Environmental Safety

In addition to protecting the health and safety of consumers, farm neighbors, and farm workers, Dow AgroSciences is committed to finding ways to minimize the environmental impact of its products while still maintaining their effectiveness. We continue to work with regulatory agencies, such as the EPA to protect the environment.

Most pesticides currently registered in the United States and around the world break down relatively quickly in the environment, so they are effective for as long as they need to be for plant protection, but no longer than that, so they have less opportunity to be dangerous to non-target insects and animals.

Regulated Environmental Safeguards

In previous environmental assessments, such as those conducted during FIFRA reregistration, chlorpyrifos was found to have potential negative effects on non-target species, many of them aquatic invertebrates. To address concerns about potential environmental effects the EPA and Dow AgroSciences collaborated to develop the following product label improvements to mitigate environmental risk which have been implemented since the 2002 EPA reregistration decision:

• Decreased application rates for certain crops. Depending on the crop, some application rates were lowered either minimally or significantly, according to the potential for environmental risk posed by chlorpyrifos application.
• Decreased the number of applications allowed. Specifying limits for how often chlorpyrifos could be applied to particular crops further reduced the amount of the product potentially affecting the environment.
• Eliminated or restricted certain uses of the product. Application types for certain crops are limited to a particular form of the product — e.g. granules vs. liquid application, or the reverse, depending on the situation.
• Established no-spray buffer zones around permanent bodies of water. Depending on the application method — aerial application, orchard blast, or ground application — distances of between 25 to 150 feet away from groundwater were established.

Chlorpyrifos in Soil

Chlorpyrifos breaks down relatively quickly in the environment. Soil microbes and a chemical process that occurs when chlorpyrifos comes into contact with water, called “hydrolysis,” detoxify the compound before further breakdown occurs. In alkaline soils, the product’s half-life can be as short as two weeks; in less alkaline soils, its half-life can extend to two months.

Chlorpyrifos also bonds strongly to soil and thereby minimizes runoff effects and leaching into surface water and groundwater. Large-scale field runoff studies have confirmed that even under relatively severe conditions (heavy rainstorms closely following application), generally less than one percent of the applied chlorpyrifos can move off the edge of treated fields through runoff water and eroding soil particles.

Chlorpyrifos in Water

Both laboratory studies and extensive field studies have shown that chlorpyrifos also breaks down quickly in water. In laboratory studies, chlorpyrifos was added to pure water with a neutral pH factor. As with soil, chlorpyrifos’ half-life was about a month — with water and light (photolysis) contributing to its detoxification and breakdown. And, as with soil, more alkaline conditions resulted in faster breakdown — half-life was around two weeks.

In field studies, where samples of natural water from streams and canals were analyzed, chlorpyrifos often broke down significantly faster — as much as 16 times faster. In fact, half-lives in the water of less than one day are typical, due to a combination of breakdown by microbes and plants, evaporation, and bonding with organic matter and sediments.

Chlorpyrifos and Wildlife

So what does this mean for living organisms such as plants and animals? Studies conducted within the last few years are largely reassuring.

Greenhouse and field studies indicate that plants do not take in chlorpyrifos through roots, although they do absorb some of the product through their leaves. Chlorpyrifos is quickly broken down and detoxified on leaf surfaces and in the plant. Dissipation of the product occurs in as brief a time as a single day and as extended a period as 7 days. Therefore, there is less opportunity for wildlife to be exposed to chlorpyrifos by eating the treated plants.

Fish and other aquatic life can absorb chlorpyrifos from the surrounding water. Although the compound is absorbed by the organism’s tissue, it is quickly excreted — so it isn’t stored and accumulated in the fish and doesn’t increase in concentration as it travels up the food chain. Most of the chlorpyrifos in fish, shellfish, and other aquatic life is excreted within half a day to just over two days.

Animals, birds, and insects vary in the routes by which they’re exposed and the speed with which they metabolize it. Many insects — generally the target insects — absorb chlorpyrifos through their body surfaces, at a rate of up to 90% of what they’re exposed to. Some animals, such as rats, can absorb up to 60% of the exposure dose through their skin, whereas humans tend to absorb only 3% of the chlorpyrifos to which their skin is exposed. While some species of bird and small mammal are particularly susceptible to chlorpyrifos, in general the product is metabolized quickly — in a matter of hours — and excreted without harmful effect.

Visit the Endangered Species Act page for more about chlorpyrifos and salmon.