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Candle composition is expected to influence the air pollutants emissions, possibly leading to important differences in the emissions of volatile organic compounds and polycyclic aromatic hydrocarbons. In this regard, the purity of the raw materials and additives used can play a key role. Consequently, in this work emission factors for some polycyclic aromatic hydrocarbons, aromatic species, short-chain aldehydes and particulate matter have been determined for container candles constituted by different paraffin waxes burning in a test chamber. It has been found that wax quality strongly influences the air pollutant emissions. These results could be used, at least at a first glance, to foresee the expected pollutant concentration in a given indoor environment with respect to health safety standards, while the test chamber used for performing the reported results could be useful to estimate the emission factors of any other candle in an easy-to-build standardised environment.
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Emissions of air pollutants from scented candles burning in a test chamber
Marco Derudi
, Simone Gelosa
, Andrea Sliepcevich
, Andrea Cattaneo
, Renato Rota
Domenico Cavallo
, Giuseppe Nano
Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica G. Natta, Via Mancinelli 7, 20131 Milano, Italy
Università degli Studi di Milano, Dipartimento di Medicina del Lavoro, Via San Barnaba 8, 20122 Milano, Italy
Università degli Studi dellInsubria, Dipartimento di Scienze Chimiche ed Ambientali, Via Lucini 3, 22100 Como, Italy
article info
Article history:
Received 18 January 2012
Received in revised form
4 March 2012
Accepted 9 March 2012
Scented candles
Emission factors
Test chamber
Volatile organic compounds
Burning of scented candles in indoor environment can release a large number of toxic chemicals.
However, in spite of the large market penetration of scented candles, very few works investigated their
organic pollutants emissions. This paper investigates volatile organic compounds emissions, with
particular reference to the priority indoor pollutants identied by the European Commission, from the
burning of scented candles in a laboratory-scale test chamber. It has been found that BTEX and PAHs
emission factors show large differences among different candles, possibly due to the raw parafnic
material used, while aldehydes emission factors seem more related to the presence of additives. This
clearly evidences the need for simple and cheap methodologies to measure the emission factors of
commercial candles in order to foresee the expected pollutant concentration in a given indoor envi-
ronment and compare it with health safety standards.
Ó2012 Elsevier Ltd. All rights reserved.
1. Introduction
Indoor air quality is affected by a number of indoor and outdoor
pollutants sources. However, while several information are avail-
able for outdoor pollutant sources in terms of emission factors
(Ravindra et al., 2008; Estrellan and Iino, 2010), only few infor-
mation have been published for indoor pollutant sources (Ott and
Siegmann, 2006; Sarigiannis et al., 2011), which include tobacco
smoke, as well as cooking, heating, and ofce equipments (e.g.,
Tuckett et al., 1998; Long et al., 200 0; Fan and Zhang, 2001;
Destaillats et al., 2008).
Burning of candles in indoor environments can release a large
number of toxic chemicals, including acetaldehyde, formaldehyde,
acrolein, and polycyclic aromatic hydrocarbons (Lau et al., 1997;
USEPA, 2001; Lee and Wang, 2006; Orecchio, 2011). It is believed
that regular burning of several candles in indoor environments can
expose people to harmful amounts of organic chemicals (USEPA,
Among the huge variety of candles available on the market,
scented candles have gained popularity over the past 30 years
resulting in the current abundance of candle shops and aroma-
therapy candle products. For the sake of example, U.S. retail sales of
candles are estimated at approximately $2 billion annually, being
by far the fragrance the most important characteristic impacting
candle purchases.
In spite of this large penetration of scented candles in indoor
environments, a few works investigating pollutants emissions from
candle burning (van Alphen,1999; Fine et al.,1999; Nriagu and Kim,
2000; Guo et al., 2000; Wasson et al., 2002; He et al., 2004; Zai
et al., 2006; Lee and Wang, 2006; Pagels et al., 2009)were
mainly focused on metals and soot emissions rather than on
organic pollutants, such as Volatile Organic Compounds (VOC) or
PAHs (Lau et al., 1997; Maupetit and Squinazi, 2009; Orecchio,
2011). However, candle composition is expected to determine the
pollutants emissions, possibly leading to important emissions of
VOC. Moreover, the priority indoor pollutants identied by the
European Commission (EU) mainly refer to VOC (Kotzias et al.,
Consequently, the aim of this work has been to characterize
pollutants emissions from the burning of scented candles using
a test chamber. In particular, emission factors for some polycyclic
aromatic hydrocarbons (PAHs), aromatic species (BTEX) and some
short chain aldehydes have been measured for different scented
candles. Among the others, formaldehyde, benzene and naphtha-
lene (which are classied by the EU as High priority chemicals)as
well as toluene and xylenes (which are classied by the EU as
Second priority chemicals) have been investigated. The obtained
results have been compared with the few data available in the
*Corresponding author. Tel.: þ39 0223993134; fax: þ39 0223993180.
E-mail address: (G. Nano).
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Atmospheric Environment 55 (2012) 257e262
literature in terms of emission factors, as well as with the emission
factors measured for raw parafn used to manufacture candles in
order to identify the contribution of added fragrances and dyes to
the pollutants emissions.
These results could be used to protect people health by
comparing the expected pollutant concentration in a given indoor
environment with health safety standards, while the test chamber
designed for performing the reported measurements could be
useful to perform further measurements in an easy-to-build stan-
dardized environment.
2. Materials and methods
2.1. Experimental setup
A crucial point in the determination of the pollutants emissions
from burning candles is the simulation of realistic burning condi-
tions. Different approaches have been proposed in the literature,
ranging from sampling ambient air close to a candle burning in
a real room (Orecchio, 2011), to sampling of the exhaust air from
a real-scale ventilated room (Maupetit and Squinazi, 2009) or from
a ventilated environmental chamber (Lee and Wang, 2006) where
the burning candle is located. These methods provide some pro and
some contra, the latter being mainly related tothe cost of a real-size
instrumented room or to the lack of reproducibility of a non-
controlled environment.
To overcome these problems, a laboratory-scale test chamber
has been designed to ensure well dened and reproducible
burning conditions as well as the possibility of sampling easily
the exhausts (Gelosa et al., 2007). The nal geometry, dened on
the basis of some preliminary Computational Fluid Dynamics
simulations and sketched in Fig. 1, creates a smooth air ow
around the candle an a large vortex above it, which mixes candle
fumes with the incoming air providing well-mixed conditions
and uniform concentration at the inlet of a long stack, from which
air is sampled far enough from the stack inlet to avoid entrance
As shown in Fig. 1, the test chamber consists of three parts: the
room itself is a cylinder (diameter 0.6 m, height 0.4 m) covered by
a conical cap (height 0.6 m) and a stack (internal diameter 0.07 m
and height 1.5 m). The cylindrical chamber is equipped with two
portholes to observe the candles behaviour during the tests.
The internal walls of the chamber have been blackened to
minimize radiation phenomena from the chamber walls to the
candle leading to uncontrolled rise of the candle temperature. The
test chamber has been equipped with an air sparger at the bottom
to supply air to the chamber environment with minimum turbu-
lence and very low velocity. Such an air sparger is constituted by
a perforated coil covered by a bed of small glass spheres. For all
experiments, pre-cleaned air through a charcoal trap has been
used. To verify the trap effectiveness,a blank measure on the air fed
to the chamber has been carried out before each test.
The air ow rate to the test chamber has been adjusted
to 10e15 NL min
to obtain realistic burning conditions with
a burning rate close to the values measured in some preliminary
burning tests in real rooms.
Four candles have been burned simultaneously for each test;
they have been placed upright at the centre of the chamber bottom,
spaced enough to avoid undesirable thermal inuence from one
candle to the others. The locations of the individual candles inside
the chamber have been recorded and kept equal for all the tests.
Burning four candles simultaneously allows for both increasing the
pollutant production rate and averaging the possible differences
among candles of the same kind, thus reducing the uncertainties in
the estimation of the pollutants emission factors.
To determine the candle burning rate, each candle has been
weighted before and after the burning experiment and the corre-
sponding burning time has been recorded.
Five different kinds of coloured (about 30 mg of dye) and
scented (about 2% by weight of fragrance) commercially available
candles with a cotton wick have been tested. The candles had an
approximate weight of 150 g without any container. More details
on such candles can be found elsewhere (Gelosa et al., 2007), where
some preliminary results were also discussed.
Moreover, candles made only from three different kinds of
commercially available parafns (which are used as raw materials
by candles makers) with a cotton wick have been investigated. They
had an approximate weight of 100 g and were contained in a glass
beaker. The results of these last experiments allow investigating the
contribution of fragrance and dye to the pollutants emissions. Main
features of the investigated candles are summarized in Table 1.
2.2. Analytical methods
At the beginning of each experimental run the candles were
burnt for about 15 min before to start the exhaust sampling. This
initial burning period was used to check that individual candles
reached proper burning conditions, without atypical burning
Fig. 1. Sketch of the test chamber. Arrows inside the chamber roughly represent air
Table 1
Main features of the investigated candles.
Sample Container Color Fragrance
A No Brown Cedarwood
B No Blue Plumeria
C No Navy blue Oriental spices
D No Red Rhubarb
E No Pale green Aloe vera
W1 Glass No No
W2 Glass No No
W3 Glass No No
M. Derudi et al. / Atmospheric Environment 55 (2012) 257e262258
behaviour, and to ensure that steady conditions are obtained within
the chamber; for this reason, an on-line measure of the residual
oxygen concentration within the stack was performed. Once
a steady oxygen concentration was obtained the sampling was
started. Then, exhaust gases were sampled and analysed to evaluate
the concentrations of PAHs, BTEX, as well as short chain aldehydes
such as formaldehyde, acetaldehyde, propionaldehyde and benz-
aldehyde. Considering both the initial transient phase and the
sampling period, the overall duration of each experiment was less
than 4.5 hours.
For the short chain aldehydes the DNPH (2,4-
dinitrophenylhydrazine) method was used (Sesana et al., 1991). By
means of a gas sampling pump a well dened volume of exhaust is
passed through a cartridge containing the DNPH sorbent (LpDNPH
S10 cartridge). The aldehydes react quantitatively with DNPH to the
corresponding hydrazone compounds which can be measured
through HPLC. According to the sampling capacity of the DNPH
cartridge, a sampling ow of about 1.5 L min
allows for collecting
a total volume of about 45 L in 30 min. The DNPH cartridge can be
desorbed using acetonitrile, and aldehydes analysed using HPLC
(C18 column, 5
m 250 mm, detector UV@360 nm). The extraction
yield of the aldehydes has been always close to 100% and the rela-
tive standard deviations on the corresponding measurements were
less than 5%. The detection limit for the various aldehydes has been
estimated equal to about 0.1
of candle burnt.
For measuring benzene, toluene, ethylbenzene and xylenes,
awelldened volume of exhaust gas was sampled by means of
a gas pump and passed through a charcoal cartridge (Carbotrap
349). According to the sampling capacity of the charcoal cartridge,
a sampling ow of about 0.05 L min
allows for collecting a total
volume of about 12 L in 4 h. After sampling, the charcoal cartridge
was thermally desorbed and analysed with gas chromatography e
mass spectroscopy (CG/MS) equipped with Restek Rxi-5Sil-MS
chromatographic column. The average extraction yields of the
BTEX ranged from 86% to 100% and the relative standard deviations
on the corresponding measurements were less than 10%. The
detection limit for the various BTEX has been estimated equal to
about 0.01
of candle burnt.
PAHs were sampled with a combined particle/gas phase system:
awelldened volume of exhaust gas was sampled by means of a gas
pump and passed through a PTFE lter (TE 35, pore size of 0.2
and an adsorption Tenax cartridge (Supelco XAD Orbo Tube).
Particles were collected on the PTFE lter surface, while gas phase
PAHs were sampled on the XAD2 sorbent. Both lter and cartridge
were extracted with dichloromethane coupled with a sonication
treatment of 30 min. According to the sampling capacity of both the
lter and the cartridge, a sampling ow of about 0.5 L min
for collecting a total volume of about 120 L in 4 h. After vacuum
concentration, the desorbed solution was analysed using gas
chromatography coupled with a mass-spectrometry (GC/MS).
Considering the measurements of all the samples, extraction yields
of the PAHs were never less than 85% and in most cases almost
100%, while the relative standard deviations on the corresponding
measurements were less than 15%. The detection limit for the
Fig. 2. Aldehydes emission factors for the investigated scented candles (lled bars) and pure parafn candles (empty bars). Dashed line represents the quantication limit.
Fig. 3. BTEX emission factors for the investigated scented candles (lled bars) and pure parafn candles (empty bars). Dashed line represents the quantication limit.
M. Derudi et al. / Atmospheric Environment 55 (2012) 257e262 259
various PAHs has been estimated equal to about 0.01 ng g
candle burnt.
Sampling was always stopped before the blowout of the candles
so as to avoid the collection of pollutants produced during the last
transient stage of the burning process.
3. Results and discussion
As previously mentioned, four scented candles have been
burned in the test chamber for each test, leading to an average
candle burning rate of about 4.5 g h
for all the investigated
Apart from the beginning of the test, when a calm ame
gradually formed a cup rim surrounding the so-called burn bowl,
the ame burned without visible release of smoke and the candles
did not drip. In particular, scented candles have been burnt in
a single step, but to verify if the emissions were constantly
released few experiments have been also carried out in different
burning cycles of about 4 hours, followed by a 1 hour stop
between the cycles. No signicant differences were found for the
two procedures.
Measured emissions have been calculated as emission factors
with reference to 1 g of candle burnt. These values allow a direct
comparison between different types of candles; as shown in
Figs. 2e4, emission factors can change signicantly from one candle
type to another one: variation as large as one order of magnitude
have been recorded for individual pollutants.
The measured emission factors show that large differences can
be found also in similar candles; moreover, no clear correlations can
be deduced from these data, because one candle can show large
emission factor for one pollutant and small emission factor for
another one. Moreover, we can see that large emissions of BTEX are
not necessarily related to high levels of PAHs, and even within the
BTEX no clear relations exist. One candle clearly show lower levels
of BTEX and PAHs, while evidencing emission factors for aldehydes
similar to the other candles. The other candles evidenced that more
than 34% of the emitted BTEX is constituted by ethylbenzene while
xylenes formation is negligible.
For what concerns PAHs, two scented candles show emission
factors close to the detection limit of the analytical procedures,
while the other ones show not negligible emission factors (Fig. 4).
Most of the PAHs detected are constituted by 2- to 4-ring PAHs; in
particular, naphthalene (2-ring PAH), phenanthrene (3-ring PAH),
uoranthene and pyrene (4-ring PAHs), which are known as
precursors of particulate matter, evidenced average emission
factors above the detection limit.
Finally, aldehydes emissions are quite similar for all the candles,
as expected if such emissions would be mainly related to the
presence of a fragrance rather than to the other candle parameters.
In particular, formaldehyde shows always the highest emission
factors, followed generally by acetaldehyde; on the other hand,
other short chain aldehydes do not show a clear behaviour,
evidencing several individual emission factors below the detection
limit (Fig. 2).
This has been conrmed by the experiments carried out using
candles made by pure parafn and enclosed in a glass beaker,
whose results are also summarized in Figs. 2e4. These candles
showed an average burning rate lower than the previous one and
equal to about 2.5 g h
, as expected due to the presence of the
glass container that hinders the air ow towards the ame.
The results summarized in Fig. 2 clearly show that burning pure
parafn candles does not produce any detectable amount of alde-
hydes, whose production in the commercial candles investigated
should be consequently ascribed to the presence of additives.
Moreover, a data scattering among the three parafns investi-
gated even larger than that found for the scented candles is evident
for BTEX and PAHs emission factors. Differences as large as two
orders of magnitude can be seen from Figs. 3 and 4, especially for
2e3 ring PAHs. This seems to indicate that the kind of raw material
rather than the additives determines BTEX and PAHs emissions.
Studying the distribution of different PAHs isomers into the
exhausts it is possible to hypothesize if they are released by evap-
oration and pyrolysis phenomena at relatively low temperature,
due to the overheating of the candles constituents, or produced by
an incomplete combustion (Yunker et al., 2002; Orecchio, 2010).
Usually, values of anthracene to anthracene plus phenanthrene
Fig. 4. PAHs emission factors for the investigated scented candles (lled bars) and pure parafn candles (empty bars). Dashed line represents the quantication limit.
Table 2
Isomeric ratios for the investigated candles (legend as in Table 1).
Isomeric ratios Scented samples Waxes Mean scented Mean waxes
Ant/(Ant þPhe) 0.19 0.33 0.07 0.27 0.25 0.95 0.63 0.83 0.22 0.80
Fla/(Fla þPyr) 0.50 0.50 0.40 0.43 0.60 0.09 0.20 0.11 0.49 0.13
B[a]A/(B[a]A þChr) 0.76 0.67 0.50 0.01 0.50 0.50 0.50 0.50 0.49 0.50
Total index 6.96 7.92 4.18 3.86 6.50 12.19 9.25 11.11 5.89 10.85
M. Derudi et al. / Atmospheric Environment 55 (2012) 257e262260
Ant/(Ant þPhe) ratio <0.10 are an index of low temperature
sources while values larger than 0.10 indicates a dominance of
combustion (Yunker et al., 2002). As reported in Table 2, most of the
investigated samples evidenced high values of this index; consid-
ering the average values, Ant/(Ant þPhe) is equal to 0.22
for scented candles and to 0.8 for the scentless ones. Concerning
Fla/(Fla þPyr) and B[a]A/(B[a]A þChr) ratios, values of 0.4 and 0.2
respectively can be assumed as common threshold between low
temperature sources and intermediate conditions or combustion
sources (liquid and solid fossil fuels). For the samples analysed in
this paper, scented candles exhibited average values equal to 0.49
for both the isomeric ratios conrming that PAHs are mainly
emitted by combustion, while the parafnic waxes evidenced
discordant average values of Fla/(Fla þPyr) <0.4 and B[a]A/(B[a]
AþChr) >0.2. To overcome this problem, as suggested by Orecchio
(2010), a total index, dened as the sum of the above mentioned
isomeric ratios, normalized to the limit values reported in literature
(Yunker et al., 2002), has been evaluated as:
Total index ¼Ant
ðAnt þPheÞ$0:1þFla
ðFla þPyrÞ$0:4
When the total index is >4, PAHs are mainly originated from
high temperature processes (combustion) while lower values
indicate prevalently low temperature emissions. In this study, the
average total index is equal to 5.89 for scented candles and 10.85 for
parafns, thus conrming that PAHs are emitted by high temper-
ature processes.
Finally, the scented candles results have been compared with
the few data concerning scented candles available in the literature
(Maupetit and Squinazi, 2009; Orecchio, 2011), as summarized in
Table 3. We can see that most of the emission factors reported in
Figs. 2e4lie inside the ranges measured in these previous works.
However, we can also see that such ranges are quite wide,
therefore conrming that emission factors can change signicantly
from one candle type to another one without any self-explaining
reason. This clearly evidences the need for simple and cheap
methodologies to measure the emission factors of commercial
candles in order to foresee their health hazard level, possibly before
they can reach the market.
Emissions of few high priority pollutants have been then
compared to the corresponding ambient air quality standards; on
the basis of the determined emission rates of the candles, a simple
indoor air scenario was used to determine resulting indoor air
levels when four scented candles are burnt simultaneously in
room, considering an air exchange rate of 0.5 h
. In a well-
mixed environment, the steady-state concentration for the i-th
pollutant (C
) has been computed as follows:
V$AER (2)
with n¼number of candles, m¼candle burnig rate, EF
factor of the i-th pollutant, V¼room volume, and AER ¼air
exchange rate.
The resulting indoor air concentrations, computed for the
maximum emission factors found for formaldehyde, benzene and
benzo[a]pyrene, respectively, are summarized in Table 4, together
with the corresponding air quality standards. It can be seen that
formaldehyde and benzene concentrations are well below the
standards considered, while the concentration of benzo[a]pyrene is
about 40% of the recommended value; obviously a much more
detailed toxicological study should be performed to critically
evaluate the obtained data.
4. Conclusions
The main aim of this work has been to characterize pollutants
emission factors, with particular regard to VOC identied by the EU
as priority indoor pollutants, from the burning of scented candles.
All the experiments have been carried out using a laboratory-
scale test chamber, which allows for performing these measure-
ments in a controlled environment avoiding the large investments
required by a full-scale environmental room.
It has been found that the BTEX and PAHs emission factors show
large differences in similar candles without any clear correlations.
On the other hand, aldehydes emission factors are quite similar for
all the candles, leading to the conclusion that such emissions are
mainly related to the presence of a fragrance rather than to the
other candle parameters. This has been conrmed by the experi-
ments carried out using candles made by pure parafn, where
almost no emissions of aldehydes have been found. Moreover,
a data scattering among the three parafns investigated even larger
than that found for the scented candles is evident for BTEX and
PAHs emission factors. This seems to indicate that the kind of raw
material rather than the additives determines BTEX and PAHs
A comparison with the few data concerning scented candles
available in the literature conrmed that the emission factors of the
scented candles lie inside the ranges measured in these previous
works, which are indeed quite wide.
This clearly evidences the need for simple and cheap method-
ologies to measure the emission factors of commercial candles in
order to foresee the expected pollutant concentration in a given
indoor environment and compare it with health safety standards.
In this regard, the laboratory-scale test chamber realized in this
study could be useful to perform measurements in an easy-to-build
standardized environment.
Table 4
Airborne concentrations of pollutants estimated for the considered exposure
Pollutant Scented candles
(Max. value)
3.49 100 (World Health
Organization, 2010)
0.15 5 (EU, 2000)
Benzo(a)pyrene, ng m
0.41 1 (EU, 2004)
Table 3
Comparison among emission factors measured for different scented candles.
This work
(maximum value)
Maupetit and
Squinazi, 2009
Orecchio, 2011
2.91 7.09e141.30
1.12 1.77e8.48
0.55 0.00e11.30
0.13 <1
0.23 <1
0.04 <1
Naphthalene, ng g
0.04 <2800 0.48e15.00
Fluorene, ng g
0.04 0.06e4.70
Phenanthrene, ng g
0.14 0.05e3.00
Anthracene, ng g
0.02 <15
Fluoranthene, ng g
0.07 0.005e1.20
Pyrene, ng g
0.10 0.005e1.00
Chrysene, ng g
0.75 0.007e3.00
Benzo(a)anthracene, ng g
0.03 0.01e0.40
Benzo(a)pyrene, ng g
0.33 0.01e1.40
M. Derudi et al. / Atmospheric Environment 55 (2012) 257e262 261
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... (UFPs), 4-7 polycyclic aromatic hydrocarbons (PAHs), 8 and NO x . [9][10][11] Candle emissions have been associated with various adverse health effects in humans such as reduced cognitive abilities 12 and negative changes in lung function. 13 On the contrary, increased power of high-frequency spectral band of heart rate variability in healthy women has been reported after exposure to candle particles from stressed burn. ...
... NO x emissions from the steady burn of candles have previously been reported. 9,11 However, the influence of the wax and wick composition on the NO x emissions has not been investigated. We measured the particle and gas emissions from five types of pillar candles (120 mm in height and 58-60 mm in diameter) that had different wax and wick combinations (denoted as candles 1-5) during stressed burning conditions (Table 1). ...
... The similarity in NO x emissions is consistent with previous reported NO x emissions from the steady burn of candles. 9 ...
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Burning candles release a variety of pollutants to indoor air, some of which are of concern for human health. We studied emissions of particles and gases from the stressed burning of five types of pillar candles with different wax and wick compositions. The stressed burning was introduced by controlled fluctuating air velocities in a 21.6 m3 laboratory chamber. The aerosol physicochemical properties were measured both in well‐mixed chamber air and directly above the candle flame with online and offline techniques. All candles showed different emission profiles over time with high repeatability among replicates. The particle mass emissions from stressed burning for all candle types were dominated by soot (black carbon; BC). The wax and wick composition strongly influenced emissions of BC, PM2.5, and particle‐phase polycyclic aromatic hydrocarbons (PAHs), and to lower degree ultrafine particles, inorganic and organic carbon fraction of PM, but did not influence NOx, formaldehyde, and gas‐phase PAHs. Measurements directly above the flame showed empirical evidence of short‐lived strong emission peaks of soot particles. The results show the importance of including the entire burn time of candles in exposure assessments, as their emissions can vary strongly over time. Preventing stressed burning of candles can reduce exposure to pollutants in indoor air.
... Cultural Heritage is frequently under threat and the phenomenon associated to its deterioration is mainly ascribed to anthropogenic actions, environmental influence and/or microbial colonisation. Monuments are highly susceptible to deterioration, triggered by environmental and anthropogenic conditions, such as high concentration of airborne particles and volatile organic compounds originated from combustion of carbonaceous materials, like fossil fuel and candles [1,2]. Air pollution is a factor that intensifies the deterioration of historic buildings and it can be observed by the presence of black crusts in carbonate (e.g., gypsum crusts) or in granitic stones, inducing superficial detachments [3]. ...
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This article discloses a rare and outstanding type of Mn-rich black-blue patina found on mural painting and granite ashlars located in the church of Sta. Marinha, north of Portugal, and conjectures the phenomenon associated to the appearance of such patinas in different surface materials. This Mn-patina reported on mural painting and their origin is probably assigned to manganese leaching from building materials (i.e., granite and phyllites). Stained mural painting and granite examined by XPS and SEM have showed patinas enriched with manganese (IV) oxide, potentially catalysed by a microbiota, like fungi, observed in SEM micrographs. The pigments used to depict mural painting and groundwater were also analysed by micro-Raman and ICP-MS, respectively, indicating that they are unlikely manganese sources. Unstained building materials, such as granite ashlars, historic joints, mortars and phyllite rocks, were also analysed by ICP-MS showing that historic joints and mortars present significant concentrations of manganese, possibly associated to their absorbing feature. The main materials with potential to impart manganese to Mn-rich patinas are granite ashlars and phyllites. The aim of this investigation is to reveal and ascertain the hypothetical sources and the phenomenon responsible for the Mn-rich black-blue patina appearance, both on mural painting and granite ashlars.
... The spatial discrepancies in PAH concentrations in soils is related to the land use type, proximity to emission sources, nature of the land surface, and physicochemical characteristics of soils, whereas spatial differences in indoor dust are linked to the nature of the indoor setting and activities within the indoor environment including smoking, housekeeping habits, proximity to areas with high traffic density, and other anthropogenic activities, as well as the rate of inltration of outdoor dust into the indoor environment. 40,75,76 The spatial discrepancies in the PAH concentrations in outdoor dust are related to dust dispersion rate, pavement types, traffic volume, vehicular speed, frequency of street cleaning, and nature and height of buildings. 49,77 The target and intervention values set by the Nigerian regulation for PAHs in soil are 1000 and 40 000 mg kg À1 respectively, 78 which are similar to the Dutch target and intervention values of 1500 and 40 000 mg kg À1 respectively. ...
In this study, we evaluated the concentrations, composition, sources, and potential risks of polycyclic aromatic hydrocarbons (PAHs) in soils, and indoor and outdoor dust from Port Harcourt city in Nigeria. Gas chromatography-mass spectrometry (GC-MS) was used for the detection and quantification of PAH species in the samples. The concentrations of the US EPA 16 PAHs plus 2-methyl-naphthalene (∑17 PAHs) in soils, and indoor and outdoor dust from Port Harcourt city ranged from 240 to 38 400, 276 to 9130 and 44 to 13 200 μg kg-1 (dry weight, d.w.) respectively. The PAH concentrations in these matrices followed the sequence: soil > indoor dust > outdoor dust. The composition of PAHs in soils and dust (indoor and outdoor) showed remarkable differences with prominence of 3- and 5-ring PAHs. The estimated carcinogenic risk to the residents arising from exposure to these concentrations of PAHs in soils, and indoor and outdoor dust from Port Harcourt was above the acceptable target cancer risk value of 10-6. We concluded that these sites require clean-up, remedial actions and implementation of stringent pollution control measures with the intention of reducing the undesirable impacts of PAHs on both the ecosystem and humans.
... Because the toxic effect of PAH to bacterial DNA was recognized, detecting the recA gene is a more direct evidence to show the bacterial response from soot exposure. Although the amount of PAH and other pollutants in the soot from the paraffin-type candles can widely vary (Derudi et al. 2014), the evaluation step requires further consideration of a soot property analysis. A detailed evaluation of genetic-level response to soot exposure is beyond the scope of this investigation; however, it is a direct way to assess the effect of soot on bioaerosol. ...
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Atmospheric pollutants are hypothesized to enhance the viability of airborne microbes by preventing them from degradation processes, thereby enhancing their atmospheric survival. In this study, Mycobacterium smegmatis is used as a model airborne bacteria, and different amounts of soot particles are employed as model air pollutants. The toxic effects of soot on aerosolized M. smegmatis are first evaluated and excluded by introducing them separately into a chamber, being sampled on a filter, and then cultured and counted. Secondly, the bacteria–soot mixture is exposed to UV with different durations and then cultured for bacterial viability evaluations. The results show that under UV exposure, the survival rates of the low-, medium-, and high-soot groups are 1.1 (±0.8) %, 70.9 (±4.3) %, and 61.0 (±17.6) %, respectively. This evidence significantly enhanced survival rates by soot at all UV exposures, though the combinations of UV exposure and soot amounts revealed a changing pattern of survival rates. The possible influence by direct and indirect effects of UV-damaging mechanisms is proposed. This study indicates the soot-induced survival rate enhancements of M. smegmatis under UV stress conditions, representing the possible relations between air pollution and the extended pathogenic viability and, therefore, increased airborne infection probability.
One of the more important classes of potentially toxic indoor air chemicals are the Volatile Organic Compounds (VOCs). However, due to a limited understanding of the relationships between indoor concentrations of individual VOCs and health outcomes, there are currently no universal health-based guideline values for VOCs within Europe including the UK. In this study, a systematic search was conducted designed to capture evidence on concentrations, emissions from indoor sources, and health effects for VOCs measured in European residences. We identified 65 individual VOCs, and the most commonly measured were aromatic hydrocarbons (14 chemicals), alkane hydrocarbons (9), aldehydes (8), aliphatic hydrocarbons (5), terpenes (6), chlorinated hydrocarbons (4), glycol and glycol ethers (3) and esters (2). The pathway of interest was inhalation and 8 individual aromatic hydrocarbons, 7 alkanes and 6 aldehydes were associated with respiratory health effects. Members of the chlorinated hydrocarbon family were associated with cardiovascular neurological and carcinogenic health effects and some were irritants as were esters and terpenes. Eight individual aromatic hydrocarbons, 7 alkanes and 6 aldehydes identified in European residences were associated with respiratory health effects. Of the 65 individual VOCs, 52 were from sources associated with building and construction materials (e.g. brick, wood products, adhesives and materials for flooring installation etc.), 41 were linked with consumer products (passive, electric and combustible air fresheners, hair sprays, deodorants) and 9 VOCs were associated with space heating, which may reflect the relatively small number of studies discussing emissions from this category of sources. A clear decrease in concentrations of formaldehyde was observed over the last few years, whilst acetone was found to be one of the most abundant but underreported species. A new approach based on the operational indoor air quality surveillance will both reveal trends in known VOCs and identify new compounds.
Children’s exposure to particulate matter (PM) is of great interest because it can cause adverse health effects, including asthma, and decreased lung function. The purpose of this study was to determine the levels of PM in low socio-economic status homes in Omaha, Nebraska. Between October 2018 and September 2019, we collected ambient air PM samples from 30 homes, of which 70% had at least one asthmatic child. Samples were collected at the 2-foot level and the 4-foot level to approximate the breathing zones of toddlers and older children, respectively. We also asked the study participants questions related to indoor air quality (IAQ). Indoor PM levels ranged from 4.28 to 72.81 μg/m3. There was a significant association between IAQ and the furnace filter status (dirty or clean) (p = 0.023, OR = 7.5 [95% confidence interval: 1.40, 39.84]). We found that IAQ status suggests a significant association with the level of housekeeping (p = 0.05, OR = 4.76 [95% confidence interval: 0.95, 23.86]). Indoor PM levels varied significantly between 2 feet and 4 feet (p < 0.05). PM levels could differ substantially depending on the furnace filter’s status. In addition, exposure to PM can significantly depend on the child’s height.
It has been known for a long time that incomplete combustion processes produce by-products that are harmful to human health. Particularly high concentrations of such by-products can arise in indoor environments when operating open flames without venting. The emission behavior of many combustion sources, including candles, has already been examined in detail. However, to date there are no studies in which the chemical composition of the candles is known exactly or where the candles were specifically manufactured for comparative measurements. In this respect, the study presented here, which was designed in collaboration with candle manufacturers and fragrance houses, demonstrates new insights into the emissions of burning candles depending on their composition. All investigations were carried out under controlled climatic conditions in an 8 m³ stainless steel chamber. Combinations of four different fuels (waxes) and five different fragrances in addition to one set of unscented control candles were examined. This resulted in 24 experiments, 20 with scented candles and four with unscented candles. The typical combustion gases carbon monoxide, carbon dioxide and NOx, organic compounds, such as formaldehyde, benzene, and polycyclic aromatic hydrocarbons, PM2.5 and ultrafine particles were monitored in the chamber air and the emission rates were determined. The data were statistically evaluated using parametric and non-parametric methods as well as hierarchical cluster analysis. Exposure scenarios typical for indoor environments were calculated from the emission rates and the results were compared with indoor guidance and reference values. As expected, a multitude of gaseous and particulate emissions were detected. These were typical combustion products as well as evaporated constituents of the fragrance mixtures. In most cases, the calculated indoor concentrations were well below the respective guidance and reference values. The exceptions observed in some cases for nitrogen dioxide, acrolein and benzo[a]pyrene are discussed critically.
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Polycyclic aromatic hydrocarbons (PAHs) in indoor dust are one of the common exposure sources for children worldwide. The aim of this study is to explore PAHs pollution status in indoor dust and estimate health risk on Chinese children with big data. Weighted average concentration was used to analyze source and characterization of PAHs in indoor dust based on peer-reviewed literature. According to specific inclusion criteria, 17 studies were included finally to analyze weighted average concentration. The national average concentration of Σ 16 PAHs was approximately 25.696 µg/g. The highest concentration of Σ 16 PAHs was in Shanxi (2111.667 µg/g), and the lowest was in Hong Kong (1.505 µg/g). The concentrations in Shanxi and Guangdong were higher than national level and the over standard rate was 18.18%. The concentrations of individual PAHs varied greatly across the country, and Flu in Shanxi was the highest (189.400 µg/g). The sources of PAHs varied in different regions and combustion processes played a leading role. PAHs exposure through ingestion and dermal contact was more carcinogenic than inhalation. The incremental lifetime cancer risk model indicated that children lived in Shanxi were found in the highest health risk coupled with the highest BaPE concentration (54.074 µg/g). Although PAHs concentrations of indoor dust showed a downward trend from 2005 to 2018, indoor environmental sanitation should be improved with multidisciplinary efforts. Health standard should be possibly established to minimize children exposure to PAHs in indoor dust in China.
The benefits of nanofibrous media have been extensively explored in laboratory-scale research but are less clear in real filtration applications. Thus, this study investigated the links between the size-resolved filtration efficiency of nanofibrous media mounted in portable air cleaners in a chamber test and results from the media mounted in a cone-shape filter holder in a more conventional duct test. Results showed a similar trend for the filtration efficiency curves for these two experimental tests, despite differences in test type, challenge aerosol, instrumentation, and the calculation of filtration efficiency. Long-term operation, surface area blockage, and isopropyl alcohol treatment adversely impacted the filtration efficiency of the tested nanofibrous media in the chamber test, with a different magnitude of impact for three different media tested. The filtration efficiencies were lower than most of the previously reported data in the literature, which may be due to the differences in medium type, fiber diameter, filter thickness, porosity, face velocity, filter charge, and the number of filter layers. This study suggests the needs for determining the performance of nanofibrous media in terms of filtration efficiency and quality factor in real environmental systems. Copyright © 2021 American Association for Aerosol Research
Technical Report
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Legal notice Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use which might be made of the following information. Foreword In the past decades a large number of studies have indicated the presence of many different compounds belonging to a variety of chemical classes in indoor environments (buildings, homes). The presence of these chemicals in indoor air is the result of infiltration of polluted outdoor air and of emissions from various indoor sources, including building materials, activities of the occupants, consumer products, smoking etc. For many of these chemicals, the risk to human health and comfort is almost totally unknown and difficult to predict because of lack of toxicological data and information on the dose-response characteristics in humans or animal models. On the other hand, a full toxicological testing as requested by the " existing chemicals " legislation is difficult to accomplish for these compounds, because it would involve investigation of acute and subacute toxicity, mutagenicity, carcinogenicity and reproductive toxicity according to testing protocols that are complex, time-consuming and expensive. Moreover, the EU policy on limitation of unnecessary animal testing further limits the possibility of advocating a generalized animal testing of these chemicals. The result of this situation is that there is an objective difficulty in regulating the presence of these substances in indoor air principally because of the absence of adequate hazard and risk assessment. There is therefore an urgent need to develop a strategy for the identification of priorities in testing, assessment and regulation. In the frame of the INDEX project the existing knowledge worldwide has been assessed on-type and levels of chemicals in indoor air and-available toxicological information to allow the assessment of risk to health and comfort. The collection and evaluation of the aforementioned information within the frame of the INDEX project shall contribute to develop a strategy for prioritization in assessment and regulation of chemicals in indoor environments.
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Cited By (since 1996): 63 , Export Date: 4 February 2013 , Source: Scopus , The following values have no corresponding Zotero field: Author Address: EPRI, 3412 Hillview Avenue, Palo Alto, CA 94304-1395, United States Author Address: UMDNJ/R. W. J. Med. Sch./Rutgers, Department of Environmental Medicine, Piscataway, NJ, United States Author Address: Harvard School of Public Health, Department of Environmental Health, Landmark Center, Boston, MA, United States
Burning incense and scented candles indoors is known to produce particles, carbon monoxide and carbon dioxide but relatively few studies have documented their emissions of volatile organic compounds (VOC) and formaldehyde. This study presents a methodology to characterise the emissions of VOCs and formaldehyde from those products. The measurements taken were used to assess health risk for consumers and to make recommendations for use. Methodology: VOCs and formaldehyde emissions from 43 products were measured in a test room of the Centre scientifique et technique du bâtiment (CSTB) experimental house. A testing protocol was established to characterise time-dependent emissions from burning incense and candles. Results: For incense sticks and cones, the highest benzene and formaldehyde emissions were measured during combustion and for an hour afterwards: the concentrations measured then decreased significantly as the pollutants were removed by the ventilation system (0.6 vol/h). Incense cones emitted more formaldehyde than incense sticks, and for incense in general, the higher the burnt mass, the higher the emissions. Benzene and formaldehyde emissions from scented candles were far lower than from incense. Nevertheless, formaldehyde emissions did increase slightly during candle burning, presumably due to secondary reactions. Applications: The experimental methodology presented in this paper was used to assess the risks of indoor exposure to benzene and formaldehyde associated with the combustion of incense and candles. Specific exposure scenarios were developed. Results from this risk assessment have been presented to producers, who have used them to modify their products (mainly by diminution of the burnt mass) or to formulate low-emission products. Exposure scenarios were also used to derive recommendations on indoor use of incense and scented candles.
A series of source tests were conducted to characterize emissions of particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), and total hydrocarbon (THC ) from five types of portable combustion devices. Tested combustion devices included a kerosene lamp, an oil lamp, a kerosene space heater, a portable gas range, and four unscented candles. All tests were conducted either in a well-mixed chamber or a well-mixed room, which enables us to determine emission rates and emission factors using a single-compartment mass balance model. Particle mass concentrations and number concentrations were measured using a nephelometric particle monitor and an eight-channel optical particle counter, respectively. Real-time CO concentrations were measured with an electrochemical sensor CO monitor. CO2, CH4, and THC were measured using a GC-FID technique. The results indicate that all particles emitted during steady burning in each of the tested devices were smaller than 1.0μm in diameter with the vast majority in the range between 0.1 and 0.3μm. The PM mass emission rates and emission factors for the tested devices ranged from 5.6±0.1 to 142.3±40.8mgh−1 and from 0.35±0.06 to 9.04±4.0mgg−1, respectively. The CO emission rates and emission factors ranged from 4.7±3.0 to 226.7±100mgh−1 and from 0.25±0.12 to 1.56±0.7mgg−1, respectively. The CO2 emission rates and emission factors ranged from 5500±700 to 210,000±90,000mgh−1 and from 387±45 to 1689±640mgg−1, respectively. The contributions of CH4 and THC to emission inventories are expected to be insignificant due both to the small emission factors and to the relatively small quantity of fuel consumed by these portable devices. An exposure scenario analysis indicates that every-day use of the kerosene lamp in a village house can generate fine PM exposures easily exceeding the US promulgated NAAQS for PM2.5.
A series of source tests were conducted on the combustion of paraffin and beeswax candles. An enclosed chamber sampling system was utilized, and fine particle samples were collected on both quartz fiber and Teflon filters. Electronic particle sizing was performed using an optical particle counter and a differential mobility analyzer. Filter samples were weighed to determine fine particle mass emission rates and then analyzed for elemental carbon and organic carbon by thermal evolution and combustion analysis and for organic chemical composition by GC/MS. Three modes of candle burning were observed with very different emission profiles: a “normal burning” mode characterized by low mass emission rates and particles smaller than 100 nm in diameter; a “sooting” behavior with high emission rates of predominantly elemental carbon particles; and a “smoldering” phase upon candle extinction during which most of the mass emissions occurred as white particles having diameters between 400 and 800 nm. The majority of emissions were organic compounds including alkanes, alkenes, alkanoic acids, wax esters, cyclohexylalkanes, and alkanals. Analysis of the unburned waxes revealed that while some of these compounds were thermally altered products of the unburned wax, many others were unaltered candle components emitted by direct volatilization. Thus, possible chemical tracers for candle burning may be easily identified by analyzing unburned wax material. The information provided in this study, in conjunction with future ambient indoor air sampling programs and receptor-oriented chemical mass balance techniques, can be used to determine the relative importance of candle burning to indoor soiling problems.
Conference Paper
The paper gives results of testing five types of candles, purchased from local stores, for fine particulate matter (PM) emissions under close-to-realistic conditions in a research house. The test method allows for determination of both the emission and deposition rates. Most test revealed low PM emission rates: in only two was there excessive sooting, with thye PM concentration approaching 1000 micrograms per cubic meter with six and nine burning wocks. Wax breakthrough significantly increased the emissions rate. Smoldering generated more fine PM than several hours of normal burning, causing very high concentrations in a short period of time, which raises concern with potentially acute health effects, especially for children and the elderly. A simple source model is proposed to represent both the stable PM emissions during normal combustion conditions and the sudden concentration surge following flame extinction.