Case study: Monitoring and risk management practices of blue–green algae blooms within the regional municipality of Halton

Abstract

Cyanobacteria pose a threat to public health in waters affected by seasonal blooms. There have been sporadic occurrences of cyanobacterial blooms at an increasing number of public beaches in Halton Region, Ontario, Canada. Even though cyanobacteria may not be visibly present, the risk of exposure to cyanotoxins remains and requires consideration for an effective risk management and monitoring program. The objective of this case study is to provide best practices that may aid local Health Departments in setting up a cyanobacteria monitoring program. Public health inspectors are responsible for visual monitoring of public beaches that takes place on a weekly basis while conducting routine surveillance. Currently, when cyanobacteria are visually identified, a beach posting is issued. A complete risk assessment is completed to determine the acceptability of reopening the beach for public use. It is recommended to implement an approach that involves both visual monitoring and toxin testing using a field test kit. For a beach to be considered safe for bathing, surveillance should indicate a visual absence of a bloom and microcystin test results below Health Canada’s recreational water standard of 20 ppb. This case study highlights Halton Region’s response to cyanobacteria blooms in recreational waters in accordance with the prescribed protocol and guidance document.