Indoor/outdoor relationship of fine particles less than 2.5 μm (PM2.5) in residential homes locations in central Indian region
Introduction
Assessment of the risk, to the community resulting from exposure to airborne pollutants should ideally include measurements of concentration levels of the pollutants in all microenvironments where people spend their time. Due to the multiplicity of different microenvironments, it is usually, however, not possible as it is too expensive to conduct measurements in all of them [1]. When considering human exposure to airborne pollutants, of particular importance is the exposure to airborne particles and specifically to its fine fractions as these particles have a higher probability of penetration into the deeper parts of the respiratory tract [2] and also contain higher levels of trace elements and toxins [3], [4].
A large number of epidemiological studies have been published, some based on reanalysis of the older results and some on new data sets, have greatly improved the ability to establish health effects from particulate air pollution [5], [6]. Importantly, these studies have emphasized on the importance of small size fraction, which showed no apparent thresholds at lower concentration. A better characterization of the health relevant particle fraction will have major implication for air quality policy since it will determine which source should be controlled [7].
Particulate matter (PM2.5) is the most ubiquitous and most complicated air pollutant, [8] besides health effects, atmospheric fine aerosol particles play an important role in controlling a number of atmospheric processes such as deposition of different compounds, the optical properties etc [9]. It is generated by various sources, fuel combustion processes in transportation and energy production are the primary sources of the outdoor PM2.5, while cooking, smoking and cleaning activities contribute primarily to the indoor PM2.5 levels. Traffic-related fine particles are recognized as an important contributor to outdoor PM2.5 concentrations [10]. The concentration of airborne particles inside a house is governed by the generation of particles within the house, the concentration of particles outside the house, the rate of air exchange and the depositional characteristics of the particles [11]. Most houses in the developing world are naturally ventilated, allowing particles from out-of-doors to readily penetrate the house through given spaces and cracks in the structure [12]. Smoking can add ∼20 μgm−3 (24-h mean) of fine particles per smoker to a household, [13] with short-term peaks of 300 μgm−3 which can persist for up to 30 min after a cigarette is finished [14]. Cooking in some houses generated particles <0.1 μm which accounted for 30% of the particle volume [15]. Particulate matter concentrations were increased by cooking style, [15] especially frying. It was reported that indoor/outdoor ratios were slightly higher in houses with gas cookers than in those without sources [16]. A questionnaire survey is a common way to relate illness prevalence with indoor air quality. Sundell associated different types of ventilation and outdoor-air flow rates with sick building syndromes (SBS) like cough, dry throat, sneezing, asthma and hay fever using a questionnaire survey study [17].
Over the past two decades there has been a rapid increase in urbanization and industrialization in many cities of India. With this has come a dramatic increase in the number of residences, office buildings and manufacturing facilities, together with an increase in both the number and density of motor vehicles. The urbanization process has both positive and negative effects on indoor air quality in many cities of the world [18]. More than 72% of the Indian households according to 2001 census, still use unprocessed biomass as their primary cooking fuel, in rural areas; this figure is approximately 90% [19]. As a result, India bears one of the largest burdens of diseases due to the use of unclean household fuels. According to WHO comparative risk study 28% of all deaths is caused by indoor air pollution (IAP) in developing countries [20]. Many developing countries like India don't have monitoring of fine particles and also no national standards, so a study related to these particles is very necessary as most of the health related adverse effects are associated with the same and short-term study in representative areas for a particular region may overcome the existing problem for policy makers for their judgment and appropriate decision making. Continuing with our earlier studies [21], [22] the main objectives of this study are to provide quantitative information on particulate matter especially fine particles (PM2.5, PM1.0, PM0.50, PM0.25) indoors and outdoors in 14 residential homes located in three different microenvironments, to analyze the relationship between indoor and outdoor particles and identification of the main indoor sources contributing to the elevated fine particulate concentrations. This is the first time we are reporting measurements of particulate mass concentration in this range using real-time measurements.
Section snippets
Site description
Agra, the city of Taj (27°10′N, 78°02′E) is located in the central part of northern India, about 204 km of south of Delhi in the Indian state of U.P. Agra is one of the most famous tourist spots of the country. The city, situated on the west bank of the river Yamuna, is known the world over as home to a wonder of the world, the Taj Mahal. A part of the great northern Indian plains, Agra has a tropical climate. The climate during summer is hot and dry with the temperature ranging from 32° to 48
Indoor/outdoor particulate concentration
All measurements were conducted during the six-month period in Agra (September 2007–March 2008). Temperature, relative humidity and wind speed mean value and range during the measurement period are presented in Table 1.
Fine particulate matter concentration levels were measured inside and outside the homes located in roadside, rural and urban areas of the Agra region. The mean concentration (Table 2) for each site at 15 min interval of 24 h average was calculated along with monthly mean
Conclusion
Based upon the data generated from the questionnaire surveys in 550 houses and sampling in 14 houses, the result obtained suggested that outdoor sources as well as indoor activities influenced the fine particulate concentrations of indoors in houses located in three different types of microenvironments. The average indoor concentrations of PM2.5, PM1.0, PM0.5 and PM0.25 for rural, roadside and urban homes were (173.03 μgm−3, 133.26 μgm−3, 96.02 μgm−3, 8.56 μgm−3), (137.93 μgm−3, 117.09 μgm−3, 68.17 μgm
Acknowledgement
This study was funded by the project no: SR/S4/AS-262/05 of Department of Science and Technology (DST), New Delhi. The authors thank Dr. F.M. Prasad, Principal, St. John's College, Agra and Dr. Ashok Kumar, Head, Department of Chemistry, St. John's College, Agra for providing us the facilities.
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