Vol.3, No.9, 545-548 (2011)
doi:10.4236/health.2011.39092
C
opyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
Health
Air temperature was associated with ambulance
transports in Osaka area, Japan
Nobuyuki Miyatake1*, Noriko Sakano1, Shoko Murakami1, Takeshi Suzue2, Takeshi Yoda2,
Akira Yoshioka2, Tomohiro Hirao2
1Department of Hygiene, Faculty of Medicine, Kagawa University, Kagawa, Japan;
*Corresponding Aut hor:
2Department of Public Health, Faculty of Medicine, Kagawa University, Kagawa, Japan.
Received 4 July 2011; revised 1 August 2011; accepted 9 August 2011.
ABSTRACT
We investigated the link between ambulance
transports and meteorological parameters of
summer by using daily data in Osaka area, Ja-
pan. Daily observations for ambulance trans-
ports (from July 1 to September 30, 2009) were
obtained from Fire Department Service in Osaka.
Data of meteorological parameters in Osaka
area, Japan (from July 1 to September 30, 2009)
were also obtained from Japan Meteorological
Agency. Effect of meteorological parameters on
ambulance transports was analyzed. A total of
49,526 ambulance transports were observed
from July 1 to September 30, 2009 in Osaka,
Japan. Ambulance transports were significantly
correlated with mean air temperature (r = 0.298),
the highest air temperature (r = 0.347), the low-
est air temperature (r = 0.209) and daylight hour s
(r = 0.301). The higher air temperature was as-
sociated with higher ambulance transports of
summer in Osaka area, Japan.
Keywords: Ambulance Transports;
Air Temperature; Osaka Area; Daylight Hou rs
1. INTRODUCTION
Global warming has become public health challenge
in Japan. Global average temperatures are predicted to
increase between 1.4˚C and 5.8˚C by the end of this cen-
tury [1]. We have previously showed that estimated
changes in mean temperature was 1.6˚C for 50 years in
Osaka areas, Japan [2]. In addition, by using monthly
data, higher air temperature was associated with ambu-
lance transports in Takamatsu [3] and Okayama [4] areas,
Japan. Basu et al. also reported that th e relation between
elevated ambient air temperature and mortality in their
review [5]. However, the link between ambulance trans-
ports by using daily data and meteorological parameters
i.e. air temperature, humidity, atmospheric pressure and
daylight hours still remains to be investigated.
Therefore, we investigated the relationship between
ambulance transports of summer and meteorological
parameters by using daily data in Osaka area, Japan.
2. METHODS
2.1. Study Area
Osaka area is the second largest metropolitan area in
Japan and its population is abo ut 8.7 million . Osaka city
(2.6 million population, 220 km2) is located in the center
of the metropolitan area, and have been mostly urban-
ized for a long time in Japan. The Osaka plain is sur-
rounded by Hokusetsu and Rokko mountains to the north,
Ikoma mountain on the east side, Izumi Mountain in the
south, and Osaka Bay to the west.
2.2. Ambulance Dat a
Daily incidence data of ambulance transports was ob-
tained from Fire Department Service in Osaka from July
1 to September 30, 2009 [6].
2.3. Meteorological Parameters
Daily meteorological parameters in Osaka areas in
Japan for the required periods were obtained from Japan
Meteorological Agency [7]. The observation spots were
located at the central in the area. Daily meteorological
parameters i.e. mean atmospheric pressure (land surface)
(hPa), mean atmospheric pressure (sea surface) (hPa),
total precipitation (mm), mean air temperature (˚C), the
highest air temperature (˚C), the lowest air temperature
(˚C), mean humidity (%), the lowest humidity (%), mean
velocity of the wind (m/s) and daylight hours (hours)

N. Miyatake et al. / Health 3 (2011) 545-548
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
546
were used for analysis.
2.4. Statistical Analysis
Simple correlation analysis was used to test the sig-
nificance of the linear relationship among continuous
variables. p < 0.05 was considered to be statistically sig-
nificant.
3. RESULTS
Profiles of used daily data in Osaka area from July 1
to September 30, 2009 were summarized in Table 1. A
tota l of 49,526 ambul ance transports wer e observed from
July 1 to September 30, 2009 in Osaka area, Japan.
Mean ambulance transports was 538.3 ± 33.0/day, re-
spectively.
We investigated the relationship between ambulance
transports and meteorological parameters by simple cor-
relation analysis (Table 2). Ambulance transports were
significantly correlated with mean air temperature, the
highest air temperature (Figure 1), the lowest air tem-
perature and daylight hours. Correlation coefficient rate
Table 1. Profiles of used daily data in Osaka area from July 1 to September 30, 2009.
Mean ± SD Minimum Maximum
Number of days 92
Mean atmospheric pressure (land surface) (hPa) 1000.2 ± 4.3 990.0 1010.2
Mean atmospheric pressure (sea surface) (hPa) 1009.6 ± 4.4 999.3 1019.9
Total precipitation (mm ) 2.8 ± 5.9 0.0 30.5
Mean air temperature (˚C) 26.6 ± 2.3 20.8 30.8
The highest air temperature (˚C) 31.1 ± 2.8 22.0 36.3
The lowest air temperature (˚C) 23.3 ± 2.5 17.8 27.7
Mean humidity (%) 65.4 ± 9.2 48.0 88.0
The lowest humidity (%) 47.7 ± 11.4 27.0 81.0
Mean velocity of the wind (m/s) 2.4 ± 0.6 1.4 4.7
Daylight hours (hours) 5.6 ± 3.9 0.0 12.3
Ambulance transport (number/day) 538.3 ± 33.0 454.0 616.0
Table 2. Simple correlation analysis between ambulance transports and meteorological pa-
rameters from July 1 to September 30, 2009.
r p
Mean atmospheric pressure (land surface) (hPa) 0.086 0.4165
Mean atmospheric pressure (sea surface) (hPa) 0.090 0.3927
Total precipitation (mm ) –0.085 0.4186
Mean air temperature (˚C） 0.298 0.0039
The highest air temperature (˚C) 0.347 0.0007
The lowest air temperature (˚C) 0.209 0.0461
Mean humidity (%) –0.076 0.4694
The lowest humidity (%) –0.161 0.1250
Mean velocity of the wind (m/s) 0.152 0.1480
Daylight hours (hours) 0.301 0.0035

N. Miyatake et al. / Health 3 (2011) 545-548
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547547
˚C
Figure 1. Simple correlation analy sis between ambulance transports (/day) and the highest air
temperature (˚C) by using da ily data in Osaka ar ea, Japa n.
between the highest air temperature and ambulance
transports was the highest. However, other parameters
were not correlated with ambulance transports.
4. DISCUSSION
We firstly evaluated the link between ambulance
transports and meteorological parameters by using daily
data in Osaka area, Japan. The highest air temperature
was closely associated with ambulance transports.
Average subsurface temperature profiles in four Asian
cities (Tokyo, Osaka, Seoul and Bangkok) were com-
pared and analyzed to evaluate the effects of surface
warming [8]. The magnitude of surface warming was the
largest in Tokyo (2.8˚C), followed by Seoul, Osaka and
Bangkok. The combination of the heat island effect due
to urbanization and global warming on subsurface tem-
peratures also relates to global ground water quality is-
sues [9]. In addition, in some literatures, the link be-
tween high temperatures and heat-related diseases has
been reported. Bai et al. reported that the number of un-
usual deaths in the summer of 1994 in Osaka, Japan was
more compared to those of previous years [10]. Nakai et
al. also investigated heat-related deaths in Japan from
1968 through 1994 and heat-related deaths were most
prone to occur on days with a peak daily temperature
above 38 degrees C [11]. Th ey reported that incidence of
heat-related deaths showed and exponential dependence
on the number of hot days [11]. Qiu et al. reported that
an unusually hot spell in 1999 was followed by a high
mortality rate in Hokkaido, Japan [12]. Piver et al.
showed that heat stroke was associated with prolonged
exposures to higher air temperatures that usually occur
in the summer months of July and August in 1980-1995
in Tokyo [13]. In our previous study, higher air tem-
perature was closely associated with higher ambulance
transports in Takamatsu and Okayama city using
monthly data [3,4]. We also found that high air tem-
perature was associated with ambulance transports by
using daily data in Osaka area, Jap an in this study. Coef-
ficient rate between ambulance transports and the high-
est air temperature was the highest among parameters.
Furthermore, the slope of the regression line (change in
highest air temperature vs change in ambulance trans-
ports) in Osaka city was 4.125 (Figure 1). Accordingly,
we found that a 1˚C increase in highest air temperature
of summer in Osaka area, Japan, corresponded to a
4.125/day increase in ambulance transports in Osaka
area, Japan.
Potential limitations still remain in this study. First,
the link between ambulance transports and air tempera-
tures, which was noted in this study, may not apply for
the link among individuals. Second, we could not di-
rectly evaluate heat-related diseases or deaths. Therefore,
we could not accurately evaluate the link between am-
bulance transports and high air temperatures. Further
studies are required to prove such link.

N. Miyatake et al. / Health 3 (2011) 545-548
Copyright © 2011 SciRes. Openly accessible at http://www.scirp.org/journal/HEALTH/
548
5. ACKNOWLEDGEMENTS
This research was supported in part by Research Grants from FU-
KUTAKE Science & Culture Foundation, Japan.
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