EpidemiologicalEvidence of Algal Toxins in Drinking Water and Recreational Waters
ReportNo WSAA 104
September 1996
SYNOPSIS
Objective:
Toinvestigate whether exposure to River Murray and allied water sources during aperiod of raised cyanobacterial cell counts was associated withgastrointestinal and dermatological symptoms.
Design:
Acase-control study selecting gastrointestinal and dermatological cases andcontrols from subjects attending 21 general practitioners in eight River Murraytowns in South Australia. The association between the proportion ofconsultations for such symptoms and mean log cyanobacterial count was alsoexamined.
Subjects:
102gastrointestinal cases, 86 dermatological cases and 132 controls.
Main Outcome Measure:
Therelative odds of gastrointestinal and dermatological symptoms, respectively, asopposed to no such symptoms, according to water contact history during the weekpreceding the medical consultation.
Results:
Afteradjusting for concurrent risk factors, subjects drinking chlorinated riverwater rather than rain water had a raised risk of gastrointestinal symptoms(P=0.008), and those using untreated river water for domestic purposes ratherthan rain water had a raised risk of gastrointestinal (P=0.034) and of dermatological(P=0.048) symptoms. The proportion of consultations for gastrointestinal anddermatological symptoms correlated on a weekly basis with the overall mean logcyanobacterial cell count. Statistical significance was, however, not achievedfor the correlation with dermatological consultations or for separate reachesof the river.
Conclusions:
Theraised risks of gastrointestinal and dermatological symptoms in those usingMurray River water for drinking and other domestic purposes are consistent withcausal relationships. However, the evidence for adverse health effects is atbest, only suggestive. This study has been the stimulus for a multistateinitiative under the National Health Consortium.
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