Cyanobacterial Blooms at Beaches Study

Cyanobacterial blooms are increasingly common in Canadian freshwater recreational water bodies, posing health risks to humans and animals due to toxin exposure. However, limited data exist on illness risks associated with recreational water contact at affected beaches. This study aims to fill this gap by investigating recreational water illness linked to cyanobacterial blooms at popular beaches in Ontario, Manitoba, and Nova Scotia.

Project Updates

2024-2025 Cohort Study:

In 2024 and 2025, surveys were administered at four beaches in Manitoba, Windsor-Essex Region (Ontario), Durham Region (Ontario), and Halifax to gather data on recreational water user activities and possible exposures to cyanobacteria (i.e., blue-green algae). This was followed by a 3-7 day illness survey. Dog owners were also recruited to gather information about dog exposures. Water sampling was conducted to measure cyanobacteria levels, toxin concentrations, and pigment levels.

A total of 2,282 individuals participated, with 66.6% completing the follow-up. Nearly half (45.7%) engaged in water contact activities, primarily swimming (34.8%) and wading (23.4%). Approximately 8.3% reported swallowing water, nearly half (46.6%) of whom were children ≤14 years old. Overall, acute gastrointestinal illness incidence was 2.1%, increasing from 1.3% among non-swimmers to 3.0% among those with water contact. Among 256 dogs, 65.6% entered the water and 56.3% were observed with water in their mouths. Cyanobacteria counts were generally low, though sporadic peaks occurred.

The results are still being analyzed. Check back again soon for more updates!

Read our study protocol and methods here.

2023 Focus Groups:

Focus groups were conducted with parents and dog owners from across Canada to gather information about their awareness of and practices toward cyanobacterial blooms in Canadian beaches. A summary of these results is shown in the infographics below.