High total volatile organic compounds pollution in a hospital dental department
Environ Monit Assess
High total volatile organic compounds pollution in a hospital dental department
Ming-Hui Liu 0 1 2 4 5 6
Tao-Hsin Tung 0 1 2 4 5 6
Fen-Fang Chung 0 1 2 4 5 6
Li-Chuan Chuang 0 1 2 4 5 6
Gwo-Hwa Wan 0 1 2 4 5 6
0 F.<F. Chung Department of Nursing, Chang Gung University of Science and Technology , Taoyuan, Taiwan , Republic of China
1 T.<H. Tung Department of Medical Research and Education, Cheng-Hsin General Hospital , Taipei, Taiwan , Republic of China
2 M.<H. Liu Department of Pediatric Dentistry, Taoyuan Chang Gung Memorial Hospital , Taoyuan, Taiwan , Republic of China
3 Department of Respiratory Therapy, Chang Gung University of Science and Technology , Chiayi, Taiwan , Republic of China
4 G.<H. Wan Department of Neurosurgery, Linkou Chang Gung Memorial Hospital , Taoyuan, Taiwan , Republic of China
5 G.<H. Wan Department of Respiratory Therapy, College of Medicine, Chang Gung University , Taoyuan, Taiwan , Republic of China
6 L.<C. Chuang Department of Pediatric Dentistry, Linkuo Chang Gung Memorial Hospital , Taoyuan, Taiwan , Republic of China
Bioaerosols produced by dental procedures may affect indoor air quality and cause infections in dental healthcare workers. To provide air quality data that can be used to protect dental healthcare workers, this study evaluated the air quality and its influencing factors in the dental department of the Chang Gung Memorial Hospital in Taiwan. The study was a crosssectional study design. Indoor air quality (IAQ) evaluations were conducted in six locations: pediatric dentistry, craniofacial orthodontic dentistry, periodontal dentistry, and general practice dentistry, instrument washing room, and patient waiting area. The measured air quality parameters included temperature, relative humidity, and concentrations of CO2, total volatile organic compounds (TVOCs), suspended particulate matter (PM), and bacteria. TVOCs concentrations at all six sampling stations were found to exceed the indoor air quality standards prescribed by the Taiwan Environmental Protection Agency. The highest concentrations of atmospheric PM10, PM2.5, and PM1 were found in the periodontal dentistry department, while the lowest concentrations occurred in the patient waiting area. The detection rate for Gram-positive bacteria was highest in the pediatric department (25%) and lowest in the instrument washing room (9%). Micrococcus luteus and Bacillus cereus were the primary pathogens detected. The dental departments of the hospital had a serious TVOCs pollution. The air quality of dental departments deserves long-term surveillance and attention.
Indoor air quality; Dental department; Particulate matter; Volatile organic compounds; Bacteria
Dental treatments include many diverse procedures, such
as restorative dentistry, root canal therapy, ultrasonic
scaling, periodontal curettage of dental calculus,
periodontal surgery, prosthetic dentistry, orthodontic treatment,
surgical extraction of impacted third molars, and dental
implant surgery. The use of high-speed drills or ultrasonic
scalers can produce aerosols. Microbial aerosols and
splatters are also generated during dental procedures. These
aerosols are air-suspended liquid or solid molecules that
contain bacteria, viruses, fungi, saliva, and blood.
Aerosols produced during dental procedures not only reduce
the IAQ, but also pose a threat to the health of dental staff
and are important sources of infection (
Bennett et al. 2000; Leggat et al. 2007).
IAQ assessment indicators include concentrations of
(Li et al. 2001; Scheff et al. 2000)
, PM, TVOCs,
bacteria (Liu et al. 2000), fungi, and viruses, as well as
temperature and relative humidity (RH). Particle
concentrations in the indoor air of a hospital are related to
human activity, air exchange, and air filtration
et al. 1989)
. High concentrations of aerosols can be
produced by a high-speed drill or rotating instrument
used inside an oral cavity (
Harrel and Molinari 2004
Kedjarune et al. 2000; Leggat and Kedjarune 2001). The
composition, concentration, and distribution of aerosols
is affected by factors such as the type of treatment
procedure, size and location of the treatment room,
duration of treatment, mode of treatment, patient
characteristics, and seasonality (Bennett et al. 2000;
Kedjarune et al. 2000; Grenier 1995).
In one study, closed and isolation dental clinic rooms
had high bacterial concentrations ((216 ± 75) CFU m−3
during scaling and (75 ± 22) CFU m−3 during fillings).
The bacterial concentration after 2 h of dental treatment
in the isolation dental treatment room was the same as
the background concentration of 12–14 CFU m−3
. In the same study, bacteria were
detectable in all areas of an open clinic with multiple dental
chairs. Peak bacterial concentrations were observed in
the main treatment area after 3 h of dental treatment (76–
114 CFU m−3), and the amount of bacteria in the
nontreatment area (42 CFU m−3) remained higher than the
background level. This shows that aerosols can spread
and move through the air
. All dental
procedures, and particularly dental surgery, are intended
to be performed in a sterile environment. The use of
protective measures, such as sterile gloves, gowns, and
face masks, is very important during these procedures.
The climate in Taiwan is characterized by high temperature and humidity, which are very conducive to the formation of bioaerosols. Patients, family members, and
healthcare workers are the main sources of biological
aerosols in hospitals. The close contact between patients
and medical staff, coupled with the central
airconditioning systems typically used in hospitals,
increases the probability of mutual infection. To date,
few studies have evaluated the IAQ of dental
departments in hospitals. The purpose of this study was to
investigate the air quality parameters and aerosol
distribution in six different locations of the dental
department: pediatric dentistry, craniofacial orthodontic
dentistry, periodontal dentistry, general practice dentistry,
instrument washing room, and patient waiting area.
Materials and methods
Permits for this study were obtained from the Taoyuan
Chang Gung Memorial Hospital in northern Taiwan.
This study evaluated the IAQ for the six locations of
the dental department, including pediatric dentistry
(PEDI), craniofacial orthodontic dentistry (ORTHO),
periodontal dentistry (PERIO), general practice
dentistry (GP), the instrument washing room (IR), and the
patient waiting area (PWA).
Figure 1 shows the six dental departments of the
selected hospital. The space volumes of PEDI, PERIO,
IR, ORTHO, GP, and PWA were 26.51, 39.22, 31.05,
96.59, 232.03, and 78.62 m3, respectively. During the
sampling period, indoor air was conditioned but not
Air quality monitoring
This study was performed from July to August in 2016.
Indoor air quality parameters of six locations in the
dental department were monitored for 9 h (8 am to 5
pm) per day for 3 days. Bacterial samples were collected
twice a day (in the morning and in the afternoon) for
3 days. The air sampling instruments were placed ap
proximately 1.5 m from the dental unit to avoid
interrupting dental treatment, and as close to the center
of the sampling area as possible. All instruments were
positioned 1 m above the floor to simulate the seated
breathing zone of healthcare workers.
The evaluated air quality indices included the air tem
perature, RH, and concentrations of TVOCs, CO2,
suspended PM, and bacteria. The air temperature, RH,
and CO2 concentration were determined every minute
using a digital psychrometer (TSI, Inc., Shoreview, MN,
USA). The PM levels were measured every 6 s using a
portable dust monitor with 31 size channels measured the
size range between 0.25 and 32 μm (Model 1.110;
Grimm Labortechnik Ltd., Ainring, Germany). The level
of TVOCs was determined every minute by a hand
carried detector (ppb RAE 30000, USA). Bacterial
concentrations were assessed using Andersen one-stage
viable impactors (N6; Andersen Samplers, Atlanta, Georgia)
with 20 mL of tryptic soy agar at an airflow rate of
28.3 L min−1 for 3 min. Duplicate bacterial samples were
collected to ensure sampling accuracy, and bacterial
samples were incubated at 30 ± 1 °C for 48 ± 2 h, as
recommended by the Taiwan Environmental Protection
Agency (TEPA). The positive hole conversion table and
sampled air volume were used to calculate the number of
colony forming units per volume of air (CFU m−3). All
the bacterial colonies were identified biochemically.
Data were analyzed using SPSS version 21.0 (IBM
Corp., Armonk, NY, USA). All figures were constructed
with GraphPad Prism version 6.0 (GraphPad Software,
San Diego, CA, USA). The two-sided p value with
α < 0.05 was considered statistically significant. Besides
the bacterial concentration, the hourly data of air quality
indices were used for statistical analysis in the study. The
PM was classified as PM10 (aerodynamic diame
ter ≤ 10 μm), PM2.5 (aerodynamic diameter ≤ 2.5 μm),
and PM1 (aerodynamic diameter ≤ 1 μm). The IAQ
indices in the six locations of the dental department in
the hospital were compared using the one-way analysis
of variance test with Scheffe’s post hoc comparison or
Kruskal-Wallis test for continuous variables. Pearson correlation analysis was applied to identify the relationship between combinations of two continuous variables with normally distributed data.
During the study period, the largest and smallest
numbers of people were observed in ORTHO (N = 105) and
in PERIO (N = 66), respectively. Air quality data
collected from the six locations of the dental department
(n = 156) is shown in Table 1. The highest temperature
was recorded in PEDI (24.5 °C), while the lowest was
recorded in ORTHO (20.43 °C). The temperature
differences in the six locations are statistically significant
(p < 0.001). The IR had the highest RH value (70.59%),
,trr°eaepuCm ,% ,ppm2 ,sppbCO 3−,gmμ01 3−,gmμ.52 3−,gmμ1 ,tireaacgmμ
舃eT 舃RH 舃CO 舃TV 舃PM 舃PM 舃PM 舃B
while PERIO had the lowest RH value (58.11%).
Differences in the RH values in the six locations were
statistically significant (p < 0.001). The measured CO2
concentrations in six regions ranged from 491.73 to
653.65 ppm, with the maximum occurring in PERIO
and the minimum occurring in IR. A significant
difference (p < 0.001) was found in the CO2 concentrations
for the six locations, but all values were within the
TEPA indoor air quality standard of 1000 ppm.
The average TVOCs concentrations found in the six
sampling locations all exceeded TEPA indoor air quality
standards of 560 ppb h−1. The highest concentration
occurred in GP (1373.99 ppb) and the lowest occurred
in the IR (674.56 ppb). The TVOC concentrations in the
six locations were significantly different (p < 0.001).
The maximum concentrations of PM10, PM2.5, and
PM1 were found in PERIO, while the minimum concen
trations were found in the PWA. Concentrations of
PM10, PM2.5, and PM1 had statistically significant dif
ferences between the six sampling locations (p < 0.001).
However, none of the values exceeded the TEPA stan
dard. The upper limit for the PM10 concentration was
75 μg m−3 for 24-h average concentration, while that for
PM2.5 was 35 μg m−3 for 24-h average concentration.
The median concentrations of airborne bacteria in
PERIO (773.01 CFU m−3), GP (307.56 CFU m−3), IR
(619.63 CFU m−3), and PWA (1299.25 CFU m−3) were
s i g n i f i c a n t l y h i g h e r t h a n t h o s e i n O RT H O
(84.48 CFU m−3) and PEDI (247.97 CFU m−3). Also, a
significant difference in the airborne bacterial
concentration was found between PWA and IR (p = 0.025). In this
study, the bacterial concentrations were generally lower
than the TEPA indoor air quality standards, which sets an
upper limit of 1500 CFU m−3. Only two specimens
exceeded the 1500 CFU m−3 standard, both during
afternoon sessions, one in GP (4058.67 CFU m−3) and one in
the PWA (2551.39 CFU m−3) (data not shown). In the
morning and afternoon sessions in PEDI and ORTHO,
bacterial concentrations were below 500 CFU m−3.
Temperature had a significant negative correlation
with RH (r = − 0.463, p < 0.01) and TVOCs
(r = − 0.16, p < 0.05), while RH had a significant negative
correlation with CO2 (r = − 0.550, p < 0.01) and TVOC
(r = − 0.172, p < 0.05) concentrations (Table 2). In
addition, CO2 concentration was positively correlated
with the concentration of TVOCs (r = 0.377, p < 0.01),
PM10 (r = 0.28, p < 0.01), and PM2.5 (r = 0.16, p < 0.05).
PM10 had significant positive correlations with PM2.5
(r = 0. 827, p < 0.01) and PM1 (r = 0. 739, p < 0.01).
(舃9) Number of people
The types and isolation rates of bacteria in the six
dental departments are listed in Table 3. The total
airborne bacteria species include both Gram-positive and
Gram-negative bacteria. Most of the bacteria were
Gram-positive species (94%). The proportion of Grampositive bacteria was largest in PEDI (25%) and smallest in the IR (9%). The Gram-positive bacteria included
Micrococcus luteus (31%), Bacillus cereus (22%),
Bacillus circulans (9%), other Bacillus spp. (6%),
Micrococcus lylae (6%), other Micrococcus spp. (6%),
Achromobacter spp. (3%), Bacillus licheniformis (3%),
Staphylococcus haemolyticus (3%), and Staphylococcus
kloosii (3%). Gram-negative bacteria, which included
Brevundimonas diminuta and Nocardia spp., were only
found in GP and represented a mere 6% of the
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PEDI pediatric dentistry, ORTHO craniofacial orthodontic dentistry, PERIO periodontal dentistry, GP general practice dentistry, IR
instrument washing room, PWR patient waiting area
✝ The number of specific isolated microorganism divided by the total number of isolated microorganisms
Hospital indoor air pollution is associated with
inadequate building environments, including building
materials, air-conditioning systems, and ventilation rates, and
with human factors, such as overcrowding in
constrained spaces. This was the first study in Taiwan
evaluating air quality indices for a dental department in
Dentists face potential exposure to various air
pollutants during different types of dental procedures. Studies
have shown that dental workers have a higher chance of
exposure to microbes and, consequently, a higher risk of
respiratory infections, inflammation, and disease than
do other workers
(Bennett et al. 2000)
. In addition, skin
irritation and eye infections are often a health hazard for
(Leggat et al. 2007)
. The distance between
the dentist and the patient, the location of the patient,
and the patient head height during dental treatment also
affected the distribution and concentration of aerosols.
Studies have shown that the central location of a
dentist’s face (including the eyes and nasal region) are at
high-risk for infection
(Nejatidanesh et al. 2013)
rubber barriers used in mouth during patient treatment
can effectively reduce aerosol concentrations
et al. 2008; Al-Amad et al. 2016; Tag and El-Hady
, while patients using antibacterial mouthwash
before dental treatment also proved to decrease
aerosolized bacterial production effectively (
Fine et al. 1992
Molinari and Molinari 1992; Fine et al. 1993).
In our study, the TVOCs concentrations of the six
sampling locations exceeded the TEPA indoor air
quality standard, and the highest TVOCs concentration was
found in GP. Resin materials are often used for
temporary prosthetics and relining removable dentures in this
department. One of the main components of resin
monomer is methyl methacrylate, which has a strong acrid
smell and volatile character. The resin monomer spreads
through the air following polymerization and
incomplete setting. This monomer is the main source of
volatile organic compounds in GP, which has an open area
floor plan with five dentists working simultaneously.
The partial pressure of resin monomer vapor is thus very
high from the volatile gas accumulation in this location.
The second highest value of TVOCs was recorded in
PERIO, which is a closed treatment room. Common treatments here include ultrasonic scaling, periodontal surgery, and dental implant surgery, none of which include volatile materials. However, 3 days a week,
there are four prosthetic dentists who treat patients in
this department. They often use resin monomers to
make temporary prosthetics and adjust dentures. The
volatile gas therefore spreads through the
airconditioning system. In addition, every Wednesday
afternoon, the nurses use bleaching solvent to disinfect the
boxes used for collecting surgery devices, and they
throw away the bleach the following day. We speculate
that the resin monomer and the bleaching solvent both
contributed to PERIO having the second highest
concentration of TVOCs. In ORTHO, the dentists also use
resin materials to reline newborn cleft palates. In
addition, orthodontic and pediatric dentists often use
resinbased adhesive materials and bonding agents, which
have volatile properties. The lowest concentration of
TVOCs occurred in the IR because only enzyme powder
is used to soak and clean all instruments, so no volatile
material sources were found in this location.
In order to prevent the formation of TVOCs in dental
departments, high-power ventilation can be used along
with a high-density charcoal filter system near the
dentistry procedure locations. A method for preventing high
TVOC concentrations during dental treatment is still
needed. One suggestion is that all dentists should close
the button of resin monomer immediately after using it.
The correct powder to liquid ratio would also help
prevent unnecessary emissions. High values of TVOCs
are harmful to the working staff and patients. Hospitals
need to focus more on improving the air quality in their
dental departments. Additionally, CO2 levels are closely
related to TVOC, PM10, and PM2.5 concentrations. With
a better ventilation system, the CO2 level is decreased,
and the volatile solvents and aerosols would be more
effectively flushed and filtered out.
Dental scaling can produce high concentrations of
aerosols, which can be removed using high-intensity
Barnes et al. 1998
Harrel et al. 1996
Harrel et al. 1998). High-intensity suction is thus a good
way to reduce the risk of exposure to microbes.
Bioaerosols collected in the dental locations included
Streptococcus mutans and Streptococcus sanguinis
bacteria, mainly from the patient mouths (Earnest and
Loesche 1991), as well as fungi from the environment
(Krogulski and Szczotko 2010)
. Adding a fluorescent
agent to the water column of a high-speed drill would
indicate when splashing has occurred on the head, upper
arm, neck, or chest of the dentist, which is a problem
especially when treating the lower right molar area.
Most of the sputtering landed on the patient chest
(Bentley et al. 1994)
. In this study, we found bacterial
counts as high as 4000 CFU m−3 in GP one afternoon.
Because the number of patients that day was up to 20
people simultaneously, the airborne bacterial level was
particularly high. For each afternoon session in the
PWA, a higher bacterial concentration was noted, pos
sibly because more patients and families were present.
During afternoon sessions in PEDI and ORTHO, bacte
rial concentrations were all below 500 CFU m−3. We
infer that this was because of a lower number of patients
on weekdays. There were many airborne bacterial
species in PEDI and ORTHO, due to the larger number of
people and children present.
In conclusion, serious TVOCs pollution was found in
the dental departments of the hospital. The air quality of
dental departments deserves attention and requires
longterm surveillance from environmental safety and health
departments in hospitals to protect patients as well as
dentists and other nursing workers. The distributions of
air pollutant concentrations during common dental
treatment procedures should be evaluated in a future study.
Acknowledgements The authors thank Chang Gung Memorial
Hospital in Taiwan for financially supporting this research under contract nos. BMRP441 and CMRPG5F0171.
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of interest.
Abbreviations TVOCs, total volatile organic compounds; PM,
suspended particulate matter; RH, relative humidity; PEDI,
pediatric dentistry; ORTHO, craniofacial orthodontic dentistry;
PERIO, periodontal dentistry; GP, general practice dentistry; IR,
instrument washing room; PWA, patient waiting area; TEPA,
Taiwan Environmental Protection Agency
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