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For exceptions, permission may be sought for such use through Elsevier’s permissions site at: http://www.elsevier.com/locate/permissionusematerial Science of the Total Environment 381 (2007) 47–58 www.elsevier.com/locate/scitotenv Particulate matter and carbon monoxide multiple regression models using environmental characteristics in a high diesel-use area of Baguio City, Philippines Brandon E. Cassidy a, Mary Anne Alabanza-Akers b, Timothy A. Akers c, ⁎ Daniel B. Hall d, P. Barry Ryan e, Charlene W. Bayer f, Luke P. Naeher a, a The University of Georgia (UGA), College of Public Health, Department of Environmental Health Science, Athens, Georgia, GA 30602-2102, USA b UGA, College of Environment and Design, Athens, Georgia, USA c Kennesaw State University, WellStar College of Health and Human Services, Kennesaw, Georgia, USA d UGA, Franklin College of Arts and Sciences, Department of Statistics, Athens, Georgia, USA e Emory University, Rollins School of Public Health, Atlanta, Georgia, USA f Georgia Tech Research Institute, Atlanta, Georgia, USA Received 12 September 2006; received in revised form 20 February 2007; accepted 2 March 2007 Available online 3 May 2007 Abstract In Baguio City, Philippines, a mountainous city of 252,386 people where 61% of motor vehicles use diesel fuel, ambient particulate matter b2.5 μm (PM2.5) and b10 μm (PM10) in aerodynamic diameter and carbon monoxide (CO) were measured at 30 street-level locations for 15 min apiece during the early morning (4:50–6:30 am), morning rush hour (6:30–9:10 am) and afternoon rush hour (3:40–5:40 pm) in December 2004. Environmental observations (e.g. traffic-related variables, building/roadway designs, wind speed and direction, etc.) at each location were noted during each monitoring event. Multiple regression models were formulated to determine which pollution sources and environmental factors significantly affect ground-level PM2.5,PM10 and CO concentrations. The models showed statistically significant relationships between traffic and early morning particulate air pollution [(PM2.5 p=0.021) and PM10 (p=0.048)], traffic and morning rush hour CO (p=0.048), traffic and afternoon rush hour CO 3 (p=0.034) and wind and early morning CO (p=0.044). The mean early morning, street-level PM2.5 (110±8 μg/m ; mean±1 3 standard error) was not significantly different (p-valueN0.05) from either rush hour PM2.5 concentration (morning=98±7 μg/m ; afternoon=107±5 μg/m3) due to nocturnal inversions in spite of a 100% increase in automotive density during rush hours. Early morning street-level CO (3.0±1.7 ppm) differed from morning rush hour (4.1±2.3 ppm) (p=0.039) and afternoon rush hour (4.5± 2.2 ppm) (p=0.007). Additionally, PM2.5,PM10, CO, nitrogen dioxide (NO2) and select volatile organic compounds were continuously measured at a downtown, third-story monitoring station along a busy roadway for 11 days. Twenty-four-hour average 3 3 ambient concentrations were: PM2.5 =72.9±21 μg/m ; CO=2.61±0.6 ppm; NO2 =27.7±1.6 ppb; benzene=8.4±1.4 μg/m ; ethylbenzene=4.6±2.0 μg/m3; p-xylene=4.4±1.9 μg/m3; m-xylene=10.2±4.4 μg/m3; o-xylene=7.5±3.2 μg/m3. The multiple regression models suggest that traffic and wind in Baguio City, Philippines significantly affect street-level pollution concentrations. 3 3 Ambient PM2.5 levels measured are above USEPA daily (65 μg/m ) and Filipino/USEPA annual standards (15 μg/m ) with concentrations of a magnitudeAuthor's rarely seen in most countries personal except in areas where local topography copy plays a significant role in air ⁎ Corresponding author. Tel.: +1 706 542 2454; fax: +1 706 542 7472. E-mail address: [email protected] (L.P. Naeher). 0048-9697/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2007.03.010 48 B.E. Cassidy et al. / Science of the Total Environment 381 (2007) 47–58 pollution entrapment. The elevated pollution concentrations present and the diesel-rich nature of motor vehicle emissions are important pertaining to human exposure and health information and as such warrant public health concern. © 2007 Elsevier B.V. All rights reserved. Keywords: Air pollution; Traffic; Particulate matter; Carbon monoxide; Nitrogen dioxide; Volatile organic compounds; Ambient; Wind; Diesel; Inversion 1. Introduction this study due to limited resources (Republic of the Philippines, 2003). Ambient air pollution, which includes but is not Data collected in the downtown area of Baguio City, limited to particulate matter (PM), carbon monoxide Philippines (Central Business District or CBD) in 2000 (CO), volatile organic compounds (VOCs) and nitrogen and 2001 indicated that Baguio was one of the most oxides (NOx), is a major environmental health problem polluted cities within the Philippines with respect to PM present within a variety of urban and rural settings. (World Bank, 2002), much of which was derived from Although high air pollution concentrations have been diesel-fueled motor vehicles [(61% of the 22,713 documented within rural areas (Hassan et al., 1995; registered vehicles in Baguio use diesel) (Baguio Naeher et al., 2007; Reinhardt et al., 2001), ambient air DOTC, 2003)]. Additionally, unleaded gasoline was pollution is most prevalent within urban areas poten- introduced in the Philippines in February 1994 and leaded tially resulting in large-scale exposures within the gasoline was nationally phased out in 2000. The motor residing population. The World Health Organization vehicles present that formerly used leaded gasoline were (WHO) estimates that 1.5 billion urban dwellers live in not equipped with catalytic converters and therefore areas with levels of outdoor air pollution above the would release a higher level of VOCs and NOx during the maximum recommended limits (WHO, 2005). combustion of unleaded gasoline (Hoekman, 1992). Due Epidemiological studies have shown a positive corre- to the importance of Baguio as a tourism and educational lation between exposure to air pollutants and morbidity/ hub within the northern Philippines, it is important to mortality including asthma, chronic obstructive pulmo- characterize the city's air quality and to identify potential nary disease, cardiovascular disease, lower birth weights, air pollution sources. cancer, and premature births (ATSDR, 1997; Dockery Adequate air pollution exposure studies can be costly et al., 1993; HEI, 2001; WHO, 2000). In Asia alone over which may prove to be a limiting factor for many areas, 500,000 people die each year from diseases related to air particularly within developing countries. Therefore, a pollution (WHO, 2005). Furthermore, studies have shown low-cost study design that could sufficiently predict that particulates generated from combustion processes, pollutant concentrations primarily using environmental especially diesel exhaust particulates, are more toxic and variables may prove to be suitable for areas that could often result in more exacerbated health effects than those not afford the equipment and personnel needed for a full from non-combustion processes (Bremner et al., 1999; air pollution study. Brunekreef et al., 1997; Hoek et al., 2000; South Coast, The objectives of this study were: 1) to identify the 2000; Van Vliet et al., 1997). most predictive environmental observation variables in Although there is a steadily growing air pollution urban, diesel-rich areas of Baguio City, Philippines in study database, personal air pollution exposures have not relation to PM2.5,PM10 and CO concentrations during been adequately studied and documented in many periods associated with varying motor vehicle densities developing countries. For example, the only air pollutant and nocturnal inversions and; 2) to monitor ambient that has been historically monitored within the Philip- concentrations of selected air pollutants [PM2.5,PM10, pines is total suspended particulates (TSP), which CO, NO2 and selected VOCs (BTEX: benzene, toluene, incorporates all PM less than 50 μm in aerodynamic ethylbenzene and xylenes)] in downtown Baguio City in diameter. However, studies have shown that particles order to determine diurnal pollution patterns. μ Author's personal copy less than 2.5 m in aerodynamic diameter (PM2.5) are primarily responsible for most of the particle-related 2. Methods health effects (Dockery et al., 1993; HEI, 2001). Even though the 1999 Philippine Clean Air Act set ambient 2.1. Study location standards for PM10,NO2, and CO, multiple parts of the country including Baguio City have not fully complied This study was conducted December 13–25, 2004 in with these new monitoring requirements as of the time of Baguio City, Philippines. Baguio City, a city of 252,386 B.E. Cassidy et al. / Science of the Total Environment 381 (2007) 47–58 49 people as of 2000, is located at 16°N and 120°E on the Approximately half the area of the city has a slope of island of Luzon in the Pacific Ocean 125 miles north of 25% or more (WOWPhilippines, 2005). The CBD is Manila approximately 5000 ft above sea level within the home to a variety of activities including but not limited Cordillera Mountains. Baguio's elevation and corres- to educational establishments (primary, secondary and ponding cooler temperature (mean annual temperature universities), hospitals, commercial businesses, restau- of 68 °F) result in a regular flow of visitors from the rants and offices/professional activities.