Eect of selected pesticides and their ozonation by-products on gap junctional intercellular communication using rat liver epithelial cell lines Susan J. Masten a, * , Ming Tian a , Brad L. Upham b , James E. Trosko b a Department of Civil and Environmental Engineering, Michigan State University, Research Complex ± Engineering A 130, East Lansing, MI 48824, USA b Department of Pediatrics/Human Development, Institute of Environmental Toxicology and the Cancer Center of MSU, East Lansing, MI 48824, USA Received 15 November 1999; accepted 9 May 2000 Abstract The non-genotoxic eects of two commonly used pesticides, 1,1-bis p-chlorophenyl)-2,2,2-trichloroethane DDT) and malathion, and one widely used commercial insect repellent N,N-diethy-m-toluamide DEET) on gap junction intercellularcommunicationGJIC)weredeterminedusingaratliverepithelialcellline.MalathionandDDTreversibly inhibitedGJICinatreatmenttime-anddose-dependentmanneratnon-cytotoxicdoses,whereas,DEETdidnotinhibit GJIC. Malathion was very reactive with ozone, while DEET and DDT did not react to any appreciable extent with ozone. The mixtures of ozonation products from malathion and DEET did not inhibit GJIC. The mixtures of ozo- nation by-products formed from DDT inhibited GJIC, but to a lesser extent than did DDT, itself. These results suggest that ozone can eectively remove malathion from solution without forming GJIC-toxic products, but is less eective in eliminating DEET and DDT from solution. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Malathion; DDT; DEET; Ozone; Gap junction intercellular communication 1. Introduction The presence of pesticides in the surface and groundwaters throughout the United States is ubiqui- tous Gilliom et al., 1999). This has resulted in much public concern, as many of these waters are used for drinking purposes Funari-Enzo, 1995). Since prior to distribution, water is treated with various reactive chemicals, including chlorine and ozone, an additional concern and one rarely investigated is whether the products formed during this treatment render the pol- lutants more or less toxic. With this in mind, we have focused our eorts on investigating the epigenetic tox- icity of three commonly used pesticides, 1,1-bis p- chlorophenyl)-2,2,2-trichloroethane DDT), malathion and N,N-diethy-m-toluamide DEET) and their ozona- tionby-products.Themolecularstructuresofthesethree pesticides are shown in Fig. 1. DDT, an organochlorine pesticide, that has been used for pest control is both bio-accumulated and per- sistent in the soil environment Ney, 1995). DDT or its metabolites have been found in surface waters e.g., Heinisch and Klein, 1991; Pereira et al., 1996), groundwaters e.g., Loch, 1991; Adamski and Pugh, 1996), soils e.g., Dogheim et al., 1996; Spencer et al., 1996), and dairy products e.g., Peyraud, 1971; Von D uszeln, 1991). Chemosphere 44 2001) 457±465 www.elsevier.com/locate/chemosphere * Correspondingauthor.Tel.:+1-517-353-8539;fax:+1-517- 353-8464. E-mail address: masten@egr.msu.edu S.J. Masten). 0045-6535/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0045-653500)00296-4