Report No DWI0759

ASSESS1NG THE VALUE OF EPIDEMIOLOGICAL STUDIES OF ACUTE CHEMICAL CONTAMINATION INCIDENTS AFFECTING DRINKING WATER

Final Report to the Department of Environment

DWI0759

Feb 1996

EXECUTIVE SUMMARY

Chemical incidents that result in the acute (i.e. short-term) chemical contamination of drinking water supplied to a substantial population of consumers are reassuringly rare. Such incidents provide the opportunity for epidemiological investigation to establish whether the contamination affected the health of the exposed population and, if possible, to quantify the effect, although there may be a number of other reasons for carrying out such studies. Before trying to decide whether epidemiological studies of acute chemical incidents should be encouraged, a view is needed on whether such studies are a) technically feasible and b) of value. With these questions in mind, the objective of this programme of research was to assess relevant published studies and establish the extent to which epidemiological investigations of acute incidents of chemical contamination have been or could be worthwhile. This included identifying requirements that future studies would need to meet to be regarded as useful.

In practice, there have been few epidemiological studies of the impact of contaminants on consumers who receive the water. Eleven studies were chosen for review and were assessed not only in terms of their technical quality but also whether they met their own declared aims and other specified objectives of particular interest to DOE.

The review demonstrated that epidemiological studies of acute chemical contamination of drinking water are technically feasible. Nine of these eleven studies were successful in investigating and quantifying the effects of the contamination on the exposed population. Only three of the studies, however, could be said to add to basic scientific knowledge on the toxicology of the contaminant involved. These three studies involved small populations and symptoms of illness that were susceptible to clinical confirmation. Eight of the studies were considered to have helped in the planning of the health care of the exposed population. All of the studies were considered capable of contributing to the management of any future incident involving the same or similar contaminants.

A number of weaknesses of varying importance were identified in the studies, although the review revealed two aspects that were critical for the quality of information that the studies were able to provide. These were a) the time interval between the onset of the incident and the start of the research; b) the provision of adequate information on the concentrations of the contaminant(s) in the drinking water to which members of the study population were exposed.

The report gives technical guidelines for future studies and makes recommendations of an operational nature. The two most important recommendations are, first, that contingency planning should be in place to establish a routine of good communication between all of the experts and organisations that need to be involved. Second, in order to ensure that adequate water sampling takes place to support an epidemiological study, resources must be available in addition to those already committed to the investigation and management of the cause of the incident. As one aspect of this, further consideration needs to be given to the storage of perpetual rolling samples at water treatment works.

Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.