Pesticides A Toxic Time Bomb in Our Midst

Better information on pesticide use will also be extremely helpful in protecting pri-

vate domestic wells and other water systems that are not subject to current drinking-

water rules.

Prevention Is Key

The most complete story of trends in response to regulatory action and reduced pesti-

cide use is the decline in organochlorine pesticide concentrations that followed reduc-

tions in use during the 1960s and bans on uses in the 1970s and 1980s. Concentrations

of total DDT levels in fish, for example, decreased rapidly from the 1960s through the

1970s, and then more slowly during the 1980s and 1990s, as documented by data from

the U.S. Fish and Wildlife Service and the National Water Quality Assessment

(NAWQA) Program. Just as notable as the declines, however, is the finding that persis-

tent organochlorine pesticide compounds still occur at levels greater than benchmarks

for fish-eating wildlife in many urban and agricultural streams across the nation.

In contrast, NAWQA findings show that concentrations of relatively mobile and

short-lived pesticides in stream water respond more rapidly to changes in use than

the less mobile and more persistent organochlorine insecticides. For example,

increases in acetochlor and decreases in alachlor are evident in streams in the Corn

Belt, where acetochlor partially replaced alachlor for weed control in corn beginning

in 1994. The changes in use were reflected quickly in stream concentrations, gener-

ally within one to two years. Similarly, concentrations of diazinon decreased signifi-

cantly from 1998 to 2004 in five of seven urban and mixed-land-use streams sampled

in the Northeast, consistent with the EPA-mandated phase-out of nonagricultural

uses of diazinon that began in 2002.

Long-term and consistent data for assessing trends are essential for tracking water-

quality responses to changes in pesticide use and management practices, for providing

early warning of unanticipated problems, and for updating and improving models.

Long-term monitoring is particularly important for assessing the occurrence of pesti-

cides in groundwater and the occurrence of persistent compounds in streams because

concentrations change slowly, sometimes taking decades to respond to changes in use.^43

There is one final caveat. The best protection against drinking-water contamina-

tion by pesticides isprevention.

Pesticides in the Soil

Sometimes I couldn’t stand how my eyes were watering and my throat hurt;

I couldn’t stand the gas. I would run outside the field to get some air. Now,

I can’t breathe well, and my vision is blurry.

—Jorge Fernandez^44

Introduction

Pesticides are applied to the soil or to a crop. Many techniques can be used to

apply a pesticide depending on the type of formulation, the timing of application,

208 | Pesticides

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