organic halide), but
                                                                                most results
                                                                                generally did not
                                                                                provide support for
                                                                                an association.
                                                                                Preterm birth showed
                                                                                a small inverse
                                                                                relationship with DBP
                                                                                exposure (i.e. higher
                                                                                exposures showed less
                                                                                preterm births), but
                                                                                this association was
                                                                                weak. TTHM exposure
                                                                                of 80 ug/L was
                                                                                associated with twice
                                                                                the risk for small
                                                                                for gestational age
                                                                                during the third
                                                                                trimester and was
                                                                                statistically
                                                                                significant.
Toledano et al. 2005...........  Large cross-       Linked mother's    Stillbirth, low    A significant
                                  sectional study    residence at       birth weight.      association between
                                  in England, 1992-  time of delivery                      TTHM and risk of
                                  1998.              to modeled                            stillbirth, low birth
                                                     estimates of                          weight, and very low
                                                     TTHM levels in                        birth weight was
                                                     water zones.                          observed in one of
                                                                                the three regions.
                                                                                When all three
                                                                                regions were
                                                                                combined, small, but
                                                                                non-significant,
                                                                                excess risks were
                                                                                found between all
                                                                                three outcomes and
                                                                                TTHM and chloroform.
                                                                                No associations were
                                                                                observed between
                                                                                reproductive risks
                                                                                and BDCM or total
                                                                                brominated THMs.
Dodds et al. 2004 (and King et   Population-based   Estimated THM and  Stillbirth.......  A statistically
 al. 2005).                       case-control       HAA exposure at                       significant
                                  study in Nova      residence during                      association was
                                  Scotia and         pregnancy.                            observed between
                                  Eastern Ontario,   Linked water                          stillbirths and
                                  1999-2001.         consumption and                       exposure to total
                                                     showering/                            THM, BDCM, and
                                                     bathing to THM                        chloroform.
                                                     exposure.                             Associations were
                                                                                also detected for
                                                                                metrics, which
                                                                                incorporated water
                                                                                consumption,
                                                                                showering and bathing
                                                                                habits. Elevated
                                                                                relative risks were
                                                                                observed for
                                                                                intermediate
                                                                                exposures for total
                                                                                HAA and DCAA
                                                                                measures; TCAA and
                                                                                brominated HAA
                                                                                exposures showed no
                                                                                association. No
                                                                                statistically
                                                                                significant
                                                                                associations or dose-
                                                                                response
                                                                                relationships between
                                                                                any HAAs and
                                                                                stillbirth were
                                                                                detected after
                                                                                controlling for THM
                                                                                exposure.

Infante-Rivard 2004............  Case-control       Estimated THM      Intrauterine       No associations were
                                  study of           levels and water   growth             found between
                                  newborns in        consumption        retardation.       exposure to THMs and
                                  Montreal, 1998-    during                                intrauterine growth
                                  2000.              pregnancy.                            retardation. However,
                                                     Exposure from                         a significant effect
                                                     showering and                         was observed between
                                                     presence of two                       THM exposure and
                                                     genetic                               intrauterine growth
                                                     polymorphisms.                        retardation for
                                                                                newborns with the
                                                                                CYP2E1 gene variant.
                                                                                Findings suggest that
                                                                                exposure to THMs at
                                                                                the highest levels
                                                                                can affect fetal
                                                                                growth but only in
                                                                                genetically
                                                                                susceptible newborns.
Wright et al. 2004.............  Large cross-       Estimated          Birth weight,      Statistically
                                  sectional study:   maternal third-    small for          significant
                                  Massachusetts,     trimester          gestational age,   reductions in mean
                                  1995-1998.         exposures to       preterm            birth weight were
                                                     TTHMs,             delivery,          observed for BDCM,
                                                     chloroform,        gestational age.   chloroform, and
                                                     BDCM, total                           mutagenic activity.
                                                     HAAs, DCA, TCA,                       An exposure-response
                                                     MX and                                relationship was
                                                     mutagenicity in                       found between THM
                                                     drinking water.                       exposure and
                                                                                reductions in mean
                                                                                birth weight and risk
                                                                                of small for
                                                                                gestational age.
                                                                                There was no
                                                                                association between
                                                                                preterm delivery and
                                                                                elevated levels of
                                                                                HAAs, MX, or
                                                                                mutagenicity. A
                                                                                reduced risk of
                                                                                preterm delivery was
                                                                                observed with high
                                                                                THM exposures.
                                                                                Gestational age was
                                                                                associated with
                                                                                exposure to THMs and
                                                                                mutagenicity.
Yang et al. 2004 (and Yang et    Large cross-       Compared maternal  Low birth weight,  Residence in area
 al. 2000).                       sectional          consumption of     preterm delivery.  supplied with
                                  studies in         chlorinated                           chlorinated drinking
                                  Taiwan, 1994-      drinking water                        water showed a
                                  1996.              (yes/no).                             statistically
                                                                                significant
                                                                                association with
                                                                                preterm delivery. No
                                                                                association was seen
                                                                                between chlorinated
                                                                                drinking water and
                                                                                low birth weight.
Fenster et al. 2003............  Small prospective  Examined TTHM      Sperm motility,    No association between
                                  study in           levels within      sperm morphology.  TTHM level and sperm
                                  California, 1990-  the 90 days                           mobility or
                                  1991.              preceding semen                       morphology. BDCM was
                                                     collection.                           inversely associated
                                                                                with linearity of
                                                                                sperm motion. There
                                                                                was some suggestion
                                                                                that water
                                                                                consumption and other
                                                                                ingestion metrics may
                                                                                be associated with
                                                                                different indicators
                                                                                of semen quality.
Shaw et al. 2003...............  2 case-control     Estimated THM      Neural tube        No associations or
                                  maternal           levels for         defects, oral      exposure-response
                                  interview          mothers'           clefts, selected   relation were
                                  studies: CA,       residences from    heart defects.     observed between
                                  1987-1991.         before                                malformations and
                                                     conception                            TTHMs in either
                                                     through early                         study.
                                                     pregnancy.
Windham et al. 2003............  Prospective        Estimated          Menstrual cycle,   Findings suggest that
                                  study: CA, 1990-   exposure to THMs   follicular phase   THM exposure may
                                  1991.              through            length (in days).  affect ovarian
                                                     showering and                         function. All
                                                     ingestion over                        brominated THM
                                                     average of 5.6                        compounds were
                                                     menstrual cycles                      associated with
                                                     per woman.                            significantly shorter
                                                                                menstrual cycles with
                                                                                the strongest finding
                                                                                for
                                                                                chlorodibromomethane.
                                                                                There was little
                                                                                association between
                                                                                TTHM exposure and
                                                                                luteal phase length,
                                                                                menses length, or
                                                                                cycle variability.
Wright et al. 2003.............  Cross-sectional    Estimated TTHM     Birth weight,      Statistically
                                  study:             exposure in        small for          significant
                                  Massachusetts,     women during       gestational age,   associations between
                                  1990.              pregnancy          preterm            2nd trimester and
                                                     (average for       delivery,          pregnancy average
                                                     pregnancy and      gestational age.   TTHM exposure and
                                                     during each                           small for gestational
                                                     trimester).                           age and fetal birth
                                                                                weight were detected.
                                                                                Small, statistically
                                                                                significant increases
                                                                                in gestational
                                                                                duration/age were
                                                                                observed at increased
                                                                                TTHM levels, but
                                                                                there was little
                                                                                evidence of an
                                                                                association between
                                                                                TTHM and preterm
                                                                                delivery or low birth
                                                                                weight.
Cedergren et al. 2002..........  Retrospective      Examined maternal  Cardiac defects..  Exposure to chlorine
                                  case-control       periconceptional                      dioxide in drinking
                                  study: Sweden,     DBP levels and                        water showed
                                  1982-1997.         used GIS to                           statistical
                                                     assign water                          significance for
                                                     supplies.                             cardiac defects. THM
                                                                                concentrations of 10
                                                                                ug/L and higher were
                                                                                significantly
                                                                                associated with
                                                                                cardiac defects. No
                                                                                excess risk for
                                                                                cardiac defect and
                                                                                nitrate were seen.
Hwang et al. 2002..............  Large cross-       Compared exposure  Birth defects      Risk of any birth
                                  sectional study    to chlorination    (neural tube       defect, cardiac,
                                  in Norway, 1993-   (yes/no) and       defects,           respiratory system,
                                  1998.              water color        cardiac,           and urinary tract
                                                     levels for         respiratory        defects were
                                                     mother's           system, oral       significantly
                                                     residence during   cleft, urinary     associated with water
                                                     pregnancy.         tract).            chlorination.
                                                                                Exposure to
                                                                                chlorinated drinking
                                                                                water was
                                                                                statistically
                                                                                significantly
                                                                                associated with risk
                                                                                of ventricular septal
                                                                                defects, and an
                                                                                exposure-response
                                                                                pattern was seen. No
                                                                                other specific
                                                                                defects were
                                                                                associated with the
                                                                                exposures that were
                                                                                examined.

Dodds and King 2001............  Population-based   Estimated THM,     Neural tube        Exposure to BDCM was
                                  retrospective      chloroform, and    defects,           associated with
                                  cohort in Nova     bromodichloromet   cardiovascular     increased risk of
                                  Scotia, 1988-      hane (BDCM)        defects, cleft     neural tube defects,
                                  1995.              exposure.          defects,           cardiovascular
                                                                        chromosomal        anomalies. Chloroform
                                                                        abnormalities.     was not associated
                                                                                with neural tube
                                                                                defects, but was
                                                                                associated with
                                                                                chromosomal
                                                                                abnormalities. No
                                                                                association between
                                                                                THM and cleft defects
                                                                                were detected.
Jaakkola et al. 2001...........  Large cross-       Compared           Low birth weight,  No evidence found for
                                  sectional study    chlorination       small for          association between
                                  in Norway, 1993-   (yes/no) and       gestational age,   prenatal exposure to
                                  1995.              water color        preterm delivery.  chlorinated drinking
                                                     (high/low) for                        water and low birth
                                                     mother during                         weight or small for
                                                     pregnancy.                            gestational age. A
                                                                                reduced risk of
                                                                                preterm delivery was
                                                                                noted for exposure to
                                                                                chlorinated water
                                                                                with high color
                                                                                content.
K[auml]ll[eacute]n and Robert    Large cross-       Linked prenatal    Gestational        A statistically
 2000.                            sectional cohort   exposure to        duration, birth    significant
                                  study in Sweden,   drinking water     weight,            difference was found
                                  1985-1994.         disinfected with   intrauterine       for short gestational
                                                     various methods    growth,            duration and low
                                                     (no chlorine,      mortality,         birth weight among
                                                     chlorine dioxide   congenital         infants whose mother
                                                     only, sodium       malformations,     resided in areas
                                                     hypochlorite       and other birth    using sodium
                                                     only).             outcomes.          hypochlorite, but not
                                                                                for chlorine dioxide.
                                                                                Sodium hypochlorite
                                                                                was also associated
                                                                                with other indices of
                                                                                fetal development but
                                                                                not with congenital
                                                                                defects. No other
                                                                                effects were observed
                                                                                for intrauterine
                                                                                growth, childhood
                                                                                cancer, infant
                                                                                mortality, low Apgar
                                                                                score, neonatal
                                                                                jaundice, or neonatal
                                                                                hypothyroidism in
                                                                                relation to either
                                                                                disinfection method.
Dodds et al. 1999 (and King et   Population-based   Estimated TTHM     Low birth weight,  A statistically
 al. 2000b).                      retrospective      level for women    preterm birth,     significant increased
                                  cohort study in    during pregnancy.  small for          risk for stillbirths
                                  Nova Scotia,                          gestational age,   and high total THMs
                                  1988-1995.                            stillbirth,        and specific THMs
                                                                        chromosomal        during pregnancy was
                                                                        abnormalities,     detected, with higher
                                                                        neural tube        risks observed among
                                                                        defects, cleft     asphyxia-related
                                                                        defects, major     stillbirths.
                                                                        cardiac defects.   Bromodichloromethane
                                                                                had the strongest
                                                                                association and
                                                                                exhibited an exposure-
                                                                                response pattern.
                                                                                There was limited
                                                                                evidence of an
                                                                                association between
                                                                                THM level and other
                                                                                reproductive
                                                                                outcomes. No
                                                                                congenital anomalies
                                                                                were associated with
                                                                                THM exposure, except
                                                                                for a non-
                                                                                statistically
                                                                                significant
                                                                                association with
                                                                                chromosomal
                                                                                abnormalities.
Klotz and Pyrch 1999 (and Klotz  Population-based   Estimated          Neural tube        A significant
 and Pyrch 1998).                 case-control       exposure of        defects.           association was seen
                                  study in New       pregnant mothers                      between exposure to
                                  Jersey, 1993-      to TTHMs and                          THMs and neural tube
                                  1994.              HAAs, and                             defects. No
                                                     compared source                       associations were
                                                     of water.                             observed for neural
                                                                                tube defects and
                                                                                haloacetic acids or
                                                                                haloacetonitriles.
Magnus et al. 1999.............  Large cross-       Compared           Birth defects      Statistically
                                  sectional study    chlorination       (neural tube       significant
                                  in Norway, 1993-   (yes/no) and       defects, major     associations were
                                  1995.              water color        cardiac,           seen between urinary
                                                     (high/low) at      respiratory,       tract defects and
                                                     mothers'           urinary, oral      chlorination and high
                                                     residences at      cleft).            water color (high
                                                     time of birth.                        content of organic
                                                                                compounds). No
                                                                                associations were
                                                                                detected for other
                                                                                outcomes or all birth
                                                                                defects combined. A
                                                                                non-statistically
                                                                                significant, overall
                                                                                excess risk of birth
                                                                                defects was seen
                                                                                within municipalities
                                                                                with chlorination and
                                                                                high water color
                                                                                compared to
                                                                                municipalities with
                                                                                no chlorination and
                                                                                low color.
Gallagher et al. 1998..........  Retrospective      Estimated THM      Low birth weight,  Weak, non-
                                  cohort study of    levels in          term low           statistically
                                  newborns in        drinking water     birthweight, and   significant
                                  Colorado, 1990-    during third       preterm delivery.  association with low
                                  1993.              trimester of                          birth weight and TTHM
                                                     pregnancy.                            exposure during the
                                                                                third trimester.
                                                                                Large statistically
                                                                                significant increase
                                                                                for term low
                                                                                birthweight at
                                                                                highest THM exposure
                                                                                levels. No
                                                                                association between
                                                                                preterm delivery and
                                                                                THM exposure.
Swan et al. 1998...............  Prospective study  Compared           Spontaneous        Pregnant women who
                                  in California,     consumption of     abortion.          drank cold tap water
                                  1990-1991.         cold tap water                        compared to those who
                                                     to bottled water                      consumed no cold tap
                                                     during early                          water showed a
                                                     pregnancy.                            significant finding
                                                                                for spontaneous
                                                                                abortion at one of
                                                                                three sites.

Waller et al. 1998 (and Waller   Prospective        Estimated TTHM     Spontaneous        Statistically
 et al. 2001).                    cohort in          levels during      abortion.          significant increased
                                  California, 1989-  first trimester                       risk between high
                                  1991.              of pregnancy via                      intake of TTHMs and
                                                     ingestion and                         spontaneous abortion
                                                     showering.                            compared to low
                                                                                intake. BDCM
                                                                                statistically
                                                                                associated with
                                                                                increased spontaneous
                                                                                abortion; other THMs
                                                                                not. Reanalysis of
                                                                                exposure yielded less
                                                                                exposure
                                                                                misclassification and
                                                                                relative risks
                                                                                similar in magnitude
                                                                                to earlier study. An
                                                                                exposure-response
                                                                                relationship was seen
                                                                                between spontaneous
                                                                                abortion and
                                                                                ingestion exposure to
                                                                                TTHMs.
Kanitz et al. 1996.............  Cross-sectional    Compared 3 types   Low birth weight,  Smaller body length
                                  study in Italy,    of water           body length,       and small cranial
                                  1988-1989.         treatment          cranial            circumference showed
                                                     (chlorine          circumference,     statistical
                                                     dioxide, sodium    preterm            significant
                                                     hypochlorite,      delivery, and      association with
                                                     and chlorine       other effects.     maternal exposure to
                                                     dioxide/sodium                        chlorinated drinking
                                                     hypochlorite).                        water. Neonatal
                                                                                jaundice linked
                                                                                statistically to
                                                                                prenatal exposure to
                                                                                drinking water
                                                                                treated with chlorine
                                                                                dioxide. Length of
                                                                                pregnancy, type of
                                                                                delivery, and
                                                                                birthweight showed no
                                                                                association.
Bove et al. 1995 (and Bove et    Large cohort       Examined maternal  Low birth weight,  Weak, statistically
 al. 1992a & 1992b).              cross-sectional    exposure to TTHM   fetal deaths,      significant increased
                                  study in New       and various        small for          risk found for higher
                                  Jersey, 1985-      other              gestational age,   TTHM levels with
                                  1988.              contaminants.      birth defects      small for gestational
                                                                        (neural tube       age, neural tube
                                                                        defects, oral      defects, central
                                                                        cleft, central     nervous system
                                                                        nervous system,    defects, oral cleft
                                                                        major cardiac).    defects, and major
                                                                                cardiac defects. Some
                                                                                association with
                                                                                higher TTHM exposure
                                                                                and low birth weight.
                                                                                No effect seen for
                                                                                preterm birth, very
                                                                                low birth weight, or
                                                                                fetal deaths.
Savitz et al. 1995.............  Population-based   Examined TTHM      Spontaneous        There was a
                                  case-control       concentration at   abortion,          statistically
                                  study: North       residences and     preterm            significant increased
                                  Carolina, 1988-    water              delivery, low      miscarriage risk with
                                  1991.              consumption        birth weight.      high THM
                                                     (during first                         concentration, but
                                                     and third                             THM intake (based on
                                                     trimesters).                          concentration times
                                                                                consumption level)
                                                                                was not related to
                                                                                pregnancy outcome. No
                                                                                associations were
                                                                                seen for preterm
                                                                                delivery or low birth
                                                                                weight. Water source
                                                                                was not related to
                                                                                pregnancy outcome
                                                                                either, with the
                                                                                exception of a non-
                                                                                significant,
                                                                                increased risk of
                                                                                spontaneous abortion
                                                                                for bottled water
                                                                                users. There was a
                                                                                non-statistically
                                                                                significant pattern
                                                                                of reduced risk with
                                                                                increased consumption
                                                                                of water for all
                                                                                three outcomes.
Aschengrau et al. 1993.........  Case-control       Source of water    Neonatal death,    There was a non-
                                  study in           and 2 types of     stillbirth,        significant,
                                  Massachusetts,     water treatment    congenital         increased association
                                  1977-1980.         (chlorination,     anomalies.         between frequency of
                                                     chloramination).                      stillbirths and
                                                                                maternal exposure to
                                                                                chlorinated versus
                                                                                chloraminated surface
                                                                                water. An increased
                                                                                risk of urinary track
                                                                                and respiratory track
                                                                                defects and
                                                                                chlorinated water was
                                                                                detected. Neonatal
                                                                                death and other major
                                                                                malformations showed
                                                                                no association. No
                                                                                increased risk seen
                                                                                for any adverse
                                                                                pregnancy outcomes
                                                                                for surface water
                                                                                versus ground and
                                                                                mixed water use.
Kramer et al. 1992.............  Population-based   Examined           Low birth weight,  Statistically
                                  case-control       chloroform,        prematurity,       significant increased
                                  study in Iowa,     DCBM, DBCM, and    intrauterine       risk for intrauterine
                                  1989-1990.         bromoform levels   growth             growth retardation
                                                     and compared       retardation.       effects from
                                                     type of water                         chloroform exposure
                                                     source (surface,                      were observed. Non-
                                                     shallow well,                         significant increased
                                                     deep well).                           risks were observed
                                                                                for low birth weight
                                                                                and chloroform and
                                                                                for intrauterine
                                                                                growth retardation
                                                                                and DCBM. No
                                                                                intrauterine growth
                                                                                retardation or low
                                                                                birth weight effects
                                                                                were seen for the
                                                                                other THMs, and no
                                                                                effects on
                                                                                prematurity were
                                                                                observed for any of
                                                                                the THMs.
Shaw et al. 1991 (and Shaw et    Small case-        Estimated          Congenital         Following reanalysis,
 al. 1990).                       control study:     chlorinated tap    cardiac            no association
                                  Santa Clara        water              anomalies.         between cardiac
                                  County, CA, 1981-  consumption,                          anomalies and TTHM
                                  1983.              mean maternal                         level were observed.
                                                     TTHM level,
                                                     showering/
                                                     bathing exposure
                                                     at residence
                                                     during first
                                                     trimester.
Aschengrau et al. 1989.........  Case-control       Source of water    Spontaneous        A statistically
                                  study in           and exposure to    abortion.          significantly
                                  Massachusetts,     metals and other                      association was
                                  1976-1978.         contaminants.                         detected between
                                                                                surface water source
                                                                                and frequency of
                                                                                spontaneous abortion.

     Reviews/Meta-analyses
Hwang and Jakkola 2003.........  Review and meta-   Compared DBP       Birth defects      The meta-analysis
                                  analysis of 5      levels, source     (respiratory       supports an
                                  studies.           of water,          system, urinary    association between
                                                     chlorine           system, neural     exposure to
                                                     residual, color    tube defects,      chlorination by-
                                                     (high/low), and    cardiac, oral      products and the risk
                                                     2 types of         cleft).            of any birth defect,
                                                     disinfection:                         particularly the risk
                                                     chlorination and                      of neural tube
                                                     chloramination.                       defects and urinary
                                                                                system defects.
Bove et al. 2002...............  Qualitative        Examined THM       Birth defects,     Review found the
                                  review of 14       levels. Compared   small for          studies of THMs and
                                  studies.           drinking water     gestational age,   adverse birth
                                                     source and type    low birth          outcomes provide
                                                     of water           weight, preterm    moderate evidence for
                                                     treatment.         delivery,          associations with
                                                                        spontaneous        small for gestational
                                                                        abortion, fetal    age, neural tube
                                                                        death.             defects, and
                                                                                spontaneous
                                                                                abortions. Authors
                                                                                felt risks may have
                                                                                been underestimated
                                                                                and exposure-response
                                                                                relationships
                                                                                distorted due to
                                                                                exposure
                                                                                misclassification.
Graves et al. 2001.............  Review of          Examined water     Low birth weight,  Weight of evidence
                                  toxicological      consumption,       preterm            suggested positive
                                  and                duration of        delivery, small    association with DBP
                                  epidemiological    exposure, THM      for gestational    exposure for growth
                                  studies using a    levels, HAA        age,               retardation such as
                                  weight of          levels, and        intrauterine       small for gestational
                                  evidence           other              growth             age or intrauterine
                                  approach.          contaminants.      retardation,       growth retardation
                                                     Compared source    specific birth     and urinary tract
                                                     of water, water    defects,           defects. Review found
                                                     treatment, water   neonatal death,    no support for DBP
                                                     color (high/       decreased          exposure and low
                                                     low), etc.         fertility, fetal   birth weight, preterm
                                                                        resorption, and    delivery, some
                                                                        other effects.     specific birth
                                                                                defects, and neonatal
                                                                                death, and
                                                                                inconsistent findings
                                                                                for all birth
                                                                                defects, all central
                                                                                nervous system
                                                                                defects, neural tube
                                                                                defects, spontaneous
                                                                                abortion, and
                                                                                stillbirth.
Villanueva et al. 2001.........  Qualitative        Compared exposure  Spontaneous        Review found positive
                                  review of 14       to TTHM levels,    abortion, low      associations between
                                  reproductive and   mutagenic          birth weight,      increased spontaneous
                                  developmental      drinking water,    small for          abortion, low birth
                                  health effect      water              gestational age,   weight, small for
                                  studies.           consumption,       neural tube        gestational age, and
                                                     source water,      defects, other     neural tube defects
                                                     types of           reproductive and   and drinking
                                                     disinfection       developmental      chlorinated water in
                                                     (chlorination      outcomes.          most studies,
                                                     and                                   although not always
                                                     chloramination),                      with statistical
                                                     and residence                         significance.
                                                     times.
Nieuwenhuijsen et al. 2000.....  Qualitative        Examined levels    Low birth weight,  The review supports
                                  review of          of various DBPs,   preterm            some evidence of
                                  numerous           water              delivery,          association between
                                  toxicological      consumption, and   spontaneous        THMs and low birth
                                  and                duration of        abortions,         weight, but
                                  epidemiological    exposure.          stillbirth,        inconclusive. Review
                                  studies.           Compared water     birth defects,     found no evidence of
                                                     color, water       etc.               association between
                                                     treatment,                            THMs and preterm
                                                     source of water,                      delivery, and that
                                                     etc.                                  associations for
                                                                                other outcomes
                                                                                (spontaneous
                                                                                abortions,
                                                                                stillbirth, and birth
                                                                                defects) were weak
                                                                                but gaining weight.
Reif et al. 2000...............  Qualitative        Compared source    Birth weight, low  Weight of evidence
                                  reviews of         of water supply    birth weight,      suggested DBPs are
                                  numerous           and methods of     intrauterine       reproductive
                                  epidemiological    disinfection.      growth             toxicants in humans
                                  studies.           Estimated TTHM     retardation,       under appropriate
                                                     levels.            small for          exposure conditions.
                                                                        gestational age,   The review reports
                                                                        preterm deliver,   findings between
                                                                        somatic            TTHMs and effects on
                                                                        parameters,        fetal growth, fetal
                                                                        neonatal           viability, and
                                                                        jaundice,          congenital anomalies
                                                                        spontaneous        as inconsistent.
                                                                        abortion,          Reviewers felt data
                                                                        stillbirth,        are at the stage of
                                                                        developmental      hazard identification
                                                                        anomalies.         and did not suggest a
                                                                                dose-response pattern
                                                                                of increasing risk
                                                                                with increasing TTHM
                                                                                concentration.
WHO 2000.......................  Qualitative        Various exposures  Various            Review found some
                                  reviews of         to THMs.           reproductive and   support for an
                                  various studies                       developmental      association between
                                  in Finland,                           effects.           increased risks of
                                  U.S., and Canada.                                        neural tube defects
                                                                                and miscarriage and
                                                                                THM exposure. Other
                                                                                associations have
                                                                                been observed, but
                                                                                the authors believed
                                                                                insufficient data
                                                                                exist to assess any
                                                                                of these
                                                                                associations.
Craun, ed. 1998................  Qualitative        Examined THM       Stillbirth,        Associations between
                                  review of 10       levels and water   neonatal death,    DBPs and various
                                  studies, focus     consumption, and   spontaneous        reproductive effects
                                  on California      compared source    abortion, low      were seen in some
                                  cohort study.      of water and       birth weight,      epidemiological
                                                     water treatment    preterm            studies, but the
                                                     (chlorine,         delivery,          authors felt these
                                                     chloramines,       intrauterine       results do not
                                                     chlorine           growth             provide convincing
                                                     dioxide).          retardation,       evidence for a causal
                                                                        neonatal           relationship between
                                                                        jaundice, birth    DBPs and reproductive
                                                                        defects.           effects.

Mills et al. 1998..............  Qualitative        Examined TTHM      Various            Review found studies
                                  review of 22       levels and water   reproductive and   suggest possible
                                  studies.           consumption.       developmental      increases in adverse
                                                     Compared source    effects.           reproductive and
                                                     of water and 2                        developmental
                                                     types of water                        effects, such as
                                                     treatment                             increased spontaneous
                                                     (chlorination                         abortion rates, small
                                                     and                                   for gestational age,
                                                     chloramination).                      and fetal anomalies,
                                                                                but that insufficient
                                                                                evidence exists to
                                                                                establish a causal
                                                                                relationship.
Reif et al. 1996...............  Review of 3 case-  Examined THM       Birth defects      Studies reviewed
                                  control studies    levels at          (central nervous   suggest that exposure
                                  and 1 cross-       residences, dose   system, neural     to DBPs may increase
                                  sectional study.   consumption,       tube defects,      intrauterine growth
                                                     chloroform.        cardiac, oral      retardation, neural
                                                     Compared source    cleft,             tube defects, major
                                                     of waters and 2    respiratory,       heart defects, and
                                                     types of water     urinary tract),    oral cleft defects.
                                                     treatment          spontaneous        Review found
                                                     (chlorination      abortion, low      epidemiologic
                                                     and                birth weight,      evidence supporting
                                                     chloramination).   growth             associations between
                                                                        retardation,       exposure to DBPs and
                                                                        preterm            adverse pregnancy
                                                                        delivery,          outcomes to be sparse
                                                                        intrauterine       and to provide an
                                                                        growth             inadequate basis to
                                                                        retardation,       identify DBPs as a
                                                                        stillbirth,        reproductive or
                                                                        neonatal death.    developmental hazard.
Swan et al. 1992...............  Qualitative        Compared maternal  Spontaneous        Four of the studies
                                  review of 5        consumption of     abortion.          reviewed suggest that
                                  studies in Santa   residence tap                         women drinking
                                  Clara County, CA   water to bottled                      bottled water during
                                  (Deane et al.      water.                                the first trimester
                                  1992, Wrensch et                                         of pregnancy may have
                                  al. 1992, Hertz-                                         reduced risk of
                                  Picciotto et al.                                         spontaneous abortion
                                  1992, Windham et                                         relative to drinking
                                  al. 1992,                                                tap water. No
                                  Fenster et al.                                           association seen in
                                  1992).                                                   the fifth study.
                                                                                Review concluded that
                                                                                if findings are
                                                                                causal and not due to
                                                                                chance or bias, data
                                                                                suggest a 10-50%
                                                                                increase in
                                                                                spontaneous abortion
                                                                                risk for pregnant
                                                                                women drinking tap
                                                                                water over bottled
                                                                                water.
----------------------------------------------------------------------------------------------------------------

    ii. Toxicology. To date, the majority of reproductive and
developmental toxicology studies have been short term and higher dose.
Many of these studies are summarized in a review by Tyl (2000). A
summary of this review and of additional studies is provided in the
proposed Stage 2 DBPR (USEPA 2003a). Individual DBP supporting
documents evaluate and assess additional studies as well (USEPA 2000b;
USEPA 2000c; USEPA 2001a; USEPA 2001b; USEPA 2003b; USEPA 2005b; USEPA
2005c; USEPA 2005d; USEPA 2005e; USEPA 2005k). A number of recent
studies have been published that include in vivo and in vitro assays to
address mechanism of action. Overall, reproductive and developmental
toxicology studies indicate a possible reproductive/developmental
health hazard although they are preliminary in nature for the majority
of DBPs, and the dose-response characteristics of most DBPs have not
been quantified. Some of the reproductive effects of DCAA were
quantified as part of the RfD development process, and impacts of DCAA
on testicular structure are one of the critical effects in the study
that is the basis of the RfD (USEPA 2003b).
    A few long term, lower dose studies have been completed. Christian
et al. (2002a and 2002b) looked for an association between BDCM and
DBAA and reproductive and developmental endpoints. The authors
identified a NOAEL and LOAEL of 50 ppm and 150 ppm, respectively, based
on delayed sexual maturation for BDCM and a NOAEL and LOAEL of 50 ppm
and 250 ppm based on abnormal spermatogenesis for DBAA. The authors
concluded that similar effects in humans would only be seen at levels
many orders of magnitude higher than that of current drinking water
levels. As discussed in more detail in the proposal, EPA believes that
because of key methodological differences indicated as being important
in other studies (Bielmeier et al. 2001; Bielmeier et al. 2004; Kaydos
et al. 2004; Klinefelter et al. 2001; Klinefelter et al. 2004),
definitive conclusions regarding BDCM and DBAA cannot be drawn. Other
multi-generation research underway includes a study on BCAA, but this
research is not yet published.
    Biological plausibility for the effects observed in reproductive
and developmental epidemiological studies has been demonstrated through
various toxicological studies on some individual DBPs (e.g., Bielmeier
et al. 2001; Bielmeier et al. 2004; Narotsky et al. 1992; Chen et al.
2003; Chen et al. 2004). Some of these studies were conducted at high
doses, but similarity of effects observed between toxicology studies
and epidemiology studies strengthens the weight of evidence for a
possible association between adverse reproductive and developmental
health effects and exposure to chlorinated surface water.
    c. Conclusions. EPA's weight of evidence evaluation of the best
available science on carcinogenicity and reproductive and developmental
effects, in conjunction with the widespread exposure to DBPs, supports
the incremental regulatory changes in today's rule that target lowering
DBPs and providing equitable public health protection.
    EPA believes that the cancer epidemiology and toxicology literature
provide important information that contributes to the weight of
evidence for potential health risks from exposure to chlorinated
drinking water. At this time, the cancer epidemiology studies support a
potential association between exposure to chlorinated drinking water
and cancer, but evidence is insufficient to establish a causal
relationship. The epidemiological evidence for an association between
DBP exposure and colon and rectal cancers is not as consistent as it is
for bladder cancer, although similarity of effects reported in animal
toxicity and human epidemiology studies strengthens the evidence for an
association with colon and rectal cancers. EPA believes that the
overall cancer epidemiology and toxicology data support the decision to

pursue additional DBP control measures as reflected in the Stage 2
DBPR.
    Based on the weight of evidence evaluation of the reproductive and
developmental epidemiology data, EPA concludes that a causal link
between adverse reproductive or developmental health effects and
exposure to chlorinated drinking water or DBPs has not been
established, but that there is a potential association. Despite
inconsistent findings across studies, some recent studies continue to
suggest associations between DBP exposure and various adverse
reproductive and developmental effects. In addition, data from a number
of toxicology studies, although the majority of them were conducted
using high doses, demonstrate biological plausibility for some of the
effects observed in epidemiology studies. EPA concludes that no dose-
response relationship or causal link has been established between
exposure to chlorinated drinking water or disinfection byproducts and
adverse developmental or reproductive health effects. EPA's evaluation
of the best available studies, particularly epidemiology studies is
that they do not support a conclusion at this time as to whether
exposure to chlorinated drinking water or disinfection byproducts
causes adverse developmental and reproductive health effects, but do
provide an indication of a potential health concern that warrants
incremental regulatory action beyond the Stage 1 DBPR.

D. DBP Occurrence and DBP Control

    New information on the occurrence of DBPs in distribution systems
raises issues about the protection provided by the Stage 1 DBPR. This
section presents new occurrence and treatment information used to
identify key issues and to support the development of the Stage 2 DBPR.
For a more detailed discussion see the proposed Stage 2 DBPR (USEPA
2003a). For additional information on occurrence of regulated and
nonregulated DBPs, see the Occurrence Assessment for the Final Stage 2
Disinfectants and Disinfection Byproducts Rule (USEPA 2005f).
1. Occurrence
    EPA, along with the M-DBP Advisory Committee, collected, developed,
and evaluated new information that became available after the Stage 1
DBPR was published. The Information Collection Rule (ICR) (USEPA 1996)
provided new field data on DBP exposure for large water systems and new
study data on the effectiveness of several DBP control technologies.
The unprecedented amount of information collected under the ICR was
supplemented by a survey conducted by the National Rural Water
Association, data provided by various States, the Water Utility
Database (which contains data collected by the American Water Works
Association), and ICR Supplemental Surveys for small and medium water
systems.
    After analyzing the DBP occurrence data, EPA and the Advisory
Committee reached three significant conclusions that in part led the
Advisory Committee to recommend further control of DBPs in public water
systems. First, the data from the Information Collection Rule showed
that the RAA compliance calculation under the Stage 1 DBPR allows
elevated TTHM or HAA5 levels to regularly occur at some locations in
the distribution system while the overall average of TTHM or HAA5
levels at all DBP monitoring locations is below the MCLs of the Stage 1
DBPR. Customers served at those sampling locations with DBP levels that
are regularly above 0.080 mg/L TTHM and 0.060 mg/L HAA5 experience
higher exposure compared to customers served at locations where these
levels are consistently met.
    Second, the new data demonstrated that DBP levels in single samples
can be substantially above 0.080 mg/L TTHM and 0.060 mg/L HAA5. Some
customers receive drinking water with concentrations of TTHM and HAA5
up to 75% above 0.080 mg/L and 0.060 mg/L, respectively, even when
their water system is in compliance with the Stage 1 DBPR. Some studies
support an association between acute exposure to DBPs and potential
adverse reproductive and developmental health effects (see Section
III.C for more detail).
    Third, the data from the Information Collection Rule revealed that
the highest TTHM and HAA5 levels can occur at any monitoring site in
the distribution system. In fact, the highest concentrations did not
occur at the maximum residence time locations in more than 50% of all
ICR samples. The fact that the locations with the highest DBP levels
vary in different public water systems indicates that the Stage 1 DBPR
monitoring may not accurately represent the high DBP concentrations
that actually exist in distribution systems, and that additional
monitoring is needed to identify distribution system locations with
elevated DBP levels.
    These data showed that efforts beyond the Stage 1 DBPR are needed
to provide more equitable protection from DBP exposure across the
entire distribution system. The incremental regulatory changes made
under the Stage 2 DBPR meet this need by reevaluating the locations of
DBP monitoring sites and addressing high DBP concentrations that occur
at particular locations or in single samples within systems in
compliance.
2. Treatment
    The analysis of the new treatment study data confirmed that certain
technologies are effective at reducing DBP concentrations. Bench- and
pilot-scale studies for granular activated carbon (GAC) and membrane
technologies required by the Information Collection Rule provided
information on the effectiveness of the two technologies. Other studies
found UV light to be highly effective for inactivating Cryptosporidium
and Giardia at low doses without promoting the formation of DBPs
(Malley et al. 1996; Zheng et al. 1999). This new treatment information
adds to the treatment options available to utilities for controlling
DBPs beyond the requirements of the Stage 1 DBPR.

E. Conclusions for Regulatory Action

    After extensive analysis of available data and rule options
considered by the Advisory Committee and review of public comments on
the proposed Stage 2 DBPR (USEPA, 2003a), EPA is finalizing a Stage 2
DBPR control strategy consistent with the key elements of the Agreement
in Principle signed in September 2000 by the participants in the Stage
2 M-DBP Advisory Committee. EPA believes that exposure to chlorinated
drinking water may be associated with cancer, reproductive, and
developmental health risks. EPA determined that the risk-targeting
measures recommended in the Agreement in Principle will require only
those systems with the greatest risk to make treatment and operational
changes and will maintain simultaneous protection from potential health
concerns from DBPs and microbial contaminants. EPA has carefully
evaluated and expanded upon the recommendations of the Advisory
Committee and public comments to develop today's rule. EPA also made
simplifications where possible to minimize complications for public
water systems as they transition to compliance with the Stage 2 DBPR
while expanding public health protection. The requirements of the Stage
2 DBPR are described in detail in Section IV of this preamble.

IV. Explanation of Today's Action

A. MCLGs

    MCLGs are set at concentration levels at which no known or
anticipated adverse health effects occur, allowing for an adequate
margin of safety.

Establishment of an MCLG for each specific contaminant is based on the
available evidence of carcinogenicity or noncancer adverse health
effects from drinking water exposure using EPA's guidelines for risk
assessment. MCLGs are developed to ensure they are protective of the
entire population.
    Today's rule provides MCLGs for chloroform and two haloacetic
acids, monochloroacetic acid (MCAA) and trichloroacetic acid (TCAA).
1. Chloroform MCLG
    a. Today's rule. The final MCLG for chloroform is 0.07 mg/L. The
MCLG was calculated using toxicological evidence that the carcinogenic
effects of chloroform are due to sustained tissue toxicity. EPA is not
changing the other THM MCLGs finalized in the Stage 1 DBPR.
    b. Background and analysis. The MCLG for chloroform is unchanged
from the proposal. The MCLG is calculated using a reference dose (RfD)
of 0.01 mg/kg/day and an adult tap water consumption of 2 L per day for
a 70 kg adult. A relative source contribution (RSC) of 20% was used in
accordance with Office of Water's current approach for deriving RSC
through consideration of data that indicate that other routes and
sources of exposure may potentially contribute substantially to the
overall exposure to chloroform. See the proposed Stage 2 DBPR (USEPA
2003a) for a detailed discussion of the chloroform MCLG.
[GRAPHIC] [TIFF OMITTED] TR04JA06.003

    Based on an analysis of the available scientific data on
chloroform, EPA believes that the chloroform dose-response is nonlinear
and that chloroform is likely to be carcinogenic only under high
exposure conditions (USEPA 2001a). This assessment is supported by the
principles of the 1999 EPA Proposed Guidelines for Carcinogen Risk
Assessment (USEPA 1999a) and reconfirmed by the 2005 final Cancer
Guidelines (USEPA 2005i). The science in support of a nonlinear
approach for estimating the carcinogenicity of chloroform was affirmed
by the Chloroform Risk Assessment Review Subcommittee of the EPA SAB
Executive Committee (USEPA 2000d). Since the nonzero MCLG is based on a
mode of action consideration specific to chloroform, it does not affect
the MCLGs of other trihalomethanes.
    c. Summary of major comments. EPA received many comments in support
of the proposed MCLG calculation for chloroform, although some
commenters disagreed with a non-zero MCLG.
    At this time, based on an analysis of all the available scientific
data on chloroform, EPA concludes that chloroform is likely to be
carcinogenic to humans only under high exposure conditions that lead to
cytotoxicity and regenerative hyperplasia and that chloroform is not
likely to be carcinogenic to humans under conditions that do not cause
cytotoxicity and cell regeneration (USEPA 2001a). Therefore, the dose-
response is nonlinear, and the MCLG is set at 0.07 mg/L. This
conclusion has been reviewed by the SAB (USEPA 2000d), who agree that
nonlinear approach is most appropriate for the risk assessment of
chloroform; it also remains consistent with the principles of the 1999
EPA Proposed Guidelines for Carcinogenic Risk Assessment (USEPA 1999a)
and the final Cancer Guidelines ( USEPA 2005i), which allow for
nonlinear extrapolation.
    EPA also received some comments requesting a combined MCLG for THMs
or HAAs. This is not appropriate because these different chemicals have
different health effects.
2. HAA MCLGs: TCAA and MCAA
    a. Today's rule. Today's rule finalizes the proposed Stage 2 MCLG
for TCAA of 0.02 mg/L (USEPA 2003a) and sets an MCLG for MCAA of 0.07
mg/L. EPA is not changing the other HAA MCLGs finalized in the Stage 1
DBPR (USEPA 1998a).
    b. Background and analysis. The Stage 1 DBPR included an MCLG for
TCAA of 0.03 mg/L and did not include an MCLG for MCAA (USEPA 1998a).
Based on toxicological data published after the Stage 1 DBPR, EPA
proposed new MCLGs for TCAA and MCAA of 0.02 mg/L and 0.03 mg/L,
respectively, in the Stage 2 proposal (USEPA 2003a). The proposed TCAA
MCLG and its supporting analysis is being finalized unchanged in
today's final rule. The MCLG calculation for MCAA is revised in this
final rule, based on a new reference dose, as discussed later. See the
proposed Stage 2 DBPR (USEPA 2003a) for a detailed discussion of the
calculation of the MCLGs.
    TCAA. The MCLG for TCAA was calculated based on the RfD of 0.03 mg/
kg/day using a 70 kg adult body weight, a 2 L/day drinking water
intake, and a relative source contribution of 20%. An additional
tenfold risk management factor has been applied to account for the
possible carcinogenicity of TCAA. This approach is consistent with EPA
policy. TCAA induces liver tumors in mice (Ferreira-Gonzalez et al.
1995; Pereira 1996; Pereira and Phelps 1996; Tao et al. 1996;
Latendresse and Pereira 1997; Pereira et al. 1997) but not in rats
(DeAngelo et al. 1997). Much of the recent data on the carcinogenicity
of TCAA have focused on examining the carcinogenic mode(s) of action.
However, at this time, neither the bioassay nor the mechanistic data
are sufficient to support the development of a slope factor from which
to quantify the cancer risk.
[GRAPHIC] [TIFF OMITTED] TR04JA06.000

    The chronic bioassay for TCAA by DeAngelo et al. (1997) was
selected as the critical study for the development of the RfD. In this
chronic drinking water study, a dose-response was noted for several
endpoints and both a LOAEL and NOAEL were determined. The data are
consistent with the findings in both the Pereira (1996) chronic
drinking water study and the Mather et al. (1990) subchronic drinking
water study. The RfD of 0.03 mg/kg/day is based on the NOAEL of 32.5
mg/kg/day for liver histopathological changes in rats (DeAngelo et al.
1997). A composite uncertainty factor of 1000 was applied in the RfD
determination. A default uncertainty factor of 10 was applied to

the RfD to account for extrapolation from an animal study because data
to quantify rat-to-human differences in toxicokinetics or
toxicodynamics are not available. The default uncertainty factor of 10
was used to account for human variability in the absence of data on
differences in human susceptibility. Although subchronic and chronic
studies of TCAA have been reported for multiple species, many studies
have focused on liver lesions and a full evaluation of a wide range of
potential target organs has not been conducted in two different
species. In addition, there has been no multi-generation study of
reproductive toxicity and the data from teratology studies in rats
provide LOAEL values but no NOAEL for developmental toxicity. Thus, an
additional uncertainty factor of 10 was used to account for database
insufficiencies.
    The MCLG calculation also includes a relative source contribution
(RSC) of 20%. The RSC was derived consistent with Office of Water's
current approach for deriving RSC. In addition to disinfected water,
foods are expected to contribute to daily exposure to TCAA (Raymer et
al. 2001, 2004; Reimann et al. 1996). Some of the TCAA in foods comes
from cleaning and cooking foods in chlorinated water. Additional TCAA
is found in some foods because of the widespread use of chlorine as a
sanitizing agent in the food industry (USFDA 1994). EPA was not able to
identify any dietary surveys or duplicate diet studies of TCAA in the
diet. TCAA also has been identified in rain water, suggesting some
presence in the atmosphere (Reimann et al. 1996); however, due to the
low volatility (0.5--0.7 mm Hg at 25 [deg]C) of TCAA, exposure from
ambient air is expected to be minimal. Dermal exposure to disinfected
water is also unlikely to be significant. A study by Xu et al. (2002)
reports that dermal exposure from bathing and showering is only 0.01%
of that from oral exposure. In addition, the solvents
trichloroethylene, tetrachlorethylene, 1,1,1-trichloroethane (often
found in ambient air and drinking water), and the disinfection
byproduct chloral hydrate all contribute to the body's TCAA load since
each of these compounds is metabolized to TCAA (ATSDR 2004; ATSDR
1997a; ATSDR 1997b; USEPA 2000e). Due to the limitations primarily in
the dietary data and a clear indication of exposure from other sources,
EPA applied a relative source contribution of 20%.
    MCAA. The MCLG for MCAA uses the following calculations: An RfD of
0.01 mg/kg/day, a 70 kg adult consuming 2 L/day of tap water, and a
relative source contribution of 20%.
    The RfD included in the proposal was based on a chronic drinking
water study in rats conducted by DeAngelo et al. (1997). In the
assessment presented for the proposed rule, the LOAEL from this study
was identified as 3.5 mg/kg/day based on increased absolute and
relative spleen weight in the absence of histopathologic changes. After
reviewing comments and further analysis of the data, EPA concludes that
it is more appropriate to identify this change as a NOAEL. Increased
spleen weights in the absence of histopathological effects are not
necessarily adverse. In addition, spleen weights were decreased, rather
than increased in the mid- and high-dose groups in the DeAngelo et al.
(1997) study and were accompanied by a significant decrease in body
weight, decreased relative and absolute liver weights, decreased
absolute kidney weight, and an increase in relative testes weight.
Accordingly, the mid-dose in this same study (26.1 mg/kg/day) has been
categorized as the LOAEL with the lower 3.5 mg/kg/day dose as a NOAEL.
    Based on a NOAEL of 3.5 mg/kg/day (DeAngelo et al. 1997), the
revised RfD was calculated as shown below, with a composite uncertainty
factor of 300. EPA used a default uncertainty factor of 10 to account
for extrapolation from an animal study, since no data on rat-to-human
differences in toxicokinetics or toxicodynamics were identified. A
default uncertainty factor of 10 was used to account for human
variability in the absence of data on the variability in the
toxicokinetics of MCAA in humans or in human susceptibility to MCAA. An
additional uncertainty factor of three was used to account for database
insufficiencies. Although there is no multi-generation reproduction
study, the available studies of reproductive and developmental
processes suggest that developmental toxicity is unlikely to be the
most sensitive endpoint. This led to the following calculation of the
Reference Dose (RfD) and MCLG for MCAA:
[GRAPHIC] [TIFF OMITTED] TR04JA06.001

Where:

3.5 mg/kg/day = NOAEL for decreased body weight plus decreased liver,
kidney and spleen weights in rats exposed to MCA for 104 weeks in
drinking water (DeAngelo et al. 1997).
300 = composite uncertainty factor chosen to account for inter species
extrapolation, inter-individual variability in humans, and deficiencies
in the database.
[GRAPHIC] [TIFF OMITTED] TR04JA06.002

    The RSC for MCAA was selected using comparable data to that
discussed for TCAA. MCAA, like TCAA, has been found in foods and is
taken up by foods during cooking (15% in chicken to 62% in pinto beans)
and cleaning (2.5% for lettuce) with water containing 500 ppb MCAA
(Reimann et al.1996; Raymer et al. 2001, 2004). Rinsing of cooked foods
did not increase the MCAA content of foods to the same extent as was
observed for TCAA (Raymer et al. 2004). MCAA was found to be completely
stable in water boiled for 60 minutes and is likely to be found in the
diet due to the use of chlorinated water in food preparation and the
use of chlorine as a sanitizing agent by the food industry (USFDA
1994). As with TCAA, inhalation and dermal exposures are unlikely to be
significant. Dermal exposure from bathing and showering was estimated
to contribute only 0.03% of that from oral exposure (Xu et al. 2002).
As with TCAA, due to the limitations in dietary data and a clear
indication of exposure from other

sources, EPA applied a relative source contribution of 20%.
    c. Summary of major comments. EPA received few comments on MCAA and
TCAA. The majority of comments about the MCLGs for TCAA and MCAA were
general MCLG questions, including RSC derivation. Some commenters
questioned why MCAA, TCAA, and chloroform were calculated using an RSC
of 20%. In particular, some commenters compared these calculations to
that for DBCM in the Stage 1 DBPR, which uses 80%. Each of the MCLGs
set for chloroform, TCAA, and MCAA under this rule is calculated using
the best available science and EPA Office of Water's current approach
for deriving the RSC. EPA chose an RSC of 20%, not 80%, because of
clear indications of exposure from other sources; data limitations
preclude the derivation of a specific RSC.
    The RSC for DBCM was 80% in the Stage 1 DBPR. The DBCM MCLG is not
part of today's rulemaking. Any possible future revision to the DBCM
MCLG as a result of an RSC change would not affect the MCL for TTHM
finalized in today's rule.
    In response to comments received on the RfD for MCAA, EPA has
reviewed the critical study regarding the appropriateness of an
increase in spleen weight in the absence of histopathology as a LOAEL.
EPA has determined that the dose associated with this endpoint is more
appropriately categorized as a NOAEL rather than a LOAEL and has
revised the RfD and MCLG for MCAA.

B. Consecutive Systems

    Today's rule includes provisions for consecutive systems, which are
public water systems that receive some or all of their finished water
from another water system (a wholesale system). Consecutive systems
face particular challenges in providing water that meets regulatory
standards for DBPs and other contaminants whose concentration can
increase in the distribution system. Moreover, previous regulation of
DBP levels in consecutive systems varies widely among States. In
consideration of these factors, EPA is finalizing monitoring,
compliance schedule, and other requirements specifically for
consecutive systems. These requirements are intended to facilitate
compliance by consecutive systems with MCLs for TTHM and HAA5 under the
Stage 2 DBPR and help to ensure that consumers in consecutive systems
receive equivalent public health protection.
1. Today's Rule
    As public water systems, consecutive systems must provide water
that meets the MCLs for TTHM and HAA5 under the Stage 2 DBPR, use
specified analytical methods, and carry out associated monitoring,
reporting, recordkeeping, public notification, and other requirements.
The following discusses a series of definitions needed for addressing
consecutive system requirements in today's rule. Later sections of this
preamble provide further details on how rule requirements (e.g.,
schedule and monitoring) apply to consecutive systems.
    A consecutive system is a public water system that receives some or
all of its finished water from one or more wholesale systems.
    Finished water is water that has been introduced into the
distribution system of a public water system and is intended for
distribution and consumption without further treatment, except as
necessary to maintain water quality in the distribution system (e.g.,
booster disinfection, addition of corrosion control chemicals).
    A wholesale system is a public water system that treats source
water as necessary to produce finished water and then delivers finished
water to another public water system. Delivery may be through a direct
connection or through the distribution system of one or more
consecutive systems.
    The combined distribution system is defined as the interconnected
distribution system consisting of the distribution systems of wholesale
systems and of the consecutive systems that receive finished water from
those wholesale system(s).
    EPA is allowing States some flexibility in defining what systems
are a part of a combined distribution system. This provision determines
effective dates for requirements in today's rule; see Section IV.E
(Compliance Schedules) for further discussion. EPA has consulted with
States and deferred to their expertise regarding the nature of the
connection in making combined distribution system determinations. In
the absence of input from the State, EPA will determine that combined
distribution systems include all interconnected systems for the purpose
of determining compliance schedules for implementation of this rule.
2. Background and Analysis
    The practice of public water systems buying and selling water to
each other has been commonplace for many years. Reasons include saving
money on pumping, treatment, equipment, and personnel; assuring an
adequate supply during peak demand periods; acquiring emergency
supplies; selling surplus supplies; and delivering a better product to
consumers. EPA estimates that there are more than 10,000 consecutive
systems nationally.
    Consecutive systems face particular challenges in providing water
that meets regulatory standards for contaminants that can increase in
the distribution system. Examples of such contaminants include
coliforms, which can grow if favorable conditions exist, and some DBPs,
including THMs and HAAs, which can increase when a disinfectant and DBP
precursors continue to react in the distribution system.
    EPA included requirements specifically for consecutive systems
because States have taken widely varying approaches to regulating DBPs
in consecutive systems in previous rules. For example, some States have
not regulated DBP levels in consecutive systems that deliver
disinfected water but do not add a disinfectant. Other States have
determined compliance with DBP standards based on the combined
distribution system that includes both the wholesaler and consecutive
systems. In this case, sites in consecutive systems are treated as
monitoring sites within the combined distribution system. Neither of
these approaches provide the same level of public health protection as
non-consecutive systems receive under the Stage 1 DBPR. Once fully
implemented, today's rule will ensure similar protection for consumers
in consecutive systems.
    In developing its recommendations, the Stage 2 M-DBP Advisory
Committee recognized two principles related to consecutive systems: (1)
consumers in consecutive systems should be just as well protected as
customers of all systems, and (2) monitoring provisions should be
tailored to meet the first principle. Accordingly, the Advisory
Committee recommended that all wholesale and consecutive systems comply
with provisions of the Stage 2 DBPR on the same schedule required of
the wholesale or consecutive system serving the largest population in
the combined distribution system. In addition, the Advisory Committee
recommended that EPA solicit comments on issues related to consecutive
systems that the Advisory Committee had not fully explored (USEPA
2000a). EPA agreed with these recommendations and they are reflected in
today's rule.

3. Summary of Major Comments
    Commenters generally supported the proposed definitions. However,
commenters did express some concerns, especially with including a time
period of water delivery that defined whether a system was a
consecutive system (proposed to trigger plant-based monitoring
requirements) or wholesale system (proposed to allow determination that
a combined distribution system existed). EPA has dropped this
requirement from the final rule; population-based monitoring
requirements in the final rule do not need to define how long a plant
must operate in order to be considered a plant, and EPA has provided
some flexibility for States to determine which systems comprise a
combined distribution system (without presenting a time criterion).
    Other commenters expressed concern that the proposed definition of
consecutive system was inconsistent with use of the term prior to the
rulemaking. EPA acknowledges that the Agency has not previously
formally defined the term, but believes that the definition in today's
rule best considers all commenters' concerns, while also providing for
accountability and public health protection in as simple a manner as is
possible given the many consecutive system scenarios that currently
exist.
    Several States requested flexibility to determine which systems
comprised a combined distribution system under this rule; EPA has
included that flexibility for situations in which systems have only a
marginal association (such as an infrequently used emergency
connection) with other systems in the combined distribution system. To
prepare for the IDSE and subsequent Stage 2 implementation, EPA has
worked with States in identifying all systems that are part of each
combined distribution system.
    Finally, several commenters requested that the wholesale system
definition replace ``public water system'' with ``water system'' so
that wholesale systems serving fewer than 25 people would not be
considered public water systems. EPA did not change the definition in
today's rule; EPA considers any water system to be a public water
system (PWS) if it serves 25 or more people either directly (retail) or
indirectly (by providing finished water to a consecutive system) or
through a combination of retail and consecutive system customers. If a
PWS receives water from an unregulated entity, that PWS must meet all
compliance requirements (including monitoring and treatment techniques)
that any other public water system that uses source water of unknown
quality must meet.

C. LRAA MCLs for TTHM and HAA5

1. Today's Rule
    This rule requires the use of locational running annual averages
(LRAAs) to determine compliance with the Stage 2 MCLs of 0.080 mg/L
TTHM and 0.060 mg/L HAA5. All systems, including consecutive systems,
must comply with the MCLs for TTHM and HAA5 using sampling sites
identified under the Initial Distribution System Evaluation (IDSE) or
using existing Stage 1 DBPR compliance monitoring locations (as
discussed in Section IV.F). EPA has dropped the proposed phased
approach for LRAA implementation (Stage 2A and Stage 2B) by removing
Stage 2A and redesignating Stage 2B as Stage 2.
    Details of monitoring requirements and compliance schedules are
discussed in preamble Sections IV.G and IV.E, respectively, and may be
found in subpart V of today's rule.
2. Background and Analysis
    The MCLs for TTHM and HAA5 are the same as those proposed, 0.080
mg/L TTHM and 0.060 mg/L HAA5 as an LRAA. See the proposed rule (68 FR
49584, August 18, 2003) (USEPA 2003a) for a more detailed discussion of
the analysis supporting the MCLs. The primary objective of the LRAA is
to reduce exposure to high DBP levels. For an LRAA, an annual average
must be computed at each monitoring location. The RAA compliance basis
of the 1979 TTHM rule and the Stage 1 DBPR allows a system-wide annual
average under which high DBP concentrations in one or more locations
are averaged with, and dampened by, lower concentrations elsewhere in
the distribution system. Figure IV.C-1 illustrates the difference in
calculating compliance with the MCLs for TTHM between a Stage 1 DBPR
RAA, and the Stage 2 DBPR LRAA.
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    EPA and the Stage 2 M-DBP Advisory Committee considered an array of
alternative MCL strategies. The Advisory Committee discussions
primarily focused on the relative magnitude of exposure reduction
versus the expected impact on the water industry and its customers.
Strategies considered included across the board requirements, such as
significantly decreasing the MCLs (e.g., 40/30) or single hit MCLs
(e.g., all samples must be below 80/60); and risk targeting
requirements. In the process of evaluating alternatives, EPA and the
Advisory Committee reviewed vast quantities of data and many analyses
that addressed health effects, DBP occurrence, predicted reductions in
DBP levels, predicted technology changes,

and capital, annual, and household costs. The Advisory Committee
recommended and EPA proposed the risk targeting approach of 80/60 as an
LRAA preceded by an IDSE. Today's rule finalizes these requirements.
    EPA has chosen compliance based on an LRAA due to concerns about
levels of DBPs above the MCL in some portions of the distribution
system. The LRAA standard will eliminate system-wide averaging of
monitoring results from different monitoring locations. The individuals
served in areas of the distribution system with above average DBP
occurrence levels masked by averaging under an RAA are not receiving
the same level of health protection. Although an LRAA standard still
allows averaging at a single location over an annual period, EPA
concluded that changing the basis of compliance from an RAA to an LRAA
will result in decreased exposure to higher DBP levels (see Section VI
for predictions of DBP reductions under the LRAA MCLs). This conclusion
is based on three considerations:
    (1) There is considerable evidence that under the current RAA MCL
compliance monitoring requirements, a small but significant proportion
of monitoring locations experience high DBP levels at least some of the
time. Of systems that collected data under the Information Collection
Rule that met the Stage 1 DBPR RAA MCLs, 14 percent had TTHM single
sample concentrations greater than the Stage 1 MCL, and 21 percent had
HAA5 single sample concentrations above the MCL. Although most TTHM and
HAA5 samples were below 100 [mu]g/L, some ranged up to 140 [mu]g/L and
130 [mu]g/L, respectively.
    (2) In some situations, the populations served by certain portions
of the distribution system consistently receive water that exceeds
0.080 mg/L for TTHM or 0.060 mg/L for HAA5 (both as LRAAs) even though
the system is in compliance with Stage 1 MCLs). Of Information
Collection Rule systems meeting the Stage 1 DBPR MCLs as RAAs, five
percent had monitoring locations that exceeded 0.080 mg/L TTHM and
three percent exceeded 0.060 mg/L HAA5 as an annual average (i.e., as
LRAAs) by up to 25% (calculated as indicated in Figure IV.C-1).
Customers served at these locations consistently received water with
TTHM and/or HAA5 concentrations higher than the system-wide average and
higher than the MCL.
    (3) Compliance based on an LRAA will remove the opportunity for
systems to average out samples from high and low quality water sources.
Some systems are able to comply with an RAA MCL even if they have a
plant with a poor quality water source (that thus produces high
concentrations of DBPs) because they have another plant that has a
better quality water source (and thus lower concentrations of DBPs).
Individuals served by the plant with the poor quality source will
usually have higher DBP exposure than individuals served by the other
plant.
    In part, both the TTHM and HAA5 classes are regulated because they
occur at high levels and represent chlorination byproducts that are
produced from source waters with a wide range of water quality. The
combination of TTHM and HAA5 represent a wide variety of compounds
resulting from bromine substitution and chlorine substitution reactions
(e.g., bromoform has three bromines, TCAA has three chlorines, BDCM has
one bromine and two chlorines). EPA believes that the TTHM and HAA5
classes serve as an indicator for unidentified and unregulated DBPs.
EPA believes that controlling the occurrence levels of TTHM and HAA5
will help control the overall levels of chlorination DBPs.
3. Summary of Major Comments
    Commenters supported the proposed, risk-targeted MCL strategy over
the alternative MCL strategies that were considered by the Advisory
Committee as the preferred regulatory strategy. Commenters concurred
with EPA's analysis that such an approach will reduce peak and average
DBP levels. Commenters supported the Stage 2 long-term MCLs of 0.080
mg/L TTHM and 0.060 mg/L HAA5 as LRAAs.
    EPA received many comments on today's MCLs specific to consecutive
systems. While commenters supported consecutive system compliance with
the Stage 2 DBPR in order to provide comparable levels of public health
protection, they noted that it would be difficult for many consecutive
systems to meet Stage 2 requirements because they have not had to meet
the full scope of DBP requirements under previous rules. EPA has
developed a training and outreach program to assist these systems and
encourages States, wholesale systems, and professional associations to
also provide assistance.
    Some commenters expressed concern about holding consecutive systems
responsible for water quality over which they have no control. Several
commenters were concerned about the establishment of contracts between
wholesale and consecutive systems, including concern about a strain on
their relationship, wholesale system reluctance to commit to keep DBPs
at a level suggested by the consecutive systems, and the time and money
it could take to work out differences. Although setting up a contract
is a prudent business action, commenters noted that small consecutive
water systems have few resources to sue for damages should the
wholesaler provide water exceeding the MCL.
    The purpose of DBPRs is to protect public health from exposure to
high DBP levels. Not requiring violations when distributed water
exceeds MCLs undermines the intent of the rule. While EPA recognizes
consecutive systems do not have full control over the water they
receive, agreements between wholesale and consecutive systems may
specify water quality and actions required of the wholesaler if those
water quality standards are not met.
    Finally, commenters recommended that the Stage 2A provisions in the
proposed rule be removed. These provisions (compliance with locational
running annual average MCLs of 0.120 mg/L for TTHM and 0.100 mg/L for
HAA5) required systems to comply with the Stage 1 MCLs (as running
annual averages) and the Stage 2A MCLs (as LRAAs) concurrently until
systems were required to comply with Stage 2B MCLs. Commenters noted
that having two separate MCLs for an individual system to comply with
at the same time was confusing to the system and its customers. In
addition, State resources needed for compliance determinations and data
management for this short-term requirement would be resource-intensive.
Finally, resources spent to comply with Stage 2A would be better spent
in complying with Stage 2B, especially given that some of the changes
for Stage 2A compliance might not provide any benefit for Stage 2B.
Since EPA agrees with commenters' concerns, the Stage 2A requirements
have been removed from the final rule.

D. BAT for TTHM and HAA5

1. Today's Rule
    Today, EPA is identifying the best available technology (BAT) for
the TTHM and HAA5 LRAA MCLs (0.080 mg/L and 0.060 mg/L respectively)
for systems that treat their own source water as one of the three
following technologies:
    (1) GAC10 (granular activated carbon filter beds with an empty-bed
contact time of 10 minutes based on average daily flow and a carbon
reactivation frequency of every 120 days)
    (2) GAC20 (granular activated carbon filter beds with an empty-bed
contact time of 20 minutes based on average

daily flow and a carbon reactivation frequency of every 240 days)
    (3) Nanofiltration (NF) using a membrane with a molecular weight
cutoff of 1000 Daltons or less.
    EPA is specifying a different BAT for consecutive systems than for
systems that treat their own source water to meet the TTHM and HAA5
LRAA MCLs. The consecutive system BAT is chloramination with management
of hydraulic flow and storage to minimize residence time in the
distribution system for systems that serve at least 10,000 people and
management of hydraulic flow and storage to minimize residence time in
the distribution system for systems that serve fewer than 10,000
people.
2. Background and Analysis
    The BATs are the same as was proposed, except that consecutive
systems serving fewer than 10,000 people do not have chloramination as
part of the consecutive system BAT. See the proposal (68 FR 49588,
August 18, 2003) (USEPA 2003a) for more detail on the analysis
supporting these requirements. The Safe Drinking Water Act directs EPA
to specify BAT for use in achieving compliance with the MCL. Systems
unable to meet the MCL after application of BAT can get a variance (see
Section IV.K for a discussion of variances). Systems are not required
to use BAT in order to comply with the MCL. PWSs may use any State-
approved technologies as long as they meet all drinking water
standards.
    EPA examined BAT options first by analyzing data from the
Information Collection Rule treatment studies designed to evaluate the
ability of GAC and NF to remove DBP precursors. Based on the treatment
study results, GAC is effective for controlling DBP formation for
waters with influent TOC concentrations below approximately 6 mg/L
(based on the Information Collection Rule and NRWA data, over 90
percent of plants have average influent TOC levels below 6 mg/L (USEPA
2003c)). Of the plants that conducted an Information Collection Rule
GAC treatment study, approximately 70 percent of the surface water
plants studied could meet the 0.080 mg/L TTHM and 0.060 mg/L HAA5 MCLs,
with a 20 percent safety factor (i.e., 0.064 mg/L and 0.048 mg/L,
respectively) using GAC with 10 minutes of empty bed contact time and a
120 day reactivation frequency, and 78 percent of the plants could meet
the MCLs with a 20 percent safety factor using GAC with 20 minutes of
empty bed contact time and a 240 day reactivation frequency. Because
the treatment studies were conducted at plants with much poorer water
quality than the national average, EPA believes that much higher
percentages of plants nationwide could meet the MCLs with the proposed
GAC BATs.
    Among plants using GAC, larger systems would likely realize an
economic benefit from on-site reactivation, which could allow them to
use smaller, 10-minute empty bed contact time contactors with more
frequent reactivation (i.e., 120 days or less). Most small systems
would not find it economically advantageous to install on-site carbon
reactivation facilities, and thus would opt for larger, 20-minute empty
bed contact time contactors, with less frequent carbon replacement
(i.e., 240 days or less).
    The Information Collection Rule treatment study results also
demonstrated that nanofiltration was the better DBP control technology
for ground water sources with high TOC concentrations (i.e., above
approximately 6 mg/L). The results of the membrane treatment studies
showed that all ground water plants could meet the 0.080 mg/L TTHM and
0.060 mg/L HAA5 MCLs, with a 20% safety factor (i.e., 0.064 mg/L and
0.048 mg/L, respectively) at the system average distribution system
residence time using nanofiltration. Nanofiltration would be less
expensive than GAC for high TOC ground waters, which generally require
minimal pretreatment prior to the membrane process. Also,
nanofiltration is an accepted technology for treatment of high TOC
ground waters in Florida and parts of the Southwest, areas of the
country with elevated TOC levels in ground waters.
    The second method that EPA used to examine alternatives for BAT was
the Surface Water Analytical Tool model that was developed to compare
alternative regulatory strategies as part of the Stage 1 and Stage 2 M-
DBP Advisory Committee deliberations. EPA modeled a number of BAT
options. In the model, GAC10 was defined as granular activated carbon
with an empty bed contact time of 10 minutes and a reactivation or
replacement interval of 90 days or longer. GAC20 was defined as
granular activated carbon with an empty bed contact time of 20 minutes
and a reactivation or replacement interval of 90 days or longer.
    The compliance percentages forecasted by the SWAT model are
indicated in Table IV.D-1. EPA estimates that more than 97 percent of
large systems will be able to achieve the Stage 2 MCLs with the GAC
BAT, regardless of post-disinfection choice (Seidel Memo, 2001).
Because the source water quality (e.g., DBP precursor levels) in medium
and small systems is expected to be comparable to or better than that
for the large system (USEPA 2005f), EPA believes it is conservative to
assume that at least 90 percent of medium and small systems will be
able to achieve the Stage 2 MCLs if they were to apply one of the
proposed GAC BATs. EPA assumes that small systems may adopt GAC20 in a
replacement mode (with replacement every 240 days) over GAC10 because
it may not be economically feasible for some small systems to install
and operate an on-site GAC reactivation facility. Moreover, some small
systems may find nanofiltration cheaper than the GAC20 in a replacement
mode if their specific geographic locations cause a relatively high
cost for routine GAC shipment.

 Table IV.D-1.--SWAT Model Predictions of Percent of Large Plants in Compliance With TTHM and HAA5 Stage 2 MCLs After Application of Specified Treatment
                                                                      Technologies
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                                                          Compliance with 0.080 mg/L TTHM and 0.060 mg/L  Compliance with 0.064 mg/L TTHM and 0.048 mg/L
                                                                            HAA5 LRAAs                       HAA5 LRAAs (MCLs with 20% Safety factor)
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