Pesticides Used in Forestry and Their Impacts on Water Quality
Approximately 2.1 billion kg active ingredient (a.i.) of pesticides are used in the US annually. Of the 890 a.i.s registered, 20 account for more than 95% of the pesticide used in forest vegetation management. Forest vegetation management, in the broader context, includes such activities as plant protection from animal, insect, bacterial, and fimgal damage. It also includes pesticideuses fornoxious weedcontrol, coniferand hardwood culture, and improvement ofrecreational areas and wildlife habitat. Pesticide use is most intensive around home and gardens, followed by agricultural land, governmental and industrial land, and is least intensive on forest land. The most extensive use is on agricultural land. Contamination of surface and ground water have been monitored and observed to occur at relatively low levels. Maximum pesticide concentrations observed in water have been much lower than the maximum levels which EPA considers safe forconsumption on a daily basis over a lifetime (HAL). Some studies have applied herbicides at several times the labeled rate directly to surface water in research studies. In some of these studies maximum herbicide concentrations observed in ephemeral to first-order streams exceeded the lifetime HAL, but were ephemeral lasting only a few hours and the highest concentrations did not exceed EPA's 1-day HAL. Even with the wide spread use of pesticides in North America, those typically used in vegetation management programs have not been identified in surface or groundwaterat sufficiently high concentrationsas to impair drinking water quality. Their rapid break-down by physical, chemical, and biological routes coupled with current use patterns precludes the development of significant water contamination problems unless they are applied directly to water. Therefore, their use should be carefully planned and all agency, local, state, and federal laws should be followed. It is especially important to follow all label directions because pesticide labels are legal documents specifying federal laws pertaining to their use. Best management practices should be carefully adherred to and use around drinking watersupplies should be avoided, except where permitted by the label. Wherever pesticides are used, precautions should always be taken to protect drinking water sources from contamination.