Traffic impacts on PM2.5 air quality in Nairobi, Kenya

Abstract

Motor vehicle traffic is an important source of particulate pollution in cities of the developing world, where rapid growth, coupled with a lack of effective transport and land use planning, may result in harmful levels of fine particles (PM2.5) in the air. However, a lack of air monitoring data hinders health impact assessments and the development of transportation and land use policies that could reduce health burdens due to outdoor air pollution. To address this important need, a study of traffic-related PM2.5 was carried out in the city of Nairobi, Kenya, a model city for sub-Saharan Africa, in July 2009. Sampling was carried out using portable filter-based air samplers carried in backpacks by technicians on weekdays over two weeks at several sites in and around Nairobi ranging from high-traffic roadways to rural background. Mean daytime concentrations of PM2.5 ranged from 10.7 at the rural background site to 98.1 μg/m3 on a sidewalk in the central business district. Horizontal dispersion measurements demonstrated a decrease in PM2.5 concentration from 128.7 to 18.7 μg/m3 over 100 meters downwind of a major intersection in Nairobi. A vertical dispersion experiment revealed a decrease from 119.5 μg/m3 at street level to 42.8 μg/m3 on a third-floor rooftop in the central business district. Though not directly comparable to air quality guidelines, which are based on 24-hour or annual averages, the urban concentrations we observed raise concern with regard to public health and related policy. Taken together with survey data on commuting patterns within Nairobi, these results suggest that many Nairobi residents are exposed on a regular basis to elevated concentrations of fine particle air pollution, with potentially serious long-term implications for health.

Characterizing and predicting coarse and fine particulates in classrooms located close to an urban roadway

“…The location of monitoring station with respect to the adjacent road has been found to be a main factor affecting the PM concentrations at classroom B. When compared with previous studies, it was found that in most of the outdoor measurements, the PM concentrations showed sharp drop with distance away from roadway (Kinney et al, 2011;Levy et al, 2003). Kinney et al (2011) observed that the average concentrations at the roadside (0 m) were more than 4 times higher than average concentrations 30 m away, and over 6 times higher than those 100 m away.…”

“…When compared with previous studies, it was found that in most of the outdoor measurements, the PM concentrations showed sharp drop with distance away from roadway (Kinney et al, 2011;Levy et al, 2003). Kinney et al (2011) observed that the average concentrations at the roadside (0 m) were more than 4 times higher than average concentrations 30 m away, and over 6 times higher than those 100 m away. A Student's t test (single-tailed) was also performed to determine whether the PM 10 , PM 2.5 , and PM 1 concentrations were significantly higher at near-field region compared with far-field region.…”

Characterization of Size-Fractionated Particulate Matter and Deposition Fractions in Human Respiratory System in a Typical African City: Nairobi, Kenya

“…Using the deposition fractions from fine PM, the estimated deposited masses are 9.5 µg in the head airways region, 1.1 µg in the tracheobronchial region and 0.7 µg in the pulmonary for every 1000 L of air breathed by an average urbanite in Nairobi city. However, Kinney et al (2011) reported PM 2.5 average concentration of 98.1 µg m -3 from a sidewalk in the Central Business District which translates to a deposition of 45 µg (head airways), 5.2 µg (tracheobronchial) and 3.0 µg (pulmonary). A study on occupational exposure by Ngo et al (2015) reported that bus drivers in Nairobi city were exposed to about 103 µg m -3 which translates to a deposition of 46 µg to the head airways, 5.5 µg to the tracheobronchial and 3.2 µg to the pulmonary tract.…”

“…The urban centres in Africa are growing at exceedingly high rates whereas the provision of prerequisite social services and amenities are not commensurate with this growth (UN-HABITAT, 2006;UNDESA, 2010;Karanja and Makau, 2012). The urban population is reported to be exposed to wide range of air pollutants (Gulis et al, 2004;Ngo et al, 2015) whose sources have been identified as vehicular emissions, biomass burning and mineral dust (Formenti et al, 2003;Gatari and Boman, 2003;Kinney et al, 2011;Petkova et al, 2013;Gaita et al, 2014). Therefore, the objectives of this study were to obtain a size distribution of PM and elemental concentrations in a typical African city and to determine the deposition fractions of measured PM and trace elements in the respiratory system.…”

Stated preferences for improved air quality management in the city of Nairobi, Kenya

“…Toxic gases such as CO, NO x , SO x and PM x are in high concentrations as a result of increased urban expansion and motorization linked to rapid economic development experienced over the last decade. Consequently, most city residents are exposed to elevated concentrations of vehicular emissions that potentially pose serious long-term eff ects on human health and quality of the urban environment (Odhiambo et al, 2010;Kinney et al, 2011;Vliet & Kinney, 2007). For instance, CO causes blood clotting when it reacts with haemoglobin.…”