounts. The information must be site-specific enough so
that water providers can target aggressive pollution prevention efforts to particular
places that are most vulnerable, such as areas with high runoff or with soils prone to
leaching. In turn, the pesticide-use data can help measure the effectiveness of efforts
to prevent pollution.
Detailed information on pesticide use will also help water-monitoring efforts. Water
providers need to know which pollutants to test for, such as pesticides that are used
heavily in a particular source-water area. Testing only for chemicals that have estab-
lished MCLs makes little sense in areas where other pesticides may be heavily used or
where waterways are especially vulnerable to pollution from a particular pesticide.
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