SEPA
United States
Environmental Protection
Agency
Office of Water
820F15003
June 2015
2015 Drinking Water Health Advisories for
Two Cyanobacterial Toxins
Summary
EPA has issued 10-Day Drinking Water Health
Advisories (HAs) for the cyanobacterial toxins
microcystins and cylindrospermopsin.
EPA recommends HA levels at or below 0.3
micrograms per liter for microcystins and 0.7
micrograms per liter for cylindrospermopsin in
drinking water for children pre-school age and
younger (less than six years old). For school-age
children through adults, the recommended HA levels
for drinking water are at or below 1.6 micrograms
per liter for microcystins and 3.0 micrograms per
liter for cylindrospermopsin. Young children are
more susceptible than older children and adults as
they consume more water relative to their body
weight.
HAs are non-regulatory values that serve as informal
technical guidance to assist federal, state and local
officials, and managers of public or community
water systems to protect public health from
contaminants. EPA has also published health effects
support documents for the cyanobacterial toxins
microcystins and cylindrospermopsin. These
documents contain the health effects basis for the
development of HAs for the protection of human
health. In addition, EPA has published a health
effects support document for anatoxin-a but
concluded that there was not adequate information
to support a health advisory for this toxin.
Background
What are cyanobacterial toxins?
Cyanobacteria, common to freshwater and marine
ecosystems, can under certain conditions (high
nutrient concentrations and high light intensity)
form scums or "blooms" at the surface of a water
body. These blooms can produce toxic compounds
(cyanobacterial toxins or "cyanotoxins") that are
harmful to the environment, animals and human
health. Winds and water currents can transport
cyanobacterial blooms within proximity to drinking
water intakes at treatment plants that, if not
removed during treatment, can cause odor, taste
and color problems in treated drinking water and
can be harmful to human health.
What is a health advisory?
The Safe Drinking Water Act provides the authority
for EPA to publish health advisories for contaminants
not subject to any national primary drinking water
regulation. Health advisories describe non-
regulatory concentrations of drinking water
contaminants at or below which adverse health
effects are not anticipated to occur over specific
exposure durations (e.g., one-day, 10-days, several
years, and a lifetime). They serve as informal
technical guidance to assist federal, state and local
officials, and managers of public or community
water systems by providing information on the
health effects of and methods to sample and treat
cyanobacterial toxins in drinking water. HAs are not
legally enforceable federal standards and are subject
to change as new information becomes available.
Why has EPA taken this action?
There are no U.S. federal guidelines, water quality
criteria, standards or regulations for cyanobacteria
or cyanotoxins in drinking water under the Safe
Drinking Water Act or in surface waters under the
Clean Water Act. However, EPA has listed
cyanotoxins including microcystin-LR,
cylindrospermopsin, and anatoxin-a on the previous
and current Contaminant Candidate Lists (CCL),
which identify contaminants that may need
regulation under the Safe Drinking Water Act.
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EPA found there are adequate health effects data to
develop HAs for microcystins and
cylindrospermopsin, but found the data inadequate
to develop an HA for the cyanobacterial toxin
anatoxin-a.
How Can I Be Exposed to Cyanobacterial Toxins?
For the cyanotoxin HAs, drinking water is the
primary source of exposure. Exposure may also
occur by ingestion of toxin contaminated food,
including consumption offish; by inhalation and
dermal contact during bathing or showering; and
during recreational activities. Effects due to these
other routes of exposure cannot be quantified at this
time, however, they are assumed to be less than
from drinking water ingestion.
What information was used to develop the
health advisories for cyanobacterial toxins?
EPA worked with Health Canada and conducted a
comprehensive search of the literature from January
2013 to May 2014. The HA includes information on
occurrence; environmental fate; mechanisms of
toxicity; acute, short term, subchronic and chronic
toxicity and cancer in humans and animals;
toxicokinetics; health effects and exposure. The HA
also includes information on methods for analysis
and treatment techniques for removal in drinking
water treatment plants.
Health Effects Information
Effects including gastroenteritis, and liver and kidney
damage have been reported in humans following
short-term exposure to cyanotoxins in drinking
water. Recreational exposure to cyanobacterial
blooms has been reported to lead to allergic
reactions, including hay fever-like symptoms; skin
rashes; and gastrointestinal distress. Animal studies
have shown that long-term adverse effects from
cyanotoxins include liver and kidney damage.
However, more research is needed to quantify these
effects.
Critical Studies Used
The critical study supporting the microcystins 10-day
HA was conducted by Heinze (1999). This study is a
28-day study in rats, whose drinking water contained
microcystin-LR. Effects observed included changes in
liver weight, liver serum enzymes, and lesions in the
liver. The lowest observed adverse effect level
(LOAEL) based on these effects was 50 micrograms
per kilogram per day, a no observed adverse effect
level (NOAEL) was not identified. This dose was
selected as the basis for deriving a reference dose
(RfD) for microcystins. A total uncertainty factor of
1000 (10 to account for differences between humans
and animals, 10 to account for variability in humans,
3 for extrapolation from a LOAEL, and 3 to address
database deficiencies) was applied to determine the
RfD for microcystins. These values were used along
with body weight and drinking water intake for
infants and adults to derive the 10-Day HA values.
The 10-day HA of 0.3 u.g/L is considered protective of
non-carcinogenic adverse health effects for bottle-
fed infants and young children of pre-school age
over a ten-day exposure to microcystins in drinking
water. The 10-day HA of 1.6 u.g/L is considered
protective of non-carcinogenic adverse health
effects for children of school age through adults over
a 10-day exposure to microcystins in drinking water.
The critical study supporting the cylindrospermopsin
10-day advisory was conducted by Humpage and
Falconer (2002, 2003). This study is an 11-week
study with cylindrospermopsin administered to male
mice by gavage. Effects observed included increases
in kidney weight. The NOAEL from this study was 30
micrograms per kilogram per day and the LOAEL
based on kidney weight changes was 60 micrograms
per kilogram per day. The NOAEL of 30 micrograms
per kilogram per day was selected as the basis for
the RfD. A total uncertainty factor of 300 (10 to
account for differences between humans and
animals, 10 to account for variability in humans, and
3 to address database deficiencies) was applied to
determine the RfD for cylindrospermopsin. These
values were used along with body weight and
drinking water intake for infants and adults to derive
the 10-Day HA values. The 10-day HA of 0.7 u.g/L is
considered protective of non-carcinogenic adverse
health effects for bottle-fed infants and young
children of pre-school age over a 10-day exposure to
cylindrospermopsin in drinking water. The 10-day HA
of 3 u.g/L is considered protective of non-
carcinogenic adverse health effects for children of
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school age through adults over a 10-day exposure to
cylindrospermopsin in drinking water.
As the science on the health impacts of algal toxins
continues to improve, EPA will track developments
and update recommendations as appropriate.
Additional EPA support document to assist
states and utilities in managing
cyanobacterial toxins
EPA has also published a cyanotoxin management
document as a companion to the HAs. The
document is designed to provide information and a
framework that Public Water Systems and others
can consider to inform their decisions on managing
the risks from cyanotoxins to drinking water. It
includes a potential stepwise approach these
systems could use to inform their decisions on
whether and how to monitor and treat water, and
communicate with stakeholders.
Where can I find more information?
To learn more about the HAs for microcystins and
cylindrospermopsin and to view the health effects
support documents for these and anatoxin-a in
drinking water, visit EPA's Health Advisory webpage:
http://water.epa.gov/drink/standards/hascience.cf
rn. To learn about additional strategies Public Water
Systems and others could consider in managing
cyanotoxins, visit EPA's CyanoHABs website:
http://www2.epa.gov/nutrient-policy-
data/guidelines-and-recommendations
References
Heinze, R. 1999. Toxicity of the cyanobacterial toxin
microcystin-LR to rats after 28 days intake with the
drinking water. Environ. Toxicol. 14(1):57-60.
Humpage, A.R. and I.R. Falconer. 2002. Oral Toxicity of
Cylindrospermopsin: No Observed Adverse Effect Level
Determination in Male Swiss Albino Mice. The
Cooperative Research Centre for Water Quality and
Treatment, Salisbury, South Australia. Research Report
No. 13. (93 pages).
Humpage, A.R. and I.R. Falconer. 2003. Oral toxicity of the
cyanobacterial toxin cylindrospermopsin in male Swiss
albino mice: Determination of no observed adverse effect
level for deriving a drinking water guideline value.
Environ. Toxicol. 18(2):94-103.
U.S. EPA (United States Environmental Protection
Agency). 2015. Drinking Water Health Advisory for the
Cyanobacterial Toxin Microcystin. EPA 820R15100,
Washington, DC; June, 2015. Available from:
http://water.epa.gov/drink/standards/hascience.cfm
U.S. EPA (United States Environmental Protection
Agency). 2015. Drinking Water Health Advisory for the
Cyanobacterial Toxin Cylindrospermopsin. EPA
820R15101, Washington, DC; June, 2015. Available from:
http://water.epa.gov/drink/standards/hascience.cfm
U.S. EPA (United States Environmental Protection
Agency). 2015. Health Effects Support Document for the
Cyanobacterial Toxin Microcystins. EPA 820R15102,
Washington, DC; June, 2015. Available from:
http://water.epa.gov/drink/standards/hascience.cfm
U.S. EPA (United States Environmental Protection
Agency). 2015. Health Effects Support Document for the
Cyanobacterial Toxin Cylindrospermopsin. EPA
820R15103, Washington, DC; June, 2015. Available from:
http://water.epa.gov/drink/standards/hascience.cfm
U.S. EPA (United States Environmental Protection
Agency). 2015. Health Effects Support Document for the
Cyanobacterial Toxin Anatoxin-a. EPA 820R15104,
Washington, DC; June, 2015. Available from:
http://water.epa.gov/drink/standards/hascience.cfm
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