Burden of Recreational Water Illness Due to Exposure to Cyanobacteria and Their Toxins in Freshwater Beaches in Canada

Swimming and other recreational water activities at public beaches are increasingly popular leisure activities among Canadians. However, harmful algal blooms caused by blue-green algae (i.e., cyanobacteria) have also been increasing reported at Canadian public beaches in recent years. These algal blooms can cause various acute illnesses among recreational water users through ingestion, inhalation of aerosols, or skin contact with contaminated water. In addition, blue-green algae blooms and their toxins can cause illnesses in pets and wildlife. Currently, baseline data are lacking on the risk of recreational water illness from exposure to blue-green algae blooms in Canada. This study will identify the burden of recreational water illness among recreational water users at four targeted beach sites in Ontario, Manitoba and Nova Scotia, over a two-year period. A prospective cohort study design will be used. The investigators will determine the risk of acquiring acute illness outcomes in recreational water users, as well as their pet dogs, that engage in different levels of water contact at beaches at risk of blue-green algae blooms. The investigators will examine differences in illness risks by gender, age, and location. Relationships between cyanobacterial cell counts, toxin levels, and environmental conditions with the risk of acute illness among participants will be determined. Overall, results will provide important data on the risk of recreational water illness from exposure to blue-green algae and their toxins in Canadian beach settings.

NCT Number	NCT06579170
Lead Sponsor	Toronto Metropolitan University Collaborators: Ontario Ministry of the Environment, Conservation and Parks, Manitoba Environment and Climate Change, Windsor-Essex County Health Unit, Canadian Veterinary Medical Association, Health Canada
Conditions	Gastroenteritis, Gastrointestinal Diseases, Eye Infections, Skin Infections, Respiratory Tract Infections, Blue Green Algae Poisoning
Enrollment	2,500 participants
Start Date	2024-06-01
Primary Completion	2025-09-15 (estimated)
Study Completion	2026-03-31 (estimated)
Updated on ClinicalTrials.gov	2025-09-09