Alachlor and nitrofen – now ‘extremely hazardous’

The WHO updates its classification of pesticides by hazard every two years, and the 1996-97 version is now available. The classification gives an indication of toxicity, dividing active ingredients into five classes: Ia—extremely hazardous; Ib -highly hazardous; II—moderately hazardous; III—slightly hazardous; and Table 5—products unlikely to present acute hazard in normal use.
    While the classification deals only with acute risk to health, where studies of other effects, including cancer, have been completed this is noted, and in some classification is adjusted. This has effected two notable changes in this edition where the widely used herbicide alachlor has moved from III to Ia. And in a more dramatic move, nitrofen moved from Table 5 to Ia, having been found to be carcinogenic in rats and mice and teratogenic in several species.
    Other changes include moving both metaldehyde and quizalofop-p-terfuryl from III to II, while fenthion went from Ib to II. A number of new pesticides were noted: metconazole (III); and fluthiacet, metosulam, bispyribac (all Table 5). Several older pesticides were noted as obsolete.

The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 1996-97, International Programme on Chemical Safety, UNEP, ILO, WHO, WHO/PCS/96.3, IPCS/WHO, CH-1211 Geneva 27, Switzerland.