Warmer climates combined with excessive nutrient loading are leading to increases in the occurrence of harmful algal blooms (HABs) and associated algal toxins in many water supplies. The recreational and ecological impacts of HABs, such as recreational restrictions, dead zones and the related economic impacts, have received significant attention, but concerns for the impacts on drinking water quality have been less prominent since advanced surface water treatment most often takes care of any potential drinking water impacts before they become apparent to the public. Unfortunately, this is starting to change and an increasing number of utilities are reporting levels of algal toxins that are difficult to remove with existing treatment systems.
The topic garnered significant discussion during NDWAC’s December 2013 meeting, taking up most of the meeting’s second day. Presentations to NDWAC on recent problems faced by utilities in addressing HABs highlighted the need for increased scientific research, particularly for algal toxin identification, testing and treatment technique evaluation and development. Significant work is also needed to establish health effects and exposure data that could be used to set thresholds that would better inform the issuance of health advisories and help water utilities structure responses to algal toxin contamination events. Based on the presentations and its discussions of the issues, NDWAC is contemplating making recommendations to the EPA Administrator for increasing its focus on the issue and potential actions to better understand the science and regulatory implications of the increasingly prevalent threat to drinking water supplies.
EPA staff indicated to the NDWAC that plans for addressing algal toxins in water supplies are already in motion. Based on increased concerns, algal toxins will be getting a very thorough look as the development of the fourth contaminant candidate list (CCL4) progresses and the fourth Unregulated Contaminant Monitoring Rule (UCMR4) moves forward. This process, as with any contaminant, puts algal toxins on a preliminary path towards a potential regulatory determination and new drinking water regulation. More immediately, several states and individual utilities that have been on the front lines in combating algal toxin threats are working aggressively on their own to ramp up programs dealing with algal toxin threats.