Drift, sprays/dusts

Dusts are the simplest means of insecticide dispersal and are appHed by introducing the finely divided carrier, with particles of 0.5 ndash 3.0 p.m in diameter, into a moving air stream. In comparison with sprays, dusts adhere poody to surfaces and cause serious drift problems away from the treatment area. 

Granules are mostly used for application to soil and water. They are useful in variety of insect control situations. Examples include application to the seed bed for seed protection, broadcasting and tilling into the soil for soil insect control, application to growing crops for either foliar or soil insect control, and application to ponds for mosquito control. They are easy to apply and are not as likely to drift as dusts or spray. They have less tendency to adhere to foliage and can thus be applied to soil surface through a canopy of leaves. Researchers often find that when different formulations of a toxicant are compared, the granules perform better. 

Biocides should not be present in water used for aquaculture. Sources of herbicides and pesticides are mnoff from agricultural land, contamination of the water table, and spray drift from crop-dusting activity. Excessive levels of phosphoms and nitrogen may occur where mnoff from fertilized land enters an aquaculture faciUty either from surface mnoff or groundwater contamination. Trace metal levels should be low as indicated in Tables 4 and 5. 

Spray drift is defined for this topic by the National Coalition On Drift Minimization (NCODM) as The physical movement of pesticide through the air at the time of pesticide application or soon thereafter from the target site to any non- or off-target site . Secondary drift, defined by NCDOM as vapor drift or subsequent dust and particle movement after the application , is only partially addressed, although most key principles discussed will still also apply to such secondary movements. 

The danger to domestic animals, including pets, is an important hazard in the use of all newer economic poisons. Drift dusts or sprays from carelessly applied materials may set back the useful development of many valuable chemicals. Only recently have authorities finally decided that we should slow down on the use of DDT on cows until we know more about the occurrence of the chemical in rtiilk, butter, and steaks. Our sportsmen and, incidentally, a major economic factor in our pleasant way of life—the fish, game, and wildlife activities—are part and parcel of the problem of chemical usage in forests and streams. We need continued and expanded investigations of the effects of the newer pesticides on wild life. 

Gerhardt, P. D., Witt, J. M., Summary of Downwind Drift Limits, Comparison of Dust vs. Spray, Pesticide Residue Study, Univ. of Arizona, September 1963. 

Pesticide movement away from the release site in the air is usually called drift. Pesticide particles, dusts, spray droplets, and vapors all may be carried offsite in the air. People who mix, load, and apply pesticides outdoors usually are aware of the ease with which pesticides drift offsite. People who handle pesticides indoors may not realize how easily some pesticides move offsite in the air currents created by ventilation systems and by forced-air heating and cooling systems. 

Lightweight particles, such as dusts and wettable powders, are easily carried by moving air. Granules and pellets are much heavier and tend to settle out of air quickly. Small spray droplets also are easily carried in air currents. High-pressure and fine nozzles produce very small spray droplets that are very likely to drift. Lower pressure and coarse nozzles produce larger droplets with less drift potential. 

USEPA (2001) Draft Registration Notice Spray and Dust Drift Label Statements for Pesticide Products. Pesticide Registration (PR) Notice 2001-X. 

CMorinated pesticides enter the atmosphere primarily through spray drift during application, wind-blown dusts, and volatilization from treated surfaces. Heavy use of chlorinated pesticides generally means that spray drift is the most important means of entry to the atmosphere. In general, application by airplane results in more drift than application by ground equipment, and dusts drift more than sprays. For example, ZDDT particles measuring 2 /rni in diameter drifted about 35 km compared to 70 m for 50 jum droplets (Spencer, 1975). Wind-blown dusts are the most important source of entry to the atmosphere in areas where the use of chlorinated pesticides is either limited or curtailed. The dust source category will continue to contribute substantially to the world-wide redistribution of pesticides, particularly DDT and its derivatives, for many years to come. This partially accounts for the presence of detectable levels of pesticides in the sediments of remote Arctic lakes. 

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