Household air pollution exposure and nasopharyngeal carriage of streptococcus pneumoniae in Malawian infants

摘要

Approximately 3 billion people rely on the burning of solid fuel for everyday cooking. Children can be exposed to harmful household air pollution (HAP) generated during the combustion of these solid fuels. These exposures have been linked to many adverse health outcomes including pneumonia. The mechanism linking exposure to pneumonia has been poorly characterized. Here we aim to quantify the relationship between HAP exposure and prevalence of nasopharyngeal carriage (NPC) of streptococcus pneumoniae (SP), which is considered a necessary step to developing pneumonia. This study was conducted in the Karonga district in northern Malawi and focused on 6-week and 6-month old children. 48-hour PM2.5 exposures were measured using the RTI MicroPEM and nasal swabs were collected at the end of exposure sampling. This study was embedded in the Cooking and Pneumonia Study (CAPS) to take advantage of the available intervention stoves (Philips HD4012LS). We collected 673 valid exposure measurements and found no significant difference in personal PM2.5 exposures of children in homes using an open fire or the Philips stove (p=0.1525; 53.4 [95%CI 49.9, 57.1] μg/m~3; 48.0 [42.1, 54.6] μg/m~3; respectively). However, exposures did vary significantly by age (p<0.0001), presence of cigarette smoker (p=0.0181), and kitchen location (p=0.0080). We also found that personal PM2.5 exposures in 6-month old children that tested positive for SP-NPC were significantly higher than children that tested negative (p=0.0020; 60.6 [56.1, 65.6] μg/m~3; 43.4 [35.3, 53.4] μg/m~3; respectively). We observed that 6-week old children living with an active cigarette smoker were 70% more likely to test positive for SP-NPC than their peers. This is the first study in which MicroPEMs were used to measure the personal exposures of infants on a large scale. To our knowledge this is also the first study to show a direct link between HAP exposure and prevalence of nasopharyngeal carriage of streptococcus pneumoniae.