Plane Gnu aninia species in ue environment life System were directly or indirectly affected by the .

herbicides. ; i”

.
This chapter briefly evaluates the available evidence concerning the environmental impact of —

herbicide use. Particular attention is focused on residues in ait, water, soil, and Organisms, as well

as environmental effects related to crop, aquatic, industrial, and conservation uses. Emphasis is

placed not only on the identification of ecological consequences but also on Possible alternatives

and less hazardous usage of herbicides. a :

SOURCES AND MOVEMENT OF HERBICIDES IN THE ENVIRONMENT eo

The environmental contamination of target and nontarget areas depends on (1) toxicity of
herbicide, (2) biomagnification, (3) persistence, (4) amount used, (5) application method, and
(6) movement. Although the toxicity of herbicides to animals varies widely, herbicides as a class
are less toxic than insecticides. Biomagnification occurs primarily in plants, which can be a hazard,
but seldom in animals. Persistence increases the chances of a herbicide’s becoming a pollutant.
This is because the longer a material remains in the environment, the greater the opportunity for
the chemical to be a problem within the target area or to move out of the treated area and become
a hazard elsewhere. Se - :

In terms of the amount used, the pollution problem is clear and needs no explanation. Appli-
cation methods determine the amount of herbicide used and the extent of environmental contami-
nation. Of major concern is the extensive use of aerial application: 15 to 20 percent of all
agricultural herbicides is applied by aircraft (USDA, 197 2). _Akesson and Yates (1971) report
that spray recoveries from aircraft applications may be as low as 25 to 30 percent of the amount
applied, Widespread drift effects from aircraft applications have cccurred, for example, in
California” Propanil was applied to rice and injury to fruit trees was observed about 55 miles
downwind (Akesson, 1971). — :

Airborne concentrations harmfui to nontarget crops‘are most frequently due to drift at the
time of application of the herbicide to the target. Usually residues on plants contaminated from
drift are far lower than those on the target species of plants; however, sensitive plants, such as
cotton and grapes, are particularly vulnerable to 2,4-D and, under rare weather circumstances, may
be damaged by residues as much as 15 miles from the point of application. However, damage most
frequently occurs within 500 feet (Van Middelem, 1966). .

Akesson, N. B., November 1971, personal communication. ; .

Akesson, N. B., Wilce, S. E., and Yates, W. E., 1971. “‘Atomization Contro! to Confine Sprays to
Treated Fields,” Paper 71-662, Annual Meeting of the American Society of Agricultural
Engineers, December 7-10, 1971, Chicago.

Akesson, N. B., Yates, W. E., 1971. “Atomization Control to Confine Sprays to Treated Fields,”

"Paper No. 71-662, Annual Meeting of the American Society of Agricultural Engineers,
December 7-10, 1971, Chicago.

Akesson, N. B., Yates, W. E., and Christensen, P., 1972. “Aerial Dispersion of Pesticide Chemicals
of Known Emissions, Particle Size and Weather Conditions,” paper presented at the 163rd
National Meeting of the American Chemical Society, Boston.

Anderson, G. R., and Baker, C. O., 1950. Agron. J., 42, 456.

Anderson, W. P., Richards, A. B., and Whitworth, J. W., 1969. Weed Set., 16(2), 165,

Anonymous, 1970. Herbicide Handbook of the Weed Society of America, 2nd ed., W. F. Humphrey
Press, Inc., Geneva, N.Y. .

Anonymous, 1971. Aquatic Herbicides (privileged source).

Applegate, V. C., Howell, J. H., Hall, A. E., dr., and Smith, M. A., 1957. Toxicity of 4,346 Chemi.
cals to Larval Lampreys and Fishes, Special Scientific Report, Fisheries No. 207, U.S. Fish and
Wildlife Service, Washington, D.C. ‘

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