Identiteit, voorkomen en betekenis van de chloreringsprodukten van humuszuur in waterig milieu

Abstract

During chlorination of cyanoethanoic acid at pH=10 a number of compounds is formed. The compounds were confirmed with synthetic standards with GC and mass-spectrometry (MSD). The endproducts of the reaction at pH=10 were dichloroacetic acid, dichloromalonic acid and a small amount of trichloroacetic acid. Intermediates were dichloroacetonitrile (DCAN) and N-chloroacetamides. These N-chloroacetamides were previously errorneously identified as hydroxamoyl chlorides. Mutagenicity tests showed that only DCAN is mutagenic. The total of the mutagenicity of the chlorination mixture can be declared by this compound. In samples drinking water derived from plants where chlorine is used DCAN is detected (0.04-1.05 mug/L). At this concentration level the health risks are very small. The strong bacterial mutagen 'MX' is detected in chlorinated river water (Rhine and Meuse). In these samples the accounted contribution of MX on the measured mutagenic activity (Salmonella typhimurium TA 100) is appr. 20%. In samples drinking water no MX is detected. By chlorination with a higher dose than used for postdesinfection the compound can be formed. It seems to be that the most important mutagens will be organic acids isolated at low pH. The application of chlorine during the production of drinking water has to be limited for emergencies to maintain the bacteriologic quality.<br>