Harmful algae

Health effects

Water contaminated by blue-green algae constitutes a health risk to humans.

Drinking water

Due to the toxins they may produce, blue-green algae can affect water consumers in a number of ways. They have been associated with nausea, headache, vomiting, abdominal pain, diarrhoea, gastroenteritis, muscle weakness, pneumonia and paralysis.

Note: Boiling the water will not destroy toxins. Boiling will kill algae but in doing so will release toxins into the water. In fact some toxins become more dangerous as a result of boiling the water.

Skin contact

Contact with blue-green algae (toxic and non-toxic forms) through water-based activities can cause problems such as

  • skin rashes
  • swollen lips
  • eye irritation and redness
  • ear ache and itchiness
  • sore throat
  • hayfever symptoms
  • asthma
  • and possibly promotion of skin tumours.

The risk of problems is likely to grow as contact time increases.

Eating fish from algae-affected waters

The identification of Paralytic Shellfish Poisoning (PSP) toxins in one of the species of blue-green algae in Australia has highlighted concerns about possible neurotoxin bioaccumulation in edible mussels and other shellfish.

In marine waters, consumption of shellfish contaminated by PSP has caused many human deaths. Cylindrospermopsin, another blue-green algal toxin common in Queensland freshwaters has been identified in the edible flesh of crayfish. Therefore, mussels, yabbies and other shellfish caught in algae infested waters should not be consumed.

In this guide:

  1. Blue-green algae in freshwater
  2. Reporting outbreaks
  3. Health effects
  4. Livestock and farm dams

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