Subject: toxicity of pesticdes
From: "Bill Robinson" <roseguy@flash.net>
Organization: Miami, FL, USA
Date: Tue, 2 Sep 1997 05:41:22 -0700
Message-ID: <MOD$970902.18871@rec.gardens.ecosystems>


Troy Coaziahr wrote,

> LD = "lethal dose"
> LC = "lethal concentration"

> The 50 means 50% -- as in that particul;r dose caused 50% of
> the test animals to die.

> LC50 is usally expressed in parts per million (ppm), and oral
> LD50 is expressed in milligrams of the substance per kilogram
> of the test animals body weight.

Troy is totally on target but there are a couple of things to keep in mind
with the LD50 numbers. The method involves the forced feeding of the test
material to laboratory animals. The proceedure is relatively fast,
inexpensive, and reproducable. It is used throughout the pesticide industry
and is consiidered reliable by the various regulatory agencies.

It is a measurement of acute poisoning which is a different
thing than measuring long term effects. It is also a
measurment of toxicity to the test animal which is a different
thing than measuring the environmental impact. Pesticide toxicity is not a
cut and dry issue. The figures need to be considered
in context.

Bill