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Kerosene Lamps Lead to Higher Concentrations of Black Carbon in Air

Compared to those who use electricity, exposure to black carbon particles is 81% more among women in Mozambique who rely on kerosene as the primary source of energy for lighting.

This was the key finding of a research conducted by the Barcelona Institute for Global Health (ISGlobal), an institute supported by “la Caixa”, in partnership with the Manhiça Health Research Centre (CISM) in Mozambique and the Institute of Environmental Assessment and Water Studies (IDAEA) in Barcelona.

The research, which has been published in the journal Environment International, recruited 202 women aged between 12 and 49 years living in Manhiça, a semi-rural region situated 80 km north of Maputo, Mozambique. During the study phase, the women were asked to wear a portable device which recorded their personal exposure to black carbon (soot) 24 hours a day. Furthermore, all the participants answered a comprehensive questionnaire about their domestic routines and the features of their homes.

In the one-year research period, ambient levels of fine particulate matter (PM2.5), elemental carbon, and black carbon were measured once every three days in samples gathered together by a stationary sampling device set up in the CISM facilities.

Black carbon is one of the constituents of PM2.5 (particles having a diameter smaller than 2.5 millionths of a meter), an air pollutant that is injurious to human health as well as the planet. Black carbon from domestic combustion produces 25% of global anthropogenic PM2.5 emissions and 80% of those are created in Africa.

One prominent finding was that personal levels of black carbon exposure among the women taking part in this study were much greater than those observed in studies of adults and children residing in European cities (a day-to-day average of 15 μg/m3 compared to 2.8 μg/m3 in Europe).

Black carbon, in Europe, is used as a marker of air pollution caused by traffic, but in rural areas and in middle- and low-income nations, it is a marker of domestic combustion. It is projected that 95% of Mozambique’s population rely on contaminated fuels for cooking and, because of the absence of electricity in several areas of the country. The use of portable kerosene lamps (or candeeiro de vidrio, as they are referred to in Portuguese) for domestic lighting is extensive.

The use of kerosene as an energy source in the home has been associated with tuberculosis, acute respiratory infections in children, low birth weight and neonatal mortality. And it is women who bear the brunt of this effect because traditionally they carry the burden of all the domestic work.

Ariadna Curto, Researcher and Study Lead Author, ISGlobal

In this research group, the highest level of exposure to black carbon happened, on average, between 6 and 7 in the afternoon—around sunset—and the highest level of concentrations were 93% higher among the women who stated that they used kerosene lamps to light their homes.

Another significant finding was that women living with a partner had a 55% higher peak of exposure than single, widowed or divorced women. This difference can be attributed to the fact that the women in our study undertook all the domestic work in the household (almost all of the participants were housewives) and, consequently, the greater the number of people living in the home, the greater their personal exposure.

Ariadna Curto, Researcher and Study Lead Author, ISGlobal

The other factors, besides the kind of lighting used, that were predictive of black carbon exposure were kitchen model and ambient temperature. Black carbon exposure was 61% higher in the group of women who stated having a partially or totally enclosed kitchen than in those who had an outdoor kitchen or no kitchen.

Another pertinent factor is that in the majority of the participant households, the women used solid biomass fuels (coal and wood) for cooking, which additionally increased their exposure to black carbon.

Examination of data on temperature showed that average exposure to black carbon reduced by 24% for every 5 °C rise in ambient temperature. “This difference is probably due to the fact that when the temperature rises, the women tend to cook outdoors (where the smoke is dispersed) and use less fuel to heat the house,” explains Cathryn Tonne, ISGlobal researcher and study’s last author.

Finally, PM2.5 concentrations went beyond the maximum safe threshold stipulated by the WHO in 12% of the samples collected by the device set up in the CISM facilities to compute ambient pollution, with higher concentrations being noticed mostly during the dry season.

Air quality in sub-Saharan Africa is expected to deteriorate further in the near future as a result of several factors, including an increase in vehicle ownership and industrial expansion. Studies like ours show that improving access to electricity or clean alternative lighting (solar lamps, for example) in populations currently dependent on inefficient household energy sources would have very positive effects on air quality and reduce negative health impacts.

Cathryn Tonne, Researcher and Study Last Author, ISGlobal


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