Pyrethrin and pyrethroid exposures in the United States: a longitudinal analysis of incidents reported to poison centers.

Introduction: Citing the Food Quality Protection Act, the US Environmental Protection Agency (EPA) decided to phase out and eliminate organophosphate insecticide use in residential environments. The phase out process spanned from 2000 to 2005, and it may have resulted in increased consumer use of insecticides containing other active ingredients. This study utilized data from the national Poison Control Center to assess possible changes in exposure incidents involving pyrethrin and pyrethroid insecticides during the phase out of organophosphates from residential uses.

Methods: We extracted pyrethrin and pyrethroid insecticide exposure data from the American Association of Poison Control Centers Toxic Exposure Surveillance System (TESS) annual reports from 2000 to 2005. We examined pyrethrin and pyrethroid incidents by total exposures for each year, and we stratified exposures by age range, reason, number of cases treated in a health care facility, and medical outcome. Cases were examined as a proportion of all insecticide exposures. We calculated the annual incidence rates for exposures involving pyrethrin and pyrethroid insecticides of the population served.

Results: Pyrethrin and pyrethroid exposures increased annually in number and as a percentage of all insecticide exposure incidents. The increase in cases was observed for all age categories and exposure reasons. A statistically significant correlation was observed between advancing years (2000-2005) and the number of pyrethrin and pyrethroid incidents (p<.01). While the number of incidents treated in a health care facility increased annually during the study period, the proportion was constant (0.185 +/- 0.012) over the six year period. During the study period, the incidence rate for pyrethrin and pyrethroid exposures increased each year. 44% of all medical outcomes data was recorded, and the majority of outcomes resulted in no symptoms (37%) or minor symptoms (53%).

Conclusion: TESS data showed a clear increase in cases involving pyrethrins and pyrethroids. The increase was temporally associated with the phase out of organophosphates from residential uses. In the future, medical toxicologists and poison control center personnel should be prepared to respond to an increasing number of pyrethrin and pyrethroid insecticide exposures.