Permethrin

From

Summary

TBD.

News Timeline

• Study claim. Common insecticide used in homes associated with delayed mental development of young children (Media release), Eurekalert.org, February 10, 2010.
  • Summary. "The study was conducted with a subset of 725 pregnant women participating in a prospective longitudinal study of black and Dominican women living in upper Manhattan and the South Bronx underway at the Columbia Center for Children's Environmental Health (CCCEH). The insecticide permethrin was selected for the evaluation because it is one of the most common pyrethroid insecticides used in U.S. homes, as well as the most commonly sold pesticide, according to a nationally representative sample. Piperonyl butoxide (PBO), a chemical that is added to insecticides to increase efficacy was also selected for evaluation. Any detection of PBO in air is a marker of a pyrethroid insecticide application. In all, 342 women were studied for permethrin exposure in personal air during pregnancy; 272 for permethrin in maternal and umbilical cord plasma; and 230 were evaluated for exposure to PBO. To collect the air samples, mothers from the CCCEH Mothers and Newborns cohort wore a small backpack holding a personal ambient air monitor for 48 hours during the third trimester of pregnancy. The children of these mothers were evaluated for cognitive and motor development at age three. CCCEH researchers used the Bayley Scales of Infant Development. In evaluating the results, researchers controlled for gender, gestational age, ethnicity, maternal education and intelligence, quality of the home environment, and prenatal exposure to environmental tobacco smoke and chlorpyrifos. PBO was detected in the majority of personal air samples (75%). While the results demonstrate that a significant prenatal exposure to permethrin in personal air and/or plasma was not associated with performance scores for the Bayley Mental Developmental Index or the Psychomotor Developmental Index at 36 months, children who were more highly exposed to PBO in personal air samples (≥4.34 ng/m3) scored 3.9 points lower on the Mental Developmental Index than those with lower exposures. "This drop in IQ points is similar to that observed in response to lead exposure," said Megan Horton of the Mailman School of Public Health and lead researcher. 'While perhaps not impacting an individual's overall function, it is educationally meaningful and could shift the distribution of children in the society who would be in need of early intervention services'."
  • Comment. This study could not possibly link pemethrin with lower IQ as childhood development is complex/multifactorial and not all developmental factors were considered by these researchers. Prenatal alcohol/drug consumption among the low-income women study subjects, for example, was not considered as a confounding factor. Other points:
    • Prenatal exposure to permethrin was not associated with lower IQ; only exposure to PBO, a chemical added to insecticides to increase efficacy.
    • Only the highest quartile of exposure to PBO was associated with lower IQ in one particular statistical model. In another model, the association was not statistically significant.
    • The highest quartile median exposures was much greater than one would expect (i.e., 0.27, 0.45, 0.87, 4.33 ng/m3). So there's something odd about that group of study subjects.
    • These researchers may be biased as they touted their earlier controversial findings that prenatal exposure to chlorpyrifos was associated with adverse neurodevelopment.

Studies and Reports

• Rusiecki J et al., Cancer incidence among pesticide applicators exposed to permethrin in the Agricultural Health Study, Environ Health Perspect. 2009 Apr;117(4):581-6. Epub 2008 Nov 10.
  • Conclusions. "This study found no association with most cancers analyzed. Although the suggested association with multiple myeloma was based on a small number of cases, it warrants further evaluation."
• Appel K et al., Risk assessment of Bundeswehr (German Federal Armed Forces) permethrin-impregnated battle dress uniforms (BDU), Int J Hyg Environ Health. 2008 Mar;211(1-2):88-104. Epub 2008 Jan 28.
  • Abstract. "In an age when vector-borne diseases are emerging worldwide, personal protective measures are essential for shielding soldiers and other exposed persons from arthropod attack. The development of permethrin-impregnated clothing has been one recent advance in protecting persons at-risk. However, to date risk assessment has not been performed related to wearing permethrin-impregnated clothing over longer time periods. Therefore, this paper describes relevant toxicological aspects of permethrin and estimates the extent of dermal permethrin uptake by soldiers wearing impregnated uniforms by determining urine metabolites of permethrin. The exposure monitoring conducted in wearers of untreated uniforms did not show any signs of increased permethrin uptake and was similar to that of the general population in Germany. By contrast, studies involving the soldiers wearing permethrin-impregnated uniforms identified far higher internal exposure, the amounts of urine metabolites clearly above the reference value for the background exposure of the German population at large. Comparing the median excretion values, an approximately 200 times higher exposure can be assumed. The excretion levels of the subject with the maximum amount of metabolites correspond to an internal exposure of around 5-6microg/kg body weight and day thereby considering that biomonitoring could not take all urine metabolites and other elimination routes into account. Based on an oral absorption rate of 50%, the internal dose of 5-6microg/kg body weight and day would correspond to an oral uptake of permethrin which is around 20% of the ADI value of 50microg/kg body weight and day. In addition, based on these data and using a dermal absorption rate of 2% the permethrin dose reaching the skin was estimated to be 250microg/kg body weight and day. Considering a standard body weight and the area covered by the uniform, an exposure level of about 1.25microg permethrin/cm(2) skin and day can be calculated. Clinical subjective symptoms were recorded by means of a self-reporting questionnaire which has been developed and used for this specific purpose in environmental outpatient departments in both groups (wearers of impregnated versus non-impregnated uniforms). Only minor sensory impairments were identified in one of the studies (Kabul/Afghanistan) which may represent skin paraesthesiae. Based on these results, it can be assumed that the normal use of permethrin-treated uniforms does not affect human health to a clinical relevant extent. We recommend that the release rate of permethrin from the textile material should be strictly monitored by means of a quality assurance method. It should comply with standards to which the results of this study may contribute."
• Macedo P et al., Risk assessments for exposure of deployed military personnel to insecticides and personal protective measures used for disease-vector management, J Toxicol Environ Health A. 2007 Oct;70(20):1758-71.
  • Abstract. "Infectious diseases are problematic for deployed military forces throughout the world, and, historically, more military service days have been lost to insect-vectored diseases than to combat. Because of the limitations in efficacy and availability of both vaccines and therapeutic drugs, vector management often is the best tool that military personnel have against most vector-borne pathogens. However, the use of insecticides may raise concerns about the safety of their effects on the health of the military personnel exposed to them. Therefore, our objective was to use risk assessment methodologies to evaluate health risks to deployed U.S. military personnel from vector management tactics. Our conservative tier-1, quantitative risk assessment focused on acute, subchronic, and chronic exposures and cancer risks to military personnel after insecticide application and use of personal protective measures in different scenarios. Exposures were estimated for every scenario, chemical, and pathway. Acute, subchronic, and chronic risks were assessed using a margin of exposure (MOE) approach. Our MOE was the ratio of a no-observed-adverse-effect level (NOAEL) to an estimated exposure. MOEs were greater than the levels of concern (LOCs) for all surface residual and indoor space spraying exposures, except acute dermal exposure to lambda-cyhalothrin. MOEs were greater than the LOCs for all chemicals in the truck-mounted ultra-low-volume (ULV) exposure scenario. The aggregate cancer risk for permethrin exceeded 1 x 10(-6), but more realistic exposure refinements would reduce the cancer risk below that value. Overall, results indicate that health risks from exposures to insecticides and personal protective measures used by military personnel are low."
• Mytton O et al., Safety of benzyl benzoate lotion and permethrin in pregnancy: a retrospective matched cohort study, BJOG. 2007 May;114(5):582-7.
  • Conclusion. "We found no evidence of adverse effects on pregnancy outcome due to topical 25% BBL or 4% permethrin."
• Meyer K et al., Agricultural pesticide use and hypospadias in eastern Arkansas, Environ Health Perspect. 2006 Oct;114(10):1589-95.
  • Conclusion. "... we did not find evidence that estimated exposure to (permethrin)... increases risk of hypospadias."
• Young G and Evans S., Safety and efficacy of DEET and permethrin in the prevention of arthropod attack, Mil Med. 1998 May;163(5):324-30.
  • Conclusion. "Many preventable diseases affecting troop strength are directly attributed to disease-carrying insects. The first line of defense against arthropod vectors is the use of personal protective measures. The concurrent application of DEET (N,N-diethyl-m-toluamide) repellent on the skin and permethrin [(3-phenoxy-phenyl)methyl(+/-)cis,trans-3-(2,2-dichloroethenyl)-2, 2- dimethylcyclopropane-carboxylate] insecticide on the battle dress uniform, while the uniform is worn properly, is a personal protective strategy officially known as the DOD Insect Repellent System. It is important for troop commanders and field leaders to enforce the use of personal protective measures to prevent insect-borne infectious diseases and to ensure troop and soldier readiness. DEET is a safe and effective repellent. Permethrin is a synthetic pyrethroid insecticide and repellent. Used in conjunction with proper clothing and other personal protective equipment, these repellents provide the best known protection available and are critical in minimizing the occupational health threat of arthropod-borne diseases to troops in the field."
• Llewellyn D et al., Occupational exposure to permethrin during its use as a public hygiene insecticide, Ann Occup Hyg. 1996 Oct;40(5):499-509.
  • Abstract. "Permethrin is an active ingredient found in many public hygiene insecticide products and exposure to it was assessed in a survey of 45 professional users. The exposures measured were over a wide range, with more than a 100-fold difference between average levels and the highest levels. Dermal contamination was evident on 93% of the operators, the highest contamination resulting from the use of leaking application equipment, demonstrating that proper maintenance of equipment is vital. Where the insecticide was applied at ground level most contamination was on the legs, indicating the importance of appropriate footwear. Contamination of the hands occurred despite the use of protective gloves, higher levels of contamination occurring when liquids were used. Dermal contamination was not always the principle route of exposure, and high airborne concentrations were linked with use in confined areas. Airborne concentrations were also associated with the physical form of the product used and the treatment method. To help in assessing the effectiveness of protective clothing and control measures, biological monitoring was carried out. Monitoring of metabolites in urine showed that systemic uptake occurred but evidence from toxicological studies indicates that the levels found were well below those considered to cause harm."