International Journal of Medicine and Medical Sciences Vol. 1(7) pp. 288-289, July, 2009
Available online http://www.academicjournals.org/ijmms©2009 Academic Journals

Short Communication

Effect of chlorine dioxide gas of extremely low
concentration on absenteeism of schoolchildren
Norio Ogata* and Takashi Shibata
Taiko Pharmaceutical Co., Ltd., Osaka, Japan.
Accepted 03 July, 2009

Gas-generating devices of chlorine dioxide (ClO2) are used as deodorant of rooms. We happened to use
a commercial tabletop deodorant canister that releases extremely low-concentration ClO2 gas in aschool classroom as deodorant. We found retrospectively and unexpectedly that during a period of 38
consecutive school days the rate of school children absent from the school was markedly lower (1.5%)
in a classroom where the ClO2 device was placed than that (4.0%) in a classroom where it was notplaced. The percentages of absenteeism between these classrooms (1.5% vs. 4.0%) were significantly(p < 0.00001) different. The predominant causes of absenteeism during the period were common coldand influenza. Judging from the known virucidal activity of ClO2, our unexpected finding in the schoolclassrooms strongly suggests the usefulness of extremely low-concentration ClO2 gas to prevent
respiratory viral diseases in semi-closed areas, such as theaters, hospitals and aircraft, without
necessitating evacuation.
Key words: Chlorine dioxide, absenteeism, schoolchildren, gas, influenza, respiratory infection, virus.
INTRODUCTION
Chorine dioxide (ClO2) is water-soluble gas at room
temperature (Gordon et al., 1972). It has long been used
as a disinfectant of tap water (Betancourt and Rose,2004), bleach (Moran et al., 1953) and deodorant(Loesche and Kazor, 2002). Owing to its strong oxidizing
activity, it inactivates bacteria, fungi and viruses (Berg etal., 1982; Morino et al., 2007; Roller et al., 1980; Simonetand Gantzer, 2006). ClO2 gas released from its aqueous
solution has been used as a sanitizer and a deodorant ofroom air. We used a commercial tabletop deodorant ClO2
gas-generating device in school classrooms, and noticed
an important finding about the absenteeism of schoolchildren. The emerging threat of an influenza pandemic
that may be spread rapidly by air travel is currently aserious global concern. The importance of our finding interms of prevention of the spread of respiratory viral diseases, such as high-virulence avian influenza, in semiclosed areas, such as theaters, hospitals and aircraft, isbriefly discussed.
MATERIALS AND METHODS
A commercially available tabletop ClO2 gas-generating device*Corresponding author. E-mail: nogata7@yahoo.co.jp.

(Cleverin G, a canister of 150 g active ingredients) was used. The
ingredients of the device are sodium chlorite (NaClO2), sodiumdihydrogenphosphate (NaH2PO4), sodium salt of polyacrylic acidand water. The device releases gaseous ClO2 in a sustainedmanner. Three of these devices were placed in a classroom with
65-m2 floor area (230-m3 volume) and 34 schoolchildren for use asa deodorant. According to the manufacturer, the concentration of
ClO2 becomes 0.01-0.03 ppm in a classroom of this volume whenthat number of units is used. The data were collected from anelementary school with schoolchildren of 6-12 years old and withalmost equal numbers of girls and boys. The statistical evaluation of
the difference in the rate of absenteeism between two groups(schoolchildren in classrooms with or without the ClO2 devices) wasdone by a χ2 test, and the difference was considered significant at p
< 0.05.

RESULTS AND DISCUSSION
When we used the device in a school classroom, wefound retrospectively during the period of 38 consecutive
school days that the rate of absenteeism (number ofabsent schoolchildren divided by a nominal number ofschool children in that particular classroom) during theperiod of 38 consecutive school days (from January toMarch) appeared lower in the classroom where the ClO2
devices were placed compared to that in the classrooms
where such devices were not placed (Figure 1). However,it was statistically unclear from Figure 1 whether theOgata and Shibata

Figure 1. Rates of absenteeism of school children. Rates ofabsenteeism (number of absent schoolchildren divided by anominal number of school children in that particular classroom) in classrooms where ClO2 gas-generating devices(Cleverin G) were (filled circles, one classroom) or were not(open circles, 17 classrooms) placed are shown.

Table 1. Cumulative numbers of schoolchildren present
or absent from school.

Cumulative no. of school children
ClO2 device
PresentAbsent
Placed1272 (98.5%)
20 (1.5%*)
Not placed
21634 (96.0%)
900 (4.0%*)
Numbers represent cumulative numbers of schoolchildren inclassrooms with (one classroom) or without (17 classrooms)
ClO2 devices who were present or absent from school during
38 consecutive school days. *Significantly different (p <0.00001, χ2 test).

289

which a classroom where a ClO2 device was placed isstudied again without the device with the same
population of children.
The effect of the device on the lower rate of absentteeism appears to be due to the ClO2 gas released fromthe device, since the only volatile materials released fromthe device are ClO2 and water. Respiratory viral diseases,
such as high-virulence avian influenza, are major publichealth concerns worldwide (Ginsberg et al., 2009). Due tothe potential for rapid spread of such diseases via airtravel, they could immediately result in pandemics withmillions of fatalities. However, at present there are almost
no effective countermeasures against such devastating
infectious diseases in semi-closed areas, such as aircraft,tramcars and school classrooms. Judging from the known
virucidal activity of ClO2 (Zoni et al., 2007), our unexpected and retrospectively observed finding in school
suggests the possible usefulness of extremely low-concentration ClO2 gas to prevent the spread of respiratory
viral diseases without necessitating evacuation. Basedupon the serendipitous observation in a school, we conclude that ClO2 gas at an extremely low concentration
could potentially prevent diseases, such as respiratory
infections, in semi-closed areas. Large-scale prospective
studies based upon a solid methodology would beneeded to substantiate our important observation.
ACKNOWLEDGMENT
We thank Shigeo Asada for his valuable contribution tothis work.
REFERENCES

difference in the rate of absenteeism between the twogroups was significant. Therefore, we calculated cumulative numbers of schoolchildren present or absent fromschool based upon the above data by summing up thedaily number of schoolchildren present or absent for theentire 38 school days (Table 1).
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