Health effects associated with blue-green algae have been studied more comprehensively than ever before in a recently concluded research project. The study focused on the toxicity of Finnish blue-green algae blooms, the factors that caused the reported poisonings, and the diversity of the bacteria living together with blue-green algae.   

More than 600 samples of blue-green algae blooms were analyzed for their species composition and toxins. Some 130 of these samples were related to reports of adverse health effects. More than 150 patients were interviewed and their symptoms were compared with the results of water samples. The purpose of the interviews was to survey the exposition patterns, the occurrence of various kinds of symptoms, and the duration of the symptoms. Usually the symptoms started less than one day after the exposition and their duration was normally less than three days. This was the first time such a comprehensive survey of acute human symptoms caused by blue-green algae has been made.

Among the most common health symptoms associated with blue-green algae were stomach symptoms, such as nausea, vomiting, and diarrhoea, as well as fever, skin symptoms, and muscle pains. The most common type of exposition was swimming, but the largest number of symptoms was caused by the use of bathwater contaminated with blue-green algae. Beyond toxins in the strict sense of the word, blue-green algae can produce other compounds that cause eczema, fever, and symptoms similar to hay fewer.

For the first time in Finland, it was found that blue-green algae samples contain the strong neurotoxin called saxitoxin. Large concentrations of this toxin were found in the species Anabaena lemmermannii. Neurotoxins were found in lakes that are assumed to be rather healthy
- in oligotrophic, clear-watered lakes in which the number of blue-green algae species has been rather low and the blooms have typically been small. A slight eutrophication in these lakes seems to favour those blue-green algae which produce neurotoxins.

Hepatotoxins, on the contrary, were found in rather eutrophic and dark-watered lakes in which blue-algae blooms have been a well-known phenomenon. The concentrations of liver toxins in the symptom-related samples were relatively low. The symptoms seem to be associated with blue-green algae in general rather than with the concentrations of hepatotoxins.

Some results of the research project suggest that some of the symptoms associated with blue-green algae may actually be caused by bacteria. Several new bacteria, living together with blue-green algae, were identified in the samples. A scientific description was given to a new bacterial genus that dissolves the neurotoxins produced by blue-green algae. A number of other bacterial species, possibly pathogenic to humans or animals, were isolated from the bloom samples. These bacteria have not previously been studied.     

The telephone service of the Poison Information Centre gets annually some 100 calls from people who suffer from symptoms presumably related to blue-green algae. The algae telephone of SYKE answers annually to some 350 questions about blue-green algae. The algae telephone service (Levälinja) will again be opened in June.

The research project was a part of the research programme MICMAN (Microbes and Man) which was funded by the Academy of Finland. The blue-green algae project was carried out by the Finnish Environment Institute, the Poison Information Centre of the Hospital District of Helsinki and Uusimaa, and the National Product Control Agency for Welfare and Health (STTV). The nation-wide algae monitoring and the sampling were carried out by the regional environment centres, by municipal environment and health inspectors, and by voluntary algae observers.

More information:
Ms Liisa Lepistö, professor, Finnish Environment Institute (SYKE), phone 040 740 1697, firstname.lastname@environment.fi

Mr Jarkko Rapala, chief inspector, National Product Control Agency for Welfare and Health (STTV), phone (09) 3967 2810, firstname.lastname@sttv.fi

Ms Sirpa Pellinen, information officer, Finnish Environment Institute (SYKE), phone (09) 4030 0703 or 040 7402 754, firstname.lastname @environment.fi

Ms  Eija Iivari, information officer, Product Control Agency for Welfare and Health (STTV),phone (09) 3967 2787, firstname.lastname@sttv.fi