Waikato shallow lakes cyanobacterial update

Health warning in place only for Lake Waikare

The most recent cyanobacterial testing carried out on the six monitored lakes have shown generally low cell counts.

As at the end of August, the only lake, which still has a health warning, is Waikare, which has always had very high cell counts since monitoring began.

Warnings for Lakes Kainui, Waahi and Whangape do not currently have health warnings.

These low cell counts will probably rise in some or all of the lakes as Spring progresses and it is likely that some warnings will be reinstated when the next monitoring tests are taken in late October.

Monthly sampling will resume from November.

"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 Waikato District Health Board medical officer of health Dell Hood.

"In Kainui, it is quite possible that in some areas of the lake, the cell count is still above the warning level, and users are warned to be cautious in using this lake; particularly if children are likely to be in the water.

"Most lakes are not tested, and cell counts are typically lower during the cooler months, 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."

Swallowing water from lakes affected by blooms should also be avoided.

While not everyone will be affected, 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.

Waikato DHB's Population Health Service would like to be informed about health problems, which 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. Follow-up testing may be done, depending on the situation.

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

The Environment Waikato website has up-to-date results:

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.

Date: 3 September 2009

ENDS