South Canterbury DHBWednesday 15 December 2010, 2:44PM
Media release from South Canterbury DHB
The South Canterbury Medical Officer of Health has issued a warning
after water surveys of the Pareora and Opihi Rivers this week found
moderate levels of the potentially toxic blue-green algae (benthic
cyanobacteria), with algae accumulating along the river
Humans and animals, particularly dogs, should avoid the Pareora
River at Pareora Huts, and the Opihi River at Waipopo, until the
health warnings have been lifted.
South Canterbury Medical Officer of Health Daniel Williams says the
algal mats can produce toxins harmful to humans and animals. The
risk of exposure to toxins is increased when algal mats break off
and accumulate as scum along the river edge.
"Exposure may cause skin rashes, nausea, stomach cramps, tingling
and numbness around the mouth and fingertips. If you experience any
of these symptoms after contact with contaminated water, visit your
doctor immediately," he says.
Drinking contaminated water, even boiled water, from these rivers
should be avoided at all times, Dr Williams says.
Animals should be taken to a vet immediately if they come into
contact with the contaminated rivers.
Environment Canterbury is monitoring the sites and the public will
be advised of any changes in water quality.
Facts about cyanobacteria:
The algae occur naturally but can increase rapidly during warmer
weather and low river flows. It grows as dark brown/black mats
attached to rocks along the river, and may detach and accumulate
It often has a strong musty smell and algal concentrations can vary
quickly with changing environmental conditions.
Although high river levels will remove the algal bloom, mats often
accumulate onshore immediately after increased flows.
If a health warning is in place avoid contact with the water.
Although district or city councils may place warning signs, these
may not be seen at the numerous river access points, hence the need
for people/ dog-walkers to treat every low-flowing river
For further information