Establishing Guidance Levels and Risk Communication Materials for Exposures to Harmful Algal Blooms in Colorado Recreational Waters

BACKGROUND:  Freshwater harmful algal blooms (HABs) caused by overgrowth of toxin-producing bacteria are recognized as emerging ecologic issues and indicators of climate change. Exposure to HABs is of increasing concern in recreational and drinking waters due to the potential health risk for humans, domestic animals and livestock. While some states have established action levels for notifying the public of harmful algal blooms, no nation-wide monitoring or regulation of cyanobacterial toxins exist. The Colorado Environmental Public Health Tracking (EPHT) program at the Department of Public Health and Environment was asked to coordinate with the Colorado Department of Parks and Wildlife and the Colorado Department of Agriculture to evaluate available toxicological information and recommend actions protective to public health during these blooms.

METHODS:  In order to provide guidance on when to take public health action and how to communicate potential risk to recreational water users in Colorado, EPHT looked to the Environmental Protection Agency (EPA), World Health Organization, and other National EPHT network states for existing action levels. Exposure assumptions and reference doses based on professional judgment and the most recent available science were used to calculate recreational water guidelines for each cyanotoxin. Concurrently, communications and subject matter experts created risk communication strategies and proposed language for signage, press releases, fact sheets and other materials.

RESULTS:  Colorado EPHT collaborated with water quality experts to develop a decision-support tool for use in determining when to post advisories or issue closures around affected water areas, when to increase the frequency of cyanobacterial toxin sampling, and when to notify drinking water providers and local health departments. Colorado elected to adopt the recent EPA recommendations for acceptable/permissible levels in drinking water. Colorado also developed fact sheets for the public, physicians and veterinarians along with draft “Caution” and “Warning” signage for posting in affected areas when there is a risk of exposure to toxins. These materials were shared across agencies and with stakeholders.

CONCLUSIONS:  Effective decision-support tools, risk communication strategies, communications materials, and coordination among agencies and stakeholders are needed to address the public health ramifications from HABs. Along with the advancement of research and development in clinical and laboratory analysis of algal toxins, the best tools available are accurate information and education. Having the resource of a network of EPHT states, actively involved in HABs research, was key to a rapid and successful creation of these guidance measures.