Cyanotoxins

Microcystis bloom at Ohio River, 2008. Photo by Jim Crawford, Ohio EPA

The most commonly occurring groups of freshwater algae are diatoms, green algae, and blue-green algae (more correctly known as cyanobacteria). Cyanobacteria refer to a group of microorganisms that possess characteristics of algae (chlorophyll-a and oxygenic photosynthesis). They are found in fresh, estuarine, and marine waters in the U.S. Cyanobacteria are often confused with filamentous green algae, because both can produce dense mats that can impede activities like swimming and fishing, and may cause odor problems and oxygen depletion. However, unlike cyanobacteria, filamentous algae are not generally thought to produce toxins. Freshwater cyanobacterial blooms that produce highly potent cyanotoxins are known as cyanobacterial HABs (cyanoHABs). These species are capable of producing compounds that are hepatotoxic (affect the liver), neurotoxic (affect the nervous system) and acutely dermatotoxic (affect the skin). Hepatotoxic freshwater blooms of cyanobacteria are more commonly found than neurotoxic blooms throughout the world.

Anabaena bloom on Lake Pontchartrain, Louisiana, 1997. Photo by John Burns

Freshwater cyanobacterial blooms may be dominated by a single-species or be composed of a variety of toxic and non-toxic strains (i.e., a specific genetic subgroup within a particular species). Cyanotoxins are produced and contained within the actively growing cyanobacterial cells (i.e., intracellular toxins). The release of these toxins into the surrounding water, as dissolved (extracellular) toxins, occurs mostly during cell death and lysis (i.e., cell rupture) of a cyanobacterial bloom, rather than by continuous excretion from the cells.

Cyanotoxins can be produced by a wide variety of planktonic (i.e., free living in the water column) cyanobacteria. Some of the most commonly occurring genera are Microcystis, Anabaena, and Planktothrix (Oscillatoria).

Planktothrix bloom at Grand Lake St. Mary, Ohio. Courtesy of Keith Loftin, USGS

Microcystis is the most common bloom-forming genus, and is almost always toxic. Microcystis blooms are a greenish, thick, paint-like (sometimes granular) material that accumulates along shores. Scums that dry on the shores of lakes may contain high concentrations of microcystin for several months, allowing toxins to dissolve in the water even when the cells are no longer alive or after a recently collapsed bloom.

Species of the filamentous genus Anabaena form slimy summer blooms on the surface of eutrophic lakes and reservoirs. Anabaena blooms may develop quickly. They may look like green paint. In less eutrophic waters, some species also form colonies, which are seen as large dark dots in water samples and on filters after filtration.

Nostoc dominated bloom. Courtesy of J. Hyde, NYS DOH

Planktothrix agardhii (previously named Oscillatoria agardhii) forms long, slender, straight filaments that usually remain separate but form dense surface scums. Its presence may be revealed by a strong earthy odor and the filaments are easily detected visually in a water sample.

Based on the surveys that have been carried out to date in U.S. waters, the most commonly identified cyanotoxins are microcystins, cylindrospermopsins, anatoxins and saxitoxins.

Microcystins

Woronichinia-Microcystis bloom. Courtesy of Keith Loftin, USGS

Microcystins are a group of at least 80 toxin variants which share a cyclic heptapeptide structure and primarily affect the liver (hepatotoxin). Microcystins are the most widespread cyanobacterial toxins and can bioaccumulate in common aquatic vertebrates and invertebrates such as fish, mussels, and zooplankton. Microcystins are produced by Microcystis, Anabaena, Planktothrix (Oscillatoria), Nostoc, Hapalosiphon, Anabaenopsis and Snowella lacustris. Nodularin, which is structurally related to microcystin and has a similar mode of toxicity, has been isolated from only one species of cyanobacteria, Nodularia spumigena. Recent evaluation of carcinogenesis from microcystin exposure by the International Agency for Research in Cancer has determined that microcystin- LR is possibly carcinogenic to humans (Group 2B), and has been linked to incidences of human liver and colon cancer.

Cylindrospermopsins

Aphanizomenon flosaquae dominated bloom. Courtesy of Keith Loftin. USGS

Cylindrospermopsin is usually produced by Cylindrospermopsis raciborski, Aphanizomenon ovalisporum, Anabaena bergii, Umezakia natans, and Raphidiopsis curvata. The primary toxic effect of this toxin is irreversible damage to the liver. It also appears to have a progressive effect on several other vital organs. Effects of poisoning in humans included hepatoenteritis and renal insufficiency. Although the evidence of carcinogenicity in humans and experimental animals is inadequate, there is strong evidence of the tumour-promotion capacity of microcystin-LR to place them in Group 2B as possibly carcinogenic to humans.

Anatoxins
Anatoxins binds to neuronal nicotinic acetylcholine receptors affecting the central nervous system (neurotoxins). There are multiple variants, including anatoxin-a, homoanatoxin-a, and anatoxin-a(s). These toxins are mainly associated with the cyanobacterial genera Oscillatoria species, Cylindrosperum, Planktothrix spp., Aphanizomenon spp., Lyngbya and species such as Anabaena flos–aquae and A. planktonica.

Saxitoxins
Saxitoxins are representative of a large toxin family referred to as the Paralytic Shellfish Poisoning (PSP) toxins. When toxigenic marine dinoflagellates are consumed by shellfish, toxins concentrate and toxic quantities are delivered to consumers of the shellfish. These toxins have been reported also in freshwater cyanobacteria including Aphanizomenon flos–aquae, Anabaena circinalis, Lyngbya wollei, Planktothrix spp. and a Brazilian isolate of C. raciborskii.

LINKS
Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms
US EPA IRIS Toxicological Reviews for Microcystins, Anatoxin-a, and Cylindrospermopsin
WHO Water Related Diseases: Cyanobacterial Toxins
WHO Cyanobacteria and Cyanotoxins in Drinking Water
WHO IARC Monographs on the Evaluation of Carcinogenic Risks to Humans; Ingested Nitrate and Nitrite, and Cyanobacterial Peptide Toxins, VOLUME 94
CDC Harmful Algal Blooms (HABs)
CDC Recent Water-related Response Activities

DETECTION

To determine the occurrence and risk of cyanoHABs, it is important to collect samples that reflect the actual site or source conditions. Samples may consist of water, plankton, invertebrates, vertebrates, or sediments. Although chlorophyll–a and cyanobacterial cells have been used as a first estimation of maximum intracellular microcystin concentration, it is important to isolate a pure culture of the strain and characterize and quantify the toxin to confirm that a particular cyanobacterial strain is the source of the toxin.

There is a diverse range of rapid screen tests and laboratory methods used to detect and identify cyanotoxins in water and cyanobacteria cells (see table below provided by Keith Loftin, USGS). These methods can vary greatly in their degree of sophistication and the information they provide.

Often, more than one toxin may be present in a sample, therefore, a single method will not suffice for the identification and accurate quantification of many cyanotoxins. This laboratory analysis can be expensive and time consuming, and often requires lengthy sample processing to concentrate the toxins and eliminate matrix contaminants. In addition, the ability of these techniques to identify the toxins is restricted by the lack of standard reference materials for the toxins and readily available, validated, analytical methods that are capable of detecting the range of cyanotoxins known to exist.

Analysis of microcystins is most commonly carried out using reversed-phase high performance liquid chromatographic methods (HPLC) combined with ultra-violet (UV) detection. Analytical methods such as enzyme–linked immunosorbent assays (ELISA) already exist to analyze cyanobacterial hepatotoxins and saxitoxins, while the protein phosphatase inhibition assay (PPIA) can be used for microcystins and nodularins. These two methods are sensitive, rapid, and suitable for large-scale screening but are predisposed to false positives and unable to differentiate between toxin variants. The liquid chromatography/mass spectrometry (LC/MS) method can be fast in identifying the toxicants in the samples. Conventional polymerase chain reaction (PCR), quantitative real–time PCR (qPCR) and microarrays/DNA chips can be used to detect microcystin/nodularin and saxitoxin producers. However, relatively little work has been done on methods for detection of other toxins, including anatoxins and cylindrospermopsins. Saxitoxins are the exception, as they also occur widely in the marine environment and many methods have been developed for their detection in shellfish.

The following table describes the methods available for cyanotoxin measurement in freshwater. The information in the table is adapted from a presentation entitled Analytical Methods for Cyanotoxin Detection and Impacts on Data Interpretation by Keith Loftin, Jennifer Graham, Barry Rosen (U.S. Geological Survey) and Ann St. Amand (Phycotech). The presentation was given on April 26, 2010 at the 2010 National Water Quality Monitoring Conference at Denver, CO.

Methods Available for Cyanotoxin Detection

Acronyms in the table:

ELISA: Enzyme-Linked Immunosorbent Assays
PPIA: Protein Phosphatase Inhibition Assays
GC/FID: Gas Chromatography with Flame Ionization Detection
GC/MS: Gas Chromatography with Mass Spectrometry
HPLC or LC/UV: Liquid Chromatography / Ultraviolet-Visible Detection
LC/FL: Liquid Chromatography/Fluorescence

LC/IT MS: Liquid Chromatography Ion Trap Mass Spectrometry
LC/TOF MS: Liquid Chromatography Time-of-Flight Mass Spectrometry
LC/MS: Liquid Chromatography Single Quadrupole Mass Spectrometry
LC/MS/MS: Liquid Chromatography Triple Quadrupole Mass Spectrometry

LINKS
US EPA Environmental Technology Verification Program, Immunoassay Test for Microcystins
Nova Scotia Department of the Environment, Evaluation of Two Test Kits for Measurement of Microcystin Concentrations (PDF) (19 pp, 6MB) 
Presentations EPA Workshop on Cyanobacteria and Cyanotoxins Occurrence and Detection Methods, July 2012 (PDF) (24 pp, 34MB) 
Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms
USGS Guidelines for Design and Sampling for Cyanobacterial Toxin and Taste-and-Odor Studies in Lakes and Reservoirs
Monitoring and Event Response for Harmful Algal Blooms in the Lower Great Lakes (MERHAB-LGL) Analytical Techniques Webpage
WHO Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management
WHO Guidelines for Safe Recreational Waters Volume 1 - Coastal and Fresh Waters
Australia Guidelines for Managing Risks in Recreational Water 
Microcystins ELISA Test Kits Health Canada Algal Toxin Tests Kits Report (PDF) (21 pp, 142K)
Indiana Department of Environmental Management, Blue-Green Algae Sampling Resource List (PDF) (2 pp, 184K)

HEALTH AND ECOLOGICAL EFFECTS

Blooms of cyanobacteria in the United States have been associated with the death of wildlife and domestic animals. They may pose a risk to human health through exposure to contaminated recreational or drinking water, and fish and shellfish consumption.

The most common exposures to cyanobacteria and their toxins are believed to occur during recreational activities via the oral, dermal, and inhalation routes. Oral exposure may occur from accidental or deliberate ingestion of recreational water. Dermal exposure may occur by direct contact of exposed parts of the body to water containing cells, or inhalation may occur through the aspiration of water containing cyanobacteria cells and their toxins. Wind-driven currents may cause buoyant cyanobacterial blooms to amass on shorelines. These accumulations contain orders of magnitude more cyanobacterial cells than blooms in open waters, thus presenting more of a health risk to humans and animals. Cyanobacterial cells can also accumulate in bathing suits, particularly diving suits. When the algal cells break the wearer's skin is exposed to the toxins.

Other major routes of human exposure are through ingestion of cyanotoxin-contaminated drinking water, inhalation while showering, dietary intake via consumption of cyanotoxins in contaminated foods and algal dietary supplements, and exposure from water used in medical treatments (e.g., medical dialysis). The consumption of fish flesh (muscle) is usually considered safe but there are fish species and fish organs, especially the liver, and stomach/intestinal contents which may contain considerable amounts of cyanotoxins. Consumption of mussels and clams collected during cyanobacterial blooms or immediately after blooms should be avoided. Generally, hepatotoxic Microcystins/Nodularins are more common than the neurotoxins in aquatic animals including mussels, clams, crab larvae, prawns, crayfish and zooplankton, causing hepatotoxic effects in the fish and the accumulation of toxins in their organs. Consumption of contaminated shellfish and fish with cyanotoxins can lead to impacts on the liver and the nervous system.

Adverse health outcomes from exposure to cyanotoxins may range from a mild skin rash to serious illness or death. Acute illnesses caused by exposure to cyanotoxins have been reported. Symptoms range from allergic–like reactions (e.g., rhinitis, asthma, eczema, and conjunctivitis) to flu–like reactions (skin rashes, gastroenteritis, and respiratory irritation). Allergic or irritative dermal reactions of varying severity have been reported from recreational exposures to several freshwater cyanobacterial genera such as Anabaena, Aphanizomenon, Nodularia, and Oscillatoria. Endotoxins, the blue–green pigment of the cyanotoxins (phycocyanin) and dermal toxins produced by Lyngbya and Planktothrix species have been linked to skin and eye irritation from exposure during swimming.

The cyanotoxins, like microcystin, anatoxin-a and saxitoxin, have been linked to gastrointestinal illness, liver disease, neurological effects, skin reactions, and cancer in humans. Experimental studies have demonstrated the tumor promotion activity of microcystins and nodularin and the potential for cancer (tumor) development by cylindrospermopsin. The most serious incidence occurred in 1996 at a hemodialysis clinic in Brazil when the deaths of over 50 patients receiving dialysis were attributed to exposure to microcystins which were later identified in the clinic’s water supply.

Cyanobacterial blooms may cause detrimental effects on aquatic ecosystems. High biomass blooms, whether of toxic or nontoxic species, can accumulate as thick scums and mats, which decompose causing excessive oxygen consumption (hypoxia), and lead to mortality and degradation of fish, shellfish, invertebrate, and plant habitats. The blooms may also affect benthic flora and fauna due to decreased light penetration. Toxic blooms from some cyanobacteria genera (e.g., Anabaena circinalis, Aphanizomenon flosaquae, Cylindrospermopsis raciborskii, and Microcystis aeruginosa) may lead to inhibition of other phytoplankton and suppression of zooplankton grazing, leading to reduced growth and reproductive rates and changes in community structure and composition.

In addition to the production of toxins, cyanobacteria have often been associated in drinking water with taste and odor problems. Algal scums can be quickly broken by wave action and redispersed by wind mixing. In shallow bays, scums may take a long time to disperse and cells may disintegrate and die. Dying and lysing cells release their contents (toxins) into the water and are subject to rapid putrefaction of the material. Blooms produce a variety of odor and taste compounds, such as geosmin and 2–methylisoborneol (MIB), which are not toxic but are a nuisance to the public. The cyanobacterial genera that are known to produce geosmin are Anabaena, Aphanizomenon, Lyngbya, Microcystis, Oscillatoria, Phormidium, Schizothrix and Symploca. However, taste and odor issues are complex and are not solely associated with the presence of cyanobacteria. Many actinomycetes bacteria such as Actinomyces and Streptomyces species, aquatic fungi and myxobacteria can also produce these compounds.

LINKS
Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms
US EPA Harmful Algal Blooms and Seafood Safety
US EPA IRIS Toxicological Reviews for Microcystins, Anatoxin-a, and Cylindrospermopsin
WHO Cyanobacterial toxins: Microcystin-LR in Drinking-water
WHO Water Related Diseases: Cyanobacterial Toxins
Health Canada Blue-Green Algae (Cyanobacteria) and their Toxins

RESEARCH

In 1998, Congress passed the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA) to address cyanobacterial HABs that impacted living marine resources, fish and shellfish harvests and recreational and service industries along the U.S. coastal waters. In 2004, Congress reauthorized and expanded HABHRCA by passing the Harmful Algal Bloom and Hypoxia Amendments Act required federal agencies to assess HABs to include freshwater and estuarine environments and develop reports and plans to reduce the likelihood of HAB formation and to mitigate their damage. In 2008, the report entitled Scientific Assessment of Freshwater Harmful Algal Blooms was generated to examine the causes, consequences, and economic costs of freshwater HABs and to establish priorities and guidelines for a research program on HABs in freshwater environments. This document is based, in large part, on the proceedings of the International Symposium on Cyanobacterial Harmful Algal Blooms (ISOC-HAB), a meeting convened by EPA and sponsored by a variety of Federal agencies, to describe current scientific knowledge and identify priorities for future research on cyanobacterial HABs. A detailed account of the research needs related to HABs listed at the Symposium may be found in http://nheerlpub.rtord.epa.gov/nheerl/cyanobacteria_symposium/

Below is a list of recent research activities supported by EPA’s Office of Research and Development:

• Development and Application of a Fiber Optic Array System for Detection and Enumeration of Potentially Toxic Cyanobacteria
• Near-real Time, Highly Sensitive and Selective Field Deployable Biosensor for Cyanotoxins and Cyanobacteria Using both Antibodies and DNA-signatures
• Aptamer Capture and Optical Interferometric Detection of Cyanobacterial Toxins
• Monitoring, Photochemical Fate, and Oxidative Degradation by UV and Solar-based Catalytic Technologies of Cyanotoxins in Freshwater Estuaries
• The Impact of Nutrients, Zooplankton, and Temperature on Growth of, and Toxin Production by, Cyanobacteria Blooms in the Upper Reaches of Chesapeake Bay
• Quantifying Grazing on Harmful Algae with a Novel, qPCR-based Technique Rapid Detection of Algal Toxins
• The Future of Harmful Algal Blooms: An Empirical Approach to Predicting the Combined Impacts of Rising CO2, Temperature, and Eutrophication
• Development and Evaluation of an Innovative System for the Concentration and Quantitative Detection of CCL Pathogens in Drinking Water
• The Geochemistry of a Vitamin: Vitamin B12 Cycling and Marine Microbial Community Dynamics
• Ongoing Projects:
  • Developing a Metabolic Switch for Photobiological Hydrogen Production
  • Development of Novel Risk Assessment and Screening Approaches for Microcystin Congeners in Freshwater Harmful Algae Blooms
  • Cyanobacteria Assessment Network (CyAN)

Research activities and programs from EPA Regional Offices and Laboratories

• Region 1 New England Regional Laboratory: New England Lakes and Pond Projects
• Region 3 Chesapeake Bay Monitoring Program
• Region 4 Gulf of Mexico Program Ecology and Oceanography of Harmful Algal Blooms Projects
• Region 9 Blue Green Algae Watershed Agreement in the Klamath Basin

Research from other Federal Agencies

• NOAA’s Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Research Program
• US Geological Service (USGS) Kansas Algal Toxin Research Team
  • Comparison of two cell lysis procedures for recovery of microcystins in water samples from Silver Lake in Dover, Delaware with microcystin producing cyanobacterial accumulations
  • Ongoing Projects:
    • Evaluation of Laboratory Methods of Cyanobacterial Cell Lysis for Microcystin Recovery and Solid Phase Extraction, US EPA Regional Methods Program
    • Evaluation of Field Techniques for Sample Splitting of Cyanobacterial Bloom Samples
    • Continued Expansion of Direct Injection LC/MS/MS Method For Multiple Classes Of Algal Toxins
    • Screening of Environmental Samples By LC/TOF-MS For Unknown Algal Toxins

CAUSES, PREVENTION AND MITIGATION

Cyanobacteria have been present in aquatic ecosystems for a very long time, with their first occurrence dating back at least 2.7 billion years ago. They are generally present, but not necessarily dominant, in freshwater bodies in the U.S. However, there is widespread agreement within the scientific community that the incidence of cyanobacterial Harmful Algal Blooms (HABs) is increasing both in the U.S. and worldwide. This increase is attributed to increasing anthropogenic activities and their interaction with a suite of physical, chemical and biological factors such as competition and grazing. Some physical factors include the availability of light, meteorological conditions, alteration of water flow, vertical mixing and temperature. Chemical factors include pH changes, nutrient loading (principally in various forms of nitrogen and phosphorus) and trace metals.

As a result of the interplay of these factors, there may be large temporal fluctuations in the levels of cyanobacteria and their toxins in predominating species. The ratio of nitrogen to phosphorus, organic matter availability, temperature, and light attenuation among others, likely play an interactive role in determining corresponding HAB composition and toxin production. Fresh waters that are high in phosphorus but low in nitrogen are typically dominated by toxic nitrogen fixing genera (e.g., Anabaena, Aphanizomenon, Nodularia and Cylindrospermopsis). Such “biological nitrogen fixation” results in the production of ammonia, an important process in the global nitrogen cycle. On the other hand, surface waters that are high in nitrogen are dominated by toxic blooms of non-nitrogen fixing genera (Microcystis, Lyngbya, Planktothrix).

Historically, HABs have been strongly correlated with excessive levels of nutrients in waterbodies with low turbidity. Point sources (which may include discharges from sewage treatment plants and confined animal feeding operations) and non-point sources (which may include diffuse runoff from agricultural fields, roads and stormwater, may be high in nitrogen and phosphorus and can promote or cause excessive fertilization (eutrophication) of both flowing and non-flowing waters.

In addition, climatic changes, including variation in rainfall patterns, flood and drought frequencies, dust storms, tropical storms, and the intensity of hurricanes, have impacted nutrient cycling in freshwater bodies and may support cyanobacterial and algal communities and bloom development. The following conceptual figure illustrates the environmental processes that control cyanobacterial blooms, including man-made management actions and impacts of climate change.

Source: Pearl, H., Hall, N., and Calandrino, E. (2011) Controlling harmful cyanobacterial blooms in a world experiencing anthropogenic and climatic-induced change. Science of the Total Environment, Vol. 409, Issue 10, April, 2011, Pages 1739-1745

Preventative measures are the preferred approach to managing the occurrence of cyanoHABs. The most effective preventative measures are those that seek to control the anthropogenic influences that promote blooms such as the leaching and runoff of excess nutrients. Management practices for nutrients, specifically nitrogen and phosphorus, should have the goal of reducing loadings from both point and nonpoint sources, including water treatment discharges, agricultural runoff, and stormwater runoff. Devices that result in the mixing of lakes (for example, by air bubbling), enhance vertical mixing of the phytoplankton, which minimizes the formation of surface blooms of buoyant cyanobacteria. Also, increasing the water flow through lakes or estuaries reduces water residence time and inhibits cyanobacteria blooms. However, these efforts can be expensive and are best suited to small affected water bodies.

Another effective but expensive management practice for small watersheds is the application of compounds to chemically-precipitate phosphorus, followed by removal of the sediment by dredging. Adding alum, ferric salts or clay products effectively settles the phosphorus to the sediment layer reducing concentrations and the potential for bloom formation. Suction dredging of the top half meter of sediments removes nutrients and prevents bloom formation. Repeated dredging at intervals of several years may be necessary to prevent the re-release of phosphorus. Monitoring phosphorus concentrations is recommended to evaluate if dredging is needed. Effective treatment requires careful design and understanding of the sediment chemistry and hydrology of the water to be treated.

Mitigation (or remedial) measures can be employed once blooms have already occurred to control the phytoplankton blooming rate and to remove blooms. Remedial measures include the physical removal of surface scums and the application of algaecides and other chemicals (e.g. copper sulfate and lime) to control blooms. The precipitation of algal blooms with lime does not appear to cause cell lysis and toxin release into the water. However, application rates are high and, therefore, are recommended only for small lakes. Treatment of algal blooms with copper sulfate leads to cell breaking and a substantial release of cyanotoxins into the water, greatly increasing the risk of toxin contamination and treatment costs. Copper may also be toxic to other aquatic wildlife in the lake. Algaecides also lead to cell breaking and should be applied when cell numbers are low to avoid excessive toxin contamination following rupture of the cells. Algaecides application in drinking water reservoirs may required monitoring since conventional drinking water treatment processes are not very effective in removing toxins released in water after cell breaking.

Biological mitigation measures include different approaches to change the aquatic food web to increase grazing pressure on cyanobacteria by introduction of functionally competitive species (e.g., diatoms). Competition and grazing can affect the net growth rates of algae in water but the effectiveness in reducing harmful algae depends on the population density of the harmful algae and nutrients concentrations. In some cases, grazing may increase nutrient regeneration affecting the availability of some nutrient forms for the algae to consume. For many HAB species, the toxicity increases when they are grown under nutrient-unbalanced conditions. Although competition and grazing have been studied for a long time, there are still important gaps, in particular, understanding the grazing of phytoplankton with different nutritional status.

Cyanobacterial problems and cyanotoxins in water supplies may also be mitigated during drinking water treatment. Conventional water treatment (flocculation, coagulation, sedimentation and filtration) is effective in removing algal cells and intracellular cyanotoxins. Drinking water treatment facilities that use microstrainers or fine screens to remove debris from the water intake are useful in removing larger algae, cyanobacterial cells and aggregated cells. Oxidants are often added at the intake to reduce taste and odor problems and to discourage biological growth (zebra mussels, biofilm, and algae) on the intake pipe. However, pretreatment oxidation is not recommended because it may rupture cyanobacteria cells releasing the cyanotoxin to the water column. This may also cause the formation of chlorinated disinfection by-products.

When algae are blooming, a substantial proportion of toxins are expected to be released to the water column. Conventional water treatment is usually not effective in removing extracellular cyanotoxins (soluble toxins). Neither aeration nor air stripping are effective treatments for removing soluble toxins or cyanobacterial cells. Advanced treatment processes, such as powdered and granular activated carbon adsorption, must be implemented to remove extracellular toxins as well as intact cells.

Different cyanotoxins react differently to chlorination. While chlorination is an effective treatment for destroying microcystins and cylindrospermopsin, effectiveness is dependent on the pH. Anatoxin–a is not degraded by chlorination. Other chlorine disinfectants such as chloramines and chlorine dioxide that are frequently used to minimize the formation of regulated disinfection by-products, have little impact on microcystin, cylindrospermopsin, anatoxin-a, and saxitoxins. Therefore, those treatment utilities that use disinfectants other than chlorine in order to reduce the formation of disinfection by-products may not have an oxidant treatment barrier for cyanotoxin inactivation.

Other disinfection techniques like ozone and Ultraviolet (UV) light have been shown to be effective in inactivating cyanotoxins. Ozone is a good oxidant of microcystins, anatoxin-a and cylindrospermopsin. Saxitoxins, however, appear to have low to moderate susceptibility to ozone oxidation. Ultraviolet (UV) is an effective treatment in destroying microcystin, anatoxin-a, and cylindrospermopsin cells. However, it requires high dosages, making it a non-viable treatment barrier for cyanotoxins.

In summary, mitigation and treatment techniques that are applied once a bloom has formed can be important management tools, but preventing the bloom from forming is the better choice when it can be achieved. A wide range of technologies are available for treatment of drinking water sources contaminated with cyanotoxins. However, all the technologies have their own advantages and limitations. Choosing the most efficient, safest, and cost-effective approach should be done on case-by-case basis.

LINKS
Climate Change and Harmful Algal Blooms Fact Sheet
Harmful Algal Blooms (HAB) – The Beach Manager's Manual (PDF) (8 pp, 3.4MB, About PDF)
Cyanobacteria and Cyanotoxins: Information for Drinking Water Systems fact sheet (PDF) (9 pp, 78K, About PDF) 
Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms
US EPA Climate Change Indicators in the United States
US EPA Watershed Framework Approach
US EPA Watershed Analysis and Management (WAM) Guide for States and Communities
WHO Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management
WHO Guidelines for Safe Recreational Waters Volume 1 - Coastal and Fresh Waters
Australia Guidelines for Managing Risks in Recreational Water
Management Strategies for Cyanobacteria (Blue-Green Algae) and their Toxins: a Guide for Water Utilities
US EPA OW Nutrient Pollution Video

POLICIES AND GUIDELINES

Currently there are no U.S. federal guidelines, water quality criteria and standards, or regulations concerning the management of harmful algal blooms in drinking water under the Safe Drinking Water Act (SDWA) or in ambient waters under the Clean Water Act (CWA). However, several countries outside the U.S. do have various values that serve as guidelines or thresholds for certain management actions.

The SDWA requires EPA to publish a list of unregulated contaminants that are known or expected to occur in public water systems in the U.S., with a frequency and at levels of public health concern and where there is a meaningful opportunity for health risk reduction. This list is known as the Contaminant Candidate List (CCL). EPA’s Office of Water has listed cyanobacteria and cyanotoxins on the three drinking water CCLs (CCL 1 of 1998, CCL 2 of 2005 and CCL 3 of 2009). Based on toxicological, epidemiology and occurrence studies, the EPA Office of Ground Water and Drinking Water has focused on 3 of the over 80 variants of cyanotoxins reported, recommending Microcystin congeners LR, YR, RR and LA, Anatoxin–a and Cylindrospermopsin for further research activities. The EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) program to collect data for contaminants suspected to be present in drinking water that do not have health–based standards.

The absence of standardized analytical methods for individual toxins has prevented EPA from including cyanobacterial toxins in the UCMR. Due to this factor and to the absence of certified toxin standards to support analyses and the lack of capacity to deal with multiple toxin congeners, EPA has not made regulatory determinations or established any guidelines for cyanobacteria and their toxins in drinking water.

The World Health Organization (WHO) released in 1998 a provisional guideline of 1 μg/L for microcystin-LR in drinking-water. This guideline value covers only microcystin-LR since there are insufficient data to derive a guideline value for cyanobacterial toxins other than microcystin-LR. For recreational waters, the WHO considered a single guideline value for cyanobacteria or cyanotoxins to be not appropriate. Due to the variety of exposures in recreational activities (contact, ingestion and inhalation) it is necessary to differentiate between the chiefly irritative symptoms caused by unknown cyanobacterial substances and the more severe hazard of exposure to high concentrations of known cyanotoxins, particularly microcystins. The WHO guidance values for the relative probability of acute health effects during recreational exposure to cyanobacteria and microcystins are:

Several U.S. states have implemented standards or guidelines that apply to cyanotoxins and cyanobacteria in recreational water using risk assessment methods and the guidelines provided by the WHO for recreational waters. For a summary of the U.S. states with guidance values being used to post advisories and beach closures see the table below or see the Monitoring Recreational Freshwaters paper by Jennifer L. Graham, Keith A. Loftin, and Neil Kamman (2009).

LINKS
Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms
US EPA Contaminant Candidate List (CCL) and Regulatory Determinations
US EPA Creating a Cyanotoxin Target List for the UCMR (PDF) (17 pp, 110K, About PDF) 
WHO Cyanobacterial toxins: Microcystin-LR in Drinking-water
WHO Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management
Current approaches to cyanotoxin risk assessment, risk management and regulations in different countries
WHO Guidelines for Safe Recreational Waters Volume 1 - Coastal and Fresh Waters
Health Canada Guidance for cyanobacterial Toxins – Microcystin-LR in Drinking Water
Health Canada Guidelines for Canadian Recreational Water Quality
Summary of the U.S. states with guidance values for cyanotoxins in drinking and recreational water 

Links to State Information

• California Department of Public Health, Blue-Green Algae (Cyanobacteria) Blooms
• Florida Department of Health, Division of Environmental Health, Aquatic Toxins Program
• Georgia Department of Public Health, Coastal Health District, Harmful Algal Bloom
• Indiana Department of Environmental Management, Addressing concerns about blue-green algae
• Iowa Department of Public Health, Harmful Algal Blooms
• Kansas Department of Health and Environment, Blue Green Algae
• Maine Department of Environmental Protection, Algal Toxins
• Maryland Department of Natural Resources, Harmful Algal Blooms in Maryland
• Massachusetts Department of Public Health, Environmental Toxicology Program, Algae
• Minnesota Department of Health Blue-Green Algal Blooms and Microcystin
• Minnesota Pollution Control Agency, Blue-green Algae and Harmful Algal Blooms
• New England Interstate Water Pollution Control Commission, Regional Cyanobacteria Workshop
• New Hampshire Department of Environmental Services: What You Should Know About Cyanobacteria
• New York State, Department of Environmental Conservation, Blue-Green Harmful Algal Blooms
• North Carolina Department of Health and Human Services, Blue-Green Algae
• Ohio Department of Health, Department of Natural Resources
• Ohio EPA: Grand Lake St. Marys Toxic Algae Information
• Oregon Health Authority, Harmful Algal Bloom Surveillance Program
• Oregon Health Authority, Algae Resources
• Rhode Island Department of Health, Cyanobacteria
• South Carolina Department of Natural Resources, South Carolina Algal Ecology Lab
• Texas Parks and Wildlife Department, Harmful Algal Blooms
• Vermont Department of Health, Cyanobacteria, Blue-Green Algae in Lake Champlain
• Vermont Department of Environmental Conservation, Water Quality Division, Cyanobacteria toxins
• Virginia Department of Health, Cyanobacteria
• Washington State Department of Health, Division of Environmental Health, Cyanobacteria (Blue-Green Algae)
• Washington State Toxic Algae, Freshwater Algae Bloom Monitoring Program
• Wisconsin Department of Health Services, Blue-Green Algae

• Inland HAB Discussion Group

More Information

• The Interagency, International Symposium on Cyanobacterial Harmful Algal Blooms (ISOC-HAB) held on 2005 and co-sponsored by the EPA, NOAA, FDA, USGS, NIH, CDC, USDA, and other federal agencies described the scientific knowledge and areas of uncertainty concerning freshwater harmful algal blooms. The proceedings of the symposium were published in a monograph that could be download here:
• Climate Change Indicators in the United States report presents the trends of 24 indicators, including, global sea surface temperature, related to the causes and effects of climate change.
• EPA's National Water Program Watershed Framework Approach is a coordinating framework for environmental management that focuses public and private sector efforts to address the highest priority problems within hydrologically-defined geographic areas, taking into consideration both ground and surface water flow.
• Watershed Analysis and Management (WAM) Guide for States and Communities is a guideline that outlines the methods, tools and process to ensure an effective watershed partnership
• The Environmental Technology Verification Program, Advanced Monitoring Systems Center Immunoassay Test Kits for detection and quantification of Microcystins in water
• Harmful Algal Blooms and Seafood Safety
• Toxicological Reviews of Anatoxin-a, Cylindrospermopsin, and Microcystins with available data regarding toxicity of these toxins in support of the health assessment of unregulated contaminants on the CCL.
• National Lakes Assessment: A Collaborative Survey of the Nation’s Lakes. This report states the lakes conditions in the United States for 2010
• EPA Region 1 New England Lakes and Pond Projects. Provide an assessment of the ecological and water quality condition of lakes and ponds across the New England region
• EPA Region 3 Chesapeake Bay Program information on HABs and waterways monitoring.
• Office of Research and Development, National Center for Environmental Assessment, Environmental Monitoring for Public Access and Community Tracking Program. Automated biological monitoring system that measured toxicity caused by HABs in the Chicamacomico River, a tributary of Chesapeake Bay.
• EPA Region 4 Gulf of Mexico Program Information on HABs and useful links and resources
• EPA Region 9 National Watershed Program. Blue Green Algae Monitoring in the Klamath River and reservoirs.
• Office of Water, Office of Ground Water and Drinking Water, Contaminant Candidate List (CCL) and Regulatory Determinations. Information about EPA’s list of contaminants in public water systems that are not regulated but may require regulation under the Safe Drinking Water Act.
• Office of Water, Office of Ground Water and Drinking Water, Unregulated Contaminant Monitoring Regulation (UCMR 2). Creating a Cyanotoxin Target List for the UCMR

• This site provides information on cyanobacteria and HABs, CDC’s related activities and other HABs resources

• This site provides information on NOAA’s activities related to HABs, Research and Monitoring activities and more
• This site provide a description of the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA)
• This site describes the purpose and projects of the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Research Program

• This site provides information on algal toxins from the Kansas Algal Toxin Research Team
• This site list the research efforts on water quality and cyanobacteria from USGS Microbiology
• USGS Cooperative Water Program
• Guidelines for Design and Sampling for Cyanobacterial Toxin and Taste-and-Odor Studies in Lakes and Reservoirs

• Cyanobacterial (Blue-Green Algal) Toxins: A Resource Guide. Resource document for water utilities.
• Assessment of Blue-Green Algal Toxins in Raw and Finished Drinking Water. Evaluates the occurrence of algal toxins in the US water sources and provides guidance for monitoring algal toxins and recommendations for responding to potential safety concerns.
• Removal of Algal Toxins from Drinking Water Using Ozone and GAC. Assesses the conditions of ozone residual and contact time under which three algal toxins (Microcystin, Anatoxin-a, and the PSP class of toxins) are destroyed.
• Treating Algal Toxins Using Oxidation, Adsorption, and Membrane Technologies. Develops chemical and engineering data and criteria necessary to assess algal toxin treatment for a variety of raw water qualities and locations.
• Evaluation of Integrated Membranes for Taste and Odor and Algal Toxin Control. Will evaluate ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes, in integrated treatment systems, for the removal of taste and odor compounds and cyanobacterial toxins.
• Rapid Detection of Cyanobacterial By-Products in Drinking Water. A rapid and simple method for detection and differentiation of MC-LR and its variants.
• Determination and Significance of Emerging Algal Toxins (Cyanotoxins). Analyzes and compares analytical techniques used to assess the occurrence of total (intracellular and dissolved) and dissolved biotoxins in water supplies and treated waters
• Development of Molecular Reporters for Microcystis Activity and Toxicity. Novel molecular approaches for the detection of Microcystis aeruginosa and the Microcystin toxin.
• Early Detection of Cyanobacterial Toxins Using Genetic Methods. Provides water utilities with robust and functional molecular detection tools for managing the risk from cyanobacterial toxins.
• Methods for Measuring Toxins in Finished Water. Commonly used toxicity assays and disinfectant neutralization methods/techniques of chlorine and chloramines to allow for reliable measurements of toxins in finished water.
• Criteria for Quality Control Protocols for Various Algal Toxin Methods. Quality control criteria to be used by laboratories providing algal toxin analyses to drinking water utilities.
• Reservoir Management Strategies for the Control and Degradation of Algal Toxins. Identifies the mechanisms that trigger the production and release of algal and cyanobacterial biotoxins into water supplies in response to environmental and reservoir treatment conditions.
• International Guidance Manual for the Management of Toxic Cyanobacteria. Consolidates more than 20 years of research on the management of cyanobacteria and the toxins they produce.
• Optimizing Conventional Treatment for Removal of Cyanobacteria and Toxins. Identify the optimum coagulation, flocculation, sedimentation, and filtration conditions for the removal of cyanobacteria and their metabolites.

• Toxic cyanobacteria in water: A guide to their public health consequences, monitoring and management. This guide provide information needed to protect drinking water and recreational water sources from the health hazards caused by cyanobacteria and their toxins
• Cyanobacteria and Cyanotoxins in Drinking Water. This site provides resources regarding cyanobacteria and their toxins in drinking water and recreational waters.
• Guidelines for Safe Recreational Waters Volume 1 - Coastal and Fresh Waters. This document provides information on the health hazards and risks associated with the recreational use of coastal and freshwater environments. Algae and cyanobacteria in coastal and estuarine waters and in fresh water are discussed in Chapter 7 and Chapter 8, respectively.
• Cyanobacterial toxins: Microcystin-LR in Drinking-water. Background document for development of WHO Guidelines for Drinking-water Quality. This document provides supporting information to the Guidelines for Drinking Water Quality and describes the approaches used in deriving guideline values and evaluates the risks for human health from exposure to Microcystin-LR in drinking water.
• Water Related Diseases: Cyanobacterial Toxins. This link provides a summary of health effects, the causes and control activities for cyanobacterial toxins.

Australia

• Guidelines for Managing Risks in Recreational Water. Guidelines prepared by the Australian Government National Health and Medical Research Council to protect human health from threats posed by the recreational use of coastal, estuarine and fresh waters, such as natural and artificial hazards.
• Management Strategies for Cyanobacteria (Blue-Green Algae) and their Toxins: a Guide for Water Utilities. Guide developed by the Water Quality Research Australia to provide management strategies of source water.
• Australian Drinking Water Guidelines (PDF) (1244 pp, 6.3MB, About PDF)

• Blue-Green Algae (Cyanobacteria) and their Toxins. This site covers topics related to cyanobacteria in drinking water and recreational water.
• Guidelines for Canadian Drinking Water Quality: Cyanobacterial Toxins – Microcystin-LR. This document establishes the maximum acceptable concentration (MAC) for the cyanobacterial toxin Microcystin-LR in drinking water.
• Guidelines for Canadian Recreational Water Quality. This document establishes the recommended guideline values for cyanobacteria and their toxins in recreational waters.

• Provide links and resources on HABs in coastal waters.

Intergovernmental Oceanographic Commission of UNESCO, Harmful Algal Bloom Programme

• IOC Harmful Algal Bloom Website.

For additional information, please contact Lesley Vazquez-Coriano (Vazquez-Coriano.Lesley@epa.gov), Project Manager, at 202-566-1125.