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JUN 2 0 1991
STATUS REPORT ON DEVELOPMENT OF REGULATIONS FOR
DISINFECTANTS AND DISINFECTION BY-PRODDCTS
The purpose of this document is to indicate the status of
regulation development for the disinfectants (Ds) and
j? disinfection by-products (DBFs) and to solicit feedback from the
^ public. Previously, EPA made available to the public a
^s. "strawroan" rule (October 1989) and a conceptual framework for
jj developing these regulations (December 1990).
\h. This document reflects EPA's current thinking on how the
*Y criteria for the D/DBP regulations are evolving. The document
consists of four sections: 1) overview of anticipated general
requirements of the rule and major issues, 2) fact sheet on the
status of pertinent analytical methods, 3) fact sheet on the
status of health effects information, and 4) draft compliance
monitoring requirements.
EPA anticipates adhering to the following schedule in
developing the D/DBP regulations:
Agency approval of intent
and scope of regulations:
Distribute draft rule
to interested public:
Propose rule:
Promulgate rule:
December 1991
February 1992
June 1993
June 1995
The information contained herein has not undergone formal
Agency review. It is meant to elicit thoughts and information
from the public to assist EPA in development of the regulations.
EPA solicits comment on all the information and criteria
described herein. All comments received by October 15, 1991 will
be considered in the development of the Draft Rule. Comments
received after November 15, 1991 will be considered in the
development of the Proposed Rule. Comments should be sent to:
Stig Regli - D/DBP Regulations
OGWDW (WH-550D) -
USEPA
401 M St., SW
Washington, DC 20460
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HEADQUARTERS LIBRARY
ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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OVERVIEW OF ANTICIPATED GENERAL REQUIREMENTS
AND MAJOR ISSUES
GENERAL REQUIREMENTS
Applicability
The D/DBP regulations would apply to all public water systems
(including noncommunity systems) using disinfection and serving
non-transient populations. This is unlike the current maximum
contaminant level (MCL) for total trihalomethanes (TTHMs) which
only pertains to systems serving more than 10,000 people.
Compounds Likely To Be Regulated With MCLs1
trihalomethanes (THMs)2 - chloroform, bromodichloromethane,
chlorodibromomethane, bromoform
haloacetic acids (HAs)3 - trichloroacetic acid,
dichloroacetic acid
chloral hydrate
brornate
chlorine
chloramin'es
chlorine' dioxide
chlorate
chlorite
1 This .list of compounds is significantly shorter than that
included in the 1989 "strawman" rule. Some of the original
compounds have been deleted because they do not appear to pose
significant health risk at levels that occur in drinking waters
(e.g., haloacetonitriles, chloropicrin). Other compounds have
been deleted because their health risks will not be adequately
characterized in time for this regulation. Such compounds may be
regulated at a future date (e.g., certain aldehydes and organic
peroxides) when more data become available.
2 Three options are being considered: 1) MCLs for each of the
four THMs, 2) an MCL for TTHMs, and 3) an MCL for each of the
THMs and an MCL for TTHMs (which may be different from the sum of
the individual THMs). Individual THMs are being considered
because their health risks are significantly different from each
other (see fact sheet on health effects), and the technical
feasibility for limiting their formation can vary greatly for
each of the compounds, depending upon source water quality. An
MCL for TTHMs is being considered because of the precedent
already established with the current TTHM standard, and to act as
a surrogate regulation to limit other DBFs.
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3 Three options are being considered: 1) HCLs for
trichlbroacetic acid and dichloroacetic acid; 2) an MCL for
total HAs including mono-, di-r and tri-chloroacetic acid?
monobromo and dibromo acetic acid; and bromochloroacetic acid;
and 3) the combination of options 1 and 2. A limit for total HAs
is being considered because all the compounds can be measured at
the same time using the same analytical method for no additional
cost. A limit for total HAs would act as a surrogate to limit
production of other HAs and DBFs for which health risks are not
yet determined.
MAJOR ISSUES
Risk Trade-offs in Controlling for Pathogenic Organisms
Traditionally we have set drinking water standards for
contaminants at the lowest possible number which is technically
and economically feasible to achieve for most large systems.
However, the Agency is in the process of reassessing the use of
costs and cost-effectiveness for setting MCLs (e.g., see proposed
Radionuclides Rule, June 17, 1991). In the case of regulating
specific DBFs and disinfectants, setting an MCL based on what is
technically and economically feasible to achieve raises several
concerns.
Our goal is to ensure that drinking water remains
microbiologically safe at the limits we set for disinfection by-
products (DBFs) and disinfectants (Ds). Disinfection is
essential for protection from waterborne disease. Therefore, we
may have to accept greater risks from Ds/DBPs than for other
contaminants EPA regulates. We are attempting to develop
standards which minimize risk from both Ds/DBPs and pathogenic
organisms.
To properly address this issue we would like to'answer key
questions during the development of our Proposed Rule:
* What are the uncertainties associated with defining
microbial and D/DBP risks?
• How can we compare these risks with one another?
What levels of DBP/D risk and microbiological risk are
we willing to accept and at what cost?
What are the most practical criteria available for
defining the achievement of acceptable levels of risk
in this rule?
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use of Alternative Disinfectants to Limit Chlorination DBFs
Certain combinations of alternative disinfectants to
chlorine (e.g., ozonation and chloramines) can provide excellent
disinfection of pathogens and greatly limit the formation of DBFs
typical of chlorination such as THMs. However, we currently do
not have a good understanding of the by-products formed from
alternate disinfectants and of some of their associated health
risks. EPA does not want to promulgate a standard which
encourages the industry to switch to alternative disinfectants
unless it is likely that their by-products pose substantially
less risk than those from the by-products of chlorination.
Other concerns from alternative disinfectants relate to
microbiological issues. For example, depending on the source
water type and other technologies used, switching to ozone may
increase availability of assimilable organic material and
subsequently increase, with unknown risk, bacterial populations
in distribution systems.
Different concerns pertain to chloramines. Since
chloramines are a weak disinfectant, their use in lieu of
chlorine for primary disinfection might significantly increase
risk from microbial disease.
We are confronted with a unique situation where adoption of
technologies to reduce one type of risk may increase another type
of risk. Our ability to characterize these differences in risk
is still fairly crude.
Integration With the Surface Water Treatment Rule (SWTR1
The SWTR requires systems using surface water to achieve at
least 99.9% (3-log) and 99.99% (4-log) removal/inactivation of
Giardia and viruses, respectively, although many systems now
achieve much greater removals. EPA guidance to the SWTR
recommends greater than 3/4-log removal/inactivation' for poor
source waters. EPA would not like to reduce that existing level
of protection, unless there is an obvious overall risk reduction,
taking by-products and disinfectants into consideration.
Amendments to the SWTR, which would require higher levels of
removal/inactivation for systems with poor source waters than the
3/4-log minimum, may be necessary to ensure adequate protection
from pathogens while systems comply with the new regulations for
disinfectants and disinfection by-products.
Best Available Technology
The Safe Drinking Water Act requires EPA to specify a
maximum contaminant level goal (MCLG) for each contaminant that
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it regulates. EPA must set the MCL as close to the MCLG as is
technically and economically feasible to achieve and must specify
in the rule such best available technology (BAT). Systems unable
to meet the MCL after application of BAT can get a variance.
Systems that obtain a variance roust meet a schedule approved by
the State for coming into compliance. Systems are not required
to use BAT in order to comply with the MCL but can use other
technologies as long as they meet all drinking water standards
and are approved by the State.
How BAT is defined will determine the level at which MCLs
are set for DBFs. Because health risks from by-products of
alternate disinfectants are not as yet well characterized as they
are for by-products of chlorination, it may be appropriate to
define chlorination for primary disinfection and certain
precursor removal technologies as BAT under this rulemaking.
Examples of such technologies include: a) conventional treatment
optimized for DBF precursor removal, b) granular activated
carbon (GAC) as a filter media replacement, c) GAC following
filtration, and d) membrane filtration. Other technologies for
BAT consideration, depending upon the source water quality,
include conventional treatment with use of alternate
disinfectants such as ozone for primary disinfection and
chloramines for residual disinfection.
sThe cost and performance of the above technologies will vary
greatly depending upon how they are designed and operated. The
technical and economic feasibility of using these technologies to
achieve different finished water quality targets (potential MCLs)
can be greatly influenced by source water quality and system
size.
Approach to SettingMCLs
IPA is attempting a risk/risk trade-off analysis between
exposures from pathogens and Ds/DBPs for different regulatory
options. This will help us arrive at the most cost-effective
rule and determine how BAT should be defined. In order to
resolve the problems of risk assessment comparison between these
two types of health concerns, we are trying to determine the
regulatory options which lead to the lowest total cost (see
Figure 1). This approach should clearly define the uncertainties
of risk for different options and help us to define how much we
would be willing to pay to avoid such uncertainties.
Although we are in the early stages of our analysis, we
believe the following outcomes will become evident: a) there are
significant uncertainties in the risk from unknown DBFs in the
lowest-cost treatment technology options, (e.g., conventional
filtration processes followed by ozone with chloramines as a
residual disinfectant); and b) the technologies that can
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minimize exposure to risks from known and unknown pathogens and
DBFs (e.g., filtration followed by granular activated carbon or
membrane filtration with disinfection) are significantly more
costly than technologies using conventional treatment and
alternative disinfectants.
Lack of data pertaining to risk/risk trade-offs between
pathogens and Ds/DBPs will significantly compromise our ability
to estimate optimal regulatory targets within the current
regulatory schedule (proposing in June 1993 and promulgating in
June 1995). The level of stringency that is practical to achieve
for chlorination DBFs at affordable costs is associated with
potential increased risks from exposure to pathogens and DBFs
from alternate disinfectants. Several regulatory strategies
could address this issue within the current regulatory time
frame.
Possible Regulatory Strategies
One strategy to address the uncertainty in risk trade-offs
between protection from pathogens versus exposure to DBFs and
disinfectants is to develop a regulation which defines the most
effective DBF precursor removal technologies as BAT, e.g.,
granular activated carbon following filtration and membranes
filtration. However, such a regulation would minimize health
risk concerns at substantial costs without us knowing whether
other less costly technologies could provide similar benefits,
e.g., conventional treatment with alternative disinfectants.
Such a regulation would also create pressure for a large number
of variances for small systems.
Alternatively, we could develop a less stringent regulation
until we are able to obtain more data and the cost-effectiveness
of using higher cost versus lower cost treatment technologies
becomes clearer. This latter approach would involve a two-phase
regulation of potentially increasing stringency as more data
become available.
Under the scenario of a two-phase regulation, BAT in the
first phase of regulation (promulgation in June 1995) might be
defined as conventional treatment optimized for precuror removal
using chlorination for primary disinfection. Systems would have
a variety of technical options other than the BAT to achieve
compliance. The MCL would be based on what is feasible for the
BAT to achieve on a selected source water quality. The source
water quality selected for the basis of BAT determination might
be that which represents the central tendency of source water
quality in the U.S. regarding DBF precursor and pathogen
occurrence,
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BAT in the second phase of regulation (promulgation in June
2000) might be defined as filtration followed by GAC or membrane
filtration and/or possible use of alternative disinfectants. If
systems adopted precursor removal technologies such as granular
activated carbon or membrane filtration in Phase I, they could be
assured of being able to meet more stringent limits that might be
set in Phase II. This strategy could facilitate adoption of the
most cost-effective technologies for controlling DBFs as well as
other regulated contaminants.
The total cost analysis mentioned above will help us
understand the merits of different regulatory options, determine
how to define BAT, and provide insight on whether to proceed with
a two-phased regulatory approach. EPA intends to share the
outcome of this analysis with the public in a Draft Rule
anticipated to be released at the end of February 1992. EPA
solicits comment on the above strategies and welcomes suggestions
for other approaches to address the aforementioned issues.
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FACT SHEET - ANALYTICAL METHODS
DISINFECTANTS AND DISINFECTION BY-PRODUCTS
June 1991
Methods for measuring disinfectant residuals and the
concentrations of disinfection by-products in finished
drinking water are under various stages of development. A
summary of the status of the methods is presented below.
Background
Before a Maximum Contaminant Level (MCL) can be set for
a drinking water contaminant, there must be at least one
reliable method for measuring the concentration of the
contaminant. In order for a method to be useful, it must
provide reasonably precise and accurate measurements of the
analyte at concentrations near the MCL. The method must be
written in a standard format and it must undergo
multilaboratory validation studies to determine
interlaboratory performance. Performance evaluation (PE)
samples must be prepared for use in the certification
process as well as in the generation of interlaboratory
performance data.
Summary of Analytical Methods
Disinfectants;
Chlorine and Chloramines. The following methods were
specified in the Surface Water Treatment Rule (SWTR) for
measuring free chlorine and combined chlorine (chloramines}
residuals in disinfected drinking water: Method 408C
(Amperometric Titration Method); Method 408D (DPD Ferrous
Titrimetric Method); Method 408E (DPD Colorimetric Method);
and Method 408F (Leuco Crystal Violet Method) as set forth
in Standard Methods for the Examination of Water and
Wastewater. 1985, American Public Health Association et al.,
16th edition. The State Regulatory Agencies were given the
option to approve the use of DPD colorimetric test kits.
The applicability of these methods will be reevaiuated for
the Groundwater Disinfection Rule (GWDR). Chlorine is
included in current EPA performance evaluation (PE) studies.
Issues: Interferences and other method limitations
must be examined. New methods may need to be developed.
Guidance on defining what constitutes a "detectable"
chlorine residual may need tp be written, since the
sensitivity varies with analytical method. The cited
methods are also subject to interferences that could result
in false positives.
There is no mechanism to ensure the free and combined
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chlorine residual measurements are being done properly.
Chloramine is not yet included in PE studies.
References to methods need to be updated to the 17th
edition of standard Methods forthe Examination of Water and
Wastewater. Provisions must be made for continual updating
as new versions are published.
Chlorine Dioxide. The SWTR specified the following
methods for determining chlorine dioxide residual
concentrations: Method 410B (Amperometric Method) or Method
4IOC (DPD Method) as set forth in Standard Methods for the
Examination ofWater and Wastewater. 1985, American Public
Health Association et al., 16th edition.
Issues: Since EPA is developing separate risk
assessments for chlorine dioxide and the inorganic by-
products (chlorite and chlorate) as part of the Groundwater
Disinfection Rule (GWDR) and the Disinfection By-product
(DBF) Rule, the chlorine dioxide methods must be reexaminecl
to determine their applicability. The methods may not be
sensitive enough to reliably measure the analytes at levels;
considered to have no adverse health effects.
Chlorine dioxide is not yet included in PE studies.
References to methods need to be updated to the 17th
edition of Standard Methods for the Examination of Water and
Wastewater. Provisions must be made for continual updating
as new versions are published.
Ozone. The SWTR specified the residual disinfectant
concentrations for ozone must be measured by the Indigo
Method as set forth in Bader, H., Hoigne, J., "Determination
of Ozone in Water by the Indigo Method; A Submitted Standard
Method"; OzoneScience and Engineering. Vol. 4, pp. 169-176,
Pergamon Press Ltd., 1982, or automated methods which are
calibrated in reference to the results obtained by the
Indigo Method. Two on-line measurement techniques are under
development through the AWWA Research Foundation and they
will be evaluated for applicability. Ozone residuals*.cannot
be maintained in water, but monitoring of ozone residual and
dose is necessary for determining CT credits.
Issues: The SWTR reference should be updated to Method
4500.03B as set forth in Standard Methods for the
Examination of Water and Wastewaterf 1989, American Public
Health Association et al., 17th edition.
Ultraviolet Radiation. Since UV radiation is an
effective disinfectant for viruses, EPA intends to allow the
use of UV as a primary disinfectant in the GWDR.
Issue: One of the current limiting factors in its use
is the inability to continuously monitor the UV dose being
applied in the to the water by a standard method.
Development of a UV sensor will be necessary before
widespread use of UV can be encouraged.
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Disinfection By-products:
Trihalome thanes, Haloacetonitriles, Chloropropanones,
Chloropicrin, & Chloral Hydrate. There are 2 methods
approved for compliance monitoring of THM concentrations in
finished drinking water (EPA Methods 501.1 and 501.2).
These methods were published in the Federal Register in
1979, as part of the THM Rule. Due to many advances in gas
chroma tography, these methods are based oh obsolete
chroma tography technology. Three additional methods are
EPA-approved for measuring THM concentrations (EPA Methods
502, 524.1 and 524.2), but they have not been designated as
compliance monitoring methods. The EPA is preparing a
Federal Register notice to allow their use for compliance
monitoring.
The EPA has also developed a new liquid/liquid
extraction method, which can be used to measure 4
haloacetonitriles (HANs) (trichloroacetonitrile [TCAK],
dichloroacetonitrile [DCAN], bromochloroacetonitrile [BCAN],
and dibromoacetonitrile [DBAN]), 2 chloropropanones (1,1-
dichloropropanone [DCP], and 1,1,1-trichloropropanone
[TCP] ) , chloropicrin (CP) , and chloral hydrate (CH) , as well
as the THMs. EPA Method 551 was published in Methods for
the Determination of Organic Compounds, Supplement 1.
EPA/600/4-90/020, July 1990, and several laboratories are
using it to measure THMs and the other analytes. The method
involves adjusting the ionic strength of the sample,
extracting the analytes into methyl -tertiary-butyl ether
(MTBE) , and analyzing the extract by capillary column gas
chromatography (GC) with electron capture detection (BCD) .
In some matrices, a separate sample must be collected
for chloral hydrate, because the regular dechlorinating
agent interferes with its analysis.
THMs, HANs, DCP, and TCP are included in the PE
studies. THMs, BCAN, TCP, and CH standards are available
through EPA cooperative research and development agreements
(CRADAs) .
Method detection limits: All of the methods can easily
meet MCL measurement requirements for THMs. The MDLs
published in Method 551 are < 0.1 M9/L, and most
laboratories will be able to reliably quant i tat e down to 1-5
Issues: Method 551 includes a preservation technique
for HANs, CP, DCP, and TCP that is not viable for field use.
(The procedure involves removing the free chlorine using
NH4C1, then adjusting the sample pH to 4.5 using Hcl. Note:
It is critical that the Ph not be lowered below this level,
because free chlorine is again formed.) Further work on a
preservation technique will be needed, if these compounds
are to be regulated by setting MCLs.
Mixed standards should be included as part of the EPA
CRADAs, if these compounds are regulated.
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At this time EPA does not anticipate setting MCLs for
HANs, CP, DCP and TCP.
There is very little data on the stability of the non-
THM analytes in water samples, so sample holding times
cannot be established.
CH and CP are not included in PE studies
CH analyses are complicated by the fact that working
standards are not stable for longer than 1-2 weeks.
Haloacetic Acids fc Chlorophenols. The EPA has
developed a method to measure the concentrations of 6
haloacetic acids (monochloroacetic acid [MCAA],
dichloroacetic acid [DCAA], trichloroacetic acid [TCAA],
monobromoacetic acid [MBAA], dibromoacetic acid [DBAA], and
bromochloroacetic acid [BCAA]) and 2 Chlorophenols (2,4-
dichlorophenol [24DCPh] and 2,4,6-trichlorophenol [246TCPhJ.
The method involves an acidic extraction with MTBE,
conversion of the analytes to methyl esters using
diazoroethane, and analysis by capillary column GC/ECD. EPA
Method 552 was published in Methods for the Determination of
Organic Compounds in Drinking Water. Supplement 1.
EPA/600/4-90/020, July 1990. It is in use at several
laboratories around the country. The method incorporates an
option of using a microextraction technique developed by
Metropolitan Water District of Southern California. The PE
studies include 5 of the HAAs and 246TCPh.
Method detection limits (MDLs): The MDLs published in
the method are < 1.0 M9/L/ and most laboratories will
probably be able to reliably quantitate down to the 5-10
jig/L range for the HAAs.
Issues: The method requires the use of diazomethane,
which is a problem for some laboratories due to safety
concerns. An alternative derivatizing procedure is under
development.
EPA has very little data on the stability of these
compounds. Additional data on the HAAs are being collected,
so EPA can specify a sample holding time. '• •
Some drinking waters contain a contaminant (not yet
identified) that interferes with the analysis of MCAA.
No commercial standards are available for BCAA or the
other mixed bromo-chloro acetic acids that are probably also
amenable to this method. Standards will have to be
developed for these compounds.
Mixed standards of these compounds will be prepared as
part of the new EPA CRADAs. Single compound standards
should also be considered.
The method is subject to interferences that
chromatograph in the same general areas as the
Chlorophenols. This complicates the analysis and sometimes
requires the use of mass spectrometry to verify that the
peak is not a chlorophenol.
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cyanogen Chloride. EPA Method 524.2, published in
Methods forthe Determination of Organic Compounds in
Drinking Water. EPA/600/4-88/039. December 1988, can be used
to measure CNCl concentrations in water, if the
dechlorinating/preservation technique is modified. Ascorbic
acid is the only dechlorinating agent that can be used with
samples for CNCl analysis, and the sample should not be
acidified with HCl. Analyses involve the use of purge and
trap (P&T), capillary column GC with mass spectrometry (MS).
Laboratories experienced in analyzing drinking water for
vinyl chloride will have the least difficulty successfully
analyzing for cyanogen chloride.
Method detection limits: EPA can quantitate down to
0.3 /ig/L.
Issues: This compound is not stable in some water
matrices. Determining a preservative for CNCl will require
extensive research.
Cyanogen chloride is not included in current PE
studies.
Some purge & trap units cannot be used for CNCl
analyses because too much water is carried to the GC column.
Efforts to eliminate this problem are under way.
Colorimetric methods are available for this compound,
but they don't have the sensitivity required for drinking
water. There is no research planned in this area, unless it
is identified as a high priority.
Aldehydes. The draft EPA Method 554 can be used to
measure the concentrations of carbonyl compounds in drinking
water using high performance liquid chromatography (HPLC).
The sample is buffered to pH 3, derivatized with 2,4-
dinitrophenylhydrazine (DNPH), and passed through reverse
phase C18 bonded silica cartridges. Ethanol is used to
elute the analytes and they are quantitated using HPLC.
In addition to that method, a gas chromatography (GC)
method is being used by EPA for treatment, occurrence, and
monitoring studies. The method is based on the procedure
described by Glaze et.al. in Environ. Sci. Technol.. Vol 23,
838-847, 1989. The aldehydes are converted to oximes via an
aqueous phase derivatization with O-(2,3,4,5,6-
pentafluorobenzyl)hydroxylamine hydrochloride (PFBOA) and
the oximes are extracted into hexane. Quantitation is
accomplished via capillary column GC/ECD or GC/MS.
Method detection limits: The HPLC method lists MDLs in
the range of 5-70 pg/L (formaldehyde « 8; acetaldehyde =
69), and the GC method provides MDLs around 1 Mg/L.
Issues: Sample stability is a major concern for this
method, and will require extensive research before it is
resolved.
The HPLC method may not be sensitive enough for
drinking water applications. If MCLs are set for certain
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aldehydes and they are < 50 M9/L for individual compounds,
the GC method may be the only method available.
The HPLC method has not been used to measure glyoxal
and raethylglyoxal concentrations.
It is unlikely aldehydes can be included in PE studies
in the near future, due to stability and analytical method
problems.
Chlorite, Chlorate, Bromate, i lodate. EPA has a draft
ion chromatography (1C) method (EPA Method 300.OB) for
measuring chlorite, chlorate/ and bromate. A flow injection
analytical technique is also under development. Work is
under way to include iodate in the 1C method. Chlorite,
chlorate, and bromate will be added to PE studies in near
future.
Method detection limits: The method lists MDLs in the
range of 3-20 ng/L (chlorate < chlorite < bromate).
Issues: Stability problems have been identified with
chlorite, so the method specifies immediate analysis. Work
is in progress to determine a preservative for this analyte.
lodate requires additional study before it can be added
to PE studies.
It is unlikely that any of these contaminants can be
reliably quantified at < 10 #g/L in complex drinking water
matrices using the current method. Research is underway to
lower detection limits.
organic Peroxides. One of the concerns about the use
of ozone as a primary disinfectant is the theoretical
possibility of forming organic peroxides. Since analytical
methods sensitive enough to detect these types of compounds
are not available, no one has been able to demonstrate
whether they occur. EPA is determining the feasibility of
developing methods based on electrochemical techniques for
detecting these compounds. An internal report will be
available in 1 year. If development of a method(s) is
feasible, this will be a long range research project...
MX [3-chloro-4(dichloroaethyl)5-hydroxy-2(5H)
furanone]. The analytical procedures used to measure the
concentrations of this and similar compounds in drinking
water are too complex for routine use. Extensive research
would be required, with no guarantee of success, to develop
a "rugged" method for MX. No research on methods is
planned.
N-Organochloramines & Nitrosamines. There are no
methods available to measure the concentrations of these
compounds at the levels they may be expected to occur in
drinking water. Before extensive research in this area can
occur, specific target compounds must be identified. Method
development will focus on techniques useful in research type
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situations, since the goal is to determine whether these
types of compounds are formed during the treatment of
drinking water. If research indicates they are formed at
concentrations of health significance, then further methods
development work may be necessary.
N-oxy Compounds. Chloropicrin is the only compound of
this type for which an analytical method is available.
Research indicates chloropicrin forms in higher
concentrations when ozonation is used during the treatment
process. There is concern that other compounds may also be
formed as the result of ozonation followed by chlorination
or chloramination. A method for detecting these types of
compounds is needed to assure they are not being formed at
concentrations of health significance. This is a long term
research project.
Surrogate Measurements;
EPA is considering the use of surrogate measurements as
indicators of situations in which DBF monitoring
requirements may be reduced or waived. Some of the
surrogates being considered are described below.
Total organic Halide. A study of 30 drinking water
utilities treating surface water indicated total organic
halide (TOX) may be a good surrogate for the sum of the
chlorination by-products being considered for regulation.
If this analysis is used as a screening technique or
factored into the monitoring requirements of the DBF Rule in
some other way, EPA may need to evaluate the performance of
EPA Method 450.1 and include TOX in the PE studies. The THM
samples currently included in PE studies might be applicable
for TOX measurements and should be evaluated.
Source Water Quality. The organic load of the source
water (as indicated by measurements of either dissolved
organic carbon [DOC], or nonpurgeable organic carbon [NPOC]
concentrations or UV absorbance at 254 nm) provides
information about DBP precursors. If such measurements are
used/as a basis for granting monitoring waivers, the methods
may need to be evaluated.
Bromide ions in source water react with ozone or
chlorine to form such DBPs as bromate, bromoform, and
dibromoacetic acid. Bromide concentrations can be measured
using ion chromatography.
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FACT SHEET - HEALTH EFFECTS
DISINFECTANTS AND DISINFECTION BY-PRODUCTS
June 1991
The Environmental Protection Agency (EPA) is in the
process of assessing the potential health risks of several
drinking water disinfectants and their by-products in
anticipation of proposing regulations in June 1993. The
following is a summary of the health assessment of these
compounds and steps that need to be followed prior to
proposal.
Background
The EPA is responsible for the protection of public
water supplies as mandated by the Safe Drinking Water Act
(SDWA) of 1974, amended in 1986. The SDWA requires EPA to
regulate those contaminants that may pose an adverse human
health risk and are known or anticipated to occur in
drinking water. For each contaminant considered for
regulation, the EPA determines a Maximum Contaminant Level
Goal (MCLG) and a Maximum Contaminant Level (MCL) or, if
monitoring is not feasible, a treatment technique.
The MCLG is a nonenforceable health-based goal that is
considered protective of human health over a lifetime
exposure and which provides an adequate margin of safety.
The EPA has established a three-category approach .for
setting MCLGs. Factors such as weight of evidence for
carcinogenicity, cancer potency, exposure, pharmacokinetics
and mechanism of action influence the category in which a
contaminant is placed. For category I contaminants,, there is
strong evidence of a carcinogenic risk to humans from a
drinking water source; thus the MCLG is set at zero. For
category II contaminants, there is limited evidence of a
carcinogenic risk to humans exposed to the contaminant in
drinking water. The MCLG determined for this group is based
on the Reference dose (RfD) approach (described below) with
an additional uncertainty factor applied to account for
possible carcinogenicity. If adequate data are not available
to calculate an RfD, then the MCLG is set using cancer risk
information. For contaminants with inadequate or no evidence
of carcinogenicity to humans via drinking water, the MCLG is
determined from the RfD approach.
The RfD represents a daily oral exposure to a
contaminant that would not result in an adverse health
effect in the human population over a lifetime of exposure.
The RfD incorporates a margin of safety and protects
sensitive members of the population. The RfD is calculated
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from a no- or lowest-observed-adverse-effeet level
identified from an appropriate study in humans or animals,
and divided by an uncertainty factor. The uncertainty factor
accounts for differences in response to toxicity within the
human population and between humans and animals, as well as
the quality and totality of the data base and the type of
toxic effect. To represent a drinking water exposure, the
RfD is adjusted for an adult drinking 2 liters of water per
day as an average over a lifetime. The resulting value is
called the Drinking Water Equivalent Level (DWEL). The DWEL
assumes that all of one's exposure comes from a drinking
water source. However, exposure to a given contaminant may
also come from other sources; thus, the DWEL is adjusted to
reflect a known or assumed level of exposure to the
contaminant from a drinkinj water source. This value
represents the HCLG.
The MCL is then set as close to the HCLG as feasible,
based on the ability of different technologies to measure
and remove the contaminant from water. Often the MCL will
equal the MCLG. In cases where the MCLG is set at zero, the
MCL will usually fall in an excess cancer risk range of one
in ten thousand to one in one million (10~4 to 10"6) .
Summary of Health Information
Disinfectants;
Chlorine. Most commonly used disinfectant. It is a
strong oxidizing agent and reacts with water to form
hypochlorous acid and hypochlorite. In addition, chlorine
reacts with organic matter in the water (e.g., humic and
fulvic acids) to form a number of oxidation by-products.
Health effects: Toxic effects observed in animal
studies with chlorine or hypochlorite include decreased
organ and body weights, and changes in serum enzymes.' These
effects were observed in animals exposed to much higher
levels of chlorine than would be found in drinking water.
Early reports indicated effects on serum cholesterol, these
findings were not confirmed in follow-up studies by the same
authors. A two-year bioassay with chlorinated water in
rodents reported a significant increased incidence of
mononuclear cell leukemia in female rats exposed only to the
mid-dose. The incidence does not appear to be dose-related
for this lesion.
Epidemiology studies have associated chlorinated water
with an increased risk of bladder, colon and rectal cancer
in persons exposed for 40 years or more. The International
Agency for Research on Cancer (IARC), however, recently
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determined that these data are inadequate to classify the
carcinogenicity potential of chlorinated drinking water to
humans. They recommended further research to clarify this
issue.
Risk Assessment: The EPA has not determined an RfD for
noncancer health effects or cancer assessment for chlorine
at this time. Health effects do not appear to be associated
with typical residual chlorine levels in public water
supplies.
Future steps: Review new data on reproductive and
immunological effects. Determine RfD for chlorine in Summer,
1991; initiate review of carcinogenicity of chlorinated
water in Summer, 1991. Science Advisory Board review
possibly in October, 1991.
Chloramine. Chloramines are a common alternative to
chlorine for disinfection. Chloramines are not as strong an
oxidizer and are less reactive than chlorine in water. They
do, however, react with organic matter in water to form
oxidation by-products. The level of by-products formed is
less than that produced with chlorine.
Health Effects: The health effects associated with
high levels of chloramine given to animals are changes in
blood chemistry parameters and decreases in organ and body
weights. A two-year drinking water bioassay with chloramine
in rodents reported a dose-related increase in the incidence
of monbnuclear cell leukemia in female rats.
In humans, exposure to high levels of Chloramines may
result in some skin, eye and lung irritations. No adverse
health effects were noted in persons drinking chloraminated
water at levels typically used for disinfection.
Risk Assessment: The EPA has not determined an RfD for
noncancer health effects or cancer assessment for
Chloramines at this time. Health effects do not appear to be
associated with levels of residual chloramine typically
found in drinking water.
Future steps: Review new data on immunological
effects. Determine RfD for Chloramines in Summer, 1991;
initiate review of carcinogenicity of chloraminated water in
Summer, 1991; Science Advisory Board review possibly in
October, 1991.
Chlorine Dioxide, Chlorite and Chlorate: Chlorine
dioxide is a strong oxidizing agent that has been used along
with chlorine to disinfect drinking water and control
phenol-related tastes and odors in the water. Use of
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chlorine dioxide as a disinfectant does not result in the
formation of oxidation by-products found with use of
chlorine. Chlorine dioxide rapidly breaks down to chlorite
and to some extent chlorate and chloride.
Health Effects: The health effects in animals exposed
to high levels of chlorine dioxide and its byproducts,
chlorite and chlorate, include damage to red blood cells and
effects on the thyroid. Delayed neurodevelopment has also
been reported in young rats whose mothers were given high
levels of chlorine dioxide in their water.
No health effects have been observed in healthy humans
drinking water that has been disinfected with chlorine
dioxide. However, persons deficient in a liver enzyme,
glucose 6 phosphate dehydrogenase, may be at risk of
developing anemia if they drink water treated with chlorine
dioxide for a long period of time.
Risk assessment: The EPA has not determined an RfD or
cancer assessment for chlorine dioxide, chlorite and
chlorate at this time. The EPA published a guidance level in
1979, recommending that total residual oxidants not exceed 1
ppm in water when chlorine dioxide is used. EPA will develop
separate risk assessments for chlorine dioxide, chlorite and
chlorate that will likely be lower than the I ppm guidance
level. This new level could preclude the use of chlorine
dioxide as a residual disinfectant.
Future steps: Determine and verify an RfD for each
chemical in Summer, 1991. Science Advisory Board review to
be scheduled in late 1991 or early 1992.
Ozone: Ozone is another disinfectant for drinking water
that is commonly used in Europe with increasing use in the
US. It breaks down rapidly in water so that a residual is
not maintained. Thus, it may be used in conjunction with
another disinfectant such as chlorine or chloramine.
Health effects: Very little health effects information
is available on ozone. Ozone has been tested for mutagenic
activity. The results have generally been negative.
Risk assessment: The EPA has not determined an RfD or
cancer assessment for ozone. It is unlikely that EPA will
regulate ozone since a residual concentration is not
maintained in the distribution system.
Future steps: Initiate research on the potential health
effects to humans consuming ozonated drinking water.
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Disinfection Bv-Products:
Trihalomethanes: The trihalomethanes (THMs) consisting
of chloroform, bromoform, bromodichloromethane and
dibromochloromethane are the most commonly occurring by-
products of disinfection. They result from the reaction of
chlorine or chloramines with organic matter in the water.
Health Effects: Animals studies have shown that
exposure to high levels of THMs can effect liver and kidney
function. Long-term exposure to high levels of the
individual THMs has resulted in liver, kidney and intestinal
tumors in rodents.
Risk Assessments: The EPA has determined RfDs of 0.01
mg/kg/d for chloroform and 0.02 mg/kg/d for bromoform,
bromodichloromethane and dibromochloromethane. The EPA has
also determined that there is sufficient evidence of
carcinogenicity in animals to place chloroform,
bromodichloromethane and bromoform in Group B2: probable
human carcinogen. Dibromochloromethane has been placed in
Group C: possible human carcinogen based on limited evidence
of carcinogenicity in animals. The estimated excess cancer
risk range is:
Chemical • Risk Range 10'V to 10'6
Chloroform 0.6 to 0.006 ppm
Bromodichloromethane 0.03 to 0.0003 ppm
Bromoform ^ 0.4 to 0.004 ppm
The EPA established an MCL for total THMs in 1979 of
0.1 ppm. This level was based on the toxicity of chloroform
in the absence of data for the brominated THMs. with the
availablity of information for all four compounds, the
current MCL may be revised to determine a separate MCL for
each compound.
Future steps: Reevaluate the cancer risk assessment for
chloroform to consider new information on pharmacokinetics.
Reconsider the RfDs for the brominated THMs based on the
Science Advisory Board's recommendations from the October
1990 meeting.
Halo-Acetic Acids: The halo-acetic acids, consisting of
mono- (MCA), di- (DCA) and trichloroacetic acid (TCA) and
various brominated forms are also commonly occurring by-
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products of disinfection. DCA has also been used
therapeutically to control abnormal metabolism in humans.
Health Effects: Health effects data for the brominated
acetic acids and MCA are limited. Effects noted in animals
exposed to high levels of DCA include metabolic changes,
neurological effects such as muscle weakness, numbness,
tremors and liver tumors in rodents following long-term
exposure to very high levels. Studies in animals exposed to
high levels of TCA indicated changes in enzyme levels and
body weight gain. Limited evidence of liver tumors were also
observed in rodents given very high levels of TCA in
drinking water for 2 years.
Numbness and tingling sensations were reported in
patients given therapeutic doses of DCA. These symptoms
disappeared when treatment was discontinued.
Risk assessment: EPA has not determined an RfD or
cancer assessment for the chlorinated acetic acids at this
time.
Future steps: Conduct research on the potential health
risks of brominated acetic acids. Determine RfDs for DCA and
TCA in Summer, 1991. Evaluate new data for MCA. Initiate
evaluation of carcinogenicity for DCA and TCA particularly
in'reference to a possible threshold mechanism. The Science
Advisory Board will review cancer and neurotoxicity issues
for DCA and TCA in April, 1991.
Ozone by-products: Formaldehyde and bromate are
representative of ozone by-products. Formaldehyde has also
been shown to increase in concentration following
chlorination.
Formaldehyde has been classified in Group Bl: probable
human carcinogen based on limited human data and sufficient
animal data showing nasal lesions following inhalation
exposure. Formaldehyde exposure from ingestion does not
appear to have a carcinogenic potential. The EPA has
verified an RfD of 0.2 mg/kg/d based on absence of effects
on weight gain and stomach in rats given formaldehyde in
drinking water. Adjusting for an adult, water consumption
and exposure from water, EPA has developed a Lifetime Health
Advisory of 0,1 mg/L.
Bromate has not been extensively studied. Available
data indicate that oral exposure to bromate in water can
result in an increased incidence of kidney tumors in male
and female rats and an increase in peritoneal mesotheliomas
in male rats. The EPA has not formally assessed the weight
of evidence or quantitative risk for bromate
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.carcinogenicity. A review will be initiated in the Summer of
1991. Data on noncarcinogenic effects are not available.
Low Occurring Disinfection By-products: There are
several other by-products produced from disinfection that
occur in lesser frequency and concentration than the THMs or
halo-acetic acids. This group includes bromate,
chloropicrin, chloral hydrate, cyanogen chloride and the
haloacetonitriles.
Chloral hydrate, also known as trichloroacetaldehyde
monohydrate, has been used as a seditive in humans. Effects
in animals given high doses has produced changes in liver
size and weight. Preliminary results from a cancer bioassay
in rodents suggest some potential for carcinogenicity. The
EPA has determined a Refernece dose of 0.0016 mg/kg/d for
chloral hydrate. Further evaluation of the cancer data will
be initiated upon publication of the results.
Cyanogen chloride is an unstable by-product of
chloamination. It has also been used as a nerve gas agent,
particularly in WWI. The data base for cyanogen chloride
dates back to the 1920's and is inadequate to use in
determining a risk assessment. The EPA has determined a
Reference dose for cyanogen chloride based on the toxicity
of hydrogen cyanide resulting in a value of 0.02 mg/kg/d.
The EPA will reevaluate the RfD based on the recommendations
to be made by the Science Advisory Board.
EPA has not determined Reference doses or cancer
assessments for chloropicrin or the haloacetonitriles at
this time. The haloacetonitriles have been shown to produce
effects in rat fetuses whose mothers were given water
containing high levels of the compounds. EPA is presently
evaluating new information on chloropicrin.
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DRAFT COMPLIANCE MONITORING REQUIREMENTS
UNDER CONSIDERATION FOR
DISINFECTANTS AND DISINFECTION BY-PRODUCTS
June 1991
Background
The Disinfectants and Disinfection By-Products Rule
will have monitoring requirements for disinfectants and for
organic and inorganic by-products of disinfection (e.g.,
trihalomethanes and chlorate). The requirements will apply
to over 50,000 public water systems that use disinfection
(including those that purchase water from other systems).
EPA estimates that about 90% of the systems affected
will be very small ground-water systems that serve less than
500 people. Because of the characteristics unique to most
of these systems (low variability of the already low organic
content in the source water, small distribution systems),
EPA will require fewer samples to characterize disinfectant
and disinfection by-product (DBP) occurrence at those
systems. EPA also intends to allow some systems with low
vulnerability to significant DBP formation to qualify for
monitoring waivers for some by-products.
Approximately 80% of the U.S. population is currently
served by about 3000 large systems that disinfect. These
large systems must comply with the monitoring requirements
of the Trihalomethane (THM) Rule of 1979. To do so, they
have selected sample collection points, designed compliance
monitoring procedures, and are now paying about $65 per
sample for measurement of THMs. The new monitoring •'
requirements will result in additional analytical costs for
these systems; most of the new costs are anticipated to
result from measurement of haloacids ($200), chloral hydrate
($75), and chlorine dioxide ($50) (prices are per sample).
Costs for measurement of other by-products, disinfectants,
and some surrogates are indicated in Table 1.
In addition to absorbing the per sample analytical
costs, small systems (serving populations of less than
10,000) will have to set up sample collection and data
reporting procedures to meet the new monitoring
requirements.
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TABLE 1. ANALYTICAL COSTS - 1991 DOLLARS
ANALYTE OR PARAMETER
Source Water Quality Indicators
Total Organic Carbon (TOC)
(nonpurgeable)
Ultraviolet (UV) Absorption
Bromide
Total Organic Halogen (TOX)
Formation Potential Studies (FP)
COST(SI/SAMPLE
40
< 10
30
100
150-500
Organic & Inorganic Bv~Products
Trihalomethanes (THMs)
Haloacetic Acids (HAAs)
Chloral Hydrate (CH)
Bromate, Chlorate, Chlorite ($25 each)
65
200
75
75
Disinfectants
Chlorine
Chloramines
Chlorine Dioxide
(includes Chlorite & Chlorate)
< 10
< 10
50
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General Conditions of the Monitoring Requirements
1. The rule will specify minimum monitoring
requirements but will also allow systems to sample
more frequently and at more locations to determine
compliance. To sample more frequently, the system
must submit a map of all sampling locations,
reasons for the frequency selected, and the
formula that will be used to calculate a running
annual average concentration for each organic by-
product and an annual average concentration for
each disinfectant and inorganic by-product. This
plan, when approved by the State, must be used to
measure all disinfectants and by-products for
which the system must monitor.
2. A system using ground water under the direct
influence of a surface water will have the same
requirements as a surface water system.
3. When monitoring is less frequent than quarterly or
the number of samples per collection period is
less than four, the system must select a sample
point and sampling time that are expected to
produce the highest concentration of by-product.
This is defined as being during the month of
warmest water temperature, and at remote points in
the distribution system.
4. A ground-water system may (with State approval)
elect to determine compliance for disinfection
by-products (except the inorganics) with one
annual formation potential sample.
Summary of Compliance Monitoring Requirementa
O STANDARDIZED MONITORING
Although the Agency's Standardized Monitoring
Framework does not apply to the disinfectants and
disinfection by-products, the monitoring requirements
described herein fit relatively well within the
Framework. Portions of the Framework that are
compatible with the monitoring criteria being developed
include:
Monitoring is a system responsibility unless the
State accepts responsibility.
Waivers (by Rule, by Use and by Susceptibility)
2
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are granted by the State. They are used to permit
no or reduced monitoring.
There are always base Monitoring requirements that
a system must comply with whenever a waiver is not
obtained or renewed.
Initial monitoring begins on a January 1st.
Initial monitoring is phased in over three years
and States submit a compliance schedule. Phase-in
by system size is not required.
Reduced monitoring cycles are in multiples of
three years. However, some monitoring frequencies
may be as low as once every nine years depending
on the vulnerability of the system to the by-
product (s) of concern.
EPA is not planning to adopt the Standardized
Monitoring Framework per se for this rule. To do so
would delay initial monitoring until January 1999 for
systems that now disinfect. For that particular
deadline, EPA is considering January I, 1997, instead.
o WAIVERS
In general, all systems using a chemical
disinfectant must monitor for the disinfectant and
possible by-products. A system cannot receive a
waiver from disinfectant monitoring but may obtain
waivers from some or all by-product monitoring.
Exceptions to this are that systems using .ozone
will not be required to measure ozone residuals
under this rule; they will only have to measure
for by-products (unless waivers are obtained).
Systems that use only ultraviolet (UV) radiation
will not be subject to any monitoring requirements
under this rule. They will have monitoring
requirements to characterize the effectiveness of
UV disinfection under the Ground-Water
Disinfection Rule.
Systems that annually conduct monitoring of total
organic carbon (TOC), bromide, and UV absorbance
(all relatively inexpensive), or other indicators
of by-product formation potential, may be able to
obtain a waiver from some by-product measurements.
Systems with certain types of pH control, or that
can demonstrate predictable DBP formation
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correlations with other by-products or parameters
may receive a waiver from some or all by-product
monitoring.
Systems whose samples are reliably and
consistently below a "trigger" percentage of the
maximum contaminant level (MCL) for certain DBFs
may be able to obtain a waiver from some by-
product measurements.
Waivers to allow reduced monitoring frequencies
must be regularly renewed. They are not
automatically granted when prior monitoring data
is below the trigger concentration. To qualify
for reduced monitoring, the State must concur, and
there must be no significant change in source
water quality or treatment during the waiver
period.
Possible waiver criteria for "no monitoring"
waivers (i.e, waivers that would allow systems to
avoid monitoring for some or all DBFs) are listed
in Table 2. Possible criteria for reduced
frequency monitoring waivers for DBFs are shown in
Tables 3 and 4.
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MONITORING FOR ORGANIC BY-PRODUCTS
Chloral hydrate, haloacetic acids, and trihalomethanes
(Tables 3 and 4; Figures 1, 2, and 3):
The requirements have been divided first by
population served, and second by type of source water
used (ground water or surface water).
- Initial monitoring at large systems is at the same
frequencies and sample points used in the 1979 THM
Rule.
Initial monitoring at small systems requires only
one sample per sampling period.
Reduced monitoring requires a system to base
compliance on worst-case samples. However, this
should work very well for the large majority of
systems eligible for reduced monitoring. These
systems are mostly very small ground-water systems
(the majority with populations less than 500) and
have low and relatively constant concentrations of
precursors in the source water.
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MONITORING FOR DISINFECTANTS AND INORGANIC BY-PRODUCTS
Chlorine, chloramines, chlorine dioxide; bromate,
chlorate, and chlorite (Table 5}:
Disinfectant residuals are measured at least
monthly at representative locations in the
distribution system under the Surface Water
Treatment Rule (SWTR). The same is expected to be
required under the Ground-Water Disinfection Rule
(6WDR) for those systems that must disinfect
distribution systems. If a system is not using a
chemical disinfectant under the GWDR, then these
monitoring requirements will not apply.
Monitoring requirements for the inorganic by-
products are identical to those for the
disinfectants.
- Measurements of free chlorine will be required to
determine compliance with the chlorine MCL;
however, total chlorine measurements may be used
instead. Many systems measure total chlorine
residual under the SWTR.
- Total chlorine measurements will be used to
determine compliance with the chloramines MCL.
Sampling location, minimum sampling frequency, and
calculations required for determining compliance
with the disinfectant and inorganic by-product
MCLs are specified in Table 5.
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TIMING OF INITIAL MONITORING REQUIREMENTS
The estimated dates of the disinfectant and
disinfection by-product monitoring requirements
and the anticipated deadlines of the GWDR are in
Table 6, assuming promulgation by June 30, 1995
for both rules.
Systems that are disinfecting at the time of
promulgation will begin monitoring January l,
1997. States will have three years to complete
initial monitoring for all vulnerable systems.
Systems will .always have the option to begin
monitoring earlier.
Monitoring data for by-products collected up to 12
months before monitoring is required will be
accepted provided treatment and source water
quality have not changed.
Three-year phase-in periods for systems that begin
disinfection after 1995 will be as follows. For
community water systems, initial monitoring will
be phased in between January 1, 1999 and December
31, 2001. For non-transient noncommunity water
systems, initial monitoring will begin January l,
2002, which is the first January 1 after which
disinfection is anticipated to be required under
the GWDR.
- These monitoring requirements can accommodate any
combination of regulatory MCL options. The
options include, but are not limited to, setting
MCLs for each contaminant, and/or MCLs for total
THMs, and total haloacetic acids.
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COMPLIANCE DETERMINATIONS FORBY-PRODUCTS
Under the Trihaloraethane Rule of 1979, compliance is
determined by comparing the running annual average of prior
sample measurements to the total trihalomethane MCL. For
large systems (Table 3), EPA will use the same compliance
criteria for each MCL. This will apply to whatever
combination of single-contaminant MCLs or group MCLs (e.g.,
total haloacids) that EPA adopts in the Final Rule.
This approach might discourage small systems from
choosing the economy of reduced monitoring at one-, three-,
and nine-year frequencies. These systems risk having
compliance based on worst-case samples collected in this
interval. Therefore, for systems serving less than 10,000
people, EPA will consider determining compliance for chloral
hydrate, haloacids, and trihalomethanes based on a three-
year forward average.
This would work as follows. A sample is collected in
the first year that a system qualifies for a reduced
sampling frequency. Depending on the result of this
measurement, one of three repeat sampling schedules applies:
1. If the result is less than the MCL but above one
or more of the trigger concentrations, the
system's frequency increases as listed in Table 4.
2. If the result is less than both the MCL and the
trigger concentrations, the next sample continues
to be collected one, three, or nine years later.
3. If the first measurement exceeds the MCL, the
system is not in violation unless the subsequent
three-year average exceeds the MCL. The system
must increase its monitoring to at least
quarterly, and if appropriate, take corrective
action to assure compliance. Under other
requirements, disinfection compliance is always
checked by monthly monitoring of both
disinfectants and inorganic disinfection by-
products—including brornate.
Request for Comments
EPA solicits public comment on these draft monitoring
criteria and will consider comments in developing the Draft
Rule scheduled for distribution to the public in early 1992,
EPA also asks for responses to the following questions.
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We have suggested several parameters or
correlations with treatment or other by-product
occurrences as ways to waive a system from some
by-product monitoring.
a. Is this a reasonable approach?
b. What cutoffs do you suggest be set:
i. for the indicators of source water
quality listed in Table 2?
ii. for the reduced monitoring trigger
concentrations in Tables 3 and 4?
c. Do you have data to support other indicators?
d. Because of expense and complexity, we have
not proposed simulated distribution system
formation studies. Should we offer this
option? If so, how can it be cost-effective?
For large systems, the proposed monitoring
requirements for all byproducts are identical to
the requirements of the 1979 THM Rule.
a. Is this reasonable?
b. or should EPA allow more flexibility in both
initial and repeat monitoring? Specifically,
i. for initial monitoring, should we permit
a range of 2-4 samples per quarter
rather than requiring 4 per quarter?
ii. for repeat or reduced monitoring, should
EPA allow less frequent monitoring when
a system is reliably and consistently
below some percentage of the MCL? For
example, if for three years a system is
below a trigger percentage of the MCL,
the sampling frequency could be reduced
to once every three years.
When less than four samples per sampling period
are collected, or when the sampling frequency is
less than quarterly, we require that compliance
with an MCL be based on a worst-case sample.
a. Is it cost-effective for a system to select
such a site and time?
b. Should we only permit less than two samples
and less than quarterly monitoring at very
small systems?
c. If so, should these be defined only as:
serving a population less than 3,300? less
than 500? or non-transient noncommunity
systems?
d. Should EPA not permit less than one sample
per year per system under any conditions?
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If EPA fully adopted the Standardized Monitoring
Framework nine-year compliance cycle, initial
monitoring for systems that currently disinfect
and for community water systems that begin
disinfection under the GWDR would be between
1999-2001. This is a two-year delay for systems
now disinfecting; no delay for the others. Non-
transient noncommunity systems would begin
disinfection in July 2001. This means initial
monitoring would run from 2002 to 2004. This
represents no delay if the GWDR criteria are in
effect before Dec. 31, 2001.
Under what circumstances should EPA conform to the
Framework's nine-year compliance cycles, given
that this gives systems the option to delay
monitoring two years after an MCL becomes
effective?
For small systems, we have suggested three-year
forward-averaging periods for compliance with MCLs
for trihalomethanes, haloacetic acids, and chloral
hydrate. This is done to help systems that
collect worst-case samples on a frequency that is
less than quarterly.
a. Do you agree with this approach?
b. Should EPA allow three-year averaging only
for some by-products, and require one-year
averaging for by-products that have MCLs set
at the high end of the relative risk range?
Compliance determinations have not been thoroughly
discussed in this draft. Do you have suggestions
for determining compliance when worst-case samples
are collected, or when sampling frequencies are
less than quarterly?
— END
10
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