HEALTH-EFFECTS OF EXPOSURE TO CYANOBACTERIA (BLUE-GREEN-ALGAE) DURINGRECREATIONAL WATER-RELATED ACTIVITIES

The aim of this study was to investigate effects on health of exposure to cyanobacteria as a result of recreational water activities. Partic ipants, who were aged six rears and over, were interviewed at water re creation sites in South Australia, New South Wales and Victoria on sel ected Sundays during January and February 1995. Telephone followup was conducted two and seven days later to record any subsequent diarrhoea , vomiting, nu-like symptoms, skin rashes, mouth ulcers, fevers and ev e or ear irritations. On the Sundays of interview, water samples from the-sites were collected for cyanobacterial cell counts and toxin anal ysis. There were 852 participants, of whom 75 did not have water conta ct on the day of interview and were considered unexposed. The 777 who had water contact were considered exposed. No significant differences in overall symptoms were found between the unexposed and exposed after two days. At seven days, there was a significant trend to increasing symptom occurrence with duration of exposure (P = 0.03). There was a s ignificant trend to increasing symptom occurrence with increase in cel l count (P = 0.04). Participants exposed to more than 5000 cells per m i, for more than one hour had a significantly higher symptom occurrenc e rate than the unexposed. Symptoms were not correlated with the prese nce of hepatotoxins. These results suggest symptom occurrence was asso ciated with duration of contact with water containing cyanobacteria, a nd with cyanobacterial cell density. The findings suggest that the cur rent safety threshold for exposure of 20 000 cells per mi, may be too high.