Isofenphos toxicity

Toxicity The acute oral LD50 of isofenphos for rats ranges from 20 to 125 mg/kg, and the acute dermal LD50 for rats is 70 mg/kg. The acute LC50 for rats is 0.144 mg/L and 1.3 mg/L. The acute inhalation LC50 (4 hours) for hamsters is 0.23 mg/L. These values indicate that the compound is highly toxic to organisms and humans who inhale even small amounts of isofenphos. In combination with malathion, isofenphos becomes extremely toxic.65,67... 

Isofennhos. Exposure of soils to salicylic acid, the secondary hydrolysis product of isofenphos, resulted in enhanced degradation of isofenphos (Table IV). Nearly two-thirds of the applied isofenphos was converted to soil-bound residues in soil pretreated 3 and 4 times with salicylic acid. Seventy-eight percent of the applied isofenphos was recovered at the end of the 3-week incubation in the control treatment as compared with 34 to 65% in soils pretreated with salicylic acid. The ability of microbes to metabolize structurally similar compounds such as 3,5-dichlorosalicylate, 3,6-dichlorosalicylic acid (24), and 5-chlorosalicylate (25) to their benefit has been reported. The low microbial toxicity, relative availability (as discussed later in this chapter), and nutritive value of salicylic acid may contribute to its potential to condition soils for enhanced degradation of isofenphos. 

The hydrolysis products of some pesticides susceptible to enhanced degradation (isofenphos, diazinon, carbofuran) yielded higher EC50 values, reflecting their low toxicity to bacteria (Table V). Conversely, some pesticides with little or no propensity for enhanced biodegradation yield hydrolysis products that show considerable antibacterial activity (chlorpyrifos, 2,4,5-T). 

---