JUN 2 0 1991

     The purpose of this document is to indicate the status of
regulation development for the disinfectants (Ds)  and
disinfection by-products (DBFs) and to solicit feedback from the
public.  Previously, EPA made available to the public a
"strawman" rule (October 1989) and a conceptual framework for
developing these regulations (December 1990).

     This document reflects EPA's current thinking on how the
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:     December 1991

          Distribute draft rule
          to interested public:         February 1992

          Propose rule:                 June  1993

          Promulgate rule:              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)  _
401 M  St., SW
Washington, DC  20460

                        AND MAJOR ISSUES
                      GENERAL REQUIREMENTS
The D/DBP regulations would apply to all public water systems
(including noncoitununity 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,
                              ch1orodibromomethane, bromo form
haloacetic acids (HAs)3  -    trichloroacetic acid,
                              dichloroacetic acid
chloral hydrate
chlorine dioxide
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.

3  Three options are being considered:   1)  MCLs for
trichloroacetic acid and dichloroacetic acid;  .2) an MCL for
total HAs including mono-, di-, 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

     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

     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?

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  (SWTR)

     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 S.WTR
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

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 must 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.

     The 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

Approach to Setting MCLs

     EPA 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

               FIGURE 1
           AFFECT SLOPE
                        REGULATORY RANGE
total cost
                       cost of  treatment
                       cost of  health
                       damages incurred
                         degree of treatment

 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
iJune 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

 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 membrane
 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

     BAT in the second phase of regulation (promulgation in June
2000) might be defined as filtration followed by GAG 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 DBPs 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.



                         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.


     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


     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 reevaluated 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

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 for the 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
410C (DPD Method) as set forth in Standard Methods for the
Examination of Water 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
(DBP) Rule, the chlorine dioxide methods must be reexamined
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"; Ozone Science 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 Wastewater, 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.

Disinfection By-products;

     Trihalometbanes,  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
chromatography, these  methods are based on obsolete
chromatography 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
     The EPA has also  developed a new liquid/liquid
extraction method, which can be used to measure 4
haloacetonitriles (HANs)  (trichloroacetonitrile [TCAN],
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 (ECD).
     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
     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 quantitate 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.

     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 & 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 [246TCPh].
The method involves an acidic extraction with MTBE,
conversion of the analytes to methyl esters using
diazomethane, 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 ng/L, and most laboratories will
probably be able to reliably quantitate down to the 5-10
Mg/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
     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.

     cyanogen Chloride.   EPA Method 524.2,  published in
Methods for the Determination of Organic Compounds in
Drinking Water. EPA/600/4-88/039.  December  1988,  can be used
to measure CNC1 concentrations in water,  if the
dechlorinating/preservation technique is modified.  Ascorbic
acid is the only dechlorinating agent that  can be used with
samples for CNC1 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 Mg/L.
     Issues:  This compound is not stable in some water
matrices.  Determining a preservative for CNC1 will require
extensive research.
     Cyanogen chloride is not included in current PE
     Some purge & trap units cannot be used for CNC1
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 M9/L (formaldehyde = 8; acetaldehyde =
69), and the GC method provides MDLs around 1 M9/L-
     Issues:  Sample stability  is a major concern for this
method, and will require extensive research before  it is
     The HPLC method may not be sensitive enough  for
drinking water applications.   If MCLs are set  for certain

aldehydes and they are < 50 /ig/L for individual compounds,
the GC method may be the only method available.
     The HPLC method has not been used to measure glyoxal
and methylglyoxal concentrations.
     It is unlikely aldehydes can be included in PE studies
in the near future, due to stability and analytical method

     Chlorite/ Chlorate, Bromate, 6 Zodate.  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
     Method detection limits:  The method lists MDLs in the
range of 3-20 Mg/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.
     Iodate 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 Mg/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 l year.  If development of a method(s) is
feasible, this will be a long range research project...

     MX  [3-Chloro-4(dichloromethyl)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

     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

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 DBF 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 DBFs as bromate, bromoform, and
dibromoacetic acid.  Bromide concentrations can be measured
using ion chromatography.



                         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


     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

from a no- or lowest-observed-adverse-effect 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 MCLG.

     The MCL is then set as close to the MCLG 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


     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

determined that these data are inadequate to classify the
carcinogenicity potential of chlorinated drinking water to
humans.  They recommended further research to clarify this

     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

     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 mononuclear 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

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 by-products,
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 1 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.

Disinfection Bv-Products:

     Trihalomethanes: The trihalomethanes (THMs)  consisting
of chloroform, bromoform,  bromodichloromethane and
dibromochlororoethane 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'* 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-

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

     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

     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

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

     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.




                         June 1991

     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



Source Water Quality Indicators

Total Organic Carbon (TOC)                           40

Ultraviolet  (UV) Absorption                        < 10

Bromide                                              30

Total Organic Halogen  (TOX)                  "      100

Formation Potential Studies  (FP)                150-500

Organic & Inorganic By—Products

Trihalomethanes  (THMs)                               65

Haloacetic Acids  (HAAs)                             200

Chloral Hydrate  (CH)                                 75

Bromate, Chlorate, Chlorite  ($25 each)               75

Pis infectants

Chlorine'                                           < 10
                                                * *

Chloramines                                         < 10

Chlorine Dioxide                                    50
 (includes  Chlorite & Chlorate)

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 Requirements


          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

          Monitoring is a system responsibility unless the
          State accepts responsibility.

          Waivers  (by Rule, by Use and by Susceptibility)


        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 1, 1997, instead.

   -    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  DBF formation

correlations with other by-products or parameters
may receive a waiver from some or all by-product

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

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.

                       TABLE  2.   FOUR POSSIBLE WAIVER CRITERIA

     Systems may be allowed to avoid  measuring some  DBFs  if one or more of the
 following  criteria are met, subject to State approval.  A waiver generally must be
 renewed every year or at the  end  of the reporting period.

 1.  Raw water quality.  If the source water  (or water prior to disinfection) falls
 below certain levels [to be determined] for certain  combinations [to be determined]
 of the following parameters:

     TOC < "x"
     UV absorbance < "x"

 then monitoring for certain DBFs may  be waived.

 2.  Other water quality criteria.  If  the criteria below  [to be determined] are met
 for any of the DBFs specified, then monitoring for those  DBFs is not required.
Waiver For
Haloacetic Acids
Chloral Hydrate
Raw Water. Criteria

Bromide < "x"

Finished Water Criteria
pH > "x11 and/or
[Acids] < T% MCL
No hypochlorination
No use of ozone
[Chloroform] < T% MCL •
3.  Surrogates in finished water.  If the ratio of TTHM/TOX is [required relationship
to be determined] and pH and temperature are within [range to be determined]  and
[range to be determined], respectively, then DBF monitoring is not required.
4.  Membrane treatment.
If certain membrane processes are used,  no DBF monitoring is

                                (Based on 1979 THM Rule)

                           System size:   Population  > 10.000
Water Source:
Surface Water
Ground Water
Number of Samples:
Sample Frequency:
Reduction Criteria0:
Annual average
Annual average
< MCL or FPb <  MCL
Reduced Frequency:
(worst-case sample)
(worst-case sample)
Compliance:  See text at page 8
"Four samples taken at THM sample locations.

bOne formation potential sample.

cAssumes no change in treatment or source water quality,  and State concurs.


                           System  Size;   Population  <  10,000
Water Source:
Surface Water
Ground Water
Sample Location/Time!
Worst-case sample
from distribution
Worst-case sample
from distribution
Sample Frequency:
Reduction Criteria':
Annual average
< 50% MCL or
< 25% MCL
Each sample
< 50% MCL for 3 yrs
or one sample
< 25% MCL for 1 yr
Reduced Frequency:
1/yr or 1/3 yrs,
1/3 yrs or 1/9 yrs,
Compliance:  See text at page 8
"Assumes  no  change in treatment  or source water quality,  and State  concurs.


     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

          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.

                   FIGURE 1
                   Initial Monitoring
                 4 samples/qtr for 1 yr
                                 4 samples/qtr
   1  sample/qtr

                   FIGURE 2
    < 50%
    < 25%
              Initial: 1 sample/qtr
                   for 1 yr
 1 sample/3 yrs
            1 sample/qtr
            1  sample/yr

                   FIGURE 3
   <25% MCL?
              Initial: 1 sample
  1  sample/9 yrs
                               1 sample/yr
1  sample/3 yrs


     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
          (GWDR) 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

          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.

                                         BROMATE,  CHLORATE,  AND CHLORITE
Water Source  and  System Size:      AH vulnerable  systems0
Sample Location:                   Representative  locations  in the distribution
Sample Frequency:                  I/month"
Compliance:                        Annual average of monthly values must be < MCL.
                                   If more than 1 sample is taken per month, the
                                   monthly median values are averaged.
8Free chlorine;  analysis performed at water system.   Compliance may also be
determined using total chlorine measurements.

Compliance determined using total chlorine measurements.

cTo be defined.

Monitoring for disinfectant residuals is already required under the SWTR and
anticipated under the GWDR.


     -    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 1,
          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.


                 Disinfectants/Disinfection By-Products  Rule  (D/DBP Rule)
                         and Ground-Water Disinfection Rule (GWDR)
 D/DBP  Rule

 June 30,  1995

June 30, 1995
Effective Date;
January  1,  1997
January 1, 1997
Complete D/DBP Monitoring
(Systems Currently
January 1, 1997 -
December 31, 1999
systems That Begin
Disinfection After 1/1/95t

     Community Systems:
       Begin Disinfection:

       Complete D/DBP Monitoring:
     Noncommunity Systems:
       Begin Disinfection:

       Complete D/DBP Monitoring:
January 1, 1999 -
December 31, 2001
January 1, 2002 -
December 31, 2004
                              July 1, 1998
                              July 1, 2001


     Under the Trihalomethane 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 bromate.
Reuest for
     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.

     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?
2.   For large systems, the proposed monitoring
     requirements for all by-products 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.
3.   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
     d.   Should EPA not permit less than one sample
          per year per system under any conditions?

4.   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
5.   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?
6.   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  ===