Pesticide Toxicity

Background

The environmental movement was catalyzed by Rachel Carson's (1962) book, Silent Spring. The title wasbased on her thesis that the biomagnification of pesticides in avian food chains would lead to the demise of song birds. Her concerns were based on studies which showed that pesticides designed to exterminate insects (insecticides) were being bioaccumulated in food chains to toxic levels in higher trophic levels. This toxicity was first recognized in birds, since they were at the top of most insect food chains.

However, she also suggested that tragedy could be averted with the development of more responsible pesticide management practices:

Through all these new, imaginative and creative approaches to the problem of sharing our earth with other creatures there runs a constant theme, the awareness that we dealing with life - with living populations and all their pressures and counter-pressures, their surges and recessions. Only by taking account of such life forces and by cautiously seeking to guide them into channels favorable to ourselves can we hope to achieve a reasonable accommodation between the insect hordes and ourselves.

The classic example of the adverse effects of pesticide biomagnification is DDT in pelicans and peregrine falcons. There are still concerns that DDT may be harming the Caspian tern population at Moss Landing, which appear to be accumulating DDT from contaminated sediments in Elkhorn Slough. These cases illustrate the inherent complexity of determining the adverse ecological effects of any pesticide.

The four primary factors determining the potential adverse effects of a pesticide are:

inherent toxicity
stability
solubility
absorptivity
Characterization

Types of pesticides may be characterized by their "target" organism

herbicide - weeds
insecticide - insects
arachicides - spiders
rodenticide - rodents

Types of pesticides may also be characterized by their chemical formulation:

 

References

Carson, R. 1962. Silent Spring. Houghton Mifflin, Boston, MA, pp. 368.

Chambers, J.E. 1994. Toxicity of Pesticides. In: Basic Environmental Toxicology ( L.G. Cockerham and B.S. Shane, eds.), CRC Press, Boca Raton, pp. 185-198.

Metaclf, R.L. 1981. Insect control technology. In: Encyclopedia of Chemical Technology, Volume 13. Wiley-Interscience, New York, NY. pp. 413-485.

 

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