Media Release

Date: 9 July 2007

Waikato Shallow Lakes- Cyanobacterial warning update

Only three of the Waikato lakes where cyanobacterial monitoring is carried out remain above the health warning level. Monitoring done in late June shows that Lakes Kainui, Whangape and Waikare remain above the warning level of 15,000 cells per ml.

The warning has been lifted for Lake Waahi, where the cell count has fallen from around half a million to 7600.

Waikare's cell count remains very high at just over 1.5 million but Whangape, where the cell count peaked at around 11 million cells per ml in February, has fallen to 16,000 only just exceeding the warning level.

Lake Ngaroto's result is close to the warning level with a cell count of 14,758 and has shown a pattern of rising since autumn.

Lake Hakanoa's cell count has been well below the limit since April, most recently only 140 cells/ml.

In general cyanobacterial numbers are expected to fall as the weather gets cooler and there is less sunlight. However users of all shallow lakes in the region should continue to be cautious before taking part in any activity which involves direct contact with lake water. There are many lakes, and the cyanobacteria in them behave differently, even during winter's cooler shorter days.

Lake users are reminded 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. People should always avoid contact with water that looks cloudy green or brown, or has scum forming, even when there is no warning in place. Most lakes are not tested, and water users must consider the possibility of cyanobacterial blooms in any water body before they use it.

During blooms, lakes should not be used for any activity involving skin contact with the water. 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 not everyone will be affected, for some the risks are of rash and skin irritation, eye irritation, allergic 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 water.

Up to date information on cyanobacterial cell counts is available from local councils and Environment Waikato. (http://www.ew.govt.nz/enviroinfo/water/healthyrivers/waikato/algalbloom/).

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

ENDS