Background: Why the algae are dangerous
According to public health documents found on the Internet, the world's largest recorded anabaena outbreak occurred in 1991-92 along a 620-mile stretch of the Barwon-Darling River in Australia. A state of emergency was declared, and drinking water supplies were bought into all areas dependent on the Barwon-Darling as a water supply.
Many sheep and cattle died along the river, and samples of the algae from the water were found to contain the same paralytic poisons that are present in poisonous shellfish.
No human illness was reported, however, as anabaena typically forms in surface scums. Concentrated cells can be drunk by livestock, but drinking water supplies normally are drawn from deeper areas of a reservoir.
Although humans ordinarily avoid drinking water that displays a blue-green bloom or scum, they may be affected by toxic strains when they swim or ski in recreational water bodies during a bloom. Typical symptoms include redness of the skin and itching around the eyes; sore, red throat; headache; diarrhea; vomiting; and nausea. Human death has not been documented.
Boiling water with the algae in it doesn't help, said Morgan Marler of the Hillsboro water department. The temperature would instead release the toxins, making it more dangerous.
After the outbreak in Australia, researchers there investigated which water treatment processes were most effective for removal of the toxisn. Ozonation was found to be ineffective. Chlorination was found to be effective at high pH. Activated carbon, both in the granular and powdered form, was found effective for reducing toxicity.
Several toxins can be created by anabaena.
The hepatotoxin microcystin produced by anabaena causes blood to collect in the liver, causing circulatory shock. It could lead to death by liver failure. Hepatotoxins can cause weakness, vomiting and diarrhea. Microcystins can accumulate in aquatic invertebrates such as mussels, so aquatic animals caught from water where there is an algal bloom should not be eaten.
Anabaena also produces two types of neurotoxins, anatoxin and saxitoxin, that interfere with the functioning of the nervous system and can cause death of humans and animals within minutes by causing paralysis of the respiratory muscles. Saxitoxin is the same poison found in aquatic "red tides."
"These toxins need to be removed from the water supply before it is supplied for domestic use and consumption, or an alternative supply sought," the Australian researchers looking into the Barwon-Darling bloom concluded.
In the United States, the Environmental Protection Agency has placed the broader class of blue-green algae to which anabaena belongs on the Drinking Water Contaminant Candidate List in accordance with requirements of the Safe Drinking Water Act, as amended in 1996.
In 1998, these algae were listed as priorities for additional health research, treatment research, and analytical methods research. To date, however, there is no drinking water standard in the United States or from the World Health Organization for the toxins.
The algae typically bloom in spring amid an abundance of nitrogen nutrients, presumably from agricultural runoff.
This is the first time such an incident has taken place in Kansas since 1989, Marler said.
