An Approach for Applying EPA's 2012 Recreational Water
Quality Criteria Recommendation to Non-primary Contact
Exposure Scenarios
White Paper
Office of Science and Technology
Office of Water
U. S. Environmental Protection Agency
Washington DC 20460
January 2022
Office of Water 823-B-22-001
-------
Author:
Gary Russo, Ph.D., Office of Water, Office of Science and Technology, Standards and Health
Protection Division.
Lead Reviewer:
Katherine Bentley, Office of Water, Office of Science and Technology, Health and Ecological
Criteria Division (on detail from Region 3, Water Division).
Additional Reviewers (in alphabetical order):
Shari Barash, Office of Water, Office of Science and Technology, Standards and Health
Protection Division.
Betsy Behl, Office of Water, Office of Science and Technology, Health and Ecological Criteria
Division.
Sara Hisel-McCoy, Office of Water, Office of Science and Technology, Standards and Health
Protection Division.
Sharon Nappier, Office of Water, Office of Science and Technology, Health and Ecological
Criteria Division (currently in Office of Water, Office of Policy Management and Engagement).
Jamie Strong, Ph.D., Office of Water, Office of Science and Technology, Health and Ecological
Criteria Division (currently in Office of Research and Development, Center for Public Health
and Environmental Assessment).
Lars Wilcut, Office of Water, Office of Science and Technology, Standards and Health
Protection Division.
Acknowledgements:
The author acknowledges Jeffery Soller of Soller Environmental, LLC for early concept
development under ICF contract EP-C-11-005 (John Ravenscroft, EPA work assignment
manager), and Alfred Dufour, Ph.D., Office of Research and Development, Center for
Environmental Measurement and Modeling, for helpful comments and suggestions.
Notices
This document has undergone contractor-led external peer review as well as a review process
within the U.S. Environmental Protection Agency (EPA). This document has undergone final
review and been approved for publication by the Standards and Health Protection Division and
Health and Ecological Division in the Office of Science and Technology.
Disclaimer:
This EPA document proposes an approach for adjusting EPA's existing §304(a) Recreational
Water Quality Criteria recommendation for primary contact recreation that provides a similar
risk of GI illness in non-primary contact exposure scenarios. This document does not change or
substitute for any law, regulation, or any other legally binding requirement and is not legally
enforceable. This document is not a regulation and does not impose legally binding requirements
-------
on EPA, states, tribes, or the regulated community, and might not apply to a particular situation
based upon the circumstances. EPA may change this document in the future.
-------
Table of Contents
Abstract i
1. Introduction 1
2. Application of the methodology from EPA's 2012 RWQC to non-primary contact
recreation scenarios 2
2.1. Approach 2
2.2. Assumptions 3
2.3. Exposure assessment 4
2.3.1. Route 4
2.3.2. Duration 4
2.3.3. Magnitude 5
2.3.4. Frequency 6
2.4. Developing adjustment factors for non-primary contact exposure scenarios 6
3. Incidental water ingestion during different recreational activities 9
References 12
-------
Abstract
EPA's 2012 Recreational Water Quality Criteria (RWQC) document describes primary
contact recreation as "activities where immersion and ingestion are likely and there is a high
degree of bodily contact with the water, such as swimming, bathing, surfing, water skiing,
tubing, skin diving, water play by children, or similar water-contact activities." However, some
states and authorized tribes adopt uses other than primary contact recreation. These other types
of recreational uses have historically been dubbed secondary contact, limited water contact,
limited body contact, partial body contact, incidental contact, or limited contact recreation
(henceforth all referred to as non-primary contact recreation). Non-primary contact recreation is
often associated with less ambient water contact and where immersion and ingestion of ambient
water is less likely than primary contact recreation. Consequently, some states and tribes assign
less stringent water quality values for non-primary contact recreation on the basis that less
contact with pathogens in water compensates for a higher concentration of those pathogens
resulting in the same overall risk of illness. However, there is limited information on how to
determine water quality that would protect the public while engaging in non-primary contact
recreation.
EPA proposes a method for applying non-primary contact exposure scenarios to the
geometric mean and statistical threshold value in EPA's 2012 RWQC for primary contact
recreation. This method characterizes exposure during different types of water recreation using
quantitative data on the amount of incidental ingestion of ambient water. EPA derives an
equation implementing this method as:
pFIB pFIB y 1primary
^non-primary ^primary A T
1 non-primary
where:
the concentration of fecal indicator bacteria (FIB) associated with a
particular risk of illness during primary contact recreation.
the concentration of FIB in the same ambient water associated with the
same risk of illness during non-primary contact recreation.
the amount of ambient water incidentally ingested during primary
contact recreation as described in EPA's 2012 RWQC.
the amount of ambient water incidentally ingested during a specific
non-primary contact recreational activity.
When the value of C^mary equals a primary contact criterion magnitude specified in EPA's
2012 RWQC, the value C^on-primary represents a comparable non-primary contact magnitude
with the same risk of illness. This method is an approach for adjusting EPA's existing §304(a)
RWQC recommendation for primary contact recreation to provide a similar risk of GI illness in
non-primary contact exposure scenarios. This method is not itself an EPA criterion
recommendation pursuant to §304(a) of the Clean Water Act.
rFIB
uprimary
nFIB
^non-primary
I primary
Inon-primary'
1
-------
1. Introduction
Between 2000 and 2014 there were at least 140 untreated recreational water-associated
outbreaks that caused at least 4,958 illnesses and two deaths (Graciaa et al., 2018). EPA's 2012
recreational water quality criteria (RWQC) recommendation (USEPA, 2012b) provides specific
levels of protection from gastrointestinal illness associated with "primary contact" recreation.
EPA's 2012 RWQC document describes primary contact recreation as "activities where
immersion and ingestion are likely and there is a high degree of bodily contact with the water,
such as swimming, bathing, surfing, water skiing, tubing, skin diving, water play by children, or
similar water-contact activities." For some waters where primary contact activities do not occur,
occurs seasonally, or where the water quality does not support primary contact recreation, some
states and authorized tribes adopt other types of recreational uses. These other types of
recreational uses have historically been dubbed secondary contact, limited water contact, limited
body contact, partial body contact, incidental contact, or limited contact recreation (henceforth
all referred to as non-primary contact recreation).
Non-primary contact recreation can also result in gastrointestinal illness (Dorevitch et al., 2012).
However, non-primary contact recreation is presumed to be associated with less ambient water
contact and where immersion and ingestion of ambient water is less likely compared to primary
contact recreation. Consequently, water quality standards for non-primary contact recreation are
often less stringent than EPA's recommendation for primary contact recreation based on the
presumption that less contact with ambient water compensates for a higher pathogen
concentration in recreational waters resulting in the same risk of illness. Some states have
developed values for protection of non-primary contact recreation by multiplying EPA's RWQC
recommendations for primary contact recreation by a factor of five and occasionally as high as
ten. However, there is a limited or outdated scientific basis for developing or evaluating water
quality standards for non-primary contact recreational uses. The multiplier value of five was
derived from RWQC recommendations in a 1968 National Technical Advisory Committee report
(Federal Water Pollution Control Administration, 1968) that EPA later assessed as insufficient
(USEPA, 1986).
Although the scientific justification for previous multiplier values was limited, using a
multiplier to adjust primary contact recreation values to address risk in non-primary contact
exposure scenarios may be a reasonable approach. Illness risk associated with recreational
exposure to ambient water is related to both the degree of exposure to water during recreation
and the concentration of pathogens in that water (USEPA, 2012a). EPA's 2012 RWQC identifies
gastrointestinal (GI) illness as the most appropriate health endpoint through the exposure route of
oral ingestion. Individuals engaging in activities with greater water contact (i.e., greater exposure
through oral ingestion) have a higher risk of GI illness compared to individuals engaging in
activities with less water contact (i.e., less exposure through oral ingestion) (Russo et al., 2020;
Wade et al., 2008; Wade et al., 2006; Wade, Pai, Eisenberg, & Colford, 2003; Wade et al., 2010).
A recent systematic review and meta-analysis (Russo et al., 2020) evaluated risk of illness
associated with three different categories of recreational activities corresponding to different
types of water contact - swimming, minimal contact (e.g., fishing, boating, and canoeing or
kayaking in calm waters), and sports-related contact (e.g., snorkeling, surfing, and canoeing or
kayaking in turbulent waters). The study by Russo et al. (2020) suggests minimal contact
activities with a lower level of exposure to ambient water are associated with a lower risk of GI
1
-------
illness compared to swimming, whereas sports-related activities with the same or higher level of
exposure to ambient water are associated with the same or higher risk of GI illness compared to
swimming. Thus, both water quality and the level of exposure determines illness risk associated
with recreation in ambient water.
Given a concentration of pathogens in ambient water, the main difference between risk of
GI illness associated with primary contact recreation and risk of GI illness associated with
non-primary contact recreation is the level of exposure through oral ingestion. EPA's current
RWQC recommendation (USEPA, 2012b) applies to a level of exposure characterized as
primary contact recreation. One way to achieve a similar level of public health protection for
non-primary contact recreation is to apply alternative exposure scenarios to the values EPA
recommends in its 2012 RWQC for primary contact recreation that results in the same level of
pathogen ingestion during non-primary contact recreation. This white paper proposes a method
for adjusting EPA's RWQC recommendation for primary contact recreation to provide a similar
risk of GI illness in non-primary contact exposure scenarios. This proposed method is not itself a
criteria recommendation as provided under §3 04(a) of the Clean Water Act.
2. Application of the methodology from EPA's 2012 RWQC to non-primary contact
recreation scenarios
EPA proposes a method for applying non-primary contact exposure scenarios to the
methodology used in EPA's 2012 RWQC for primary contact recreation. The proposed method
uses quantitative data on the amount of incidental ingestion of ambient water during different
types of recreational activities as the measure of exposure.
2.1. Approach
When developing its 2012 RWQC, EPA identified the hazard of concern as pathogenic
microorganisms in fecally-contaminated surface waters. Pathogens often co-occur with bacterial
indicators of fecal contamination. Therefore, EPA relied on fecal indicator bacteria (FIB) to
serve as pathogen indicators. A pathogen indicator, as defined in §502(23) of the CWA, as
amended by the BEACH Act, is defined as: "a substance that indicates the potential for human
infectious disease." EPA has a long history of using FIB for protecting people who use
recreational waters and has long set water quality criteria for the protection of primary contact
recreation based on the relationship between FIB density and the occurrence of human illness.
Using a series of epidemiological studies EPA conducted in association with the development of
its 1986 Ambient Water Quality Criteria for Recreation Waters (Cabelli, 1983; Dufour, 1984;
USEPA, 1986) and National Epidemiological and Environmental Assessment of Recreational
Water (NEEAR) studies (USEPA, 2009; Wade et al., 2008; Wade et al., 2006; Wade et al.,
2010), EPA found gastrointestinal (GI) illnesses had the strongest association with FIB
concentration and concluded that criteria based on protecting the public from GI illness will
prevent most types of recreational waterborne illnesses (USEPA, 2012b). Those epidemiological
studies used primary contact and no-contact exposure groups to evaluate illness rates associated
with different levels of FIB in recreational waters. The epidemiological studies allowed EPA to
develop a dose-response assessment (i.e., evaluation of illness risk at different water quality
levels) among participants who engaged in primary contact recreation. EPA developed criteria
values as levels of FIB corresponding to specified illness rates.
2
-------
In this paper, EPA proposes an approach for determining the water quality necessary to
protect non-primary contact recreational uses. The approach is based on applying adjustment
factors to EPA's 2012 RWQC for primary contact recreation. EPA's 2012 RWQC focused on
water quality associated with risk of GI illness during primary contact recreation. However,
differences in risk of GI illness between primary and non-primary contact recreation can be
characterized as due to differences in exposure to pathogens in water through oral ingestion. The
approach proposed here assumes the same stressors EPA used to develop it's 2012 RWQC for
primary contact recreation (pathogenic microorganisms in fecally-contaminated surface waters)
but derives adjustment factors representing differences in levels of water contact during primary
and non-primary contact recreation. The adjustment factors are derived from data on incidental
ingestion during primary and non-primary contact recreation. Application of the adjustment
factors to the values in EPA's 2012 RWQC for primary contact recreation results in water
quality values with a similar risk of GI illness during non-primary contact recreation.
As mentioned above, EPA does not consider the approach described in this paper or any
values resulting from the approach as criteria recommendations pursuant to §3 04(a) of the Clean
Water Act. Instead, EPA considers the approach described in this paper an implementation tool
to help states and authorized tribes make risk management decisions when considering
recreational designated uses other than primary contact recreation and to help determine the
levels of FIB necessary to protect those designated uses. Any water quality values resulting from
the application of the approach described in this paper are not applicable for Clean Water Act
purposes until a state or authorized tribe adopts them into their state or tribal water quality
standards and EPA approves them. EPA expects states and authorized tribes to rely on their
EPA-approved RWQC for primary contact recreation when both primary and non-primary
contact recreation co-occur or are co-designated consistent with EPA regulations at
40 CFR §131.11(a) regarding protection of the most sensitive designated use.
2.2. Assumptions
EPA assumes the hazard of concern, indicators of fecal contamination, enumeration
methods, human health endpoints, scope of analysis, and the pathogen dose-response relationship
EPA used to develop its 2012 RWQC for primary contact recreation are applicable to both
primary contact and non-primary contact recreation. EPA assumes the pathogens causing GI
illness associated with primary contact recreation are the same pathogens causing GI illness
associated with non-primary contact recreation. EPA also assumes the same FIB EPA used to
develop its 2012 RWQC for primary contact recreation applies to non-primary contact recreation
scenarios.
Although the dose-response relationships of most pathogens are sigmoidal in shape with
an inflection point above which there is a steep increase in risk of infection and illness with
increasing dose, the relationship between dose and illness risk is roughly linear in the low-dose
range below the inflection point that includes the illness risk targets of EPA's 2012 RWQC (32 -
36 illnesses/1000 recreators). Thus, EPA assumes that the dose-response relationships of the
pathogens responsible for excess GI illness associated with non-primary contact recreation is
also linear in the dose range expected to occur in non-primary contact recreational waters.
EPA conducted epidemiological studies that were the basis of its 2012 RWQC at highly
used beaches at a variety of geographic locations that included participants with a broad
3
-------
demographic profile. EPA assumes the same health outcomes, host-pathogen profile, FIB-
pathogen relationships, and FIB-risk relationships apply to both primary contact and non-primary
contact recreators.
2.3. Exposure assessment
EPA proposes applying an adjustment factor to EPA's 2012 RWQC to characterize
alternative exposure scenarios associated with non-primary contact recreation. A critical
component of this approach is an assessment of the exposure associated with different
recreational activities. EPA describes primary contact recreation as "activities where immersion
and ingestion are likely and there is a high degree of bodily contact with the water, such as
swimming, bathing, surfing, water skiing, tubing, skin diving, water play by children, or similar
water-contact activities." However, water recreation encompasses a greater diversity of activities
including but not limited to snorkeling, windsurfing, bodysurfing, rafting, canoeing, kayaking,
rowing, standup paddle-boarding, boating, fishing, caving, and sailboarding. Furthermore, the
weather and water conditions during recreation may have a substantial effect on the magnitude
and/or probability of exposure. For example, rafting, canoeing, or kayaking in relatively calm
conditions are likely to result in a lower exposure compared to those same activities during high
water flows or in turbulent conditions.
Microbial exposure assessment estimates or measures the route, duration, magnitude, and
frequency of exposure to a microbial hazard, along with the number and characteristics of the
person or population exposed (USEPA, 2012a). Understanding the exposure profile of recreators
in ambient water during primary and non-primary contact recreation provides the basis for
adjusting the exposure assessment element underlying the studies and methodology in EPA's
2012 RWQC.
2.3.1. Route
The epidemiological studies that form the basis of EPA's 2012 RWQC for primary
contact recreation evaluated a variety of adverse health endpoints including GI illnesses, upper
respiratory illnesses, rash, eye ailments, earache, and skin infections. Because the primary route
of exposure to microorganisms causing GI illness is oral ingestion, EPA assumes incidental oral
ingestion of ambient water as the route of exposure to water-borne pathogens associated with
both primary and non-primary contact water recreation.
2.3.2. Duration
Duration of exposure describes the length of time a person is exposed to a microbial
hazard. The epidemiological studies that form the basis of EPA's 2012 RWQC for primary
contact recreation estimated illness risk associated with the cumulative exposure to ambient
water that typically occurs during a one-day beach visit. EPA assumes that a one-day visit to a
surface water location is a reasonable characterization of the duration of exposure for both
primary contact and non-primary contact recreation.
4
-------
2.3.3. Magnitude
Exposure magnitude describes the amount (dose) of a microbial hazard. In the context of
water-based recreation, exposure magnitude can be characterized as jointly the amount of water
that recreators incidentally ingest and the density of pathogenic microorganisms in the ingested
water.
Although recreators generally seek to avoid swallowing ambient water while recreating,
instances of incidental ingestion during recreation can occur. The cumulative amount of water
that recreators incidentally ingest during one day of water-based recreation is primarily
determined by two factors. One factor is the amount of water recreators swallow with each
instance, and the other factor is the number of times such instances occur.
The number of times recreators swallow ambient water during one day of recreation can
vary with different recreational activities. The probability of incidental water ingestion is highest
when recreators immerse their head below the surface of the water, and different recreational
activities are associated with different probabilities of head immersion. For example, Wade et al.
(2006) found in their epidemiological study of primary contact recreation that 30% (1734/5716)
of beachgoers reported immersing their head below the surface of the water whereas Dorevitch et
al. (2011) found in their study of incidental water ingestion during non-primary contact
recreation that only 5.4% (41/766) of surface water canoers and 3.4% (27/801) of surface water
kayakers reported capsizing (and thus immersing their head below the surface of the water).
The amount of water swallowed with each instance may also vary with different
recreational activities. For example, the amount of swallowed water in each instance is likely
higher with head immersion compared to splashing or hand-to-mouth contact. The amount of
swallowed water in each instance may also depend on the level of physical exertion or the unique
characteristics of the activity (e.g., water skiing where relatively large amounts of water may be
forced into the mouth during impact with the water's surface).
Several studies of incidental water ingestion associated with different types of water-
based recreational activities have been published (DeFlorio-Barker et al., 2018; Dorevitch et al.,
2011; Dufour, Behymer, Cantu, Magnuson, & Wymer, 2017; Dufour, Evans, Behymer, & Cantu,
2006; Schets, Schijven, & de Roda Husman, 2011; Suppes, Abrell, Dufour, & Reynolds, 2014).
EPA developed exposure values for primary contact recreation in a recent recreational water
quality criteria for cyanotoxins (USEPA, 2019a) based on results of Dufour et al. (2017). EPA's
Exposure Factors Handbook summarizes many (but not all) of these studies and provides tables
of ingestion estimates for a variety of different types of recreational activities (USEPA, 2019b).
These studies reported the amount of incidental ingestion either as a rate of ingestion per unit
time or as a total amount over a particular time period. EPA assumes that the magnitude of
exposure is characterized as jointly the cumulative amount of ambient water incidentally
ingested during the exposure duration (one day of recreation) and the density of pathogenic
microorganisms in the water ingested.
Children exhibit behaviors that increase their exposure to environmental contaminants,
including increased head and body immersion in recreational waters (USEPA, 2009; Wade et al.,
2008; Wade et al., 2006) and hand-to-mouth contact (Xue et al., 2007). Children also stay in the
water longer than adults (Wade et al., 2008; Wade et al., 2006) and ingest more water (DeFlorio-
Barker et al., 2018; Suppes et al., 2014). Although EPA exposure values for primary contact
recreation in a recent recreational water quality criteria for cyanotoxins were based on exposure
5
-------
to children (USEPA, 2019a), EPA's 2012 RWQC recommendations are based on exposure to the
general population including children. Therefore, the approach proposed in this paper assumes
exposure to the general population including children.
2.3.4. Frequency
Frequency of exposure describes how often a person is exposed to a microbial hazard. As
discussed in section 2.3.3, the probability of incidental water ingestion is highest when
recreators immerse their head below the surface of the water. A variety of conditions and
circumstances can affect the frequency of such events. However, the epidemiological studies
underlying EPA's 2012 RWQC for primary contact recreation evaluated illness rates associated
with the cumulative total of all exposure events during one day of primary contact recreation in a
typical beach environment. Because primary contact and non-primary contact recreation are
likely to occur in ambient surface waters with similar physical characteristics, EPA assumes the
frequency of individual exposure events is determined by the particular recreational activity of
the recreator. Thus, the frequency of exposure is incorporated into the characterization of
exposure magnitude and the exposure dose constitutes the total number of organisms in the set of
individual exposures that occur during one day of recreation.
2.4. Developing adjustment factors for non-primary contact exposure scenarios
The "dose" associated with illness risk is the number of pathogenic microorganisms
incidentally ingested during recreation. As discussed in section 2.3, the number of pathogenic
microorganisms incidentally ingested during recreation is determined by both the density of
pathogenic microorganisms in the water and the amount of water incidentally ingested. The FIB
density recommended in EPA's 2012 RWQC associated with a particular illness rate assumes an
ingestion amount typically expected while engaging in primary contact recreation over the
course of a single day. Ingestion amount associated with non-primary contact recreation can be
used to estimate an alternative FIB concentration that results in the same "dose" of pathogenic
microorganisms that results in the same illness rate as provided by EPA's 2012 RWQC for
primary contact recreation.
The relationship between microorganism concentration, ingestion amount, and illness
risk can be represented mathematically. Assuming illness risk during recreation is the result of
the number of pathogenic microorganisms incidentally ingested, then:
Dprimary ~ Cprimary ^ ^primary (Equation 1)
and
Dnon-primary ~ Cnon-primary ^ ^non-primary (Equation 2)
where:
Dprimary = the number of pathogenic microorganisms ("dose") incidentally ingested
during primary contact recreation,
6
-------
Dnon-primary = the number of pathogenic microorganisms ("dose") incidentally ingested
during non-primary contact recreation,
^primary = the concentration of pathogenic microorganisms in ambient water during
primary contact recreation,
^non-primary = the concentration of pathogenic microorganisms in ambient water during
non-primary contact recreation,
I primary = the amount of ambient water incidentally ingested during primary
contact recreation as described in EPA's 2012 RWQC.
Inon-primary = the amount of ambient water incidentally ingested during a specific
non-primary contact recreational activity.
Because illness risk is determined by the number of pathogenic microorganisms
incidentally ingested during recreation and EPA is interested in identifying a concentration of
pathogenic microorganisms that results in the same illness risk under both primary contact and
non-primary contact exposure scenarios, EPA sets the number of microorganisms ingested to be
the same in both scenarios such that:
Dprimary ~ Dnon-primary
Thus, EPA can combine Equation 1 and Equation 2 to yield:
^non-primary X ^non-primary = Cprimary X ^primary (Equation 3)
Equation 3 represents two exposure scenarios (non-primary contact recreation on the left
and primary contact recreation on the right) where the combination of water quality and
incidental ingestion amount for each scenario result in the same illness risk. Because EPA seeks
to identify water quality during non-primary contact recreation that results in the same illness
risk as water quality during primary contact recreation, EPA rearranges Equation 3 to yield:
->org _ rorg 1primary
ru,y _ ru,y -primary fFmifltinn 4^
non-primary primary j '
r s r s in nn —r>rim nr-M
non-primary
Equation 4 specifies the concentration of pathogenic microorganisms in water during
non-primary contact recreation associated with the same illness risk as primary contact recreation
by multiplying the concentration of pathogenic microorganisms in water associated with the
illness rate specified in EPA's 2012 RWQC with the ratio of primary contact ingestion amount to
non-primary contact ingestion amount. However, EPA's 2012 RWQC for primary contact
recreation does not specify a concentration of pathogenic microorganisms in water, but rather a
concentration of FIB. Applying the assumptions described in Section 2.2 that increasing GI
illness associated with increasing FIB densities in human-impacted waters is due to increasing
concentrations of pathogens that cause GI illness and the dose-response relationship for
pathogens that cause GI illness in recreational waters is linear in the dose range expected to
occur in waters used for recreation, EPA can represent the concentration of pathogenic
microorganisms in water as directly proportional to the concentration of FIB. Such
7
-------
proportionality can be represented as a simple linear equation in two variables with a y-intercept
of 0 and a slope of k such that:
and
rorg _ , cfib
primary ~ ""primary * °primary
rorg , rFW
non-primary non-primary ^ unon-primary
the concentration of pathogenic microorganisms in ambient water during
primary contact recreation,
the concentration of pathogenic microorganisms in ambient water during
non-primary contact recreation,
the concentration of FIB in ambient water during primary contact
recreation,
the concentration of FIB in ambient water during non-primary contact
recreation,
the slope of the linear relationship between the concentration of
pathogens and the concentration of FIB in primary contact recreational
waters,
the slope of the linear relationship between the concentration of
pathogens and the concentration of FIB in non-primary contact
recreational waters.
Applying the assumption described in Section 2.2 that the relationship between the concentration
of pathogenic microorganisms and the concentration of FIB in recreational waters are the same
for primary contact and non-primary contact recreation, kprimary and knon_primary are equal.
Thus, EPA can represent the constant of proportionality under primary contact and non-primary
contact exposure scenarios as a single constant k such that:
rorg , rFlB
primary uprimary
and
rorg , CFIB
non-primary non-primary
Replacing C°rrfmary with k x C^fmary and replacing C^_pWmarywith k x C^Bn_primary in
Equation 4 yields:
8
where:
ror8
primary
-org
non-primary
nFIB
uprimary
nFIB
unon-primary
If
^primary
If
^non-primary
-------
7, y rFIB = k Y rFIB X primary fF filiation
n, ^non—primary primary , ^lAjuauuu )
1non-primary
Because the proportionality constant A: is on both sides of Equation 5, they cancel yielding:
rFIB rFIB Y. /Pr'mary fF filiation
^non-primary °primary T ^^uauun yjj
1 non-primary
Equation 6 shows that the concentration of FIB representing illness risk associated with
non-primary contact recreation equals the concentration of FIB representing the same illness risk
associated with primary contact recreation multiplied by the ratio of primary contact ingestion
amount to non-primary contact ingestion amount. When C^fmary equals a criterion value
provided in EPA's RWQC recommendations for primary contact recreation, C^^l_primary
equals an adjusted value for non-primary contact recreation with the same illness risk. Note that
Ipnmary is the amount of incidental ingestion of ambient water associated with primary contact
recreation, and Inon-primary is the amount of incidental ingestion of ambient water associated with
the non-primary contact recreational activities that are the focus of the analysis. Also note
Equation 6 is like multiplying a value for primary contact recreation with a multiplier as has been
common past state practice, except here the multiplier is derived from quantitative data
representing exposure during specific non-primary contact recreational activities. Furthermore,
Iprimary and Inon-primary can be specified in any appropriate unit of measure because they effectively
cancel (provided the units of measure for both values are the same). Section 3 discusses
considerations when choosing ingestion amount estimates for Equation 6.
3. Incidental water ingestion during different recreational activities
Applying the methodology from EPA's 2012 RWQC to non-primary contact recreation
using Equation 6 depends on quantitative data on the amount of incidental water ingestion
associated with recreation. The value Ipnmary represents the amount of incidental ingestion
associated with primary contact recreation as defined in EPA's 2012 RWQC, and the value
Inon-primary represents the amount of incidental ingestion associated the targeted non-primary
contact recreation. Several published studies provide ingestion amount estimates for a variety of
different recreational activities (DeFlorio-Barker et al., 2018; Dorevitch et al., 2011; Dufour et
al., 2006; Schets et al., 2011; Schijven & de Roda Husman, 2006; Stone, Harding, Hope, &
Slaughter-Mason, 2008; Suppes et al., 2014; USEPA, 2019a). These studies provide incidental
ingestion estimates for the following activities:
• Boating,
• Canoeing in calm water (i.e., no capsizing),
• Canoeing in turbulent water (i.e., with capsizing),
• Exercise swimming,
• Fishing,
• Kayaking in calm water (i.e., no capsizing),
• Kayaking in turbulent water (i.e., with capsizing),
• Leisure swimming,
• Occupational diving,
• Rowing in calm water (i.e., no capsizing),
9
-------
• Rowing in turbulent water (i.e., with capsizing),
• Sports diving with full face mask,
• Sports diving with ordinary face mask,
• Surfing,
• Swimming,
• Wading/splashing,
• Walking.
EPA's Exposure Factors Handbook (USEPA, 2019b) summarizes many of these studies and
compiles quantitative estimates of incidental ingestion provided by those studies in a collection
of tables.
The approach described in this white paper relies on accurately establishing the ratio of
incidental ingestion of ambient water associated with primary contact to the incidental ingestion
of ambient water associated with non-primary contact recreation. Thus, selecting an appropriate
matched pair of quantitative measurements for both primary and non-primary contact recreation
is essential. Because the epidemiological studies forming the basis of EPA's 2012 RWQC
describe exposure as swimming or wading, it is reasonable to use an incidental ingestion
estimate associated with swimming or wading as an appropriate value for I primary. EPA's
Exposure Factors Handbook lists a range of estimates of incidental ingestion associated with
primary contact recreation. EPA has also derived peer-reviewed ingestion rate estimates
associated with primary contact recreation acceptable for developing recreational water quality
criteria (USEPA, 2019a). However, EPA has not derived analogous ingestion rate estimates for
non-primary contact recreation with the same scientific rigor. At the time of this writing,
ingestion rate estimates for non-primary contact recreation are limited, with only one study
(Dorevitch et al., 2011) providing estimates of incidental ingestion associated with typical
non-primary contact recreational activities. Additional data on incidental ingestion of ambient
water during non-primary contact recreational activities may become available as interest in
implementing the approach proposed in this paper increases.
The approach described in this white paper depends on accurately establishing the ratio
of primary contact to non-primary contact incidental ingestion of ambient water. Thus, the
selection of values for I primary and Inon-primary should consider potential biases present in both
estimates. A variety of factors could potentially bias estimates of incidental ingestion associated
with recreation. Some sources of bias may be random (that is, inherently unpredictable such as
fluctuations in the readings of a measurement apparatus), whereas other sources of bias may be
systematic (that is, always affecting the results in a predictable direction). Sources of potential
bias include:
• Gender (e.g., female versus male),
• Age (e.g., children versus adults),
• Salinity (fresh waters versus marine waters),
• Study venue (surface waters versus pools),
• Measurement technique (cyanuric acid in urine versus categorical self-reported ingestion
amount such as drop, teaspoon, mouthful, shot glass, etc.),
• Definition of recreational activity (e.g., wading, bathing, playing, swimming, etc.),
10
-------
• Recreational activity specifications (e.g., any contact with water versus requiring head-
immersion),
• Statistic reported (e.g., arithmetic mean, geometric mean, median, 95th percentile, etc.),
• Unit of measurement (e.g., ml/hour, ml/day, or ml/event),
• Other study-specific uncontrolled confounding variables (either known, forgotten, or
unknown).
Because Equation 6 calculates an adjustment factor as the ratio of Ipnmary to 1non-primary, one
approach for choosing appropriate values for Ipnmary and Inon-primary is to choose a pair of values
with the same biases so that the biases cancel. In addition, units of measure for Ipnmary and
Inon-primary should be the same, should be appropriate for describing incidental ingestion of
ambient water during recreation, and should be consistent with the distribution of the underlying
data.
The value of Ipnmary represents the primary contact exposure scenario in the epidemiological
studies that was the basis of EPA's 2012 RWQC, and the value of Inon-primary represents the non-
primary contact exposure scenario of interest. Because the primary contact exposure scenario in
EPA's epidemiological studies was a combination of children and adults engaging in primary
contact recreation, Ipnmary should be a value that reflects overall incidental ingestion of both
children and adults engaging in primary contact recreation.
11
-------
References
Cabelli, V. J. (1983). Health Effects Criteria for Marine Recreational Waters. In. Cincinnati, OH:
U.S. Environmental Protection Agency.
DeFlorio-Barker, S., Arnold, B. F., Sams, E. A., Dufour, A. P., Colford, J. M., Jr., Weisberg, S.
B., . . . Wade, T. J. (2018). Child environmental exposures to water and sand at the beach:
Findings from studies of over 68,000 subjects at 12 beaches. J Expo Sci Environ
Epidemiol, 28(2), 93-100. doi:10.1038/jes.2017.23
Dorevitch, S., Panthi, S., Huang, Y., Li, H., Michalek, A. M., Pratap, P., . . . Li, A. (2011). Water
ingestion during water recreation. Water Res, 45(5), 2020-2028.
doi: 10.1016/j.watres.2010.12.006
Dorevitch, S., Pratap, P., Wroblewski, M., Hryhorczuk, D. O., Li, H., Liu, L. C., & Scheff, P. A.
(2012). Health risks of limited-contact water recreation. Environ Health Perspect, 120(2),
192-197. doi: 10.1289/ehp. 1103934
Dufour, A. P. (1984). Health Effects Criteria for Fresh Recreational Waters. In. Cincinatti, OH:
U.S. Environmental Protection Agency.
Dufour, A. P., Behymer, T. D., Cantu, R., Magnuson, M., & Wymer, L. J. (2017). Ingestion of
swimming pool water by recreational swimmers. J Water Health, 75(3), 429-437.
doi:10.2166/wh.2017.255
Dufour, A. P., Evans, O., Behymer, T. D., & Cantu, R. (2006). Water ingestion during
swimming activities in a pool: a pilot study. J Water Health, 4(4), 425-430. Retrieved
from https://www.ncbi.nlm.nih.eov/pubmed,
Federal Water Pollution Control Administration. (1968). Water Quality Criteria. Report of the
National Technical Advisory Committee to the Secretary of the Interior. (800-R-68-900).
Washington, DC: Author
Graciaa, D. S., Cope, J. R., Roberts, V. A., Cikesh, B. L., Kahler, A. M., Vigar, M., . . . Hlavsa,
M. C. (2018). Outbreaks Associated with Untreated Recreational Water - United States,
2000-2014. MMWRMorbMortal Wkly Rep, 67(25), 701-706.
doi: 10.15585/mmwr.mm6725al
Russo, G. S., Eftim, S. E., Goldstone, A. E., Dufour, A. P., Nappier, S. P., & Wade, T. J. (2020).
Evaluating health risks associated with exposure to ambient surface waters during
recreational activities: A systematic review and meta-analysis. Water Res, 176, 115729.
doi: 10.1016/j.watres.2020.115729
Schets, F. M., Schijven, J. F., & de Roda Husman, A. M. (2011). Exposure assessment for
swimmers in bathing waters and swimming pools. Water Res, 45(1), 2392-2400.
doi: 10.1016/j.watres.2011.01.025
12
-------
Schijven, J., & de Roda Husman, A. M. (2006). A survey of diving behaviour and accidental
water ingestion among Dutch occupational and sport divers to assess the risk of infection
with waterborne pathogenic microorganisms. Environ Health Perspect, IJ4(5), 712-717.
doi:10.1289/ehp.8523
Stone, D. L., Harding, A. K., Hope, B. K., & Slaughter-Mason, S. (2008). Exposure assessment
and risk of gastrointestinal illness among surfers. J Toxicol Environ Health A, 77(24),
1603-1615. doi:l0.1080/15287390802414406
Suppes, L. M., Abrell, L., Dufour, A. P., & Reynolds, K. A. (2014). Assessment of swimmer
behaviors on pool water ingestion. Journal of Water and Health, 12(2), 269-279.
doi:10.2166/wh.2013.123
USEPA. (1986). Ambient Water Quality Criteria for Bacteria - 1986. (440-5-84-002).
Washington DC: Author
USEPA. (2009). Report on 2009 National Epidemiologic and Environmental Assessment of
Recreational Water Epidemiology Studies. (EPA-600-R-10-168). Washington, DC:
Author Retrieved from https://www.epa.gov/sites/production/files/2019-
Q3/documents/report-2QQ9-national-epidemiologic-studies.pdf
USEPA. (2012a). Microbial Risk Assessment Guideline: Pathogenic microorganisms with focus
on food and water. (EPA/100/J-12/001). Washington DC: Author
USEPA. (2012b). Recreational Water Quality Criteria. (820-F-12-058). Washington DC: Author
Retrieved from https://www.epa.gov/sites/production/files/2015-
10/dociiM ents/rwq c2012. pdf
USEPA. (2019a). Recommended Human Health Recreational Ambient Water Quality Criteria or
Swimming Advisories for Microcystins and Cylindrospermopsin. (822-R-19-001).
Washington DC: Author Retrieved from
https://www.epa.gov/sites/production/files/2Q19-Q5/documents/hh-rec-criteria-habs-
document-2 [
USEPA. (2019b). Update for Chapter 3 of the Exposure Factors Handbook. Ingestion of Water
and Other Select Liquids. (600-R-18-259F). Washington, DC: Author Retrieved from
https://www.epa.gov/expobox/exposiire-factors-handbook-chapter-3
Wade, T. J., Calderon, R. L., Brenner, K. P., Sams, E., Beach, M., Haugland, R., . . . Dufour, A.
P. (2008). High sensitivity of children to swimming-associated gastrointestinal illness:
results using a rapid assay of recreational water quality. Epidemiology, 19(3), 375-383.
doi: 10.1097/EDE.0b013e318169cc87
Wade, T. J., Calderon, R. L., Sams, E., Beach, M., Brenner, K. P., Williams, A. H., & Dufour, A.
P. (2006). Rapidly measured indicators of recreational water quality are predictive of
swimming-associated gastrointestinal illness. Environ Health Per spect, 114(1), 24-28.
doi:10.1289/ehp.8273
13
-------
Wade, T. J., Pai, N., Eisenberg, J. N., & Colford, J. M., Jr. (2003). Do U.S. Environmental
Protection Agency water quality guidelines for recreational waters prevent
gastrointestinal illness? A systematic review and meta-analysis. Environ Health Perspect,
777(8), 1102-1109. doi:10.1289/ehp.6241
Wade, T. J., Sams, E., Brenner, K. P., Haugland, R., Chern, E., Beach, M., . . . Dufour, A. P.
(2010). Rapidly measured indicators of recreational water quality and swimming-
associated illness at marine beaches: a prospective cohort study. Environ Health, 9, 66.
doi: 10.1186/1476-069X-9-66
Xue, J., Zartarian, V., Moya, J., Freeman, N., Beamer, P., Black, K., . . . Shalat, S. (2007). A
meta-analysis of children's hand-to-mouth frequency data for estimating nondietary
ingestion exposure. Risk Anal, 27(2), 411-420. doi: 10.1111/j. 1539-6924.2007.00893.x
14
------- |