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US Scented Candles Study
The following is an extract only of a
Master of Science in Public Health thesis entitled "CHARACTERIZATION OF
SCENTED CANDLE EMISSIONS AND ASSOCIATED PUBLIC HEALTH RISKS" by J. DAVID
KRAUSE, Department of Environmental and Occupational Health, College of
Public Health, University of South Florida, August 1999. Major Professor:
Raymond D. Harbison, Ph.D. Copyright by J. David Krause 1999. All rights
reserved. Extracts were chosen (and emphasis added) by The LEAD Group Inc.
ABSTRACT
The recent increased popularity of scented
candles has prompted concerns by consumers and public health officials about
their emission products. According to the National Candle
Association, candle sales are approaching $2 billion annually. The
combustion of scented candles in residences, which typically have low
ventilation rates, may raise indoor concentrations of combustion products. A
recently described phenomenon of residential black soot deposition, sometimes
associated with scented candle usage, prompted concerns that occupant
exposures to soot and other candle emissions may constitute a health risk.
The lack of data on candle emissions prompted this research into the
volatile, semi-volatile and particulate emissions from scented candles and
their potential health risks.
This study characterized the products of
emission by individually burning 91 candles inside a stainless steel
combustion chamber and determining specific emission rates of soot, benzene
and lead. Candle soot was typically less than 1 µm, contained up to 66%
elemental carbon and carried numerous adsorbed organic compounds including
dibutyl phthalate, diethyl phthalate, toluene and styrene. Volatile organic
compound emissions included benzene, styrene, toluene, ethyl benzene,
naphthalene, acetylaldehyde, benzaldehyde, benzene, ethanol, and 2-butanone
(methyl ethyl ketone). Analysis for lead revealed some candles emitted
significant quantities of aerosolized lead during combustion.
A risk assessment of occupant exposures to
soot, benzene and lead resulted in the highest attributable risk being from
soot, ranging from 9.7 x 10-5 to 4.7 x 10-2. Lead
exposures were modelled for children and suggest the potential to raise blood
lead levels of children above 10 µg/dL when typical background exposures are
also present. The possible impacts on public health from consumer use
of scented candles may include increased risk of cancer, neurological and
behavioral deficits and acute aggravation of existing respiratory diseases
such as asthma.
Chapter 3 - Results
Scented candle emissions were determined to
consist of vaporphase and particle-phase components. Low levels of benzene
emissions were also detected from a non-burning candle.
Soot
Particulate emissions exhibited the
physical and chemical characteristics of soot. SEM analysis revealed particle
sizes ranging from 0.045 µm to 0.2 µm diameter.
Elemental carbon content ranged from 6% to
66%, with a median value of 32%. All soot samples tested for semivolatile
organic compounds revealed high quantities of paraffins but varied in amounts
of other adsorbed compounds. Dibutyl phthalate was identified in 33 of 53
samples, diethyl phthalate (8/53), bis (2-ethylhexyl) phthalate (7/53),
didecyl phthalate (4/53), toluene (7/53) and styrene (3/53).
Analysis of soot did not reveal measurable
amounts of benzo[a]pyrene or other PAHs typically identified in combustion
products. This finding was inconsistent with previously reported studies and
could not be readily explained. A recent study of candle soot from
non-scented candles by Fine and Cass also did not reveal measurable amounts
of PAHs.
Soot emissions from scented candles were
significantly higher than those from non-scented candles. Forty five percent
of non-scented (n=11) candles produced detectable amounts of soot, while 63%
of scented candles (n=80) produced detectable amounts of soot. Soot
production from non-scented candles, that produced soot, ranged from 20-175
µg/min/wick (mean 83 µg/min/wick). Soot production from scented candles,
that produced soot, ranged from 20-3100 µg/min/wick (mode 1 = 180, mode 2 =
1650 µg/min/wick). The fine particulate matter collected from candle
emissions was similar to that of diesel engine exhaust in particle size,
morphology, elemental carbon content, and adsorbed chemical constituents,
although lacking detectable quantities of PAHs.
Lead
All candles which had wire core wicks were
tested for lead emissions. Of the 91 candles tested, 27 had wire core wicks
in addition to one candle which was in a metal container. Four of the 27
candles with wire core wicks were determined to emit detectable quantities of
lead, ranging from 0.40 µg/min to 120 µg/min. The candle in the
metal container, which did not have a wire core wick, was found to emit lead
at a rate of 1.3 µg/min. Only one of the candles determined to emit
lead also emitted detectable amounts of soot. This observation suggests that
a visually clean burning candle could still emit significant quantities of
lead.
Chapter 4 - Risk Assessment
Public health risks associated with scented
candle usage, were estimated by identifying chemical emissions and then
determining occupant exposures. The emission characterization performed on
candle emissions in Phase I revealed there was great variability in both the
vapor phase and soluble organic fraction of particulate emissions, but that
the particle size was consistently less than 1 µm. The first step in
assessing risk is identifying the chemical hazards associated with candle
emissions.
Hazard Evaluation
Soot
While unit risk values exist for many of
the vapor phase emissions from candles, unit risk values for candle soot have
not been developed. Due to the numerous similarities between candle soot and
diesel soot, the unit risk value for diesel exhaust could be used for the
purpose of assessing risk associated with candle soot…. IARC has
classified diesel exhaust as a probable human carcinogen 2A.
Lead
Although lead was only detected in the
emissions of 5 out of 91 candles, the implications of lead exposures from a
previously uncharacterized source supports its inclusion in this risk
assessment. Extensive data exist on exposures to lead in both occupational
and residential settings. Tremendous resources have been expended to remove
lead containing materials from homes and schools.
Exposure Modelling
Due to the lower air exchange rates in
newer homes, the residence time of emissions were determined to continue for
up to 10 hours after extinguishing a candle.
Risk Characterisation
Scented candles have become common-place in
homes and in certain businesses such as boutiques, salons, and spas. However,
the indoor environment where the most significant exposures are likely to
take place, due to low ventilation rates and long duration of occupancy, are
homes.
Chapter 5 - Discussion
Scented candle usage indoors may cause high
levels of respirable soot, with risks to occupants for both acute and chronic
health effects, including an increased risk of cancer. Similarities between
candle and diesel soot, suggest the potential for similar toxicological
effects on exposed occupants.
Comparison with Diesel Exhaust
Studies indicated that filtered diesel
exhaust is not as toxic or carcinogenic as whole diesel exhaust. The marked
difference between whole and filtered diesel exhaust was also evident from
general toxicological indices such as decreased body weights, increased lung
weights, pulmonary function measurements, and pulmonary histopathology in
animals (ie. proliferation of Type II cells and changes in the respiratory
bronchiolar epithelium, and fibrosis). Numerous studies have shown that
animal exposure to diesel particles plus vapor-phase compounds produced
biochemical and cytological changes in the lung that are much more prominent
than those evoked by the vapor-phase chemicals alone. These studies point to
the predominant effects that soot may have on occupant health. Comparison of
the particle-phase products from diesel and candle emissions is essential to
demonstrate similarities in potential toxicity.
Acute health endpoints due to soot exposure
include reduction in alveolar macrophage activity and acute inflammatory
response. For individuals with pre-existing asthma and allergies an increased
risk of acute attacks are also potential health effects. The US EPA has
determined a Reference Concentration (RfC) for diesel exhaust of 5 µg/m3.
The American Conference of Governmental Industrial Hygienists (ACGIH) has
served notice of intent to change the Threshold Limit Value (TLV) for diesel
exhaust particulate from 150 µg/m3 to 50 µg/m3 for 8
hour exposures. These are considered safe levels of exposure based upon a
scientific consensus. The lowest observable adverse effects level (LOAEL) for
DPM has been determined to be 300 µg/m3 (HEC [human equivalent
concentration]). The no observable adverse effects level (NOAEL) was
determined to be 155 µg/m3 (HEC). The concentrations of candle
soot an occupant may be exposed to due to candle combustion may be
significantly higher.
Ambient Particulate Matter
Concerns of population risks associated
with exposure to submicron dust particulate and its impact on acute
respiratory and cardiopulmonary disease has resulted in regulation of ambient
particulate levels. Changes in NAAQS to include regulation of particulate
matter 2.5 µm and smaller (PM2.5) are intended to address microscopic soot,
which is believed to contribute greatly to the urban illnesses associated
with air pollution. The contribution of candle soot during indoor exposures
can be orders of magnitude higher than outdoor exposures and may be
significant sources of total soot exposure.
Conclusions
Soot Exposure Risks
The characteristics observed in
candle emissions match those of diesel emissions in the aspects considered to
contribute to toxicity. Their size, less than 1 µm, allows deep
penetration of the respiratory system and alveolar deposition. The insoluble,
carbonaceous core structure with high surface area allows adsorption of
extractable volatile, and semi-volatile organic compounds. Its origin is
from the incomplete combustion of hydrocarbon containing fuel, allowing the
formation of aromatic structures, which become adsorbed to the carbonaceous
core. Studies of diesel particulate have indicated the above factors are
those which contribute to its toxicity and carcinogenicity. Diesel soot and
candle soot share the same physical and many of the same chemical properties
which are believed to contribute to both toxicity and carcinogenicity. These
similarities point to a similar potential for adverse health effects.
Comparison with the reference concentration
(RfC = 5 µg/m3) for diesel soot shows the emissions from candles
can cause significantly higher exposures to occupants (3-520 µg/m3).
This exposure indicates that further examination of scented candle emissions
is needed to determine its toxicity and carcinogenicity. Due to the current
absence of information on scented candle emission toxicity, and its numerous
similarities with diesel exhaust, it would be prudent to tentatively adopt
the recognized toxicity values for diesel emissions until specific testing
can be accomplished. When the unit cancer risk for diesel exhaust is applied
to exposures to candle soot, the estimated increased cancer risk for
a lifetime exposure, would range from 9.7 x 10-5 to 3.0 x
10-4 for the lowest emitting candle to 1.5 x 10-2 to
4.7 x 10-2 for the highest emitting candle, using the
range of unit cancer risk of 2.9 x 10-5 to 9.0 x 10-5
per µg/m3.
Benzene Exposure Risks
Candle emissions can contribute to
increased exposure to benzene and other potentially carcinogenic volatile and
semi-volatile organic compounds. Average daily inhalation exposures to
benzene were found to range from 0.02 - 1.6 µg/m3-day due to the
use of 1 candle per day. The carcinogenic risk attributable to a lifetime
exposure would range from 3.3 x 10-8 to 1.2 x 10-7 for
the lowest emitting candle to 3.5 x 10-6 to 1.2 x 10-6
for the highest emitting candle using the Inhalation Unit Risk of 2.2 x 10-6
to 7.8 x 10-6 per µg/m3. Further consideration of
benzene as a significant risk in the use of scented candles should be made.
Due to the use of multiple candles simultaneously, occupants may become
exposed to levels of benzene constituting a cancer risk greater than 1 x 10-5.
Lead Exposure Risks
Average daily doses of lead were shown to
range from 0.4 to 120 µg/day. By comparison, the upper range of these values
exceeds the equivalent dose caused by exposure to the NAAQS limit of
atmospheric lead of 1.5 µg/m3, equivalent to 30 µg/day. Using
the IEUBK model, blood lead levels for children 2-3 years of age could exceed
10 µg/dL if exposed to daily emissions of certain candles which emit lead.
Summary
Use of scented candles may contribute
significant quantities of pollutants to the indoor environment, especially
soot, benzene and lead. Dozens of other compounds were identified in
individual candles, but their contribution to occupant risks were not
characterized in this limited scope risk characterization. Due to the
variability in candles and their respective emission rates, great uncertainty
would exist in a generalized risk assessment. The available data suggest that
each candle type should be evaluated for its emissions and contribution to
occupant exposure. There appear to be three distinct candle types with
regards to soot emissions; low emitting candles, with no detectable emissions
of soot; moderate emitting candles ranging from 20-600 µg/min; and high
emitting candles ranging from 900 to 3000 µg/min. It has also been observed
that visible soot emissions are not associated with significant lead
emissions, thus do not offer any protective warnings for users. The absence
of consumer warnings concerning candle emissions and their potential health
effects may contribute to exposure of susceptible individuals to respiratory
inflammatory agents, carcinogens and teratogens.
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