“…Direct-acting mutagenic activity of trihalomethanes and other chlorinated and nonchlorinated organic products, formed as a result of aqueous chlorination of humic materials, has been reported by some authors (Bull, 1981;Meier et al, 1983;Meier, 1988). Furthermore, studies performed in United States, Canada, Europe, and South Africa have documented that the organic fraction of chlorinated drinking water derived from surface water has shown mutagenic activity in Ames SalrnonelZalmammalian-microsome test and in mammalian culture cells (Athanasiou and Kyrtopoulos, 1983;Cheh et al, 1980;De Marini et al, 1982;Douglas et al, 1986;Grabow et al, 1981;Kool and Kreijl, 1984;Maruoka and Yamanaka, 1980;Meier et al, 1983;Meier, 1988;Nestmann et al, 1979;Schwartz et al, 1979;Williams et al, 1982;Vartiainen and Liimatainen, 1986).…”