Media information For immediate release

Date: 20 May 2009

Waikato Shallow Lakes Cyanobacterial Warning Update

The cyanobacterial health warning has been reinstated for Lake Kainui, but lifted on Lake Ngaroto following the latest monitoring results from the six tested Waikato shallow lakes.

Warnings remain in place for Waahi, Waikare and Whangape; cell counts at Hakanoa remain low.

"Kainui's cell count has risen again to just above the current warning level of 15,000 cells/ml and the cells present are almost entirely those of a single species, rather than a mixture of species," said Waikato District Health Board's Population Health medical officer of health Dell Hood.

"This coincides with increased chance of water contact activities during the duck shooting season.

"It is likely that the cell count is in fact fairly steady at the moment, and the changes seen over the last three tests are random variations between samples."

She said Lake Waahi's cell count by contrast has been falling steadily since its highest numbers in the summer but it remains above the warning level.

"Waikato shallow lake users should always avoid contact with water which looks cloudy green or brown, or has scum forming even when there is no warning in place," said Dr Hood.

"Most lakes are not tested, and although cooler weather and shorter daylight hours generally see a decrease in the growth of algae, the results of the testing over the last two-and-a-half years have been quite unpredictable. "Users must consider the possibility of cyanobacterial blooms in any water body before they use it - at any time of year."

Dr Hood reminds the public that test results should be used for general guidance only, as cyanobacteria and their toxins will not be evenly spread through any lake and may be concentrated in some areas by wind and water movements.

"During blooms, lakes should not be used for any activity which involves skin contact with the water," she said.

"If people choose to do this, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable."

People should also avoid swallowing water from lakes affected by blooms.

While it will not affect everyone; for some the risks include rash, skin and eye irritation, allergy symptoms such as hayfever and asthma and possibly stomach upsets such as diarrhoea and vomiting.

These effects may not appear until some time after contact with the affected water.

Population Health would like to be informed about health problems that develop after exposure to any of the Waikato lakes. This allows recording of location, time, the activity taking place and length of time the problem lasted.

Depending on the situation, follow-up water testing may be done.

"Up-to-date information on cyanobacterial cell counts is available from local councils and Environment Waikato.

For up-to-date information, please visit http://www.ew.govt.nz/Environmental-information/Rivers-lakes-and-wetlands/healthyrivers/Waikato-River/Algal-Blooms-in-the-Waikato-region/#Heading4

Health advice is available from the Population Health (07) 839 8899 in and out of hours.

ENDS

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