Exposures to and origins of carbonaceous PM2.5 in a cookstove intervention in Northern Ghana

Abstract

REACCTING (Research on Emissions Air Quality, Climate, and Cooking Technologies in Northern Ghana) was a 200-home cookstove intervention study from 2013 to 2015. Study households were divided into four groups: a control group, a group given two locally made rocket stoves, a group given two Philips forced draft stoves, and a group given a locally made rocket stove and a Philips stove. In a subset of study households, 48-hour PM exposure samples were collected for adults and children, as well as in the primary cooking area. Further, weekly ambient background PM samples were collected for the first nine months of the study. All PM samples were analyzed for elemental and organic carbon (EC/OC), and a subset was also analyzed for organics. Mixed effects modeling was applied to quantify differences in PM exposures between the groups and to assess relationships between exposures and cooking area measurements. Results showed that personal OC exposure for the intervention groups was 56.6% lower than the control group (p≤0.01). Both intervention groups given Philips stoves had significantly lower EC exposure than the control group (60.6% reduction, p≤0.02). Only weak relationships were found between personal and cooking area EC or OC. Source apportionment modeling was performed on both the personal/microenvironment and the ambient organics PM data sets to assess the sources of the observed PM. We identified six PM sources. The identified source factors were similar among the data sets, as well as with previous work in Navrongo. Two sources, one characterized by the presence of methoxyphenols, and one by the presence of polyaromatic hydrocarbons and EC, were associated with biomass burning, and accounted for a median of 9.2% of OC and 15.3% of EC personal exposure. Here, we demonstrate the utility of using the cooking-related source apportionment factors within a mixed effects model for more precise estimation of exposures due to cooking, rather than other combustion sources unrelated to the intervention.

Rural–urban differences in cooking practices and exposures in Northern Ghana

“…During the study period, ambient pollutant concentrations were measured at the Navrongo Health Research Center (NHRC), five health centers located across the K-N districts, and in the middle of the primary market place in the Navrongo town center (figure 1). These measurements were made with G-Pod air quality monitors ( [3,6], mobilesensing technology.com), configured to measure CO with an electrochemical sensor (CO-B4, Alphasense, Essex, UK). Ambient particulate matter with aerodynamic diameters less than 2.5 mm (PM 2.5 ) samples were collected on quartz filters at the NHRC, and only the carbonaceous component was quantified following the methods described by Piedrahita et al [6].…”

“…Other measurements conducted in both rural and urban households included stove use monitoring, microenvironment (kitchen) carbon monoxide (CO) concentrations, and personal exposures of CO and [7]. 48 h personal carbonaceous PM 2.5 exposure was collected and measured on a subset of the CO sampling periods (tables S3, S4) using methods described by Piedrahita et al [6]. All PM 2.5 samples were collected on quartz filters and were analyzed for particulate organic carbon (OC) and elemental carbon (EC) mass.…”

“…All PM 2.5 samples were collected on quartz filters and were analyzed for particulate organic carbon (OC) and elemental carbon (EC) mass. Organic speciation was quantified and used for source apportionment applications on a subset of the samples [6].…”

“…3 mg m −3 ). This further suggests that local sources including but not limited to cooking are the primary drivers for exposure for urban dwellers, as they are for rural dwellers [6], and the density of sources is low enough that regional atmospheric mixing is helping reduce exposures. The influence of local sources is seen by comparing the ratio of personal exposure to ambient total carbonaceous PM (EC þ OC), which is 9.7 in REACCTING [6], compared with, for example, 2.4 in Colorado, USA [10], where they compared personal exposure to ambient total Environ.…”

“…Further, the extent to which cooking versus other sources drives exposures will depend on what other sources are present in the environment (i.e. [6]). For instance, daytime commercial cooking with charcoal burning coalpots and TSF is very common in Navrongo town and virtually nonexistent in rural communities.…”