A	United States	Office of Water	EPA 822-R-19-002
llia>|a"j|Uk	Environmental Mail Code 4304T May 2019
¦¦¦I mm	Protection Agency
Response to Public Comments on the U.S. EPA's Draft
Recommended Human Health Recreational Ambient Water
Quality Criteria or Swimming Advisories for Microcystins
and Cylindrospermopsin

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Notice
This document has been drafted and approved for publication by the Health and Ecological Criteria
Division, Office of Science and Technology, United States Environmental Protection Agency. Mention
of trade names or commercial products does not constitute endorsement or recommendation for use.

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Table of Contents
Introduction	5
Category 1 - General Comments	5
Category 1.1- General Comments - Authority under the Clean Water Act	5
Category 1.2 - General Comments - Support for development of Recreational AWQC and swimming
advisories (Recreational AWQC/SA)	6
Category 1.3 - General Comments - Support for development of swimming advisories, but not
AWQC	8
Category 1.4 - General Comments - Not supportive of approach	9
Category 1.5 - General Comments - Provide linkage to nutrients	11
Category 2 - Stressors	13
Category 2.1 - Stressors - Cyanobacterial cell density and other cyanobacterial-related measures	13
Category 2.2 - Stressors - Consideration of water velocity and other factors	16
Category 2.3 - Stressors - Differential toxicity of microcystin congeners	16
Category 2.4 - Stressors - Develop values for other cyanotoxins (anatoxin-a and nodularin)	17
Category 2.5 - Stressors - Other comments	18
Category 3 - Sources	19
Category 3.1 - Sources - Application of values to marine waters	19
Category 3.2 - Sources - Recreational waters can be drinking water sources	19
Category 3.3 - Sources - Application of Recreational AWQC/SA to all waters of the United States..20
Category 4 - Exposure Routes	20
Category 4.1- Exposure Routes - Incidental ingestion	20
Category 4.2 - Exposure Routes - Inclusion of fish/shellfish ingestion	23
Category 4.3 - Exposure Routes - Relationship to secondary contact	23
Category 4.4 - Exposure Routes - Characterization of dermal and inhalation exposure	24
Category 5 - Receptors	25
Category 5.1 - Receptors - Consideration of multiple lifestages	25
Category 5.2 - Receptors - Protection for companion animals and livestock	26
Category 5.3 - Receptors - Other comments	26
Category 6 - Endpoints	27
Category 6.1 - Endpoints - Consideration of inflammatory and other endpoints	27
Category 6.2 - Endpoints - Other	28
Category 7 - Analysis	28
Category 7.1- Analysis - Deviations from 2000 AWQC Methodology	28
Category 7.2 - Analysis - Relative Source Contribution	29
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Category 7.3 - Analysis - Derivation of the reference doses (RfDs) for microcystins and
cylindrospermopsin	30
General comments	30
Adequacy of database	30
Duration of critical study for derivation of the RfD for microcystins	32
Dose range of the critical study for derivation of the RfD for microcystins	33
Rodent strain used in critical study for derivation of the RfD for microcystins	34
Measure of effect in critical study for derivation of the RfD for microcystins	35
Use of microcystin-LR as a surrogate for all microcystins	35
Selection of critical study for derivation of the RfD for cylindrospermopsin	36
Uncertainty factors	37
Use of animal data in derivation of the RfDs	39
Benchmark dose modeling	39
Category 7.4 - Analysis - Criteria duration and frequency	40
Category 7.5 - Analysis - Exposure duration and other exposure variables	41
Category 7.6 - Analysis - Other comments	42
Category 8 - Implementation	44
Category 8.1- Implementation - Recommend/provide information on methods for cyanotoxins	44
Category 8.2 - Implementation - Use of non-toxin endpoints	45
Category 8.3 - Implementation - Criteria support materials	46
Category 8.4 - Implementation - Impacts of implementation	46
Category 9 - Other General Comments	47
Citations	49
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Introduction
This document summarizes public comments submitted regarding the U.S. Environmental Protection
Agency (EPA) document titled Draft Recommended Human Health Recreational Ambient Water
Quality Criteria or Swimming Advisories for Microcystins and Cylindrospermopsin (Recreational
AWQC/SA) and the EPA's responses. The EPA published the draft Recreational AWQC/SA document
in December 2016. The sections that follow provide summaries of the comments received and the EPA's
responses, which are organized into categories.
Category 1 - General Comments
Category 1.1 - General Comments - Authority under the Clean Water Act
Comments Summary: Comments focused on the Clean Water Act (CWA) and its role in addressing
natural hazards originating from cyanotoxin-producing cyanobacteria. Hall and Associates asserted that
the CWA limits the EPA to considering only man-induced water pollution and not natural hazards. This
commenter recommended that the EPA distinguish between levels of cyanotoxins which are natural, and
those that are above natural levels, indicating a man-induced cyanotoxin pollution problem. The
commenter concludes that the EPA can only regulate cyanobacteria when toxin levels are above natural
levels, and only if said unnaturally high levels have a demonstrable adverse impact on human health.
Response:
The Agency has the authority to develop recommended criteria for water quality under section 304(a)
[U.S. Code 33 section 1314(a)(1)] of the Clean Water Act accurately reflecting the latest scientific
knowledge on the kind and extent of all identifiable effects on health and welfare which may be
expected from the presence of pollutants in any body of water. Elevated levels of cyanobacteria and
cyanotoxins may be expected to result from the presence in a waterbody of pollutants such as
phosphorous and nitrogen and can result in adverse effects on human health, including for recreation
uses. The values recommended by the EPA represent the latest scientific knowledge on the kind and
extent of all identifiable effects on human health and welfare that might be expected from the presence
of microcystins and cylindrospermopsin in a body of water. Section 304(a) does not restrict the EPA
from developing recommended water quality criteria where naturally occurring pollutant concentrations
may in some instances result in an effect on health and welfare.
Importantly, the publication of 304(a) criteria are not regulations, rather they are recommendations that
states may consider in their development of water quality standards or otherwise use to manage water
quality. These values may be adopted as water quality criteria to protect the recreational designated use,
serve as the basis for swimming advisories to protect public health in recreational waters, or both. Even
in jurisdictions where these section 304(a) recommended criteria are adopted as legally-binding water
quality criteria consistent with the procedures set forth in section 303(c), under the Clean Water Act and
the EPA's implementing regulations states have several options to provide regulatory flexibility for
water bodies where natural conditions exceed these criteria. For example, pursuant to 40 CFR
130.10(g)(1), states may remove a designated use, which is not an existing use if the state can
demonstrate that attaining the designated use is not feasible because naturally occurring pollutant
concentrations prevent the attainment of the use. Alternatively, states have the option to develop site-
specific criteria to reflect the presence of naturally occurring pollutants provided that those criteria are
based on sound science and protect the designated use.
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Category 1.2 - General Comments - Support for development of Recreational AWQC
and swimming advisories (Recreational AWQC/SA)
Comments summary: Multiple groups submitted comments in support of the EPA's development of
the Recreational AWQC/SA to protect public health in recreational waters affected by harmful algal
blooms (HABs)1 and the cyanotoxins, microcystins and cylindrospermopsin:
•	The Association of Clean Water Act Administrators and nine states (California Natural resources
Agency Department of Water Resources and State Water Resources Control Board, Massachusetts
Department of Public Health and Department of Environmental Protection, New York State
Department of Environmental Conservation and Department of Health, Oregon Department of
Environmental Quality, Pennsylvania Department of Environmental Protection, Utah Department
of Environmental Quality, Vermont Department of Environmental Conservation, Virginia
Department of Environmental Quality and Department of Health, State of Wisconsin Department
of Natural Resources).
•	One tribe (Karuk Tribe).
•	Other stakeholders consisting of the regulated community, researchers, citizen groups, and the
general public (Surfrider Foundation, Connecticut Citizen-Led Environmental Observatory, Clean
Water Action/Clean Water Fund, Clean Ocean Action, Great Lakes Environmental Law Center,
Lake Erie Foundation, Mississippi River Collaborative, North Carolina Conservation Network et
al. University of North Carolina at Chapel Hill's Institute of Marine Sciences).
Paraphrased comments with some quotations included the following.
•	Association of Clean Water Administrators (ACWA) supports the EPA's efforts to address the
issue of harmful algal blooms (HABs) in recreational waters. ACWA also acknowledged "the
collaboration and dialogue that has occurred between ACWA and the EPA throughout 2016 and
2017 regarding HABs and recognizes the achievements that have emerged from that partnership."
They "appreciate the flexibility that the EPA has extended to states to use the recommended values
for swimming advisories only, as water quality standards, or neither."
•	California Water Boards, State Water Resources Control Board acknowledged the "extensive
effort EPA put into development of the microcystins and cylindrospermopsin criteria, and supports
EPA's efforts to develop proposed human health recreational ambient water quality criteria for
cyanotoxins."
•	The California Environment Protection Agency, "Office of Environmental Health Hazard
Assessment (OEHHA) commends the work that the U.S. Environment Protection Agency has
undertaken to address the risks associated with recreational exposure to microcystins and
cylindrospermopsin... Once finalized, the U.S. EPA's human health recreational criteria and
swimming advisories for microcystins and cylindrospermopsin will provide critical support for
public health officials and water managers nationally."
•	The Commonwealth of Massachusetts, Office of Health and Human Services and
Massachusetts Department of Environmental Protection (MassDEP) stated that "Through a
comprehensive literature review of currently available relevant scientific studies, EPA generated
1 In this and the Recreational AWQC/SA document, harmful cyanobacterial blooms are also known as harmful algal blooms
or HABs.
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draft criteria for both cyanotoxins to help ensure public safety during recreational activities...
MassDEP appreciates EPA efforts to produce a document that summarizes the critical background
information and identifies important issues attributed to HABs."
•	Oregon Department of Environment Quality (ODEQ) supports the EPA's proposal approach to
allow the recommended values to be used as either recreational advisory levels, water quality
standards, or both. ODEQ stated that "Microcystins and cylindrospermopsin are not the same as
typical water quality criteria. Unlike other water quality parameters, these toxins are not
discharged directly into the environment; rather they occur at high levels most often during
harmful algal blooms that form when waterbodies experience an increase in the level of nutrients,
higher than normal water temperatures, low flows, or other issues. As a result, criteria for these
toxins should not be treated as the same as other water quality criteria. It is critical for states to
have tools and strategies to address elevated levels of these toxin in order to understand when
public health is at risk and to act.
•	Pennsylvania Department of Environmental Protection wrote that "The EPA's document
effectively explains the complex, ever-changing, and challenging subject of protecting public
recreationists from HABs. A thorough scientific review resulted in the EPA selecting reasonable
advisory levels for microcystins and cylindrospermopsin... It is expected that advisory levels for
other cyanotoxins will also be determined in the future."
•	The Utah Division of Water Quality "commends and supports EPA's continue efforts to address
water quality concerns and human health effects resulting from harmful algal blooms (HABs).
These draft criteria represent significant progress in that effort. The Utah Division of Water
Quality (UDWQ) is supportive of EPA's draft criteria for cylindrospermopsin and microcystins...
The draft criteria are based on the most recent and relevant scientific literature, and the techniques
used in the criteria calculations are reasonable. Therefore, UDWQ believes these criteria to be
scientifically defensible and appropriately protective of the specific human health concerns
identified in the draft document."
•	The Wisconsin Department of Natural Resources (WDNR) "supports the approach used to
derive the criteria/advisory levels for microcystins and cylindrospermopsin. This approach is in
keeping with EPA's Methodology for Deriving Ambient Water Quality Criteria for the Protection
of Human Health and the Water Quality Guidance for the Great Lakes System (40 CFR 132).
Furthermore, WDNR understands and values the evaluation of children as the receptor for these
pollutants. As children spend more time recreating in the water and tend to ingest more water
while recreating, they are the most likely to be impacted by these toxins."
•	The Vermont Department of Environment Conservation stated that "We support this effort to
develop national guidance by which human health risks from cyanobacteria may be evaluated.
National guidance will facilitate the development of consistent monitoring approaches and foster
consistent messaging for the many stakeholders concerned about these organisms."
•	Commonwealth of Virginia, Virginia Department of Environmental Quality (VDEQ) and
Department of Health (VDH) stated that "There are no significant questions or concerns with the
selected values. Should the recommended advisory thresholds from EPA become final, VDH will
be prepared to amend current recreational advisory guidance for cyanobacteria toxins."
•	The Karuk Tribe, Karuk Community Health Clinic stated that "Overall the Draft EPA Human
Health Recreational Ambient Water Quality Criteria and/or Swimming Advisories for
Microcystins and Cylindrospermopsin document is well structured and relies on sound science to
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formulate the cyanotoxin advisories. We urge the EPA to finalize the advisories, so that States can
use the data to update their cyanotoxin guidelines."
Several commenters (Connecticut Department of Energy and Environmental Protection, New York State
Department of Environmental Conservation and Department of Health, Pennsylvania Department of
Environmental Protection, Vermont Department of Environmental Conservation) suggested additional
information or approaches that could be used to improve the document, including:
•	suggesting the criteria be strengthened by mirroring the approach already being taken by a state
with an existing HAB advisory program.
•	encouraging the EPA to provide more explanation of the science behind the studies used to
generate the criteria.
•	recommending some additions to be made.
Specific points made by these commenters are summarized under the technical topic areas.
Response:
The EPA would like to thank all the states, tribes, and other stakeholders for providing their comments
in support of the development of the Recreational AWQC/SA to protect public health in recreational
waters affected by HABs and the cyanotoxins microcystins and cylindrospermopsin. The EPA
understands the considerable efforts states have put forward to manage water quality and protect the
public from HABs and appreciates them sharing their knowledge as part of the comment process.
The EPA considered the additional information and suggestions provided by all commenters as it made
its final revisions to the document. The EPA is providing this information as recommendations;
however, states have the flexibility to use these as AWQC if they decide to adopt them into their water
quality standards (WQS), swimming advisories, or both. The EPA revised the document to be clear that
the decision on how to use these values is up to the discretion of states. Also, the EPA has worked with
states to develop implementation guidance for these Recreational AWQC/SA for microcystins and
cylindrospermopsin.
Category 1.3 - General Comments - Support for development of swimming advisories,
but not AWQC
Comments Summary: Five commenters supported the development of swimming advisories for
cyanotoxins, but not national recommended 304(a) criteria:
•	Georgia Department of Natural Resources-Georgia Environmental Protection Division
(Georgia EDP) expressed concerns largely about implementation and indicated "Georgia EDP
does not plan on adopting ambient water quality criteria for HABs, but would consider using the
recommended guidance for swim advisories."
•	Kansas Department of Health and Environment (KDHE) "supports EPA's recommended
values that are protective of primary contact recreation, particularly for pre-teenage children
derived from the published science addressing these toxins. KDHE supports the issuance of
swimming advisories to protect the recreating public and intends to amend our current messaging
approaches associated with issuing public notifications during HAB events to incorporate EPA's
recommendations. Harmful Algal Blooms have become the critical water quality issue in Kansas,
and KDHE appreciates EPA's effort to assist with this ever-challenging endeavor."
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•	Ohio Environment Protection Agency stated that "U.S. EPA's proposed numerical values for
swimming advisories and recreational criteria were calculated using standard risk assumptions
and are similar to Ohio's recreational advisory levels. Ohio is supportive of U.S. EPA's effort to
establish numeric thresholds for cyanotoxins to guide recreational advisories. This information is
important and will help state and local officials in their efforts to provide the public the most up-
to-date advice regarding potential health risks encountered while swimming in our nation's
waters."
•	The National Association of Clean Water Agencies requested that the EPA clarify in the
document that states have the "option to adopt only the swimming advisories without also
adopting the AWQC."
•	Agricultural Retailers Association et al. indicate that the EPA should consider publishing the
information only as swimming advisories under 304(a)(2).
Response:
The EPA is providing this information as recommendations; however, states have the flexibility to use
these as AWQC if they decide to adopt them into their WQS, as swimming advisories, or both. The EPA
revised the document to be clear that the decision on how to use these values is up to the discretion of
states.
The EPA appreciates the suggestions provided by states on how to implement these reactional criteria
and swimming advisories and has worked with states to develop implementation guidance for these
recreational criteria and swimming advisories for microcystins and cylindrospermopsin.
Category 1.4 - General Comments - Not supportive of approach
Comments Summary: The EPA received comments from states (Iowa Department of Natural
Resources, Kentucky Division of Water, Texas Commission on Environmental Quality, the State of
Wisconsin Department of Natural Resources) and multiple other stakeholders (Agricultural Retailers
Association et al., City and County of Honolulu Department of Environmental Services Division of
Environmental Quality, Hall and Associates, Mississippi River Collaborative, National Association of
Clean Water Agencies, North Carolina Lower Neuse River Basin Association, North Carolina Neuse
River Compliance Association, Virginia Association of Municipal Wastewater Agencies, American
Waterworks Association) that were not supportive of Recreational AWQC/SA.
Two states (Kentucky Division of Water and Wisconsin Department of Natural Resources) suggested
the information be published only as 304(a)(2) information.
The Agricultural Retailers Association et al. cited the EPA's "court-ordered process" which included
expert scientific workshop to define a science plan, epidemiology studies, multiple research and
stakeholder meetings, and opportunities for stakeholder comment on the criteria and implementation
guidance. The commenter requested that the EPA implement such an approach before taking final action
on the criteria.
Commenters provided other specific concerns with the publication of the draft criteria. These included:
•	Wyoming Department of Environmental Quality "has questions regarding: criteria
implementation; the assumptions and statistical methodologies that were used during criteria
and/or advisory value development; and missing or misleading information."
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•	Iowa Department of Natural Resources had questions about the derivation of the values and
implementation, which are addressed further below. They asked the EPA to base criteria on an
appropriately designed epidemiological study focusing on the acute effects of elevated
cyanotoxins on human health during recreational water activities such as swimming.
•	Two commenters (Hall and Associates, Iowa Department of Natural Resources) noted that
the proposed criteria create an artificially stringent standard (or "overprotective criteria")
resulting in unclear, and potentially unnecessary, burdens placed on states to implement them.
•	The Agricultural Retailers Association et al. expressed concern with the overall nature of the
draft document because it appears that the EPA is "blending" the concepts of non-regulatory
health advisories for short-term exposure to microcystins in drinking water with Clean Water Act
criteria for fecal indicator bacteria at freshwater and marine beaches.
•	The Virginia Association of Municipal Wastewater Agencies unsupportive of the AWQC due
to what they describe as the paucity of scientific data in support of the derivation of draft AWQC
values.
•	Two commenters (Hall and Associates and Washington DC American Water Works
Association) expressed concern over the economic impact of the criteria. Hall and Associates
voiced concern that the EPA would use the criteria to impose nutrient reduction requirements
that would lead to detrimental economic impacts without benefit. This commenter stated that this
effort represents the EPA's attempt to regulate a naturally occurring group of organisms in an
effort to protect recreational uses that do not appear to be adversely affected by this parameter.
•	Two commenters (North Carolina Neuse River Compliance Association and North Carolina
Lower Neuse River Basin Association) voiced concern with the use of the draft criteria to
stimulate rules and regulations, specifically those related to 303(d) listing decisions,
exceedances, and the National Pollutant Discharge Elimination System (NPDES) permitting
process. These commenters suggested that the EPA remove from the draft document any
mention that numeric thresholds be used as the basis for regulation development.
•	The City and County of Honolulu Department of Environmental Services Division of
Environmental Quality believed that the EPA should not have issued the AWQC values for
microcystins and cylindrospermopsin because of the lack of consideration of site-specific
conditions, which may reduce the likelihood of formation of algal blooms that generate these
cyanotoxins.
•	The National Association of Clean Water Agencies expressed concerns about considerable
implementation challenges.
Response:
The Recreational AWQC/SA are recommendations, not regulations. Unlike the EPA's 2012
Recreational Water Quality Criteria (RWQC) (U.S. EPA 2012), these recommendations are not subject
to a consent decree resulting from litigation. States can choose to implement as SA, AWQC, both, or not
at all. The EPA leveraged the science from its peer reviewed Health Effects Support Documents
(HESDs) and provided the criteria for public comment. The EPA engaged with states through ACWA
throughout this process. Detailed responses to specific concerns related to the exposure assumptions are
discussed below.
The AWQC are based on the same peer reviewed, published science on the adverse health effects from
exposure to microcystins and cylindrospermopsin that support the drinking water Health Advisories
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(HAs) developed for these compounds, but differ in the exposure scenario. The Recreational
AWQC/SAs include recreation-specific exposure parameters that reflect the increased exposure
experienced by children during primary contact recreation. The EPA has revised the document to
provide additional description of assumptions used in the derivation of the Recreational AWQC/SAs.
The specific responses to comments about assumptions and approaches used for criteria derivation are
addressed in other comment categories, including categories 6, 7, and 8. Scientific uncertainties have
also been transparently addressed in the section on effects characterization in the document (section 7).
The EPA has also clarified that these criteria were developed for freshwaters. The EPA notes that site-
specific criteria can be developed.2
The Recreational AWQC/SA are recommendations available to states to help protect human health
during primary contact recreation. As recommendations, they do not impose costs. The Recreational
AWQC/SA were not developed as a result of a court-ordered action. Communities across the country
have experienced loss of economic benefits due to beach closures resulting from HABs, and the majority
of comments from states and other stakeholders indicate the need for such tools to assist states and tribes
in managing recreational water quality. The EPA has been working collaboratively with states to
develop implementation materials and has published materials for beach managers; see Monitoring and
Responding to Cvanobacteria and Cvanotoxins in Recreational Waters (U.S. EPA 2017b).
Publishing this information under 304(a)(1) rather than 304(a)(2) provides clarity for those states who
wish to use these as criteria to protect state-designated recreational uses in their WQS. The 304(a)(1)
AWQC are recommendations only.
Sections 2.5.2.1 of the HAs for microcystins and cylindrospermopsin (U.S. EPA 2015e, 2015f),
summarize human data for exposures to microcystins and cylindrospermopsin. As noted in the HAs, the
human data on the oral toxicity of microcystins and cylindrospermopsin are limited by the potential co-
exposure to other pathogens and toxins, by the lack of quantitative information, and by the failure to
control for confounding factors. The Recreational AWQC/SA document also includes a discussion of
additional recreational acute exposure case reports published since 2015 and human studies evaluating
effects following exposures to cyanobacterial cells (see Recreational AWQC/SA section 7.5). Taken
together, the weight of evidence for human studies supports the conclusion that microcystins and
cylindrospermopsin exposures are a human health hazard. At this time, the EPA concludes that the
human studies are adequate for use qualitatively in hazard identification but not for use quantitatively
(see Recreational AWQC/SA section 7.5).
Finally, while it is widely accepted that excess nutrients are an important factor that contribute to algal
bloom formation and occurrence of cyanotoxins, these Recreational AWQC/SA do not address nutrient
contamination.
Category 1.5 - General Comments - Provide linkage to nutrients
Comments Summary: Several commenters (Agricultural Retailers Association et al., Association of
Clean Water Administrators, Hall and Associates, State of Wisconsin Department of Natural Resources,
2 The EPA's regulations state in 40 CFR section 131.11(b)(1) provide that "In establishing criteria, States should (1)
Establish numerical values based on (i) 304(a) Guidance; or (ii) 304(a) Guidance modified to reflect site-specific conditions;
or (iii) Other scientifically defensible methods."
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National Association of Clean Water Agencies) stated that the link between nutrients and cyanobacteria
and or cyanotoxins from algal blooms is not clear and has no direct quantitative correlation.
Two commenters (Clean Ocean Action, Clean Water Action/Clean Water Fund) stated that while
naturally occurring environmental conditions may generate HABs, nutrient pollution and warming water
temperatures are more likely the underlying causes of HAB outbreaks in marine waters. These two
commenters acknowledged the EPA's studies of the links between HABs, nutrient pollution, warming
water temperatures, and other environmental changes might make HABs more frequent and more
intense.
The National Association of Clean Water Agencies noted that establishing AWQC-based permit
requirements for cyanotoxins would be difficult because of the absence of related nutrient criteria. The
State of Wisconsin Department of Natural Resources recommended that the EPA wait to finalize the
criteria until they have developed guidance on how to manage a waterbody that does not meet the
microcystins or cylindrospermopsin criteria and also have published nutrient criteria. Hall and
Associates stated that the association between point source loads of nutrients and cyanotoxin
concentration is weak and argued for a case-by-case assessment of that the relationship between
nutrients and cyanobacteria or cyanotoxins. The Association of Clean Water Administrators requested
additional information on resources and models used to relate levels of nutrients and cyanotoxins.
Several commenters (Hall and Associates, State of Wisconsin Department of Natural Resources)
expressed concern over the challenges of meeting the proposed water quality criteria in waterbodies
given natural conditions that impact nutrient concentration in U.S. waters. Two commenters (Kansas
Department of Health and Environment, National Association of Clean Water Agencies) stated that
controlling nutrient discharge will not be a reliably effective means of meeting the recreational criteria
goals. One of these commenters (National Association of Clean Water Agencies) suggested that this
challenge stems from different parameters affecting nutrients and cyanotoxins. The American Water
Works Association requested additional information about how the criteria would be used; asking
whether, for example, cyanotoxin ambient water quality criteria would be used to improve management
of nutrient loadings from non-point sources. The Agricultural Retailers Association et al. noted that the
EPA and states already have frameworks to address nutrient pollution, and states are already taking
initiative to control nutrients. They suggest that given the lack of monitoring, the public would be better
informed by guidance based on visual signs. This commenter indicated that nutrient pollution control
from point and nonpoint sources might not solve the problem of algal blooms. The Iowa Farm Bureau
Federation stated that the EPA should continue to support state partnerships, and that federal mandates
to implement 304(a) criteria under 40 CFR section 131.20(a) will greatly strain available resources and
viability and will potentially reverse progress that has already been made. The Kentucky Division of
Water suggested 303(d) listings for excessive nutrients provide a more appropriate management strategy
than 303(d) listings for cyanotoxins.
One commenter (Merced Irrigation District) provided reference to a study showing the association
between Microcystis species and an inorganic nitrogen pool from a wastewater treatment facility.
The Lower Neuse Basin Association noted that the North Carolina Department of Health and Human
Services (DHHS) provides a practical set of recommendations to protect the public "since most
recreational waters are not and never will be monitored."
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One commenter (Clean Ocean Action) supported development of numeric criteria for nutrients in saline
waterbodies, noting that nutrient pollution and warming water temperatures are more likely the
underlying cause of algal blooms rather than naturally occurring environmental conditions. Another
commenter (Clean Water Action/Clean Water Fund) noted the increase in reported incidents of HABs in
recent years, agreeing with the EPA's characterization of the environmental conditions contributing to
these blooms. This commenter encouraged the EPA to continue to implement activities identified in the
2016 Nutrient Memorandum (U.S EPA 2016).
Response:
The Recreational AWQC/SA document does not rely on the availability of nutrient criteria to be
implemented. The EPA recognizes that preventing harmful algal toxins production in the surface waters
implies preventing or limiting the growth of toxin-producing algae and the nutrient supplies that support
that growth. The EPA is working with states and with ACWA to develop additional information on
resources and models to relate levels of nutrients and cyanotoxins. Specifically, the EPA is updating
304(a) criteria recommendations for nutrient pollution (i.e., nitrogen and phosphorus) for lakes that
address designated uses for drinking water, recreation, and aquatic life uses. In the interim, states can
rely on almost 20 years of the EPA's policies and regulatory guidance on state development of numeric
nutrient criteria, as well as their CWA regulatory authorities under section 303(c), to pursue effective
point source interventions that prevent excess nutrients that contribute to the occurrence of microcystins
and cylindrospermopsin. The EPA agrees with comments that management frameworks (e.g., state
nutrient reduction strategies, the Agency's guidance) exist for states to take action to reduce nutrient
pollution. The EPA also agrees with comments that states are taking tangible actions to implement these
frameworks. The EPA intends the Recreational AWQC/SA for cyanotoxins to provide states with new
tools to manage recreational uses, to complement rather than to take the place of other state efforts
related to nutrient pollution.
The EPA disagrees with the comments that the link between nutrients and cyanotoxins is not clear. The
EPA refers the commenters to Recreational AWQC/SA section 3.1.1.1 for a summary of the scientific,
peer reviewed literature describing relationships between nutrients and cyanotoxins.
The EPA is providing other tools that can be used to address algal toxins and recognizes that states have
multiple approaches to address these issues. These tools are specified in category 8 (implementation).
Category 2 - Stressors
Category 2.1 - Stressors - Cyanobacterial cell density and other cyanobacterial-related
measures
Comments Summary: Five states (Commonwealth of Massachusetts/Massachusetts Department of
Public Health/Massachusetts Department of Environmental Protection, Connecticut Department of
Energy and Environmental Protection, New York State Department of Environmental Conservation and
Department of Health, Pennsylvania Department of Environmental Protection, State of Utah Department
of Environmental Quality Division of Water Quality), one tribe (Karuk Tribe), and one non-
governmental stakeholder (North Carolina Conservation Network) submitted comments that encouraged
the EPA to include a recommendation for a cyanobacterial cell density or other biomass-related metric
(including visual observations of a cyanobacterial bloom). The points they made include:
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•	Cell count is a valuable tool that states currently use in combination with toxin levels to evaluate
lake quality and to manage beaches to protect public health (Pennsylvania Department of
Environmental Protection).
•	Measures of cells can provide a proactive approach to protect public health before toxins are
produced (Pennsylvania Department of Environmental Protection).
•	Measures of cells are easier to implement than toxin measurements and facilitate a more rapid
response than toxin analysis (North Carolina Conservation Network).
•	Because more than one cyanobacteria genera are able to produce microcystins, and the
production of cyanotoxins is unpredictable, using only Microcystis species as the indicator of
toxin production (and calculation of cell density) is limiting. Additional ways of evaluating risk
are necessary (scum observation, total cyanobacteria) to protect recreational uses (Massachusetts
Department of Public Health and Massachusetts Department of Environmental Protection).
•	Even if dose-response cannot be established, the EPA could set an upper level of cyanobacterial
density to mitigate risks of inflammatory responses. Utah uses the World Health Organization
(WHO) level of 100,000 cells. The Karuk Tribe uses 5,000 cells. Commenters asked whether the
EPA would support states continued use of cell benchmarks.
•	Qualitative criteria of visual inspection of blooms (e.g., discolored water and surface scums)
should also be recommended along with toxin recommendations to avoid observable blooms and
can be more public health protective than monitoring only the two toxins (Vermont Department
of Environmental Conservation, Connecticut Department of Energy and Environmental
Protection, Massachusetts Department of Public Health and Massachusetts Department of
Environmental Protection, New York State Department of Environmental Conservation and
Department of Health).
•	One state (Wisconsin Department of Environmental Protection) commented on the lack of
current science to support a recommendation of cell count as criteria and recommended working
toward evaluating inflammatory effects.
•	Another state (Pennsylvania Department of Environmental Protection) requested the EPA
develop guidance on cyanobacterial biovolume to monitor cyanotoxins using pigment detection
and fluorescence.
•	Another state (Vermont Department of Environmental Conservation) recommended deleting cell
density information from the document. In their experience, there was no clear link between cell
density and likelihood of exceedance of toxin criteria at the cell density limit identified
qualitatively by the EPA (20,000 cells/mL) at which microcystins criteria "might" be exceeded.
They do support use of visual cues as guidelines indicating the level of risk in public notification
systems and for developing narrative criteria.
•	The Mississippi River Collaborative asserted that the use of cyanobacterial cell densities
continues to be highly unreliable for use in setting quantitative guidelines, since toxin levels vary
over time and environmental conditions.
Many states supported additional research to better understand stressor response relationships with cells
including inflammatory effects. Ohio Environmental Protection Agency suggested epidemiology studies
be conducted to address dermal and inflammatory endpoints before establishing criteria for HABs.
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Response:
The EPA did not include criteria based on total cyanobacterial density (or the related measures such as
biovolume, chlorophyll a, or phycocyanin) values related to inflammatory health endpoints due to the
variability in the evidence in the literature linking levels of cyanobacteria and health effects. The
rationale for this decision is discussed in the Effects Characterization section of the document
(Recreational AWQC/SA section 7.5).
The EPA understands that some states regard measures of cyanobacterial cells as a valuable tool for
managing water quality and protecting public health. The EPA provides a comparison of cyanobacterial
cell density values for toxin-producing, or toxigenic, cells related to the recommended toxin
concentrations in the Effects Characterization section of the document (Recreational AWQC/SA section
7.5.3). This approach, used by the WHO and others, relies on information found in the scientific
literature on toxin quotas—concentrations of toxin associated with cyanobacterial cells—to develop a
cell density related to the toxin-associated endpoints. Australia and some U.S. states have used a similar
approach to develop their recreational water guideline values for toxigenic cyanobacteria and total
cyanobacterial density values. The EPA conducted a literature search to compile additional information
on microcystins and cylindrospermopsin quotas to improve understanding of the relationship between
toxin levels and cyanobacterial biomass. The EPA reviewed the literature to determine minimum,
maximum, and mean microcystins and cylindrospermopsin quotas for some common cyanobacterial
genera. The EPA has included the results of the literature search and this analysis in the revised
document (Recreational AWQC/SA Appendix G) in lieu of criteria based on cell count as additional
information for states to consider in evaluating water quality. The EPA is retaining the characterization
of cell density associated with toxin concentration in this report and has updated the cell density based
on updates made to toxin concentrations as a result of public comment. The EPA recognizes that states
and others may estimate toxigenic cell density using different assumptions or local data that are also
reasonable approaches.
The EPA clarified that visual inspection alone cannot differentiate between toxigenic species and non-
toxigenic species of cyanobacteria (Recreational AWQC/SA sections 3.1 and 7.5.2) and has added
reference to an approach adopted by Ohio that uses DNA markers to identify cyanobacterial cells
(Recreational AWQC/SA section 7.5.2). The EPA agrees that research to improve and validate
indicators of potential HABs and cyanotoxins exposures would be beneficial.
The EPA understands that many states use qualitative or visual inspection information as a component
of their health protective criteria or monitoring programs. Implementation materials the EPA has
published provide more information on how such indicators can be considered to manage water quality
(see U.S. EPA 2017b). However, visual inspection alone is insufficient to serve as a criterion because
elevated cyanotoxin levels may be present in the absence of a visual bloom (Recreational AWQC/SA
section 3.2.5.2).
The EPA added summaries of research on alternative detection approaches and indicators for
cyanobacteria and cyanotoxins to the revised document (Recreational AWQC/SA section 7.5.2). Please
refer to responses in category 8, Implementation, of this report for the EPA's efforts and plans to
provide further guidance for monitoring.
The EPA considered other scientific references the commenters provided and revised the text to improve
clarity.
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Category 2.2 - Stressors - Consideration of water velocity and other factors
Comments Summary: The California Department of Water Resources said that the proposed guidance
fails to include water velocity as a contributing factor in HAB formation. They recommended that water
velocity be included as a contributing environmental factor in HAB formation in all lists and statements
within the draft.
The National Association of Clean Water Agencies noted that there are differences in the fate and
transport of toxins in flowing rivers and lakes and these differences could impact the applicability of
these Recreational AWQC/SA. Specifically, the residence time and concentration of toxins in rivers can
differ from lakes. This difference might impact data applicability between these two waterbody types.
The commenter asked if the criteria apply to all water bodies.
California's Merced Irrigation District commented that the California Sacramento-San Joaquin River
Delta is a complex ecosystem and factors driving occurrence of cyanobacteria are poorly understood but
influenced by temperature, streamflow, and other factors.
Response:
The EPA agrees that water flow rate may be a factor that affects the formation of HABs; this is noted in
section 3.1.1 (Environmental Factors Influencing Occurrence) of the Recreational AWQC/SA
document. The EPA also agrees that differences in the fate and transport of toxins, as well as ecosystem
characteristics can influence the concentration of toxins to which people are exposed.
Category 2.3 - Stressors - Differential toxicity of microcystin congeners
Comments Summary: Three commenters (Commonwealth of Massachusetts/Massachusetts
Department of Public Health/Massachusetts Department of Environmental Protection, Mississippi River
Collaborative, State of Wyoming Department of Environmental Quality) raised concerns about the use
of microcystin-LR to derive the microcystins reference dose. The Mississippi River Collaborative
suggested that microcystin-LR may only be approximately 25 to 40 percent of the total microcystin
concentration in a cyanobacteria bloom, and there are more than 100 microcystin congeners. The
Wyoming Department of Environmental Quality questioned whether this value is overly stringent, given
that microcystin-LR is considered to be as toxic as or more toxic than other congeners. Another
commenter (Commonwealth of Massachusetts/Massachusetts Department of Public Health/
Massachusetts Department of Environmental Protection) questioned whether microcystin-LR is more
toxic than other congeners, since a study conducted by Fischer et al. (2010) suggested that higher
cellular uptake of microcystin-LW and -LF versus microcystin-LR might lead to higher toxic effects
from these other congeners. The Wyoming Department of Environmental Quality requested additional
information on the toxicity and distribution of microcystin congeners, and questioned whether the
reference dose derived from microcystin-LR has limited applicability to certain states or ecoregions.
The Florida Department of Environmental Protection and the Mississippi River Collaborative
commented on cylindrospermopsin congeners, requesting presentation of additional congeners in a table
format and presentation of rationale for not considering the other known cylindrospermopsin
cyanotoxins in developing the draft criteria.
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Response:
The EPA is aware of available reliable data on the relative toxicity of different congeners of
microcystins and refers the commenters to sections 3.2.1 (Physical Chemical Properties) and 5.1.1.1
(Animal Toxicity Studies for Microcystins) of the Recreational AWQC/SA for its rationale for using
microcystin-LR to represent other congeners. Additional details can be found in section 4.1 of the EPA's
HA for microcystins (U.S. EPA 2015e), which describes the basis for using microcystin-LR as a
surrogate for total microcystins.
The EPA revised the Recreational AWQC/SA document to identify other congeners of
cylindrospermopsin and clarified the lack of physical/chemical and health effects data for these
congeners.
Category 2.4 - Stressors - Develop values for other cyanotoxins (anatoxin-a and
nodularin)
Comments Summary: Six commenters (California State Water Resources Control Board,
Commonwealth of Massachusetts/Massachusetts Department of Public Health/Massachusetts
Department of Environmental Protection, Connecticut Department of Energy and Environmental
Protection, Mississippi River Collaborative, New Jersey Department of Environmental Protection,
Pennsylvania Department of Environmental Protection) encouraged the EPA to expand their research of
additional cyanotoxins of concern, including anatoxin-a, saxitoxin, or nodularins, and develop
recreational guidelines to protect the public from these other cyanotoxins.
Five of these commenters (California State Water Resources Control Board, Commonwealth of
Massachusetts/Massachusetts Department of Public Health/Massachusetts Department of Environmental
Protection, Connecticut Department of Energy and Environmental Protection, Mississippi River
Collaborative, New Jersey Department of Environmental Protection) supported the development of
criteria for anatoxin-a, citing its frequent occurrence in waterbodies throughout the United States and its
lethality in both humans and animals. The Commonwealth of Massachusetts/Massachusetts Department
of Public Health/Massachusetts Department of Environmental Protection specifically asked for
clarification on why anatoxin was not evaluated as part of the criteria. New Jersey Department of
Environmental Protection cited toxicity data and an approach for developing a Reference Dose (RfD) for
anatoxin-a and emphasized that their health protective approach with the available data should be
considered in developing criteria for anatoxin-a since it is a neurotoxin and can have a lethal endpoint.
Pennsylvania Department of Environmental Protection suggested that the EPA criteria should also
include nodularin due to its co-occurrence with microcystins and the similar toxic effects it can have on
organisms. They noted based on experience that microcystin detection ELISA kits detect both
microcystins and nodularin.
Response:
The EPA published an HESD for anatoxin-a in 2015 (U.S. EPA 2015d). This document describes the
available toxicity data for anatoxin-a, including the studies identified by New Jersey Department of
Environmental Protection. After consideration of these data from studies by Astrachan and Archer
(1981); Astrachan et al. (1980); and Fawell et al. (1994, 1999), the EPA determined that the
uncertainties in the Fawell et al. (1994, 1999) results combined with the data reporting deficiencies of
the Astrachan and Archer (1981) and Astrachan et al. (1980) studies were inadequate to develop an oral
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toxicity value (RfD) for anatoxin-a. The EPA's HESD for anatoxin-a underwent peer review and the
reviewers supported this conclusion. Based on that, the EPA did not develop an RfD for anatoxin-a. The
EPA continues to evaluate the available information on human health risk associated with anatoxin-a.
The EPA's Algal Toxin Risk Assessment and Management Strategic Plan (U.S. EPA 2015a) indicates
that the Agency will continue to evaluate additional toxicity data that may become available for these
three cyanotoxins.
Nodularin is frequently detected in surface waters in the United States, especially in the Great Salt Lake
in Utah. Although nodularin and microcystin-LR are very similar in the structure, use the same
transporters, inhibit the same proteins, and produce similar LD50 values in comparable toxicity tests,
relevant toxicity data such as uptake and excretion of nodularin, and acute, sub-chronic and chronic
adverse effects from oral exposure to nodularin are not available.
Category 2.5 - Stressors - Other comments
Comments Summary: Mississippi River Collaborative observed that synergistic and additive
interactions among cyanotoxins (and other toxic substances) were not considered in the draft criteria.
Mississippi River Collaborative strongly encouraged the EPA to address the question of data gaps
regarding additive and synergistic effects of cyanotoxins in order to protect public health. They cited
ecological and in vitro studies suggesting the cyanotoxins act additively and synergistically with each
other and other toxic substances.
The North Carolina Conservation Network et al. noted that levels of cyanobacteria have been identified
at counts above 100,000 cells/mL at multiple sample sites, signaling an increase in the frequency of
blooms. This commenter added that data on toxin exposure via these blooms is not systematic due to the
nature of data collection practices (i.e., collection on a complaint-driven basis).
Two commenters (Hall and Associates, Merced Irrigation District) noted the challenges associated with
understanding the physical drivers associated with blooms and predicting their abundance, formation,
distribution, and control; studies of these drivers are ongoing. One commenter (Merced Irrigation
District) shared that warmer water temperature and streamflow appear to be important physical drivers
for controlling the growth rate of cyanobacteria. The commenter (Merced Irrigation District) supported
additional monitoring and modeling to develop a complex model to predict development of HABs. One
commenter (Hall and Associates) noted the ubiquitous nature of cyanotoxins found in nearly every type
of water body, even those in pristine or near-pristine watersheds. Hall and Associates concluded that
cyanotoxin occurrence is not always associated with human activities and, for all practical purposes,
cannot always be prevented. The Agricultural Retailers Association et al. said that in some instances,
even the most effective point and nonpoint source controls will not be sufficient to prevent HABs.
Response:
Regarding the comment about synergistic and additive effects, the EPA identified key research gaps in
its HESDs (see HESD section 8.0) for microcystins and cylindrospermopsin. Included on these lists
were the potential health risks from exposure to mixtures of microcystins or cylindrospermopsin with
other cyanotoxins and chemical stressors present in ambient or drinking water supplies. The studies
cited by commenters inform potential for ecological toxicity, but are not relevant to human health hazard
assessment.
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The EPA acknowledges the complexity of bloom occurrence and cyanotoxin production. However, at
this time the science is sufficient to develop a recommendation of microcystins and cylindrospermopsin
levels in recreational waters to protect human health while recreating. Although cyanotoxin occurrence
is not always preventable, human exposure to cyanotoxins through recreational activities can be
managed using tools that include the EPA's Recreational AWQC/SA.
Category 3 - Sources
Category 3.1 - Sources - Application of values to marine waters
Comments Summary: Two comm enters (Commonwealth of Massachusetts, Massachusetts Department
of Public Health and Massachusetts Department of Environmental Protection, Florida Department of
Environmental Protection) point out that the fact sheet accompanying the draft document states the
recommended criteria apply to fresh and marine waters, while the document only addresses freshwaters.
They requested clarification and additional supporting documentation regarding the occurrence of the
two cyanotoxins in the marine environment and the difference in incidental ingestion rates for fresh and
marine waters.
Response:
The recommended values for microcystins and cylindrospermopsin were developed for fresh
recreational waters. The fact sheet that accompanied the draft document mistakenly stated that the
criteria apply to fresh or marine waters. The fact sheet will be revised to make it clear that the values
were developed for freshwaters. The EPA revised the document to further clarify that the values were
developed for freshwaters.
The EPA is aware that it is possible for toxins produced by cyanobacteria in freshwaters to be carried
downstream to estuarine and coastal marine waters, potentially affecting people recreating in those
waters. The document does not provide recommendations for those waters, however, it was revised to
include more information and new studies on occurrence of these cyanotoxins in estuarine and marine
waters (Recreational AWQC/SA section 3.2.3). A study published in 2017 (Preece et al. 2017), after the
draft Recreational AWQC/SA document was released, collates information from multiple studies
demonstrating microcystins produced by cyanobacteria in fresh waters can affect estuarine and coastal
waters and describing the potential for some cyanobacteria to be salt-tolerant and persist in marine
waters.
The EPA also included available data on ingestion volumes for fresh and marine waters in the revised
Recreational AWQC/SA document (Appendix F).
Category 3.2 - Sources - Recreational waters can be drinking water sources
Comment summary: The Clean Water Action/Clean Water Fund stated that blooms often occur in
lakes and rivers used for both recreation and as sources of drinking water and cited the 2014 Toledo,
Ohio and the 2016 City of Ingleside, Texas blooms.
Response:
The EPA agrees that toxigenic HABs in lakes and rivers can impact waters that are designated as both
drinking water and recreational uses. Nationally, approximately 15 percent of drinking water intakes
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overlap with recreational waters within the intake's source water protection area, representing over
10,000 recreational assessment units. Blooms or elevated concentrations of cyanotoxins in recreational
waters may be a sentinel for drinking water treatment operators to enhance monitoring to ensure
drinking water is protected. The EPA published materials for drinking water plant operators to provide
information on treatment approaches that can be employed to reduce ambient water toxin concentrations
that might be found in their sources waters. Refer to the EP A's Recommendations for Public Water
Systems to Manage Cyanotoxins in Drinking Water (U.S. EPA 2015b).
Category 3.3 - Sources - Application of Recreational AWQC/SA to all waters of the
United States
Comment summary: Hall and Associates commented that because the criteria apply to toxic
substances, the criteria would apply to all waters of the United States, including areas where recreational
activity is unlikely, such as "ditches, puddles, dead end coves of lakes, mudflats, areas with extensive
rooted aquatic vegetation." They argue that the criteria should not apply to these situations where there
is no relationship between actual use protection needs and the criteria. They mention wetlands and bird
sanctuaries where recreational activities occur, but that may never be able to meet the cyanotoxin
criteria.
Response:
As stated in the introduction to the Recreational AWQC/SA, section 304(a) of the Clean Water Act
(CWA) requires the Administrator of the EPA to publish water quality criteria that accurately reflect the
latest scientific knowledge on the kind and extent of all identifiable effects on health and welfare that
might be expected from the presence of pollutants in any body of water. States define in their water
quality standards the water quality goals of a water body or portion thereof, which includes designating
the use or uses to be made of the water. These Recreational AWQC/SA are recommendations for states
who may adopt them, or other scientifically defensible information, into their state standards to protect
the designated uses of state waters.
Category 4 - Exposure Routes
Category 4.1 - Exposure Routes - Incidental ingestion
Comments Summary: Commenters had mixed opinions regarding the incidental ingestion while
recreating scenario used to derive the recommended toxin values. For example, the California Office of
Environmental Health Hazard Assessment considered the inputs to be "very conservative but
defensible." The Hampton Roads Sanitation district stated the children's recreation scenario is
"acceptable." Six commenters (Hall and Associates, Agricultural Retailers Association et al., Iowa
Department of Natural Resources, National Association of Clean Water Agencies, Florida Department
of Environmental Protection, State of Wyoming Department of Environmental Quality) were concerned
that the inputs were too conservative.
Several questions were raised regarding the EPA's approach for assessing incidental ingestion. The
Florida Department of Environmental Protection suggested that the EPA use a probabilistic risk-based
approach for calculating the ingestion rate, or at least provide increased documentation of the key
computations and formulas used to estimate incidental ingestion in the R script. The Iowa Department of
Natural Resources et al. stated that the EPA used an unrealistic ingestion scenario based on chronic
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instead of acute exposures. Hall and Associates stated that pool water would not be consumed like
marine water because salt content leads to abdominal distress. Similarly, people are more likely to avoid
swallowing algal bloom water compared to pool water.
Response:
The EPA used an estimate of incidental ingestion of ambient water while swimming based on the
Agency's Exposure Factors Handbook (U.S. EPA 2011) and new information for incidental ingestion
from a new and larger study by Dufour et al. (2017). This study was published subsequent to the draft,
and addresses many of the concerns identified in comments. See section 4.2.3.1 of the Recreational
AWQC/SA. The EPA provided the R script in Appendix E of the draft document.
The EPA's 2000 Methodology for Deriving Ambient Water Quality Criteria for the Protection of
Human Health can be used for short- or long-term scenarios (section 4.3) (U.S. EPA 2000). The EPA
used a short-term scenario for when people recreate. See responses in comment Category 7.3, Analysis -
Derivation of the Reference Dose (RfD) for responses to the comments related to the RfD. The RfDs
derived for microcystins and cylindrospermopsin are considered short-term values.
The EPA's recommendations apply to freshwaters with a recreational designated use. The EPA added
clarifying language to the Recreational AWQC/SA document. The EPA also added language discussing
the potential for cyanobacteria to affect downstream waters.
The EPA revised the Recreational AWQC/SA document to discuss in more detail swimming durations
in different water types; see Appendix F.
Comments Summary: Other comments were focused on children's recreational exposure. The State of
Wisconsin Department of Natural Resources questioned whether the children's scenario would cover
high contact activities like water skiing and how such activity would impact exposure. The National
Association of Clean Water Agencies stated that although studies agree that children ingest more than
adults, these ingestion rates vary from study to study. The Agricultural Retailers Association et al.
pointed out the EPA's Office of Pesticides Programs (OPP) uses 0.050 L/hour based on the assumption
that non-competitive, adult swimmers ingest twice as much as competitive swimmers and that children
ingest twice as much as (non-competitive) adults. The Mississippi River Collaborative stated that one to
four year-olds might have a higher ingestion rate than the six to 11 year-olds and that the lack of
quantitative data for the one to four year-olds prevents analysis of whether the EPA's approach was
sufficiently conservative to protect that younger age group. The State of Wyoming Department of
Environmental Quality suggested that using different age cohorts, especially those with small sample
sizes, for each input value may result in misrepresentation of the target population.
Response:
The EPA described in section 4.2.3 its rationale for selecting incidental ingestion during primary contact
activities (such as swimming) in derivation of the recreational criteria and swimming advisories. See
section 7.4.1 of the Recreational AWQC/SA document for a discussion of limited information available
related to water skiing exposure.
The EPA's SWIMODEL used by OPP in assessments is described in Recreational AWQC/SA section
7.2, and explains that competitive swimming duration practices (e.g., children swimming laps) are less
relevant to children's recreational activities in lakes or rivers. The EPA discussed exposure factors for
younger children (younger than six years old) in the Recreational AWQC/SA section 7.3.2. After the
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draft Recreational AWQC/SA was released for public comment, a larger data set for measured
incidental ingestion while recreating in a swimming pool was published in the peer reviewed literature
by Dufour et al. (2017). This data set includes more participants than the study the EPA used in the draft
for incidental ingestion estimation (Dufour et al. 2006) and provides information for younger children,
older children, and adults. Relevant exposure factors data for children younger than six years old are
limited to body weight values presented in the EPA's Exposure Factors Handbook (U.S. EPA 2011),
and the available peer reviewed studies of incidental ingestion which included children did not provide
data on incidental ingestion volume or duration specific to children younger than six years old (Schets et
al. 2011; Dufour et al. 2017).
Comment Summary: Hall and Associates expressed concern that the ingestion rate is over one-third of
the daily drinking water intake per unit body weight (as provided by the HAs), which seems excessive
for incidental ingestion.
Response:
The EPA uses a 90th percentile exposure scenario to derive drinking water health advisories consistent
with the EPA's 2000 Methodology for Deriving Ambient Water Quality Criteria for the Protection of
Human Health, with a drinking water consumption rate from the EPA's Exposure Factors Handbook
(U.S. EPA 2011, or most recently published version). The recreational exposure scenario used to
develop these criteria is based on peer reviewed studies conducted on incidental ingestion while
recreating and represents a 90th percentile exposure scenario for children aged six to 10 years of age.
The incidental ingestion rate has been revised from 0.33 L/day to 0.21 L/day based on the EPA's
analysis of a more robust data set provided by Dufour et al. (2017) and duration of exposure information
in the EPA's Exposure Factors Handbook (U.S. EPA 2011); this analysis is documented in Appendix E
of the Recreational AWQC/SA document.
Comment Summary: Some comments specifically addressed the key incidental ingestion study
identified as the source of the exposure duration. The Agricultural Retailers Association et al. stated that
the EPA should be transparent about the statistical weakness of the small sample size of Dufour et al.
(2006). Hall and Associates suggested that the EPA's scaling of the duration from "at least 45 minutes"
to one hour over estimates the duration. The Florida Department of Environmental Protection stated the
EPA should use the 90th percentile instead of the 97th percentile for the ingestion rate. The Agricultural
Retailers Association et al. asked the EPA to explain why the event duration from the 1997 Exposure
Factors Handbook (with a sample size of 15) was used over the 2011 Exposure Factors Handbook.
Response:
The EPA revised the document to use the most current peer reviewed science, including a recreational
water incidental ingestion study (Dufour et al. 2017) that was published after the draft Recreational
AWQC/SA document was released. See section 4.2.3.1 of the Recreational AWQC/SA for revisions and
clarifications of the EPA's calculation of the daily ingestion rate.
The EPA added additional language to discuss the duration data available and clarify how that data were
considered. See sections 4.2.3.1 (Incidental Ingestion) and 7.2 (Recreational Exposure Duration).
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Category 4.2 - Exposure Routes - Inclusion of fish/shellfish ingestion
Comments Summary: Several commenters focused on the route of exposure to cyanotoxins through
ingestion of fish and shellfish.
The Florida Department of Environmental Protection asked why the document did not include
information about the occurrence of cyanotoxins in fish and shellfish. They also asked whether the EPA
examined differences in exposure from marine, estuarine, and fresh fish. The Florida Department of
Environmental Protection asked if there was an effort made to determine if there were additional studies
characterizing sources of microcystins and cylindrospermopsin that became available after the
publication of the health effects documents and prior to the publication of the draft. This commenter also
requested that the EPA provide documentation regarding the literature search for other sources of
microcystins and cylindrospermopsin.
The Florida Department of Environmental Protection discussed the various modes of cyanotoxin
transmission through ingestion, specifically that the cooking of shellfish can cause the transmission of
high concentrations of toxins from organs to edible tissues. Furthermore, the commenter discussed
aquaculture ponds, which are a potentially significant source of cyanotoxins due to their proneness for
cyanobacteria blooms. They recommended that these sources of cyanotoxins should be considered when
characterizing overall exposure and determining the relative source contribution (RSC) in the derivation
of the criteria.
The New Jersey Department of Environmental Protection recommended that the EPA continue research
about exposure to toxins through ingestion of fish and shellfish in order to fill knowledge gaps and
provide better guidance for the consuming of recreationally caught fish and harvested oysters and
mussels. North Carolina Conservation Network et al. noted that shellfish are not currently tested for
cyanobacteria or their toxins. They recommended that the EPA weigh consumption of contaminated
shellfish as an exposure pathway in setting the human health criteria.
Response:
The EPA acknowledges that fish and shellfish are potential sources of cyanotoxins. The EPA has
developed recreational criteria, not human health criteria (which consider drinking water and fish
consumption). Consistent with the development of the 2012 RWQC, the EPA reconsidered application
of an RSC and did not address fish consumption at this time. Please refer to the category 7.2 for
comments regarding the RSC. The criteria focus on the short-term recreational exposure experienced by
people engaged in primary contact recreation. Additional language was added to the document to
emphasize the potential for exposure to the cyanotoxins from fish and shellfish consumption and to
discuss the occurrence of microcystins and cylindrospermopsin in other matrices (Recreational
AWQC/SA sections 3.2.4 and 7.6).
Category 4.3 - Exposure Routes - Relationship to secondary contact
Comments Summary: The Kentucky Division of Water stressed the necessity for the EPA to recognize
and provide guidance for tiered levels of exposure to toxins based on varied uses of water. The
recommended values are based upon protecting primary contact recreation, which neglect secondary
contact recreation.
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Response:
The Recreational AWQC/SA apply to ambient waters designated for primary contact recreation.
The EPA recognizes that there is the potential for exposure to the toxins via secondary contact recreation
(e.g., falling into the water from a boat, inhalation of aerosolized cells and toxins, dermal contact with
cells and toxins via fishing and boating). The EPA determined that using a primary contact recreation
scenario (swimming) for exposure as the basis for the criteria is protective of other aquatic activities
including those related to secondary contact recreation (see section 4.2.3 of the Recreational
AWQC/SA).
Effects Characterization (section 7 in the Recreational AWQC/SA) describes the potential relative risks
of adverse human health effects for inhalation and dermal exposure to microcystins and
cylindrospermopsin compared to the oral ingestion route. However, specific toxicity information for
these two routes are currently unavailable. This section also describes the potential risks from contact
with the cyanobacterial cells, where published data demonstrate that inhalation and dermal exposure can
be important to consider compared to exposure to the toxins.
Category 4.4 - Exposure Routes - Characterization of dermal and inhalation exposure
Comments Summary: Commenters expressed concerns regarding the EPA's characterization of dermal
and inhalation exposure of cyanotoxins. Four commenters (State of Wyoming Department of
Environmental Quality, Virginia Department of Environmental Quality and Department of Health,
Massachusetts Department of Public Health and Massachusetts Department of Environmental
Protection, and Mississippi River Collaborative) stated that there was insufficient evidence to support
the conclusions drawn by the EPA. The State of Wyoming Department of Environmental Quality
suggested removing descriptors of dermal absorption until sufficient evidence is available. They were
also concerned with the assumption that inhalation and ingestion pathways are directly comparable,
since persistence and toxicity in the respiratory tract are likely to differ from the gastrointestinal tract.
The Virginia Department of Environmental Quality and Department of Health suggested that the EPA
should not base their analysis on limited data, but instead support the need for further research to better
understand the extent of dermal exposure. The Massachusetts Department of Public Health and
Massachusetts Department of Environmental Protection stated that greater clarification was needed to
apply short-term exposure studies to situations involving long-term chronic exposure via inhalation.
The Virginia Department of Environmental Quality and Department of Health also voiced concerns
regarding the tables, formulas, and calculations in sections 7.5.1.1 and 7.5.1.2 of the draft document.
They pointed out that the ratios given in Table 7-5, Comparison of Recreational Exposure Ingested Dose
to Inhaled Dose of Microcystin, could not be reproduced, and suggested it would be more helpful to
demonstrate with an example calculation. Furthermore, they stated that Table 7-6, Comparison of
Recreational Exposure Ingested Dose to Dermal Absorbed Dose of Microcystins, required clarification.
They stated it was unclear if the ingested dose applied to children or adults, and that the lack of unit
conversion values made it difficult to reproduce the calculations.
Response:
The EPA added language to the Problem Formulation (section 4) and Effects Characterization (section
7) sections of the Recreational AWQC/SA document to clarify that the EPA is not assessing risks from
inhalation or dermal exposure to microcystins or cylindrospermopsin because there is not sufficient
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information to quantify the risks. The EPA did not calculate a risk value, but provided a comparative
characterization of potential exposures (Recreational AWQC/SA section 7.4).
The exposure scenario the EPA evaluated was limited to short-term recreational exposures. The EPA did
not evaluate a long-term or chronic exposure via ingestion, inhalation, or dermal exposure, therefore it
cannot make any conclusions about long-term recreational exposures.
The EPA identified typographical errors in Table 7-5 of the draft AWQC document that showed the
comparison of recreational exposure ingested dose to inhaled dose of microcystins. The calculated ratios
were correct, but certain input parameters were incorrectly shown. The EPA revised the Recreational
AWQC/SA document to fix the errors.
Category 5 - Receptors
Category 5.1 - Receptors - Consideration of multiple lifestages
Comments Summary: Three commenters (State of Wisconsin Department of Natural Resources, North
Carolina Conservation Network, Clean Water Action/Clean Water Fund) agreed with the use of the
child as the appropriate receptor. The Ohio Environmental Protection Agency stated that they use "a
tiered advisory approach: a recreational advisory for sensitive receptors, including children, and an
elevated advisory for all receptors."
The Mississippi River Collaborative did not agree that the EPA's approach was adequately protective of
children. This commenter suggested that the EPA should use a body weight for one- to five-year-old
children as soon as appropriate ingestion data are available for this age group; this commenter stated that
the body weight for five- to 11-year-old children results in a higher, less protective value. This
commenter also cited a link that demonstrates that body weights differ between age groups.
The Mississippi River Collaborative provided an analysis of the derivation of each parameter in the
equation used to calculate the draft guidelines. The commenter (Mississippi River Collaborative) stated
that their analysis shows that the EPA's selected values for body weight and exposure duration which
are not sufficiently protective of children, and the commenter requested modification in advance of the
publication of the criteria.
The North Carolina, Upper Neuse River Basin Association suggested that numeric criteria be added that
explicitly note the applicability of the rule to children ages five to 11 years old and that additional age-
relevant tables should be added to the document.
Two commenters (North Carolina, Lower Neuse River Basin Association, North Carolina, Neuse River
Compliance Association) stated that while children are the lifestage most vulnerable to the effects of
cyanobacterial toxin, no reports of adverse health effects in children have been identified in their state.
Response:
The body weight parameter value selected is based on the information presented in the EPA's 2011
Exposure Factors Handbook. The body weight for children aged six to 10 years represents the weighted
average for the children represented by each year in that age group.
The URL link cited by the commenter contains a table of height and weights for males and females from
infancy to 20 years. It is the EPA's practice to use peer reviewed data whenever available. The source of
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this information is not given, nor are the number of people in each category, which inhibits the
calculation of a weighted average for boys and girls aged six to 11 years.
The qualitative comparison discussed in the Effects Characterization suggests that children younger than
six years old may not contribute significantly to the ingestion distribution. Unfortunately, quantitative
data for the younger children are not available, so it is not possible to definitively test the commenter's
assumption that children under six years may be more highly exposed in a recreational scenario.
The EPA evaluated exposure of multiple lifestages and concluded that children six to 10 years have the
highest exposures (see Recreational AWQC/SA sections 4.2.3.1 and 7.3). Quantitative data for children
younger than six years old are not available.
Category 5.2 - Receptors - Protection for companion animals and livestock
Comments Summary: Two commenters (North Carolina, Lower Neuse River Basin Association, North
Carolina, Neuse River Compliance Association) stated that dogs are vulnerable to cyanotoxins and that
deaths of dogs associated with cyanotoxins have been reported. The North Carolina Conservation
Network suggested that the EPA should either consider dogs when finalizing the criteria or make
explicit note of this gap.
The New York State Department of Environmental Conservation and Department of Health suggested
that the EPA should include recommendations for the public and their animals to avoid algal blooms.
The Mississippi River Collaborative suggested that the EPA should derive quantitative guidelines for
other mammals, such as dogs, livestock, and wildlife. The California Office of Environmental Health
Hazard Assessment noted that their state has already developed health-based surface water
concentrations for microcystins and cylindrospermopsin to protect pets and livestock.
The Karuk Tribe agreed with the EPA's analyses, noting their consistency with current local cyanotoxin
guidelines to protect human and animal health.
Response:
The EPA included additional information on pets and livestock in the Recreational AWQC/SA section
7.8. Information on public communication, including HAB risks to pet exposures, was included in the
recently published implementation support materials Recreational Water Communication Toolbox for
Cyanobacterial Blooms (U.S. EPA 2017a). The toolbox provides examples of best practices, including
ways to prevent pet and animal exposure.
Category 5.3 - Receptors - Other comments
Comments Summary: The Mississippi River Collaborative stated that the "draft guidelines may not
adequately protect sensitive groups, such as immunocompromised people, people with liver or liver and
kidney disease, people with nervous system disorders, pregnant women, nursing mothers, and the
elderly" and that the federal agencies involved in cyanotoxin-related resource management (e.g., the
EPA, Centers for Disease Control and Prevention, National Institutes of Health, and National Institute of
Environmental Health Sciences) should fund studies that will enable guidelines to be written to protect
sensitive groups from adverse impacts of these toxins.
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Response:
Recreational exposure data is limited for the sensitive subgroups identified by the commenter. The
recommended values for the toxins are derived using exposure factors for the subgroup with the highest
exposure (i.e., children approximately six to 11 years-old). Sensitive populations such as those
mentioned in the comment are taken into account in the derivation of the toxicity values for microcystins
and cylindrospermopsin. Specifically, an uncertainty factor is applied to account for variability in the
human population. No information was available to characterize inter-individual and age-related
variability in the toxicokinetics or toxicodynamics among humans.
Category 6 - Endpoints
Category 6.1 - Endpoints - Consideration of inflammatory and other endpoints
Comments Summary: Three commenters (State of Wisconsin Department of Natural Resources, State
of Utah Department of Environmental Quality, Division of Water Quality, and Association of Clean
Water Administrators) stated that the proposed criteria do not protect the public from the more
immediate inflammatory responses from acute exposures to cyanotoxins, sensitization of exposure, and
repeated exposure events.
The Iowa Department of Natural Resources stated that the RfDs for microcystins and
cylindrospermopsin, based upon liver or kidney impacts, should not be used in determining recreational
criteria/guidelines, and that an acute endpoint such as inflammatory response is the relevant endpoint.
The Kentucky Division of Water stated that the EPA should continue to provide guidance and ultimately
develop recommended advisory values that are protective of both the primary and secondary contact
recreation uses for all routes of exposure, and for endpoints other than organ toxicity (dermal symptoms,
eye/ear irritation, fever, gastrointestinal illness, and respiratory symptoms).
Three additional commenters (New York State Department of Environmental Conservation and
Department of Health, Ohio Environmental Protection Agency, North Carolina Conservation Network)
stated that evaluating toxins alone is inadequate for protecting recreators, noting that there is a link
between recreational exposure to cyanobacterial cells and acute health effects such as allergic, dermal,
eye or ear irritation, gastrointestinal, inflammatory, and respiratory effects. One of these commenters
(North Carolina Conservation Network et al.) suggested the inclusion of a threshold cell concentration
criteria to be protective of inflammatory and allergic reactions.
Response:
Acute endpoints such as inflammatory effects from clinical, epidemiological, and outbreak studies were
not selected as the primary endpoint of concern due to data uncertainties. The EPA did provide a
summary of available information on effects resulting from exposure to cyanobacterial cells. See
Recreational AWQC/SA section 7.5.1 (Health Effects Associated with Cyanobacterial Cells and
Uncertainties) and Appendix D (Review of the State of the Science on Cyanobacterial Cell Health
Effects) that summarize the health studies reviewed for this effort and the EPA's conclusions regarding
cyanobacterial cells and inflammatory effects. The EPA agrees that further research is needed to
improve understanding of the toxicity associated with non-oral routes of exposure, with the
inflammatory responses such as dermal symptoms, eye/ear irritation, fever, gastrointestinal illness,
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respiratory symptoms, chronic health effects, and cancer. The EPA will evaluate new research as it
becomes available.
The EPA does not agree that adverse effects on liver or kidney that may result from incidental ingestion
during primary contact recreational activities should not be considered in establishing recreational
criteria or swimming advisories. The Recreational AWQC/SA has been revised to include two case
reports of liver toxicity reported in humans following acute recreational exposure.
Category 6.2 - Endpoints - Other
Comments Summary: The Mississippi River Collaborative agreed with the EPA's conclusion that
there are insufficient data to determine whether microcystins or cylindrospermopsin are carcinogenic.
Both the Mississippi River Collaborative and Kentucky Division of Water encouraged a coordinated
federal research effort to investigate the carcinogenicity of cyanotoxins. Both commenters also noted
that if sufficient carcinogenicity information is generated, the EPA would need to provide updated
recommended values to account for carcinogenicity.
Response:
Applying the U.S. EPA (2005) Guidelines for Carcinogen Risk Assessment, the Agency concluded that
there is inadequate information to assess carcinogenic potential of microcystins and cylindrospermopsin.
The few available epidemiological studies on microcystins are limited by their study design, poor
measures of exposure, potential co-exposure to other contaminants, and the lack of control for
confounding factors. There are no epidemiological studies evaluating the carcinogenic potential of
cylindrospermopsin. No long-term animal studies were available to evaluate dose-response for the
tumorigenicity of either cyanotoxin. The EPA identified key research gaps in its HESDs (HESDs section
8.0) for microcystins and cylindrospermopsin. Included on these lists are the carcinogenic potential of
microcystin-LR and cylindrospermopsin. The EPA acknowledges that updated analyses would be
needed if new studies results indicated carcinogenic potential of either of these cyanotoxins.
Category 7 - Analysis
Category 7.1 - Analysis - Deviations from 2000 AWQC Methodology
Comments Summary: Two commenters (Iowa Department of Natural Resources, Iowa Farm Bureau
Federation) stated that the EPA did not follow its 2000 AWQC Methodology for Deriving Ambient
Water Quality Criteria for the Protection of Human Health (2000 AWQC Methodology). The Iowa
Department of Natural Resources quoted an excerpt in the 2000 AWQC methodology, which the
commenter interpreted to say that the EPA believes that average amount of incidental water ingestion
while recreating is negligible and will not have any impact on the chemical criteria values representative
of both drinking water and fish ingestion. Therefore, the commenter argued it is unnecessary to establish
human health AWQC based on incidental ingestion of ambient water during recreational activities. The
Iowa Farm Bureau Federation stated that the EPA deviated from the 2000 AWQC Methodology by
extrapolating and mixing together chronic exposure health effects with short-term acute ingestion
exposures.
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Response:
The 2000 AWQC Methodology default approach is to use drinking water ingestion rates to estimate
ingestion exposure. In that guidance, the EPA explains that incidental ingestion is not added to the
drinking water rate because it is negligible compared to drinking water ingestion [emphasis added]. The
EPA used available reliable data on incidental ingestion while recreating to derive recreational
AWQC/SA for the cyanotoxins. Using the drinking water consumption rate would not be representative
of a recreational exposure scenario.
In response to the comment regarding mixing chronic exposure health effects with short-term acute
ingestion exposures, please refer to the EPA's responses in section 7.3 (Analysis - Derivation of the
RfDs for Microcystins and Cylindrospermopsin), which clarify that the EPA derived a short-term RfDs,
the justification and support for the selection of the critical toxicity studies.
Category 7.2 - Analysis - Relative Source Contribution
Comments Summary: Several commenters (Florida Department of Environmental Protection, Hall and
Associates, State of Utah Department of Environmental Quality Division of Water Quality, Texas
Commission on Environmental Quality, Mississippi River Collaborative) requested clarification on the
assumption that the RSC value is equal to 0.8 and additional supporting documentation in order to prove
its scientific defensibility. The Florida Department of Environmental Protection found the reference to
the decision tree from the 2000 methodology to be inadequate and the RSC "section is lacking the
needed details to assess whether or not a RSC of 0.80 is appropriate for these proposed criteria."
The Virginia Department of Environmental Quality and Virginia Department of Health stated that "in all
likelihood the RSC value of 80% is adequate," however, they asked the EPA for further details for the
rationale for the use of 80 percent. They also requested that the EPA add to the draft document a
demonstration that this RSC value is adequate and not arbitrary, including a calculation that illustrates
that "other exposure modes are/are not insignificant and text describing the potential/non-potential for
additive exposure effects." In addition, "if further research is needed or would be helpful to the
understanding, clearly articulating the need in the document would be preferred."
The California Office of Environmental Health Hazard Assessment "agrees that there are multiple
sources of exposure and therefore supports the use of an RSC of 80 percent." The Mississippi River
Collaborative stated that "the RSC used by the EPA in deriving the draft guidelines for both
[microcystins] and [cylindrospermopsin], 0.8, is the highest allowed value. Rather than providing a
"margin of safety" as asserted by the EPA, its use biased the analysis to yield higher, less protective
draft guidelines. The RSC should be re-evaluated."
The New Jersey Department of Environmental Protection pointed out that the EPA's 2000 AWQC
guidance methodology discusses the use of an RSC in drinking water exposure assessment, but not
recreational criteria exposure assessment. The draft criteria appear to represent the first use of RSCs for
recreational criteria exposure assessment. This commenter asked the EPA to acknowledge that this
approach represents an extension to their previous methodology (2000 AWQC guidance) and provide
further discussion in the draft document.
The Texas Commission on Environmental Quality asked the EPA to change the RSC value. Stating that
"the use of an RSC of anything less than one in the draft criteria cannot be justified because there is not
information to suggest that there is any significant exposure to microcystins and/or cylindrospermopsin
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via other routes of exposure, such as dermal exposure, inhalation, ingestion of fish/shellfish, or drinking
water."
Several commenters (Virginia Department of Environmental Quality, Florida Department of
Environmental Protection, California Office of Environmental Health Hazard Assessment, Texas
Commission on Environmental Quality, Hall and Associates, Agricultural Retailers Association et al.,
Mississippi River Collaborative) pointed out routes of exposure associated with recreating in addition to
incidental ingestion. Several commenters (Agricultural Retailers Association et al., California Office of
Environmental Health Hazard Assessment, Florida Department of Environmental Protection, Texas
Commission on Environmental Quality, State of Utah Department of Environmental Quality Division of
Water Quality, Mississippi River Collaborative) questioned why exposure to cyanotoxins via fish and
shellfish were not discussed in the context of the derivation of the RSC. Two commenters (Florida
Department of Environmental Protection, Hall and Associates) noted that the EPA's exclusion of fish
and shellfish consumption as part of the RSC in the draft criteria is a deviation from the 2000 AWQC
Methodology and previous assessments.
Response:
The EPA decided not to apply the RSC term as explained in the Recreational AWQC/SA section 4.2.4.
Category 7.3 - Analysis - Derivation of the reference doses (RfDs) for microcystins and
cylindrospermopsin
General comments
Comments Summary: Two commenters (North Carolina Conservation Network, Clean Water
Action/Clean Water Fund) agreed with the values the EPA presented for both microcystins and
cylindrospermopsin. Another commenter (University of North Carolina at Chapel Hill's Institute of
Marine Sciences) fully supported the endpoints of liver and kidney toxicity used to derive the criteria.
Response:
Thank you for your comments.
Adequacy of database
Comments Summary: Three commenters (Hall and Associates, National Association of Clean Water
Agencies, Agricultural Retailers Association et al., Virginia Association of Municipal Wastewater
Agencies) stated that there are limited human or animal studies that provide evidence to support the need
for the proposed criteria. They stated that few of the available human studies reported adverse health
effects from exposure to cyanotoxins, and the only effects were noted were at doses higher than the
limits proposed by the EPA. The Agricultural Retailers Association et al. stated that criteria should not
be recommended until adequate, peer reviewed, scientific information is provided. They also noted that
it appears that no relevant health effects studies have been published since the publication of the HAs
based on the citations in the draft document. The Virginia Association of Municipal Wastewater
Agencies mentioned uncertainties associated with the available study data and commented that the
available information is insufficient for the promulgation of 304(a) criteria.
One commenter (National Association of Clean Water Agencies) also stated concerns over the limited
number of peer reviewed studies that the EPA used to derive the swimming advisories and recreational
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AWQC, and stated that these values "do not appear to be based on any dose-response data from ambient
exposures."
Response:
The recreational criteria development relied upon the EPA's HESDs released by the Office of Water
in 2015. In developing these HESDs, the EPA conducted a comprehensive search of the literature for
information on mechanisms of toxicity; acute, short-term, subchronic and chronic toxicity and cancer
in humans and animals; and toxicokinetics.
For microcystins, oral and intraperitoneal (i.p.) acute and short-term studies in mice and rats, and
subchronic studies in mice are available. Chronic data are also available for microcystins, however,
they are limited by the lack of quantitative data provided. There are limited neurotoxicity studies and
several i.p. reproductive and developmental toxicity studies (there is no multi-generation reproductive
toxicity study). For cylindrospermopsin the database for studies in laboratory animals includes oral
exposure acute, short-term and subchronic studies, but many of them lacked a comprehensive
evaluation of a wide spectrum of effects. The database lacks chronic toxicity and multi-generation
reproductive and developmental toxicity studies using the oral route of exposure.
Epidemiological studies related to outbreaks, clinical studies, and cases studies evaluating human
health effects due to exposure to microcystins and cylindrospermopsin are described in detail in the
EPA's HESDs (see section 6.1 of U.S. EPA 2015g and U.S. EPA 2015c). While the human data on
the oral toxicity of microcystins and cylindrospermopsin are limited and confounded by potential co-
exposure to other contaminants; a lack of quantitative information; and other confounding factors,
these studies do provide support for the kidney and liver as targets of cyanotoxin-induced toxicity
observed in the animal studies.
EPA's HESD and HA documents describe the selection of the critical study and effect in detail and
provide the rationale for selection of the critical studies and endpoints for derivation of the short-term
oral reference doses (see section 3.1 in the HAs and Chapter 7 in the HESDs). The EPA conducted an
extensive independent external peer review of its HESDs that included charge questions requesting
comment on whether there were sufficient data to derive reference doses for microcystins and
cylindrospermopsin. The peer reviewers supported the development of reference values for these
cyanotoxins.
The EPA conducted supplemental literature searches in September 2015 to identify additional data on
human health effects related to exposures to cyanotoxins and cyanobacterial cells for consideration in
developing the recreational values. Studies of human studies to cyanobacterial cells have been
included in Appendix D.1.3 of the Recreational AWQC/SA document. The EPA did not identify any
new toxicity studies for microcystins or cylindrospermopsin suitable for RfD derivation.
The severity of the endpoints of concern for microcystins and cylindrospermopsin precludes
conducting a study that purposefully exposes children and adults to increasing levels of toxin-
contaminated water in order to find the lowest observable adverse level for the purpose of deriving
recreational AWQC/SA. Use of the animal model allows for evaluation of a wide range of doses to
inform the adverse effect level. The EPA's recommendations represent a concentration at which one
would not expect to have adverse health effects occur from short-term exposure to these toxins.
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Duration of critical study for derivation of the RfD for microcvstins
Comments Summary: The Agricultural Retailers Association et al. noted that the criteria are based on
single animal studies with ingestion of drinking water for 28-77 days which is not consistent with risks
associated with a single day, or even several days, of recreational exposure. The Iowa Department of
Natural Resources considers swimming and recreational exposures to be short-term or acute, not a
chronic exposure scenario in which they stated that the reference dose is normally used.
Response:
Section 4.2.2 of the Recreational AWQC/SA document describes that short-term RfDs were used in the
criteria derivation. For microcystins, a short-term RfD was developed using a study in male rats exposed
to microcystin-LR for 28 days via drinking water (Heinze, 1999). For cylindrospermopsin, an 11-week
study by Humpage and Falconer (2002, 2003) was selected as the critical study for development of the
RfD. The available short-term studies available for cylindrospermopsin (Shaw et al., 2001; Reisner et
al., 2004), were evaluated and are considered supportive of the critical study, however the EPA
concluded that they were not suitable for quantification based on limitations including the use of extract,
lack of adequate numbers of animals, monitored endpoints, the limited number of doses tested and
endpoints monitored. As described in the EPA's HESDs, similar effects were observed at a similar dose
after three weeks comparable to the effects seen in the Humpage and Falconer (2002, 2003) study at a
slightly lower dose after 11 weeks. The Humpage and Falconer (2002, 2003) study was determined to be
the most appropriate for the quantitative assessment because the LOAEL at 11 weeks would be
protective for the effects seen at three-weeks in the shorter duration study. For these reasons, this RfD
was deemed suitable for development of the short-term drinking water health advisory and for use in
recreational exposure scenarios. Peer reviewers agreed with this conclusion.
The EPA assumes that people who live close to a swimming area will most likely recreate frequently
and those that travel to swimming areas typically spend time recreating over a week or weekend. Thus,
the EPA does not believe that swimmers will only be exposed acutely (i.e., one day) and that kidney or
liver effects are not possible after such a short exposure.
Comment Summary: One commenter (Hall and Associates) stated that the reference doses were overly
conservative. This commenter stated that the Heinze (1999) study only evaluated effects at the end of
the 28-day exposure period, and no effects were evaluated at an interim time period.
Response:
The methodology for deriving an RfD (including application of uncertainty factors) and the algorithm
for deriving AWQC for noncarcinogens is presented in the EPA's 2002 A Review of the Reference Dose
and Reference Concentration Processes (U.S. EPA 2002) and the 2000 Methodology for Deriving
Ambient Water Quality Criteria for the Protection of Human Health (U.S. EPA 2000), respectively. The
EPA's HESDs for both microcystins and cylindrospermopsin were subject to external peer review and
the reviewers supported the derivation of the RfDs for these cyanotoxins.
A short-term RfD for microcystins was developed using a study in male rats exposed to microcystin-LR
for 28 days via drinking water. Because the study lacked interim effects data, it is not known when
during the 28-day study these effects were originally manifest. The human data from the dialysis clinic
(Carmichael et al. 2001; Jochimsen et al. 1998; Soares et al. 2005) and the Australian study of an acute
2-hour exposure to water impacted by a bloom (Giannuzzi et al. 2011) clearly demonstrate that a brief
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exposure duration can initiate the sequence of hepatic events that are terminally manifest as signs and
symptoms for liver damage in humans.
Comments Summary: One commenter (Hall and Associates) argued that the lowest-observed-adverse-
effect-level (LOAEL) should be multiplied by the 28-day exposure duration. Another commenter (Water
and Environmental Testing, Inc. and South Valley Water Reclamation Facility) noted that the reference
dose units should be changed from [j,g/kg/day to [j,g/L for a continuous 28-day exposure period.
Response:
Total dose across the study duration is not the appropriate point of departure for the quantification of
risk. The Guzman and Solter (2002) i.p. injection study suggests the tissue damage that progresses to
liver cell necrosis can occur within the first days of dosing arguing against summing the doses for
quantification. In this study, there were signs of liver damage as early as two hours after an
intraperitoneal injection of 45 |ig/kg microcystin-LR and apoptosis was apparent in BALB/C mice given
a the same i.p. dose for two days and sacrificed 24 hours after the second dose. These results clearly
demonstrate early effects on the liver with very short-term doses roughly comparable to the doses in the
Heinze (1999) longer term study. The dosing in Heinze (1999) was slightly higher than that in Guzman
and Solter (2002) but had less direct delivery to the liver.
The Heinze (1999) study did not perform interim sacrifices to evaluate effects prior to the conclusion of
the study (28 days). Given the lack of these data, the precise day the tissue damage that lead to the
effects at sacrifice began is not known.
In the case of cylindrospermopsin, the available short-term study by Reisner et al. (2004) found an
impact of on urine excretion rate and kidney weight at three weeks and is supportive of the renal effects
seen in the critical study at 11 weeks.
Dose range of the critical study for derivation of the RfD for microcvstins
Comments Summary: Four commenters (Florida Department of Environmental Protection, New Jersey
Department of Environmental Protection, Hampton Roads Sanitation District, Mississippi River
Collaborative) thought that the Heinze (1999) study had an inadequate dose range, expressing concern
that this study did not find a no-observed-adverse-effect-level (NOAEL). Mississippi River
Collaborative also stated that critical study (Heinze 1999) LOAEL was too high because the lowest
microcystin-LR concentration tested (50 |ig/kg/day) showed major effects—increased liver weight,
slight to moderate liver lesions with hemorrhages, and increased serum enzyme levels.
Response:
Acute, short-term, and subchronic animal studies were identified and described in the EPA's HESD
for microcystins (U.S. EPA 2015c). Of these studies, three oral exposures studies were identified as
possible studies for the development of the short-term guidance value: Heinze (1999), a 28-day
drinking water rat study, Fawell et al. (1999), a 90-day gavage study in mice, and Chen et al. (2011),
a three to six month drinking water study using mice. After evaluation of Chen et al. (2011), the EPA
determined that because of limitations in study design, report, and methods used, this study was not
adequate for determining the point of departure for the derivation of the RfD for microcystins. Peer
reviewers agreed with this conclusion.
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The primary health effect following exposure to microcystin-LR in animal studies is liver damage.
Multiple studies (short-term and subchronic) have reported effects on the liver including altered liver
weight and enzyme levels, necrosis, and inflammation and hepatocyte vacuolization. Heinze (1999) was
selected as the critical study because it used a broader dose range than other studies considered, used the
most relevant route of administration, histopathological evaluation of endpoints, and observed dose-
related liver effects at low doses. The findings of the critical study are supported by the Guzman and
Solter (1999, 2002) and Fawell et al. (1999) studies. Although these studies used different species and
strains of laboratory animal and differed in dose, duration, route of exposure, and description of liver
histopathology, they all reported effects to the liver in the 30 to 50 (J,g/kg dose range. The selection of
the critical study and description of supporting studies, including an explanation of the uncertainty factor
the EPA applied to adjust the LOAEL to a NOAEL, is presented in the Agency's HESD for
microcystins section 7.4.1. Peer reviewers agreed with this conclusion. Research gaps associated with
the microcystin database are presented in section 8.0 of the EPA's HESD.
Comments Summary: The Virginia Association of Municipal Wastewater Agencies claimed that the
microcystins reference dose is based on a study (Heinze 1999) that observed large percent differences
between two microcystin exposure treatments, leading to high uncertainty regarding whether the RfD is
accurate. They expressed a similar concern about the study used to derive the RfD for
cylindrospermopsin (Humpage and Falconer 2002).
Response:
The EPA disagrees with the claim that there was a large difference in the response to the two doses in
the Heinze (1999) study. Tables 6-2 and 6-3 of the EPA's HESD demonstrate that tripling the dose
shifted the tissue damage from four animals with mild necrosis and six with moderate necrosis at the
low dose to six with moderate necrosis, three with severe necrosis, and one with moderate tissue
hemorrhage for the high dose. That is not a dramatic change. The greater concern is the fact that all
animals exhibited necrosis of the liver at both doses. The differences in the enzymes indicative of liver
damage are also not dramatically difference at the high dose from those at the low dose.
Rodent strain used in critical study for derivation of the RfD for microcystins
Comment Summary: American Water Works Association commented that the critical study by Heinze
et al. (1999) used a rat breed that the commenter suggested might be more susceptible to liver
impairments than other rodent strains typically used in risk assessments.
Response:
The primary health effect following exposure to microcystin-LR in animal studies is liver damage.
Multiple studies (short-term and subchronic) have reported effects on the liver including altered liver
weight and enzyme levels, necrosis, and inflammation and hepatocyte vacuolization.
As described in the EPA's HESD for microcystins (U.S. EPA 2015c), the available studies reported
effects to the liver in the 30 to 50 (J,g/kg dose range, consistent with the hypothesis that the risk for liver
damage is proportional to the exposure route and unrelated to the rats' breed. Neither of the two co-
critical studies used the same strain of rat as Heinze et al. (1999), however, Sprague Dawley rats were
used by Guzman and Solter (1999). The EPA concluded, based on the requirement for transport, that the
Fawell et al. (1999) mice were less sensitive to the microcystin due to less liver exposure resulting from
the once per day bolus dose delivery method. Although a NOAEL was not identified in Heinze (1999),
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and these studies used different species and strains of laboratory animal and differed in dose, duration,
and route of exposure, the changes in liver histopathology were similar and the exhibited LOAEL's for
liver damage increased with route of dose delivery as predicted (i.p. infusion > drinking water >
gavage). Evidence from these and other studies (Ito et al. 1997; Guzman and Solter 1999) suggest that
the NOAEL is not very far below the lowest dose used by Heinze (1999). The fact that three different
strains of laboratory animal had similar hepatic responses after allowing exposure route does not support
the claim that the Heinze (1999) strain of rat is more sensitive than the others evaluated.
Measure of effect in critical study for derivation of the RfD for microcvstins
Comment Summary: American Waterworks Association commented on the EPA's "use of a
secondary measure of toxicity without demonstrated linkages to direct measures of toxicological effect."
They noted that this approach was different from other state and government agencies' approaches taken
for cyanotoxins.
Response:
Most of the toxicity information on the adverse effects of microcystins is from animal studies. However,
data from the episode in a dialysis clinic in Caruaru, Brazil where microcystins were not removed by
treatment of dialysis water, identify liver effects: 100 of the affected patients developed acute liver
failure and, of these, 76 died. At a similar incident in Brazil patients had markers of hepatic cellular
injury including cholestasis and elevated levels of aspartate aminotransferase (AST), alanine
transaminase (ALT), bilirubin, alkaline phosphatase (ALP), and gamma glutamyl transferase (GGT) in
serum. These data support the selection of liver damage as the measure of toxicity.
Use of microcvstin-LR as a surrogate for all microcvstins
Comments Summary: North Carolina, Upper Neuse River Basin Association suggested clarifying the
comprehensive magnitude of uncertainty and applying the criteria solely to microcystin-LR. Another
commenter, American Water Works Association, expressed concern that the derivation of a level of
concern for all microcystins based exclusively on microcystin-LR differed from approaches taken by
other state and international governments. North Carolina, Upper Neuse River Basin Association
recommended the EPA consider the use of microcystin-LR toxicity equivalency values for other
microcystins, similar to dioxin congener approaches.
Response:
Section 4.1 of the EPA's HA for microcystins (U.S. EPA 2015e) describes the basis for using
microcystin-LR as a surrogate for total microcystins. The data that support the quantitative assessment
of risk are all based on studies of microcystin-LR. Little is known about the other microcystin
congeners, and the data that exist are not consistent regarding relative potency. The EPA's HESD for
microcystins (U.S. EPA 2015c) notes that researchers have explored toxicity equivalency factors for
microcystin congeners (Wolf and Frank 2002). However, these calculations were based on
intraperitoneal LD50 values, which have questionable application to evaluating risk from oral or dermal
exposure given that differences in lipophilicity and polarity of the congeners may lead to variable
absorption by non-injection routes of exposure.
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Selection of critical study for derivation of the RfD for cylindrospermopsin
Comments Summary: Hampton Roads Sanitation District commented that the Humpage and Falconer
(2002) study was insufficient, adding that the biological significance of the endpoints considered in that
study was unclear.
Response:
For cylindrospermopsin, the 11-week study by Humpage and Falconer (2002, 2003) was selected as the
critical study for development of the RfD. Kidney toxicity was the critical effect chosen for the point of
departure. In both studies, Humpage and Falconer (2002, 2003) explained that although urine total
protein was significantly decreased at doses above 60 [j,g/kg/day, the kidney was the more sensitive
organ to this toxin and identified a NOAEL of 30 [j,g/kg/day.
The short-term studies available for cylindrospermopsin (Shaw et al. 2001; Reisner et al. 2004), were
evaluated and are considered supportive of the critical study, however the EPA concluded that they were
not suitable for quantification based on limitations including the use of extract, lack of adequate
numbers of animals and monitored endpoints, and limited number of doses tested. The EPA's HESD
and HA documents for cylindrospermopsin describe the selection of the critical study and effect in detail
and provides the rationale for applicability of the longer-term duration study.
Briefly, similar effects to those observed in the critical study were observed in a 21-day study in mice by
Reisner et al. (2004). Specifically, significant increases in hematocrit, acanthocytes (abnormal red blood
cells), and liver and testes weights effects at a 66 [j,g/kg/day dose and a duration-related nonsignificant
increase in and kidney weight were observed. This study was not selected for development of the 10-day
HA because this study used a single dose and observed the biochemical and hematology effects at
weekly intervals. The kidney and red blood cell effects at that dose after three-weeks were comparable
to the effects seen in the Humpage and Falconer (2002, 2003) study at a slightly lower 60 mg/kg/day
dose after 11 weeks. The red blood cell effects in Reisner et al. (2004) were seen as early as the end of
the first week of dosing and were present in each of the three weekly blood samples collected. The
Humpage and Falconer (2002, 2003) study was determined to be the most appropriate for the
quantitative assessment because the LOAEL at 11 weeks would be protective for the effects seen at
earlier time points in the Reisner et al. (2004) study. Peer reviewers agreed with this conclusion.
Comment summary: The Virginia Association of Municipal Wastewater Agencies described concern
about high degree of uncertainty generated by the large effect differences between cylindrospermopsin
exposures in the critical study (Humpage and Falconer 2002).
Response:
The Humpage and Falconer (2002, 2003) study utilized four dose groups, adequate numbers of animals
per dose group and evaluated a variety of endpoints. Statistically significant, dose-related effects on the
kidney, liver and serum chemistry were observed. The kidney was the most sensitive target of toxicity.
The Humpage and Falconer (2002) data are supported by other studies (e.g., Reisner et al., 2004) where
results showed increased kidney weights and hematological effects (acanthocytes) after a three-week
exposure. Although this study has the limitation of a control with a single dose, it had the advantage of
following the response to dose at weekly interval for those endpoints that did not require sacrifice for
detection (e.g., urinary excretion rate and acanthocytes) rather than kidney weight.
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Uncertainty factors
Comments Summary: Five commenters did not think the uncertainty factors utilized were appropriate.
Mississippi River Collaborative thought that the uncertainty factors for database uncertainty (UFd) and
LOAEL to NOAEL extrapolation (UFl) and were both too low for microcystins and
cylindrospermopsin, and that these values should be increased to 10. New Jersey Department of
Environmental Protection agreed that a UFd of three was too low for both microcystins and
cylindrospermopsin, and also recommended this value be increased to 10. California Office of
Environmental Health Hazard Assessment agreed that the UFl for microcystins was too low and should
be increased to 10. Hall and Associates noted that no uncertainty factor was used for extrapolating
subchronic to chronic exposure (UFs). American Water Works Association commented that the EPA's
approach to not reduce uncertainty factors when data is available related to mechanisms and modes of
action for microcystin-LR differed from state and international government approaches.
Response:
The database for microcystins includes limited human data, oral and i.p. acute and short-term studies in
mice and rats, and subchronic studies in mice. The database lacks a multi-generation reproductive
toxicity study. There are limited neurotoxicity studies and several i.p. reproductive and developmental
toxicity studies. The EPA considered the effects of microcystin on the male reproductive system and
sperm development following oral exposures as a potential critical effect. Based on the limitations in
study design, report and methods used by Chen et al. (2011), the EPA concluded, with peer reviewer
support, that the quantitative data on decreased sperm counts and sperm motility were not appropriate
for determining the point of departure for the derivation of the RfD for microcystins. The available
reproductive and developmental toxicity studies have limitations in methods and reporting that limit
their utility a measure of dose response for developmental/neurodevelopmental effects.
For cylindrospermopsin, the database includes limited human data and studies in laboratory animals
including oral exposure acute, short-term and subchronic studies. The database includes evaluation of
reproductive and developmental endpoint but lacks chronic toxicity and multi-generation reproductive
and developmental toxicity studies using the oral route of exposure. There is a lack of data on
neurological and immunological endpoints.
A database UF is warranted (i.e., a three) in situations where reproductive and developmental studies are
limited and it is difficult to assess their potential to affect the point of departure (POD), as is the case for
microcystins and cylindrospermopsin.
The EPA applied an uncertainty factor of three to account for the extrapolation from a LOAEL to a
NOAEL based on the evidence suggesting that the uptake of microcystins by tissues requires membrane
transporters. Heinze (1999) identified a LOAEL of 50 [j.g/kg/day based on increased liver weight, slight
to moderate liver lesions with hemorrhages, and increased enzyme levels. Guzman and Solter (1999)
used intraperitoneal implantation of osmotic pumps, a more direct delivery of dose to the liver, to
administered purified microcystin-LR to groups of three male rats. The pumps delivered zero, 16, 32, or
48 |ig/kg/day and identified a NOAEL of 16 [j,g/kg/day and a LOAEL of 32 [j,g/kg/day. Guzman and
Solter (1999) observed necrosis at doses of 32 and 48 [j,g/kg/day, but not at a dose of 16 [j,g/kg/day,
supporting for the critical effect and dose. Using three animals per dose group is a weakness of the
Guzman and Solter study. However, not finding evidence for necrotic or pre-necrotic hepatic damage in
the 16 |ig/kg/day dose group and the use of a slow osmotic pump mode of delivery that bypassed the
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need for intestinal transporters are its strengths. The EPA also evaluated Fawell et al. (1999), a gavage
study in mice that found liver effects at a higher dose (200 |ig/kg) than the LOAEL identified in Heinze
et al. (1999). Through considering the data from all three studies, the EPA believes that there is no
reason to believe that the less direct delivery from the intestines to the liver following oral exposures
through drinking water (as was used in Heinze 1999) would have a more than three-fold separation
between a NOAEL and LOAEL had there been one in the Heinze (1999) study. Therefore, the EPA
concluded that a three-fold NOAEL/LOAEL uncertainty factor for Heinze et al. (1999) is appropriate.
There was no uncertainty factor (UFs) applied to account for use of a less than chronic duration study
since the EPA developed the RfDs for short-term exposures. See the key study and uncertainty factor
descriptions in section 7.4 of the EPA's HESD for microcystins (U.S. EPA 2015c) for details.
Comments Summary: A commenter (North Carolina, Upper Neuse River Basin Association) stated
that the document did not clearly highlight the magnitude of the comprehensive uncertainty in deriving
the criteria.
Response:
The commenter mentions a number of factors related to the database for microcystins and
cylindrospermopsin that are illustrative to the uncertainties in the assessment. Human studies and case
reports are limited by potential co-exposure to other pathogens, cyanotoxins, and microorganisms; by
the lack of quantitative information (microcystin concentrations); and by the failure to control for
confounding factors. However, case studies of recreational exposures indicate human health effects; see
the EPA's HESD for microcystins (U.S. EPA 2015c) and summaries of recent recreational exposure
case reports of cyanobacteria and microcystin exposures that have been added to the Recreational
AWQC/SA document. Other human studies are also supportive for potential liver damage following
exposure to microcystins (Carmichael 2001; Falconer et al. 1983; Hilborn et al. 2013; Jochimsen et al.
1998; Li et al. 2011).
Acute and subchronic animal studies were identified and described in the EPA's HESD for
microcystins (U.S. EPA 2015c). Of these studies, three oral exposures studies were identified as
possible studies for the development of the short-term guidance value: Heinze (1999), a 28-day
drinking water rat study, Fawell et al. (1999), a 90-day gavage study in mice, and Chen et al. (2011), a
three to six month drinking water mice study. After evaluation and peer review of Chen et al. (2011)
the EPA determined that because of limitations in study design, report and methods used, this study
was not adequate for determining the point of departure for the derivation of the RfD for microcystins.
Heinze (1999) was selected as the key study because of the study duration, the use of multiple doses,
dose-related toxicological responses, and histopathological evaluations of toxicity. The uncertainty
factors apples are consistent with those applied for interspecies and intraspecies uncertainties for many
regulated and unregulated chemicals evaluated by the EPA. The factor of three applied for use of a
LOAEL was based on the data from the Guzman and Solter (1999) study in Sprague Dawley rats.
As for cylindrospermopsin, the information on the human health effects is limited to the observations
from the Australian Palm Island outbreak involving acute and short-term drinking water exposure to
Cylindrospermopsis raciborskii (Byth 1980; Griffiths and Saker 2003). The clinical picture of the illness
is well-defined and includes fever, headache, vomiting, bloody diarrhea, hepatomegaly and kidney
damage with renal loss of water, electrolytes, and protein. However, as with many outbreaks and human
case reports, no data are available on the exposure levels of cylindrospermopsin that induced these
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effects. Nevertheless, these effects, especially kidney damage have been supported by animal studies
(Humpage and Falconer 2002, 2003; Sukenik et al. 2006).
Use of animal data in derivation of the RfDs
Comments Summary: The State of Wyoming Department of Environmental Quality requested
additional explanation as to how extended studies on experimental animals translate into a daily human
exposure value that is not to be exceeded. This commenter also requested an explanation of how
prolonged consumption of toxic drinking water in experimental animals translates into incidental
ingestion in children.
Response:
The EPA used the best available, peer reviewed science to determine algal toxin levels that are
protective of human health. A comprehensive evaluation of the available health effects information and
derivation of these toxicity values (i.e., reference doses or RfDs) for both microcystins and
cylindrospermopsin is included in the EPA's HESDs (U.S. EPA 2015a, 2015b). The HAs for both
microcystins and cylindrospermopsin include an analysis plan which describes the methods used to
develop these toxicity values (U.S. EPA 2015c, 2015d). Briefly, after the available studies were
evaluated for inclusion in the EPA's HESD and HA, the critical study was selected based on
consideration of factors including exposure duration (comparable to the duration of the guideline value
being derived), route of exposure (oral exposure via drinking water, gavage, or diet is preferred), species
sensitivity, comparison of the point of departure with other available studies demonstrating an effect,
and confidence in the study (U.S. EPA 1999). Once a point of departure was chosen for quantification,
uncertainty factors appropriate for the study selected were then applied to the point of departure to
account for variability and uncertainty in the available data. This analysis was subject to independent
expert peer review.
Human data on oral toxicity of microcystins and cylindrospermopsin are limited, but suggest the liver
and kidney as the primary target organs. These studies were inadequate for use quantitatively in the
assessment. Animal studies have shown that acute, short-term, and subchronic exposure can lead to
adverse effects on the liver and kidney.
Animals and humans have both quantitative and qualitative differences that are accounted for when
using animal models with the application of uncertainty factors (interspecies variability from
extrapolating animal data to humans).
As the basis for the default incidental recreational ingestion values, the EPA used a study on children
and adults and found that children age six to 10 ingested higher volumes of water while swimming than
adults (Dufour et al. 2017). Children also spend more time in the water compared to adults (U.S. EPA
2011; Schets et al. 2011). Therefore, although the incidental ingestion volume is expected to be less than
the default value for drinking water, children can be at greater risk from cyanotoxin exposure while
recreating because they consume more water and spend more time in the water than adults.
Benchmark dose modeling
Comments Summary: One commenter (Florida Department of Environmental Protection) requested an
explanation as to why the EPA did not utilize its preferred approach of Benchmark Dose Models (BMD)
in deriving its microcystins and cylindrospermopsin reference doses.
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Response:
For microcystins, the data set reported by Heinze (1999) was evaluated for BMD modeling (U.S. EPA
2015c, 2015e). A discussion of these considerations is presented in the HA and HESD for microcystins.
Briefly, Heinze (1999) demonstrated dose-related liver changes and statistically significant effects at the
lowest dose (50 (j,g/kg/day). The EPA did not choose to do dose-response for the Heinze et al. (1999)
drinking water study because histological changes (necrosis, Kupffer Cell activation, and PAS staining)
were observed in all animals in all dose-groups. For the EPA, the necrosis was the response of greatest
concern. Although differences in the degree of necrosis were observed with or without hemorrhage
related to dose, all the necrosis, Kupffer cell activation and Periodic Acid Schiff (PAS) staining showed
no dose-response since all 10 animals at the low and high doses displayed liver damage associated with
each effect. Therefore, the dose-response for the sum of the incidence categories (slight, moderate, and
intensive damage), are not amenable to BMD modeling. As a result, the LOAEL of 50 [j,g/kg/day
described by Heinze (1999) was used as the POD for development of the HA. In the Guzman and Solter
(1999) study, there were more dose groups but it did not use oral exposure and there were only three
animals per dose group. Thus, it was not appropriate for benchmark dose modeling and was utilized to
help inform the uncertainty analysis. The fact that the 32 mg/kg/day and 48 mg/kg/day dose groups had
hepatic tissue damage helped to support identification of the liver effects as critical as did other studies
(e.g., Fawell et al. 1999) data in mice.
For cylindrospermopsin, Humpage and Falconer (2002, 2003) reported adverse effects on the kidney
including significantly increased relative kidney weight at > 60 [j.g/kg/day, decreased urinary protein and
liver lesions at > 120 [j,g/kg/day, and renal tubular lesions at 240 [j,g/kg/day. No significant renal changes
were observed at 30 mg/kg/day. These adverse effects are potential indicators of suppressed hepatic
protein synthesis or increased retention of low molecular weight of mouse urinary proteins by the kidney
because of damage to the renal tubules. One aspect of determining the approach taken to derive the point
of departure was consideration of whether there is a link between the decreased urinary protein observed
and increased kidney weight. Decreased urinary protein is an adverse effect in mice because the urinary
proteins act as pheromones for mating and tracking. In humans, protein should not be present in urine
and excretion of protein in urine is an indication of kidney damage and is considered adverse. The
magnitude of the response observed by Humpage and Falconer (2002, 2003) at the NOAEL was
approximately 12 percent.
Category 7.4 - Analysis - Criteria duration and frequency
Comments Summary: Seven commenters (Agricultural Retailers Association et al., Hall and
Associates, Mississippi River Collaborative, Ohio Environmental Protection Agency, Upper Neuse
River Basin Association, Water and Environmental Testing, Inc. and South Valley Water Reclamation
Facility, State of Wyoming Department of Environmental Quality) expressed concern about the
scientific rationale and health relevancy of the frequency and the duration criteria. These commenters
cited disapproval of the frequency, specifically the language "no more than 10 percent of days." The
Upper Neuse River Basin Association requested that frequency be removed from the document because
there is "no requirement that a 304(a) criteria document contain implementation decisions for regulatory
programs such as the 303(d) [listing] process." Hall and Associates suggested that a set number of days
to be protective in all situations, tied to definitive scientific evidence, would be preferable to the percent
frequency. The Agricultural Retailers Association et al. stated that the state should have the flexibility to
devise and defend appropriate methods to determine water body attainment status.
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Several commenters maintained that the rationale of the new frequency being "similar to
recommendations for other recreational criteria" was not sufficient. The Upper Neuse River Basin
Association stated that the recommended single day exceedance, as well as alternative exceedance,
frequencies might easily be misapplied. This commenter also pointed out that since the criteria are not
proposing a regulatory threshold, there was no requirement to include regulatory frequencies such a
single sample or single day thresholds.
Similarly, three commenters (Hall and Associates, Mississippi River Collaborative, Water and
Environmental Testing, Inc., and South Valley Water Reclamation Facility) stated the recommended
duration should reflect the conditions and implications of a definitive scientific test in order to be
defensible. Hall and Associates stated it was not clear how the literature cited in defense of the proposed
exposure period was relevant to the cyanotoxin criteria and that "since the effect of cyanotoxins is
cumulative, continuous exposure should be the only relevant concern." The Mississippi River
Collaborative stated that the duration should be reevaluated to include consideration of typical
sampling/budgetary realities and that if the "EPA is recommending that 10% of the time, it is acceptable
if the guideline is exceeded by any amount. Such excursions could commonly, seriously jeopardize
public health."
The Water and Environmental Testing, Inc. and South Valley Water Reclamation Facility stated "The
use of a percentage could be too restrictive for a waterbody with a short recreational period and too
lenient for a waterbody with a long recreational period. For example, a period of three months or 90
days would allow nine days at the recommended magnitude which is excessively protective when
compared to the 28-day definitive exposure period. On the other hand, a 12-month recreation period
would allow 36 days which, in the event of a HAB could be consecutive days, which is over the 28-day
duration of the definitive test and therefore has the real potential for the health exposures described in
the definitive test to develop. Consider a recommendation using a set number of days to be protective in
all situations and that is tied to the definitive test."
Response:
The EPA as clarified the logic and justification for the duration and frequency in the Recreational
AWQC/SA sections 6.3 and 6.4. The EPA considered the public comments received and clarified
recommendations consistent with the health effects data and HABS occurrence. In addition, the EPA
built in flexibilities for state risk managers regarding exceedance frequency.
Category 7.5 - Analysis - Exposure duration and other exposure variables
Comments Summary: Several commenters (Florida Department of Environmental Protection, State of
Wyoming Department of Environmental Quality, Texas Commission on Environmental Quality, Water
and Environmental Testing, Inc. and South Valley Water Reclamation Facility, Hall and Associates,
National Association of Clean Water Agencies, Virginia Association of Municipal Wastewater
Agencies) questioned the exposure duration values used in the draft document. The Karuk Tribe fully
supports the higher ingestion rates and water contact time utilized by the EPA.
Four commenters (Texas Commission on Environmental Quality, Water and Environmental Testing,
Inc. and South Valley Water Reclamation Facility, National Association of Clean Water Agencies,
Virginia Association of Municipal Wastewater Agencies) suggested using a different value for the
exposure duration. The Texas Commission on Environmental Quality suggested that 1.3 hours would be
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a more reasonable exposure duration, based a larger peer reviewed study. The National Association of
Clean Water Agencies suggested that the EPA use the swimming durations published in the most recent
Exposure Factors Handbook (U.S. EPA 2011) or in the Agency's Swimmers Exposure Assessment
Model. The Water and Environmental Testing, Inc. and South Valley Water Reclamation Facility agreed
that use of the 2.7 hours per day is somewhat logical; however, "the time spent swimming per month
data" provides better clarity on how often children spend recreating and should not be discounted. The
"time spent swimming per month" data coupled with the duration of recreational event of 2.7 hours per
day suggests that the children only swim from one to one and a half days per month. The Virginia
Association of Municipal Wastewater Agencies agreed that using monthly swimming values would be
valuable. The use of a monthly swimming value would resolve what they argued is a mismatch between
short-duration exposures and a longer-duration reference dose. They estimated this approach would
generate health protective values more similar to those currently used by the WHO and several states.
The State of Wyoming Department of Environmental Quality was concerned with the underlying
assumption that surface waters would be used for a similar duration as outdoor spas and pools,
especially in colder climates. Hall and Associates argued that active swimming in a lake environment
should not be equated to time spent in a pool either in duration or ingestion level.
Two commenters (Water and Environmental Testing, Inc. and South Valley Water Reclamation Facility,
and Florida Department of Environmental Protection) requested that the EPA clarify the table in their
Exposure Factors Handbook (U.S. EPA 1997) that the document referenced the mean exposure duration
of five to 11 year olds time spent in home pools and spas.
Response:
The EPA used national data available on exposure duration. In the revised document, the EPA expanded
the discussion of exposure duration data sets and uncertainties in the Effects Characterization section
(Recreational AWQC/SA section 7.2). The EPA recognizes that states and tribes may decide to adapt
recommendations based on local conditions, such as shorter duration times due to colder temperatures.
In this case, substantiation of alternative duration parameter will facilitate evaluation of the resulting
value.
The EPA used the duration of a recreational event from the Agency's 2011 Exposure Factors Handbook
Table 16-20 (time spent per 24 hours in an outdoor spa or pool for different age groups) because the
equation used to calculate the AWQC uses a daily ingestion rate (L/d). As the commenter notes, the
2011 Exposure Factors Handbook also includes the mean swimming in minutes/month for different age
groups and a 95th percentile for all age groups of 181 minutes/month. This 95th percentile value is an
artifact of the data collection survey and is not a usable number. The table had a footnote that says "A
value of 181 for number of minutes signifies that more than 180 minutes were spent." The data
collection approach did not quantify time spent at levels greater than 180 minutes.
Category 7.6 - Analysis - Other comments
Comment Summary: The Texas Commission on Environmental Quality asked the EPA to clarify
whether the criteria apply to total microcystins or cylindrospermopsin, any of the known congeners, or
whether congeners could be used as a surrogate for total toxins. The commenter noted that certain
methods of analyses, such as enzyme-linked immunosorbent assays (ELISA), are not specific at
identifying variants. The State of Wyoming Department of Environmental Quality recommended that
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the EPA clarify more consistently across the document that the criteria are for total cyanotoxin
concentration.
Response:
The EPA has added language clarifying that the values are for total microcystins.
Comment Summary: The American Water Works Association questioned why the EPA's toxicological
analysis resulted in substantially lower criteria than those of other authoritative bodies and suggested re-
examination of the data and better alignment with methodology used by those other organizations.
Response:
In the derivation of the recreational criteria and swimming advisories for microcystins and
cylindrospermopsin, the EPA used the oral RfD values that were previously derived in its HESDs for
microcystins and cylindrospermopsin (U.S. EPA 2015c, 2015d). The peer review of the EPA's
HESDs included charge questions requesting comment on whether there was sufficient data to derive
reference doses for microcystins and cylindrospermopsin. The peer reviewers supported the
development of reference values for these cyanotoxins. See Recreational AWQC/SA Table 2-2 for a
list of international recreational water guideline or action levels for cyanobacteria and microcystins.
Microcystin thresholds in other countries range between four and 25 |ig/L and the EPA's AWQC are
also within that range.
Comments Summary: The State of Wisconsin Department of Natural Resources suggested that the
EPA explore criteria derived using the 80th percentile values. This commenter requested the EPA
conduct a sensitivity analysis to understand which exposure factors are the most sensitive.
Response:
The EPA followed its 2000 AWQC guidance (U.S. EPA 2000), which recommends using 90th
percentile values. The Effects Characterization (section 7.3.1) of the Recreational AWQC/SA provides
an evaluation of multiple lifestages.
Comments Summary: The Mississippi River Collaborative recommended that the EPA revise its draft
guidelines to be more conservative in protecting human health and suggested alternative calculated
criteria values. They calculated alternate draft guidelines for microcystins (1.23 |ig/L) and
cylindrospermopsin (2.31 |ig/L) and stated that they should be considered by the EPA to replace the
present draft guidelines. They suggested that these values could be rounded to two |ig/L and 2.5 |ig/L,
respectively. They noted that, at present, the lowest state recreational guidelines for microcystins and
cylindrospermopsin are 0.8 |ig/L and four |ig/L, respectively.
Response:
The EPA appreciates the commenter's offer of alternative values and reminds states and tribes that the
Recreational AWQC/SA are recommendations; states and authorized tribes have the flexibility to adopt
other values into state standards if those values are scientifically defensible and protective of the
designated use.
Comments Summary: The Texas Commission on Environmental Quality recommended that the EPA
incorporate the results of the 2012 National Lakes Assessment (NLA) into the draft recommendations
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rather than relying solely on the 2007 NLA report. This would ensure that the recommendations would
reflect the most recent data.
Response:
The 2012 NLA results were not published in time to incorporate those results in the draft document
before it was released for public comment. The EPA has revised the current document to include the
2012 NLA results.
Category 8 - Implementation
Category 8.1 - Implementation - Recommend/provide information on methods for
cyanotoxins
Comments Summary: Many commenters (State of Wyoming Department of Environmental Quality,
Iowa Department of Natural Resources et al., Georgia Department of Natural Resources Georgia
Environmental Protection Division, Hall and Associates, Iowa Farm Bureau Federation, Lake Erie
Foundation, State of Wisconsin Department of Natural Resources, Florida Department of Environmental
Protection, Kentucky Division of Water, Texas Commission on Environmental Quality, Massachusetts
Department of Public Health and Massachusetts Department of Environmental Protection, New Jersey
Department of Environmental Protection, North Carolina Upper Neuse River Basin Association,
Washington DC American Water Works Association, Association of Clean Water Administrators,
National Association of Clean Water Agencies, Clean Ocean Water Act, Great Lakes Environmental
Law Center), regardless of whether they support using the document as an AWQC or swimming
advisory, requested recommendations/information on monitoring methods (and sample protocols). They
stated that there are many methods available and it is not clear which is best for recreational water
bodies. They noted that the EPA has not approved a cyanotoxin method in 40 CFR Part 136. Several
commenters also raised concerns over the variability of available methods based on the 2007- 2008
Florida round-robin study. Hall and Associates and the Iowa Farm Bureau Federation also expressed
concern over differentiating between naturally occurring blooms and those due to the discharge of
pollutants.
Response:
The EPA agrees that information on the use of analytical methods and associated sampling techniques
would be helpful to implement the AWQC/SA. The Agency recently released technical materials to aid
in the development of cyanobacteria and cyanotoxin monitoring programs, including information on
available methods (U.S. EPA 2017a, 2017b). Specifically, these materials include: a decision tree on
monitoring and notifying the public on the risk from cyanotoxins; information on available analytical
methods and technologies; and examples of and links to state HABs program resources.
For the EPA's response to differentiating between naturally occurring blooms and blooms due to
pollutants please refer to comment category 1.5.
Related information:
• There is no single cyanotoxin method the EPA recommends at this time for ambient waters;
however, the Recreational AWQC/SA magnitude values are at least an order of magnitude above
the limit of detection for nearly all available methods. A recent study by Gaget et al. (2017)
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compared several assays for cyanotoxins and supports the EPA's conclusion that there is no "gold
standard" technique for the detection of cyanotoxins in recreational waters; however, current
methods are good at confirming presence of cyanotoxins. The paper recommends considering cost,
practicality, reliability and comparability of results before choosing a method.
•	Analytical methods and remote technology for measuring/predicting cyanotoxins is rapidly
evolving through research by the EPA's Office of Research and Development, other federal and
state agencies, as well as by companies selling the various kits and supplies associated with
cyanotoxin tests. For example, the methods used in the 2007-2008 round-robin study in Florida as
well as the method used in the EPA's 2012 National Aquatic Resource Surveys have been updated
or refined.
•	The EPA recently released an ambient-water method for quantifying specific microcystins (and
nodularin) using Adda-ELISA technology (EPA Method 546). The EPA made available in 2018,
two draft ambient-water methods based on liquid chromatography-tandem mass spectrometry
(LC/MS/MS) technology: one for thirteen microcystin congeners and nodularin, and another for
cylindrospermopsin and anatoxin-a.
•	Sample preparation/processing and analytic standards are very much tied to individual methods
and therefore questions on these issues can be answered by the protocol or vendor of the method
materials. Sampling issues related to where and when to sample are tied to the location and
environmental conditions and what question is being asked (e.g., is it safe to swim, or is this water
in attainment with WQS?). Local or state managers can best address those issues on a site-specific
basis. The EPA intends to continue to develop information on sampling issues as additional
research and data becomes available.
Category 8.2 - Implementation - Use of non-toxin endpoints
Comments Summary: A few commenters (Iowa Department of Natural Resources et al., New Jersey
Department of Environmental Protection, North Carolina Lower Neuse River basin Association,
Washington DC American Water Works Association, Iowa Farm Bureau Federation, Lake Erie
Foundation Clean Water Action/Clean Water Fund, State of Wisconsin Department of Natural
Resources) requested information on issuing advisories or prioritizing analytical testing based on
phycocyanin, chlorophyll a, cell counts, or other (non-toxin) information. Some commenters already
have a HAB program based on a non-toxin endpoint.
Response:
The EPA agrees that information on the use of analytical methods and associated sampling techniques
would be helpful, and includes information on cyanobacterial cells in the Effects Characterization
section of the Recreational AWQC/SA document. In addition, the Agency has recently released
technical materials to aid in the development of cyanobacteria and cyanotoxin monitoring programs
(U.S. EPA 2017b). Specifically, in addition to information on analytical methods for cyanotoxins, these
materials include: a discussion on prioritizing recreational waters for monitoring; a discussion of, and
links to, non-toxin methods (e.g., identification of cyanobacteria species); use of non-toxin endpoints
(e.g., the WHO and certain state programs); and remote sensing tools for use in issuing advisories. The
cyanotoxin implementation materials include three key references for cyanobacteria identification (U.S.
Geological Survey), cell counts (the WHO), and cell biomass (International Guidance Manual for the
Management of Toxic Cyanobacteria referred to as the 'Australian Report'). The EPA's Office of
Research and Development and the National Oceanic and Atmospheric Administration continue to make
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progress toward providing remote sensing data on chlorophyll a concentrations in large water bodies
nationwide.
Category 8.3 - Implementation - Criteria support materials
Comments Summary: Several commenters (State of Wisconsin Department of Natural Resources,
State of Wyoming Department of Environmental Quality, Kentucky Division of Water, Texas
Commission on Environmental Quality, California State Water Resources Control Board, Vermont
Department of Environmental Conservation, State of Utah Department of Environmental Quality
Division of Water Quality, Ohio Environmental Protection Agency, Washington DC American Water
Works association, Association of Clean Water Administrators, Agricultural Retailers Association et al.,
Oregon Department of Environmental Quality, Surfrider Foundation, Great Lakes Law Center), urged
the EPA to address how to assess waterbodies for impairment, calculate cyanotoxin Total Maximum
Daily Loads (TMDLs), and collect samples for CWA 303(d) listing decisions and issue permits. Some
commenters (Texas Commission on Environmental Quality, Washington DC American Water Works
Association, Agricultural Retailers Association et al., Great Lakes Environmental Law Center) would
like the EPA to address how to develop and implement management strategies. The New York State
Department of Environmental Conservation and Department of Health, Association of Clean Water
Administrators suggested conveying qualitative information to the public, such as public notices or
general recommendations to avoid recreational exposure in areas with suspected or confirmed
cyanobacterial blooms.
Response:
The EPA agrees that information on implementation of microcystins and cylindrospermopsin criteria
would be helpful. The Agency's goal is to release criteria technical support materials following the final
Recreational AWQC/SA that provide information on implementation of these criteria, including
information on assessment and CWA section 303(d) listing, TMDL development, and CWA section 402
NPDES permitting. In a separate effort, the EPA is working to develop nutrient criteria tools that take
this recreational criteria endpoint into account.
Related information:
•	The EPA is working to ensure implementation-related questions and comments are addressed
through separate implementation materials.
•	The EPA has published Recreational Water Communication Toolbox for Cyanobacterial Blooms
that provides resources for beach managers to use in communicating risk to the public about
cyanotoxins in lakes, rivers, or other recreational water bodies (U.S. EPA 2017a).
Category 8.4 - Implementation - Impacts of implementation
Comments Summary: A few commenters (Iowa Department of Natural Resources, Texas Commission
on Environmental Quality, American Water Works Association) expressed concern over the impact of
implementing the Recreational AWQC/SA on existing water quality management programs and the
public's perception of water safety. They suggest that the EPA remain flexible in their implementation
of these criteria and seek to prepare state and local authorities for potential issues. Some of the
commenters suggested investigating the cause of the conditions causing the blooms (Oregon Department
of Environmental Quality, Georgia Department of Natural Resources Georgia Environmental Protection
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Division) or increasing public education (Agricultural Retailers Association et al., Clean Water
Action/Clean Water Fund, North Carolina Lower Neuse River Basin Association) instead of focusing on
the quantitative measure of cyanotoxin levels. Some commenters (Iowa Department of Natural
Resources et al., Georgia Department of Natural Resources Georgia Environmental Protection Division,
American Water Works Association, Association of Clean Water Administrators, Iowa Farm Bureau
Federation, Ohio Environmental Protection Agency, Georgia Department of Natural Resources Georgia
Environmental Protection Division) are concerned that they will not be able to afford comprehensive
cyanotoxin testing of all water bodies. The City and County of Honolulu Department of Environmental
Services Division of Environmental Quality, Honolulu, Hawaii noted that HABs rarely occur in their
region and implementing monitoring and analysis is not justifiable in that region. The American Water
Works Association suggests the EPA wait for the revised the WHO drinking water guidelines (currently
under review) before finalizing its assessment.
Response: The EPA intends to remain flexible in guidance on how states might implement these
criteria. The implementation materials that the EPA plans to release should help states and local
authorities identify potential issues and suitable local solutions. The EPA agrees that investigation of the
cause of conditions that cause blooms and further public education are important components of
protecting public health. These efforts can be supported by quantitative measures of cyanotoxin levels.
CWA 304(a) human health criteria do not take financial or technological constraints into consideration.
The EPA is working with the WHO in the update of their drinking water guidelines. However, these
AWQC/SA are for recreational waters, not for drinking water.
Category 9 - Other General Comments
Comments Summary: Twelve commenters (State of Wyoming Department of Environmental Quality,
Florida Department of Environmental Protection, Texas Commission on Environmental Quality,
California State Water Resources Control Board, Connecticut Department of Energy and Environmental
Protection, Georgia Department of Natural Resources, Georgia Environmental Protection Division, State
of Utah Department of Environmental Quality Division of Water Quality, Massachusetts Department of
Public Health and Massachusetts Department of Environmental Protection, Ohio Environmental
Protection Agency, Water and Environmental Testing, Inc. and South Valley Water Reclamation
Facility, National Association of Clean Water Agencies, The North Carolina, Upper Neuse River Basin
Association, Mississippi River Collaborative) provided editorial comments for the EPA to consider,
including updated or corrected information, and requests for clarification.
Response:
The EPA made the following requested editorial updates:
•	The EPA clarified in the opening summary that the values are based on children's oral exposure
due to their findings that this group experiences the highest exposure.
•	The EPA updated the document with the cylindrospermopsin study sample sizes.
•	The EPA added information to the citation for the Humpage and Falconer (2002) reference,
including the URL link to Water Research Australia website where the report can be accessed.
•	The EPA added clarification to the document that the values refer to total microcystins.
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•	The EPA double-checked and verified the accuracy of the microcystins concentration in surfaces
waters values.
•	The EPA corrected the status of state recreational water guidelines for cyanotoxins and
cyanobacteria in Texas.
•	The EPA updated the document to reflect information provided regarding California's guidelines
or action levels for microcystins, cylindrospermopsin, and cyanobacterial cells to include the
recent work of the California Cyanobacteria and Harmful Algal Bloom (CCHAB) Network.
•	The EPA updated the document to accurately reflect the Connecticut Department of Energy and
Environmental Protection program guidelines for cyanotoxins and cyanobacteria.
•	The EPA updated the document to provide scientifically accurate information regarding
distribution of microcystins through the water column.
•	The EPA checked and updated information regarding cyanobacteria identified during the 2016
bloom in Utah Lake.
•	The EPA updated the document to accurately report MDPH guidelines for cyanobacteria in
freshwater recreational water bodies in Massachusetts.
•	The EPA updated the document to accurately report Ohio state action levels for microcystins.
•	The EPA corrected section cross references.
•	The EPA clarified the cylindrospermopsin no-observed-adverse-effect-level.
The EPA did not change the title of the document as suggested by The North Carolina, Upper Neuse
River Basin Association because the title as drafted is an accurate reflection of the contents and intention
of the document.
The EPA also reviewed over 60 articles and attachments that the commenters cited or included in their
comment submission. Citations were added to the Recreational AWQC/SA document where
appropriate.
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