Report No DWI0094

Apr 1982

A number of epidemiological studies carried out in the United States have found statistical associations between cancer death-rates and the use of river or surface waters as the source of supply.

Epidemiological studies using British data have therefore been undertaken to investigate:

1. the possibility of an association between the long-term degree of contamination of water sources by sewage effluent and industrial effluent, and cancers of the digestive system and urinary tract,
2. whether any such associations with water sources exist with respect to more immediate adverse health indices such as stillbirths and infant mortality,
3. whether any adverse health effects are associated with organic chemicals in drinking water, as characterised by the type of water source; groundwater, river, or upland catchment.

The first two objectives, those concerned with the possible effects of re-use, were approached first in a study confined to the London area, where some of the water supplies have for many years contained the highest proportion of sewage effluent in the country. The study with respect to cancer mortality was then extended to all those towns in Great Britain receiving lowland river or underground water. The third objective was approached using data from around 250 urban areas in Britain. Multiple regression techniques were used, with refinements to overcome some of the limitations of aggregate population studies. Throughout the work attention has been paid to the influence of socioeconomic, geographical and other possible confounding factors.

The studies provided some evidence of small adverse health effects associated with (but not necessarily caused by) water supplies. In the case of reused water, the associated health effects were stomach cancer incidence in women, urinary tract cancer incidence in women, and stillbirth rates. Although the sizes of the effects of reuse were small, the evidence is consistent with the results of the epidemiological studies in the United States. In that part of the study in which different types of water source were contrasted, upland-derived supplies were associated with higher mortality from stomach cancer in women. This is a new finding, and the hypothesis would require further testing before a firm conclusion can be reached.

To investigate any of these matters further in this country it will probably be necessary to move on from studies of aggregated populations to studies of individuals. Possible designs for such studies are being investigated.

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