What The EPA Health Advisory On Algal Toxins Means For You
On May 6, the U.S. EPA issued a health advisory regarding elevated levels of algal toxins in drinking water. Following a cyanotoxin crisis that resulted in a water ban in Toledo last August, the agency recommended specific drinking water values for microsytin and cylindrospermopsin in advance of the summer bloom season.
The advisory recommends a microsytin level of 0.3 micrograms per liter (µg/L) and a cylindrospermopsin level of 0.7 µg/L for children younger than school age. For older children and adults, the recommended values are 1.6 µg/L for microcystin and 3.0 µg/L for cyldinrospermopsin.
While algal toxins pose no immediate health threat, the EPA cites gastroenteritis, liver, and kidney damage as potential health effects from exposure to high levels of these toxins exceeding 10 days. The agency deems the detection and treatment of these harmful algal blooms (HABs) as imperative.
Prevention
The EPA recommends preventative action as the first line of defense against algal toxins.
“It is important for drinking water systems to pay attention to vulnerability of their source waters to HABs, and to work with upstream partners to promote effective management of excess nutrients that contribute to HAB formation,” the agency said in an interview elaborating on the advisory. “Water supply managers are encouraged to pay careful attention to characteristics of their watershed that could contribute to the formation of HABs. Preparation and early action following a detection may result in quick mediation of the problem.”
The nutrients that most typically lead to HABs are nitrogen and phosphorous. Targeting nutrient sources such as discharge from sewage treatment plants, animal feeding operations, agricultural runoff, roads, and stormwater can reduce the chances of these nutrients reaching the water.
The other key factors to be aware of are sunlight, as algae is photosynthetic, and rising temperatures, which create the cyanotoxins’ preferred climate. The typical bloom season lasts from late May to early September.
For the preemptive control of phosphorous in a water source, the EPA recommends precipitating the nutrient and then dredging it out as sediment. This can be achieved by adding alum, ferric salts, or clay.
Detection
On its website, the EPA notes that algae are often identifiable through an eye test. Signs of HAB presence include water discoloration and thickness, accumulations on the shoreline and surface, and fish kills.
When testing water samples for potential toxins, the EPA cautions labs to store them in amber glass containers that will prevent the cyanotoxin adsorption caused by plastic containers and minimize exposure of the sample to sunlight. Quenching and chilling samples immediately after collection is also recommended.
To measure total cyanotoxins (both the intracellur and dissolved toxins), rupture the cyanobacterial cells (lysing) to break the cell wall and release the toxins into the solution. The EPA recommends studying the sample under microscope to determine the effectiveness of lysing. To read more about testing for cyanobacterial toxins, review the USGS Guidelines.
In the advisory, the EPA notes the presence of a “diverse range of rapid screen tests and laboratory methods” that can be used to identify cyanobacteria and cyanotoxins in water. It recommends employing more than one of these methods, as a single one will not accurately quantify the several cyanotoxins that are likely present in the sample. For analyzing microcystins, the EPA recommends several methods adapted from a presentation given at the 2010 National Water Quality Monitoring Conference.
Some utilities and industry thought leaders have voiced concern over the expense and time requirement that will come with such testing.
“There is a little problem, I think, from the utility point of view,” said Dr. Djanette Khiari, a research manager at the Water Research Foundation who specializes in algal toxins. “We have standard monitoring methods in place that are quick, the turnaround time is short, but they lack accuracy. The 0.3 recommendation is a little stringent because of the standard deviation associated with these tests. Utilities are going to have to do intensive monitoring and that is going to be very resource-extensive.”
Khiari cited a microsytin level of 1 µg/L as an industry standard adopted by the World Health Organization, which utilities are better suited to adhere to through current testing methods. She speculated that the lower-level recommendation from the EPA comes as a direct result of the crisis in Toledo and that it may be unnecessarily strict.
“EPA’s health advisories reflect the latest science on algal toxins and the effects of more short-term exposures on both adults and children,” the EPA said, in defense of the recommendation for lower microsystin levels.
It is worth noting that the health advisories do not require states or drinking water utilities to test, treat, or communicate with the public regarding HABs.
Control/Treatment of HABs
If blooms have already occurred, there are methods for mitigation. For one, you can physically remove surface scums or apply algaecides such as copper sulfate and lime to blooms. However, the use of algaecides can result in cell-breaking and the release of toxins into the water source, which can harm natural plant and wildlife.
Cyanobacteria and cyanotoxins can be mitigated during standard drinking water treatment processes such as flocculation, coagulation, sedimentation, and filtration. The EPA provides a table which lists the various water treatment techniques used for cyanotoxin removal and their respective effectiveness.
“The treatments we have within the drinking water utility right now should take care of the problem, unless there is a major catastrophe and there is a bloom so extensive that we have not seen it,” said Khiari.
Chlorination, a conventional treatment at most water utilities, will affect cyanotoxins differently, but microcystin and cylindrospermopsin are both susceptible to chlorination. Other standard disinfection techniques such as ozone and UV light have also proven to be effective against cyanotoxins.
The EPA recommends advanced processes like powdered and granular activated carbon adsorption to remove extracellular toxins.
Next Steps
“EPA will finalize the health advisories before June 15 of this year in response to the requests from Congressional members, the Great Lakes mayors, and the Great Lakes states that we do so prior to the next HAB season,” the agency said.
As we await the final advisories, Khiari says there are some burning questions that water utilities hope to have answered by this June 15 deadline.
“What the utilities need now, basically, is for the EPA to give good methods and good guidelines to be able to monitor and to know how often to do so,” she said. “They need answers because with the right ones, this can be handled.”