Breathing the lovely morning air in Delhi traffic

GUEST POST.  “Anyone who has sat in traffic in an Indian city knows what it feels like to be blasted in the face by the exhaust of a neighboring vehicle.  Despite the potentially important health risks that may be involved with such encounters, relatively few studies have measured in-traffic air pollution in developing world cities, where the combination of congested traffic and high-emitting vehicle fleets make “in-your-face” exposures a feature of everyday life.”

(But before reading any further, may we suggest that you enjoy the following two minute video.)

Concentrations of fine, ultrafine, and black carbon particles in auto-rickshaws in New Delhi, India

– Joshua Apte, Energy and Resources Group, UC Berkeley

My colleagues and I recently spent four months in New Delhi measuring particulate matter inside auto-rickshaws — semi-enclosed vehicles known elsewhere “tuk-tuks” or three-wheelers. To capture the effects of individual exhaust plumes, we used instruments that are capable of measuring second-to-second changes in air pollution concentration.

Over the entire study, average concentrations of fine particle mass (PM2.5), black carbon (BC), and ultrafine particles (UFP) inside the auto-rickshaws were among the highest ever recorded for a routine urban transportation setting. Short-term peak concentrations during any trip — for example, when passing through a truck’s exhaust plume (see video) — were extremely high for all the pollutants we measured.

Our results suggest that the high concentrations in auto-rickshaws are primarily caused by the city’s vehicle fleet, rather than by so-called “self-pollution” from a rickshaw’s own emissions. For example, concentrations inside cars with open windows were statistically indistinguishable from those in auto-rickshaws. Overall, 30% of PM2.5, 68% of BC, and 86% of UFP concentrations in auto-rickshaws were attributable to on-road pollution in excess of the already-high ambient concentrations.

Ten years after Delhi’s initial successes with CNG as a clean transportation fuel, the goal of clean air remains a long way down the road.

* The full report of the team is available in Atmospheric Environment 45, 4470-4480. http://dx.doi.org/10.1016/j.atmosenv.2011.05.028

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Abstract:

Concentrations of air pollutants from vehicles are elevated along roadways, indicating that human exposure in transportation microenvironments may not be adequately characterized by centrally located monitors. We report results from ~180 h of real-time measurements of fine particle and black carbon mass concentration (PM_2.5, BC) and ultrafine particle number concentration (PN) inside a common vehicle, the auto-rickshaw, in New Delhi, India. Measured exposure concentrations are much higher in this study (geometric mean for ~ 60 trip-averaged concentrations: 190 µg m^-3PM_2.5 , 42 µg m^-3 BC, 280 × 10³particles cm^-3; GSD ~ 1.3 for all three pollutants) than reported for transportation microenvironments in other megacities. In-vehicle concentrations exceeded simultaneously measured ambient levels by 1.5× for PM_2.5, 3.6× for BC, and 8.4× for PN. Short-duration peak concentrations (averaging time: 10 s), attributable to exhaust plumes of nearby vehicles, were greater than 300 µg m^-3 for PM_2.5, 85 µg m^-3 for BC, and 650 × 10³ particles cm^-3 for PN. The incremental increase of within-vehicle concentration above ambient levels — which we attribute to in-and near-roadway emission sources — accounted for 30%, 68% and 86% of time-averaged in-vehicle PM_2.5­, BC and PN concentrations, respectively. Based on these results, we estimate that one’s exposure during a daily commute by auto-rickshaw in Delhi is as least as large as full-day exposures experienced by urban residents of many high income countries. This study illuminates an environmental health concern that may be common in many populous, low-income cities.

Citation
Apte, J.S., Kirchstetter, T.W., Reich, A.H., Deshpande, S.J., Kaushik, G., Chel, A., Marshall, J.D., Nazaroff, W.W., 2011. Concentrations of fine, ultrafine, and black carbon particles in auto-rickshaws in New Delhi, India. Atmospheric Environment 45, 4470-4480. http://dx.doi.org/10.1016/j.atmosenv.2011.05.028

Authors:

Joshua Apte is a PhD candidate in the Energy and Resources Group at UC Berkeley, USA;
Thomas Kirchstetter is a scientist in the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory, USA;
Alexander Reich and Shyam Desphande were most recently undergraduate research assistants from Grinnell College, USA;
Geetanjali Kaushik is assistant professor at the University of Petroleum and Energy Studies, Dehradun, India;
Arvind Chel is senior research scholar in the Centre for Energy Studies at Indian Institute of Technology, Delhi;
Julian Marshall is McKnight Land-Grant Professor of Urban Sustainability at the University of Minnesota, USA and
William Nazaroff is Daniel Tellep Distinguished Professor in the Department of Civil and Environmental Engineering at UC Berkeley, USA.

For further inquiries, contact Joshua Apte at japte {at} berkeley {dot} edu