Aerosol Chemistry and Physics - Aerosols: Measurement, Dosimetry, and Health Effects - page 145

2006b; HONO: Sleiman et al., 2010a). The same reactions also produced ultraine secondary
aerosol that was depleted of nicotine and contained oxidation and polymerization by-products
(Sleiman et al., 2010b).
6.2.1.4 Candles
Fine et al. (1999) characterized particles from burning candles. They reported ine PM 1.8 emission
factors of 0.5-4 and 2 mg g −1 , for parafin and beeswax, respectively. The highest emission factors
and elemental carbon concentrations were found when parafin candles were “sooting” (emitting
visible smoke). For both types of wax, less than a third of the ine particulate organic carbon could
be traced to individual compounds. Alkanes, aldehydes, and alkanoic acids were the most abundant
classes of compounds in parafin emissions, relecting the condensation of unburned alkanes on
combustion particles. Emissions from beeswax candles contained the same wax esters, alkanoic
acids and alkanes found in the unburned wax, but also decomposition (alkenes) and combustion
products (aldehydes). The strong odd carbon number preference found in beeswax was relected in
its ine PM composition. The beeswax candles produced very little elemental carbon.
Lead has been found in emissions from some commercially available candles in the United
States and elsewhere (van Alphen 1999; Nriagu and Kim, 2000). Wasson et al. (2002) found lead
in 8 pairs among 100 purchased with metal cores or covers of wicks. They reported airborne lead
emission rates of 100-1700 μg h −1 from individual candles. At an air exchange rate of 0.3 h −1 in a
30 m 3 room, it would take only a few minutes for airborne lead concentrations from a single candle
at the average emission rate of 550 μg h −1 to exceed the EPA's ambient air Pb concentration limit of
1.5 μg m −3 . Using this scenario, Wasson et al. estimated that the room concentration of Pb would be
around 5 μg m −3 for the last 3 h of a 4 h candle burn. Other inorganic constituents have been reported
in candle smoke by Pagels et al. (2009). Flame retardants added to the wick were considered to be
the source of phosphate and alkali nitrates found in candle PM. Candles burning in sooting condi-
tions were also found to produce high levels of black carbon (between 50% and 90% of the total
mass detected on ilters and by a scanning mobility particle sizer).
6.2.1.5 Incense
Incense burning can contribute an important source of indoor ine PM (Mannix et al., 1996). See
et al. (2007) reported a signiicant fraction of ultraine particle emissions from incense burning,
between 16% and 55% of the total particle count. The same authors found that up to 6% of these
emissions were nanoparticles of diameter <50 nm. Incense smoke has not yet been subjected to the
type of comprehensive chemical characterization described earlier for particles from cooking, ire-
places, or cigarette smoke. Because of the variety of ingredients and conigurations used to prepare
incense around the world, acquiring representative data could be very challenging and expensive.
Lung and Hu (2003) reported PM 2.5 and particulate PAH emission factors for two types of handmade
incense, averaging 32 mg g −1 PM 2.5 and 21 μg g −1 PAH. Jetter et al. (2002) reviewed the literature
and reported particulate emission factors for 23 different types of incense purchased in the United
States. They found large numbers of UFP and mass size distributions that typically peaked at around
0.5 μm. PM 2.5 and PM 10 emission factors were statistically indistinguishable, with emission factors
of 5-56 mg g −1 incense and an average emission rate of 42 mg h −1 . They also found that the burn time
ranged from 14 min for one type of incense cone to 3 h or more, for both a smudge bundle and an
incense coil. Average burn time was 43 min. Using an indoor air quality model developed by one of
the coauthors (Guo, 2000), they estimated that one unit of incense with the average emission rate and
burn time would generate a peak concentration of 0.85 mg m −3 if used in a small room (30 m 3 ) with
0.5 air change per hour. Ji et al. (2010) report the characterization of particulate levels in different
rooms within an experimental house: in the proximity of the burning stick, levels were as high as
25,500 particles cm −3 ; the indoor PM 2.5 concentration was 197 μg m −3 , and the speciic surface area
concentration was 180 μm 2 cm −3 . Signiicant modiications of PM levels were registered in other
rooms within the test house.