High levels of mutagenic activity in chlorinated drinking water in Finland.

The organic extract from the drinking water of Kuopio, Eastern Finland, turned out to be highly mutagenic in the Ames test. The direct mutagenic activities of the acid/neutral fractions of 48 drinking water samples were on an average 1700 net revertants/l in strain TA100. The highest activities were more than 6000 net revertants/l, and one drinking water sample exceeded 10 000 net revertants/l. The drinking water of Kuopio is produced from lake water which has a relatively high content of humic substances. Water processing involved two chlorination phases. The organic constituents of the water samples were isolated either by continuous liquid-liquid extraction or by absorption on XAD 8 resin.