Report No DWI0112

Mar 1990

SUMMARY

I OBJECTIVES

1. To investigate the ability of concentrated drinking water extracts to induce genotoxic effects in cells of the gastro-intestinal tract.
2. To investigate the binding of mutagens in drinking water to exogenous proteins and body fluids in vitro.
3. To evaluate the mutagenic activity of polar compounds in drinking water (those recovered by XAD resin at low pH) using mammalian cell systems.

Chlorine used for disinfection of drinking water reacts with naturally occurring organic molecules to produce by-products that are mutagenic. The significance of these mutagens to the health of consumers is not clear.

III CONCLUSIONS

1. High doses of chlorinated drinking water extracts at pH 7.0 and pH 2.0 did not induce nuclear anomalies in bone marrow, gastro-intestinal tract or bladder. A very slight increase of nuclear anomalies was seen in the non-glandular stomach of some anim als treated with pH 7.0 extract.
2. Maximum tolerated doses of the potent bacterial mutagen MX induced only marginal increases in nuclear anomalies in the jejunum/ileum. A small increase in nuclear anomalies was seen in theglandular stomach but were not observed at lower than the maximum tolerated dose. No increase in nuclear anomalies was seen in bone marrow or transitional epithelium of bladder. A possible marginal increase in nuclear anomalies was observed in the lamina propria of bladder.
3. Mutagenicity to mammalian cells in tissue culture was greatly reduced in the presence of serum, albumin and glutathione suggesting that the activity of these mutagens will be substantially ameliorated or abolished in higher organisms.
4. A clear and consistent increase in mitotic figures was seen in the liver of animals given extracts of chlorinated drinking water concentrated at pH 7.0. This was less marked with pH 2.0 extracts.
5. Substantial reassurance that mutagens from chlorinated drinking water do not pose a significant hazard to consumers can be gained from these findings. However the limitations of the techniques available preclude absolute statements regarding hazard.

IV RECOMMENDATIONS

1. Consideration should be given to further studies on the activity of chlorination derived mutagens in bladder.
2. Further attempts to characterise the mutagens present in pH 7.0 extracts should be made since little is known about the compounds contributing to this mutagenicity.
3. In the event of brominated derivatives of MX being detected in drinking water extracts these should be tested in higher test systems for genotoxicity and if appropriate in in vivo systems.
4. MX should be tested in a second in vivo test system when a suitable test system is adequately established.
5. The absorption, metabolism and excretion of MX and similar compounds should be further studied in vivo using radiolabelled material.
6. Consideration should be given to the investigation of the mitogenic activity of extracts in liver although this must be considered of lower priority than other studies.

The work covered in this report concerns the evaluation of the potential risk to consumers health of chlorination derived mutagens in drinking waters.

Extracts of chlorinated drinking water concentrated at pH 2.0 have been shown to produce chromosome aberrations in cells in tissue culture although the toxicity of these extracts to the cells is greater than pH 7.0 extracts. In vitro studies have shown that the mutagens bind to serum proteins and albumin and are inactivated by glutathione.

In vivo studies with extracts at the maximum tolerated dose indicate that these are not genotoxic in bone marrow, gastro-intestinal tract, liver or bladder. MX only produced marginal changes in jejunum/ileum, glandular stomach and possibly lamina propria of bladder at doses approaching the LD50.

The implications of these findings are discussed and recommendations for further work presented.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.