Definition of the study area. The definition of the study area is a key step in the HIA process. The objective is to obtain a study area where the average of pollutant levels measured at fixed monitors will be a good estimate of the average population exposure. This means that: - no part of the area is under the influence of a large stationary source, which would result in high heterogeneity of the pollutant levels - there is no rupture of urbanisation within the study area, i.e., urban density is relatively homogeneous - there are no main changes in topography that would modify the dispersion and concentration of pollutants - a majority of the population lives and works within the study area. In addition, health data must be available on a geographical scale consistent with the study area. Finally, the choice of the study area should also take into account policy considerations (i.e. administrative boundaries, areas subjected to the same policies… In practice: - Collect useful data that will help characterise the study area. This can include : - a precise and recent map of the urban area (scale 1/25,000) with topographic curves and indications on the urbanisation - Information on prevailing winds - List of the urban area’s municipalities - Inventory of all urban background and suburban air monitoring stations and a map of their locations - Inventory of the main industrial plants emitting air pollution and a map of their locations - Population data for each municipality in the urban area - Data on daily commuting between home and place of work - Inventory of air monitoring stations and a map of their locations - Inventory of hospitals with cardiovascular and/or respiratory activity and a map of their locations. - Define a first area, named zone 1, following the administrative boundaries of the city, - Using data on commuting, you may include surrounding municipalities where more than 60% of inhabitants commute daily to zone 1. Doing so enables taking into account municipalities where significant portions of the population are exposed to central-city pollution on a daily basis. - Check that relevant health data are available for the study area, especially if working with hospitalisation data. - Take advice from experts at the air quality monitoring network of the area in order to check that calculating an average air-pollution-exposure level makes sense for the population’s exposure of the whole selected area.
Definition of the study area. The Project is located in sections of Ruiru, Kiambu and Juja sub-counties, Kiambu County, central Kenya, on the transitional zone of the Upper Athi basin and the Kikuyu dissected plateau (GPS coordinates 0.5°N Latitude and 37°E Longitude). The three sub-counties are located off the Nairobi-Thika Super Highway, which is a section of A2 Nairobi-Addis - Ababa trunk road. The Project infrastructure traverses the following areas within the mentioned sub-counties: • Githurai; • Kimbo; • Kahawa Sukari; • Kahawa Wendani; • Kiuu-Githurai; • Mwihoko; • Ruiru; • Wendani; and • Mwiki. Specifically, the Project is intended to benefit the following zones in the greater Githurai area: • Kahawa Sukari; • Kahawa Wendani: • Kiuu A; • Kiuu B; • Mwiki; • Mwihoko A; and • Mwihoko B. The sub counties within which the Project lies are as indicated with the red stripes in Figure 4.1 below.
