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TESTING OF PESTICIDE TOXICITY


All pesticides are tested to establish toxicity — a dose necessary to produce a measurable harmful effect, it is usually established through tests on mice, rats, rabbits and dogs.

Results are then extrapolated on humans, and safe exposure levels predicted.


The value commonly used to measure acute toxicity is LD 50 (a lethal dose in the short term; the subscript 50 indicates the dose is toxic enough to kill 50 per cent of lab animals exposed to the chemical). LD 50 values are measured zero onwards; the lower the LD 50 the more acutely toxic the pesticide.

To illustrate, comparison of DDT — most used in India up to the early 1990s — with monocrotophos, currently most used.

DDT’ S LD 50 is 113 mg/kg; monocrotophos, 14 mg/kg. But never forget that lower LD 50 means higher acute toxicity.

Pesticides once ingested, accumulate in the body fat or pass through. Organochlorine pesticides, for instance, accumulate in body fat and blood lipids. These fat-soluble chemicals persist in the body for many years.