Algal Toxins in Drinking Water: EPA Health Advisories

Updated August 18, 2015

Algal Toxins in Drinking Water: EPA Health Advisories

On June 17, 2015, the Environmental Protection Agency

(EPA) issued drinking water health advisories for two algal

toxins to help water providers address threats to drinking

water supplies from harmful algal blooms (HABs).

Blue-green algae (cyanobacteria) occur naturally in marine

and fresh water and can produce numerous potent algal

toxins (cyanotoxins). Exposure to cyanotoxins can cause a

range of adverse health effects, from rashes to severe illness

and, rarely, death. A confluence of conditions—including

warm water temperatures, excess nutrients (mainly nitrogen

and phosphorus) and strong sunlight—can trigger explosive

growth of cyanobacteria, creating harmful algal blooms.

These HABs can contaminate drinking water supplied from

surface water or groundwater directly influenced by surface

water. Further, HABs appear to be increasing. EPA’s 2009

National Lakes Assessment found microcystins, one of the

more common and potentially harmful cyanotoxins, to be

present in one-third of lakes surveyed nationwide.

In August 2014, microcystins produced by a bloom in Lake

Erie contaminated a water system serving Toledo, Ohio,

and surrounding areas for several days. No federal drinking

water standards were available for managing this or other

cyanotoxins, nor were rapid and sufficiently specific

analytical methods available to meet the needs of water

providers faced with quickly identifying, measuring, and

removing the toxins to ensure the safety of water supplies.

As a trigger for taking action, water managers used the state

guideline of 1 microgram per liter (µg/L) for microcystinLR (one of the more common and harmful variants of

microcystin). The immediate problem was resolved;

however, this and other incidents added urgency to EPA’s

efforts to assess cyanotoxin risks to public water supplies.

EPA has been conducting research on several common

cyanotoxins—microcystins, cylindrospermopsin, and

anatoxin-a—and evaluating them for possible regulation

under the Safe Drinking Water Act (SDWA). The agency

has also worked to validate analytical methods to enable the

measurement of these cyanotoxins in water at lower

concentrations and with greater accuracy and precision.

However, technical challenges and information gaps on the

toxins’ health effects and occurrence have thus far

prevented EPA from determining whether the cyanotoxins

meet the criteria for regulation under the SDWA.

In light of the impacts of the Lake Erie HAB and the

increasing frequency of HABs nationwide, EPA set a goal

to issue health advisories for the three types of cyanotoxins

ahead of the 2015 summertime algal bloom season.

Drinking Water Health Advisories

The SDWA authorizes EPA to issue health advisories for

contaminants that are not regulated under the act (42 U.S.C.

§300g-1(b)(1)(F)). Health advisories include nonenforceable guideline values for contaminants in drinking

water (based on non-cancer health effects) and often

include values for different exposure durations: one day, 10

days, several years, and lifetime. Advisories also provide

technical guidance on identifying, measuring, and treating

contaminants in drinking water.

On June 17, 2015, EPA issued several resource documents

related to HABs, including drinking water health advisories

for microcystins and cylindrospermopsin (80 Federal

Register 34637). Because of insufficient health effects data,

EPA was unable to issue an advisory for anatoxin-a.

The advisories include levels for the cyanotoxins in

drinking water at or below which adverse health effects are

not expected to occur based on short-term (10-day)

exposures (Table 1). They also include information on

analytical methods that water providers can use to test for

the presence and concentrations of the toxins and treatment

techniques to remove them from drinking water.

EPA also issued Recommendations for Public Water

Systems to Manage Cyanotoxins in Drinking Water, a

technical document to help water providers develop

cyanotoxin management strategies (e.g., determining when

and how to monitor and treat water and when and how to

notify the public and officials at different toxin levels).

Table 1. Cyanotoxin Health Advisory Levels

10-day exposures, micrograms per liter (µg/L)

Microcystins

Cylindrospermopsin

Children less

than 6 years old

0.3

0.7

Ages 6 and older

1.6

3.0

Source: EPA, 2015 Drinking Water Health Advisories for Two

Cyanobacterial Toxins, Fact Sheet, http://water.epa.gov/drink/

standards/hascience.cfm#micro.

Notes: EPA recommends utilities issue “do not drink, do not boil”

notices when toxins exceed values for ages 6 and older. Targeted

notification for sensitive groups is suggested when toxin levels exceed

the lower value but not the higher value. EPA worked with Health

Canada to develop health advisories. The World Health Organization

(WHO) issued a provisional drinking water guideline for microcystinLR of 1 µg/L in 1998. Ohio and Oregon use this same guideline level.

Minnesota set a guidance level of 0.04 µg/L. Seventeen countries have

adopted microcystin-LR guidelines ranging from 1.0 µg/L to 1.5 µg/L.

While broadly supporting EPA efforts, the American Water

Works Association has noted technical, policy, and cost

issues with the recommendations document and has asked

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Algal Toxins in Drinking Water: EPA Health Advisories

EPA to classify the document as “economically significant”

and to reissue it after allowing public review and comment.

One issue concerns the feasibility of using two advisory

levels for each toxin, each with different risk management

recommendations. Another of the issues concerns the

effectiveness of certain recommended testing methods

(http://www.awwa.org/legislation-regulation.aspx).

Federal Drinking Water Standards

The SDWA authorizes EPA to regulate and set enforceable

standards for drinking water contaminants and lays out a

process for doing so. First, EPA is required to regularly

prepare contaminant candidate lists (CCLs) that identify

contaminants that may require regulation. In 1998, EPA

included cyanobacteria and their toxins as candidates for

regulation on the first list (CCL 1). EPA’s 2009 list (CCL

3) and draft CCL 4 include the cyanotoxins microcystinLR, anatoxin-a, and cylindrospermopsin.

EPA then must make regulatory determinations for at least

five listed contaminants every five years. To make a

determination to regulate, the Administrator must find that

(1) the contaminant may have adverse health effects, (2) it

occurs (or is likely to occur) in public water supplies at

levels and frequencies of concern, and (3) its regulation

presents a meaningful opportunity to reduce health risks.

EPA reports that current scientific understanding of the risk

of exposures to low levels of cyanotoxins is too uncertain to

support setting standards. Further, information on the

frequency and levels of occurrence of the cyanotoxins in

public water supplies is limited. To gather occurrence data,

the SDWA directs EPA to administer a monitoring program

for unregulated contaminants. EPA plans to issue its fourth

Unregulated Contaminant Monitoring Rule (UCMR 4) in

2017 to require public water systems to monitor for 30

unregulated contaminants for the period 2017-2021. The

UMCR 4 is expected to include the three cyanotoxins.

The complexity of cyanobacteria and their toxins impedes

regulatory control. EPA reports that a single cyanobacteria

species can produce multiple toxins or no toxins, while

different species can produce the same toxins. Further, a

single toxin can have numerous “sub-species.” (Researchers

have identified more than 80 variants of microcystins.)

Cyanotoxins can occur outside or inside cells; in the latter

case, if the cell walls break, more toxins are released. This

complexity also poses testing and treatment challenges.

Although effective treatment options are available, water

providers must be able to identify toxins accurately to select

appropriate treatment method(s), because the wrong

treatment can cause some bacteria to release more toxins.

Congressional Actions

The 114th Congress has acted to address cyanotoxins in

drinking water. H.R. 212 and S. 460 (the Drinking Water

Protection Act) were introduced to require EPA to submit

to Congress a detailed plan to assess and manage risks of

algal toxins in public water supplies. In February 2015, the

Environment and the Economy Subcommittee of the House

Energy and Commerce Committee held a hearing on

microcystins in drinking water; the full committee reported

H.R. 212, amended, and the House passed H.R. 212. The

Senate passed H.R. 212 on August 5, 2015, without

amendment, and the President signed the bill into law on

August 7 (P.L. 114-45). The law requires EPA to include in

the strategic plan steps and schedules for EPA to assess

health risks of algal toxins in drinking water, publish a list

of toxins likely to pose risks and summarize their health

effects, determine whether to issue health advisories,

publish guidance on feasible methods to identify and

measure the algal toxins in water, recommend feasible

treatment methods, etc. Further, P.L. 114-45 requires the

Government Accountability Office to report on federal

HAB-related expenditures for FY2010 through FY2014.

Related bills, the Safe and Secure Drinking Water Act of

2015 (H.R. 243 and S. 462), were introduced to direct EPA

to publish a microcystins health advisory within 90 days of

enactment. These bills would also require EPA to report

annually to Congress—until EPA made a regulatory

determination for microcystins—on the status of the

determination and efforts promote testing and treatment.

HABs Prevention

Water providers and others have urged actions to reduce the

formation of HABs so that communities are not faced with

the resulting health risks and costs. Beyond drinking water

impacts, HABs can harm pets, wildlife, and livestock;

contaminate fish; halt recreational activities; and cause

other economic losses. Nutrients play a key role in the

development of HABs, and major nutrient sources include

agricultural runoff, discharges from sewage treatment

plants, and storm-water runoff from lawns and streets.

Reducing nutrient loading of waterways would help reduce

HABs. Strategies include changing fertilizer and manure

management practices, increasing sewage treatment to

remove phosphorus, controlling storm-water runoff, and

setting limits on point-source discharges to surface waters.

Among other federal actions, the U.S. Department of

Agriculture has targeted funds for conservation activities to

improve conditions in Lake Erie. (See CRS Report R43919,

Nutrients in Agricultural Production: A Water Quality

Overview.) Funding has also been provided through the

Great Lakes Restoration Initiative. Similarly, Clean Water

Act (CWA), Section 319, authorizes EPA to provide state

grants to help address nonpoint pollution sources (e.g.,

runoff from farmland and streets). Further, under CWA

Section 304, EPA is developing water quality criteria for

these toxins for recreational waters. States could use the

criteria to develop water quality standards and set discharge

limits in permits for pollutants that contribute to HABs.

Mary Tiemann, Specialist in Environmental Policy

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Algal Toxins in Drinking Water: EPA Health Advisories

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