Journal of Environmental Protection, 2013, 4, 33-40
Published Online December 2013 (http://www.scirp.org/journal/jep)
http://dx.doi.org/10.4236/jep.2013.412A1004
Open Access JEP
Decline of VOC Concentrations with the Aging of Houses
in Japan
Motoya Hayashi1, Haruki Osawa2
1Department of Life Style and Space Design, Miyagi Gakuin Women’s University, Sendai, Japan; 2Department of Healthy Building
and Housing, National Institute of Public Health, Wako, Japan.
Received September 8th, 2013; revised October 12th, 2013; accepted November 7th, 2013
Copyright © 2013 Motoya Hayashi, Haruki Osawa. This is an open access article distributed under the Creative Commons Attribu-
tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited. In accordance of the Creative Commons Attribution License all Copyrights © 2013 are reserved for SCIRP and the owner of
the intellectual property Motoya Hayashi, Haruki Osawa. All Copyright © 2013 are guarded by law and by SCIRP as a guardian.
ABSTRACT
The purpose of this investig ation is to know the long-term characteristics of VOC concentrations in houses bu ilt before
the building code in 2003 and to clarify th e coun termeasures against indoor air po llution in the houses already built. For
example, the improvements of living habits, ventilation and the remove of building materials. The concentrations of
VOCs were measured in these houses in summer and winter from 2000 to 2005. The results showed that the concentra-
tion of formaldehyde decreased in the first year. After that the decline of the concentration was not seen and the con-
centration chang ed only with the temperature. The characteristics of decline were thought to be caused by two sorts of
emission. One is an emission of concealed formaldehyde in the process of material production and the other is an emis-
sion with the generation of formaldehyde from adhesives of urea resin and moisture. The concentration of toluene de-
creased rapidly in the first year. The concentrations of xylene, ethyl-benzene and styrene showed a similar change. But
the concentrations of acetaldehyde which were measured from the summer of 2002 did not decrease and its concentra-
tion in some houses was higher than the guideline even in the winter of 2005.
Keywords: Indoor Air Quality; VOC; Passive Sampling; Questionnaire Survey; Statistics Analysis
1. Introduction
A traditional Japanese house has a structure of wooden
posts and beams. Houses with this structure have wide
openings. Therefore the traditional house is beneficial to
indoor cooling in summer and to the prevention of the
deterioration of wooden materials. Also there are many
air infiltration routes through the wall, floor, ceiling, etc.
Since 1970s, the structures have been improved to be
airtight and insulated using insulation materials and films.
However, many infiltration routes lurk in the concealed
spaces like spaces inside the walls, the ceilings and the
floors [1].
The living style of Japanese dwellers has changed in
the sixty years after World War 2. The unoccupied time
in houses became longer, because the number of family
became smaller. And the time of opening windows be-
came shorter with the spread of air conditioner. New
building materials have been produced in factories since
1960s, and prefabricated houses have expanded in Japan
since 1970s. Under these situations, “sick house”: the
indoor air pollution by chemical compounds from build-
ing materials, has been closed up in Japan since 1990s.
And many countermeasures against indoor air pollution
in houses have been taken by the Japanese government,
building companies, building material manufacturers and
other related groups. And a new building code with
countermeasures against indoor air pollution has been
forced by the Ministry of Land, Infrastructure and
Transport since 2003. According to this building code the
concentration of formaldehyde is expected to be lower
than the guideline: 0.08 ppm, which was established by
the Ministry of Health, Labour and Welfare of Japanese
Government in 1993. This building code requires our
consideration about the emission rate of formaldehyde
from building materials. The regulated materials are not
only building materials which are used for interior finish
but also materials which are concealed in walls, ceilings
and floors. And the installation of ventilation equipment

Decline of VOC Concentrations with the Aging of Houses in Japan 34
is required in all residential spaces. The required ventila-
tion time is 0.5 times per hour [2]. Before this building
code, the concentrations of formaldehyde were higher
than the guideline at the completion of houses in many
cases. And some investigations showed that the concen-
trations of formaldehyde do not decrease with time soon
[3-8]. Organic compounds are volatizing from building
materials and from furniture and articles which are car-
ried into houses by residents, so the indoor concentra-
tions do not decrease with the aging of houses. Therefore
the influences of indoor pollution on the residents’ health
may continue long and these influences may become a
cause of a multiple chemical sensitivity [1]. Under these
contexts the decline of concentrations with the aging of
houses was investigated.
2. Methods
The concentrations of formaldehyde, toluene, xylene,
ethyl-benzene, styrene and acetaldehyde were measured
in winter and in summer for five years in about two hun-
dred and fifty houses in which formaldehyde concentra-
tion was higher than the guideline: 0.08ppm in 2000. The
first investigations in 2000 were carried out from sum-
mer to winter continuously in new houses which were
built less than a year ago. The number of investigated
houses decreased gradually and became eighty-four in
the winter of 2005 as shown in Figure 1. The concentra-
tions were measured using passive samplers made by
Advanced Chemical Sensor Inc. The samplers were sent
to the residents from a laboratory. The residents placed
samplers in the rooms for 24 hours and sent them back to
the laboratory. The concentrations were specified using
gas chromatographs in the laboratory. The characteristics
of buildings and residents were checked using question-
naires. The indoor temperatures and the humidity were
measured by residents and were checked on the ques-
tionnaires. The number of investigated houses changed.
But the results of statistical analysis using the eig hty-four
houses in which the concentrations were obtained during
all the periods were quite similar to the results using all
the data. The difference between the average formalde-
hyde concentration of these eighty-four houses and that
of all the houses is smaller than 4%. Th erefore the resu lts
using all the data are reported in this paper.
3. Results
Figure 2 shows classifications of investigated houses.
They consist of apartment houses and detached houses.
Most apartment houses were built with reinforced con-
crete structure. And the numbers of stories of 45% of the
apartment houses were from one to three. And those of
the other apartment houses were from three to ten. The
0
100
200
300
20002001sum 2001win 2002sum 2002win 2003sum 2003win 2004sum 2004win 2005sum 2005win
Number of houses
Detached houseApartment house
Figure 1. Number of investigated houses.
0%
20%
40%
60%
80%
100%
2000-2005
A
partment house
Detached house
0%
20%
40%
60%
80%
100%
2000-2005
2inch X4inch wooden stud
structu re
Wooden post and beam
structu re
Prefabricated wooden panel
structu re
Prefabricated steal structure
Reinforced concrete structure
The other
Figure 2. Classification of houses.
Open Access JEP

Decline of VOC Concentrations with the Aging of Houses in Japan 35
structure types of detached houses were various but most
detached houses were built with wooden post and beam
structure which is common in Japan. Another structure
was 2 inch × 4 inch wooden stud structure which has
been imported and built generally since 1980s. The oth-
ers were prefabricated structures. Most of the prefabri-
cated houses are produced in large factories by major
housing companies. The percentage of the classification
of houses was similar to the percentage of all houses
built recently in Jap an.
Figure 3 shows the weather conditions an d the humid-
ity when the concentrations were measured in houses. In
summer, the percentage of “cloudy” was a little smaller
than that in winter. The temperatures were shown in Fig-
ure 4. Naturally the temperatures were high in summer
and low in winter. The humidity changed with the tem-
perature; it is hot and humid in summer and it is cold in
winter. This annual change is typic al in m ost a reas of Japa n.
Figure 5 shows how long the residents keep the win-
dows of their houses open in a day. The percentage of
open windows does not contain the percentage in the
case that the windows are open for less than one hour.
Naturally the percentage of open windows is larger in
summer than in winter.
0%
20%
40%
60%
80%
100%
Sum Win
Cloudy Rain Sunny
0%
20%
40%
60%
80%
100%
Sum Win
20-39 40-5960-
Figure 3. Weather and humidity.
20.9
29.1
21.4
27.4
21.1
27.6
19.2
28.8
17.4
27.1
15.7
0.11
0.07
0.03
0.05
0.03
0.06
0.03
0.06
0.02
0.05
0.02
0.151
0.022
0.0130.010
0.006 0.009
0.0040.0040.003 0.001 0.002
0
10
20
30
40
50
60
20002001sum2001win 2002sum2002win 2003sum2003win 2004sum2004win 2005sum2005win
Temperature (deg.C)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Concentration (ppm)
Indoor temerature (degC)FormaldehydeToluene
Figure 4. Change of temperature and concentrations.
Open Access JEP

Decline of VOC Concentrations with the Aging of Houses in Japan 36
Figure 6 shows the changes of formaldehyde concen-
trations. In this figure the standard deviations of concen-
trations on each measurement period are showed using
lines. The average of concentration of formaldehyde was
higher than the guideline: 0.08ppm in 2000. This is be-
cause the houses were chosen from the houses in which
the concentration exceeded the guideline when investi-
gated in 2000. The concentration of formaldehyde de-
creased from 2000 to the winter of 2001 but the concen-
tration increased in the summer of 2002. After 2003, the
concentration increased in summer and decreased in
winter. This annual change was repeated during the four
years.
Figure 7 shows the concentration of toluene. The av-
erage concentration was higher than the guideline: 0.07
ppm in 2000. The concentrations decreased and became
lower than the guideline in the summer of 2001. The
concentrations did not change with temperature. Figure
8 shows the concentration of xylene. The concentration
was lower than the guideline: 0.20 ppm in 2000. The
concentration decreased during the first year and was low
during these five years. In 2003 the concentration in-
creased a little but the reason was not clear.
0%
20%
40%
60%
80%
100%
Sum Win
Opening windowsClosing windows
Figure 5. About opening windows.
Concentration of formaldehyde (ppm)
0.113
0.073
0.031
0.054
0.033
0.059
0.025
0.060
0.021
0.046
0.019
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
20002001sum2001win 2002sum2002win 2003sum2003win 2004sum2004win 2005sum 2005win
Guidline:0.08ppm
Figure 6. Decline of formaldehyde concentration.
Concentration of toluene(ppm)
0.151
0.022 0.013 0.010 0.006 0.009 0.004 0.0040.0030.001 0.002
0
0.05
0.1
0.15
0.2
0.25
0.3
20002001sum 2001win2002sum2002win2003sum 2003win 2004sum 2004win2005sum 2005win
Guidline:0.07ppm
Figure 7. Decline of toluene concentration.
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Decline of VOC Concentrations with the Aging of Houses in Japan 37
Concentration of xylene(ppm)
0.025
0.009 0.005 0.0030.002 0.009 0.010
0.000 0.003 0.000 0.002
0
0.02
0.04
0.06
0.08
0.1
0.12
2000 2001su
m
2001win 2002sum2002win 2003sum2003win 2004su
m
2004win2005sum 2005win
Guidline:0.20ppm
Figure 8. Decline of xylene concentration.
Figure 9 shows the concentration of ethyl-benzene.
The concentration was also very much lower than the
guideline: 0.88 ppm even in 2000. The concentration
decreased during the first year and was low after that. In
the winter of 2003 the concentratio n increased a little bu t
the reason was not clear. These temporary rises are
thought to be caused by the pollution sources like furni-
ture or insecticide which are carried in houses by resi-
dents.
Figure 10 shows the concentrations of styrene. The
average concen tration was lower than the guideline: 0.05
ppm in 2000. But in some houses the concentrations
were higher than the guideline. The concentration de-
creased during the first year and was lower during these
five years. In 2003 the concentration increased a little.
Figure 11 shows the concentration of acetaldehyde.
The concentration was measured after the summer of
2002. The concentration was not enough lower than the
guideline: 0.03 ppm in the summer of 2003. And the
concentration increased gradually during the four years.
The reason of this increase is not clear. One of the emis-
sion sources is smoking but the percentage of “smoking”
was almost 11% in all measurement periods. The other
source is thought to be building materials. Anyway it
became clear that the concentration of acetaldehyde ex-
ceeded the guideline in some houses.
Figure 12 shows the percentage of houses where the
residents felt physical changes in houses. The residents
answered the following question: Have you felt a change
of physical condition which is thought to be caused by
the chemical compound. If the answer was “yes”, the
following items were also checked: who felt the change,
the physical conditions, when the change was felt. And
the following physical conditions: nausea, headache,
eczema, the pain of eyes, nose and throat were appealed
on the questionnaires. The percentage of the residents
who felt the change of their physical conditions was lar-
ger in summer and smaller in winter. This change was
similar to that of the formaldehyde concentration shown
in Figure 4. But the percentage decreased gradually and
the fluctuation of the percentage also decreased. These
results show that it is necessary to investigate the rela-
tionship between the indoor air qu ality and the residents’
feeling about the change of physical condition which are
checked on the questionnaires. This investigation is ex-
pected to be made with their medical researchers.
Figure 4 shows the change of temperature and con-
centrations. The concentrations of formaldehyde changed
with temperature.
Figure 13 shows the relationship between tempera-
tures and concentrations. In the case of formaldehyde the
concentrations are distributed on a curve: “Calculation
(C25 = 0.046, a = 1.11)” in Figure 13. This curve is cal-
culated using the following equation.
T25
25
CCa

 (1)
where C: concentration,

C25E25 Q

, E25: emis-
sion rate when temperature is 25deg.C, Q: ventilation
rate, β: ratio of sink, a: coefficient of influence of tem-
perature (a = 1.11: a value which was measured in small
chambers).
The formaldehyde concentration in 2000 was not on
the curve but the other co ncentrations fitted o n this curve
generally. This shows that the ability of formaldehyde
emission hardly decreased after 2001.
Figure 14 shows the measured concentrations of for-
maldehyde and the normalized concentrations: C25
which is calculated using equation 1. The normalized
concentration is thought to be an indicator of emission
possibility in a house. The normalized concentration de-
creased fast from 2000 to the summer of 2001 and was
steady after that. This charcteristic of concentration a
Open Access JEP

Decline of VOC Concentrations with the Aging of Houses in Japan 38
Concentration of ethyl-benzene （ppm）
0.025
0.003 0.000 0.000 0.001 0.001 0.004
0.000 0.000 0.000 0.000
0
0.01
0.02
0.03
0.04
0.05
0.06
20002001sum 2001win2002sum 2002win2003sum 2003win2004sum 2004win2005sum 2005win
Guidline:0.88ppm
Figure 9. Decline of ethyl-benzene concentration.
Concentration of styrene （ppm）
0.025
0.009 0.005 0.003 0.002 0.009 0.010
0.000 0.003 0.000 0.002
0
0.02
0.04
0.06
0.08
0.1
0.12
20002001sum 2001win2002sum 2002win2003sum 2003win2004sum 2004win2005sum 2005win
Guidline:0.05ppm
Figure 10. Decline of styrene concentration.
Concentration of acetaldehyde(ppm)
0.012
0.016 0.015 0.013
0.019
0.017
0.015
0.018
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
20002001sum 2001win2002sum 2002win2003sum 2003win2004sum2004win2005sum 2005win
Guidline:0.03ppm
Figure 11. Decline of acetaldehyde concentration.
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Decline of VOC Concentrations with the Aging of Houses in Japan 39
Percentage of houses where residents felt the change of physical condition(%)
2.7%
18.4%
4.3%
13.8%
3.0%
5.6% 4.2%
0%
5%
10%
15%
20%
25%
20002001sum2001win2002sum 2002win2003sum 2003win
Figure 12. Percentages about change of physical condition with chemical co mpound.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
10 15 2025 30 35
Indoor temperature (degC)
Concentration (ppm)
Formaldehyde
Equation 1 (C25=0.046, a=1.11)
Toluene
2000
2000
2001 sum.
2001 sum.
Figure 13. Relationship between temperatures and concentrations.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
2000/
6
2000/
12
2001/
6
2001/
12
2002/
6
2002/
12
2003/
6
2003/
12
2004/
6
2004/
12
2005/
6
2005/
12
Concentration (ppm)
F ormaldehy de
F ormaldehy de(T=25degC)
C
25
Figure 14. Change of the normalized formaldehyde concentration at a temperature 25˚C.
Open Access JEP

Decline of VOC Concentrations with the Aging of Houses in Japan
Open Access JEP
40
decline may be caused by a mechanism of emission from
building materials. In Japanese houses main emission
sources of formaldehyde were wooden building materials
produced in factories like plywood and particle board. In
the case of houses built in 2000, most of these materials
were made using adhesives of urea resin which is made
with formaldehyde. A part of formaldehyde was con-
cealed in the materials when they were produced in fac-
tories. Soon after production these concealed formalde-
hyde may start to volatilize. On the other hand formal-
dehyde is generated from inside urea resin and moisture
after production. The generation rate is influenced by
temperature and humidity. And the generated formalde-
hyde diffuses to the surface and volatilizes into indoor air.
The calculated decline curve of normalized concentration
shows that the emission of concealed formaldehyde fin-
ished in almost one year and the emission with the gen-
eration of formaldeh yde contin ues for a long ti me at least
for five years. The emission will continue until all the
sources of formaldehyde are lost.
4. Conclusion
The investigation on the decline of indoor chemical pol-
lution was carried out in Japanese houses. The concen-
trations of toluene, xylene, ethyl-benzene, styrene de-
crease fast and the concentrations were lower than the
guidelines in most houses at least after one year. But the
concentrations of formaldehyde and acetaldehyde were
above the safety zone. In the case of formaldehyde the
concentration decreased during the first one year but the
concentration did not decrease at all during the next four
years. The concentration became higher in summer every
year. Therefore the long-term countermeasure against
chemical pollution in su mmer is thought to be necessary.
If residents have suffered some impairment by indoor
chemical pollution, renovations of buildings especially
considering indoor air quality will be necessary not only
in new houses but als o in ol d ho uses.
5. Acknowledgements
The study was a part of a national project “Development
of Countermeasure Technology on Residential Indoor
Air Quality” by National Institute for Land and Infra-
structure Management under the Japanese government.
The investigations were made with the contributions of
many residents. And the investigations were made with
the cooperation of Center for Housing Renovation and
Dispute Settlement Support and the students of Miyagi-
gakuin Women’s University. The authors express their
gratitude to them and to Dr. Kouichi Ikeda of National
Institute of Public Health, Dr. Yasuo Kuwasawa of Na-
tional Institute for Land and Infrastructure Management,
Prof. Hiroshi Yoshino of Tohoku University and the
committees of the nationa l pro jects.
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