Subject: 
            Re: Roundup
       Date: 
            4 Sep 1997 00:14:46 -0400
       From: 
            Troy Coziahr <troyc@geneseo.net>
Organization: 
            a Digital Internet AlphaServer Site
 Newsgroups: 
            rec.gardens.ecosystems


> > 
> > BTW  Does anyone know what means "the 96-hour LC50 was 8.3 mg/l with
> > Roundup and 38 ppm with glyphosate" or " The acute oral LD50 in the
> > rat is 5,600 mg/kg." ?  Presumably LC50 is some sort of statistical
> > measure.
> 
> LD = "lethal dose"
> LC = "lethal concentration"
> 
> The 50 means 50% -- as in that particular dose caused 50% of the test 
> animals to die.
> 
> LC50 is usually expressed in parts per million (ppm), and oral LD50 is 
> expressed in milligrams of the substance per kilogram of the test animals 
> body weight.
> 
> Example - Oral LD50 = 3,000
> 
> 10 lab rats each weighing one pound.  On average, 3,000 mg of that 
> substance given to each rat would kill 5 of the rats.
> 
> Troy

Ooops!  That should have read "10 rats each weighing one KILOGRAM"

Sorry for the goof-up! 

I also should have pointed out that LC50 usually refers to inhalation 
hazard (concentration in the air), and oral LD50 refers to ingestion 
hazard.

Troy


