Electric lighting is not always an option in low and middle-income countries, particularly in rural areas of Asia and Africa. Even with grid access, connection and maintenance expenses can be financially beyond reach for the poor. In the villages of Kenya, therefore, kerosene lamps remain a chief source of lighting in most households.

Kerosene is also used for cooking and, until recently, many considered kerosene a cleaner-burning fuel compared to biomass alternatives, though epidemiologic findings now challenge that assumption. A paper co-authored by COEH adjunct professor Michael Bates showed the use of kerosene lamps may substantially increase the risk of tuberculosis. In a separate study, Bates published new evidence that the use of kerosene for cooking may be a risk factor for acute lower respiratory illness in young children.

Unlike smoke-spewing biomass fuel, kerosene may appear cleaner to the naked eye. But it is actually a dirty fuel, producing fine particles of pollution (particulate matter with an aerodynamic diameter less than 2.5 microns, or PM2.5) when burned that Bates and others believe may be a more potent cause of health effects than PM2.5 from biomass burning. And people in close and prolonged contact with kerosene lamps, often in poorly ventilated homes, potentially face a magnified exposure.

The options for poor families wanting an alternative to kerosene for lighting have been limited, but in recent years sales of solar-powered lighting devices have risen exponentially in the developing world, notes Bates, who led the first ever field-based assessment to measure changes in exposure for people using solar rather than kerosene lamps.

For the study, Bates, former doctoral student Nick Lam PhD ’14 – now a post-doctoral research associate at the University of Illinois – and colleagues from Kenya and Uganda enrolled 20 students attending a secondary school near the city of Busia, Kenya, and a parent in each household. For all households enrolled, cooking took place separately from the main house. This reduced the possibility that stove emissions could interfere with measurements of lamp emissions.

Using a “before-and-after” study design, the researchers assessed PM2.5 and carbon monoxide (CO) in each home and with personal exposure monitoring for a period prior to introducing three solar lamps per household. Follow-up procedures mirrored baseline procedures – questionnaires to the lamp users, room monitoring of PM2.5 and CO, personal monitoring of lamp users for 48 hours – and devices attached to both kerosene and solar lamps to monitor usage.

They found kerosene lamp use was associated with substantial exposure to PM2.5 for both the adults and students. In the three rooms compared at baseline and follow-up, PM2.5 concentrations showed little change in the kitchens where concentrations were dominated by biomass smoke from cooking, but there was a 79 percent reduction on average in the students’ rooms and a 61 percent reduction in the main living rooms. Most importantly, personal monitoring showed about a 73 percent reduction in PM2.5 exposure between baseline and follow-up for school pupils and 50 percent reduction for the adult lamp users. The smaller reduction for the adults, almost all women, was because of their greater exposure to cooking smoke.

Monitoring data showed the solar lamps were well-used – on average for about 5 hours each per day, with peak usage in the evening and to a smaller extent in the morning – displacing use of kerosene lamps by about 95 percent. This is a very high rate of adoption of new technology and confirmed the solar lamps were acceptable to families.

Although they did not monitor CO in the kitchen, baseline and follow-up concentrations in other rooms were below recommended health standards, leading the researchers to conclude there is marginal value in monitoring CO and that future studies should focus on PM2.5.

Despite the limitations of a small sample size, Bates and his co-investigators believe the results of this study provide good evidence that in poor nations solar lamps are a promising near-term solution to reducing indoor air pollution in homes reliant on kerosene for lighting. They hope to follow up this study with a much larger one that focuses on measuring any health benefits associated with replacing kerosene lamps with solar.

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