MEDIA INFORMATION FOR IMMEDIATE RELEASE
Date: 5 December, 2008
Further Waikato Shallow Lakes Cyanobacterial Warning
Six monitored lakes now have health warnings
As expected, the recent summer weather has resulted in massive growth of cyanobacteria in the routinely monitored
Warnings were already in place for Lakes Whangape, Waikare and Kainui, but over the winter cell counts were low in the
other monitored lakes - Hakanoa, Waahi and Ngaroto.
During the month of November, cell counts rose dramatically, rising 350 fold in Hakanoa, and two thousand fold in Waahi.
The most recent cyanobacterial results for Lake Rotoroa (Hamilton Lake) continue at low cell counts. This lake has no
history of algal blooms but is also monitored regularly over the summer months.
"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.
"Most lakes are not tested, and summertime conditions generally increase the growth of algae. Users must consider the
possibility of cyanobacterial blooms in any water body before they use it - at any time of year."
Algae may bloom to potentially harmful numbers within a matter of days if conditions for growth are ideal, as current
results suggest they are.
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.
The Waikato DHB Population Health Service would like to be informed about health problems which develop after exposure
to any of the Waikato lakes.
Informal feedback suggests that water users may at times experience transient rashes and stomach upsets.
These incidents, while not serious for the individual could be early warnings of more significant problems. There could
also be irritants other than cyanobacteria present in the water.
Population Health Service wishes to hear from anyone who has experienced this sort of problem after contact with any of
our lakes or rivers, to allow recording of location, time, the activity taking place and length of time the problem
"Minor health problems such as these do not require medical care, so we rely on the public to keep us up-to-date with
this information," said Dr Hood.
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.
Health advice is available from the Population Health Service (07) 839 8899 in and out of hours.