Check for health warnings before going near waterways

Swimming Water QualityRecreational water users are being reminded to avoid contact with some Canterbury and South Canterbury waterways.

Dr Alistair Humphrey, Canterbury Medical Officer of Health, says health warnings remain in place where there’s potentially toxic blue-green algae (cyanobacteria) in a number of areas around the regions.

“Make sure you check the health warnings for toxic algae before going near any waterways. And if in doubt, keep out.” Dr Humphrey says.

Harmful effects of toxic algae on humans and animals

Algal blooms can produce toxins harmful to humans and animals. People should avoid contact with the water where algal blooms are present until further notice. The algae is particularly dangerous for dogs.

“Animals that show signs of illness after coming into contact with toxic algae should be taken to a vet immediately. Symptoms of cyanobacteria poisoning in dogs include panting, lethargy, muscle tremors, twitching and convulsions – which usually occur within 30 minutes of exposure.”

Dr Humphrey says people who come into contact with toxic algae can also experience unpleasant symptoms. “Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the water,” Dr Humphrey says.

People should never drink water from a waterway where a health warning is in place and they should also avoid eating fish and shellfish taken from areas where warnings are in place. “Boiling the water does not remove the toxin. If fish are eaten, remove the gut and liver and wash in clean water.”

Environment Canterbury Chief Scientist Dr Tim Davie says it is not possible to monitor every reach of every stream and river in Canterbury so we concentrate on sites where we know people swim. “We monitor 52 popular freshwater swimming sites in Canterbury and similar number of beaches; the results are shown on the Environment Canterbury and the LAWA websites (Land, Air, Water Aotearoa),” Dr Davie says.

“If you’re swimming at non-monitored sites then we encourage you to check the stream bottom for what look like black mats.  If there are significant black mats and particularly if bits are breaking off then you should not swim or allow dogs to the site.”

Facts about cyanobacteria

  • The algae occur naturally but can increase rapidly during warmer months.
  • Avoid all contact if the water is cloudy, discoloured, or has small globules suspended in it.
  • Not all cyanobacteria blooms are visible to the naked eye and toxins can persist after the blooms disappear.
  • Cyanobacteria concentrations can change quickly with changing environmental conditions such as wind.
  • Avoid contact with the water if a health warning is in place.

Source: Canterbury District Health Board media release (2nd February 2017).

Published on Friday, February 3rd, 2017, under Uncategorised
Page last updated: 30/05/2017

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