Subject: Re: toxicity of pesticdes
From: <don@bio-organics.com>
Organization: Bio/Organics Supply Center
Date: 3 Sep 1997 22:47:41 GMT
Message-ID: <MOD$970903.16371@rec.gardens.ecosystems>
References: <MOD$970902.18871@rec.gardens.ecosystems>


"Bill Robinson" wrote:
>
>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
>

If I might add one more little thought to this, many of our
so-called "safe poisons" can react together to form something
considerably more lethal in the garden. This, along with the
idea that pesticides in general cause more damage than they
prevent (by killing friendly predator insects) is a good reason
to look for alternative methods. Actually, just improving the
soil to the point where your plants are healthy enough to
resist insect attacks and diseases is the best solution.

Don Chapman
Bio/Organics Supply Center
Camarillo CA
http://www.bio-organics.com