Environmental impacts on effectiveness of permethrin-treated clothing used by foresters to prevent mosquito bites

Principal Investigator: Stephanie L. Richards, MSEH, PhD; Environmental Health Sciences Program, Department of Health Education and Promotion, College of Health and Human Performance, East Carolina University. 3403 Carol Belk Building, Greenville, NC 27858. Email: richardss@ecu.edu. Office: 252-328-2526

Continuing a previously funded CARERC pilot study (04/13–09/30/13), this project has the following specific aims: (1) Evaluate the effects of environmental exposure on the ability of permethrin-treated fabrics to induce mosquito knockdown and/or mortality; (2) Assess the extent to which environmental conditions (e.g., light, temperature, humidity, number of washes) impact the concentration of permethrin in treated clothing. Such clothing is designed to protect foresters and other outdoor workers from mosquito and tick exposure and exposure to pathogens such as West Nile Virus, LaCrosse virus, and Eastern equine encephalitis, etc. A study by Vaughn & Meshnick(unpublished) has shown that effectiveness of permethrin treated clothing drops from 83% to 38% by its second year of wear. Other studies have explored the role of temperature, humidity, fabric content and weight, and repeated washings in reducing the effectiveness of permethrin-treated clothing. The authors anticipate that findings from this study will enhance understanding of the effectiveness of PPE available to foresters, and aid stakeholders in conducting cost-benefit analyses when selecting fabrics/uniforms.

Richards et al. will test the following fabrics:

Clothing will be hand washed in tap water with commercially available detergent and air dried in an incubator (at either 1 rc or 28°C) between daily successive washings. Washing treatments include

During drying periods, clothing in simulated sunlight treatment groups will be placed in an incubator (17"C or 28°C) and exposed to light from a xenon lamp for 40 hours a week (i.e. approximate weekly sunlight exposure of outdoor worker, assuming 8 hours of daily exposure for 5 days). Fabrics in the group experiencing no light will be kept in a separate incubator with no light. At weekly intervals for a total of 8 weeks, mosquito knockdown experiments will be conducted (see below) on these fabrics and samples of fabrics will be taken for permethrin testing (Aim 2).Study findings are expected to help provide a better understanding of the effectiveness of PPE available to foresters and environmental impacts upon treated clothing.

This project builds upon a prior project, “Effectiveness of insecticide-treated clothing to prevent tick and mosquito exposure in foresters,” funded through the Central Appalachian Regional ERC (CDC/NIOSH Cooperative Agreement1T42 OH010278-01, activity dates 09/30/12–09/29/13).

That study aimed to (1) Characterize the exposure risk of foresters/loggers to mosquito and tick bites, and (2) Assess the effectiveness of repellant/insecticide-treated clothing for the prevention of mosquito and tick bites. Nearly three dozen (34) foresters remained enrolled in that initial study (KY, N=2; NC, N=12; TN, N=3; VA, N=14; WV, N=3) as of October 2013

For a full report on the study as of 09/30/13, please click here (PDF file).