Pesticides A Toxic Time Bomb in Our Midst

in animal cell cultures exposed to atrazine in concentrations comparable to the federal

drinking-water standard.^34

Certain Populations at Risk

Pesticides such as atrazine pose the greatest risk to the developing fetus, infants,

and children. Developing biological systems are more prone to chemical disruption,

and immature metabolic systems are less able to detoxify pesticides. Children may be

disproportionately exposed to atrazine because they drink more water than adults on

a body-weight basis. Epidemiological and laboratory animal studies suggest that pre-

natal and nursing exposure to atrazine can cause abnormalities in the developing fetus

and newborn offspring. These abnormalities can include intrauterine growth retarda-

tion, low birth weights, and higher rates of prostate inflammation in males.^35

Regulation of Atrazine in Drinking Water

The EPA has set an MCL for atrazine in drinking water at 3 parts per billion

(ppb). Nevertheless, groundwater monitoring has detected the herbicide at concentra-

tions above the MCL in at least ten states. For public drinking-water supplies, regula-

tors determine compliance by averaging quarterly measurements. In agricultural

areas, however, this method can overlook spikes in atrazine levels that occur in spring

and summer and result in short-term exposures to levels significantly above the

standard.^36

Factors that Affect the Fate of Pesticides in Water

Various processes affect the fate of pesticides following an application, disposal, or

spill. The two basic processes are those that transfer chemicals or influence their

movement, and those that degrade or break down chemicals. Water is involved in the

primary transfer processes of runoff and leaching, but is much less involved in the

degradation processes.

Runoff

Runoff occurs when water carries pesticides, either mixed in the water or bound to

eroding soil, to off-target points. Rain carries pesticides from plant leaves to foliage

near the ground and into the soil. The amount of pesticide runoff depends on the

grade or slope of an area, the erodibility and texture of the soil, the soil moisture con-

tent, the amount and timing of irrigation or rainfall, and the properties of the pesti-

cide. Agricultural runoff from crops is a concern because it may contain fertilizer and

pesticides. Agricultural runoff enters our water sources by seeping through the soil to

groundwater or entering streams as surface runoff.

204 | Pesticides

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