Journal of Environmental Protection, 2011, 2, 194-197
doi:10.4236/jep.2011.22022 Published Online April 2011 (http://www.SciRP.org/journal/jep)
Evaluation of Nitrogen Oxides Pollution in
Takamatsu and Utazu Area in Kagawa
Prefecture, Japan
Shoko Murakami1, Noriko Sakano1, Shigeru Suna2, Fumiyuki Asakawa3, Nobuyuki Miyatake1
1Department of Hygiene, Faculty of Medicine, Kagawa University, Miki, Kagawa, Japan; 2Kagawa Prefectural College of Health
Sciences, Kagawa, Japan; 3Kurashiki University of Science the Arts, Kurashiki, Japan.
Received December 21st, 2010; revised February 6th, 2011; accepted March 12th, 2011.
ABSTRACT
We evaluate nitrogen oxides pollution in Takamatsu and Utazu area in Kagawa prefecture, Japan. Annually observa-
tions for nitrogen oxides (nitrogen dioxide; NO2, nitric oxide; NO) (1990-2007) were obtained from data base of Ka-
gawa prefecture, Japan. Changes in NO2 and NO in Takamatsu and Utazu area were evaluated and compared. In 2007,
NO2, NO and NO2 + NO (ppm) in Takamatsu area were higher than those in Utazu area. However, NO2 /(NO + NO2) in
Takamatsu area was lower than that in Utazu area. From 1990 to 2007, mean of NO2 in a day over the level of 0.06
ppm was 30 days in Takamatsu area and only one day in Utazu area. Mean of NO2, NO and NO2 + NO was signifi-
cantly higher and NO2/(NO + NO2)was lower in Takamatsu area than that in Utazu area. In addition, NO2, NO and
NO2 + NO were negatively correlated and NO2/(NO + NO2) was positively correlated with years (1990 - 2007) in Ta-
kamatsu area. The level of nitrogen oxides pollution in Utazu area was lower than Takamatsu area. Further observa-
tion is required for preventing nitrogen oxides pollution in Kagawa prefecture, Japan.
Keywords: Nitrogen Oxides, NO2, NO, Utazu Area, Takamatsu Area
1. Introduction
Air pollution is one of the public health challenges in
Japan. Air pollution occurs where the natural composi-
tion of the atmosphere is altered significantly in a way
that is perceived as being harmful. In Japan, environ-
mental air quality has changed remarkably since the 1960s.
A serious environmental pollution problem caused by the
enormous emission of pollutants from industries has been
improved and controlled. Recently, another type of air
pollution related to au tomobile exhaust in large cities has
become a great problem.
Atmospheric Environmental Regional Observation
System [1] in Ministry of the Environment monitor air
pollutants, and their concentrations have not sufficiently
achieved Japanese Environmental Quality Standards
(JEQS) [2]. In Kagawa prefecture, Japan, air pollution
has been also observed in some observation points [3].
However, the changes in nitrogen oxides such as ni-
trogen dioxide (NO2), nitric oxide (NO), NO2 + NO and
NO2/(NO + NO2) in Kagawa prefecture, Japan still re-
mains to be investigated, although Takamatsu is a main
city located on north side of Shikoku and Utazu is a rural
town in Kagawa prefecture of Shikoku Island, which
sites are both located around the Inland Sea, Japan.
Therefore, we evaluate the detailed changes in nitrogen
oxides pollution in Takamatsu and Utazu area in Kagawa
prefecture, Japan and compared each other.
2. Methods
2.1. Study Area
Takamatsu area, Kagawa prefecture, Japan, which in-
cludes Takamatsu city, is on the northern shore of Shi-
koku Island (in a temperate zone area). The population of
420 000 people is situated on the Takamatsu area. Cur-
rently several public offices of Shikoku district are lo-
cated in Takamatsu city. Although the surrounds of Ta-
kamatsu had been used primarily as paddy fields for ag-
riculture, recently they have undergone rapid changes,
developing into residential and/or commercial areas
(Figure 1).
Utazu area, Kagawa prefecture, Japan, which includes
Utazu-cho, is also on the northern shore, west from Ta-

Evaluation of Nitrogen Oxides Pollution in Takamatsu and Utazu Area in Kagawa Prefecture, Japan195
kamatsu area of Shikoku Island [4]. The population of
18,000 people is situated on the Utazu area. Utazu area
had been used primarily as paddy fields for agriculture
compared to Takamatsu area (Figure 1). Both observa-
tion sites are located around the Inland Sea, Japan.
2.2. Data of Nitrogen Oxides
Data of nitrogen oxides pollution in Takamatsu and
Utazu areas in Japan for the required periods (1990-2007)
were obtained from Data base of Kagawa prefecture,
Japan [5]. NO2 (ppm), NO (ppm), NO2 + NO (ppm) and
NO2/(NO + NO2) (%) were used for analysis. In general,
toxicity of NO2 is higher than that of NO in plants [6],
Therefore, we evaluate NO2/(NO + NO2) (%) were also
used for analysis.
2.3. Statistical Analysis
Data are expressed as means ± standard deviation (S.D.)
values. A comparison of parameters between the 2
groups was made using an unpaired t-test. Simple corre-
lation analysis was performed as well to test for the sig-
nificance of the linear relationship among continuous
variables, p < 0.05 was considered to indicate statistical
significance.
3. Results
NO2, NO, NO2 + NO and NO2/(NO + NO2) in Takamatsu
and Utazu area in 2007 are summarized in Table 1. NO 2,
NO and NO2 + NO in Takamatsu area were higher than
those in Utazu area. However, NO2/(NO + NO2) Taka-
matsu area was lower than that in Utazu area.
From 1990 to 2007, we compared the nitrogen oxides
between Takamatsu and Utazu area (Table 2). Mean of
NO2 in a day over the level of 0.06 ppm was 30 days in
Takamatsu area and only one day in Utazu area during
Utazu
Kagawa prefecture
Okayama prefecture
Takamatsu
●
●
Figure 1. Study point of Takamatsu and Utazu, Kagawa
prefecture, Japan (http://www.craftmap.box-i.net/map.php,
accessed on Aug 27, 2010).
Table 1. Concentration or percentage of nitrogen oxides in
Takamatsu and Utazu area in 2007.
Takamatsu area Utazu area
Mean of NO2 (ppm) 0.019 0.017
Mean of NO (ppm) 0.010 0.007
Mean of NO2 + NO (ppm)0.029 0.024
NO2/(NO + NO2) (%) 65.1 69.8
observation period (1990-2007). Mean values of NO2,
NO and NO2 + NO in Takamatsu area were significantly
higher than those in Utazu area. However, mean value of
NO2/(NO + NO2) in Takamatsu area was lower than that
in Utazu area as showed in 2007.
We further analyzed the relationship between nitrogen
oxides and years in Takamatsu and Utazu areas. NO2,
NO and NO2 + NO were negatively correlated with years
in Takamatsu area. NO2/(NO + NO2) was positively
corre- lated with years in Takamatsu area (Table 3, Fig-
ure 2). In Utazu area, parameters of nitrogen oxides were
not significantly correlated with years.
4. Discussion
We firstly evaluated and compared nitrogen oxides pol-
lution in Takamatsu and Utazu area, Kagawa prefecture,
Japan, which located around the Inland Sea, Japan. NO2,
NO and NO2 + NO in Takamatsu area were higher than
in Utazu area. However, NO2, NO and NO2 + NO in Ta-
kamatsu area were significantly improved these years.
JEQS [2] of NO2 were recommended that mean value
of NO2 in a day was under the level of 0.06 ppm and NO2
value in Japan were almost under the level of 0.06 ppm
[7]. Ono et al. reported that they surveyed the charac-
terization of residential suspended particulate matter
(SPM) and NO2 concentrations along the major road
ways in Tokyo [8]. The prevalence rate of respiratory
symptoms was higher in those areas nearest roadways
with heavy traffic both in children and adults [1]. Yori-
fuji et al. reported that long term exposure to traf-
fic-related air pollution, indexed by NO2 concentration,
increases the risk of cardiopulmonary mortality, even in a
population with a relatively low BMI and increases the
risk of lung cancer mortality in non-smokers [9]. Piver et
al. also reported that same-day daily maximum tempera-
ture and daily average concentrations of NO2 were the
most significant risk factors for heat stroke in all age
groups of males and females [10]. Rosenlund et al.
showed that long-term air pollution exposure increases
the risk of coronary heart disease during the period 1998
- 2000 [11]. In addition, Yamazaki et al [12] showed th at
they evaluated the relationship between nitrogen oxides
and health-related quality of life (HRQOL) by using
Medical Outcomes Study Short From-36 Health Survey

Evaluation of Nitrogen Oxides Pollution in Takamatsu and Utazu Area in Kagawa Prefecture, Japan
196
Table 2. Comparison of nitrogen oxides from 1990 to 2007 in Takamatsu and Utazu area, Japan.
Takamatsu area Utazu area
Mean ± S.D. Max. Min. Mean ± S.D. Max. Min p
NO2 (ppm) 0.025 ± 0.00 3 0.030 0.019 0.019 ± 0.002 0.023 0.016 < 0.0001
NO (ppm) 0.021 ± 0.006 0.03 0 0.031 0.010 ± 0.002 0.014 0.007 < 0.0001
NO2 + NO (ppm) 0.046 ± 0.009 0.061 0.029 0.029 ± 0.004 0.038 0.022 < 0.0001
NO2/(NO + NO2) (%) 54.9 ± 4.6 65.1 48.6 65.1 ± 2.6 69.9 60.2 < 0.0001
p: Takamatsu area vs. Utaz u area (unpaired t-test)
Table 3. Relationship between nitrogen oxides and years (1990-2007) in Takamatsu and Utazu area, Japan.
Takamatsu area Utazu area
r p r P
Mean of NO2 in a year (ppm) –0.548 0.019 –0.093 0.714
Mean of NO in a year (ppm) –0.580 0.012 –0.335 0.175
Mean of NO2 + NO in a year (ppm) –0.565 0.015 –0.200 0.427
NO2/(NO + NO2) (%) 0.589 0.010 0.376 0.124
Figure 2. Changes in parameters of nitrogen oxides from 1990 to 2007 in Takamatsu and Utazu areas in Kagawa prefecture,
Japan.
(SF-36) [13]. They observed a significant linear trend of
a lower ‘vitality’ domain score in the SF-36 in groups
exposed to higher concentrations of nitrogen oxides [12].
In this study, we evaluated the parameters of nitrogen
oxides in Takamatsu and Utazu area in Kagawa prefec-
ture, Japan. Over the level of 0.06 ppm in NO2 was 30
days in Takamatsu area and only one day in Utazu area
during observation period (1990 - 2007). In addition,

Evaluation of Nitrogen Oxides Pollution in Takamatsu and Utazu Area in Kagawa Prefecture, Japan197
NO2, NO and NO2 + NO in Takamatsu area were sig-
nificantly improved.
Potential limitation s still remain in this study. First, we
could not prove the link between nitrogen oxides and
health status i.e. cardiopulmonary diseases, mortality rate
and HROQL as previous studies. Second, although
Ramadan reported that the NO distribution was similar to
that of NO2 [14], NO2/(NO + NO2) in Takamatsu area
was positively correlated with years. In general, toxicity
of NO2 is higher than that of NO in plants [6]. Hiragushi
et al have studied the relation between diabetic glomeru-
lar hyperfiltration and the NO system. And they found
that the urinary NOx (2 and 3) was significantly
higher in normoalbumiuric in patients with type 2 diabe-
tes mellitus compared with normal subjects [15]. In addi-
tion, NO, known as endothelium derived relaxing factor,
is involved in glomerular hyperfiltration of experimental
diabetic rats [16]. Taylor et al. reported that two signifi-
cant cases that illustrate the probable cause and the
treatment strategies for delivery of high concentrations of
NO, resulting in methemoglobinemia with moderate and
even low-dose delivered NO [17]. We could not prove
the mechanism and issues of an increase in NO2/(NO +
NO2) in Takamatsu area, Kagawa prefecture, Japan.
Therefore, monitoring of nitrogen oxides pollution are
further required for preventing air pollution-related dis-
eases in Kagawa prefecture, Japan.
NONO
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