HEALTH ADVISORIES
The U.S. Environmental Protection Agency (U.S.
EPA) published national drinking water Health
Advisories for the cyanotoxins microcystins and
cylindrospermopsin (see Table 1). The Health
Advisories provide the cyanotoxins levels in drinking
water less than or equal to which adverse human
health impacts are unlikely to occur over a 10-day
period of time. Health Advisories are developed to
help states and water systems assess local situations
and during emergency situations and spills. They are
not a federally enforceable, regulatory limit.
Given the health concerns that can occur from
cyanotoxins in drinking water, many water systems
are taking actions to manage and reduce the risks
from cyanotoxin contamination in drinking water.
These actions can include steps for cyanotoxin
monitoring, adjusting treatment to address
contamination before levels are of concern and
notifying the public through a Drinking Water
Advisory when tap water toxin levels are a possible
public health concern.
10-DAY HEALTH ADVISORIES
LEVEL
Microcystins
Children pre-school age and
younger (under 6 years old)
0.3 |ig/L
School-age children (6 years
and older)
1.6 jjg/L
SERA
United States
Environmental Protection
Agency
Co-Branding
(optional)
CYANOTOXINS
Cylindrospermopsin
Children pre-school age and
younger (under 6 years old)
0.7 Jjg/L
School-age children (6 years
and older)
3.0 |ig/L
Table 1. U.S. EPA's National 10-Day Health Advisories
DRINKING WATER ADVISORIES
Co-Branding
(optional)
&EPA
United States
Environmental Protection
Agency
MORE INFORMATION
For more information about how HABs are managed
in your tap water contact your public water system.
For more general information see:
www. e pa. g ov/cy a n o h a b s.
EPA: 810-F-16-007

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SUMMARY
Freshwater harmful algal blooms (HABs) are a
growing concern in the United States and worldwide.
Some HABs can produce toxins that are harmful to
humans and animals (see Figure 1). These toxins
can pose challenges to drinking water supplies.
Given this risk, many drinking water systems are
taking actions to manage cyanotoxins in drinking
water and notify the public if tap water toxin levels
become a concern, including issuing Drinking Water
Advisories.
BACKGROUND
Drinking Water Health Advisories
Cyanotoxin Drinking Water Advisory
EVERYONE
risks to humans and animals. Conventional water
treatment (consisting of coagulation, sedimentation,
filtration and chlorination) can generally remove
cyanobacterial cells and low levels of toxins.
However, water systems may face challenges
providing drinking water during a severe bloom event
when there are high cyanobacteria and cyanotoxin
levels in drinking water sources. If cyanotoxins occur
in tap water over a 10-day time period at levels
above the national drinking water Health Advisories,
people are at risk of various adverse health effects
including upset stomach, vomiting and diarrhea as
well as liver and kidney damage.
Cyanobacteria, formerly referred to as blue-green
algae, are found naturally in lakes, rivers, ponds and
other surface waters. When certain conditions exist,
such as in warm water containing an abundance of
nutrients, they can rapidly form harmful algal blooms
(HABs). Some HABs are capable of producing
toxins, called cyanotoxins, which can pose health
Cyanotoxin Drinking Water Advisory
VULNERABLE
POPULATIONS*
NON-VULNERABLE
POPULATIONS
No Cyanotoxin Drinking Water Advisory
EVERYONE
'vulnerable populations = infants, children under the age of six, pregnant
women, nursing mothers, those with pre-existing liver conditions, those
receiving dialysis treatment, the elderly and sensitive populations.
DRINKING WATER ADVISORIES
If a drinking water advisory is issued for cyanotoxins,
instructions for appropriate actions to be taken
by consumers will be described in the advisory
notification. There is a possibility that there will be
different instructions for different population groups,
depending on the levels of cyanotoxin found in the
drinking water.
Using the U.S. Environmental Protection Agency's
national drinking water Health Advisory levels (see
Table 1) for microcystes and cylindrospermopsin
as a guide, ranges of cyanotoxin levels in drinking
water can be shown with the following advisory
levels: green,	and red (see Figure 2).
Green corresponds to drinking water toxin levels
where adverse health impacts are unlikely to
occur for everyone.	indicates drinking
water toxin levels where the risk of adverse health
impacts is higher for infants, young children under
the age of six and other vulnerable populations
(including: pregnant women, nursing mothers, those
with pre-existing liver conditions, those receiving
dialysis treatment, the elderly and other sensitive
populations). Red indicates drinking water toxin
levels above which the risk of adverse health
impacts is higher for everyone drinking the water.
Drinking water systems can elect to issue Drinking
Water Advisories using these categories as guides.
< Figure 2. Possible Drinking Water Health Advisories

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