Safety assessment of pyrethrins based on human experience

T.G. Osimitz, W. Droege, R. Kingston
Reports of dermatitis and respiratory reactions associated with use of pyrethrin-containing products have been described in the medical literature over the last century. The Pyrethrins Joint Venture has responded in several ways. Using knowledge of pyrethrum chemistry and an evidence-based analysis of literature, we assessed whether pyrethrins induce immunologic contact urticaria (ICU) or allergic contact dermatitis (ACD). Our interpretation suggests that no reports presented in the literature fulfill the criteria for either ICU or ACD. Similarly, our assessment of the published data does not indicate that people with asthma or other evidence of airway hypereactivity are unusually sensitive to pyrethrins. Following a review of reports to North American Poison Control Centers (2001-2003), despite extensive use, incidents with reports of moderate or major adverse effects were rare. The data suggest that asthmatics and people sensitive to ragweed (Ambrosia artemisiifolia) are not unusually sensitive to pyrethrins/piperonyl butoxide (PY/PBO). In view of their widespread use, the data indicate that PY/PBO products can be used with a relatively low risk of adverse effects. The objectives of the Pyrethrums Stewardship Program (PSP) were to investigate consumer exposures to pyrethrin-containing products and evaluate the possible association between use and adverse events. Incidents in which the subject reported at least one dermal or respiratory symptom of minor or greater outcome severity were included in the PSP. Of 531 cases (reports of human exposure to a pyrethrins-containing insecticide) received during 2014, 221 cases involving 177 exposed symptomatic individuals qualified for inclusion in the PSP. Total release foggers were the predominant product type. The majority of the products contained pyrethroids in addition to pyrethrins. Non-specific irritation to the respiratory tract (i.e., cough/choke) was the most commonly reported symptom. Almost 88% of exposed individuals claimed outcomes of minor severity; the remainder claimed moderate effects. Ninety percent of all completers were managed outside of a health care facility (generally at home), further underscoring the minor severity of effects associated with the exposures. No cases of major severity or deaths were reported. Of 177 eligible exposed individuals who were contacted by phone, 50 individuals (with 46% reporting a positive allergy status and 14% a positive asthma status), upon their consent, completed an enhanced questionnaire that probed circumstances of and results from exposure. Assistance with diagnostic patch and prick testing under physician oversight was offered, but no individual chose to participate. None of the data collected to date suggest that pyrethrin-containing products pose a significant risk of serious dermal and/or respiratory reactions to individuals with or without asthma and allergies.
Osimitz, T.G., Droege, W. and Kingston, R. 2017. Safety assessment of pyrethrins based on human experience. Acta Hort. (ISHS) 1169:33-40
consumer products, pyrethrum, exposure, dermal, respiratory, outcome asthma, allergy

Acta Horticulturae