Section III. PESTICIDES AND THE ENVIRONMENT
Pesticides were used for many years, with varying degrees of success, prior to
the development of the synthetic organic pesticide. The widespread use of the
synthetic pesticides began immediately following World War II. DDT was the forerunner
and was accepted by the general public as a panacea to the problem of unwanted
insects. It had been used quite effectively by the military services during the war and in
the subsequent rehabilitation of devastated areas. DDT became a household word --
particularly on the farm. Soon afterward, other synthetic pesticides began appearing on
the market. The new pesticides enjoyed unprecedented popularity until about 1962,
when the pendulum of public opinion began to swing in the other direction. It became
apparent that residues of DDT and other chlorinated hydrocarbons were present not
only in soil treated some years before, but also in various foods, including milk, meat,
fowl, and fish. Traces of pesticides -- principally DDT -- were even being detected in
human tissue. Following 10 years of controversy and investigation, the Federal
Environmental Pesticide Control Act of 1972 virtually ended the use of DDT and sharply
curtailed the use of certain other highly persistant pesticides.
3-11. PESTICIDE PERSISTENCE
When we think of the environmental impact of pesticides, one of our first
considerations is that of pesticide persistence. Persistence is the ability of a pesticide to
retain its toxic properties over an extended period of time in the environment. Although
persistence is a desirable characteristic in the sense that a residual effect is desired to
kill pests over a period of time, this same characteristic can be a serious liability in terms
of accumulations of the pesticide. Although wide variations occur within classes of
pesticides, we can state in very general terms the degree of persistence associated with
a chemical class of pesticides.
a. Chlorinated Hydrocarbons. The chlorinated hydrocarbons, as a group,
are considered highly persistent chemicals. Although they are biodegradable to a
degree, their persistence in the environment is measured in years. Some of them have
shown persistence up to 15 years (massive soil treatment, as in termite control).
Lindane, DDT, and its derivatives are the most persistent. The chlorinated
hydrocarbons are considered our worst polluters.
b. Organophosphates. The organophosphate compounds are considered
nonpersistent. Most of them decompose within about two weeks, although diazinon, the
most persistent of the organophosphates, remains in the soil for about three months.
Carbamates. The carbamates are similar to the organophosphates in their
residual effects. Carbaryl (Sevin), the best known and most extensively used of the
carbamates, has a half-life of about eight days in the soil. This means that every eight