Peter L. Borst wrote:

> The health effects of organophosphates, carbamates, and other 
> cholinesterase inhibitors are dose respondent: the amount of the 
> chemical and the duration of exposure are directly proportional 
> to the severity of the symptoms.

Yes, dose (concentration & time) dependent.  And some 
organophosphates are not seriously toxic to people at the
actual use dilutions used.  Examples:

A 0.5% strength Malathion formulation is EPA approved for use on 
childrens heads (with a doctor's prescription) to control head lice: 
http://www.michigan.gov/documents/Final_Michigan_Head_Lice_Manual_103750_7.pdf 
"The lotion is applied to the hair, left to air dry, then washed off after 
8 to 12 hours."  This 0.5% strength that is approved for use on children's 
heads is 5 times stronger than the 0.1% strength typically used to 
spray crops and home gardens.

Dichlorvos, another organophosphate, is EPA approved for fogging
food processing plants and food storage warehouses.  I've sold tens of
thousands of gallons of it over the past 24 years to California's almond, 
walnut and pistachio processing and packing plants.

Chlorpyrifos-methyl, another organophosphate, is EPA approved for 
post harvest use directly on barley, oats, rice, grain sorghum and wheat
being conveyed into grain bins.  Ditto for pirimiphos-methyl on corn.
http://www.ext.vt.edu/news/periodicals/cses/2005-10/grain.html

At least one organophosphate, Acephate, is a systemic as well
as a contact insecticide.  This evening I was at a Hope Depot that
sold Ortho Orthene Systemic garden spray (contains acephate).

Paul Cherubini
El Dorado, Calif.

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