OSEPA/PAPER INDUSTRY COOPERATIVE DIOXIN STUDY
"The 104 Mill Study"
SUMMARY REPORT
July 1990
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
Office of Water Regulations and Standards
401 M Street, S.W.
Washington/ D.c. 20460
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USEPA/PAPER INDUSTRY COOPERATIVE DIOXIN STUDY
"The 104 Mill Study"
SUMMARY REPORT
Table of Contents
Page
A. Introduction 1
B. Principal Findings and Conclusions 2
C. Study Features 5
1. Mills Included in the 104 Mill Study 5
2. Field Sampling Program 5
3. Analytical Program 6
4. Data Handling 7
D. Industry Profile 8
1. Pulping and Bleaching 8
2. Bleach Line Chemical Usage 9
3. Wastewater Treatment 11
E. Summary of Results 12
1. Bleached Pulps 13
2. Wastewater Effluents and Wastewater Sludges 14
3. Mass Flows Of 2378-TCDD/TCDF 16
4. Bleaching Practice and Formation of 18
2378-TCDD/TCDF in Kraft Mills
5. Kraft Mill Wastewater Treatment Findings 20
6. Other 2378-Substituted CDDs and CDFs 22
References 27
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U8EPA/PAPER INDUSTRY COOPERATIVE DIOXIN STUDY
»Th« 104 Mill Study"
SUMMARY REPORT
A. Introduction
In October of 1987 the U.S. Environmental Protection Agency
(EPA) and the U.S. pulp and paper industry jointly released
preliminary results from a screening study that provided the first
comprehensive data on formation and discharge of chlorinated
dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs) from pulp and
paper mills (1) . This early screening study of five bleached kraft
mills ("Five Mill Study") confirmed that the pulp bleaching process
was primarily responsible for the formation of the CDDs and CDFs.
The study results showed that 2378-TCDD was present in seven of
nine bleached pulps, five of five wastewater treatment sludges, and
three of five treated wastewater effluents. The study results also
indicated that 2,3,7,8-tetrachlorodibenzo-p-dioxin (2378-TCDD) and
2,3,7,8-tetrachlorodibenzofuran (2378-TCDF) were the principal CDDs
and CDFs formed. The partitioning of these compounds between the
bleached pulp, wastewater treatment sludge, and final wastewater
effluent was found to be highly variable among the five mills. The
final Five Mill Study report was published in March 1988 (2).
To provide the EPA with more complete data on the release of
these compounds by the U.S. industry, an agreement was reached in
April 1988 between EPA and the industry to conduct a second study
to characterize the 104 U.S. mills that practice chlorine bleaching
of chemically produced pulps (3) . The scope of the study was
developed by EPA and industry, and the study was managed by the
National Council of the Paper Industry for Air and Stream
Improvement, Inc., (NCASI), with EPA overview. The data from this
study provide an estimate of the release of 2378-TCDD and 2378-TCDF
in three environmental export vectors (bleached pulp, wastewater
sludge, and wastewater effluent) from the U.S. pulp and paper
industry as of mid to late 1988.
This summary report presents the major features of the study
design, sample collection, and analytical methodologies; a profile
of the industry at the time the study was conducted in terms of
number and types of mills, number and types of bleach lines, bleach
line operating characteristics during sampling, and wastewater
treatment; and the study results. This report and a statistical
analysis of the data from the study were prepared independently by
USEPA (4). The paper industry, through NCASI, has also prepared
a report of the 104 Mill Study (5) . Preliminary study results were
presented by NCASI and EPA in September 1989 (6) , and will be
published in Chemosphere. This report includes analytical data
received by EPA from NCASI as of April 1990. These data comprise
virtually all of the analytical data required by the study
objectives.
When reviewing the study results, it is important to keep in
mind the principal objective of the 104 Mill Study was to
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characterize exports from the 104 mills in terms of 2378-TCDD and
2378-TCDF. The study was not designed to address mechanisms of
formation of these compounds or to determine what are the best
technologies for minimizing formation or treating these compounds
in wastewaters. Nonetheless, the study results permit some useful
observations in these areas.
The terms used in this report to describe CDDs and CDFs, and
pulping, bleaching and wastewater treatment in the pulp and paper
industry are defined in the glossary for the Five Mill Study (2).
B. Principal Findings and Conclusions
Industry Profile
1. At the time the 104 Mill Study field program was underway
(mid to late 1988 for most mills), the U.S. pulp and paper industry
was characterized by only limited application of those pulping and
bleaching technologies and operating practices that have been
demonstrated to have the potential to reduce formation of 2378-
TCDD/TCDF. Since that time, many mill operators have been
implementing programs designed to improve pulping and bleaching
technologies and operating practices.
Data Summary
2. Analyses of field and laboratory duplicate samples
indicated excellent agreement. Consequently, the proportion of
total variability in 2378-TCDD/TCDF concentrations which could be
attributed to variability in field sampling, or sample handling and
analytical techniques, was in all cases small relative to other
sources of variability, which are generally attributed to the
process.
3. The analytical techniques used are suitable for low-level
determinations of 2378-TCDD and 2378-TCDF in kraft mill effluents
(i.e., at or below 0.010 ng/kg, or 10 ppq); and, for determinations
of 2378-TCDD and 2378-TCDF in bleached pulps and wastewater sludges
in the range of 1 ng/kg (or 1 ppt). Target analytical detection
levels were achieved or exceeded for most samples and valid data
were obtained for nearly all samples.
4. 2378-TCDD and 2378-TCDF were detected in samples from
bleached kraft and bleached sulfite mills as follows:
Kraft Mills Sulfite Mills
2378-TCDD 90 % 56 %
2378-TCDF 97 % 85 %
No mill was found to be free of 2378-TCDD/TCDF.
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5. Detected concentrations of 2378-TCDD and 2378-TCDF were
best approximated by lognormal distributions for each of the export
vectors: bleached pulp, wastewater sludge and wastewater effluent.
6. The data on concentrations of 2378-TCDD and 2378-TCDF found
in the export matrices are summarized below. The number of samples
with non-detect analyses (ND's) are listed for each matrix. The
mean, median, 90th percentile and maximum values are based upon
samples with detected concentrations of 2378-TCDD or 2378-TCDF.
Non-detect results were not included in the statistics.
(results in no/kg. or ppt)
Number of Samples
Detects ND's Mean Median 90% Maximum
Bleached Pulps
Kraft Hardwood
2378-TCDD 62 12 7.5 4.0 17 56
2378-TCDF 72 2 56 17 107 661
Kraft Softwood
2378-TCDD 98 6 12 7.6 27 116
2378-TCDF 99 3 118 26 185 2620
Sulfite Hardwood
2378-TCDD 3 5 7.1 4.4 15 15
2378-TCDF 5 3 73 9.9 323 323
Sulfite Softwood
2378-TCDD 1 7 3.5 3.5 3.5 3.5
2378-TCDF 7 2 125 6.3 449 449
Wastewater Effluents
Kraft Mills
2378-TCDD 90 17
2378-TCDF 104 7
Sulfite Mills
2378-TCDD 12 13
2378-TCDF 21 4
0.076
0.48
0.013
0.11
0.035
0.10
0.012
0.035
0.19
1.1
0.023
0.38
0.64
8.4
0.023
0.84
Wastewater Sludges
Kraft Mills
2378-TCDD 94
2378-TCDF 97
Sulfite Mills
2378-TCDD 18
2378-TCDF 16
3
0
1
0
101
796
13
99
39
161
4.7
63
203
1728
48
350
1390
17100
58
584
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Partitioning of 2378-TCDD/TCDF
7. The partitioning of 2378-TCDD and 2378-TCDF to export
vectors within mills was found to be highly consistent at most
kraft mills.
8. The partitioning of 2378-TCDD and 2378-TCDF to export
vectors was highly variable between mills. For all kraft mills,
about 38 % of the 2378-TCDD was partitioned to pulps, 33 % to
wastewater sludges and 29 % to wastewater effluents.
9. The estimated annualized mass output rates of 2378-TCDD and
2378-TCDF for the kraft and sulfite segment of the U.S. industry
at the time of the study were estimated at 1.46 Ibs (0.66 kg) and
11.7 Ibs (5.31 kg), respectively.
Bleach Plant Practice and Formation of 2378-TCDD/TCDF
10. The formation rates of 2378-TCDD and 2378-TCDF are likely
to be somewhat higher than the output rates cited above since the
amounts of these compounds that may be partitioned to settled
sludges in aerated stabilization basins was not quantified in the
sampling program.
11. Correlations between mass export rates of 2378-TCDD/TCDF
and a series of kraft mill operating parameters were generally
poor. However, positive trends were observed between average
formation of 2378-TCDD/TCDF and application of chlorine in the C-
Stage and with chlorine multiple (Kappa factor). Increased
application of chlorine generally resulted in increased formation
of 2378-TCDD/TCDF. Increased substitution of chlorine dioxide
generally resulted in decreased formation of 2378-TCDD/TCDF.
Wastewater Treatment
12. On average, mills with activated sludge wastewater
treatment systems exported less 2378-TCDD/TCDF to wastewater
effluents and more to wastewater sludges than mills with aerated
stabilization basin treatment.
13. Correlations between Total Suspended Solids concentrations
and 2378-TCDD/TCDF mass outputs for kraft mills were weak,
suggesting that TSS levels were at best only partially predictive
of 2378-TCDD/TCDF levels in wastewater effluent and wastewater
sludge.
2378-Substituted CDDs and CDFs
14. In addition to 2378-TCDD and 2378-TCDF, the most
frequently occurring 2378-substituted CDDs and CDFs found in mill
exports from nine of the 104 mills included 1234678-HpCDD, OCDD,
12378- and 23478-PeCDF and OCDF.
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15. When considered in terms of both the EPA and the I-TEF
toxic equivalency approaches, 2378-TCDD and 2378-TCDF account for
the vast majority of the computed 2378-TCDD equivalent toxicity in
each mill export. Accordingly, current U.S. regulatory programs
that are focused on these compounds appear to be properly directed.
C. Study Features
1. Mills included in the 104 Mill Study
All U.S. pulp and paper mills where chemically produced wood
pulps are bleached with chlorine and chlorine derivatives were
included in the Agreement for the 104 Mill Study (3) . However, six
bleached kraft mills were not sampled as part of the study. These
included the five mills sampled for the Five Mill Study and the
Consolidated Papers mill located at Wisconsin Rapids, Wisconsin.
Consolidated Papers had independently conducted a study at the
Wisconsin Rapids mill. Although mills included in the Five Mill
Study were not resampled in the 104 Mill Study, 2378-TCDD/TCDF data
and mill operating and wastewater treatment information from the
Five Mill Study have been included in this analysis. Due to
differences in sampling and analytical protocols, the Consolidated
Papers data for 2378-TCDD/TCDF were not included. However, mill
operating and wastewater treatment information for Consolidated
Papers were included in the industry profiles presented in Section
D.
2. Field Sampling Program
The Agreement required that each significant export vector
(fully bleached pulp, wastewater sludge, final wastewater effluent)
be sampled and the samples composited over a five day period (3).
In most cases the composite samples were comprised of up to eight
aliquots obtained throughout the sampling day. Nearly all sampling
was performed by mill personnel following guidance established by
NCASI. In a few cases, NCASI personnel conducted the sampling.
The sampling protocols closely followed those established for the
Five Mill Study (2).
The pulp samples taken were representative of the highest
brightness pulp produced at each bleach line. Hence, at a mill
with two bleach lines, where hardwood and softwood pulps are
bleached separately, separate hardwood and softwood composite pulp
samples were collected. At a mill with a single bleach line where
both hardwood and softwood pulps are bleached (i.e., a swing line),
sampling was conducted intermittently to ensure the five day
composite samples were composed of only hardwood or softwood pulp.
At a limited number of mills hardwood/softwood brownstock pulp
mixtures are bleached. Bleached pulp from those lines were sampled
as noted above for single bleach lines.
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Sludge samples consisted of only those sludges removed from
the wastewater treatment system and disposed of in landfills, by
incineration, or by other methods. Thus, for mills with activated
sludge wastewater treatment systems, the sludges sampled generally
consisted of combined primary and secondary sludge; for mills with
aerated stabilization basins, only primary sludges were sampled.
Although in most cases the sludges sampled were dewatered prior to
offsite disposal, several primary sludges were collected in a low
consistency slurry form.
More than 90 effluents sampled were collected from mills with
biological treatment. For eight mills, the samples consisted of
partially treated effluents prior to discharge to municipal
wastewater treatment plants. Untreated effluents from two mills
with direct ocean discharges were sampled. An untreated effluent
from a mill with a percolation pond for wastewater disposal was
also sampled.
This sampling scheme generated over 400 samples for isomer-
specific 2378-TCDD and 2378-TCDF analyses. About 80 additional
samples were collected as part of the quality assurance/quality
control plan. These samples were analyzed as field duplicates
and/or included in native spike determinations. Samples of each
export vector from 9 mills were analyzed for all 2378-substituted
CDDs and CDFs. The nine mills were chosen by NCASI to represent a
variety of bleaching and wastewater treatment configurations.
In addition to the physical samples, mill operators were
required to provide process operating data for bleacheries and
wastewater treatment plants. These data were collected to document
operation of the processes at the time of sampling.
3. Analytical Program
The Brehm Laboratory at Wright State University (WSU) , Dayton,
Ohio, performed analytical methods development work for isomer-
specific determinations of 2378-TCDD and 2378-TCDF in pulp and
paper mill matrices, and completed analyses of all samples for the
Five Mill Study (2). Analytical work for this study was conducted
by Enseco-California Analytical Laboratories (CAL) in West
Sacramento, California, and WSU. Enseco-CAL analyzed most of the
sludge and effluent samples, while WSU analyzed most of the pulp
samples.
The analytical methods used in the 104 Mill Study were
consistent with the screening study protocols established for the
"Five Mill Study" (2). Analytical objectives for target detection
limits for 2378-TCDD and 2378-TCDF were 1 ng/kg(ppt) for sludges
and pulps, and 0.01 ng/kg(ppt) for wastewater effluents. The
Agreement specified identification and quantitation criteria for
2378-TCDD/TCDF and required that NCASI manage quality
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assurance/quality control programs for the study. NCASI staff
performed and coordinated sample preparation, submitting samples
to the analytical laboratories, and reviewing laboratory data
reports. Nearly all analytical results met the quality
assurance/quality control objectives established for the study.
Less than six percent of the samples required more than one
analysis to obtain valid data. This was judged by EPA to be a
reasonably small proportion given the study objectives for minimum
detection levels and the complexity of the analyses in terms of
sample extraction and analyte recovery, identification and
quantitation.
4. Data Handling
To ensure consistent reporting of bleach plant and wastewater
treatment information, NCASI developed specific forms for use by
mill personnel to report bleach line operating characteristics,
bleach line chemical applications and wastewater treatment
operations. Copies of these forms, as well as schematic diagrams
of the bleacheries and wastewater treatment facilities, were
provided to EPA by NCASI for most mills. For those few mills for
which confidential treatment of certain data were requested, the
forms were submitted directly to EPA by mill operators. NCASI
submitted final analytical results to EPA as they were developed,
in conformance with the quality assurance/quality control protocols
specified in the Agreement.
EPA and NCASI independently developed data summaries in
spreadsheet format to characterize bleach line operating
characteristics; mass flow rates of bleached pulp, wastewater
sludge and wastewater effluent; and, mass flows of 2378-TCDD and
2378-TCDF in the mill exports. The respective spreadsheet entries
were compared several times and corrections were made as
appropriate. Prior to conducting detailed statistical analyses,
EPA had a contractor further compare the EPA spreadsheets against
the original report forms. All discrepancies were resolved and the
spreadsheets were updated accordingly. New databases were then
created by uploading the data from the spreadsheets to the EPA
mainframe computer.
As data were received from NCASI, the Industrial Technology
Division compiled summaries of bleached pulp, wastewater sludge and
wastewater effluent concentrations and distributed the results to
EPA regional offices and state agencies. On May 4, 1989, EPA
determined that certain bleach plant process data supplied by mill
operators should be provided confidential treatment, but that
bleached pulp data for 2378-TCDD/TCDF and other miscellaneous
bleach plant data were not confidential. The data summaries
presented in this report do not disclose confidential bleach plant
data.
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8
D. Industry Profile
1. Pulping and Bleaching
Tables 1 and 2 present the profiles for pulping and bleaching,
respectively, for those mills included in the study. This segment
of the U.S. industry is comprised of 86 kraft pulping mills, 16
sulfite mills, one soda mill and one mill with both kraft and
sulfite pulping. More than half of the bleach lines at kraft mills
are used for bleaching softwoods exclusively and forty percent for
bleaching hardwoods. The balance are either swing lines or are
used to bleach hardwood/softwood pulp mixtures. For sulfite mills,
half the bleach lines are used for bleaching softwood pulps, nearly
40% for hardwood pulps and the balance for mixed pulps.
Table 1: Industry Profile - Pulping
Number of Mills
Kraft 86
Sulfite 16
Kraft and Sulfite 1
Soda 1
Total 104
Table 2: Industry Profile - Bleaching
Number of Bleach Lines
Kraft Sulfite Soda
Hardwood 67 7 1
Softwood 89 9
Mixed HW/SW 9 2 -
Total 165 18 1
Note: (1) Kraft hardwood and softwood bleach line data
include 14 swing lines. Each swing line was
counted as both a hardwood and a softwood line,
where appropriate; or, as two hardwood or
softwood lines where multiple grades of the
same species were bleached.
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2. Bleach Line Chemical Usage
Table 3 presents a summary of the number and percentage of
bleach lines with oxygen delignification systems and chemical use
in pre-bleaching and final bleaching. The data were provided by
mill operators to characterize operations during the sampling
surveys.
Table 3: Industry Profile - Bleach Line Chemical Usage
Number of Bleach Lines,(%)
Kraft and Soda Sulfite
Oxygen Delignification 7 (4.2) 1 ( 5.6)
Pre-bleaching
Chlorine Stage C12 166 (100) 16 (89)
Chlorine Stage C102 106 (64) 1 ( 5.6)
Extraction Stage 02 79 ( 48) 4 (22)
Extraction Stage NaOCl 47(28) 1(5.6)
Extraction Stage H202 2( 1.2) 1(5.6)
Final Bleaching
C102 148 (89) 4 (22)
NaOCl 90 ( 54) 14 (78)
H202 25 (15) 1 ( 5.6)
As shown above, the industry was characterized by low
utilization of oxygen delignification, relatively low utilization
of oxygen reinforced extraction, low utilization of peroxide
reinforced extraction, and relatively high utilization of
hypochlorite in both pre-bleaching and final bleaching.
The status of bleachery operations of the U.S. industry in mid
to late 1988 with respect to chlorine usage and chlorine dioxide
substitution is summarized in Table 4. Note that about 35 % of the
kraft mill bleach lines were operated with no chlorine dioxide in
the Chlorine Stage (C-Stage) , and less than 2 % had chlorine
dioxide substitution rates greater than 50 %, a level which has
been demonstrated to have significant positive effects for
minimizing formation of several chlorinated organic compounds, and
2378-TCDD/TCDF in particular (7).
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10
Table 4: Status of U.S. Bleachery Operations
C-Staoe Chlorination and Chlorine Dioxide
Substitution (1988)
Chlorine Application
Ibs C12/ton ADBSP Bleach Lines
C102 Substitution
percent Bleach Lines
< 40 Ibs/ton
40-60
60-80
80-100
100-120
120-140
> 140
TOTAL
< 40 Ibs/ton
40-60
60-80
80-100
100-120
120-140
> 140
Kraft Mill Bleach Lines
15
22
32
36
28
16
16
165
0 %
< 5
5-10
10 - 20
20 - 30
30 - 40
40 - 50
50 - 60
60 - 70
> 70
Sulfite Mill Bleach Lines
TOTAL
2
1
2
6
3
4
0
18
0 %
< 5
> 5
TOTAL
TOTAL
59
16
41
33
9
1
3
1
1
1
165
17
1
0
18
Notes: (1)
(2)
Bleachery operations for swing lines were counted
separately for hardwood and softwood pulps.
ADBSP - Air-dried brownstock pulp.
Table 5 presents a summary of 5 day average chlorine multiples
(Kappa factor) determined for kraft and sulfite bleach lines at the
time of sampling. The chlorine multiple is the ratio of the amount
of active chlorine used in pulp bleaching in the C-Stage, to the
amount of lignin contained in brownstock or oxygen delignified pulp
as characterized by the Kappa number. At the time of the mill
sampling programs, 11 per cent of bleach lines were operated with
average chlorine multiples less than 0.15, a level which has been
cited as a threshold below which formation of 2378-TCDD/TCDF is
greatly reduced (7) . The average chlorine multiple over an
extended period may not be a good measure of the 2378-TCDD/TCDF-
forming potential of a pre-bleaching operation since short term
variations above 0.15 are thought to be significant.
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11
<
0.10 - <
0.15 - <
0.20 - <
0.25 - <
: 0.10
: 0.15
: 0.20
: 0.25
: 0.30
Table 5: C-Staae Chlorine Multiple (Kappa Factor)
Number of Bleach Lines
Chlorine Multiple Kraft Sulfite
4 2
15 1
51 6
54 3
17
> 0.30 14 6
Total 155 18
Notes: (1) Chlorine multiple was computed from active
chlorine (C12 and C102) applied in the C-Stage.
(2) Chlorine multiples could not be computed for
ten kraft mill bleach lines because of
incomplete data.
On balance, pulping and bleaching facilities were not operated
to minimize formation of 2378-TCDD/TCDF at the time of the 104 Mill
Study. Presently, there are several bleachery upgrades underway,
many of which include partial extended delignification, increasing
capability for chlorine dioxide substitution, modification of
caustic extraction systems and installation of oxygen
delignification systems.
3. Wastewater Treatment
The status of wastewater treatment provided at the 104 mills
is summarized in Table 6. The industry standard is primary
treatment followed by secondary biological treatment. Eight mills
discharge to POTWs after primary treatment and two have no
treatment. Wastewaters from one mill are disposed of in a
percolation pond. For the kraft segment, about 35 % of the mills
have activated sludge treatment and more than half have aerated
stabilization basins. For sulfite mills, nearly 70 % have
activated sludge systems and nearly 20 % have aerated stabilization
basins.
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Table 6: Industry Profile - Wastewater Treatment
Number of Mills
Kraft Sulfite Soda Total
Activated Sludge 32 11 - 43
Aerated Stabilization Basin 45 3 1 49
Discharge to POTW 71 8
Discharge to Other Mill WWTP - 1 - 1
Percolation Pond 1 - l
No Treatment 2 - - 2
Total 87 16 1 104
Note: (1) The mill with kraft and sulfite pulping was
listed as a kraft mill for purposes of this
table.
E. Summary of Results
Examination of analytical data from samples collected at each
mill indicated detected concentrations of 2378-TCDD/TCDF were best
approximated by lognormal distributions, estimated separately for
each of the export matrices: bleached pulp, sludge, and effluent.
Estimates of non-detected measurements were required for the
analyses of results. For the purposes of this study, these
measurements were assigned a value equal to half the detection
limit. This compromise procedure has been used in other studies
and enables information from non-detect samples to be utilized (4) .
This procedure was judged reasonable in light of the significant
proportion of all samples with detectable concentrations of 2378-
TCDD/TCDF, and the consistent partitioning of 2378-TCDD and 2378-
TCDF within mills. In this study, and in the Five Mill Study, no
mill was found to be free of 2378-TCDD/TCDF.
About 30% of all the samples analyzed were field duplicate
samples or laboratory-split duplicate samples. Analysis of these
duplicate samples indicated that within each matrix (pulp, sludge
and effluent), excellent agreement was shown between repeated
measurements of 2378-TCDD/TCDF concentration. Most correlations
between pairs of duplicate measurements were found to be greater
than 0.95. Consequently, the proportion of total variability in
2378-TCDD/TCDF levels which could be attributed to variability in
field sampling protocol or analytical technique was in all cases
small relative to other sources of variability, which are generally
attributed to the pulping and bleaching processes. This finding
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13
supports averaging of duplicate pair results for purposes of
estimating mass flow rates of 2378-TCDD/TCDF, as was done in this
study.
The analytical techniques used are suitable for low-level
determinations (i.e., in the range of and below 0.010 ng/kg, (10
ppq))i of 2378-TCDD/TCDF in kraft mill wastewater effluents.
Analysis of sulfite mill effluents may not be as precise over a
larger range. The study results also indicate the analytical
methods are suitable for determinations of 2378-TCDD/TCDF in the
range of 1 ng/kg (1 ppt) for bleached pulps and wastewater sludges.
1. Bleached Pulps
Summary statistics of 2378-TCDD/TCDF concentrations expressed
as ng/kg(ppt) in the bleached pulps are presented in Table 7. The
data are reported by pulping type (kraft and sulfite) as well as
by wood specie (hardwood and softwood). The statistics include
number of samples with non-detect results, number of samples with
detectable results, and mean, median, 90th percentile and maximum
concentrations. Non-detect analytical results were not included
for calculation of mean, median and 90th percentile concentrations.
Table 7: 2378-TCDD/TCDF Concentrations in Bleached Pulps
Number of
Samples
ND Detect
HW Kraft Pulps
2378-TCDD 12
2378-TCDF 2
SW Kraft Pulps
2378-TCDD 6
2378-TCDF 3
HW Sulfite Pulps
2378-TCDD 5
2378-TCDF 3
SW Sulfite Pulps
2378-TCDD 7
2378-TCDF 2
62
72
98
99
3
5
1
7
Mean
fnq/ka)
7.5
56
12
118
7.1
73
3.5
125
Median
fnq/kg)
4.0
17
7.6
26
4.4
9.9
3.5
6.3
90 %
fna/kcn
17
107
27
185
15
323
3.5
449
Maximum
fna/kq)
56
661
116
2620
15
323
3.5
449
Note that these findings are representative of the 104 mills
as of mid to late 1988 when most of the sampling was completed.
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14
Since that time several mill operators have been implementing
process changes designed to reduce 2378-TCDD/TCDF concentrations
in bleached pulps. Although the net effect of these changes on
formation of 2378-TCDD/TCDF is not fully known or quantified at
this time, examination of preliminary results supplied by mill
operators indicate significant reductions in formation of 2378-
TCDD/TCDF may be possible.
Correlating the above pulp findings with pulping or bleach
plant process parameters was significantly limited because 2378-
TCDD/TCDF concentrations in bleached pulp represent only a portion
of that formed in the bleach plant. The "Five Mill Study" clearly
demonstrated that bleach plant filtrates represented a significant
fraction of the total mass of 2378-TCDD/TCDF formed, and the
distribution between the pulp and filtrate phases was highly
variable from mill to mill (1,2). That finding was confirmed by
the more extensive data obtained from this study, (see Section
D.3). Hence, correlations of bleach plant operations with only
pulp data would not be valid and are not presented. Because it was
not the objective of this study to fully investigate the impact of
pulping and bleaching process parameters on 2378-TCDD/TCDF
formation in the bleach plant, filtrate samples were not collected.
2. Wastewater Effluents and Wastewater Sludges
Tables 8 and 9 present summary statistics of 2378-TCDD/TCDF
concentrations in wastewater effluents and sludges, respectively.
The summary statistics are the same as those presented for bleached
pulps in Table 7. Data for kraft mills and sulfite mills are
distinguished. Samples of wastewater sludge slurries obtained at
a number of mills (generally less than 5% solids) were analyzed as
liquids. Although these data were not included in Table 9, they
were considered in mass flow calculations for the respective
mills.
Table 8: 2378-TCDD/TCDF Concentrations in Wastewater Effluents
Number of
Samples Mean Median 90 % Maximum
ND Detect (ng/kg) (na/ka) fna/ka) (na/kg)
Kraft Mills
2378-TCDD 17 90 0.076 0.035 0.19 0.64
2378-TCDF 7 104 0.48 0.10 1.1 8.4
Sulfite Mills
2378-TCDD 13 12 0.013 0.012 0.023 0.023
2378-TCDF 4 21 0.11 0.035 0.38 0.84
Note: (1) A few mills have more than one wastewater effluent.
All available effluent data are included.
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15
Table 9: 2378-TCDD/TCDF Concentrations in Wastewater Sludges
Number of
Samples
ND Detect
Kraft Mills
2378-TCDD
2378-TCDF
Sulfite Mills
2378-TCDD
2378-TCDF
3
0
1
0
94
97
18
16
Mean
(nq/kq)
101
796
13
99
Median 90 %
fnq/kg) fnq/kq)
39
161
4.7
63
203
1728
48
350
Maximum
(nq/kg)
1,390
17,100
58
584
Note: (1) Analytical results for dewatered sludges are included;
results for sludge slurries are not included.
The effluent and sludge concentrations measured for sulfite
mills were generally less than those for kraft mills, as was the
case for bleached pulps described in Table 7. In all exports, the
concentrations of 2378-TCDD/TCDF were found to be highly variable
and distributed lognormally. Figure 1 presents the distribution
of 2378-TCDD in wastewater effluents. Distributions of 2378-TCDD
and 2378-TCDF were similar for all exports.
Figure 1
EFFLUENT TCDD
PROBABILITY PLOT: DETECTED VALUES ONLY
o
3
N
o
c
00
o
-1
-2
-3
10 100 1000
TCDD Concentration in PPQ
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16
3. Mass Flows of 2378-TCDD/TCDF
Rates of 2378-TCDD/TCDF mass flow were computed for all
matrices at each mill by combining the 2378-TCDD/TCDF concentration
data with mill production rates of pulp, sludge and effluent.
Estimates of mass output rates of 2378-TCDD and 2378-TCDF at U.S.
bleached pulp mills were 1.46 Ibs/yr (0.66 kg/yr) and 11.7 Ibs/yr
(5.31 kg/yr), respectively. Output rates varied substantially from
mill to mill. Comparisons showed that significantly more 2378-
TCDD/TCDF was exported at kraft mills than at sulfite mills.
The summary statistics of total mill exports of 2378-TCDD/TCDF
from kraft and sulfite mills are highlighted in Table 10. These
results are presented in terms of Ibs/ton of air-dried brownstock
pulp (ADBSP) and include data from only those mills with complete
mass flow data for pulp, sludge, and effluent and complete
analytical data for 2378-TCDD/TCDF.
Note that calculated total mill mass flow rates for mills with
aerated stabilization basins may not fully reflect the rates of
formation of 2378-TCDD/TCDF. The results for those mills are
probably biased low due to retention of 2378-TCDD/TCDF in sludge
in aerated lagoons which would not have been characterized by the
sampling program. Accordingly, the results presented are believed
to be representative of total mill exports for all mills at the
time of sampling, but not necessarily fully representative of the
total amount of 2378-TCDD/TCDF formed.
Table 10: Total Mill Exports of 2378-TCDD/TCDF
(Results in 10-8 Ibs/ton ADBSP)
Kraft Mills
2378-TCDD
2378-TCDF
Sulfite Mills
2378-TCDD
2378-TCDF
Number of
Mills
80
80
14
14
Mean Median 90 % Maximum
4.9
48
1.0
14
2.8
10
0.46
3.5
12
123
3.3
73
31
954
4.5
145
Notes: (1) Only results for mills with complete analytical and
mass flow data are included.
(2) Mass flow calculations for several mills are
affected by sludge retention in aerated
stabilization basins.
(3) ADBSP - Air-Dried Brownstock Pulp
-------
17
Figure 2 illustrates the distribution of estimated mass flows
of 2378-TCDD among pulp, effluent and sludge for kraft and sulfite
mills on an industry-wide basis.
Figure 2
TOTAL OUTPUT: TCDD
KRAFT MILLS
PULP
EFFLUENT
SULFITE MILLS
PULP
EFFLUENT
SLUDGE
SLUDGE
The high variability of the partitioning of 2378-TCDD among
exports on a mill to mill basis is highlighted in Figure 3. The
results for 2378-TCDF were similar. Each boxplot shown in Figure
3 was constructed such that the top and bottom edges of the box
represent the upper and lower quartiles of the distribution of
percentages taken across all mills. The line dividing each box is
the median, and the middle 95% of all data is depicted by the
extensions above and below each box.
-------
18
Figure 3
% OUTPUT BY MATRIX
TCDD
Q
Q
3
a
100
80
60
40
20
Matrix
As was the case with the Five Mill Study results, within-mill
partitioning of 2378-TCDD among mill exports compared to that of
2378-TCDF was found to be consistent. Although statistical
analyses were not conducted to fully examine this phenomenon, the
maximum difference between partitioning of 2378-TCDD and 2378-TCDF
among pulp, sludge and effluent at 80 % of kraft mills was found
to be less than 20 %.
4. Bleaching Practice and Formation of 2378-TCDD/TCDF
in Kraft Mills
Analyses were completed on the effects of mill bleaching
procedures upon formation of 2378-TCDD/TCDF. Correlations between
mass export rates of 2378-TCDD/TCDF and a series of mill parameters
(including application rates of bleaching and extraction chemicals)
were generally quite low. Consequently, linear regressions of the
2378-TCDD/TCDF export rates fit to each bleaching parameter were
found to be poor predictors of individual mill outputs. However,
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19
significant positive trends were observed between average 2378-
TCDD/TCDF formation and the rate of application of chlorine in the
C-Stage.
Figure 4 is a plot of 2378-TCDD formed, as characterized by
export vector measurements, vs chlorine applied in the C-Stage for
kraft mills. The data indicate a general trend of increasing 2378-
TCDD with increasing chlorine application; although, as noted
above, there appears to be only a weak correlation. Plots of 2378-
TCDD vs chlorine ratio or kappa factor for all kraft mills yielded
similar results. Increased substitution of chlorine dioxide for
chlorine in the C-Stage was weakly correlated with decreased
formation of 2378-TCDD/TCDF mass.
Figure 4
C12 vs. ADJUSTED TOTAL TCDD
KRAFT MILLS ONLY
oo
? 100.00
CO
T3
PU
C/3
Q
Q
(J
H
10.00
1.00
0.10
CO
3
0.01
50
100
150
200
C12 (Ibs/ton ADBSP)
For certain mills, factors other than chlorine application
appear to have had a more significant impact on formation of 2378-
TCDF than on formation of 2378-TCDD. This resulted in
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20
uncharacteristically high ratios of 2378-TCDF to 2378-TCDD. In a
number of cases use of contaminated oil-based defoamers was
reported to be responsible for the unusually high formation of
2378-TCDF. Resampling at a few mills after substitutions were made
confirmed this finding.
5. Kraft Mill Wastewater Treatment Findings
Differences emerged between mills with Aerated Stabilization
Basin (ASB) and Activated Sludge (ACT) wastewater treatment
systems. There was significant evidence that mills using ACT
treatment exported less effluent-based 2378-TCDD/TCDF and more
sludge-based 2378-TCDD/TCDF on average than mills with ASB systems.
This is principally due to differences in management of biological
solids in each type of system; and, the method of sludge sampling
conducted for this study, which did not characterize sludge stored
in ASB systems. Figures 5 and 6 illustrate the above findings for
2378-TCDD. Results for 2378-TCDF were similar.
Figure 5
% OUTPUT BY TREATMENT
EFFLUENT TCDD
Q
Q
U
H
c
u
3
W
100
80
60
40
20
ACT
ASB
Treatment
-------
21
Figure 6
% OUTPUT BY TREATMENT
SLUDGE TCDD
Q
Q
U
9
O
O
60
•o
100
80
60
40
20
ACT
ASB
Treatment
Further investigations were made of possible relationships
between 2378-TCDD/TCDF mass exports in sludge and effluent, type
of wastewater treatment provided, and levels of Total Suspended
Solids (TSS). On average, TSS concentrations in ACT treatment
system effluents were found to be higher than those in ASB
treatment system effluents, (60 mg/1 vs 48 mg/1). Correlations
between effluent concentrations of TSS and 2378-TCDD/TCDF mass
outputs were fairly weak, suggesting that TSS levels were at best
only partially predictive of 2378-TCDD/TCDF partitioning to sludge
and effluent.
When data from ACT and ASB-type mills were combined, a
significant but weakly correlated positive trend was observed
between effluent 2378-TCDD/TCDF mass and TSS concentrations. A
weakly correlated negative trend was observed between TSS and
sludge 2378-TCDD/TCDF. For kraft mills using ACT treatment, higher
TSS levels were associated with higher sludge-based 2378-TCDD/TCDF
exports and lower effluent-based 2378-TCDD/TCDF exports
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22
6. Other 2378-Substituted CDDs and CDFs
Bleached pulp, wastewater sludge and final wastewater effluent
samples from eight kraft mills and one sulfite mill were analyzed
for 2378-substituted CDDs and CDFs, and total CDDs and CDFs by
homologue class, tetra through octa. These analyses were conducted
to test the conclusion drawn in the Five Mill Study that 2378-TCDD
and 2378-TCDF were the principal CDDs and CDFs found in pulp and
paper mill exports, when considered in terms of EPA's toxic
equivalence approach (8).
The analyses were completed by Enseco-CAL. Ten bleached
pulps, 9 wastewater sludges and 9 final wastewater effluents were
analyzed. Duplicate analyses were conducted on one sample from
each matrix. Although there are no reference analytical methods
for many of the 2378-substituted CDDs and CDFs, the data obtained
are considered valid for the purposes intended based upon the
identification and quantitation criteria used, duplicate sample
results and limited matrix spike experiments.
Tables 11, 12 and 13 present summaries of the results obtained
in terms of the median concentration and the range of
concentrations determined for each matrix, respectively.
Examination of the raw data and the data summaries show that the
patterns of isomer profiles were fairly consistent across matrices
within mills. The most common 2378-substituted CDDs and CDFs found
in mill exports, in addition to 2378-TCDD and 2378-TCDF, were
1234678-HpCDD, OCDD, 12378- and 23478-PeCDF, and OCDF. Non-2378-
substituted tetra-, penta- and hexa-CDDs and CDFs were often found
at greater frequency among the nine mills than the corresponding
2378-substituted compounds.
Tables 14 presents the 2378-TCDD toxic equivalent
concentrations (2378-TECs) for the median values presented in
Tables 11, 12 and 13, and for the sample from each matrix
containing the highest concentrations of CDDs and CDFs. The 2378-
TECs were computed using the EPA and the I-TEF toxic equivalency
approaches (8). Table 15 presents comparisons of the percentages
of the 2378-TECs attributable to 2378-TCDD and 2378-TCDF. These
comparisons were made assuming non-detected CDDs and CDFs were
present at the detection level, and were not present, (i.e., zero
concentration). The results indicate, even with the most
conservative assumptions, that 2378-TCDD and 2378-TCDF account for
the vast majority of the 2378-TEC in each sample. This finding is
consistent with results from the Five Mill Study (2).
Bleached pulps manufactured in British Columbia from sawdust
recycled from certain wood treating operations have exhibited
markedly different isomer profiles, with the HxCDDs more prevalent.
Those findings have been linked to pentachlorophenol-based wood
treating operations (9) . This phenomena is not expected in the
United States since such materials are not suspected of being used
as sources of fiber at U.S. pulping or bleaching operations.
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23
Table 11: Pulp and Paper Mill Bleached Pulps
2378-TCDD
Other TCDDs
12378 PeCDD
Other PeCDDs
123478 HxCDD
123678 HxCDD
123789 HxCDD
Other HxCDD
1234678 HpCDD
Other HpCDDs
OCDD
2378-TCDF
Other TCDFs
12378 PeCDF
23478 PeCDF
Other PeCDFs
123478 HXCDF
123678 HXCDF
234678 HXCDF
123789 HXCDF
Other HxCDFs
1234678 HpCDF
1234789 HpCDF
Other HpCDFs
Tetra- throuah Octa-CDDs and CDFs
(Results in
Median
6.4
ND (0.4)
ND (0.3)
ND (0.3)
ND (0.4)
ND (0.5)
ND (0.5)
ND (0.5)
3.3
2.8
46
18
37
ND (0.7)
ND (0.2)
4.5
ND (0.3)
ND (0.3)
ND (0.3)
ND (0.3)
ND (0.4)
ND (0.6)
ND (0.6)
ND (0.6)
ng/kg, or ppt)
No. of Detects
Rancre (10 samples)
0.4 to 124
ND (0.2) to 7.0
ND (0.1) to 1.4
ND (0.1) to 2.1
ND (0.2) to 0.4
ND (0.2) to 1.6
ND (0.2) to 0.5
ND (0.2) to 8.8
2.3 to 8.4
1.9 to 8.4
28 to 81
1.4 to 716
2.7 to 810
ND (0.1) to 3.9
ND (0.1) to 4.7
ND (0.2) to 17
ND (0.2) to ND (0.6)
ND (0.1) to ND (0.4)
ND (0.2) to ND (0.4)
ND (0.1) to ND (0.4)
ND (0.2) to 1.7
ND (0.1) to 0.8
ND (0.1) to ND (2.1)
ND (0.1) to 2.3
10
2
2
3
1
2
1
3
10
10
10
10
10
4
3
9
0
0
0
0
4
3
0
3
OCDF
2.2
ND (2.8) to 4.3
8
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24
Table 12: Pulp and Paper Mill Wastewater Sludges
2378-TCDD
Other TCDDs
12378 PeCDD
Other PeCDDs
123478 HXCDD
123678 HxCDD
123789 HXCDD
Other HxCDD
1234678 HpCDD
Other HpCDDs
OCDD
2378-TCDF
Other TCDFs
12378 PeCDF
23478 PeCDF
Other PeCDFs
123478 HxCDF
123678 HXCDF
234678 HXCDF
123789 HXCDF
Other HxCDFs
1234678 HpCDF
1234789 HpCDF
Other HpCDFs
Tetra- throuah Octa-CDDs and CDFs
(Results in
Median
63
ND (1.5)
ND (2.5)
ND (2.9)
ND (3.1)
ND (3.2)
ND (3.9)
11
37
35
698
233
547
6.2
4.7
14
ND (2.5)
ND (1.4)
ND (1.7)
ND (1.7)
5.2
6.6
ND (1.6)
12.7
ng/kg, or ppt)
No. of Detects
Ranae (9 samples)
ND (6.3) to 180
ND (1.1) to 837
ND (1.4) to 28
ND (1.6) to 1,280
ND (1.5) to 40
ND (1.7) to 95
ND (1.7) to 80
ND (3.1) to 2,180
18 to 490
18 to 447
263 to 1,780
13 to 1,150
37 to 2,310
ND (1.2) to 22
ND (0.9) to 38
ND (2.0) to 268
ND (0.9) to 31
ND (0.9) to 33
ND (0.9) to 34
ND (0.9) to ND (4.0)
ND (0.9) to 219
ND (3.6) to 70
ND (1.2) to 10
ND (1.2) to 63
8
2
1
2
1
1
1
8
9
9
9
9
9
6
6
5
2
1
1
0
7
7
1
8
OCDF
22
ND (54) to 168
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25
Table 13: Pulp and Paper Mill Wastewater Effluents
Tetra- throuh Octa-CDDs and CDFs
(Results in pg/kg, or ppq)
Median Range
No. of Detects
(9 samples)
2378-TCDD
Other TCDDs
12378 PeCDD
Other PeCDDs
123478 HxCDD
123678 HXCDD
123789 HxCDD
Other HxCDDs
1234678 HpCDD
Other HpCDDs
OCDD
42 ND (11) to 98
34 ND (3) to 138
ND (9.6) ND (2.8) to ND(25)
9.6 ND (9.6) to 130
ND (12) ND (6.6) to ND (12)
ND (12) ND (6.6) to ND (24)
ND (12) ND (6.6) to ND (23)
ND (17) ND (6.6) to ND 360
170 77 to 270
120 ND (27) to 160
3,000 1,000 to 4,600
8
7
0
5
0
0
0
4
9
8
2378-TCDF
Other TCDFs
12378 PeCDF
23478 PeCDF
Other PeCDFs
.23478 HxCDF
L23678 HxCDF
!34678 HxCDF
L23789 HxCDF
)ther HxCDFs
.234678 HpCDF
1234789 HpCDF
Other HpCDFs
120 12 to 840
270 43 to 1,460
ND (7.2) ND (2.2) to 36
ND (6.3) ND (2.2) to 33
21 ND (2.2) to 71
ND (8.4) ND (4.8) to ND (15)
ND (7.1) ND (4.8) to ND (15)
ND (8.2) ND (4.8) to ND (15)
ND (6.2) ND (2.5) to ND (15)
ND (15) ND (5.2) to 54
ND (23) ND (13) to 44
ND (22) ND (6.4) to ND (41)
36 ND (13) to 79
9
9
2
2
5
0
0
0
0
4
3
0
7
OCDF
190
ND (180) to 230
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26
Table 14: 2378-TCDD Toxic Equivalents
Nine Mill Sampling Program
(Results in ng/kg, or ppt)
EPA-TEF/87
I-TEFs/89
BLEACHED PULP
Median
Worst case
WASTEWATER SLUDGE
Median
Worst case
WASTEWATER EFFLUENT
Median
Worst case
ND=0
8.24
197.4
88.0
216.3
0.055
0.142
ND=DL
8.56
198.2
89.8
220.6
0.063
0.156
ND=0
8.28
198.4
90.1
218.5
0.059
0.147
ND=DL
8.83
199.4
93.1
223.8
0.073
0.177
Note: (1) "Worst case" represents the sample with the
highest levels of 2378-substituted CDDs and CDFs.
Table 15: 2378-TCDD Toxic Equivalents
Nine Mill Sampling Program
Percent of 2378-TEC Attributable to 2378-TCDD/TCDF
BLEACHED PULP
Median
Worst case
WASTEWATER SLUDGE
Median
Worst case
WASTEWATER EFFLUENT
Median
Worst case
Note:
(Results in percent, %)
EPA-TEF/87
ND=0
ND=DL
ND=0
I-TEFs/89
ND=DL
99.5
99.1
98.1
98.4
98.4
98.6
95.8
98.7
96.1
96.4
86.0
89.7
99.0
98.6
95.8
97.4
91.7
95.1
92.8
98.1
92.7
95.1
72.7
79.0
(1) "Worst case" represents the sample with the
highest levels of 2378-substituted CDDs and CDFs.
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27
REFERENCES
1. Amendola, G., et. al., The Occurrence and Fate of PCDDs and
PCDFs in Five Bleached Kraft Pulp and Paper Mills.
Chemosphere, Vol. 18, Nos. 1-6, pp 1181-1188, 1989.
2. U.S. EPA Cooperative Dioxin Screening Study. U.S. EPA, Office
of Water Regulations and Standards, Washington, D.C., March
1988, EPA-440/1-88-025.
3. U.S. EPA/Paper Industry Cooperative Dioxin Study, Washington,
D.C., April 26, 1988. (104 Mill Study Agreement)
4. USEPA/Paper Industry Cooperative Dioxin Study. "The 104 Mill
Study". Statistical Findings and Analyses. USEPA, Analysis and
Evaluation Division, Washington, D.C., June, 1990.
5. USEPA/Paper Industry Cooperative Dioxin Study; The 104 Mill
Study. Technical Bulletin No. 590. National Council of the
Paper Industry for Air and Stream Improvement, Inc., New York,
New York, May 1990.
6. Whittemore, R.C., et. al., U.S. EPA/Paper Industry Cooperative
Dioxin Study; The 104 Mill Study, presented at Dioxin '89,
Toronto, Ontario, September, 1989. (accepted for publication
in Chemosphere)
7. Summary of Technologies for the Control and Reduction of
Chlorinated Organics from the Bleached Chemical Pulping
Subcateaories of the Pulp and Paper Industry. U.S. EPA, Office
of Water Regulations and Standards and Office of Water
Enforcement and Permits, Washington, D.C., April 1990.
8. Interim Procedures for Estimating Risks Associated with
Exposures to Mixtures of Chlorinated Dibenzo-p-Dioxins and -
Dibenzofurans (CDDs and CDFs) and 1989 Update. U.S. EPA, Risk
Assessment Forum, Washington, D.C., March 1989, EPA/625/3-
89/016.
9. Voss, R.H., et. al., Some New Insights in the Origins of
Dioxins Formed Purina Chemical Pulp Bleaching. Pulp and Paper
Canada, 89 (12).
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