Media release from Waikato DHB
 
The health warnings have now been lifted for two more Waikato lakes, leaving Waikare the only regularly tested lake which still has a warning in place.  Ngaroto and Whangape have their warnings lifted; Hakanoa and Waahi have not had health warnings for some months. 

Lake Rotoroa in Hamilton also has no health warning as cell counts continue to be low.

Waikato Regional Council is no longer routinely testing Lake Kainui but caution is always advised for users of this lake, because of its history of cyanobacterial blooms.

As always, these 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, said medical officer of health Dr Dell Hood.  

Cyanobacterial blooms can happen very quickly when conditions for growth are favourable.  While this is more common in summer, blooms established during summer and autumn can persist into the winter months..

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

Scums are a particular risk and contact with scums should be avoided.  If contact does occur, skin should be rinsed clean and clothing changed as soon as possible.  Because of their small size, this warning is particularly important for children.

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

"If people still choose to use the lakes when warnings are in place, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable."

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.  Long term exposure to cyanobacterial toxins may bring additional health risks.  Scums on any lake are likely to contain high levels of toxin.

The Waikato DHB Population Health Service would like to be informed about health problems which develop after exposure to any of the Waikato lakes.  

Up-to-date information on cyanobacterial cell counts is available from local councils and Waikato Regional Council.  The Waikato Regional Council website: http://www.waikatoregion.govt.nz/Environment/Natural-resources/Water/Rivers/Waikato-River/Algal-Blooms-in-the-Waikato-region/

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