International Journal ofEnvironmental Researchand Public Health
ArticleIndoor Air Quality Analysis of Newly Built Houses
Norimichi Suzuki 1, * , Hiroko Nakaoka 1 , Masamichi Hanazato 1 , Yoshitake Nakayama 1 ,Kayo Tsumura 1 , Kazunari Takaya 2 , Emiko Todaka 1 and Chisato Mori 1,3
1

2
3

*

Center for Preventive Medical Sciences, Chiba University, 6-2-1 Kashiwanoha, Kashiwa,
Chiba 277-0882, Japan; hnakaoka@faculty.chiba-u.jp (H.N.); hanazato@chiba-u.jp (M.H.);
seiken@chiba-u.jp (Y.N.); tsumu-kayo@chiba-u.jp (K.T.); todakae@faculty.chiba-u.jp (E.T.);
cmori@faculty.chiba-u.jp (C.M.)
National Institute of Occupational Safety and Health, 6-21-1 Nagao, Tama-ku, Kawasaki,
214-8585, Japan; takaya-k@h.jniosh.johas.go.jp
Center for Preventive Medical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba-shi,
Graduate School of Medicine, Chiba University, Chiba 260-8672, Japan
Correspondence: suzu-nori@chiba-u.jp; Tel.: +81-4-7137-8200; Fax: +81-4-7137-8180

Received: 30 August 2019; Accepted: 24 October 2019; Published: 28 October 2019


Abstract: Recently, people have become increasingly aware of potential health issues related to indoor
environments. In this study, we measure the concentrations of various volatile organic compounds,
carbonyl compounds, and semi-volatile organic compounds, as well as the ventilation rates, in 49 newhouses with light-gauge steel structures one week after completion. The proper indoor air quality of
new residential environments can be ensured by characterizing people’s exposure to certain chemicals
and assessing future risks. Our results show that the concentrations of the measured compounds
were lower than the guideline values set by the Ministry of Health, Labour and Welfare of Japan,
and would continue to decrease. However, we observed that unregulated compounds, assumed to be
substitutes for regulated solvents, contributed substantially to the total volatile organic compounds.
To reduce indoor chemical exposure risks, the concentrations of these unregulated compounds should
also be minimized. In addition, their sources need to be identified, and manufacture and use must be
monitored. We believe it is important to select low-emission building materials for reducing residents’
exposure to indoor chemicals.
Keywords: indoor air quality; volatile organic compounds; total volatile organic compounds; newly
built houses; sick building syndrome

1. Introduction
Indoor air quality (IAQ) can have a significant impact on human health. Recently, there has been
increasing concern regarding the adverse health effects of various chemicals released by construction
materials and household items into indoor environments [1–4]. According to the previous studies,indoor air pollutants and microbiological contaminants pose public health risks [5–8]. Therefore, for the
public’s safety, we should attempt to minimize their concentrations. They are suspected to be caused
by volatile organic compounds (VOCs) emitted by building materials and other sources in newly built
or refurbished houses.
Recent technological progress toward reducing household energy consumption has led to increased
demand for highly airtight and insulated homes. However, making homes more airtight and heavily
insulated have increased the likelihood of chemical compounds being retained indoors, resulting inincreased air contamination [9,10]. Various chemical compounds are emitted into rooms by a wide rangeof sources, including building and internal materials, furniture, curtains, air fresheners, deodorants,
pesticides, personal care products, cooking, and other everyday household products.
Int. J. Environ. Res. Public Health 2019, 16, 4142; doi:10.3390/ijerph16214142

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In particular, building materials and adhesives are important sources of VOC emissions,particularly in newly built houses [11,12]. It has been reported that current new-build houses havehigh concentrations of various VOCs emitted by building materials and products [13–15]. There has
thus been increasing interest in changing new house designs and selecting suitable building materials.
The European Union has published a list of substances and their associated emission limits, namely theEuropean Union–Lowest Concentration of Interest (EU–LCI) values [16]. This gives the reference
VOC concentrations.
European countries harmonize these values, but Japan currently does not provide labels orconcentration limits based on the emissions from building materials. The only exception is materials
containing formaldehyde, which are regulated by the revised Building Standard Law developed by
the Japanese Ministry of Land, Infrastructure, Transport and Tourism (MLIT). In addition, in Japan,
newly built houses are often delivered to clients immediately after completion. There is thus a risk that
consumers will be exposed to high chemical concentrations if the indoor air of their newly built houses
is contaminated, since new-build houses have high concentrations of various VOCs emitted by building
materials and products [11,12]. In our previous study [17], we assessed IAQ by measuring the levels of
five compounds (styrene, formaldehyde, ethylbenzene, toluene, and xylene) for which the MLIT’s
Housing Quality Assurance Act sets out guideline values, as well as the total amount of VOCs (TVOC).
Our results showed that it is possible to achieve good IAQ with low VOC concentrations, much lower
than the Act’s guideline values, even just after construction is completed by using low-emission
materials and maintaining ventilation rates of more than 0.5 air changes per hour, as required by
Japanese law.
In this study, we collaborated with a house builder to focus on building houses with better IAQ.
They attempt to build houses using materials that have low chemical compound emissions (based onemission rates calculated in small chamber method) and sell them as air-quality-conscious houses.
To evaluate whether selecting low-emission materials and building products is an effective way to
improve IAQ, we collected and analyzed air samples after the construction of these air-quality-conscious
houses was complete but prior to occupancy.
We measured the concentrations of 55 VOCs, 14 carbonyl compounds (aldehydes and ketones),and 22 semi-volatile organic compounds (SVOCs) in 49 newly built houses soon after construction
was complete (i.e., within a week). Then, we compared these results with the 13 guideline values
and the interim TVOC target value set by the Ministry of Health, Labour and Welfare of Japan(MHLW) to assess the associated indoor air contamination risks. We also compared this data withthe results of other studies and measured several environmental parameters, namely the ventilation
rate, temperature, and relative humidity. The aim of this study is to investigate whether selecting andusing low-emission construction materials can help to create low levels of VOCs with fewer chemicals,even just after completion.
2. Materials and Methods
2.1. House Characteristics
The houses considered in this study were built in Japan’s Chiba Prefecture by a construction
company. We selected 89 houses from among those built between May 2014 and November 2015.
Shortly after the houses were completed (immediately after the last finish nailing), we obtained
permission from the houses’ owners to measure the levels of VOCs, carbonyl compounds, and SVOCs
in the indoor air. A total of 49 owners gave their consent to conduct this study, and we used thesehouses as test sites.
The houses were constructed using light-gage steel with an average of 2.4 floors, and the mean
living room and bedroom areas were 30.86 and 13.48 m2 , respectively. The rooms were flooredin laminate wood and the walls were either wallpapered using starch adhesives or painted using
water-based paint. All the initial measurements were made while the rooms were devoid of furniture.

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3 of 112.2. Indoor Air Sampling and Analysis
All measurements were performed according to “The standard methods of air sampling andmeasurement,” issued by the MHLW of Japan [18]. Before sampling the air, all the windows and doors
were left open for more than 30 min for ventilation and were subsequently closed for more than 5 h.
Then, air samples were collected from two rooms in the houses (living rooms and bedrooms) via active
sampling for 60 min while their ventilation systems were operating, but with their air conditioning
systems switched off. Simultaneously, several environmental factors were measured, namely thetemperature, humidity, and ventilation rate. In Japan, the Building Standard Law stipulates mechanicalventilation equipment for all buildings and ventilation rate of 0.5 air changes per hour or more in
residential rooms. The proposed study considers it as sufficient to measure one location per house for
confirmation. Outdoor air samples were also collected every time at a point near each house under theeaves. Based on these samples, the levels of 55 VOCs, 14 carbonyl compounds, and 22 SVOCs wereidentified and quantified (Tables S1–S3 in the Supplementary Materials).
2.3. VOCs
Adsorbent tubes made of Tenax-TA® (a porous polymer resin based on 2.6-diphenylene oxide)
were obtained from Sigma-Aldrich (St. Louis, Missouri, USA) and used to actively sample the VOCs.
Air samples were collected by pumping air through the tubes at a flow rate of 100 mL/min for 30 min,then analyzed using an Agilent 7890 B gas chromatograph (Agilent Technologies Inc., Tokyo, Japan)
equipped with an MSD 5977A quadrupole mass spectrometer and a TurboMatrix ATD 650 TD unit
(PerkinElmer Japan Co. Ltd., Tokyo, Japan). Next, thermal desorption measurements were carriedout by heating the Tenax-TA for 10 min at 280 ◦ C. Here, the split ratio was 20:1 and the transfer-line
temperature was 230 ◦ C.
Next, DB-1 columns (30 m × 0.25 mm; i.d.: 1.0 µm; Agilent Technologies Inc.) were used toseparate the samples at 35 ◦ C for 5 min, before the columns were heated to 240 ◦ C at a rate of
10 ◦ C/min. Helium (more than 99.9999% pure) was used as the gas chromatography (GC) carriergas, flowing into the columns at a rate of 1.0 mL min−1 . The VOCs were identified and quantified inscan mode at mass-to-charge (m/z) ratios in the 40–350 range. The concentrations of 55 compounds
were calculated based on their individual response factors. Calibration was accomplished using two
different concentrations, i.e., 5–50 ppm, and linear responses were obtained. Finally, the TVOC was
calculated by summing the amounts of all the VOCs, carbonyl compounds, and SVOCs.
2.4. Carbonyl Compounds
First, 2,4-dinitrophenylhydrazine (DNPH) active gas tubes (designed for aldehydes and ketones;
Shibata Scientific Technology Ltd., Saitama, Japan) were used to calibrate the carbonyl compound
measurements. The samples were collected over 30 min with a pump flow rate of 1.0 L/min, and thenthe gas tubes were eluted at a flow rate of 2–5 mL/min using a 10-mL syringe filled with acetonitrile.
High-performance liquid chromatography analyses were conducted with 5.0 mL samples, using aprominence UFLC from Shimadzu Corporation (Kyoto, Japan) equipped with 2 LC-20AD liquid feedpumps, a SIL-20AC auto-sampler, and an SPD M20A photodiode array detector. Ascentis RP-Amide
columns (150 mm × 4.6 mm; i.d.: 2.7 µm; Sigma-Aldrich) were used for separation, the column oventemperature was 40 ◦ C, and the injection volume was 10 µL. The mobile phases were acetonitrile/water
solutions with ratios of 40:60 (Solution A) and 80:20 (Solution B). The column flow rate was 1.0 mL/min,using 100% of Solution A for the first 30 min, followed by 75% of Solution A and 25% of Solution B
for 55 min, and finally 100% of Solution B for 5 min. The concentrations of all the compounds were
calculated using the corresponding standards. Calibration was accomplished with a concentration of
1 ppm.

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4 of 112.5. SVOCs
To calibrate the SVOC measurements, 47-mm Empore C-18 FF Disks (3M Japan Ltd. Two Harbors,
Minnesota, USA) in an EMO holder (GL Sciences, Inc., Tokyo, Japan) were preconditioned with acetone.
The samples were collected over 120 min with a pump flow rate of 10 L/min, then the filters weretransferred to 10-mL stoppered test tubes, to which 7 mL of acetone and 1 µL of a 100-µg/mL internal
standard solution (acenaphthene-d10) were added. After 5 min of ultrasonic extraction, the samples
were centrifuged for a further 5 min at 2500 rpm. Then, the supernatants were transferred to different
test tubes and concentrated to 1.0 mL under a nitrogen stream (60 ◦ C), before their contents wereanalyzed via GC/mass spectrometry using an MSD 5977A quadrupole mass spectrometer equippedwith an Agilent 7890 B gas chromatograph and a 7693 auto-sampler (Agilent Technologies Inc.,
Santa Clara, California, USA). A DB-1 column (30 m × 0.25 mm; i.d.: 1.0 µm; Agilent Technologies Inc.)was used for separation, and its temperature was increased from 60 ◦ C to 280 ◦ C at a rate of 12 ◦ C/min,
maintaining the final temperature for 10 min. The injector temperature was 280 ◦ C and 1.0 µL volumes
were injected in splitless mode. Helium (more than 99.9999% pure) was used as the carrier gas, with aflow rate of 1.0 mL/min. The analysis was performed in SIM mode. The concentrations of all thecompounds were calculated using the corresponding standards. Calibration was accomplished using
two different concentrations, 1–100 ppb and linear responses were obtained.
2.6. Ventilation Rate
The ventilation rates in the living rooms were calculated using the concentration attenuation
method with a tracer gas (CO2 ). Dry ice was placed indoors and stirred using a turbo circulator.
After confirming that the CO2 concentration was stable with a CO2 densitometer (TES-1370, Satoshoji
Digital, Kanagawa, Japan), the maximum value was recorded and the concentration measured at
one-minute intervals as it gradually decreased over a period of 60 min. Based on the initial (maximum)
value, the ventilation rate V was calculated according to the formula given in the “Standard Methodsof Analysis for Hygienic Chemists” ([19]):
V = 2.303 × VR/t × log {(C1 − C0 ) / (Ct − C0 )}(1)

where VR is the room volume (m3 ), t is the duration of the mechanical ventilation’s operation, Ct is thetracer gas concentration (µg/m3 or mL/m3 ) at time t, C1 is the initial tracer gas concentration (µg/m3 or
mL/m3 ), and C0 is the outdoor tracer gas concentration (µg/m3 or mL/m3 ).
3. Results
3.1. Indoor Environment Characteristics
Table 1 lists the mean, median, maximum, and minimum ventilation rates together with thetemperatures and relative humidity levels for the indoor environments. The temperature varied from
7.3 ◦ C to 31.3 ◦ C in the living rooms and from 8.0 ◦ C to 33.2 ◦ C in bedrooms, whereas the relative
humidity varied from 24.6% to 82.2% in the living rooms and 24.4% to 77.5% in bedrooms. Notably,
the living room ventilation rates ranged from 0.5–2.3 per hour, meaning that all the tested rooms
exceeded the standard (0.5 air changes per hour) specified in the amended Building Standard Law set
by the MLIT of Japan [20].

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Table 1. Indoor environments.
Living Room

Bedroommean

SD (±)

median

max

min

mean

SD (±)

medianmax

minTemp (◦ C)

24.1

4.5

24.0

31.3

7.3

25.5

4.4

25.6

33.2

8.0

Relative humidity (%)
Ventilation rates (per hour)

62.7
1.0

10.4
0.4

64.6
0.9

82.2
2.3

24.6
0.5

58.4
-

10.3
-

60.4
-

77.5
-

24.4
-

-: Not measured.

3.2. Chemical Compound Concentrations
The MHLW of Japan has set non-binding guideline limits on the concentrations of 13 chemicals,
as well as an interim TVOC target of 400 µg/m3 . Table 2 shows limits of quantitation (LoQs),
and guideline values for these 13 compounds. In this study, we measured the levels of these compounds
and compared them with the guideline values. Table 2 also shows the mean, median, maximum,and minimum concentrations, together with the frequencies with which they were detected in thetest houses and the TVOC. In all cases, the concentrations of these 13 compounds were below therecommended limits. Of the 13 compounds, the three most abundant were acetaldehyde, toluene,
and formaldehyde, whose mean (±SD) living room concentrations were 24 ± 10, 12 ± 11 and
15 ± 6.5 µg/m3 , respectively. These three compounds were also detected in all the bedrooms. The mean
outdoor TVOC level was 85.0 µg/m3 and was always low regardless of temperature and humidity.

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Table 2. Concentrations and frequencies of 13 regulated compounds and the TVOC, including a comparison with the maximum values recommended by the MHLW
of Japan.
Living Room

Bedroom

LOQ (b)Guideline Values (c)Mean (±SD)

MedianMax

Min

Frequency

Mean (±SD)

MedianMax

Min

Frequency

Compounds (a)(µg/m3 )(µg/m3 )

µg/m3

µg/m3

µg/m3

µg/m3

%

µg/m3

µg/m3

µg/m3

µg/m3

%

TolueneEthylbenzene
XyleneStyrenep-Dichlorobenzene
Tetradecane
Formaldehyde
Acetaldehyde
Fenobucarb
DiazinonDibutyl phthalate
Chlorpyrifos
Bis(2-ethylhexyl) phthalate

1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.001
0.001
0.07
0.001
0.15

200
3800
870
220
240
330
100
48
33
0.29
220
1.0
120

12 (11)7 (8.6)5 (5.9)6 (7.2)<1.0
3 (1.9)15 (6.5)
24 (10)<0.001 (e)<0.0010.1 (0.1)<0.0010.1 (0.1)

8
5
4
3
<1.0
2
13
20
<0.001<0.001
0.1<0.0010.1 (0.1)

64
60
35
34
5.0
10
35
47
<0.001<0.001
0.6<0.0010.4

2<1.0 (d)
<1.0
<1.0
<1.0
<1.0
3
6
<0.001<0.001<0.07 (f)<0.001<0.15 (g)

98
98
98
98
27
84
100
100
0.0
0.0
96
0.0
98

10 (8.5)
7 (7.3)6 (5.7)3 (4.8)<1.0
3 (2.7)14 (6.4)
20 (10)<0.001<0.0010.1 (0.2)<0.0010.2 (0.2)

8
4
4
2
<1.0
3
13
16
<0.001<0.001
0.1<0.001
0.1

46
31
22
27
4.3
15
32
46
<0.001<0.001
1<0.001
0.7

2
<1.0
<1.0
<1.0
<1.0
<1.0
4
5
<0.001<0.001<0.07<0.001
<0.15

100
98
98
69
29
84
100
100
0.0
0.0
96
0.0
98

389 (112)

390

602

139

390 (123)

396

654

146

TVOC (h)(a) All the compounds were calculated by individual response factor; (b) LOQ: limit of quantitation; (c) The MHLW of Japan set non-binding guideline values for 13 chemicals (six VOCs,
two aldehydes and five SVOCs); (d), (e), (f), (g) < LOQ; (h) TVOC: Total concentration of 55 VOCs, 14 carbonyl compounds, and 22 SVOCs

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4. Discussion
In this study, we investigated the IAQ of newly built houses in terms of the concentrations of
55 VOCs, 14 carbonyl compounds, and 22 SVOCs, via active sampling. The VOC measurementsof outdoor air were conducted at the same time as those in indoor air; however, the concentrationlevels of outdoor air were always very low. Indoor air is strongly affected by outside air, but theresults led us to assume that indoor air pollutants had been emitted from indoor materials. Here,
we focused purely on the effects of building materials on air quality, excluding furniture and otherhousehold items. We measured the concentrations of a variety of chemical compounds in 49 houses
immediately after construction was complete (i.e., within a week). At this time, the concentrationsof the 13 compounds for which the MHLW of Japan has set guidelines were generally at a tenthof the guideline levels or below. However, the TVOC of several samples exceeded the provisionaltarget of 400 µg/m3 . We believe this was because these measurements were conducted in summer
and the maximum temperature was very high (31.3–33.2 ◦ C). In addition, they were performed lessthan a week after completion, within one to three days. The relation between the temperature andconcentration levels of TVOC was calculated with Spearman’s rank correlation coefficient. There was aslight positive correlation (r = 0.390 and p = 0.006 for the living rooms and r = 0.298 and p = 0.042 forthe bedrooms). There were several samples in which the TVOC levels exceeded the provisional target
value of 400 µg/m3 . We have assumed that this excess value can be attributed to these measurements
being conducted during the summer when the maximum temperature was very high (31.3–33.2 ◦ C).
However, almost all concentration levels of TVOC (Table 2) could be kept low with a mean of 389 µg/m3
and median of 390 µg/m3 in the living rooms and those in the bedrooms can be kept as 389 and390 µg/m3 , respectively, even when the room temperatures were high.
In addition, we compared the values for the 13 VOCs and the TVOC obtained in this study
with the results of other studies, by Park and Ikeda [21], Järnström et al. [13], Shin and Jo [22],Noguchi et al. [23], and Onuki et al. [14], that were conducted on newly built, less than a year old,or unoccupied dwellings (Table 3). Note that the 13 compounds considered here include some SVOCs,
which must be sampled and analyzed separately, and this SVOC data was not provided by the otherstudies. This comparison shows that almost all the VOC and TVOC values seen in this study are
lower than those of the other studies. It was difficult to implement conditions, such as measurement
procedures, apparatuses, and temperatures, which were similar to those of other studies. Therefore,
our comparison may lack accuracy, which would be a limitation of this study. However, we did try to
make our conditions, such as higher temperatures and shorter times before measurements, severer thanthose of the other studies.
Onuki et al. investigated the IAQ of houses built in Japan between 2007 and 2009, within six
months of their completion [14]. They found that the maximum concentrations of some compounds
exceeded the guideline values, and were much higher than the values observed in our study. In addition,
Noguchi et al. measured the IAQ of a daycare center just after completion [23]. Although they foundthat the ventilation system was effective for reducing VOC levels, their data showed much higher
concentrations just after completion than we observed.
In addition, our previous study showed that the chemical concentrations in seven houses in thesame development considered in this study decreased substantially after one month [17], so we expectthat the VOC levels in the houses examined here would also have reduced further after a month.
According to the development company that collaborated with us, their newly built houses are only
delivered to owners after the following steps are complete: building completion; internal inspection;
an owner check; repair work; and final delivery. This normally takes 3–4 weeks, so the IAQ of thesehouses poses a sufficiently low chemical exposure risk at the time of delivery.

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Table 3. Comparison of concentrations of 13 VOCs and TVOC in indoor which have been set by MHLW.
Our study (2015)
Compounds (a)Mean (±SD)

Park et al. (2006)

Jarnstrom et al. (2006)

Shin et al. (2012)

Noguchi et al. (2016)

Onuki et al. (2009)

Mean (±SD)

Mean (±SD)

Mean (±SD)

Mean (±SD)

MedianLiving room

Bedroom

TolueneEthylbenzene
XyleneStyrenep-Dichlorobenzene
Tetradecane
Formaldehyde
Acetaldehyde
Fenobucarb
DiazinonDibutyl phthalate
Chlorpyrifos
Bis(2-ethylhexyl) phthalate

12 (11)7 (8.6)5 (5.9)6 (7.2)<1.0
3 (1.9)15 (6.5)
24 (10)<0.001<0.0010.1 (0.1)<0.0010.1 (0.1)

10 (8.5)
7 (7.3)6 (5.7)3 (4.8)<1.0
3 (2.7)14 (6.4)
20 (10)<0.001<0.0010.1 (0.2)<0.0010.2 (0.2)

27 (56)20 (68)30 (63)64 (190)
87 (126)
nm (c)
134 (93)
nm
nm
nm
nm
nm
nm

20
29 (42)
110
3 (4)
nm
5 (8)
19 (26)
nm
nm
nm
nm
nm
nm

184 (112)
8.2 (3.8)
16.8
2.7 (2.5)
6.7 (4.1)
0.5 (0.5)
0.05 (0.03) (ppm)
nm
nm
nm
nm
nm
nm

16.9
6.4
14.3
60
nm
nm
9.5
33
nm
nm
nm
nm
nm

29.8
12.5
18.0
5.9
0.6
0.9
15.9
27.7
nm
nm
nm
nm
nm

TVOC (d),(e),(f)Regulated chemicals
Unregulated chemicals

389 (112) (d)
70.0
319

390 (123) (d)
65.0
325

328 (720) (e)nmnm

780 (1103) (f)
nm
nm

nm
nm
nm

2327 (g)nm
nm

1280 (e)1371540(a) All the compounds were calculated by individual response factor. (b) LOQ: limit of quantitation. (c) nm: not measured; (d) TVOC: Total concentrations of 55VOCs, 14 carbonylcompounds and 22 SVOCs. (e) TVOC: Sum of VOCs (26). (f) TVOC: Total concentrations calculated as toluene between hexane and hexadecane. (g) TVOC: Total concentrations calculated
as toluene between hexane and hexadecane and carbonyl compounds.

Int. J. Environ. Res. Public Health 2019, 16, 4142

9 of 11Since building materials constitute an important source of VOC emissions, especially in newly
built houses, the houses studied here were built using carefully selected materials. Almost all thematerials had their emission rates measured via chamber tests, and low-emission materials wereselected and used. In addition, all 49 houses were equipped with 24-h mechanical ventilation systems.
We measured the ventilation rates in each of the living rooms and found them to range from 0.5–2.3 airchanges per hour. In particular, all the values exceeded the standard specified in the amended BuildingStandard Law set by the MLIT of Japan (0.5 air changes h). Such systems have been reported as being
useful for reducing the VOC concentrations in new houses [24], and we also observed beneficial
effects in the seven houses of our previous study [17]. There are two types of ventilation systems,
i.e., passive ventilation such as opening a window and active ventilation or mechanical ventilation,
but it is desirable to install mechanical ventilation for maintaining a certain number of ventilation rates
and preventing crime.
This study has shown that, even just after completion, VOC concentrations can be sufficiently
low if we use carefully selected low-emission materials. There are some reports on the health risks
in indoor environments, which are often related to the poor IAQ caused by a variety of factors,
including chemicals and microbiological contaminants [24–26]. This implies that residential houses
with good IAQ and those which do not have adverse health effects on humans can be constructedby selecting building materials on the basis of their emission rates. In addition, we also observedthat unregulated substances contributed greatly to the TVOC concentrations, reaching approximately
81.9–83.3% immediately after completion (Figure 1). We believe that some of these were substitutes forregulated solvents. In Japan, the VOC concentrations of unregulated compounds tend to be higher thanthose of regulated ones [27]. Among them some compounds, such as 2-ethyl-1-hexanol, 2-butanone,
ethyl acetate and butyl acetate, have been assessed [26] or have TLVs and LCI values [16]. There still
exist, however, compounds that have not been assessed nor have guideline values. To reduce the riskof indoor chemical exposure, we need to minimize the concentrations of such unregulated compounds.
Thus, we need to identify their sources, and also monitor which materials are being used at worksites
Environ. Res. Public Health 2019, 16, x FOR PEER REVIEW
10 of 12andInt.inJ. whatquantities.

Figure 1. Proportions of regulated and unregulated compounds in the living rooms and bedrooms.
Figure 1. Proportions of regulated and unregulated compounds in the living rooms and bedrooms.

5. Conclusions
5. Conclusions

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considering
thematerials
used. Thus, we believe that it is important to carefully select low-emission building materials toused.theThus,
we believethat toit isimportantto carefully
select welow-emissionbuilding
materials
toreduceresidents’
exposureindoorchemicals.
In addition,
also believethat active
ventilation,
reduce the residents’ exposure to indoor chemicals. In addition, we also believe that active
which
was effective in our previous study, i.e., the installation of a 24-h mechanical ventilation system
ventilation, which was effective in our previous study, i.e., the installation of a 24-h mechanicalis equally important. During the next stage of our project, we plan to (a) further explore and analyze
ventilation system is equally important. During the next stage of our project, we plan to (a) further
IAQ and (b) propose that safe building materials be labeled and listed in a newly created database
explore and analyze IAQ and (b) propose that safe building materials be labeled and listed in a newly
in Japan.
created database in Japan.

Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Table S1: VOC
concentrations in the living rooms and bedrooms, Table S2: Carbonyl compounds in the living rooms andbedrooms, Table S3: SVOC concentrations in the living rooms and bedrooms.
Author Contributions: Conceptualization, N.S. and H.N.; methodology, N.S., Kazunari.T. and H.N.;

Int. J. Environ. Res. Public Health 2019, 16, 4142

10 of 11

Supplementary Materials: The following are available online at http://www.mdpi.com/1660-4601/16/21/4142/s1,
Table S1: VOC concentrations in the living rooms and bedrooms, Table S2: Carbonyl compounds in the livingrooms and bedrooms, Table S3: SVOC concentrations in the living rooms and bedrooms.
Author Contributions: Conceptualization, N.S. and H.N.; methodology, N.S., K.T. (Kazunari Takaya) and H.N.;
investigation formal, N.S. and H.N. analysis and interpretation of data, N.S., H.N., Y.N., K.T. (Kayo Tsumura),
K.T. (Kazunari Takaya), E.T. and M.H.; data curation, N.S., H.N., Y.N., K.T. (Kazunari Takaya), K.T. (Kayo Tsumura),
M.H., E.T. and C.M.; writing—original draft preparation, N.S.; writing—review and editing, C.M. All authors readand approved the final manuscript.
Funding: This research was funded by Sekisui House Ltd. and Japan Society for the Promotion of Science (JSPS)
Grants-in-Aid for Scientific Research (C) Grant Number (19K12455, 18K13885). This work was supported by JST
OPERA Program Grant Number JPMJOP1831, Japan.
Conflicts of Interest: This study was supported by a grant from the Sekisui House Ltd. The sponsor had nocontrol over the interpretation, writing, or publication of this work.

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