The Office of Environmental Health Hazard Assessment (OEHHA) has proposed to the State Water Resources Control Board (Water Board) acute notification level (NL) recommendations for four cyanotoxins as follows: 

Cyanotoxin  Recommended Acute NL (up to 1 day)  Health Effect(s) Peer-Reviewed Study
Anatoxin-a  8 µg/L*  Neurotoxicity  Fawell et al. (1994, 1999)
Microcystins 3 µg/L Liver damage Chernoff et al. (2021)
Cylindrospermopsin 3 µg/L  Liver & kidney cell death Bazin et al. (2010)
Saxitoxins 0.5 µg/L Neurotoxicity  EFSA (2009)

* µg/L means microgram per litre, a water concentration corresponding to a part per billion. 

Cyanotoxins are toxins produced by cyanobacteria, also known as blue-green algae, during algal growth. These acute NL recommendations represent the recommended maximum intensities that people can consume over 24 hours.  

They are additional to the short-term (up to one month or three months) NL recommendations provided to the Water Board on May 3, 2021. The acute NL recommendation for saxitoxins keeps posted the value formerly submitted to the Water Board. 

Notification levels are health-based advisory levels founded by the Water Board’s Division of Drinking Water (DDW) for chemicals that lack drinking water regulatory standards (maximum pollutant levels, or MCLs). When chemicals are found at intensities greater than their NLs, some conditions and recommendations apply. 


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