EPA issued new recommendations May 22 for water quality criteria and swimming advisory values for both microsystins and cylindrospermopsin, two cyanotoxins caused by harmful algal blooms (HABs). Algal blooms occur each year and though not all are harmful to human health, those that are can cause health problems in individuals that swim or participate in other recreational activities where HABs are found.
EPA has established recommended water concentrations, at or below which protects public health, at 8 micrograms per liter for microcystins and 15 micrograms per liter for cylindrospermopsin. These recommendations are based on the latest peer-reviewed scientific research and are protective of all age groups.
According to the document, “EPA envisions that if states decide to use the values as swimming advisory values, they would do so in a manner similar to their current recreational water advisory programs. Alternatively, states may consider using these same values when adopting new or revised water quality standards (WQS). If adopted as WQS and approved by the EPA under the CWA section 303(c), the WQS could be used for all CWA purposes. States may also wish to consider using these values as both swimming advisory values and WQS.”
The agency will soon release draft technical support materials for public comment that, when finalized, are intended to help states and tribes implement these recommended values. According to EPA, these materials will include “information on waterbody monitoring, assessing attainment of water quality standards, listing of impaired water bodies and developing total maximum daily loads under Clean Water Act section 303(d).”