Triennial review 2010 • During this review, it was pointed out that several pesticides had the concept of additivity misapplied • Additivity is a concept in which the concentration of the degradates is added to that of the parent compound to determine the total toxicity of the individual pesticides detected.
Hazard Index Rule • In 2000, the EPA created the Hazard Index Rule which specifies that the total toxicity of a pesticide includes the toxicity of its degradates and that each degradate is assumed to be as toxic as the parent compound , unless proven otherwise. • We have 100+ pesticides listed in DEQ-7, about 15% of which have known degradates with toxicity or carcinogenicity • Seven pesticides have been found to be improperly listed as additive with the parent pesticide when individual toxicology information is available through IRIS or development of a Human Health Advisory
Based on the Hazard Index Rule, the following seven pesticides should be quantified independently of their degradates: • Alachlor, • Atrazine • Azinphos methyl • Imazamethabene • Metolachlor • Pinoxiden • Acetochlor
DEQ-7 Pesticide Review • All of the pesticides listed in DEQ-7 will be reviewed and the Hazard Index Rule and the concept of additivity will be uniformly applied to all compounds. • The current review shows that less than 5% of the listings have had these EPA rules mis-applied.
Examples Pesticide A has two degradates, B and C, with no toxicology data Pesticide B has two degradates F and G, and F has a known toxicology • Pesticide A would be listed , both compounds B and C would be assumed to have the same toxicity as the parent pesticide and would be added to the parent compounds for net toxicity measurement • Application of the additivity principle • Pesticide B and F would be listed independently, compound G would be assumed to have the same toxicity as compound B and would be added to B in determining the total toxicity for the pesticide • Simultaneous application of the additivity principle and the Hazard Index Rule