Particulate Matter Exposure of Bicycle Route Users in Bogotá

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1 Particulate Matter Exposure of Bicycle Route Users in Bogotá Extended Abstract 2011-A- 601-AWMA Oscar A. Fajardo Néstor Y. Rojas Universidad Nacional de Colombia, Department of Chemical and Environmental Engineering, Carrera Ed. 412, Of Postal code Bogotá, Colombia. Tel (571) ext , INTRODUCTION An increase in physical activity normally leads to assuming that cycling improves a population s fitness and quality of life. However, a thorough assessment of cycling paths health benefits should include an evaluation of the cyclists exposure to air pollutants such as PM 10. The body s increased breathing rate during a period of increased physical activity results in a higher air flow, deeper penetration and larger mass of inhaled air and pollutants. Furthermore, naso-oral breathing during moments of greater effort leaves the entrance open to unfiltered PM Strong associations between exposure to PM 10 and health effects have been found 2-6, making it relevant to determine the exposure conditions of cyclists experiencing physical stress. Most studies performed on cyclists exposed to PM in Europe, Canada or the USA have compared cyclists exposure to that of users of other modes of transport such as cars, buses and underground trains Cyclists exposure levels have been shown to be lower than those measured inside cars and buses, attributing this to cyclists riding alongside cars and not behind them, thereby reducing their exposure to exhaust emissions. Since cyclists ventilation rate is higher than that of car and bus passengers, inhaled air pollution doses are highest for cyclists 17. Using a bicycle as an alternative transportation mode in Bogotá increased significantly between 1998 and ,19, accounting for 1% to 4% of total trips. Such increase has been associated with the construction of a bicycle path network which was part of local government plans to improve public spaces and the population s quality of life. Since then, cycling s share as a transportation mode has been rather constant, although it has shown a slight decrease in 2009 and Since bicycle paths have been built alongside roads with heavy traffic, including diesel buses and trucks, it is predictable that cyclists are exposed to high concentrations of PM 10. In the present study, PM 10 concentration levels were determined at two sites on one of the main bicycle paths in Bogotá to estimate the daily dose inhaled by cyclists and suggest recommendations for future bicycle paths to be built in Colombian cities, as well as in highly-polluted, high-altitude cities worldwide. Experimental Methods Bogotá (4 38 N, W) is the Colombian capital and its largest city, having a population of nearly 8 million inhabitants. Because it is built on a high plateau in the

2 Colombian Andes (2,600 masl), its annual average temperature is 14 C, despite its tropical location. Mean annual PM 10 level is 60 µg/m 3 for the whole city, but this can rise to as high as 90 µg/m 3 in the western industrial area. This is precisely the area having the longest and busiest bicycle paths, most of which are built next to the curbs alongside main avenues. The bicycle path chosen for this study is a 10.2 km east-west path. It runs along the 80 th Street, one of the rapid bus transit (BRT) avenues, although part of it also runs beside conventional public buses and heavy cargo trucks. Two bicycle path sample sites were chosen for measuring PM 10. Site 2 was influenced by heavy BRT, conventional bus and heavy truck traffic, whereas site 1, located 1.6 km to the east, had the effect of BRT articulated buses only. MS&T samplers, also known as Harvard impactors, were used for collecting 8-hour PM 10 samples on 37-mm Teflon filters, starting each day at 7 a.m. A total of 19 samples were collected for site 1 and 10 samples for site 2. Filters were conditioned at 20ºC ± 1ºC and 50% ± 5% relative humidity for 24 hours before weighing them using a Sartorius microbalance (±1 µg resolution). Exposure was estimated as being daily PM 10 dose due to using the bicycle path, based on the US EPA exposure factors handbook 20,21, modified for bicycle path use. According to this, the average daily dose (ADD, µg kg -1 d -1 ) associated with bicycle path use is given by: C IR t ADD = (equation 1), where BW C is pollutant concentration, µg/m 3 ; IR is inhalation rate, m 3 /h t is time spent on the bicycle path per day, h/d BW is body weight, kg Average body weight and height and inhalation rate values recommended by the International Commission on Radiological Protection 22 were used in equation 1. Information regarding bicycle path users gender, age, daily and weekly exposure time and physical effort level needed by the model was collected by applying a short two-day survey, simultaneously with PM 10 sampling. Results and Discussion Mean PM 10 concentrations were µg/m 3 at site 1 and 77.9 µg/m 3 at site 2. However, because of day-to-day variability at each site, and considering that similar day-to-day trends were observed when simultaneous sampling was available, a statistical comparison between both sites was only plausible if only the days where simultaneous measurements were taken are taken into account. Results from an F-test and a t-test for such days showed that PM 10 concentrations from both sites could be considered to have the same variance and same mean, indicating that bicycle path users exposure to PM 10 did not depend on the path section which they were using. PM 10 was attributed to vehicle emissions, in the absence of constructions sites.

3 Mean PM 10 concentrations were significantly higher at both sites than those measured in similar studies 12,16,17, which just confirms that air pollutant exposure levels in Bogotá should be considered as a public health issue and that more effective air pollution reduction measures are required. A total of 73 users, 40 male (55%) and 33 female (45%), answered the short survey applied. Nearly 60% of the cyclists said that they used the bicycle paths for 2 to 4 hours a week, 11% for 6 hours a week and 13% for 8 hours a week. Use on any single day was around 1 hour for 31% of users, 3 hours for 22% of them and less than 30 minutes for 13% of users. Most cyclists used a bicycle as their means of transport for getting to their jobs and 73% of them covered 4 to 16 km on a single day. Furthermore, 91% of the cyclists said that such exercise involved a light level of effort and just 9% a moderate level of effort, this being related to an average <13 km/h and >13 km/h speed, respectively. Bicycle path users average daily dose (ADD) involving light and moderate effort was calculated using the mean, minimum and maximum PM 10 concentration values measured at both sites. Reference average daily dose values were estimated to determine the importance of the average daily dose estimated for the bicycle path users; this was based on 24-h exposure at rest to 20, 40 and 60 µg/m 3 PM 10 levels which can be considered as being low, average and high reference PM 10 concentration values in Bogotá. Most cyclists riding with light effort inhaled between 5.6% and 8.8% of the daily reference amount of particles when using the bicycle path, and when time spent on the path was high, the ADD associated with the bicycle path could be as high as 29.5%. For cyclists riding with moderate effort for a short time would inhale 3% of the reference amount of PM 10. Most regular cyclists would inhale between 11.8% and 18.4% PM 10 on the bicycle path riding with moderate effort and the most enthusiastic users could inhale as much as 63.8% for female adult users and 45.3% for male adult users. SUMMARY Bogotá remains as a model in Latin America, since it has the most extensive bicycle path infrastructure. Only similar schemes in Europe or North America can be compared to it. However, PM 10 concentrations found in Bogotá are a critical factor affecting the quality and benefits of a project of such magnitude. Although constructing cyclepathways it is an innovative decision for a city seeking to promote cycling as a transport mode in Bogotá, constructing bicycle paths alongside the city s main roads would technically seem not to be the best choice. The pollution levels users are exposed to, given their proximity to vehicle traffic, puts their respiratory systems at greater risk. The studies reviewed here show the benefits of defining bicycle paths or routes away from roads having high traffic flow (especially where diesel vehicles are involved, as they tend to be the most polluting), as well as avoiding peak traffic times.

4 However, bicycle path users are usually heading to their workplaces, in most cases under pressure from time deadlines forcing them to maintain a fast pace over long distances, so that the percentage of associated ADD can reach high percentages when compared to reference doses, but at a much lower time. This affects women more significantly than men. REFERENCES 1. Salma, I., Balashazy, I., Hofmann, W., and Záray, G Effect of physical exertion on the deposition of urban aerosols in the human respiratory system. J Aerosol Science. 33, pp Pope, C.A. and Dockery, D.W Health effects of fine particle air pollution: lines that connect. J air waste Manage Assc., pp Bennett, WD, KL Zeman, and AM. Jarabek. Nasal contribution to breathing and fine particle deposition in children versus adults. J Toxicol Environ Health A.71(3), pp Daniels, M.J., Dominici, F., Samet, J.M. and Zeger, S.L Estimating Particulate Matter-Mortality Dose-Response Curves and Threshold Levels:An Analysis of daily Time-Series for the 20 Largest U.S. Cities. J. Epidemiol. 152, pp De Hartog, J. J., Hoek, G., Peters A De Hartog J.J, Hoek G, Peters A, et al. Effects of fine and ultrafine particles on cardio respiratory symptoms in elderly subjects with coronary heart disease. American Journal of Epidemiology. 157, pp El-Fadel, M. and Massoud, M Particulate matter in urban areas: healthbased economic assessment. J the science of the total environment.257, pp Samoli, E., Antonis, A., Touloumi, G., Estimating the Exposure-Response Relationships between Particulate Matter and Mortality within the APHEA Multicity Project. Environ. Health. Perspect.113, pp Adams, H.S., Nieuwenhuijsen, M.J. and Colvile, R.N. Determinants of fine particle (PM2.5) personal exposure levels in transport microenvironments. Atmospheric Environment.. 35, pp Boogaard, H., Frank Borgman, J. Kamminga, and G. Hoek Exposure to ultrafine and fine particles and noise during cycling and driving in 11 Dutch cities. Atmospheric environment. 43(27), pp Cassano, F, Bavaro, P., Mancini, A Exposure to air pollutants in the city of Bari. Med Lav. 6(100), pp Herte, O., Hvidberg, M., Ketzel M A proper choice of route significantly reduces air pollution exposure A study on bicycle and bus trips in urban streets. Science of The Total Environment. 389(1), pp

5 12. Panis, L., De Geus, B., Vandenbulcke, G. et al Exposure to particulate matter in traffic: A comparison of cyclists and car passengers. Atmospheric Environment. 44(19), pp McNabola, A., Broderick, B.M., and Gill, L.W Relative exposure to fine particulate matter and VOCs between transport microenvironments in Dublin: Personal exposure and uptake. Atmospheric Environment. 42(26), pp Nambdeo, A and Bell, M.C Characteristics and health implications of fine and coarse particulates at roadside, urban background and rural sites in UK. J environment International.31, pp Strak, M, Boogaard, H., Meliefste, K Respiratory health effects of ultrafine and fine particle exposure in cyclists. Occup Environ Med. 67, pp Thai, A., McKendry, I. and Brauer, M Particulate matter exposure along designated bicycle routes in Vancouver, British Columbia. J Science of the total environment. 405, pp Zuurbier, M, Hoek, G., Oldenwening, M Commuters' exposure to particulate matter air pollution is affected by mode of transport, fuel type, and route. Environ Health Perspect.118(6), pp Mosquera, J Entendiendo el uso de la bicicleta como medio de transporte en Bogotá; una aproximación cualitativa. In: Simposio Colombiano de Ambientes Urbanos y Salud Pública. Bogotá. 19. Alcaldía Mayor de Bogotá. Alcaldía Mayor de Bogotá. [online]. [Accessed 21 Octubre 2008]. Available from World Wide Web: <HYPERLINK " _id=1351&cat_id=239" a=1&pub_id=704&pag_id=1351&cat_id=239> 20. Environmental Protection Agency (EPA) Exposure Factors Handbook. [online]. [Accessed 31 Sep 2010]. Available from World Wide Web: <HYPERLINK " > 21. Environmental Protection Agency. Guidelines Exposure Assessment.. [online]. [Accessed 10 Dec 2008]. Available from World Wide Web: <HYPERLINK " cea/raf/recordisplay.cfm?deid=15263.> 22. International Commission On Radiological Protection (ICRP66) Human respiratory tract model for radiological protection. 66.

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