Birds diazinon toxicity

Bird kills with diazinon have been reported at all times of the year. Birds are markedly more susceptible to diazinon toxicity than other terrestrial vertebrates. LD50 values for birds range from 2.75 to 40.8 mg kg Diazinon is also very highly toxic to... 

The organophosphorons insecticides dimethoate and diazinon are mnch more toxic to insects (e.g., housefly) than they are to the rat or other mammals. A major factor responsible for this is rapid detoxication of the active oxon forms of these insecticides by A-esterases of mammals. Insects in general appear to have no A-esterase activity or, at best, low A-esterase activity (some earlier stndies confnsed A-esterase activity with B-esterase activity) (Walker 1994b). Diazinon also shows marked selectivity between birds and mammals, which has been explained on the gronnds of rapid detoxication by A-esterase in mammals, an activity that is absent from the blood of most species of birds (see Section 23.23). The related OP insecticides pirimiphos methyl and pirimiphos ethyl show similar selectivity between birds and mammals. Pyrethroid insecticides are highly selective between insects and mammals, and this has been attributed to faster metabolic detoxication by mammals and greater sensitivity of target (Na+ channel) in insects. 

Acute oral toxicity of diazinon to birds and mammals... 

Table 16.4 Acute Oral Toxicity of Diazinon to Birds and Mammals (All values shown are in milligrams of diazinon/kg body weight fatal to 50% after a single oral dose.)...

The toxicity of a chemical also varies from one animal to the next. The LD50 for the common insecticide Diazinon is 300 to 400 mg/kg in rats, while in birds it is 2.75 mg/kg. Theobromine, a chemical found in chocolate, is toxic to dogs but not to rodents. Although largely extrapolated from animal tests, a rating system for acute chemical toxicity for humans has been devised and is presented in Table 1. 

Diazinon, the active ingredient in products such as Diazinon, Basudin, and Knox Out. is a nonsystemic OP insecticide. Diazinon has a half-life in soil of 2-4 weeks (Pesticide Information Profiles, 1996). In water, diazinon s half-life is related to pH, with faster breakdown related to increasing pH, whereas in neutral conditions, half-life can be as long as 6 months (Pesticide Information Profiles, 1996). Although use of diazinon on golf courses and. sod farms in the United States was banned in 1988, primarily due to its high toxicity and lethality to birds (Pesticide Information Profiles, 1996), diazinon is still widely used in Canada, although several bird deaths have been reported (Frank et ui, 1991). 

---