Emission factors and importance of PCDD/Fs, PCBs, PCNs, PAHs and PM 10 from the domestic burning of coal and wood in the U.K.

Article abstract of DOI:10.1021/es048745i

This paper presents emission factors (EFs) derived for a range of persistent organic pollutants (POPs) when coal and wood were subject to controlled burning experiments, designed to simulate domestic burning for space heating. A wide range of POPs were emitted, with emissions from coal being higher than those from wood. Highest EFs were obtained for particulate matter, PM₁₀, (～ 10 g/kg fuel) and polycyclic aromatic hydrocarbons (～ 100 mg/ kg fuel for ΣPAHs). For chlorinated compounds, EFs were highest for polychlorinated biphenyls (PCBs), with polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) being less abundant. EFs were on the order of 1000 ng/kg fuel for ΣPCBs, 100s ng/ kg fuel for ΣPCNs and 100 ng/kg fuel for ΣPCDD/Fs. The study confirmed that mono- to trichlorinated dibenzofurans, Cl_1,2,3DFs, were strong indicators of low temperature combustion processes, such as the domestic burning of coal and wood. It is concluded that numerous PCB and PCN congeners are routinely formed during the combustion of solid fuels. However, their combined emissions from the domestic burning of coal and wood would contribute only a few percent to annual U.K. emission estimates. Emissions of PAHs and PM ₁₀ were major contributors to U.K. national emission inventories. Major emissions were found from the domestic burning for Cl_1,2,3DFs, while the contribution of PCDD/F-ΣTEQ to total U.K. emissions was minor.

Full text of DOI:10.1021/es048745i

Environ. Sci. Technol. 2005, 39, 1436-1447
hydrocarbons (PAHs), and the polychlorinated dibenzo-p-
Emission Factors and Importance of
PCDD/Fs, PCBs, PCNs, PAHs and
PM10 from the Domestic Burning of
Coal and Wood in the U.K.
dioxins and dibenzofurans (PCDD/Fs). Over the past decades,
major efforts have been made to reduce emissions of these
pollutants. The use of catalytic converters and the introduc-
tion of lead-free petrol has resulted in decreasing emissions
of PAHs and PCDD/Fs. For PCDD/Fs, abatement measures
have mostly focused on stationary sources, such as municipal
and medical solid waste incinerators, but also cement kilns
etc (e.g. refs 1-3). As a result of these abatement measures,
the relative importance of diffusive and/or numerous small-
scale sources to the national/regional patterns of emission
has increased in recent years. Reliable, quantitative estimates
of emissions from diffuse sources are notoriously difficult to
obtain. Source inventory estimates of PCB, PCDD/F and PAH
emissions to the U.K. atmosphere, for example, give only
crude figures for diffuse discharges with large uncertainties
attached.
R O B E R T G . M . L E E , † P E T E R C O L E M A N , ‡
J O A N N E L . J O N E S , †
K E V I N C . J O N E S , † A N D
R A I N E R L O H M A N N * , † , §
Department of Environmental Science, IENS, Lancaster
University, Lancaster LA1 4YQ, U.K., National Environmental
Technology Centre, AEA Technology plc, Harwell,
Didcot, Oxfordshire OX11 0QJ, U.K., and Research Center for
Ocean Margins (RCOM), University of Bremen,
One form of diffuse emission which has attracted attention
for PCDD/Fs and PAHs is the domestic burning of coal and
wood for residential heating. Recent published U.K. atmo-
sphere emissions inventories have estimated domestic
burning to contribute ca. 10% of the PCDD/F-ΣTEQ emis-
sions (2) and between ∼30 and 80% (4, 5) of the ΣPAH
emission annually. The quantities of these compounds
emitted by domestic burning are very uncertain, however,
because of the difficulties in measuring them directly, of
deriving emission factors (EFs), and the great variability in
fuel type/combustion conditions (e.g. ref 1).
P.O. Box 330440, D-28334 Bremen, Germany
This paper presents emission factors (EFs) derived for a
range of persistent organic pollutants (POPs) when coal and
wood were subject to controlled burning experiments,
designed to simulate domestic burning for space heating.
A wide range of POPs were emitted, with emissions
from coal being higher than those from wood. Highest
EFs were obtained for particulate matter, PM10, (∼ 10 g/kg
fuel) and polycyclic aromatic hydrocarbons (∼ 100 mg/
kg fuel for ΣPAHs). For chlorinated compounds, EFs were
highest for polychlorinated biphenyls (PCBs), with
polychlorinated naphthalenes (PCNs), dibenzo-p-dioxins
(PCDDs) and dibenzofurans (PCDFs) being less abundant.
EFs were on the order of 1000 ng/kg fuel for ΣPCBs, 100s ng/
kg fuel for ΣPCNs and 100 ng/kg fuel for ΣPCDD/Fs. The
study confirmed that mono- to trichlorinated dibenzofurans,
Cl1,2,3DFs, were strong indicators of low temperature
combustion processes, such as the domestic burning of
coal and wood. It is concluded that numerous PCB and PCN
congeners are routinely formed during the combustion
of solid fuels. However, their combined emissions from the
domestic burning of coal and wood would contribute
only a few percent to annual U.K. emission estimates.
Emissions of PAHs and PM10 were major contributors to
U.K. national emission inventories. Major emissions were
found from the domestic burning for Cl1,2,3DFs, while
the contribution of PCDD/F-ΣTEQ to total U.K. emissions
was minor.
Recently, careful analysis of ambient air concentrations
has shown that other POPs, such as polychlorinated biphenyls
(PCBs) and naphthalenes (PCNs) also have a pyrogenic origin
(e.g. ref 6). Indeed, numerous PCN congeners have been
identified in waste incinerator fly ash (7). Atmospheric PCB-
and PCN-concentrations are generally associated with their
past industrial production and use. To our knowledge there
are almost no published EFs for either of these groups, making
it difficult to estimate the importance of the domestic burning
of coal and wood for national emission inventories.
In winter 1998, we conducted a study to assess the role
of domestic burning of coal/wood on ambient levels of
PCDD/Fs, PCBs and PAHs in the U.K. during the winter (8).
Samples were taken concurrently at four sites in northern
England to assess the air quality with regards to PCDD/Fs,
PCBs and PAHs in urban and rural sites in winter. We
estimated that local sources in two villages, where gas was
not available for domestic heating, accounted for ∼ 25% of
the ΣTEQ and ∼ 75% of the ΣPAHs in the ambient air at those
sites during the winter sampling events (8, 9). The villages
were also characterized by a specific atmospheric pattern,
with a preponderance of the lower chlorinated PCDFs and
many PAHs. These were assumed to stem from the domestic
burning of coal and wood. For PCBs, in contrast, the villages
did not have a characteristic profile, while ambient con-
centrations were elevated compared to background con-
centrations at a semi-rural air monitoring field station. In
this study, we made direct measurements of EFs from the
burning of house coal and seasoned hardwood in an open
fire situation under carefully controlled test conditions for
PAHs, PCDD/Fs (i.e., Cl1-8DD-Fs and the 2,3,7,8-substitued
congeners), particulate matter (PM10), PCBs and PCNs.
Introduction
Various organic pollutants are released as unwanted byprod-
ucts during the incomplete combustion of fuels and waste
products. Most notable are the groups of polycyclic aromatic
* Corresponding author phone: (401)874-6612; fax: (401)874-6811;
e-mail: lohmann@gso.uri.edu. Present address and author address
for correspondence: Graduate School of Oceanography, University
of Rhode Island, Narragansett, RI 02882-1197.
† Lancaster University.
Material and Methods
Controlled Burning Experiments. Suitable fuels, represen-
tative of a bituminous housecoal and a seasoned hardwood
were chosen and burnt on an open fire operated as closely
‡ National Environmental Technology Centre, AEA Technology
plc.
§ University of Bremen.
9
1436 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 6, 2005
10.1021/es048745i CCC: $30.25
2005 American Chemical Society
Published on Web 01/29/2005

as practicable to the requirements of British Standard (BS)
BS3841:Part 1:1994 (10). The burning tests were carried out
during the periods April - May 2000 and December 2000.
EFs were determined for Cl1-8DD/Fs, the 2,3,7,8-substituted
Cl4-8DD/Fs, PCBs, PCNs, PAHs and PM10 particulates.
The following fuels were selected: A 0.4 t sample of a
pre-packed bituminous house coal that was considered to
be representative of good quality coal used in nonsmokeless
areas of the North Midlands and Yorkshire. Seasoned
hardwood (mainly beech) was selected to be fairly homo-
geneous in terms of both log size and shape and to be free
of excessive bark. Both fuels were mixed and dried at 30 °C
for 48 h in a fan-assisted air-drying oven and allowed to
equilibrate with the atmosphere for a further 24 h before
use. Representative samples were extracted during the re-
bagging process following air-drying. This was carried out
by forming a long heap or ‘strip’ of each fuel. In the case of
the house coal, 36 increments (each of 0.5 kg) were taken by
scoop from the length of the strip along both sides. The
increments were combined and the entire sample reduced
and divided in accordance with the requirements of BS1017
Part 1 to provide separate laboratory samples for moisture
determination and general analysis (10). In the case of the
hardwood logs, forty pieces were randomly selected from
the strip, and each one hand-drilled in three locations using
a low speed setting and an 8 mm drill-bit in order to produce
approximately 500 g wood dust.
Burning Facility and Procedures. Fuels were burnt in an
open fire test setting and chimney as described in BS3841:
Part 1: 1994 to burn the fuels reproducibly (10). BS3841:
Part 2 defines a method of determining the actual gravimetric
smoke release rate, relying on an extractive technique drawing
a metered sample of flue gases through a filter maintained
at 70 °C (11). The latter method was adapted to determine
the targeted pollutants. A prescribed volume of dry fuel was
ignited in a Fulham Mk.III grate with a standard volume of
fuel gas (Figure 1). The radiant output from the fire was
measured continuously throughout the test by a quadrant
cage radiometer. At a point in the initial burning cycle
determined by the radiant output falling back from its peak
value to 1.45 kW or 0.75 × peak value (whichever was smaller)
the fire was then carefully de-ashed and refuelled with a
prescribed volume of fuel, which had been weighed. Im-
mediately following this point, iso-kinetic sampling of flue-
gas commenced. The fire was allowed to burn through a
second and third radiation peak and on the radiant output
reducing to 1.45 kW, the test was terminated, and flue-gas
sampling stopped. A single test for gravimetric smoke was
deemed to be valid if the ignition time (to 1.15 kW output)
was less than 50 min, and if the second radiation peak value
lay within the range 1.8-2.3 kW. Replicate tests had to satisfy
these criteria plus the mean of their second peak radiant
output values ought to lie within the range 1.95-2.15 kW.
The test method described in BS3841: Part 1 is intended for
coal-based fuels (10). Wood burns on an open fire in a
completely different and relatively uncontrolled manner. To
achieve an overall test time consistent with that when burning
house coal, it was necessary to refuel the fire with wood
seven or eight times. From initial sighting tests it was decided
that an initial charge of 2.8-3.0 kg of dry wood followed by
refuel charges of 1.8-2.0 kg achieved a quick ignition time
(to 1.15 kW) and a second peak radiant output of > 1.8 kW
thus complying with the primary requirements of BS3841:
Part 1 (10).
FIGURE 1. Schematic of test flue sampling for organic pollutants
and PM10.
specified pollutants (and especially PM10 and trace metals)
collected over the entire test period, and these could end up
being discharged to atmosphere in a domestic situation. The
methods selected for the sampling of the components of
interest in the flue gas emissions were as follows: PCDD/Fs,
PCBs, PAHs, PCNs-based on European Norm (EN) EN1948-
1: 1996 (filter/condenser method); PM10 - based on US EPA
Method 201a/202 (12, 13). The filters used were Whatman
GF/C grade 90 mm circles. For the sampling and collection
of PCDDs, PCDFs and PCBs a set of resin traps were cleaned,
and filled with XAD-2 resin. The traps were spiked with 20
13
C -labeled PCDD/Fs, 17 corresponding to the 2, 3, 7,
12
8-substituted isomers, and 3 to the following isomers: 2,
8-Cl2DF; 2, 7/8-Cl2DD; 2, 3, 7-Cl3DD. In addition, the traps
were also spiked with 10 13C12-labeled PCBs (28, 52, 77, 101,
126, 138, 153, 180 and 209) to provide recovery information
for the PCB and PCN analysis. All samples were stored at
4 °C pending transportation to the University of Lancaster
for analysis. A field blank was run in an identical fashion to
the tests, except that the sample probe was left outside the
flue test section. For the sampling of PAHs, recovery
compounds were supplied by Harwell Scientifics and added
to the resin prior to sampling.
Analytical Procedures. PCDD/Fs, PCBs, PCNs. The
chlorinated analytes were cleaned-up and analyzed at
Lancaster University. The XAD-2 resin and filter were
extracted with toluene in a Soxhlet for 18 h, the extract was
reduced and ∼1 mL of nonane added, the toluene was
removed and ∼5 mL of hexane added to the remaining
nonane. The condensate and washings were back extracted
into hexane. The two extracts were combined and digested
Flue Gas Sampling. The flue gas extraction technique for
determination of smoke content relies upon the iso-kinetic
withdrawal of a portion of the total flue gases throughout the
second and third burn cycles. Sampling was maintained
during the de-ashing and re-fuelling periods because these
operations could contribute significantly to the amounts of
9
VOL. 39, NO. 6, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 1437

13
dodecane were added (12C12 PCB 30 and
C
PCB 141).
12
TABLE 1. Coal and Hardwood Properties on a Dry Weight
Basis
Quantification of PCDD/Fs, PCBs and coplanar PCBs was
carried out on a Micromass Autospec Ultima high-resolution
mass spectrometer operated at a resolution of at least 10,000.
Details of the GC columns used and peak identification
criteria for PCDD/Fs are given elsewhere (14). Peak iden-
tification criteria for the PCBs and PCNs were similar to those
in ref 14 and were based on retention times and ion ratios.
For coplanar PCB analysis a 30 m DB5-MS column was used
(0.25 mm i.d., 0.1 µm film thickness), for multi-ortho PCBs
analysis a 60 m DB5-MS column was used (0.25 mm i.d., 0.1
µm film thickness). PCN analysis was performed using a
Fisons MD800 GC-MS. Separation was carried out on a CP-
Sil8 (Chrompak/Varian, Palo Alto, CA) capillary column
(length 50 m, diameter 0.25 mm) using helium as the carrier
gas. The detector was operated in electron impact (EI) mode
with selected ion monitoring (SIM). Quantification of the
PCDD/F and PCBs was achieved by the isotope dilution
method using the peak areas of specific 13C12-labeled recovery
standards and have therefore been recovery corrected. PCN
quantification was performed using standards based on a
Halowax 1014 technical mixture, the PCN data was not
recovery corrected. Tables 2 to 4 contain lists of the
compounds quantified. In all cases blank values were
subtracted from the data and detection limits, based on the
integrated area under the expected peak width for that
compound, were applied. A mixture of 7 13C12-labeled PCBs
was added to a seventh, unused XAD-2 resin trap to provide
an analysis blank. An indication of the amount in the blanks
seasoned
housecoal hardwood
moisture content (after air-drying, %)
ash content (%)
2.2
3.3
10.8
1
82.5
volatile matter (%)
36.7
total sulfur (%)
chlorine (%)
gross calorific value (kJ/kg)
1.33
0.35
33,360
0.04
0.04
18,580
with concentrated H2SO4. The reduced extract was eluted
through a number of multi-sorbent cleanup columns using
100 mL of hexane. The columns consisted of alternate layers
of activated silica, basic silica and acid silica. The 100 mL of
hexane were reduced and placed on a GPC column, the first
16 mL of the 1:1 DCM:hexane eluent was discarded and the
next 30 mL collected. Separation of the multi-ortho PCBs,
coplanar PCBs (# 77, 126, 169) and PCDD/Fs respectively
was carried out on a column containing ICN Alumina 1B
(ICN Biomedicals GmbH). The following eluents and volumes
were used: Fraction A multi-ortho PCBs, 12 mL 7% DCM in
hexane; Fraction B coplanar PCBs, 6 mL toluene; Fraction
C PCDD/Fs, 30 mL 1:1 DCM:hexane. An injection standard
in nonane (37Cl4-2, 3, 7, 8-Cl4DD) was added to each of the
fractions. Samples for PCN analysis were extracted and
cleaned up in an identical manner except that fractions A
and B were combined and two injection standards in
TABLE 2. Emission Factors of PCDD/Fs from Coal and Hardwood (ng/kg fuel)
TEFa
meanb
housecoal
% blankb,c
mean
hardwood
% blankb,c
kg fuel
MJ
7.6-7.7
43-45
st.dev.d
2.0
13-16
34-42
st.dev.d
0.1
2,3,7,8-Cl4DF
1,2,3,7,8-Cl5DF
2,3,4,7,8-Cl5DF
1,2,3,4,7,8-Cl6DF
1,2,3,6,7,8-Cl6DF
1,2,3,7,8,9-Cl6DF
2,3,4,6,7,8-Cl6DF
1,2,3,4,6,7,8-Cl7DF
1,2,3,4,7,8,9-Cl7DF
Cl8DF
0.1
9.3
2.6
1.8
0.7
0.6
nd
0.5
1.3
0.3
1.4
0.5
0.4
0.2
0.3
nd
4.1
33
11000
4100
460
140
20
nd
1%
nd
9%
5%
nd
0.4
0.2
0.1
0.1
0.1
0.1
0.1
0.3
0.1
0.4
0.0
0.0
0.1
nd
nd
7%
nd
27%
19%
nd
0.05
0.5
0.4
0.1
0.4
0.0
0.1
0.2
0.0
0.1
0.1
0.0
0.1
0.1
0.1
0.8
0.2
1.2
0.0
0.1
0.0
0.2
nd
nd
0.1
0.1
0.0
0.2
nd
nd
0.01
0.01
1.0e-4
1
12%
nd
44%
nd
2,3,7,8-Cl4DD
1,2,3,7,8-Cl5DD
1,2,3,4,7,8-Cl6DD
1,2,3,6,7,8-Cl6DD
1,2,3,7,8,9-Cl6DD
1,2,3,4,6,7,8-Cl7DD
Cl8DD
nd
nd
1
nd
nd
0.1
nd
0.0
nd
0.1
nd
nd
0.1
nd
0.1
1.4
7.3
2100
250
28
0.0
0.9
5.7
210
65
11
17
0.4
0.2
0.3
4.2
20
nd
0.01
3.4
32
43%
16%
0%
0%
0%
0%
0%
3%
2%
3%
1%
0%
1%
5%
39%
31%
67%
39%
0%
1%
1%
1%
2%
10%
4%
1%
2%
1%
1%
8%
68%
49%
1.0e-4
Cl1DFs
6930
340
64
Cl2DFs
Cl3DFs
Cl4DFs
23
30
Cl5DFs
2.5
1.6
1.1
4.9
74
1.5
0.7
0.6
11
Cl6DFs
5.2
1.9
8.4
180
30
Cl7DFs
Cl1DDs
Cl2DDs
46
Cl3DDs
1.4
0.7
0.3
1.5
6.4
7400
51
5.9
4.3
1.2
1.1
2.7
2500
50
2.1
0.8
0.3
0.8
1.7
310
25
Cl4DDs
12
Cl5DDs
3.6
3.5
7.9
16000
230
3.0
Cl6DDs
Cl7DDs
Σ Cl1-8DD/Fs
Σ Cl4-8DD/Fs
Σ TEQa
0.6
0.2
0.0
a van den Berg et al. (16). b nd - not detected. c Amount in blank as % of amount in corresponding burning trial before back-ground correction.
d st.dev. - standard deviation (n ) 3).
9
1438 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 6, 2005

for each compound class has been given in Tables 2 to 5
under the heading % Blanks. This column expresses the
amount of an analyte found in the blank as a percentage of
the mean amount in the samples before the amount in the
blank has been subtracted.
Results and Discussion
Fuels. The fuel properties highlighted the different natures
of coal and wood. Coal had the higher gross calorific value
(33 kJ/kg vs 19 for wood), but less volatile matter (37% -
wood 83%). Coal had about 10 times more chlorine than
wood (0.35 vs 0.04% for wood). These values are within the
range typically found for wood (e.g. ref 15). For all EFs on
a per weight basis, the burning of coal exhibited much higher
emissions than the burning of wood (Tables 2-6). The
precision of three independent test runs for both fuels was
very satisfactory. Relative standard deviations were < 20%
for most PCDD/Fs, PCNs, PAHs and PM10. The determination
of EFs for PCBs was less reproducible, which was likely a
result of the occurrence of a greater number of PCB congeners
in the blanks and the lower concentrations of PCBs in the
samples.
PAHs. PAH analysis was carried out by Harwell Scientifics.
GFFs were spiked with 1000 ng each of D8-naphthalene, D8-
acenaphthylene, D10-acenaphthene, D10-pyrene, D12-benzo-
[b]fluoranthene and D14-dibenzo[ah]anthracene. GFFs and
XAD-2 traps and condensate/rinsings fractions were extracted
with dichloromethane (DCM). The extracts for each test were
combined and evaporated to below 10 mL volume, then made
up to 10 mL in a volumetric flask. An aliquot volume of 2 mL
was then taken for PAH analysis. After addition of a recovery
spike the aliquot was cleaned up by column chromatography,
and finally analyzed by GC/MSD (Hewlett-Packard 5970
instrument equipped with a 50 m DB5 0.2 µm film capillary
column operated in SIM) after addition of a syringe standard.
PM10. A proprietary stainless steel in-stack cyclone was
used as a classifier, separating PM10 from non-PM10 particles.
A Graseby Andersen 90 mm filter holder was located externally
to the duct and unheated, therefore maintained at ambient
temperature (or slightly higher, as dictated by the flue gas
temperature as it passed through the filter). This was clearly
not in compliance with US EPA Method 201a but was a
necessary expedient in view of the prevailing conditions (12).
Whatman GF/C 90 mm filters were used for collection of
PM10. The PM10 material collected on the filters and the
associated PM10 particles which deposited upstream of the
filter during the PM10 tests were recovered and weighed.
Blank levels were in general < 10% of PCDD/F, PAH and
PM10 emissions, with higher blank levels for the higher
chlorinated PCDDs, some PCB and PCN congeners. Mean
recoveries for all samples of the labeled 13C12 standards were
as follows: PCDD/Fs - 58-76% except for one hepta-furan
(52%); PCBs - 68-100% except congener 28 (42%); coplanar
PCBs - congener 77-55%; congener 126-28%; congener
169-38%; PCB recoveries for the PCN results - 64 to 123%,
except congener 28 (46%).
Representativeness of Fuels and Burning Practice. The
vast majority of households burning bituminous coal in the
U.K. do so on appliances which are similar in general design
to the Fulham Mk.III grate and which are set in openings
roughly similar in size to that used for the tests. Combustion
air to the undergrate is controlled by means of an adjustable
flap or damper and it is unlikely that in the normal course
of events the fire would be allowed to burn away with no
means of controlling the undergrate air supply and hence
the rate of burn. It follows that the concentrations of various
pollutants generated during the house coal tests could be
viewed as typical of those generated from a household
situation, from the equivalent mass of the same fuel charged
to an established fire.
Comparison with Published EFs. Cl1-8DD/Fs. To our
knowledge, this is the first study reporting all homologue
groups of PCDD/Fs in such samples (Table 2). The lower
chlorinated DFs dominated the overall emissions from both
coal and wood, with EFs decreasing with increasing chlorine
number for the PCDFs. EFs were highest for Cl1DFs (11,000
ng/kg coal - 2,100 ng/kg wood), followed by Cl2DFs (4,100-
250) and Cl3DFs (460-30). For both fuels, EFs of PCDDs were
highest for Cl2DDs, followed by OCDD and Cl3DDs.
For ΣCl4-8DD/Fs, emissions were 230 ng/kg coal and 50
ng/kg wood. Much higher EFs were determined by Chagger
et al. for coal (2700 ng/kg), even under good combustion
conditions (cited in ref 19), and by Broeker et al. for various
coals (60-1800 ng/kg (20)). The EFs for wood were com-
parable to results from Gullett et al. (15) for wood combustion
in fire stoves in the San Francisco Region (10-76 ng/kg wood),
but much lower than results reported by Gullett and Touati
(21) for forest fires (100 up to 7000 ng/kg wood) and by Broeker
et al. for beech wood (500-2400 ng/kg (20)).
PCBs. As a general trend, EFs decreased with increasing
degree of chlorination (Table 3), similar to the pattern
observed for the PCDFs (see above). However, Cl3Bs had
much lower EFs than Cl4Bs (900 vs 7200 ng/kg fuel for coal
and 76 vs 410 ng/kg fuel for wood, respectively). For the
higher chlorinated PCBs, EFs decreased with increasing
degree of chlorination. Major PCBs emitted from both coal
and wood were #49 and #41/64 (>3,000 ng/kg coal; >100
ng/kg wood). Other congeners showed lower EFs, by 1-2
orders of magnitude. EFs for coplanar PCBs #77, #126 and
#169 were also determined, and decreased from #77 (4 Cl)
to #169 (6 Cl). Data on PCB emissions from combustion is
scarce. Gullett et al. (15) determined EFs for PCBs in wood
fuels - their values exceed our measurements by about an
order of magnitude. We cannot explain the differences, which
probably reflect the inherent variability in different fuels,
procedures and analytical methods. Part of the discrepancy
might be that the measurements by Gullett et al. (15) may
indeed represent ‘worst-case’ scenarios with unusually dry
fuel and high burn rates (22).
Regarding the combustion of wood, the traditional inset
open fire is not the most suitable appliance on which to burn
wood, although there are a significant proportion of house-
holds possessing this type of fire on which wood is burned
either by itself, or perhaps more commonly, in admixture
with coal. The main influence on differences between the
patterns of pollutant emissions from the tests as carried out
compared with hardwood burned in a domestic situation on
the same appliance type will probably be the moisture
content. It is unlikely that seasoned hardwood prepared for
domestic consumption would ever be as low in moisture as
the wood used in the test work. Therefore, it is reasonable
to suggest that certainly PAH, PM10 and possibly PCDD/F,
etc. EFs derived from the tests on wood will be lower than
those which would be obtained from burning the quality of
seasoned hardwood normally charged to a householder’s
fire.
PCNs. A wide range of PCN congeners was detected in
the test runs (Table 4). Similar to the EFs for PCDFs and
PCBs, higher EFs were determined for the lower chlorinated
congeners. Cl3Ns and Cl4Ns showed highest EFs (around 300
and 50 ng/kg fuel for coal and wood, respectively) with much
lower EFs for the higher chlorinated congeners. PCN #24
dominated with an EF of 120 ng/kg (coal) and 32 ng/kg
(wood). EFs for PCNs (total 680 and 120 ng/kg for coal and
wood, respectively) were lower than those determined for
PCBs (8,900 and 600 ng/kg). We believe these are the first
published measurements of EFs for PCNs, so no comparison
is possible.
9
VOL. 39, NO. 6, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 1439

TABLE 3. Emission Factors of PCBs from Coal and Hardwood (ng/kg fuel)
TEFa
meanb
housecoal
% blankc
meanb
hardwood
% blankc
kg fuel
MJ
7.6-7.7
43-45
13-16
34-42
st.dev.d
st.dev.d
17/18
22
28/31
41/64
44
49
52
nd
240
660
3100
170
3400
120
97
18
8.3
61
110
16
96%
78%
68%
33%
137%
18%
60%
32%
24%
28%
30%
43%
43%
37%
47%
44%
48%
42%
48%
0%
14%
83%
48%
115%
40%
57%
53%
0%
150
340
1200
110
3900
65
20%
28%
1%
24%
9%
7.0
32
95
180
19
200
13
31%
21%
19%
14%
11%
33%
28%
27%
26%
29%
38%
24%
27%
0%
60/56
61/74
70
10
31
11
67
23
31
16
160
21
41
38
15
77
1.0e-4
1.0e-4
10
2.7
7.3
15
0.8
2.9
5.3
2.7
5.7
2.2
8.1
0.1
2.9
0.3
0.0
0.4
3.7
87/115
95
46
53
72
58
99
33
33
7.0
14
5.3
13
101/90
105
100
40
95
47
110
88
2.3
96
6.6
1.8
18
51
16
110
13
2.5
12
5.2
0.2
17
13
31
8.4
17
0.9
3.9
1.1
7.1
900
7200
490
230
87
110
2.5
120
5.7
1.0
16
114
5.0e-4
1.0e-4
1.0e-4
0.1
0.3
8.5
1.2
0.2
0.6
9.1
nd
118
123
126
4%
141
23%
34%
33%
23%
23%
28%
0%
149
49
151
14
153/132
156
97
18
6.3
0.3
0.1
3.3
0.2
0.0
0.3
0.9
5.0e-4
5.0e-4
13
0.9
0.2
4.4
0.4
0.1
1.2
2.8
nd
157
2.7
11
158
167
1.0e-5
0.01
5.6
0.1
13
8.6
20
5.3
10
0.5
2.6
0.5
2.6
490
5100
5200
210
56
21%
3%
52%
27%
56%
38%
491%
44%
38%
169
170/190
174
19%
23%
19%
26%
23%
25%
0%
180
183
1.6
3.6
nd
1.3
0.4
2.2
76
410
72
33
9.2
3.8
630
0.020
0.4
0.7
187
189
1.0e-4
194
0.4
0.1
1.1
39
250
250
26
15
3.4
0%
25%
29%
199
21%
19%
203
ΣCl3Bs
ΣCl4Bs
ΣCl5Bs
ΣCl6Bs
ΣCl7Bs
ΣCl8Bs
ΣPCBs
Σ TEQa
12
8800
0.20
5.5
6600
0.10
439
0.003
a van den Berg et al. (16). b nd - not detected. c Amount in blank as % of amount in corresponding burning trial before back-ground correction.
d st.dev. - standard deviation (n ) 3).
Helm and Bidleman (6) suggested that PCNs #44, #29,
#54, and the more toxic #66 and #67 could indicate combus-
tion sources, based on the comparison of air profiles from
suburban and industrial locations in Toronto, Canada. There
are disparities between the congeners quantified here and
in the Toronto study. We cannot comment on congeners 29,
44 and 54, for example. However, congeners 66/67 do have
elevated EFs relative to the other Cl6Ns and may therefore
be indicative of combustion. It should be kept in mind that
our study only focused on the burning of coal and wood. It
is assumed that in a major urban-industrial conurbation like
Toronto, many different emission and combustion sources
are present. Indeed it would be surprising if a ‘wood’ or ‘coal’-
based signal was dominant in a major city.
kg coal, 3 mg/kg wood) and decreased further with increasing
molecular weight (Table 5). These EFs were rather high
compared to those determined by Oanh et al. (23) and
Wenborn et al. (5) for coal: Oanh et al. (23) determined
EFs < 3 mg/kg for fluorene and higher molecular weight
PAHs, while Wenborn et al. (5) reported EFs of, in general
<7 mg/kg, with the exception of 16 mg/kg for fluorene. Similar
patterns and EFs were determined for the burning of
hardwood in fireplaces by McDonald et al. (24) with ca. 3-4
mg/kg for fluorene, pyrene, fluoranthene and anthracene,
while Wenborn et al. (5) reported 6-8 mg/kg for these PAHs.
The PM10 EFs were 40 and 8 g/kg for coal and wood,
respectively (see Table 6). The value for wood compares well
to that determined by Gullett et al. (15) for different woods
in a fireplace (3-17 g/kg) and the range of 1-28 g/kg shown
for woods burned in different appliances in the U.S. (25).
Oanh et al. (23) reported a range of 7-51 g/kg for wood and
coals burned in fuelstove systems typical for southeast Asia.
PAHs and PM10. EFs for PAHs were dominated by the
lighter weight phenanthrene, naphthalene and acenaph-
thylene (17-22 mg/kg coal, 6-8 mg/kg wood), followed by
fluorene, pyrene, fluoranthene and anthracene (ca. 15 mg/
9
1440 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 6, 2005

TABLE 4. Emission Factors of PCNs from Coal and Hardwood (ng/kg fuel)
IUPAC No.
REPa
mean
housecoal
% blankb,c
mean
hardwood
% blankb,c
kg fuel
MJ
8.1-8.3
49-52
st.dev.d
3.0
9.3
14
13-14
40-42
st.dev.d
2.8
5.6
1.7
1.5
4.6
0.0
0.6
3.8
0.6
8.0
1.6
0.8
1.6
2.2
3.9
0.4
0.4
0.3
0.4
0.0
0.2
0.3
0.3
0.8
0.1
0.0
0.5
0.1
0.0
0.0
0.4
0.2
0.0
15
19
40
120
43
nd
nd
7.2
32
nd
nd
nd
nd
24
15
nd
5.5
7.6
5.8
0.0
1.7
12
16
46
20
nd
17/25
23
86
20
15
19
0.6
5.4
1.9
2.0
10
8%
75%
22%
16%
21%
6%
12%
2%
10%
54%
48%
21%
16%
14%
18%
19%
nd
60%
321%
28%
42%
42%
20%
27%
10%
27%
132%
94%
33%
73%
41%
34%
751%
nd
42
33/34/37
47
36/35
28/29/43
27/30
35
38/40
46
5.2
45
16
2.7
16
79
29
6.9
1.5
5.9
1.7
4.4
1.0
0.4
0.4
0.4
0.0
0.2
0.4
0.5
0.8
0.4
0.0
0.6
1.1
0.0
0.0
0.4
0.1
0.0
58
21
2.2
8.1
22
29
31
24
11
52/60
58
5.5
1.1
3.3
4.8
1.4
3.2
3.8
3.1
6.3
4.7
1.2
1.1
1.1
0.0
0.0
1.0
1.2
5.4
360
280
32
0.2
0.2
1.2
2.4
0.2
1.5
0.5
0.6
1.5
0.7
0.4
1.0
0.6
0.0
0.0
0.3
0.2
3.6
44
61
50
51
57
62
nd
nd
53
nd
nd
59
nd
nd
66/67
64/68
69
1.3e-3
7.5e-5
2.0e-3
nd
nd
nd
nd
nd
nd
71/72
63
nd
nd
nd
nd
65
nd
nd
73
1.0e-3
11%
nd
9%
74
nd
75
nd
nd
ΣCl3Ns
ΣCl4Ns
ΣCl5Ns
ΣCl6Ns
ΣCl7Ns
Cl8N
ΣCl3-8Ns
ΣREP-TEQa
52
52
15
5.5
2.1
0.5
3.6
89
4.1
2.1
0.5
nd
0.7
0.7
0.6
8.1
2.1
5.4
680
0.009
120
0.002
25
0.002
0.003
a Relative potencies from Blankenship et al. (17); for 66/67 and 64/68 a 50:50 mix was assumed; REP for 69 as cited in Blankenship et al. (17).
b Amount in blank as % of amount in corresponding burning trial before back-ground correction. c nd - not detected. d st.dev. - standard deviation
(n ) 3).
In an earlier study, Wenborn et al. (5) reported 8 g/kg wood
and 10 g/kg coal.
observed by Gullett et al. (15), who determined the highest
EF for OCDF. Major contributors to the ΣTEQ in this study
were 2,3,4,7,8-Cl5DF and 2,3,7,8-Cl4DF for both coal and
wood.
PCB-TEQ. For PCBs, the ΣTEQ was 0.2 and 0.02 ng/kg
fuel for coal and wood burning, respectively. These ΣTEQs
were almost exclusively dominated by PCB 126 in both cases.
Gullett et al. (15) determined much lower ΣTEQs for the
emissions from oak, namely 0.0014 ng ΣTEQ/kg fuel.
However, in their study PCB 126 was not detected, possibly
explaining the discrepancy between the results.
PCN-TEQ. There are no consensus TEFs for PCNs yet
agreed. For PCNs, the main toxic mechanism is their ability
to bind to the Ah receptor. Relative potencies (REPs) derived
from individual experiments with in vitro assays have been
reported by Blankenship et al. (17) and Kannan et al. (26).
These were used to calculate ΣREP-TEQs for wood and coal
emissions (Table 4). ΣREP-TEQs for PCNs were 0.009 and
0.002 ng/kg fuel for coal and wood, respectively, or were
lower by about a factor of 10 relative to PCB-TEQs. Similar
ΣREP-TEQs were obtained using the induction TEFs by
Kannan et al. (26).
The PAH- and PM10-EFs reported here for the combustion
of hardwood were comparable to those determined in several
other studies. However, the EFs determined for coal were in
general much higher than literature values. Interestingly, the
EFs determined in this study were very reproducible (Table
5). Nevertheless, we caution against the unquestioned use
of the EFs determined here for PAHs and PM10 for coal.
Toxic Equivalents. PCDD/F-TEQ. Sum of toxic equiva-
lents (ΣTEQ) were calculated for PCDD/Fs and PCBs with
the WHO toxic equivalency factors (TEFs) for humans/mam-
mals as reported by van den Berg et al. (16). PCDD/F-TEQs
were 3.0 and 0.21 ng ΣTEQ/ng fuel for coal and wood,
respectively. These TEQs match almost exactly those de-
termined by Wenborn et al. (5) for coal (3.0) and wood (0.24)
in a similar study. These EFs were much lower than those
determined for coal (100-110 ng ΣTEQ/kg) by Chagger et al.
(cited in 19). For the different woods used by Gullett et al.
(15), EFs ranged from 0.25 (oak) to 2.4 (artificial logs) ng
ΣTEQ/kg fuel. In this study, highest EFs were determined for
2,3,7,8-TCDF and the highest chlorinated DDs. This was not
9
VOL. 39, NO. 6, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 1441

TABLE 5. Emission Factors for PAHs from Coal and Hardwood (mg/kg fuel)
IEFa
mean
housecoal
% blankb
mean
hardwood
% blankb
kg fuel
MJ
7.2-7.7
44-52
st.dev.c
5.20
1.90
0.24
2.10
2.30
0.95
1.10
1.10
1.10
0.41
0.38
0.51
1.50
1.00
0.71
0.06
0.38
0.39
0.48
0.04
0.03
1.05
1.01
0.15
0.26
0.07
0.30
0.03
0.53
0.01
0.09
0.03
0.02
25
15-16
36-41
st.dev.c
2.20
1.30
0.15
0.50
1.30
0.36
0.23
0.06
0.11
0.15
0.02
0.25
0.60
0.55
0.14
0.06
0.19
0.16
0.24
0.00
0.00
0.08
0.12
0.06
0.09
0.14
0.10
0.02
0.08
0.05
0.01
0.01
0.00
9
Naphthalene
1e-8
19
17
1.4%
0.1%
0.6%
0.2%
0.4%
0.3%
0.2%
0.1%
0.1%
0.3%
0.1%
0.2%
0.3%
0.3%
0.2%
0.4%
0.2%
0.4%
0.2%
0.2%
0.8%
0.2%
0.3%
0.4%
0.3%
0.2%
0.2%
0.0%
0.2%
0.0%
0.1%
0.1%
0.1%
8.2
6.6
0.6
2.8
6.8
1.7
1.0
0.3
0.4
0.7
0.1
1.1
3.5
3.2
0.2
0.3
0.8
0.7
1.0
0.0
0.0
0.3
0.4
0.2
0.4
0.6
0.4
0.1
0.3
0.1
0.04
0.02
0.01
43
1.6%
0.2%
2.2%
0.6%
0.7%
1.2%
1.2%
1.6%
0.9%
1.4%
2.4%
0.5%
0.6%
0.6%
3.9%
1.3%
1.1%
1.8%
0.6%
9.2%
9.1%
1.8%
1.7%
2.0%
2.6%
1.2%
0.9%
0.5%
2.0%
0.2%
0.7%
1.2%
5.8%
Acenaphthylene
Acenaphthene
4.9
15
Fluorene
Phenanthrene
21
Anthracene
14
2-Methyl phenanthrene
2-Methyl anthracene
1-Methyl anthracene
1-Methyl phenanthrene
9-Methyl anthracene
4.5-Methylene phenanthrene
Fluoranthene
12
12
10
7.9
2.7
7.6
14
1e-8
Pyrene
Retene
Benzo[c]phenanthrene
Benz[a]anthracene
Chrysene
15
9.8
2.0
10
1e-5
1e-4
7.0
5.9
2.2
0.1
5.1
4.1
2.3
6.9
8.0
4.5
1.3
7.8
1.9
1.2
0.7
0.5
250
4.4e-3
Cyclopenta[c,d]pyrene
Benzo[b]naph[2,1-d]thiophene
5-Methyl Chrysene
Benzo[b]fluoranthene
Benzo[j]fluoranthene
Benzo[k]fluoranthene
Benzo[e]pyrene
1e-3
Benzo[a]pyrene
1e-4
1e-4
Indeno[1,2,3-cd]pyrene
Dibenzo[ah,ac]anthracene
Benzo[g,h,i]perylene
Anthanthrene
1e-8
Dibenzo [a,e]pyrene
Dibenzo[a,i]pyrene
Dibenzo[a,h]pyrene
ΣPAHS
ΣInduction-TEQa
0.4e-3
a Geometric mean of the in vitro TCDD-Induction Equivalency Factors from Bosveld et al. (18). b Amount in blank as % of amount in corresponding
burning trial before back-ground correction. c st.dev. - standard deviation (n ) 3).
temperature range (27). It was suggested that the formation
of PCDDs proceeds generally via cyclization of halogenated
TABLE 6. Emission Factors of PM10 from Coal and Hardwood
basic molecules (i.e. chlorophenols); the formation of PCDFs
via the halogenation of aromatic intermediate and final
products (28). These reactions are obviously not limited to
chlorinated dioxins and furans. Under poor combustion
conditions, Wikstro¨m et al. (28) observed a clear shift of the
PCDD/F homologue group profile toward the lower chlo-
rinated PCDDs and PCDFs. These ‘sooting’ conditions had
a higher C:Cl ratio present in the flame (due to more soot).
This could be the reason for the observed preponderance of
the lowest chlorinated congeners for most chlorinated organic
pollutants in our burning trials. Similarly, Yasuhara et al.
(29) observed that lower chlorinated PCDFs dominated over
PCDDs in combustion products under low combustion
temperatures (∼ 600 °C). The same conditions also resulted
in elevated PCB concentrations. These studies support the
hypothesis that the formation of PCDFs and PCBs (and likely
PCNs) is enhanced during low-temperature oxygen-poor
combustions.
mean %
mean %
mean housecoal blank mean hardwood blank
kg fuel
MJ
(g/kg)
PM10
7.1-7.3
44-46
st.dev.a
3.9
14-16
32-41
st.dev.a
0.7
40
7.9
a st.dev. - standard deviation (n ) 3).
PAH-TEQ. In a similar study using in vitro assays for the
toxic action of PAHs, Bosveld et al. (18) determined and
summarized induction equivalency factors for a range of PAH,
these are included in Table 5. These induction ΣTEQs were
4400 and 410 ng/kg fuel for coal and wood, respectively and
hence much higher than any of the ΣTEQs calculated above.
In both cases, the main contributor to the induction ΣTEQ
was benzo[k]fluoranthene, with ca. 50% of the total. It should
be pointed out that PAHs are much more prone to degrada-
tion reactions than any of the other compound groups.
Formation of Chlorinated Congeners. A ‘worst-case
scenario’ for the formation of chlorinated aromatic com-
pounds from combustion systems would combine the
following features: i) poor gas-phase mixing; ii) low com-
bustion temperatures; iii) oxygen starving conditions; iv) high
particulate matter loading; v) particulate matter-bound
copper; vi) presence of HCl and/or chlorine; and vii)
significant gas-phase residence time in the 250-700 °C
The formation of PCDDs, especially Cl7-8DDs, on the other
hand, seems to depend more on the presence of chlorinated
phenols in the fuel and flame (e.g. ref 29). The observed
increase in EF for the highest chlorinated PCDDs could be
explained by this extra formation pathway, namely through
the condensation of chlorinated phenols.
Comparison of EFs for Chlorinated Compounds. The
same samples were analyzed for 4 different groups of
9
1442 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 6, 2005

FIGURE 2. Normalized Emission Factors for PCBs, PCNs, PCDFs and PCDDs from the domestic burning of (a) coal and (b) hardwood (ng/kg
fuel) (For PCBs and PCNs - average concentration for all congeners with same number of chlorines, for PCDDs and PCDFs - homologue
group concentration divided by its theroretical number of congeners).
chlorinated organic pollutants (i.e. PCDDs, PCDFs, PCBs and
PCNs). This enabled a comparison of the emissions for tri-
to octachlorinated congeners from coal and wood. To achieve
this (homologue groups were analyzed for PCDDs and PCDFs,
but selected congeners for PCBs and PCNs), EFs were
normalized to obtain a mean EF per congener for a given
number of chlorines and compound groups (Figure 2). The
same trends were apparent for congeners with three to five
chlorines for coal and wood - EF for PCBs > PCNs >
PCDFs > PCDDs. For the congeners with six chlorines,
PCBs > PCNs > PCDFs ∼ PCDDs, while PCDDs displayed
higher EFs than PCNs and PCDFs with seven chlorines. For
the octa-chlorinated compounds, PCDD > PCBs ∼ PCNs ∼
PCDF.
The EFs for PCDD/Fs suggest that congeners with one or
two chlorines were the most abundant (The low EF for Cl1DDs
could be a result of the analytical method used here).
Decreasing EFs with increasing degree of chlorination were
also seen for the PCBs, although Cl3Bs had lower EFs than
Cl4Bs. However, the variation within a given homologue group
was large for the PCBs. For PCNs, EFs decreased from Cl3Ns
to Cl7Ns, with an apparent increase for Cl8N (Figure 3). The
variability within a given degree of chlorination was much
smaller than for PCBs. These results suggest that for PCDFs
and PCNs, the magnitude of the EF depended mostly on the
total number of chlorines, and seemed independent of the
molecular conformation. The results for PCBs were noticeably
less reproducible for any given degree of chlorination. This
might be partially because PCBs were the only nonplanar
molecules considered here. In summary, it is suggested that
domestic burning releases (i) mostly lower chlorinated
congeners and of those (ii) more PCBs than PCNs, PCDDs
or PCDFs. However, these emissions seem more important
for PCDD/Fs but less important for PCBs and PCNs in the
context of the U.K.’s national emission inventory (see below).
Influence of Chlorine Content on Formation of PCDD/
Fs, PCBs and PCNs. This study was not designed to elucidate
the role of chlorine content on the amount of chlorinated
compounds formed during the burning trials. However,
within the limited scope of two different samples, the
following observations can be drawn. The chlorine content
of coal was ∼ 9 times that of wood (Table 1), while emissions
of non-chlorinated PAHs were higher by a factor of 4-6 (see
later) for coal. The following ratios (coal:wood) were deter-
mined for the emissions of the different chlorinated com-
pounds: 14 for PCBs, 6 for PCNs, 7 for PCDFs, 4 for PCDDs.
Formation of Chlorinated PAHs. The simultaneous
determination of PAHs and the chlorinated compounds
enables a comparison of the emissions of the chlorinated
versus the ‘native’ PAHs.
9
VOL. 39, NO. 6, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 1443

FIGURE 3. Comparison of homologue group profiles in ambient air at Lancaster and emission profiles from coal and wood for (a) PCDFs
and (b) PCDDs.
Naphthalenes. A minute fraction of naphthalene (EF 10-
20 mg/kg) was detected as ΣPCNs (100-700 ng/kg).
Biphenyls. In a study by MacDonald et al. (24), EFs of
biphenyl were comparable to that of fluorene for different
woods burned. In our case, this would result in EF for biphenyl
of ∼ 3 mg/kg fuel, with ΣPCBs being detected at 600-9000
ng/kg fuel. These results suggest that a multitude of
chlorinated PAHs was formed in the burning trials (of which
we only analyzed PCNs and PCBs), but that the purely
chlorinated compounds only account for ppms of the parent
PAHs.
analyzed in the same laboratory under similar conditions.
For PCDDs and PCDFs, ambient concentrations from
Lohmann et al. (30) were chosen, in which 37 air samples
were analyzed for Cl2-8DD/Fs, representing the autumn/
winter of 1997. The mean ambient air profile of PCDFs was
dominated by Cl2DFs (> 95%), with minor contributions by
the other homologue groups (Figure 3). Cl2DFs were also the
main homologue group in the EFs for wood and coal (>
80%). However, Cl3DFs and Cl4DFs contributed ca. 10% each
to the EFs, a profile that is not mirrored in the ambient air
profile.
Comparison with Ambient Air Profiles. EFs are used in
emission estimates to calculate emissions from well-studied
processes, such as the domestic burning of coal and wood.
This study was designed to assess the impact of domestic
burning on ambient concentrations of these different organic
pollutants. Ambient air profiles of PCDDs, PCDFs, PCBs and
PCNs can therefore usefully be compared to those obtained
in the controlled burning trials. For the purpose of these
comparisons, ambient air measurements from Hazelrigg,
Lancaster University’s field station were chosen. These
measurements can be considered representative of semi-
rural northern England, an area where domestic burning of
coal and wood is still widely practiced in the winter months.
Furthermore, the fuels were selected to represent coal and
wood typically used in northern English households. As an
added advantage, ambient air samples and the EFs were
While the profile for PCDFs was relatively close for ambient
air and EFs, a much greater contrast was evident for PCDDs.
The EFs were dominated by Cl2DDs (> 65%), with 10%
contributions of Cl3DDs and OCDD (Figure 3). However, the
mean ambient air profile was dominated by the highest
chlorinated congeners: OCDD (> 40%), Cl7DDs (> 15%) and
Cl6DDs (> 10%). These comparisons suggest that the
domestic burning of coal and wood did not dominate the
ambient air profiles of PCDDs and PCDFs during the
measurement campaign.
For PCBs, the mean results of a long-term study by Lee
and Jones (31) were chosen. The ambient air profile for PCBs
was dominated by Cl3Bs (∼ 40%) with decreasing contribu-
tions with increasing degree of chlorination for the other
PCBs (Figure 4). The EF profile, on the other hand, was
dominated by the Cl4Bs (70-80%). Again, this suggests that
9
1444 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 6, 2005

FIGURE 4. Comparison of homologue group profiles in ambient air at Lancaster and emission profiles from coal and wood for (a) PCBs
and (b) PCNs.
FIGURE 5. Comparison of compound profiles in ambient air at Lancaster and emission profiles from coal and wood for PAHs.
any emission-derived PCBs were not strongly influencing
ambient air concentration at the site.
For PCNs, ambient air concentrations by Lee et al. (32)
were chosen (Figure 4). In this case there is a remarkable
similarity between the ambient air profile and those from
the EF. Major contributors were Cl3Ns and Cl4Ns in all cases.
This similarity does not necessarily imply that the ambient
PCNs were combustion-derived, though. It could also be the
result of similar product distributions obtained during the
industrial formulation of PCNs and burning emissions.
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VOL. 39, NO. 6, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 1445

TABLE 7. Estimated Inputs from the Domestic Burning of Coal and Wood to the U.K. Atmosphere and Potential Contribution to
the National Inventory
Est total emissions
U.K. NAEIc
for 1998
% due to
domestic burning
other
estimates
coal
wood
amount (t/a)
ΣPAHs (t/a)a
BaP (t/a)a
ΣPCBs (kg/a)
ΣCl4-8DD/Fs (g/a)
ΣTEQ (g/a)b
ΣPCNs (kg/a)
PM10 (kt/a)
2.40E+06
420
3.7
7.21E+05
31
2685
13
2840
40100
401
284
210
17%
36%
0.1%
1%
90% (5)
12% (2)
0.9
21
0.5
555
7.2
1.6
25
36
0.1
2%
0.09
5.7
1%
15%
a EF for coal and PM10 from ref 5. b van den Berg et al., ref 16. c Ref 33.
For PAHs, the mean results of a long-term study by Lee
and Jones (31) were chosen for comparison (Figure 5).
Ambient profiles were dominated by phenanthrene (> 45%)
and fluorene (> 20%). The EF profile for wood was similarly
dominated by phenanthrene (35%). The EF profile for coal,
on the other hand, had fairly similar contributions of fluorene,
phenanthrene, anthracene and pyrene (Figure 5). This
comparison indicated a potential for a sizable contribution
of wood burning emission on the ambient air profile in
Lancaster, but not for coal burning. It should be stressed
that both the emission profile and the EF apply only to the
burning of pure materials. It has been shown that the addition
of household waste results in increased EFs of chlorinated
compounds such as PCDD/Fs (e.g. refs 20 and 33).
National Importance of Domestic Burning. Table 7 uses
the EFs measured in this study to calculate the national
emissions from domestic coal and wood burning, assuming
they are representative for the country as a whole (only for
PAHs and PM10, EF for coal were used from Wenborn et al.
(5)). These emissions are based on national domestic coal
and wood consumptions of ca. 2.4 and 0.7 million tonnes
per year in the late 1990s, respectively. It should be noted,
however, that recent trends in the U.K. show a shift from
bituminous to smokeless fuel, which would likely result in
lower emissions. National atmospheric emissions inven-
tories (NAEI (34)) compiled for PAHs, PCBs and PCDD/Fs in
the U.K. are also shown in Table 7, and the potential
contributions of domestic coal/wood burning are highlighted.
As expected, their importance differs substantially between
compound groups.
PAHs, Benzo[a]pyrene (BaP), PM10. NAEI estimates
suggest emissions of 2,700 t/a for the 16 US-EPA PAHs (34).
Residential combustion accounts for ca. 500 t/a (∼ 20%),
which is close to our estimate (17%) in Table 7. For BaP
alone, the NAEI estimates annual emissions of 13 t, of which
ca. 30% were due to residential combustion (34), again in
good agreement with the estimates from this study of 36%
(Table 7). Estimates for emissions of PM10 derive ∼ 30 kt/a,
of which ca. 15% stem from the domestic burning of coal
and wood. The domestic burning of coal and wood is clearly
a major contributor to total PAH and PM10 emissions and the
biggest single emitter of BaP.
PCBs, PCNs. NAEI (34) estimated annual emissions for
PCBs on the order of 3,000 kg/a for 1997-8. The emissions
due to the domestic burning of coal and wood (ca. 21 and
0.5 kg/a, respectively) are minute in comparison. There are
no annual emission estimates available for PCNs. However,
a crude estimate can be obtained by scaling the annual
emission of PCBs to PCN using the ratio of their global
production (total PCN production of ∼ 150,000t, or ca. 10%
of total PCBs (35)). This would indicate annual emission for
the U.K. on the order of 300 kg/a. The emissions derived
from the domestic burning of coal and wood combined would
only add ∼ 2 kg/a. This calculation suggests that for these
industrially produced high volume chemicals, volatilisation
of the industrial formulations still dominates ambient air
concentrations.
PCDD/Fs, ΣTEQ. For PCDD/Fs-ΣTEQ, NAEI estimates
annual emissions of ∼ 400 g TEQ for 1998, of which ca. 20%
were from domestic burning (34). This is in-line with 52 g
TEQ from domestic burning of solid fuels, or ca. 16% (8%
-24%) of the emission inventory for 1996 as detailed by Alcock
et al. (2). However, use of the EF determined in this study
puts the total emission from the domestic burning of coal
and wood at ca. 7 g TEQ/a, or just 2% of total emissions.
Acknowledgments
We are grateful to the U.K. Department of the Environment,
Food and Rural Affairs for financial support. This is publica-
tion number 0241 from the Research Center for Ocean
Margins (RCOM).
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