be representative of the spatial distribution of manufacturing firms in Uganda, and consistent with the official administrative boundaries of Uganda. Because the air pollution assessment was designed to accompany a firm survey designed to be representative of the firm distribution across the country, exclusion of the Northern region was informed by low population density and low firm density of the targeted firm categories. The study set out to collect 6-month pollution data with primary focus around the major emission sources in urban centers<sup>12</sup> and targeted firms within the sampled locations.

As mentioned above, the decisions for deployment of monitors started from the pre-selected subcounties and was supplemented by collation of grey literature to help establish parish level boundaries for the monitoring exercise (i.e. re-aligning with the pre-selected boundaries from the firm-level survey) and map out tentative locations for stationary monitors including boundaries for mobile monitoring-partly informed by the authors’ knowledge of the local environment.

The field validation exercise to all the selected sub-counties followed, with the objective to confirm static deployment locations and identify boundaries/routes for supplementary mobile monitoring for areas where static would not have adequate spatial coverage. Spatial boundaries and buffer zones of key pollution generating activities with the potential to affect local air quality were also identified during the field validation exercise. As anticipated, major pollution generating activities including target firm categories were largely situated in urban areas. For stationary deployment, a maximum of 1-2km impact zones (region within the physical environment and activities that can affect local air quality) were considered as most major emission sources within the study areas are closer to the ground (<3m above the ground) having largely localized effects. This was partly informed by study objectives and the fact that there is no official air quality monitoring in Uganda (i.e. there are no Air Quality Management Areas).<sup>13</sup> Lists of all the sampled sub-counties with respective parishes were uploaded onto a portable mapping tool (ArcGIS collector) for precision during the field visits and corresponding GPS coordinates for all potential locations in visited subcounties were obtained ( **figure 1** ).

> 12 Since there is no universal threshold/definition for urban centers (Chomitz et al., 2005; UN, 2017), we adopted the official classification of urban areas in Uganda, i.e., gazetted administrative centers including District Headquarters, Cities, Municipalities, Towns, Town Boards and all Trading Centers with a population of more than 1,000 persons (UBOS, 2001) and all sampled locations met this criterion. This threshold is also comparable to other jurisdictions, e.g., Chomitz et al. (2005) and UN (2017), and adopting a different threshold would not have significantly altered the sampling, in fact even the US census threshold of 288 persons per square kilometer adopted for the parish level firm survey was way below the average parish level population density.

> 13 It is typical for regulatory practice, e.g., UK-EA, to define impact zones for air quality risk assessments prior to establishing monitoring sites.

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