Agriculture Reference
In-Depth Information
C.
PESTICIDE MOVEMENT
Pesticides that move away from the release site may cause environmental
contamination. Pesticides move away from the release site both indoors and
outdoors and may cause harm in both environments. Pesticides move in sev-
eral ways, including:
•
in air, through wind or through air currents generated by ventilation
systems
•
in water, through runoff or leaching
•
on or in objects, plants, or animals (including humans) that move or
are moved offsite.
1.
Air
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 usu-
ally are aware of the ease with which pesticides drift offsite. People who han-
dle 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.
a.
Particles and Droplets
Lightweight particles, such as dusts and wettable powders, are easily car-
ried 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.
The likelihood that pesticide particles and spray droplets will drift offsite
depends partly on the way they are released. Pesticides released close to the
ground or floor are not as likely to be caught up in air currents as those re-
leased from a greater height. Pesticides applied in an upward direction or from
an aircraft are the most likely to be carried on air currents.
b.
Vapors
Pesticide vapors move about easily in air. Fumigant pesticides are in-
tended to form a vapor when they are released. Persons using fumigants must
