Science Inventory

Risk Characterization and Cumulative Risk Assessment of Pyrethroids Based on Mode of Action.


Wolf, D. Risk Characterization and Cumulative Risk Assessment of Pyrethroids Based on Mode of Action. Presented at 1st INTERNATIONAL COURSE-SEMINAR OF ENVIRONMENTAL TOXICOLOGICAL PATHOLOGY, August 23 - 24, 2012.


The assessment showed that cumulative risks for both children and adults are sufficiently low so as not to be a concern for the currently registered uses of pyrethrins and pyrethroid pesticides.


Pyrethrins and pyrethroids are insecticides included in over 3,500 registered products in the U.S., many of which are used widely in and around households, including on pets, in mosquito control, and in agriculture. The use of pyrethrins and pyrethroids has increased during the past decade with the declining use of organophosphate pesticides, which are more acutely toxic to birds and mammals than the pyrethroids. This change to less acutely toxic pesticides, while generally beneficial, has introduced new issues. For example, residential uses of pyrethrins and pyrethroids may result in urban runoff, potentially exposing aquatic life to harmful levels in water and sediment. Pyrethrins are botanical insecticides derived from chrysanthemum flowers most commonly found in Australia and Africa. They work by altering nerve function, which causes paralysis in target insect pests, eventually resulting in death. Specifically, the pesticidal mode of action is disruption of ion channels which are critical for normal nervous system function. Pyrethroids are synthetic chemical insecticides whose chemical structures are adapted from the chemical structures of the pyrethrins and act in a similar manner to pyrethrins. Pyrethroids are modified to increase their stability in sunlight. Most formulations have chemicals added which enhance the pesticidal properties of the product without adding pesticidal effects of their own. The U. S. EPA based a risk assessment of pyrethroids as a common mechanism of toxicity. A common mechanism of toxicity group is two or more pesticide chemicals or other substances that cause a common toxic effect by the same, or essentially the same, sequence of major biochemical events or mode of action. A screening level cumulative risk assessment was conducted. These tend to be very conservative and are based on people being exposed to the highest levels of residues in food, water, and in their homes, all on the same day. The assessment showed that cumulative ris



Record Details:

Product Published Date: 08/24/2012
Record Last Revised: 09/05/2012
OMB Category: Other
Record ID: 246038