Ironman Leeds was forced to cancel its swim section after toxic blue-green algae made the water unsafe, marking the fourth triathlon affected by algae blooms this year. Competitors, who had trained for months, were informed by email just a day before the event, with some choosing not to attend on August 16 after paying nearly £700 for their place.
Event details and impact on athletes
The triathlon, which includes a 2.4-mile swim, 112-mile bike ride, and 26-mile run, saw some athletes skip the event entirely. The toxic algae, while not unusual for this time of year, has been exacerbated by continued heatwaves, according to British Triathlon, the sport's governing body.
Warm water and intense sunshine accelerate the growth of the algae. In 2022, two dogs died from suspected algae poisoning in Scotland following a heatwave-induced bloom. Freshwater swimmers are being urged to take caution, as the algae can cause skin rashes, vomiting, stomach pains, fever, and headaches in humans and animals.
Safety warnings and expert insight
Several public swimming spots, including a bathing site on the Thames in London, have advised swimmers to stay away until the blooms clear. Dr Matthew Service from the Agri-Food and Biosciences Institute (AFBI) told the BBC that blue-green algae doubles every seven to 14 days.
“So once you get to where you can see it, it's just going to keep going until either the climatic conditions change, there's not enough light for it to reproduce or it just simply breaks up with the autumn and winter weather,” he said.
Competitor reaction and organiser response
News that Waterloo Lake in Roundhay Park was “significantly” above the safety threshold angered competitors, who argued organisers should have noticed the issue earlier. Jack Chamberlain told the Guardian: “It’s something they should have been checking weeks in advance. There were something like 58 countries represented in the race, so people came from all over the world. I think with people putting in time and effort and, you know, thousands of pounds into such events, things should be put in place.”
Ironman refused part-refund requests and discount codes for following events, which can cost around £750. The organiser has been approached for comment. An Ironman Instagram statement on Saturday said it was “disappointed to announce that today’s swim practice and the swim portion of Sunday’s race will not take place”, after making the decision with Leeds City Council and following advice from the UK Health Security Agency Environmental Hazards Team.
A spokesperson for the Ironman Group said: “Ironman was devastated to have to cancel the swim portion of this year’s Ironman Leeds. We know how hard our athletes train across all three disciplines (swim, bike, run) and how disappointing it was to forgo the swim segment due to water quality issues. Continuous hot weather and the absence of rain contributed to a bloom of blue-green algae, which can be hazardous to humans and made the lake unsafe for swimming. The decision to cancel the swim was made in conjunction with Leeds city council, who has jurisdiction over Waterloo Lake. 2026 was the second edition of Ironman Leeds; the swim was successfully conducted the previous year.”
