Just how dangerous are pesticides?
• Pesticides vary in how they affect organisms, including people, and in how long they persist in the environment. The World Health Organization (WHO) ranks pesticide from ‘Extremely hazardous’ (Class 1-A) to `Slightly hazardous’ (Class 3). But this system is based on an acute toxicity measure (LD50 ? lethal dose for 50 percent of laboratory test animals) and does not consider the risk of cancer, birth defects or other chronic health effects. • Pesticides can harm in ways we may not expect. For example, phenoxy herbicides like 2,4,5?T are designed to kill plants by causing them to grow too quickly, but they can also poison animals by damaging their livers. • Two or more pesticides in combination can be much more toxic than one could predict on the basis of their individual toxicities – an effect called synergism. The common practice among peasant farmers of mixing several chemicals into a pesticide ‘cocktail’ is particularly dangerous, given that few combinations have ever been studied
