An assessment of indoor air concentrations and health risks of volatile organic compounds in three primary schools

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Abstract

Concentrations of volatile organic compounds (VOCs), including formaldehyde, in classrooms, kindergartens, and outdoor playgrounds of three primary schools were measured in spring, winter, and fall terms in İzmir, Turkey. A health-risk assessment was conducted for odor detection, sensory irritation, chronic toxic effects, and cancer. Active sampling was applied for VOCs and formaldehyde on Tenax TA and DNPH tubes, respectively. VOCs were analyzed in a thermal desorption–GC–MS system. Formaldehyde analysis was performed using an HPLC instrument. Benzene, toluene, and formaldehyde were the most abundant compounds with 95th percentile indoor air concentrations of 29, 87, and 106 μg/m3, respectively. Naphthalene and xylenes followed them with an order of magnitude lower concentrations. Two isomers of dichlorobenzene (1,3 and 1,4) were the other notable compounds. The concentrations were utilized to classify the indoor air pollutants with respect to potential health effects. In addition, carcinogenic and chronic toxic risks were estimated using Monte-Carlo simulation. Formaldehyde appears to be the most concerning pollutant with high chronic toxic and carcinogenic risk levels according to the health assessment followed by naphthalene, benzene, and toluene due to their chronic effects.

Introduction

Primary schools accommodate children aged 7–14 for about 5–8 h daily, which make them the second most time-spent indoor environment after homes. This implies the importance of the schools in terms of the time component of exposure. The other component, the contaminant concentrations, is also important because volatile organic compounds (VOCs) are ubiquitous in the environment since there are many sources (e.g., traffic and industrial emissions as outdoor sources, building and furnishing materials, arts and crafts materials, cleaning agents, and personal care products as indoor sources) (Sexton et al., 2007, Shendell et al., 2004). There are also other factors that influence indoor air quality: schools are commonly associated with high population density, poor ventilation, lack of maintenance, and unsatisfactory cleaning (Daisey et al., 2003, Smedje et al., 1997). School children are more sensitive to environmental pollutants than adults, because of their higher breathing rate relative to their body size, and continuing growth (Faustman et al., 2000), which translate into higher health-risk levels. Moreover, according to critical reviews, there are studies relating poor indoor environmental quality in schools to the performance of students (Mendell and Heath, 2005), and poor ventilation to health symptoms (Daisey et al., 2003). Some of the VOCs are associated with variety of serious health effects (Sax et al., 2006, Shendell et al., 2004) and symptoms such as asthma and allergic reactions.

Allergic symptoms and diseases are common among children. It has been estimated that there were 6.8 million children with asthma (ALA, 2007) in the US, which was the principal cause of school absenteeism accounting for 20% of lost school days in elementary and high schools (Bayer et al., 2000). Demir et al. (2004) reported the prevalence of asthma in 1992, 1997, and 2002 at a primary school in Ankara, Turkey, as 8.3%, 9.8%, and 6.4%, respectively. In Edirne, Turkey, prevalence of asthma among primary school children was estimated as 5.6%, however 34% of the children experienced an allergy problem at some time in their life (Selcuk et al., 1997). Ones et al. (2005) reported that the prevalence of childhood asthma in Turkey varies between 3.8% and 12.9%. Meanwhile, a recent large-scale survey (more than 25,000 children in 14 cities in Turkey) showed that median prevalence values for asthma, wheezing, allergic rhinitis, and eczema were estimated as 13.4%, 12.6%, 17.3%, and 4.6%, respectively (Kurt et al., 2007).

Formaldehyde, the leading aldehyde in terms of both detection frequency and concentration levels, is considered separately since aldehydes require different sampling and analysis procedures than other VOCs. Norback et al. (1990) studied VOC and formaldehyde concentrations in six classrooms in Sweden. It was reported that, the concentration of formaldehyde was below the detection limit (<10 μg/m3) and the mean indoor Total VOC (TVOC) concentrations ranged from 70 to 180 μg/m3. VOCs were investigated in randomly selected 38 public schools (96 classrooms) by Smedje et al. (1997). Formaldehyde was below the detection limit of 5 μg/m3, the mean sum of 14 identified VOCs was 35 μg/m3, and the highest concentrations were of limonene, n-decane, toluene, and xylene. Lee et al. (2002) measured VOCs in 10 schools with air-conditioned classrooms located in urban, industrial, and residential areas in Hong Kong. Average indoor formaldehyde concentrations did not exceed the standard (100 μg/m3). The most abundant and frequently found VOCs were benzene, toluene, ethybenzene, p/m-xylene, and o-xylene with the mean values of 3.13, 17.7, 4.20, 3.30, and 1.66 μg/m3, respectively. According to a review (Daisey et al., 2003), the average TVOC concentrations ranged from 100 to 1600 μg/m3 in different European and US schools while the mean formaldehyde concentrations in the schools ranged from 10 to 430 μg/m3. The highest median VOC concentrations measured in Minnesota, USA, schools were reported as 4.6, 2.9, and 2.3 μg/m3 for d-limonene, toluene, and m,p-xylene, respectively (Adgate et al., 2004), where winter term concentrations were higher than those measured in spring term. A year long sampling was performed in three primary schools in Western Australia (Zhang et al., 2006). Ten compounds were identified (benzene, toluene, chlorobenzene, m,p-xylene, o-xylene, ethylbenzene, styrene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,4-dichlorobenzene) at low concentrations (TVOC < 100 μg/m3) of which the highest was measured in a visual art classroom. Godwin and Batterman (2007) conducted a study in 64 classrooms in a suburban school district not under the effect of ambient pollution sources in Michigan, USA. The most prevalent VOCs were benzene, ethylbenezene, toluene, xylene, and limonene but the concentrations were low with the mean TVOC level of 58 μg/m3. In general, the literature reported higher indoor, winter, and kindergarten VOC concentrations compared to outdoor, summer, and classrooms, respectively.

Although VOC concentration levels for schools in Turkey (Kocaeli) were reported before (Pekey and Arslanbaş, 2008), the focus was on the homes and offices. This is the first study that focuses on the school indoor air in Turkey, and assesses associated health risks. The aims of the study were to (1) measure VOC concentrations, including formaldehyde, in primary school classrooms, kindergartens, and outdoor playgrounds in fall, winter, and spring terms at three public schools, two located in the urban and one located in suburban İzmir, Turkey, and (2) conduct an assessment to estimate associated human health risks, and to classify the VOCs accordingly.

Section snippets

Site description and sampling

İzmir, the third most populated province in Turkey with a population of approximately four million, is located on the Aegean Sea shore, where the majority of the population (∼70%) resides in the metropolitan area. Three public schools, hereinafter School-1, School-2, and School-3, were selected based on their accessibility, availability, and willingness to participate, as well as their different geographic characteristics and building structure properties. Schools-1 and -2 are in the urban area

Concentrations

Indoor and outdoor VOC concentrations, including formaldehyde, were measured at three primary schools in three seasons (winter, spring, and fall) in İzmir, Turkey. The following sections present results and discussions on indoor concentrations measured in the classrooms and the kindergartens, and outdoor concentrations measured on the playgrounds.

Conclusions

Higher VOC concentrations were measured indoors than outdoors. Seasonal and spatial variations of the most abundant species were not significant, pointing at dominant indoor sources, whereas the effect of outdoor sources cannot be disregarded. Pollutant profiles differed between the kindergartens and the classrooms, and concentrations measured in the kindergartens were higher. Benzene, toluene, and formaldehyde were the most abundant compounds. Naphthalene and dichlorobenzene were the other

Acknowledgments

This study was supported by a research grant (105Y263) from the Scientific and Technical Research Council of Turkey (TUBITAK). GC–MS and HPLC analyses were performed at Environmental Research Center, İzmir Institute of Technology. We thank Dr. M. Odabasi for his help during method development for TD–GC–MS analysis.

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