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Appendix 9: Health warning sign for benthic cyanobacteria

Below is an example of the text for a health warning sign for benthic cyanobacteria. A health warning sign should provide enough information to inform the public of the potential health risks and enable them to make an informed decision. It should be clearly dated to inform the public when the warning was issued. Photographs on signs should show the public what to look for. For benthic cyanobacteria it may be useful to have a ‘medium risk’ sign which advises the public on what to look for at sites with known problems. ‘High risk’ signs can then be put in place when the action level (red mode) threshold is exceeded. Examples of medium risk and high risk signs used by the Greater Wellington Regional Council are given below:

Toxic cyanobacteria (blue-green algae) health hazard sign

Warning: potentially toxic cyanobacteria (blue-green algae) are present in this river/stream and may affect the health of persons or animals coming into contact with the water.

Contact with the water may cause skin and eye irritation. Drinking or accidentally swallowing water may result in illness.

Cyanobacteria usually occur as dark brown/black mats attached to rocks. These mats can detach and accumulate along the riverbank.

Don’t let your dog eat anything from the riverbank or come in contact with the water. Contact your vet or doctor immediately if illness occurs.







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Medium risk sign – Greater Wellington Regional Council

High risk sign – Greater Wellington Regional Council