Atmospheric dispersion of current-use pesticides: A review of the evidencefrom monitoring studies

Recently, evidence has accumulated that the extensive use of modern pestici des results in their presence in the atmosphere at many places throughout t he world. In Europe over 80 current-use pesticides have been detected in ra in and 30 in air. Similar observations have been made in North America. The compounds most often looked for and detected are the organochlorine insect icide lindane and triazine herbicides, especially atrazine. However, acetan ilide and phenoxyacid herbicides, as well as organophosphorus insecticides have also frequently been found in rain and air. Concentrations in air norm ally range from a few pg/m(3) to many ng/m(3). Concentrations in rain gener ally range from a few ng/L to several mu g/L. In fog even higher concentrat ions are observed. Deposition varies between a few mg/ha/y and more than 1 g/ha/y per compound. However, these estimates are usually based on the coll ection and analysis of (bulk) precipitation and do not include dry particle deposition and gas exchange. Nevertheless, model calculations, analysis of plant tissue, and first attempts to measure dry deposition in a more repre sentative way, all indicate that total atmospheric deposition probably does not normally exceed a few g/ha/y. So far, little attention has been paid t o the presence of transformation products of modern pesticides in the atmos phere, with the exception of those of triazine herbicides, which have been looked for and found frequently. Generally, current-use pesticides are only detected at elevated concentrati ons in air and rain during the application season. The less volatile and mo re persistent ones, such as lindane, but to some extent also triazines, are present in the atmosphere in low concentrations throughout the year. In ag ricultural areas, the presence of modern pesticides in the atmosphere can b e explained by the crops grown and pesticides used on them. They are also f ound in the air and rain in areas where they are not used, sometimes even i n remote places, just like their organochlorine predecessors. Concentration s and levels are generally much lower there. These data suggest that curren t-use pesticides can be transported through the atmosphere over distances o f tens to hundreds, and sometimes even more than a thousand kilometres. The relative importance of these atmospheric inputs varies greatly. For mounta inous areas and remote lakes and seas, the atmosphere may constitute the so le route of contamination by pesticides. In coastal waters, on the other ha nd, riverine inputs may prevail. To date, little is known about the ecologi cal significance of these aerial inputs.