poisoning of nontarget organisms as well as the danger involved in low-level flying.
Aerial dispersal of pesticides in CONUS by military agencies must be justified in terms
of necessity on an epidemiological basis, clearly demonstrated economy over other
measures, and impracticability of other methods. In making a decision on whether to
employ aerial dispersal and, if so, how to employ it, the following factors should be
(1) Wind. Aerial dispersal is most accurately controlled when there is no
wind. For practical considerations, any wind greater than 7 to 8 miles per hour should
be considered excessive.
(2) Temperature. The most favorable condition of temperature for aerial
dispersal is what is commonly referred to as a lapse condition. This is a normal
condition in which the air at ground level is warmer than the air at higher altitudes.
Under a lapse condition, particles in the atmosphere tend to fall vertically with a
minimum amount of dispersion. The reverse of this condition is known as a
temperature inversion. In an inversion condition, the air at the earth's surface is colder
than the air above it. The result is that the cool air is trapped under the warmer air and
air movement is lateral rather than vertical. Aerial distribution should be avoided under
an inversion condition as the pesticide particles may fall laterally far from the point of
(3) Formulation. Dusts, being lighter than liquids, carry further and are
thus harder to control -- particularly under turbulent weather conditions.
(4) Droplet/particle size. The size of the spray droplet or dust particle will
also affect the distance that a pesticide will travel before reaching the ground.
Unfortunately, this characteristic is often a function of equipment design and not under
the control of the operator.
(5) Dust in the atmosphere. Liquid chemical droplets adhere to dust
particles in the atmosphere and may be carried for great distances. Therefore, aerial
dispersal should be avoided under dusty conditions.
b. Water. The major pathway of pesticides into the water environment occurs
through direct application to surface waters and surface runoff. The major recipients of
surface water are streams, lakes, and coastal waters. Some pesticides find their way
into ground waters, but the contribution of pesticides to a ground water source from a
surface water source or from raindrops through the air is minute. There is little danger
of contamination of a public well water supply by pesticides, but a number of instances
of contamination of private wells have been reported -- usually by carelessness in
handling the chemicals near the wells. On the other hand, public water supplies
obtained from surface waters have frequently been found to be contaminated. The
removal of pesticides by water treatment processes varies with individual pesticides and
concentrations thereof. In general, however, it is more difficult to remove the low levels