Evaluation of Nitrogen Oxides Pollution in Takamatsu and Utazu Area in Kagawa Prefecture, Japan

doi:10.4236/jep.2011.22022

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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.

Email: [email protected]

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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