Cyanobacteria in Freshwater

Cyanobacteria, commonly known as blue-green algae, are naturally occurring microscopic organisms found in fresh, brackish, or marine water that can release cyanotoxins into freshwater systems. These toxins can pose a serious public health risk as exposure through skin contact, or ingestion of contaminated drinking water or food can cause symptoms ranging from minor irritation to more serious illness and, in worst case scenarios, can be fatal (Svirčev et al. 2017).One cyanotoxin, microcystin-LR (MC-LR), has been classified as Group 2B, possibly carcinogenic to humans after chronic exposure (IARC 2010). Under certain environmental conditions, cyanobacteria multiply quickly and create blooms. In Canada, blooms can occur at any time of year, but are more common during summer or early falland are predicted to increase in frequency and duration due to warming temperatures associated with climate change (Hamilton et al. 2016). The resources listed here are intended to assist public health practitioners to:

• Recognise and respond to cyanobacterial blooms;
• Provide guidance regarding appropriate monitoring, management, and response to a bloom in both drinking and recreational water;
• Provide guidance on risk communication during a bloom.

NCCEH Resources

• Cyanobacteria and Drinking Water: Occurrence, risks, management and knowledge gaps for public health (2019)
  This evidence review provides a scan of the occurrence of cyanoblooms in Canada, and their relative impact on drinking water source along with an overview of knowledge gaps for public health.

• Cyanobacteria and Drinking Water (2019)
  This webinar is a two part presentation that provides a summary of the NCCEH evidence review mentioned above as well as a further assessment from the Walkerton Clean Water Centre.

• Cyanobacteria in freshwater (2017)
  This fact sheet provides a brief outline of some of the key points related to cyanobacteria and the toxins they produce.

• Irrigating Food Crops with Water Containing Cyanobacteria Blooms (2017)
  This field inquiry reviews the literature on accumulation of cyanotoxins in crops irrigated with cyanotoxin-contaminated water

Selected External Resources

• Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Cyanobacterial Toxins (Health Canada 2018) 
  Health Canada’s guidelines (following a 2016 consultation) provide the maximum acceptable concentration of total microcystins in drinking water (1.5 µg/L), and a precautionary measure to seek alternative sources for reconstituting infant formula above a reference value of 0.4 µg/L. Advice on implementing the guideline and developing an action plan to respond to cyanobacterial blooms is presented (section 3; Appendix B).

• Decision protocols for cyanobacterial toxins in BC drinking water and recreational water (Government of British Columbia, 2018) 
  This decision support document provides guidance on strategies for evaluating and managing cyanobacterial blooms in BC, with recommended approaches for communication, monitoring, stakeholder engagement, and support for unregulated water systems. Protocol decision trees are provided for responding to bloom events for drinking water and recreational water.

• Control and Treatment (USEPA, 2018) 
  This management tool provides information on how to reduce nutrient input to prevent blooms in both recreational and drinking water; remedial/mitigation measures when blooms are present; and suggestions for water supply managers to deal with cyanoblooms and toxins.

• Drinking Water Health Advisory Documents for Cyanobacterial Toxins (USEPA, 2015) 
  This webpage provides information related to EPA's drinking water health advisories for toxins from cyanobacterial blooms including detailed health effects support documents for microcystins, cylindrospermopsins, and anatoxin-A.

• Guidelines for Canadian recreational water quality – third edition (Health Canada, 2012) 
  Health Canada’s guidelines for total microcystins in recreational water (20 µg/L), including discussion of other common cyanotoxins, and risk communication advice for recreational water users.

• Managing Cyanotoxins in Drinking Water: A Technical Guidance Manual for Drinking Water Professionals (AWWA and WRF 2016) 
  This guidance document provides information on the key drinking water issues related to cyanobacteria, approaches to managing and treating cyanoblooms, and approaches for developing action plans, including communications.

• Water Research Foundation: Risk Communications Toolkit for Cyanotoxins (WRF 2018) 
  This guidance document provides advice on a 4-step process to reduce communication barriers and apply risk communication best practice to improve community awareness and understanding of cyanotoxins.

• Toxic cyanobacteria in water: a guide to their public health consequences, monitoring and management. (WHO, and Chorus and Bertram (eds) 1999).
  This book provides a comprehensive overview of cyanobacteria and impacts on health through the use of water. This guide, produced on behalf of the WHO, forms the basis of many national guidance documents in existence today.

Peer-Reviewed Articles

• A Cyanotoxin Primer for Drinking Water Professionals (Westrick and Szlag 2018) 
  This article provides an overview of the treatment and management of cyanotoxins in drinking water

• Cyanobacterial toxins of the Laurentian Great Lakes, their toxicological effects, and numerical limits in drinking water. (Miller et al. 2017) 
  This article summarizes information on the occurrence of cyanoblooms, the toxicological effects of cyanotoxins and numerical limits in drinking water.

• Mitigating harmful cyanobacterial blooms: strategies for control of nitrogen and phosphorus loads (Hamilton et al., 2016) 
  This article offers practical approaches for nutrient removal from wastewater treatment to decrease the risk of cyanoblooms.

• Acute animal and human poisonings from cyanotoxin exposure – A review of the literature. (Wood, 2016). 
  This article reviews accounts of reported incidents of mortality and morbidity from 1800 to 2010 in humans and animals, providing results by country and type of exposure (e.g. recreation, drinking water).

• Blooming algae: a Canadian perspective on the rise of toxic cyanobacteria (Pick, 2016) 
  This article reviews the current knowledge on cyanoblooms in the Canadian context.

• Toxin-producing cyanobacteria in freshwater: A review of the problems, impact on drinking water safety, and efforts for protecting public health(Cheung et al., 2013) 
  This article provides a basic introduction to cyanoblooms, and summarizes the various drinking water treatment options effective for major toxins.

This list is not intended to be exhaustive. Omission of a resource does not preclude it from having value.