There is no single, universally applied method for assessing cyanobacteria risk. Across the United States, approaches vary in the monitoring methods, criteria, thresholds, and risk categories that are used. This isn’t unique to cyanobacteria. Risk frameworks are developed by the people and agencies responsible for making decisions, drawing on their expertise, experience, priorities, and the information available to them at the time.
In Massachusetts, the Department of Public Health (MassDPH) provides guidance for assessing cyanobacteria risk in recreational waters, while decisions about public health advisories are made by local health authorities. As a result, the way cyanobacteria conditions are evaluated and communicated can vary from town to town.
At APCC, we monitor ponds across multiple towns, so we need a consistent and transparent way to communicate what our monitoring is finding. Our risk tiers lean on MassDPH guidance, while also providing an intermediate category for conditions that may warrant additional caution without constituting a public health advisory.
Consider a pond where monitoring finds elevated levels of cyanobacteria and significant growth, but the available information does not meet the criteria for a public health advisory. Does that mean there is nothing to think about? Not necessarily. Someone swimming with young children or a dog may choose to be more cautious, while someone else may decide the same conditions don’t change their plans.
That middle ground can be useful information. Several Cape Cod towns already use warning or pet-advisory designations for conditions that don’t warrant the issuance of a public health advisory, but may be worth bringing to people’s attention. We hope to continue working with local decision-makers toward more consistent communication around this middle range.
APCC’s risk tiers are not public health advisories. When a town issues a public health warning or advisory and communicates it to APCC, we reflect that designation on our map. The town’s designation remains the official public health guidance.
There isn’t necessarily one “right” way to organize all of this information; assessing cyanobacteria risk is not always straightforward. What matters is understanding what a designation means, who issued it, and what it is intended to communicate. We also recognize that having different types of information can be confusing, which is why we’re continuing to work on making our communication around cyanobacteria risk as clear as possible.
