Cyanobacterial Toxins -- Microcystin-LR

Annex A: Stepwise Protocol for Microcystin-LR in Water Supplies Used for Human Consumption

Preamble

Summer conditions can lead to the growth of blue-green algae in bodies of water (generally smaller or shallow lakes, reservoirs, sloughs or dugouts) throughout Canada. In many cases, blooms tend to recur within the same bodies of water year after year. While most species of blue-green algae are capable of producing nerve and liver toxins, not all blue-green algal blooms produce toxins, and, when present, the amount of toxins varies dramatically within the body of water and over time. Analytical studies over the past few years in dugouts and other water supplies in Manitoba, Saskatchewan and the Peace River region of Alberta indicate that blue-green algal toxins are much more common in rural water supplies than originally thought. Although there are few quantitative data available, there are indications that these toxins may also be occurring in various water supplies in other provinces (e.g., Ontario, British Columbia, Quebec and Prince Edward Island).

The factors inducing the production of toxins by cyanobacteria are not well known. Laboratory studies demonstrate that some environmental factors, such as temperature, light, nitrogen concentrations, carbon availability (in the form of bicarbonate, carbonate and carbon dioxide), phosphate concentrations and pH, could be important. As toxin production varies greatly among different strains of the same species, genetic differences and metabolic processes may also be important in the production of these secondary metabolites. Studies have shown that the ability to produce toxins can vary temporally and spatially at a particular site.

Cyanobacterial toxins tend to be associated with cyanobacterial cells and may be membrane bound or occur free within the cells. In laboratory studies, most of the toxin release occurs as cells age and die and passively leak their cellular contents; some active release of toxins can also occur from young, growing cells.

Toxin levels do not necessarily coincide with maximum algal biomass; there can be significant variation in the amount of toxin per unit biomass of cyanobacteria over time, which is independent of changes in the blue-green algal population. Concentrations of microcystins were higher in blooms taken during the day than at night in one study, for example, and no significant difference in toxin concentrations from cyano-bacteria incubated for 24 hours at different depths in a reservoir was observed in another study. Microcystins are relatively persistent in the aquatic environment. Studies in Australia have shown that microcystin-LR was present up to 21 days following treatment of a Microcystin aeruginosa bloom with an algicide.

Recent studies have led to increasing concern by government agencies and the public regarding the safety of water supplies that may be potential sources of these toxins.

The purpose of this annex and the accompanying flow chart (see next page) is to provide water purveyors and health and environment authorities with a summary of the important factors that should be considered during bloom events and recommendations on actions that may be taken to address the issue.

Step 1: Visually monitor for bloom formation

As blooms tend to recur in the same water supplies, water bodies that have historically exhibited algal blooms should be visually monitored for bloom formation and hence toxin production during the peak season (usually late May to early October). Authorities should visually monitor supplies for algal growth and conduct sampling during and after collapse of the bloom. As well, bodies of water that, due to variables such as size, water depth and nutrient content, may be susceptible to algal blooms should be considered for monitoring programs. Toxins may persist following the collapse of blooms, particularly in the late summer and early fall, when the onset of colder temperatures and decrease in light intensity result in decreased rates of toxin degradation.

A visual bloom is identified by the appearance of "soupy" water. Colours can range from grey or tan to blue-green or bright blue or reddish. The appearance of blooms may also be described as fine grass clippings or small clumps.

Step 2: Sample raw¹ and treated supplies for toxin (algal identification)

Samples of raw and treated supplies (if applicable) should be taken at the same time in order to save time and money. For laboratory analysis, raw water samples should be collected prior to any treatment, including filtration; samples from the raw water tap at the treatment plant are acceptable if no pretreatment is applied. Sampling from a reservoir should be done as close to the inlet/shore and/or the bloom formation as possible. However, when possible, it is suggested that samples from several sites be pooled for the determination of toxicity, as cyanobacterial species/cell abundance and biomass vary spatially within a water body (e.g., cells may be transported by wind currents). Treated samples should be taken at the treated water tap of the treatment plant or within the distribution system.

Samples, in amounts required by the analytical laboratory, should be collected in glass containers, as studies indicate that the toxin, if present, can be adsorbed to the plastic.

Agencies may also wish to sample for algal identification. Species identification, especially from sites positive for toxin, can provide additional information regarding the source, conditions and type of other toxins that might be present.

1. A field test kit coater supply. If the presence of toxin is detected in a sample using the field test kit, the sampling agenuld be used as a screening tool to determine the presence or absence of toxin in a wcy will need to submit a sample to a recognized laboratory for confirmatory analytical analysis (see Step 3).

Step 3: Send both raw and treated samples for microcystin-LR analysis

Both raw and treated samples should be sent (in coolers) to the laboratory for analysis as soon as possible (preferably within 24 hours). Sampling agencies should contact their local or regional departments of health or environment for information on laboratories capable of conducting toxin analyses.

Upon receipt of samples from sampling agencies and in order to avoid unnecessary costs, the laboratory should store the treated samples until the results of the microcystin-LR analysis of the raw samples are available. A microcystin-LR result of >1.0 µg/L in the raw sample will cause further action, as outlined in Steps 4-10.

Step 4: Microcystin-LR >1.0 µg/L (raw)

Results will be reported to the sampling agency, as per Step 12 (raw). A result of >1.0 µg/L should cause further action, as outlined in Steps 5-10.

Step 5: Perform toxin analysis of treated water samples

Testing will be performed on treated samples when a level of >1.0 µg microcystin-LR/L is found in a raw sample from the same site.

Step 6: Microcystin-LR >1.5 µg/L (treated)

A result of >1.5 µg microcystin-LR/L for the treated sample will cause the sampling agency to take appropriate action, as outlined in Steps 7-10. Microcystin-LR results of >1.5 µg/L in a treated supply will result in a resampling of the treated supply as soon as possible (Step 9) and notification of the community and appropriate agencies (Step 7).

Step 7: Notify community and agencies

Upon receiving the results, the sampling agency will follow standard protocol for notifying communities and appropriate agencies. Consideration will be given as to which agency should be taking the lead role in this regard. Additionally, the investigation should take into account the history of the source/supply and the type of treatment at the plant. Dialysis treatment units in the community should also be notified, especially if it is a first-time occurrence for blooms on this supply. A Health Canada fact sheet on microcystin-LR (It's Your Health: Blue-Green Algae (Cyanobacteria) and their Toxins) is available to help convey information to communities.

Step 8: Consultation and decision-making

In the case of community (municipal) supplies, risk assessment discussions should take place regarding additional action to be taken. Health agencies, municipal councils and the lead regulatory agency responsible for municipal systems should be included in these discussions. The risk assessment discussion process should include, for example, such items as the history of the site, the size and location of the bloom, available treatment technology (if a treated site), uses of the source water (recreational versus domestic uses) and monitoring of the environmental conditions that might affect the bloom (e.g., wind). Where possible, lysing of the bloom by the addition of copper sulphate or Blue Stone should be avoided, as this action will immediately release toxin from the cells into the water supply. If the bloom is a common occurrence, nutrient monitoring may be considered. Weekly monitoring should be continued.

In the case of non-community (non-municipal) supplies, the sampling agency will consult with health agencies and agencies having treatment expertise.

Note: See Step 10.

Step 9: Resample treated supply

Following receipt of results indicating that the treated water contains >1.5 µg microcystin-LR/L, the treated supply will be resampled as soon as possible or as determined by the sampling agency.

Step 10: Alternative supply or treatment adjustment

During the Step 8 decision-making process, discussions regarding treatment adjustments or alternative supplies should be reviewed (Step 10). The lead agency should advise the owner of the supply of any treatment options, such as additional granular activated carbon filtration or ozonation. It should be pointed out that boiling is not effective in reducing or removing these toxins, although some point-of-use devices may be effective.

Note: As blooms may be of short duration (ranging from days to weeks), health and environment agencies may recommend, after consultations with the community (see Step 8), that consumers seek alternative supplies of safe drinking water until there is no longer a visible bloom and the toxin level has dropped below 1.5 µg/L.

Step 11 (raw): Microcystin-LR <1.0 µg/L

A result of <1.0 µg microcystin-LR/L in the raw water will cause the sampling agency to continue to visually monitor the raw water for the recurrence of blooms and resample if necessary.

Step 11 (treated): Microcystin-LR <1.5 µg/L

A result of <1.5 µg microcystin-LR/L in the treated water will cause the sampling agency to continue to monitor the raw water as per Step 11 (raw).

Step 12 (raw): Send results to agencies

Microcystin-LR results from laboratories (and field test kit results when available) will be reported to the sampling agency as soon as possible from time of receipt of the sample. Sampling agencies are responsible for reporting results to the water supply owner.

Step 12 (treated): Send results to agencies

Treated water microcystin-LR results will be reported to the sampling agency as soon as possible from the time of the positive raw water results for the same sampling site. Sampling agencies are responsible for reporting results to the water supply owner and/or responsible agencies.