Personal Exposure Assessment for Transportation Modes in La Paz
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Vehicle emission regulations are sparse are under enforced in low to middle income countries (LMICs), leading to exceedingly high point source pollutant concentrations in population dense urban areas. Although personal vehicle ownership is low at 68 per 1000 people overall for Bolivia, there is an abundance and large diversity of public transportation methods in La Paz. This project sought to differentiate in terms of commuter exposure levels the multitude of transportation options. Unique to La Paz is the recently installed cable car system, termed locally Mi Teleferico or simply the Teleferico. The main objective was to compare conventional ground based transportation methods (personal vehicle, taxi, micro bus, diesel bus, and walking) to the Teleferico using exposure to criteria air pollutants and their tracers. A focus of the project was to integrate and demonstrate the effectiveness of low cost air monitoring solutions. Using hand held battery-operated monitors for carbon monoxide (CO) and particle matter (PM [2.5um]) and its tracer, black carbon (BC) (all major constituents of exhaust from motor vehicles), main traffic thoroughfares and common commuter routes were identified and then traversed in each of the available forms of transportation. Data was collected during peak emission time frames, namely the morning and evening commuter rush hours. The concentrations and pollutant levels observed along these routes were compared to data collected during the same time of day in the Teleferico cabin. It was found that CO concentrations in the Teleferico cabin were essentially negligible, both during the morning and evening sample times. Concentrations observed on foot were on average slightly higher than those seen on the Teleferico, but did not deviate as much as measurements taken in motor vehicles. CO levels were within 1 ppm in both the personal vehicle and the micro bus, both averaging approximately 23 ppm. The diesel bus CO measurements resulted in an average of 8.82 PPM. BC observations for the personal vehicle, micro bus, and diesel bus were 11.88, 16.73, and 17.14 ug/m3 respectively. These results were in order of magnitude agreement with the PM observations, which were 24.42, 16.81, and 26.41 ug/m3 for the personal vehicle, micro bus, and diesel bus respectively. This data was used to determine unit exposure per time for each of the modes of transportation. The results suggest that there is a clear advantage to utilizing the Teleferico as a mode of transport in terms of pollutant exposure as compared to motorized vehicles. With this data, one could make deterministic calculations as to their pollutant exposure based on commute time and mode of transport. The low cost equipment proved appropriate for this purpose, and could certainly be used for similar personal exposure measurements or for stationary air quality monitoring in locations that do not have the resources for laboratory quality instruments.