ORIGINAL ARTICLE Exposure and health risk assessment of applicators to DDT during indoor residual spraying in malaria vector control program Fantahun Wassie 1 , Pieter Spanoghe 2 , Dejene A. Tessema 3 and Walter Steurbaut 2 We assessed exposure of applicators, health risk of DDT to the applicators and evaluated the applicability of existing pesticide exposure models for indoor residual spraying (IRS). Patch sampling for dermal and personal air sampler for inhalation exposure were used in monitoring 57 applicators on the exposure assessment to DDT. The exposure of the applicators was also estimated using three exposure models. The mean actual dermal exposure was 449 mg total DDT per applicator per one house treatment. The applicators were exposed to DDT much beyond the estimated AOEL (acceptable operator exposure level) of DDT. The exposure estimated with ConsExpo 5.0 b01 model is situated between the median and the 75th percentile of the experimental data. On the other hand, spraying model 1 and spraying model 10 overestimate the exposure. Thus, these three models cannot be directly used for the particular circumstances of IRS as a tool for risk assessment. In general, use of DDT in IRS as a control method for malaria mosquitoes holds a high health risk for the applicators. Strict implementation of spraying procedures stated in the IRS manual of World Health Organization (WHO) is necessary to reduce the exposure level and health risk of applicators to DDT. Journal of Exposure Science and Environmental Epidemiology (2012) 22, 549--558; doi:10.1038/jes.2012.45; published online 16 May 2012 Keywords: applicators; DDT; exposure assessment; health risk assessment; indoor residual spraying INTRODUCTION Malaria is a very important disease in tropical regions such as Africa. Ethiopia is one of the African countries in which malaria is a leading public health problem. The number of people estimated to be residing in malarious areas of Ethiopia has shown a dramatic increase from 17.7 million in 1965 to more than 52.6 million in 2005. 1 In the country, B70,000 people are dying of malaria each year. 2 Indoor residual spraying (IRS) of pesticides is one of the malaria vector control methods that are being used in Ethiopia. 3 In the country, DDT has been on use for IRS since the 1950s. 4 The coverage of DDT-sprayed households was increased from 20% in 2006 to 65% in 2009 (Dereje Mamo, Ministry of Health, Ethiopia; unpublished data). However, IRS of DDT does not fulfill its intended use as malaria mosquitoes are becoming resistant. 3,5,6 Instead, the possible human health risk of DDT, especially to the applicators, could outweigh its use. Applicators/operators (people who mix, load and apply pesticides) have the greatest exposure because of the very nature of the work. Exposure databases have been developed both in North America and Europe to better understand the extent and variability of exposure of applicators. 7 These research databases have helped to evaluate the human health risk of pesticide uses. In Ethiopia, there are no exposure data available. This resulted in lack of knowledge about human exposure and health risks of DDT similar to other countries where DDT is still being used in malaria control. 8 Similarly, the need for additional work, particularly to better characterize and understand the extent of exposure of people to DDT during IRS, was also highlighted. 9 Currently, pesticide exposure predictive models are being used in developed nations for estimating the risk of pesticide spraying as a first-tier ‘‘worst-case’’ approach. However, these models are simulating treatment conditions for agricultural use or for treatments with biocides in conditions that are not similar to the situations of IRS in malaria control. May be, it is for this reason that World Health Organization (WHO) pesticide evaluation scheme has indicated the need to develop a generic model for risk assessment of chemicals/pesticides used in IRS. 9 Exposure of applicators to DDT during IRS was noted in the 1950s and 1960s. 10,11 On the other hand, in Ethiopia, exposure of applicators to DDT has never been done since the introduction of its use in agriculture and public health sectors, although the applicators are inevitably exposed. Therefore, it is the intention of this study to monitor the real exposure of applicators to DDT during IRS under the local working conditions, to assess the health risk of DDT to the applicators, and to evaluate the applicability of existing pesticide exposure models for IRS. For this purpose, we monitored 57 applicators using a patch sampling method for dermal and a personal air sampler for inhalation exposures. The acute exposure of the applicators was estimated and the health risk of DDT to the applicators was assessed in relation to the derived acceptable operator exposure level (AOEL) of DDT and Received 1 July 2011; accepted 16 November 2011; published online 16 May 2012 1 Department of Environmental Health Sciences and Technology, College of Public Health and Medical Sciences, Jimma University, Jimma, Ethiopia; 2 Department of Crop Protection Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure, Gent, Belgium; 3 Department of Chemistry, College of Natural Sciences, Jimma University, Jimma, Ethiopia. Correspondence to: Fantahun Wassie, Department of Environmental Health Sciences and Technology, Jimma University, College of Public Health and Medical Sciences, P.O. Box: 378 or 1284, Jimma, Ethiopia. Tel.: þ 251 917 804285. Fax: þ 251 471 114484. E-mail: Fantahun.wassie@ju.edu.et or Fantahun.fantahunwassiebizuneh@ugent.be Journal of Exposure Science and Environmental Epidemiology (2012) 22, 549 -- 558 & 2012 Nature America, Inc. All rights reserved 1559-0631/12 www.nature.com/jes