Epidemiological Evidence of Algal Toxins in Drinking Water and Recreational Waters
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report No UWRAA 104
To investigate whether exposure to River Murray and allied water sources during a period of raised cyanobacterial cell counts was associated with gastrointestinal and dermatological symptoms.
A case-control study selecting gastrointestinal and dermatological cases and controls from subjects attending 21 general practitioners in eight River Murray towns in South Australia. The association between the proportion of consultations for such symptoms and mean log cyanobacterial count was also examined.
102 gastrointestinal cases, 86 dermatological cases and 132 controls.
Main Outcome Measure:
The relative odds of gastrointestinal and dermatological symptoms, respectively, as opposed to no such symptoms, according to water contact history during the week preceding the medical consultation.
After adjusting for concurrent risk factors, subjects drinking chlorinated river water rather than rain water had a raised risk of gastrointestinal symptoms(P=0.008), and those using untreated river water for domestic purposes rather than rain water had a raised risk of gastrointestinal (P=0.034) and of dermatological(P=0.048) symptoms. The proportion of consultations for gastrointestinal and dermatological symptoms correlated on a weekly basis with the overall mean log cyanobacterial cell count. Statistical significance was, however, not achieved for the correlation with dermatological consultations or for separate reaches of the river.
The raised risks of gastrointestinal and dermatological symptoms in those using Murray River water for drinking and other domestic purposes are consistent with causal relationships. However, the evidence for adverse health effects is at best, only suggestive. This study has been the stimulus for a multistate initiative under the National Health Consortium.