A lapse condition is one in which the air at ground level is warmer
than the higher-level air.
When the air at higher altitudes is warmer than at the surface, this is
known as a temperature inversion. When a temperature inversion exists, there is lateral
as well as vertical air movement, causing particles to drift far from the target area.
(2) Wind. Wind speeds greater than 8 miles per hour are generally
considered unfavorable for pesticide spraying.
(3) Dust. Dusty conditions are unfavorable for pesticide spraying because of
the tendency of the chemicals to adhere to the dust particles and be carried long
(4) Droplet size. Smaller droplets, being lighter, will carry farther with the
wind than will larger, heavier droplets. This factor is largely a matter of equipment
(5) Formulation. The type of formulation being used is also a factor in
pollution by the air route, since dusts are lighter and will carry farther than liquids.
d. Water Route. The water route is probably the most important means of
pesticide pollution, since virtually everything, which reaches the ground, is subject to
runoff with rainfall.
Neither vertical movement into ground water sources (wells and springs)
nor washing of pesticide particles in the atmosphere by raindrops is an important
consideration in this respect.
The vast majority of water pollution occurs by direct application of
pesticides to the water by aerial spraying or through surface runoff.
This source of pollution cannot be eliminated, but it may be minimized by
applying pesticides only when necessary and then only in recommended strengths and
e. Soil Route. The soil provides an important source of pesticide
During dry weather, dusty soil that has been subjected to pesticide
treatment is easily picked up by gusts of wind and transported to other areas.
In addition, the soil affords a medium in which pesticides may persist for