Asian Journal of atmospheric environment
[ Research Article ]
Asian Journal of Atmospheric Environment - Vol. 4, No. 3, pp.157-165
ISSN: 1976-6912 (Print) 2287-1160 (Online)
Print publication date 31 Dec 2010
Received 08 May 2010 Accepted 14 Oct 2010
DOI: https://doi.org/10.5572/ajae.2010.4.3.157

Indoor and Outdoor Air Quality and Its Relation to Allergic Diseases among Children: A Case Study at a Primary School in Korea

Ho-Hyun Kim ; Chang-Soo Kim1) ; Young-Wook Lim ; Min-A Suh1) ; Dong-Chun Shin1), *
The Institute for Environmental Research, Yonsei University College of Medicine, Seoul, Korea
1)Department of Preventive medicine, Yonsei University College of medicine, Seoul, Korea

Correspondence to: *Tel: +82-2-2228-1869, E-mail: dshin5@yuhs.ac

Abstract

The purpose of this study is to investigate allergic diseases related to allergy caused by the exposure to indoor and outdoor sources of air pollution in primary schools. The symptoms questionnaire of allergic diseases based on the International Study of Asthma and Allergies in Childhood (ISAAC) was completed by the participants. The past and present status of asthma, allergic rhinitis, eczema, and allergic conjunctivitis were investigated by providing a questionnaire to all the participating children. Questionnaires were sent to a total of 61,350 children from 438 primary schools. A total of 40,522 children responded to the questionnaire, which represents a 66.1% return rate. Volatile Organic Compounds (VOCs), Aldehydes, and Particulate Matter (PM10) were measured and analyzed from October to December of 2006, in 82 primary schools. The final study population comprised 35,168 children with complete data which excluded incomplete questionnaire responded by 5,354 children. Based on the survey, the level of indoor air contamination did not appear to be high, but 27.2% of the schools evaluated had exceeded the PM10 level specified by the school health guidelines (100 μg/m3). The overall mean concentration of formaldehyde was 22.07 μg/m3 and 1.0% of schools (1 school) exceeded the 100 μg/m3. Statistically significant relationships have been observed between indoor air quality and prevalence rate of allergic rhinitis and conjunctivitis of primary schools in Korea.

Keywords:

Allergic diseases, ISAAC, Primary school children, VOCs, Aldehydes, PM10

1. INTRODUCTION

In the International Study of Asthma and Allergies in Childhood (ISAAC) research report, the highest asthma prevalence occurred in industrialized and westernized countries (Ho et al., 2007). For young individuals, schools represent the environment where they pass a substantial portion of the day (Silvers et al., 1994). Other studies confirm that indoor air quality in schools is far from what may be characterized as a “healthy microenvironment” (Siskos et al., 2001; Hirsch et al., 1999; Knox et al., 1997). A number of studies have revealed that school air may be a source of a wide spectrum of air pollutants, such as VOCs, etc (Braniš et al., 2005).

Asthma is a chronic inflammatory disorder of the airways characterized by episodes of recurrent wheezing, shortness of breath, chest tightness, and cough (Downs et al., 2001). Atopic dermatitis (AD), a common chronic inflammatory skin disease, is one of the most common disorders in children (Lee et al., 2001). Currently, allergic diseases are considered to be related to environmental problems. These are associated with “problem buildings” caused by moving into new buildings, and “Sick School Syndrome” caused by contact with chemical substances in newly built school. These syndromes develop primary school students who spend most of the day in primary school area were easy to develop a symptoms so-called “sensitive group”. Recurrent sneezing due to viral infection has potential to cause sickness in many preschool children, but may not necessarily represent a respiratory symptom. Especially when there is no medical or family history of asthma or eczema, these situations are known as ‘viral-induced’ sneezing episode. These symptoms are different from those in children with asthma since acute symptoms occurring by certain interval may be related to exercise, environmental stimuli (such as pollen, smoke, and air pollution) and contact with animals (Strachen and Gerritsen, 1996).

Increased exposure to air polluting substances arising from both indoors and outdoors, such as particulate matter (PM10), Volatile Organic Compounds (VOCs), Formaldehydes (HCHO), Ozone (O3), Nitrogen dioxides (NO2) and the emission gases of diesel vehicles along with increased time spent indoors have increased the risk of exposure to various antigens (Ho et al., 2007). This is also thought to be a major reason for the increasing incidence of asthma, pulmonary and allergic diseases (Breysse et al., 2005; Nielsen et al., 2005; Delfino, 2002; Nielsen et al., 2002; Pandya et al., 2002). An increased prevalence of allergic diseases has been found in urban areas of industrialized countries that experience heavy traffic (Brunekreef et al., 1997; Weiland et al., 1994). Moreover, increasing allergic sensitization is being detected in individuals living in heavily polluted areas (Nicolai et al., 2003; Wyler et al., 2000; Popp et al., 1989). According to a 5-year investigation of allergic diseases conducted by the Korean Academy of Pediatric Allergy and Respiratory Diseases since 1995, the asthma prevalence rate in primary school students has increased from 7.7% (25,361 tested) in 1995 to 9.1% (28,050 tested) in 2000 (MOHW, 2005).

The aim of this study is to determine the effect of school indoor air quality to the allergic diseases of primary school children through the analyses of various chemical substances.


2. METHODS

2. 1 Study Subjects

Data on geographic area and number of students of all primary schools (n=6,279) in 2006 were acquired from ministry of education, science and technology (MEST) of the Republic of Korea.

We exclude [Closed school] or [Temporarily closed school] in 2006 and remote island such as Jeju. Remaining schools were separated based on the ratio of [Metropolitan city]-[Mid to small city]-[Other Gun, Myun, and Eup]. Randomized sample selection criteria were described as follows: 1) school with more than 100 students (i.e. more than three classrooms), 2) private schools included unconditionally since most Korean schools are national or public schools; and 3) determine the ratio of [Metropolitan city]-[Middle sized city]-[Other Gun, Myun, and Eup]. After the initial round of selection, the following two conditions were evaluated: Inclusion of more than 70 primary schools near major industrial complexes around the nation, and the time of school was built ([2-5 years], [6-10 years], [11-20 years], [More than 21 years]). Among selected primary schools, 3rd, 4th, and 5th grade students mainly participated to the survey.

Letters of invitation, informed consent, and ISAAC questionnaires were mailed to 61,350 children from October through November 2006. All mailing contents were administered to the parents of the children. Among 61,350 subjects of 443 primary schools, a total of 40,522 (66.1%) of 438 primary schools responded the mailing survey.

2. 2 Sampling and Analysis

Among the schools that participated in the first survey, 82 primary schools were selected according to the school selection criteria. The detailed sample selection criteria for the investigation of indoor environmental status were 1) school size with more than 100 students (Namely, more than 3 classrooms), 2) private schools are included unconditionally, 3) considering the ratio of [Metropolitan city]-[Middle sized city]-[Other Gun, Myun, and Eup], 4) evaluating the adequacy of following two conditions after sampling in case of unsatisfaction, 5) Inclusion of more than 10 primary schools near major industrial complexes around the nation, 6) Considering the establishment year of schools as the ratio of [School built year], [2-5 years], [6-10 years], [11-20 years], [More than 21 years].

The standardized as well as widely adopted International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was utilized to investigate the history and prevalence rate of allergic disease such as asthma, atopy dermatitis, allergic rhinitis and conjunctivitis (Lee et al., 2001; ISAAC Steering Committee, 1998; Asher et al., 1995). In this study, Korean version of ISAAC questionnaire for asthma following the guidelines suggested by ISAAC was used. Detailed characteristics of the Korean version of ISAAC questionnaire have been reported previously (Yeon et al., 2005; Oh et al., 2003).

In addition, questions on living environment such as monthly electricity bill (as a proxy indicator of socio-economic status), residence type, age of building, and history of moving to new house were added. The questionnaires were distributed to each school, and students were advised to fill out the questionnaire with the help of parents.

This study was approved by the Ethics Committee of Yonsei University, College of Medicine and informed consent was obtained from all the parents and principals of primary schools.

The analysis of indoor air was conducted between October and December of 2006 from the final group of selected primary schools. Measurements were taken in classrooms, hallways, and the outdoors. Aldehydes (1 hr) (Formaldehyde, Acetaldehyde), VOCs (1 hr) (Benzene, Toluene, Ethylbenzene, Xylene), and PM10 (8 hr) were quantified from each locations. Sampling was performed during class hours, and the classrooms examined were notified not to allow ventilation on the day of sample collection. Five repeated recovery ratios of VOCs and aldehyde were averaged, which resulted 85 to 110% satisfactorily.

2. 3 Statistical Analysis

For the analyses, we excluded 5,354 children whose data was uncompleted. The final study population comprised 35,168 children with complete data. Data were analyzed by residential regions which were four regions (Rural/Industrial complex/Metropolitan/Middle-sized cities). The difference of allergic disease by regional communities and multiple group comparison analysis was conducted using ANOVA. T-test was performed to compare the aldehydes, VOCs and PM10 level of two groups (case and control) and a p-value less than 0.05 was considered statistically significant. All statistical analyses were performed using the SAS 9.1 statistical package.


3. RESULTS AND DISCUSSION

3. 1 Prevalence of Allergic Diseases

The survey was separated into four regions: rural, industrial complexes, metropolitan cities, and middle-sized cities. The house types were most apartments (above 60%) and there were single and multi-detached houses. Houses were for the most part constructed more than 5 years ago (above 70%). Overall, 30% contained indoor-smoker. In addition, a higher proportion of households had ventilation (above 95%). Average ventilation was 1-2 times per day. The ratio of girl (56%) was slightly higher than boy (44%).

The distribution of allergic diseases is provided in Table 1. For asthma, 10.8% of students responded to have symptoms of wheezing; whereas only 9.3% students in rural regions reported wheezing symptoms since birth. The overall percentage of students diagnosed with asthma was 7.7%. The children from rural regions demonstrated the lowest ratio for prevalence of diagnosed with asthma for lifetime (6.5%) compared to industrial complexes (8.9%), metropolitan cities (8.0%), and middle-sized cities (7.7%). The prevalence of asthma increased from 7.7% in 1995 to 9.1% in 2000 (Hong et al., 2004). It is, however, important to note that the variation may arise in the survey due to the use of different institutions compromising students with different age distribution at 1-6 grades.

Prevalence of symptoms of allergic diseases.(Unit: person (%))

The overall lifetime prevalence of allergic rhinitis was 39.5%. Industrial complex regions had a higher 12-month prevalence rate of rhinitis (38.4%) than other regions while the lowest number of students from rural regions (27.1%). In rural regions, both the number of students diagnosed and showed symptoms of rhinitis in the past year was lower compared to other regions. Rhinitis symptoms which included sneezing, congestion and nose itching, appeared most frequently in March, April (spring), and September, October (fall), (data not shown). Congestion (23.6%) was the most prevalent rhinitis symptom and 12.9% of the symptoms were found to be itching at the nose (data not shown).

Allergic conjunctivitis showed a similar pattern, as other diseases, having the lowest occurrence in students who experienced the conjunctivitis symptoms once during their lifetime or during the last one year in rural regions. Moreover, 19.3% of students were diagnosed with allergic conjunctivitis.

The overall lifetime prevalence of eczema symptom was 22.1%, while the overall 12-month prevalence of eczema was 16.4%. Rural regions had a lower prevalence rate of diagnosed with eczema (21.1%) than other regions.

3. 2 Indoor Air and Outdoor Quality of Primary Schools

The indoor air results for the classrooms, hallways, and outdoor areas of primary schools around the country are summarized in Table 2.

Concentration of target compounds.(Unit: μg/m3)

The overall mean concentration of formaldehyde was 22.07 μg/m3 and 1.0% of schools (1 school) exceeded the 100 μg/m3 of “The maintenance and management guideline for air quality within school buildings” recommended by the environmental health law’s enforcement regulation under the Ministry of Education and Human Resources Development.

The VOCs and Aldehyde concentration revealed a decreasing trend from the indoor classroom, hallway to outdoor classroom. The overall mean concentration of acetaldehyde was 12.77μg/m3. However, the indoor air-related guidelines for acetaldehyde have not yet been established school in Korea.

Individual VOCs have not yet been designated under the environmental health law of the Ministry of Education and Human Resources Development. Instead, the Ministry of Environment’s public facilities guideline was applied. According to these guidelines, 17 to 27% of tested schools have exceeded given level of benzene, toluene, and xylene; whereas, ethylbenzene and styrene were found to meet the guideline (Table 2).

The indoor and outdoor VOCs concentration in primary schools located in Seoul, Gyeonggi, and Incheon were higher than primary schools in other areas (regional communities, Eup, Myun units). It is likely that the contamination at these schools is the result of industrial activities and high traffic volume. The occurrence and concentrations of VOCs in homes can be affected by outdoor atmospheric conditions, indoor sources, indoor volume, human activities, ventilation rates, and seasonal factors. Furthermore, VOC concentration can vary due to temperature changes, and humidity (Van der wal et al., 1997). A number of investigators have demonstrated that the indoor concentrations of VOC in dwellings are usually higher than outdoor concentration (Jo et al., 2004; Wilson et al., 1993; Sheldon et al., 1991).

This result is possibly due to the influence of other unidentified sources of VOCs from the industrial complex and indoor. The ratio of the indoor (I) to the outdoor (O) air concentration of different compounds, i.e. the I/O value, reflects the importance of outdoor versus indoor sources even better than the absolute concentration (Ilgen et al., 2001). This study could be interpreted as an indication of weak indoor sources (I/O values are greater than 1) for this compound (Table 2).

However, the mechanisms by which fine particulate and the other traffic-related pollutants might influence allergen handling by the individual and promote allergic sensitisation and morbidity can be only hypothesised. Diesel particles have been shown to enhance inflammatory reactions and sensitization (Mastrangelo et al., 2003). Like many other industries, the dyeing industry is associated with VOCs emissions from the solvents employed in the dyeing and finishing processes( Wicks Jr. et al., 1994). Of course, other unidentified potential VOC sources could still complicate the distance factor from the nearby roadway and school.

3. 3 Relationship between Indoor Air Quality and Environmental Disease

In this study, only the survey data obtained from schools were utilized to determine the relationship between the indoor air quality and environmental diseases (Tables 3-5). The ISAAC survey results were based on 80 schools since the overall results showed similar patterns (data not shown).

Analysis of indoor air value of school with asthma and atopy dermatitis.(Unit: μg/m3)

Analysis of indoor air value of school with allergic rhinitis and conjunctivitis.(Unit: μg/m3)

Analysis of indoor air value of school with asthma and atopy dermatitis.(Unit: μg/m3)

80 primary schools were divided into the upper and lower 40 primary schools with a higher and lower ratio of children who had allergic disease symptoms for the past year. Schools with a higher and lower ratio of students who had symptoms of asthma and atopic dermatitis last year did not have significantly different concentration of aldehydes (formaldehyde and acetaldehyde), VOCs (benzene, toluene, ethylbenzene, xylene), or PM10.

Depending on the measurement site (indoor, hallway, outdoor), the concentration showed expected trend between the upper and lower 40 schools. Good air quality in classrooms and hallways benefits children in their learning ability, helps keep teachers and staff productive, and also is beneficial to their health (Mendell and Heath, 2005; USEPA, 1996). Nevertheless, the variance of each measured concentration was large; thus revealing no statistically significant differences in the concentrations of substances between the upper and lower schools (Table 3). Four volatile organic compounds (BTEX) had higher concentrations in the upper 40 schools. The concentrations of these four materials were also significantly different between classrooms and hallways (p<0.05). In other words, schools where many students had allergic rhinitis symptoms in the prior year had higher concentrations of VOCs compared to schools where fewer students had allergic rhinitis symptoms. Concentration of particulate matter was higher in schools where majority of students showed allergic symptoms. However, significant differences were only found in the indoor and outdoor environment (Table 4).

Indoor formaldehyde and PM10 levels in classroom were significantly (p<0.05) higher in schools with high proportion of allergic conjunctivitis compared to schools with lower proportion. The concentrations of other substances were also higher at schools where many children had allergic conjunctivitis symptoms, but this difference was not significant. Only PM10 measured outdoors was significantly (p<0.05) different between the upper and the lower 25% schools (20 schools). The concentration of contaminant in the air for the upper 25% of schools was higher than the concentration at the lower 25% of schools (Table 5).

Previous studies have shown that air pollutants related to vehicles can stimulate allergies (D’Amato et al., 2000; Takenaka et al., 1995). In vitro experiment of Gilmour (Gilmour, 1995) also demonstrated that diesel combustion substances could increase immunoglobulin E (IgE) levels. These associations reflect the shared inflammation process underlying allergic rhinitis and asthma, and potentially explain the frequent co-existence of these disorders. These findings may be the result of an unhealthy environment at public schools, as well as different socio-economic status leading to diverse behavioural and environmental factors(ISAAC Steering Committee, 1998; Venn et al., 1998).

It is worth noting that these allergic diseases can result not only from exposure to indoor/outdoor harmful chemical substances, but also from exposure to micro-organisms, house dust mites, and fungi (Nafstad et al., 2005; De Marco et al., 2004). In addition, lifestyle factors such as dietary habits, breast feeding, atopy heritability, month of birth, parent smoking, and sex have all been reported to play an important role in causing allergic sensitivity (Ford, 2005; Monteil et al., 2004; Sly, 1999; Tariq et al., 1998). Because this study analyzed cross-sectional data, it cannot be determined whether the onset of allergy disease followed the onset of indoor air quality. Prospective data are needed to determine if such an association is causal and if there is a time frame during which a child is at increased risk for the development of allergic disease.

Causal associations cannot be assumed in this cross-sectional analysis. A further prospective investigation of the effect of social-economic status among children would be needed. In addition, numerous hypotheses relating to family size, early childhood infections and hygiene, allergen exposure, diet and obesity, and pollution may be involved (Hong et al., 2004).

The concentration results of tested substances used at the current study are the measurement data which did not reflect the various properties of school space. There are limitations of result interpretation. But in the selection of subjected schools, the schools where can represent the characteristics of the selected regions were selected, and made efforts to complement the representativeness by measuring the indoor, hallway and outdoor sites of 80 schools.


4. CONCLUSIONS

The International Study of Asthma and Allergies in Childhood (ISAAC) was previously developed to provide an acceptable method of measuring the prevalence of asthma and other atopic diseases in children (Weiland et al., 2004). In this study, prevalence of asthma was found to be 8.0% (40,522 tested). The prevalence of asthma increased from 2.7% in 1995 to 5.3% in 2000. The awareness of asthma by doctors and/or patients and their parents may have increased over this period of time, explaining, at least in part, the increased prevalence of asthma in South Korea (Hong et al., 2004).

This study revealed a trend for higher contaminating substance concentrations at schools with higher number of children with allergic symptoms (“upper schools”) compared to schools with fewer reported allergic symptoms (“lower schools”). The study showed no statistically significant differences between the upper and lower school for many of the contaminants due to the large variance. The case was different for most VOCs, in which significantly higher concentrations (p<0.05) have been found in the upper 40 schools compared to the lower 40 schools. Similarly, schools with many students with allergic rhinitis and conjunctivitis showed high concentrations of PM10. It is predicted that use of first round of measurement data and inconsideration of characteristic features of each school space may have limited the interpretation of the results. However, an effort was made to select schools that are representative of particular regions. Samples were also taken from three different areas (indoors, hallways, and outdoors) of schools. whereas cross-sectional allergical studies did not find a relationship between indoor air test performance and duration of disease prevalence.

In addition, long-term follow-up studies should be carried out to investigate related factors even after controlling for potential confounding factors such as age, sex, birth weight, breastfeeding, parental asthma, passive exposure to smoke, socioeconomic status of environmental diseases in school-aged children.

Acknowledgments

This study has been supported (2007) by the Ministry of Education, Science and Technology. We thank the parents and children who have willingly participated in this study.

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Table 1.

Prevalence of symptoms of allergic diseases.(Unit: person (%))

Total (N=35168) Rural (N=6725) Industrial complex (N=3318) Metropolitan cities (N=13621) Middle sized cities (N=11504) p-valuea
aANOVA test
Asthma
Symptom lifetime 3640 (10.8) 597 (9.3) 382 (12.0)* 1508 (11.4) 1153 (10.5) <0.0001
Symptom-last 12 months 1669 (4.9) 296 (4.6) 187 (5.9)* 660 (5.0) 526 (4.8) <0.0001
Diagnostic lifetime 2709 (7.7) 437 (6.5) 294 (8.9)* 1093 (8.0) 885 (7.7) <0.0001
Treatment, last 12 months 891 (2.5) 156 (2.3) 102 (3.1) 355 (2.6) 278 (2.4) 0.1068
Allergic rhinitis
Symptom lifetime 13588 (39.5) 2150 (32.8) 1420 (43.8)* 55595 (41.8) 4423 (39.3) <0.0001
Symptom-last 12 months 11703 (34.0) 1774 (27.1) 1246 (38.4)* 4866 (36.4) 3817 (33.9) <0.0001
Diagnostic lifetime 9926 (28.2) 1326 (19.7) 1090 (32.9)* 4237 (31.1) 3273 (28.5) <0.0001
Treatment, last 12 months 7597 (21.6) 1029 (15.3) 874 (26.3)* 3179 (23.3) 2515 (21.9) <0.0001
Eczema
Symptom lifetime 7608 (22.1) 1170 (17.8) 843 (26.0)* 3114 (23.3) 2481 (22.0) <0.0001
Symptom-last 12 months 5637 (16.4) 855 (13.0) 629 (19.4)* 2305 (17.2) 1848 (16.4) <0.0001
Diagnostic lifetime 10028 (28.5) 1419 (21.1) 1086 (32.7)* 4220 (31.0) 3303 (28.7) <0.0001
Treatment, last 12 months 4893 (13.9) 774 (11.5) 545 (16.4)* 1940 (14.2) 1634 (14.2) <0.0001
Allergic conjunc-tivitis
Symptom lifetime 6327 (18.4) 979 (15.0) 690 (21.3)* 2586 (19.4) 2072 (18.4) <0.0001
Symptom-last 12 months 4816 (14.0) 699 (10.7) 549 (17.0)* 1999 (15.0) 1569 (13.9) <0.0001
Diagnostic lifetime 6778 (19.3) 901 (13.4) 825 (24.9)* 2813 (20.7) 2239 (19.5) <0.0001
Treatment, last 12 months 4076 (11.6) 546 (8.1) 505 (15.2)* 1673 (12.3) 1352 (11.8) <0.0001

Table 2.

Concentration of target compounds.(Unit: μg/m3)

Compound Classroom (N=80) Outdoor (N=80) Hallway (N=80) I/O ratio Over value rate (%) Reference value
Mean±S.D (Min-Max) Detection rate (%) Mean±S.D (Min-Max) Detection rate (%) Mean±S.D (Min-Max) Detection rate (%)
aSchool hygiene regulation guideline
bPublic facilities guideline under uncontrolled Korea-IAQ regulation
Formaldehyde 22.07±15.62 (1.12-107.14) 100 6.12±7.26 (N.D-49.21) 91 10.52±7.11 (N.D-37.21) 99 3.6 1.2 100a
Acetaldehyde 12.77±17.61 (1.59-121.06) 100 6.12±7.26 (N.D-85.55) 94 10.52±7.11 (1.06-89.39) 100 1.1 - -
Benzene 14.03±19.38 (N.D-96.64) 96 11.59±15.58 (N.D-68.28) 90 12.88±16.34 (N.D-73.82) 93 1.2 17 30b
Toluene 81.17±110.61(N.D-816.47) 97 52.99±66.99 (N.D-261.53) 97 74.82±87.33 (N.D-534.20) 99 1.5 2.6 260b
Ethylbenzene 28.33±38.51 (N.D-158.58) 95 19.27±30.14 (N.D-116.79) 96 24.49±32.32 (N.D-125.33) 96 1.4 0.0 1000b
Xylene 50.15±70.74 (N.D-268.74) 87 30.94±50.39 (N.D-191.94) 82 46.04±67.59 (N.D-384.69) 91 1.6 24 100b
Styrene 9.95±25.14 (N.D-150.58) 64 3.86±9.80 (N.D-61.40) 59 6.37±15.21 (N.D-87.79) 64 2.6 0 260b
PM-10 88.06±54.47 (9.70-358.33) 100 63.91±41.31 (12.50-179.17) 100 84.32±53.66 (N.D-280.15) 98 1.4 27 100a
MTBE 2.18±5.63 (N.D-32.97) 23 3.46±9.17 (N.D-46.12) 26 1.28±2.90 (N.D-15.33) 25 0.6 - -

Table 3.

Analysis of indoor air value of school with asthma and atopy dermatitis.(Unit: μg/m3)

Asthma Atopy dermatitis
Case school (n=40) Control school (n=40) p-valuea Case school (n=40) Control school (n=40) p-valuea
aT-test
Formaldehyde-Classroom 22.61±17.9 22.06±13.4 0.8806 24.64±11.5 19.87±19.3 0.1968
Formaldehyde-Hallway 10.34±6.7 10.99±7.8 0.6945 11.69±6.5 9.54±7.8 0.1924
Formaldehyde-Outdoor 5.63±4.6 6.92±9.5 0.4568 5.92±5.3 6.60±9.2 0.6953
Acetaldehyde-Classroom 12.20±20.5 12.49±17.7 0.9468 13.47±17.8 11.15±20.5 0.5947
Acetaldehyde-Hallway 8.27±11.7 12.59±20.2 0.2551 11.28±16.5 9.42±16.5 0.6192
Acetaldehyde-Outdoor 10.42±18.9 12.95±21.6 0.5838 9.55±16.6 13.86±23.4 0.3537
Benzene-Classroom 11.84±16.7 16.22±21.8 0.3276 12.20±18.0 15.76±20.6 0.4278
Benzene-Hallway 11.57±15.5 14.12±17.2 0.4998 11.88±15.9 13.88±16.8 0.5956
Benzene-Outdoor 13.76±19.0 9.37±10.8 0.2293 11.58±16.4 11.61±14.9 0.9926
Toluene-Classroom 92.05±140.9 70.29±68.4 0.3960 72.61±69.0 89.30±139.6 0.5083
Toluene-Hallway 82.42±103.1 67.60±69.8 0.4681 64.73±68.1 84.90±103.1 0.3179
Toluene-Outdoor 62.82±76.3 42.89±55.1 0.2061 48.93±68.8 57.16±65.7 0.6033
Ethylbenzene-Classroom 26.33±36.2 30.33±41.0 0.6534 28.87±40.4 27.81±37.2 0.9052
Ethylbenzene-Hallway 23.32±28.7 25.59±35.7 0.7611 22.92±30.2 26.05±34.6 0.6757
Ethylbenzene-Outdoor 23.57±34.3 14.85±24.9 0.2191 19.02±32.7 19.53±27.7 0.9440
Xylene-Classroom 41.09±55.9 59.44±83.0 0.2546 45.35±66.2 55.07±75.7 0.5449
Xylene-Hallway 44.57±70.3 47.54±65.6 0.8463 37.64±48.8 54.65±82.4 0.2701
Xylene-Outdoor 36.56±55.4 25.18±44.6 0.3188 30.06±51.8 31.84±49.5 0.8764
PM10-Classroom 89.32±39.9 87.37±68.3 0.8790 94.46±58.5 81.95±51.6 0.3207
PM10-Hallway 92.14±59.2 75.20±45.9 0.2605 90.78±47.9 74.79±61.2 0.2964
PM10-Outdoor 68.91±42.2 58.07±40.3 0.3508 71.81±45.2 52.24±32.3 0.0941

Table 4.

Analysis of indoor air value of school with allergic rhinitis and conjunctivitis.(Unit: μg/m3)

Allergic rhinitis Allergic conjunctivitis
Case school (n=40) Control school (n=40) p-valuea Case school (n=40) Control school (n=40) p-valuea
aT-test
Formaldehyde-Classroom 23.87±18.4 20.86±12.8 0.4105 25.74±18.2 18.67±11.9 0.0460
Formaldehyde-Hallway 11.70±6.0 9.63±8.1 0.2083 10.97±5.2 10.32±8.9 0.7000
Formaldehyde-Outdoor 5.91±4.4 6.58±9.5 0.6948 7.22±8.5 5.19±5.9 0.2250
Acetaldehyde-Classroom 13.96±21.8 10.72±16.0 0.4559 15.61±24.8 8.90±9.2 0.1167
Acetaldehyde-Hallway 11.42±17.5 9.33±15.4 0.5772 11.83±17.1 8.84±15.8 0.4259
Acetaldehyde-Outdoor 12.43±19.9 10.87±20.7 0.7352 11.59±19.8 11.72±20.8 0.9778
Benzene-Classroom 20.01±23.3 8.35±12.5 0.0094 16.79±22.1 11.41±16.2 0.2289
Benzene-Hallway 18.81±19.1 6.63±9.6 0.0008 13.71±17.6 12.00±15.1 0.6517
Benzene-Outdoor 15.00±16.9 8.45±13.7 0.0724 13.08±16.7 10.07±14.4 0.4135
Toluene-Classroom 111.00±139.5 52.88±63.2 0.0247 78.57±69.3 83.65±139.9 0.8405
Toluene-Hallway 104.09±96.7 43.97±64.1 0.0021 67.61±61.7 82.41±108.4 0.4706
Toluene-Outdoor 67.55±74.6 39.58±56.8 0.0744 52.58±64.8 53.41±70.1 0.9584
Ethylbenzene-Classroom 40.33±42.3 16.94±30.9 0.0073 35.92±43.5 21.12±31.9 0.0941
Ethylbenzene-Hallway 36.05±35.7 12.29±23.1 0.0009 27.93±35.3 20.86±28.9 0.3434
Ethylbenzene-Outdoor 26.89±32.8 12.25±25.9 0.0371 21.62±31.3 16.86±29.2 0.5034
Xylene-Classroom 63.47±70.9 36.49±68.8 0.0902 59.49±78.5 40.57±61.3 0.2371
Xylene-Hallway 68.36±76.5 23.14±47.9 0.0024 48.05±57.5 43.97±77.3 0.7901
Xylene-Outdoor 41.76±54.7 19.84±43.5 0.0526 34.91±52.9 26.86±48.0 0.4813
PM10-Classroom 98.56±70.6 77.64±29.2 0.0906 103.63±70.5 72.29±24.2 0.0108
PM10-Hallway 95.27±49.3 68.16±56.3 0.0735 102.39±55.9 59.69±39.7 0.0036
PM10-Outdoor 74.37±46.9 48.46±24.9 0.0130 76.31±48.3 46.99±20.1 0.0047

Table 5.

Analysis of indoor air value of school with asthma and atopy dermatitis.(Unit: μg/m3)

Asthma Atopy dermatitis
Case school (n=20)a Control school (n=20)b p-valuec Case school (n=20)a Control school (n=20)b p-valuec
aLevel highest 25%, bLevel lowest 25%, cT-test
Formaldehyde-Classroom 27.73±22.5 17.32±9.8 0.0705 24.77±11.6 19.09±13.8 0.1764
Formaldehyde-Hallway 12.08±7.3 10.95±8.2 0.6499 10.96±4.9 9.77±9.0 0.6201
Formaldehyde-Outdoor 6.41±5.6 6.90±11.7 0.8708 5.56±3.4 6.67±7.5 0.5680
Acetaldehyde-Classroom 16.88±28.3 7.81±3.8 0.1712 9.63±3.6 9.68±13.1 0.9875
Acetaldehyde-Hallway 11.17±15.9 6.48±4.1 0.2152 8.30±10.7 5.27±3.7 0.2452
Acetaldehyde-Outdoor 11.16±20.7 7.74±14.0 0.5521 7.98±13.3 10.59±20.3 0.6388
Benzene-Classroom 12.98±19.3 11.72±12.9 0.8165 12.62±19.2 9.05±11.4 0.4914
Benzene-Hallway 12.87±16.6 10.73±13.4 0.6635 10.80±15.5 9.43±10.9 0.7590
Benzene-Outdoor 12.52±16.5 9.74±11.3 0.5558 9.88±14.0 7.19±7.5 0.4822
Toluene-Classroom 69.71±75.2 70.03±67.5 0.9892 77.75±66.0 101.85±183.0 0.5946
Toluene-Hallway 63.04±59.8 62.77±62.6 0.9889 58.88±59.5 94.17±133.0 0.3126
Toluene-Outdoor 61.22±79.5 52.35±58.5 0.7026 54.93±70.6 48.22±62.5 0.7683
Ethylbenzene-Classroom 29.16±42.5 26.54±36.0 0.8404 34.72±42.9 13.38±21.6 0.0636
Ethylbenzene-Hallway 21.89±24.6 20.22±33.3 0.8616 20.58±23.9 17.93±26.8 0.7518
Ethylbenzene-Outdoor 21.53±30.3 15.34±24.2 0.4987 16.74±27.2 11.99±22.2 0.5756
Xylene-Classroom 42.21±59.4 63.69±92.3 0.3905 53.46±68.5 26.12±42.1 0.1407
Xylene-Hallway 39.96±44.0 40.47±69.4 0.9779 34.91±39.8 42.57±91.2 0.7391
Xylene-Outdoor 34.09±48.6 26.50±46.2 0.6202 26.36±42.0 18.93±39.0 0.5709
PM10-Classroom 89.39±45.9 83.62±65.5 0.7536 98.08±45.0 73.35±29.5 0.0556
PM10-Hallway 82.57±44.3 56.51±21.8 0.0577 96.41±49.4 71.34±47.3 0.2237
PM10-Outdoor 66.75±37.4 42.64±18.5 0.0391 85.66±50.8 41.43±19.6 0.0043