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The effects of evaporating essential oils on indoor air quality

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Essential oils, predominantly comprised of a group of aromatic chemicals, have attracted increasing attention as they are introduced into indoor environments through various forms of consumer products via different venues. Our study aimed to characterize the profiles and concentrations of emitted volatile organic compounds (VOCs) when evaporating essential oils indoors. Three popular essential oils in the market, lavender, eucalyptus, and tea tree, based on a nation-wide questionnaire survey, were tested. Specific aromatic compounds of interest were sampled during evaporating the essential oils, and analyzed by GC-MS. Indoor carbon monoxide (CO), carbon dioxide (CO2), total volatile organic compounds (TVOCs), and particulate matters (PM10) were measured by real-time, continuous monitors, and duplicate samples for airborne fungi and bacteria were collected in different periods of the evaporation. Indoor CO (average concentration 1.48 vs. 0.47 ppm at test vs. background), CO2 (543.21 vs. 435.47 ppm), and TVOCs (0.74 vs. 0.48 ppm) levels have increased significantly after evaporating essential oils, but not the PM10 (2.45 vs. 2.42 ppm). The anti-microbial activity on airborne microbes, an effect claimed by the use of many essential oils, could only be found at the first 30–60 min after the evaporation began as the highest levels of volatile components in these essential oils appeared to emit into the air, especially in the case of tea tree oil. High emissions of linalool (0.092–0.787 mg m−3), eucalyptol (0.007–0.856 mg m−3), d-limonene (0.004–0.153 mg m−3), ρ-cymene (0.019–0.141 mg m−3), and terpinene-4-ol-1 (0.029–0.978 mg m−3), all from the family of terpenes, were observed, and warranted for further examination for their health implications, especially for their potential contribution to the increasing indoor levels of secondary pollutants such as formaldehyde and secondary organic aerosols (SOAs) in the presence of ozone.
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Atmospheric Environment 41 (2007) 1230–1236
The effects of evaporating essential oils on indoor air quality
Huey-Jen Su, Chung-Jen Chao, Ho-Yuan Chang, Pei-Chih Wu
Department of Environmental and Occupational Health, College of Medicine, National Cheng Kung University, 138 Sheng Li Road,
Tainan 70428, Taiwan, ROC
Received 8 May 2006; received in revised form 19 September 2006; accepted 22 September 2006
Abstract
Essential oils, predominantly comprised of a group of aromatic chemicals, have attracted increasing attention as they are
introduced into indoor environments through various forms of consumer products via different venues. Our study aimed
to characterize the profiles and concentrations of emitted volatile organic compounds (VOCs) when evaporating essential
oils indoors. Three popular essential oils in the market, lavender, eucalyptus, and tea tree, based on a nation-wide
questionnaire survey, were tested. Specific aromatic compounds of interest were sampled during evaporating the essential
oils, and analyzed by GC-MS. Indoor carbon monoxide (CO), carbon dioxide (CO
2
), total volatile organic compounds
(TVOCs), and particulate matters (PM
10
) were measured by real-time, continuous monitors, and duplicate samples for
airborne fungi and bacteria were collected in different periods of the evaporation. Indoor CO (average concentration 1.48
vs. 0.47 ppm at test vs. background), CO
2
(543.21 vs. 435.47 ppm), and TVOCs (0.74 vs. 0.48 ppm) levels have increased
significantly after evaporating essential oils, but not the PM
10
(2.45 vs. 2.42 ppm). The anti-microbial activity on airborne
microbes, an effect claimed by the use of many essential oils, could only be found at the first 30–60 min after the
evaporation began as the highest levels of volatile components in these essential oils appeared to emit into the air,
especially in the case of tea tree oil. High emissions of linalool (0.092–0.787 mg m
3
), eucalyptol (0.007–0.856 mg m
3
), D-
limonene (0.004–0.153 mg m
3
), r-cymene (0.019–0.141 mg m
3
), and terpinene-4-ol-1 (0.029–0.978 mg m
3
), all from the
family of terpenes, were observed, and warranted for further examination for their health implications, especially for their
potential contribution to the increasing indoor levels of secondary pollutants such as formaldehyde and secondary organic
aerosols (SOAs) in the presence of ozone.
r2006 Elsevier Ltd. All rights reserved.
Keywords: Essential oils; Indoor air quality; Airborne microbes; Terpenes; Formaldehyde; Secondary organic aerosols
1. Introduction
Essential oils and some extracted fragrance com-
pounds are widely adopted into modern society for
their capacity, at least reportedly, in generating
pleasant odors, and providing anti-bioactivity bene-
fits regardless of lacking sufficient scientific evidence
to elucidating the specific effects and their corre-
sponding mechanisms (Lahlou, 2004). Meanwhile, it
is only natural that use of essential oils and products
containing fragrances will release mixed volatile
organic compounds (VOCs) into the indoor air,
and many of these, such as terpenes and D-limonene,
have demonstrated a significant role in the formation
of secondary organic aerosols (SOA), often more
irritating or allergenic than the original substance,
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doi:10.1016/j.atmosenv.2006.09.044
Corresponding author. Tel.: +8 8 6 6 275 2459;
fax: +8 8 6 6 274 3748.
E-mail address: amb.wu@msa.hinet.net (P.-C. Wu).
after oxidation (Wainman et al., 2000). Yet, whether
emission from evaporating or heating essential oils
can affect the profiles of indoor air quality has not
been investigated comprehensively thus far. We
therefore began by examining the emission patterns
of evaporating essential oils with burning candles
underneath incense evaporator in typical office and
residential environment to further characterize the
effects of evaporating essential oils on typical indoor
air pollutants (CO, CO
2
,andPM
10
) and airborne
microbes in these environments.
2. Research methods
Three best-sold essential oils, together comprising
more than 50% of total sale volume, were selected
for the field study based on market survey, including
lavender (Lavandula angustifolis), eucalyptus (Eu-
calyptus globules), and tea tree (Melaleuca alter-
nifolia). Bulk samples of these essential oils were
analyzed in our own laboratory by GC-MS to
characterize the chemical compositions following
the procedures reported previously (Chaintreau et
al., 2003), and 300 ml of each essential oil were
diluted with 50 ml water for use in incense
evaporator with burning candle.
Two different types of indoor environments, one
bedroom (space volume: 21.6 m
3
; air change rate
(ACH): 1.8 h
1
) and one small office (space volume:
28.2 m
3
; ACH: 1.3 h
1
) were chosen for the experi-
ment. Before evaporating, 30 min background
sampling was performed to measure background
levels of various indoor air pollutants, including
CO, CO
2
, total volatile organic compound
(TVOCs), and PM
10
, using continuous monitor.
Carbon dioxide (CO
2
) and carbon monoxide (CO)
were measured by using Q-track monitor (Model-
8550, TSI Inc., USA) with detection ranges within
0.04–1000 ppm for CO and 0–5000 ppm for CO
2
.
PM
10
was measured by Dust-track monitor (TSI
Inc., USA) with the detection range within
0.06–5000 mgm
3
. TVOCs was measured by using
ppbRAE air monitor (PGM-7240, RAE system
Inc., USA) with the detection range within
0–200 ppm. All real-time data were recorded by
one data per minute during the sampling period.
Airborne microbes were also collected before study.
Monitoring during evaporating essential oils began
after background profiles had been established, and
were continuously recorded for at least 3 h for each
round of test with triplicate tests completed for each
essential oil in each testing space. All real-time data
were recorded with the frequency of one data point
per minute during the sampling period. Duplicate
samples of airborne fungi and bacteria were
collected using Burkard sampler (Rickmansworth,
UK) with malt extract agar plates (MEA) and
tryptic soy agar (TSA) at a flow rate of 10 LPM
(Macher et al., 1995;Su et al., 2001). Airborne fungi
and bacteria were collected at 0, 30, 60, 120, and
180 min within the period of evaporating essential
oils. Fungi were cultured, incubated, and identified
before average concentrations of duplicated sam-
ples, as colony forming unit per cubic meter
(CFU m
3
), were calculated for the sampling site
(Wu et al., 2005).
Stainless-steel tubes filled with Tanex-TA and
Carboxen for absorbing VOCs (EPA-TO-17) were
equipped with a sample pump (SKC 223-3, U.S.A.),
and sampling at flow rate of 70 ml min
1
during the
period of evaporating each essential oils in the
testing space for VOCs sampling. Air samples were
sealed by stainless-steel cap and sent to laboratory
to be desorbed by automatic thermal desorption
system (ATD-400, PerkinElmer Inc., USA), and
directly transferred to GC-MS (Hewlett-Packard
GC-5890; Hewlett-Packard MS-5972)(Rastogi et
al., 2001). All procedures were completed within
30 min in our own laboratory. Specific VOCs,
including two monoterpene hydrocarbons (D-limo-
nene and r-cymene), one monoterpene ether (eu-
calyptol), and two monoterpene alcohols (linalool
and terpinene-4-ol) were chosen as indicators. They
were thermally extracted, analyzed, and quantified
by standard curve using GC-MS set at the identical
condition as for bulk sample analysis.
Wicoxon signed rank test was applied to compare
the indoor pollutants’ concentrations before and
after evaporating essential oils, and Friedman test
to examine whether the change of fungal or
bacterial concentrations at different sampling per-
iods.
3. Results
The effects of evaporating essential oils on indoor
TVOCs concentrations in the testing spaces are
shown in Fig. 1. The emissions of VOCs mostly
occurred, both at home and office environment,
during the first 20 min of initial evaporation of
eucalyptus and tea tree oil. The emissions of TVOCs
of lavender oil seemed to be slower than eucalyptus
and tea tree oils, yet, also reaching steady state
within 30–45 min, either at home or at office space.
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H.-J. Su et al. / Atmospheric Environment 41 (2007) 1230–1236 1231
The average concentrations of CO
2
and CO were
significantly higher (CO
2
: 543.21ppm and CO:
1.48 ppm) in the testing periods, compared to back-
ground levels (CO
2
:435.47andCO:0.47ppm)
(Table 1). The levels of PM
10
were observed to have
a minor increase during the evaporating test, yet
without statistical significance (p¼0.053). Indoor
concentrations of total airborne bacteria appeared to
decrease after evaporating lavender, eucalyptus, and
tea tree oils regardless of being in office or home
environment, and the lowest level was found at
30 min after evaporating when the highest levels of
volatile components of these essential oils appeared
to have emitted into the air (Fig. 2). Unfortunately,
their effects on airborne bacteria did not seem to
persist through time especially in the naturally
ventilated home. Similar phenomenon was also
observed with airborne fungi when airborne fungal
levels began to decrease after the first 30min.
The levels of indicator VOCs during the testing
periods (180 min) were shown in Table 2.Thelevelof
linalool, a major composition of lavender oil, was
between 496.04 and 986.90 mgm
3
, when evaporating
lavender oil in the testing space. D-limonene was
ARTICLE IN PRESS
0
0.5
1
1.5
2
2.5
-150 1530456075
90
105 120 135 150 165
Time (min)
TVOC (ppm)
Lavender
Eucalyptus
Tea tree
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
TVOC (ppm)
Lavender
Eucalyptus
Tea tree
-150 1530456075
90
105 120 135 150 165
Time (min)
(a)
(b)
Fig. 1. The effects of evaporating essential oils on the indoor TVOCs concentrations in the testing spaces ((a) homes and (b) office).
H.-J. Su et al. / Atmospheric Environment 41 (2007) 1230–12361232
released from all three essential oils, and the
concentrations were between 2.37 and 69.32 mgm
3
in testing office and home, respectively. Terpinene-4-ol
wasalsofoundinthreeessentialoils,showing
highest levels when evaporating tea tree oils
(467.68–954.18 mgm
3
). Eucalyptol (1,8-cineole) was
ARTICLE IN PRESS
Table 1
Levels of indoor air pollutants during background and evaporating periods
Pollutants (unit) Cycles of testing Average concentrations (SD) p-value
Background (30 min) Evaporating period (180 min)
CO (ppm) 15 0.47 (0.87) 1.48 (1.13) o0.01
CO
2
(ppm) 18 435.47 (109.14) 543.21 (71.65) o0.01
PM
10
(mgm
3
) 17 2.42 (1.44) 2.45 (1.42) 0.05
TVOCs (ppm) 18 0.48 (0.30) 0.74 (0.45) o0.01
0
500
1000
1500
2000
2500
3000
0 30 60 120 180
min
Bacteria (CFU/m3)
Lavender_Office
Eucalyptus_Office
Tea tree_Office
Lavender_Home
Eucalyptus_Home
Tea tree_Home
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 30 60 120 180
min
Fungi (CFU/m3)
Lavender_Office
Eucalyptus_Office
Tea tree_Office
Lavender_Home
Eucalyptus_Home
Tea tree_Home
(b)
(a)
Fig. 2. The effects of evaporating essential oils on airborne bacteria (a) and fungi (b).
H.-J. Su et al. / Atmospheric Environment 41 (2007) 1230–1236 1233
a major compound in eucalyptus and tea tree oils, and
the higher levels were observed when evaporating
eucalyptus oils (203.09–1540.62 mgm
3
). r-Cymene
showed a strong presence both in eucalyptus and tea
tree oils, and higher levels were found when evaporat-
ing the latter (72.25–173.23 mgm
3
).
4. Discussion
Our finding suggests that most VOCs in the
essential oils would emit into the air within the first
30 min, while the emission patterns varied in each
evaporating test. The most likely rationale to justify
these variations might be attributable to various
burning temperatures associated with different
candles. Combustion-related emissions products,
including CO
2
and CO also significantly increased
during the evaporating period as expected. Such a
phenomenon might suggest the need of fresh air
intake when evaporating essential oils using an
incense evaporator with a burning candle. Com-
pared to other claims, the anti-microbial activity of
essential oils has been the one with more scientific
evidences, and documentations for bioactivity of
lavender, tea tree, and eucalyptus oils under
diffusion or contact study-setting were available
(Viljoen et al., 2003;Lis-Balchin and Hart, 1999;
Hammer et al., 1999;Inouye et al., 2001;Pattnaik et
al., 1997). Our study is, thus far, the first to
demonstrate the effects of using essential oils on
reducing airborne microbial levels. These results
implied that the reduction of airborne microbes
when evaporating essential oils could only be
observed during the first 30–60 min when the highest
levels of volatile components in these essential oils
appeared to emit into the air. The effect, yet, did not
seem to persist through, and was easily disturbed by
outdoor sources and other contributions of fugal
levels from indoor human activities. While benefits
of using various essential oils have been advocated
for commercial purpose, only a few studies in the
literature have aimed to elucidate the specific effects
of these essential oils, and the mechanisms of their
bioactivities. The reported bioactivities of essential
oils have included insecticidal activity, anti-micro-
bial activity, effects on musculoskeletal system,
neurological effects, blood pressure action, gastro-
protective effect, sedative, and antispasmolytic
actions (Lahlou, 2004). Yet, with increasing usage
and exposure to essential oils and related fragrant
compounds, concerns on clarifying more specifically
their potential health and environmental impacts
have arisen in recent decades. Meanwhile, a large
quantity of VOCs with complex mixture is also
likely to be emitted into indoor air when using
essential oils and products containing rich fra-
grance. The major constituents of these three testing
oils often include linalool, eucalyptol (1,8-cineole),
D-limonene, r-cymene, g-terpinene, and terpinene-4-
ol-1 belong to the family of terpenes. Terpennoids
are a group of unsaturated hydrocarbons and
oxygen-containing compounds mainly emitting
from plants in nature. Previous studies have
indicated that these monoterpenes (hydrocarbons,
alcohols, and ethers) with one or more unsaturated
carbon–carbon bonds may easily interact with
oxidants, such as ozone, hydroxyl and nitrate
radicals, in general environments, and generate
consequently a variety of secondary organic pollu-
tants in gas and particle phase (Weschler, 2000). The
oxidation products of terpenes, such as D-limonene,
a-pinene, and linalool, have been characterized by
atmospheric chemists to include a number of higher
molecular weight oxidation products include alde-
hydes, ketones, organic aicds, and diacids (Grosjean
et al., 1992;Reissell et al., 1999;Grosjean et al.,
1993;Shu et al., 1997;Hakola et al., 1994). One
major product derived from reaction between
oxidants and terpenes is formaldehyde, and serial
studies have shown O
3
/terpene reactions are
important sources of secondary indoor air pollu-
tants including secondary hydroscopic organic
aerosols (SOAs) which are mainly of sub-micron
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Table 2
Levels of indicative volatile organic compounds during the testing
periods (180 min)
Compounds (mgm
3
) Office Home
1st 2nd 3rd 1st 2nd 3rd
Lavender
Linalool 533 496 604 987 779 594
D-limonene 12 6 2 32 21 28
Terpinene-4-ol 100 74 56 198 89 48
Eucalyptus
Eucalyptol 523 1541 503 263 203 522
D-limonene 69 36 34 13 13 32
r-Cymene 58 46 — 14 16 28
Terpinene-4-ol 71 77 33 31 27
Tea tree
Eucalyptol 94 97 42 80 53 34
D-limonene 23 19 6 3 5
r-Cymene 132 119 72 173 157 91
Terpinene-4-ol 882 903 623 954 840 468
H.-J. Su et al. / Atmospheric Environment 41 (2007) 1230–12361234
particles (Sarwar et al., 2004;Iinuma et al., 2004).
These oxidation products have attracted rising
concerns as many of them seem to be more irritating
than their precursors (Karlberg and Dooms-Goos-
sens, 1997;Wolkoff et al., 1999;Wolkoff et al.,
2000), and fine to ultra-fine particles are known to
penetrate into lower respiratory system more easily.
The concentration levels reported in this investiga-
tion can be of great importance as they may well be
the first set of field concentrations for various
terpenes measured during the evaporation of
essential oils in general indoor environments. These
data indicate that evaporating essential oils could be
another hidden source of indoor terpenes, and
deserve more attention for its potential impacts on
indoor air quality, especially on the levels of
secondary pollutants such as formaldehyde and
SOAs.
Although, the scientific evidence regarding the
effects of these aromatic compounds remains
limited, they have been at least suggested to be
sensitization agents (Buckley et al., 2003). Exposure
to fragrance and essential oils from the air has also
induced or worsened respiratory problems including
decrease of pulmonary function and increase of
chest tightness, wheezing and exacerbates asthma in
susceptible subjects (Kumar et al., 1995;Millqvist et
al., 1999;Millqvist and Lowhagen, 1996;Galdi et
al., 2004). In addition, fragrances are also accounted
for the cause to occupational asthma (Baur et al.,
1999;Lessenger, 2001), and respiratory symptoms
and other nonspecific symptoms in susceptible
subjects triggered by exposure via airway and other
sensory pathway (Millqvist et al., 1999), with many
of them being similar to those described in multiple
chemical sensitivity and sick building syndromes
(Millqvist et al., 1999;Opiekun et al., 2003). Our
investigation illustrates the range of concentrations
that may potentially result from evaporating essen-
tial oils in a manner commonly employed by a great
proportion of Taiwanese population. The findings
warrant a need for further evaluation on health
consequences of applying essentials in the above-
discussed fashion.
Acknowledgments
The authors are in great debt to the building
owners for their understanding and cooperation
during the long process and sampling activities.
We also thank our colleagues participating in the
field investigations, and helping in the laboratory
task. Taiwan National Science Council (NSC
93-2320-B-006-070) grants have in part, supported
this study. It is to be noted that partial data
reported in this work have appeared as preliminary
results and were published in the proceedings of
indoor air 2005.
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ARTICLE IN PRESS
H.-J. Su et al. / Atmospheric Environment 41 (2007) 1230–12361236
... Because of their volatile nature, EOs can be utilized in vapor phase with no direct contact with food, although toxicity and allergenicity still need evaluation. EO vapors should be dispersed via natural evaporation because heat can alter EO components (72,116) and use of water-based media such as agar or broth can reduce antimicrobial activity (62,72). The antimicrobial activity also can diminish over time (38,116). ...
... EO vapors should be dispersed via natural evaporation because heat can alter EO components (72,116) and use of water-based media such as agar or broth can reduce antimicrobial activity (62,72). The antimicrobial activity also can diminish over time (38,116). Su et al. (116) found that when lavender, eucalyptus, and tea tree EOs were evaporated in a small room, antimicrobial activity was present in only the first 30 to 60 min. ...
... The antimicrobial activity also can diminish over time (38,116). Su et al. (116) found that when lavender, eucalyptus, and tea tree EOs were evaporated in a small room, antimicrobial activity was present in only the first 30 to 60 min. Despite these limitations, EO vapors have potential uses in food packaging systems. ...
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Consumer safety concerns over established fresh produce washing methods and the demand for organic and clean-label food has led to the exploration of novel methods of produce sanitization. Essential oils (EOs), which are extracted from plants, have potential as clean-label sanitizers because they are naturally derived and act as antimicrobials and antioxidants. In this review, the antimicrobial effects of EOs are explored individually and in combination, as emulsions, combined with existing chemical and physical preservation methods, incorporated into films and coatings, and in vapor phase. We examined combinations of EOs with one another, with EO components, with surfactants, and with other preservatives or preservation methods to increase sanitizing efficacy. Components of major EOs were identified, and the chemical mechanisms, potential for antibacterial resistance, and effects on organoleptic properties were examined. Studies have revealed that EOs can be equivalent or better sanitizing agents than chlorine; nevertheless, concentrations must be kept low to avoid adverse sensory effects. For this reason, future studies should address the maximum permissible EO concentrations that do not negatively affect organoleptic properties. This review should be beneficial to food scientists or industry personnel interested in the use of EOs for sanitization and preservation of foods, including fresh produce. Highlights:
... There is a broad literature suggesting that flavoring compounds like black pepper, cinnamon, vanilla, lemon/lime, mint, fir/pine, and eucalyptus contribute to airway toxicity, specifically, impaired respiratory immune cell function, cytotoxicity, and increases in oxidative stress (Hickman et al., 2019). Furthermore, room diffused essential oils, including lavender, eucalyptus, and tea tree have also been previously found to release known hazardous chemicals, such as terpenes, toluene, and benzene (Chiu et al., 2009;Su et al., 2007), which can cause respiratory symptoms including breathlessness and respiratory hyper-responsiveness in people with and without asthma (Chiu et al., 2009;Su et al., 2007). Lavender and tea tree oils may also act as endocrine-disrupting compounds, disrupting hormonal homeostasis (Ramsey et al., 2019). ...
... There is a broad literature suggesting that flavoring compounds like black pepper, cinnamon, vanilla, lemon/lime, mint, fir/pine, and eucalyptus contribute to airway toxicity, specifically, impaired respiratory immune cell function, cytotoxicity, and increases in oxidative stress (Hickman et al., 2019). Furthermore, room diffused essential oils, including lavender, eucalyptus, and tea tree have also been previously found to release known hazardous chemicals, such as terpenes, toluene, and benzene (Chiu et al., 2009;Su et al., 2007), which can cause respiratory symptoms including breathlessness and respiratory hyper-responsiveness in people with and without asthma (Chiu et al., 2009;Su et al., 2007). Lavender and tea tree oils may also act as endocrine-disrupting compounds, disrupting hormonal homeostasis (Ramsey et al., 2019). ...
... Although they did not focus on essential oils, they stated that the indoor air concentration of common fragrances fell below the threshold for sensory irritations. However, if the indoor air concentrations of odors are very high, they may cause severe adverse health effects [69,70]. Thus, it is crucial that aromas be disseminated within a range of concentration that does not negatively affect human health. ...
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Indoor environment has an appreciable impact on occupants' mood, health and performance. Among numerous indoor environmental components, indoor air quality is often considered to be one of the most crucial ones. While odor is a decisive factor for evaluating perceived indoor air quality, its effects - particularly the positive effects of pleasant aromas - on human responses and performance have yet to be revealed. In this study, experiments were conducted to investigate the effect of indoor aroma on students' mood and learning performance. Participants comprised 76 university students and they performed two learning tasks under one of the four odor conditions: “control (aromaless)”, “rosemary”, “lemon”, and “peppermint.” First, the way in which students sense the indoor aroma in a study space was investigated using several mood scales, including odor intensity, pleasantness, preference, acceptability, and impression. Second, the influence of indoor aroma on learning and memory performance was quantitatively assessed using a reading task and a verbal memory task. Lastly, the impacts of odor preference on subjective evaluation and performance were explored. This experiment showed that subjective evaluations were significantly different before and after olfactory adaptation, particularly in the rosemary condition. Of all three aroma conditions, the lemon aroma had the highest preference and led to the highest scores in the memory task. Although the significant impact of indoor aroma on learning performance was not detected, our results indicated that pleasant aroma has the potential to enhance students’ mood and learning performance.
... A previous study characterized the profiles and concentrations of emitted VOCs when evaporating essential oils indoors in Taiwan homes. The results showed that high emissions of linalool, eucalyptol, D-limonene, etc., were observed after the evaporation began, as the highest levels of VOCs in these essential oils appeared to emit into the indoor air [17]. Theoretically, these substances showed anti-inflammatory and anticancer properties in laboratory studies [18][19][20]. ...
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It is still unknown whether long-term inhalation of indoor air pollutants from ambient essential oil is associated with increased cardiopulmonary events. We recruited 200 healthy homemakers to conduct a prospective observation study in Northern Taiwan. We measured heart rate (HR), systolic blood pressure (SBP), diastolic BP (DBP), peak expiratory flow rate (PEFR), and indoor air pollutants four times per year for each participant between 2008 and 2018. Moreover, a questionnaire related to essential oil usage, home characteristics, and health status was filled out with each participant. The association between essential oil usage and cardiopulmonary health was determined using mixed-effects models. The mixed-effects models showed a significant association between essential oil usage and adverse cardiopulmonary effects including increased HR and BP and decreased % predicted PEFR among participants with heavy use of essential oils. No significant association between essential oils usage and adverse cardiopulmonary effects was observed among participants without essential oils usage or participants with mild use of essential oils (less than one hour per day). We concluded that exposure to indoor air pollution related to essential oils was associated with adverse cardiopulmonary effects among participants with essential oil usage more than one hour per day.
... Essential oils are easily biodegradable and do not contaminate the environment as much as synthetic compounds, making them suitable candidates for the development of mosquito repellents (Das et al. 2015). However, several risks associated with their use in indoor environments are still tested (Huey-Jen et al. 2007;Angulo-Milhem et al. 2021). ...
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Essential oils have been tested as insect repellents with moderate results. The most important characteristics of these oils are that they possess a high chemical diversity of compounds, are cheap, and are easily accessible. Recently, mixtures of essential oils have shown a higher repellent activity than a single essential oil, probably by increasing the effectiveness with the number of chemicals in the mixture. The repellent effect of essential oils from citronella (Cymbopogon nardus), mint (Mentha arvensis), rosemary (Rosmarinus officinalis L.), clove (Eugenia caryophyllata), and their mixture was evaluated against Aedes aegypti. The mixture of citronella, mint, and clove essential oils (1:1:1) was also evaluated in an adulticidal bioassay. Additionally, chemical identification was performed using these commercial essential oils. The 1:1:1 mixture of citronella, mint, and clove essential oils was as effective as the commercial repellent DEET at lower doses (5%), and it is a good candidate for an adulticide at higher doses (20–25%). The chemical constituents of the essential oils were mostly terpenes and oxygenated terpenoids. These findings were discussed in terms of economic and environmental frameworks.
... Lemon oils were found to be potent biological fungicide for ochratoxin producing Aspergillus niger (Verma et al., 2011a). A. niger (Verma et al., 2011b) VOCs produced from evaporation of essential oils of lavender, eucalyptus and tea tree Air-borne fungi samples (Su et al., 2007) ...
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Bioaerosols in indoor environment include substantial portion of fungi which are considered as “hidden killers”. Pakistan like other countries, also bears the atrocities of fungi and their mycotoxins and suffers more due to its favourable climate, weak economy and unawareness. Genus Aspergillus of Fungi is quite important and is predominant in indoor environment, along with Penicillium. There are not adequate research studies on the indoor micro-floral composition, however, the available data shows that numerous Aspergillus species are found inside the buildings whether they be houses, hospitals, laboratories, cafeteria or slaughterhouses. The mycotoxins produced by Aspergillus species include aflatoxins, fumonisins, citrinin, ochratoxins and cyclopiazonic acid. They are mainly carcinogenic and cause various diseases like aflatoxicosis, pentaketide nephrotoxin, and necrosis. To avoid such issues, fungal growth should be avoided by controlling temperature and humidity. In addition, fungicides, ultraviolet radiation or essential oils can be used against fungi. The condition of the buildings can also be adjusted to minimize fungal growth like building material, ventilation system, wall paint and hygiene. The database of the country is not satisfactory with insignificant laws and regulation. To estimate the potential risks of Aspergillus species and their mycotoxins, regular monitoring is required at all levels. It will also help to devise solutions related to health and environment related problems.
... However, the effects on evaporating EOs on indoor air quality have been widely studied. It has been proven that EOs reduce airborne microbial levels but increase CO, carbone dioxide (CO2) and volatile organic compound (VOC) levels, which could be problematic for human health [60]. Another point to be considered is the production of secondary pollutants such as formaldehyde following a reaction between oxidants and terpenes, and secondary organic aerosols in ozone [61]. ...
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In recent years, the development of new bio-based products for biocontrol has been gaining importance as it contributes to reducing the use of synthetic herbicides in agriculture. Conventional herbicides (i.e., the ones with synthetic molecules) can lead to adverse effects such as human diseases (cancers, neurodegenerative diseases, reproductive perturbations, etc.) but also to disturbing the environment because of their drift in the air, transport throughout aquatic systems and persistence across different environments. The use of natural molecules seems to be a very good alternative for maintaining productive agriculture but without the negative side effects of synthetic herb-icides. In this context, essential oils and their components are increasingly studied in order to produce several categories of biopesticides thanks to their well-known biocidal activities. However, these molecules can also be potentially hazardous to humans and the environment. This article reviews the state of the literature and regulations with regard to the potential risks related to the use of essential oils as bioherbicides in agricultural and horticultural applications.
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Gas- and particle-phase molecular markers provide highly specific information about the sources and atmospheric processes that contribute to air pollution. In urban areas, major sources of pollution are changing as regulation selectively mitigates some pollution sources and climate change impacts the surrounding environment. In this study, a comprehensive thermal desorption aerosol gas chromatograph (cTAG) was used to measure volatile, intermediate-volatility and semivolatile molecular markers every other hour over a 10 d period from 11 to 21 April 2018 in suburban Livermore, California. Source apportionment via positive matrix factorization (PMF) was performed to identify major sources of pollution. The PMF analysis identified 13 components, including emissions from gasoline, consumer products, biomass burning, secondary oxidation, aged regional transport and several factors associated with single compounds or specific events with unique compositions. The gasoline factor had a distinct morning peak in concentration but lacked a corresponding evening peak, suggesting commute-related traffic emissions are dominated by cold starts in residential areas. More monoterpene and monoterpenoid mass was assigned to consumer product emissions than biogenic sources, underscoring the increasing importance of volatile chemical products to urban emissions. Daytime isoprene concentrations were controlled by biogenic sunlight- and temperature-dependent processes, mediated by strong midday mixing, but gasoline was found to be the dominant and likely only source of isoprene at night. Biomass burning markers indicated residential wood burning activity remained an important pollution source even in the springtime. This study demonstrates that specific high-time-resolution molecular marker measurements across a wide range of volatility enable more comprehensive pollution source profiles than a narrower volatility range would allow.
Article
Essential oils (EOs) seem to be more versatile and consist of a variety of volatile and organic biological active substances that are also employed as the better substitutes in the bacteria, fungal and various food sectors. Many researchers have done detailed research about the antibacterial property of essential oils and their respective inhabitants. While several pioneering works in the past have explained the mode of action of some compounds, an extensive understanding of most of the substances and their molecular mechanisms is still lacking. In particular, the bioactivity characteristics of EOs were evaluated by the main components found in these. These components were commonly utilized in the applications of bactericidal, fungicidal, medicinal and antioxidant drugs. The oils bioactivity can be contrasted with the behavior of pharmaceutical formulations which are produced synthetically. Consequently, essential oils are showing promise organic extracts that require further analysis in the nutrition or pharmaceutical companies for potential applications as supplements, additives or antibacterial. Because of their diverse activities like antifungal and antibacterial characteristics, essential oils may be utilized as alternate additives to improve the grain and seed shelf life. This review aims to provide a summary of existing information on the antibacterial and antifungal properties of EOs, their mechanism, and ingredients in identifying the areas of study that can promote the implementation in various bacterial and fungal properties.
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Essential oil products are increasingly used in indoor environments and have been found to negatively contribute to indoor air quality. Moreover, the chemicals and fragrances emitted by those products may affect the central nervous system and cognitive function. This study uses a double‐blind between‐subject design to investigate the cognitive impact of exposure to the emissions from essential oil used in an ultrasonic diffuser. In a simulated office environment where other environmental parameters were maintained constant, 34 female and 25 male university students were randomly allocated into four essential oil exposure scenarios. The first two scenarios contrast lemon oil to pure deionized water, while the latter two focus on different levels of particulate matter differentiated by HEPA filters with non‐scented grapeseed oil as the source. Cognitive function was assessed using a computer‐based battery consisting of five objective tests that involve reasoning, response inhabitation, memory, risk‐taking, and decision‐making. Results show that exposure to essential oil emissions caused shortened reaction time at the cost of significantly worse response inhabitation control and memory sensitivity, indicating potentially more impulsive decision‐making. The cognitive responses caused by scented lemon oil and non‐scented grapeseed oil were similar, as was the perception of odor pleasantness and intensity.
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Five aromatic constituents of essential oils (cineole, citral, geraniol, linalool and menthol) were tested for antimicrobial activity against eighteen bacteria (including Gram-positive cocci and rods, and Gram-negative rods) and twelve fungi (three yeast-like and nine filamentous). In terms of antibacterial activity linalool was the most effective and inhibited seventeen bacteria, followed by cineole, geraniol (each of which inhibited sixteen bacteria), menthol and citral aromatic compounds, which inhibited fifteen and fourteen bacteria, respectively. Against fungi the citral and geraniol oils were the most effective (inhibiting all twelve fungi), followed by linalool (inhibiting ten fungi), cineole and menthol (each of which inhibited seven fungi) compounds.
Article
The formation yields of acetone from the gas-phase reactions of the OH radical (in the presence of NO) and O3 with a series of monoterpenes have been measured at room temperature and atmospheric pressure of air. The acetone formation yields ranged from <2-3% for the OH radical reaction with limonene and the O3 reactions with limonene and α-phellandrene to 50% for the O3 reaction with terpinolene. Combining these acetone formation yields with literature estimates of emission rates of monoterpenes from vegetation leads to an estimate of acetone formation from the atmospheric photooxidation of monoterpenes of ∼10-11 Tg yr-1 globally, a significant fraction of the global acetone source strength of 40-60 Tg yr-1. Reaction mechanisms leading to acetone formation from these monoterpene reactions are discussed.
Article
Consumer products can emit significant quantities of terpenes, which can react with ozone (03). Resulting byproducts include compounds with low vapor pressures that contribute to the growth of secondary organic aerosols (SOAs). The focus of this study was to evaluate the potential for SOA growth, in the presence of O3, following the use of a lime-scented liquid air freshener, a pine-scented solid air, freshener, a lemon-scented general-purpose cleaner, a wood floor cleaner, and a perfume. Two chamber experiments were performed for each of these five terpene-containing agents, one at an elevated O3 concentration and the other at a lower O3 concentration. Particle number and mass concentrations increased and O 3 concentrations decreased during each experiment. Experiments with terpene-based air fresheners produced the highest increases in particle number and mass concentrations. The results of this study clearly demonstrate that homogeneous reactions between O3 and terpenes from various consumer products can lead to increases in fine particle mass concentrations when these products are used indoors. Particle increases can occur during periods of elevated outdoor O3 concentrations or indoor O3 generation, coupled with elevated terpene releases. Human exposure to fine particles can be reduced by minimizing indoor terpene concentrations or O 3 concentrations.
Article
Linalool [(CH3)2CCHCH2CH2C(CH3)(OH)CHCH2] is a terpene derivative emitted from vegetation, including orange blossoms and certain trees and vegetation in the Mediter ranean area. Linalool reacts rapidly in the gas phase in the troposphere with OH radicals, NO3 radicals, and O3, with a calculated lifetime due to these reactions of 1 h or less. The products of these gas-phase reactions have been studied in 6500−7900-L Teflon chambers using gas chro matography, in situ Fourier transform infrared absorption spectroscopy, and direct air sampling atmospheric pres sure ionization tandem mass spectrometry. The products identified and their formation yields are as follows: from the OH radical reaction, acetone, 0.505 ± 0.047; 6-methyl-5-hepten-2-one, 0.068 ± 0.006; 4-hydroxy-4-methyl-5-hexen-1-al (or its cyclized isomer), 0.46 ± 0.11; from the NO3 radical reaction, acetone, 0.225 ± 0.052; 4-hydroxy-4-methyl-5-hexen-1-al (or its cyclized isomer), 0.191 ± 0.051; and a non-quantified nitrooxycarbonyl; from the O3 reaction, acetone, 0.211 ± 0.024; 4-hydroxy-4-methyl-5-hexen-1-al (or its cyclized isomer), 0.85 ± 0.14; 5-ethenyldihydro-5-methyl-2(3H)-furanone, 0.126 ± 0.025; and HCHO, 0.36 ± 0.06. The formation routes to these products and the reaction mechanisms are discussed. Despite the complexity of linalool, a C10-hydroxydiene, the reaction products observed and quantified account for a significant fraction of the carbon reacted (especially for the OH radical and O3 reactions), with the carbon balances being 53 ± 8% for the OH radical reaction in the presence of NO, 20 ± 4% (plus the non-quantified, but anticipated to be major, nitrooxycarbonyl) for the NO3 radical reaction, and 78 ± 10% for the O3 reaction.
Article
Several gas-phase carbonyl products of two terpenes, beta-pinene and D-limonene, and of the sesquiterpene, trans-caryophyllene, have been identified and their concentrations measured in experiments involving the reaction of these unsaturated biogenic hydrocarbons with ozone in the dark. Cyclohexane was added as a scavenger for the hydroxyl radical to minimize interferences from OH, which forms as a product of the ozone-hydrocarbon reaction. Carbonyl products were formaldehyde (yield = 0.42) and nopinone (yield = 0.22) from beta-pinene, formaldehyde (yield = 0.10) and 4-acetyl-1-methylcyclohexene from D-limonene, and formaldehyde (yield 0.08) from trans-caryophyllene. The nature and yields of these products are discussed in terms of the ozone-olefin reaction mechanism. The ozone-beta-pinene reaction rate constant, measured in the presence of cyclohexane, is 12.2 +/- 1.3 x 10(-18) cm3 molecule-1 s-1 at 22 +/- 1-degrees-C. Carbonyl products have also been identified in exploratory experiments with trans-caryophyllene and NO in sunlight.
Article
The gas-phase carbonyl products of alpha-pinene, beta-pinene, and d-limonene have been identified and their concentrations measured in experiments involving sunlight irradiations of mixtures of terpene (1-2 ppm) and NO (0.25 ppm) in air. In turn, sunlight irradiations of carbonyl-NOx mixtures have been carried out for the major high molecular weight carbonyl products of beta-pinene (6,6-dimethylbicyclo[3.1.1]heptan-2-one) and d-limonene (4-acetyl-1-methylcyclohexene), and the corresponding carbonyl products have been identified. The nature and yields of these carbonyl products are discussed in terms of oxidation mechanisms involving the OH-terpene, ozone-terpene, OH-carbonyl, and ozone-carbonyl reactions.
Article
Lavender (Lavandula angustifolia, P. Miller) is used in aromatherapy as a holistic relaxant and is said to have carminative, antiflatulence and anticolic properties. Its sedative nature, on inhalation, has been shown both in animals and man. Lavender has a spasmolytic activity on guineapig ileum and rat uterus in vitro and it also decreases the tone in the skeletal muscle preparation of the phrenic nerve–diaphragm of rats. As the mechanism of action has not been studied previously, the spasmolytic activity was studied in vitro using a guinea-pig ileum smooth muscle preparation. The mechanism of action was postsynaptic and not atropine-like. The spasmolytic effect of lavender oil was most likely to be mediated through cAMP, and not through cGMP. The mode of action of linalool, one of lavender's major components, reflected that of the whole oil. The mode of action of lavender oil resembled that of geranium and peppermint oils. Copyright © 1999 John Wiley & Sons, Ltd.
Article
The airway irritation of (+)-α-pinene, ozone, mixtures thereof, and formaldehyde was evaluated by a mouse bioassay, in which sensory irritation, bronchoconstriction, and pulmonary irritation were measured. The effects are distinguished by analysis of the respiratory parameters. Significant sensory irritation (assessed from reduction of mean respiratory rate) was observed by dynamic exposure of the mice, over a period of 30 min, to a ca. 22 s old reaction mixture of ozone and (+)-α-pinene from a Teflon flow tube. The starting concentrations were 6 ppm and 80 ppm, respectively, which were diluted and let into the exposure chamber. About 10% ozone remained unreacted (0.4 ppm), <0.2 ppm formaldehyde, <0.4 ppm pinonaldehyde, <2 ppm formic acid, and <1 ppm acetic acid were formed. These concentrations, as well as that of the unreacted (+)-α-pinene (51 ppm), were below established no effect levels. The mean reduction of the respiratory rate (30%) was significantly different (p≪0.001) from clean air, as well as from exposure of (+)-α-pinene, ozone, and formaldehyde themselves at the concentrations measured. Addition of the effects of the measured residual reactants and products cannot explain the observed sensory irritation effect. This suggests that one or more strong airway irritants have been formed. Therefore, oxidation reactions of common naturally occurring unsaturated compounds (e.g., terpenes) may be relevant for indoor air quality.
Article
Many studies on essential oils and fragrance compounds are performed and then published without any biological testing whatsoever. In addition, the mechanisms of action of such compounds can remain unknown for years in many cases. The present paper gives more comprehensive knowledge on the actions of essential oils and fragrance compounds; in addition, the bioactivity of chiral, isomer and chemotype compounds is discussed. Copyright © 2004 John Wiley & Sons, Ltd.