Blue-Green Algae Science Limited

The International Triathlon Union (ITU) has set water quality standards which are consistent with the WHO standards. For inland, freshwater, these standards cover pH, bacterial levels and blue-green algae levels. For more information see the current guidelines, section 10.1.  The Environment Agency will advise an organiser if the test results are in the RED zone, but the likelihood is that the event cannot proceed if the test results are in the RED zone (see above).  ITU does not have water quality grading, water is only acceptable and non-acceptable.

The Olympic Standards for outdoor freshwater sports follow the rules set by the respective sporting associates and unions. There are additional requirements for what is termed a "comprehensive test" of the waterbody, where the risk of exposure to all known pathogens, bacteria and sediment related toxins is reviewed. The aim of this test is to define the key parameters to be monitored. For the London Olympics, this resulted in a special focus on the monitoring of blue-green algae and the algae species that dominated the Serpentine in Hyde Park.

Rapid Testing Kits for Cyano-toxins in Freshwater

Cyano-toxin Safety Limits

Threshold levels for cyano-toxins in drinking water or recreational water have been established by a variety of organisations. In the UK, the Environment Agency, HPA/PHE, SEPA and the DWI set the standards.

Threshold levels for cyano-toxins in drinking water or recreational water have been established by a variety of organisations. In the UK, the Enviroment Agency, HPA/PHE, SEPA and the DWI set the standards. These standards should be consistent globally, but we often refer to a variety of organisations to ensure that up to date advice is being considered.

Traffic light system for use responding to cyanobacteria incidents, UK Health Protection Agency (2012), based on WHO, 1999. Grey items are additional WHO reference levels.


Drinking Water Standards

In the UK, the Health Protection Agency guidance advice (2012) is that water cannot be abstracted if it contains cyano-toxins. When using the cyano-toxins test strips, if they show the presence of cyano-toxins, abstraction of drinking water should be stopped. This is an absolute.

The World Health Organisation (WHO) has set standards for some key toxins in drinking water and the EU (Drinking Water Directive) has implemented some of these standards.  These standards have not been clearly adopted in the UK. Likewise the US EPA has issued Health Advice notices on defined limits of cyano-toxins, which are lower than the WHO limits, but effectively state that the presence of cyano-toxins in drinking water is not permitted, especially if you consider the impact on young children. These non-UK documents do not override the guidance issued by the Heath Protection Agency / Public Health England, as stated above.

In the UK, access to water potentially containing cyano-toxins is not prohibited, but a three stage risk assessment is adopted by the Environment Agency and Scottish Executive. This risk assessment is managed by the regulator following notification of a potential harmful algae bloom (HAB).  When using the cyano-toxins test strips for recreational water, if they show the presence of cyano-toxins over 10 ug/l, then the water will be classified as AMBER. Once in the Amber Zone, notification should be given to the Environment Agency, NRW or SEPA who will monitor and advise the users / owners from this point onwards.

Recreational Standards

Red (HPA)

Cyano-bacteria scums.

>100,000 cells / ml with dominance of cyano-bacterial cells.

>50 ug/l of chlorophyll-a

Amber (HPA)

>20,000 cells / ml with dominance of cyano-bacterial cells.

>10 ug/l of chlorophyll-a

Green (HPA)

<20,000 cells / ml of cyano-bacterial cells.

Very High (WHO)

Cyano-bacteria scums.

>10,000,000cells / ml with dominance of cyano-bacterial cells.

Microcystin-LR >2000 ug/l (WHO)

Microcystin-LR >20 ug/l (WHO)

Microcystin-LR >10 ug/l (WHO)

Microcystin-LR <10 ug/l (WHO)

Competitions e.g.,

Triathlon / Olympic Stardards


London Olympics, Triathlon

Serpentine, Hyde Park (LOCOG 2012)

Home Page

US - EPA Guidelines


US - EPA image used in the "Best to Stay Out" awareness campaign on blue-green algae.

UK and EU Vote

24th June 2016: Following the UK's decision to leave the EU, standards currently set to  protect water users are unlikely to change. The EU guidelines followed the World Health Organisation standards, and the UK is likely to following these same standards, as does the US, Switzerland and Norway. There will be changes in the way that the Environment Agency operates, they will no longer need to report to the EU on compliance, but the EA will continue to report to Parliament.