Conclusions

The combined results from the local, regional, and national monitoring studies indicate that a wide variety of pesticides are present in the atmosphere. Nearly every pesticide that has been investigated has been detected in air, rain, snow or fog throughout the country at different times of the year. And, there is ample evidence that some long-lived pesticides used in one area of the country migrate through the atmosphere and are deposited in other areas of the country, sometimes in areas where pesticides are not used. The atmosphere is an important part of the hydrologic cycle that can transport pesticides from their point of application and deposit them in unintended areas. Average annual concentrations of pesticides in air and rain are generally very low, although elevated concentrations may occur during periods of high use, usually in the spring and summer months. The environmental effects of long-term occurrences of low levels of pesticides in the atmosphere are not yet well understood.