Residential solid fuel emissions contribute significantly to air pollution and associated health impacts in China

Abstract

Residential contribution to air pollution-associated health impacts is critical, but inadequately addressed because of data gaps. Here, we fully model the effects of residential energy use on emissions, outdoor and indoor PM_2.5 concentrations, exposure, and premature deaths using updated energy data. We show that the residential sector contributed only 7.5% of total energy consumption but contributed 27% of primary PM_2.5 emissions; 23 and 71% of the outdoor and indoor PM_2.5 concentrations, respectively; 68% of PM_2.5 exposure; and 67% of PM_2.5-induced premature deaths in 2014 in China, with a progressive order of magnitude increase from sources to receptors. Biomass fuels and coal provided similar contributions to health impacts. These findings are particularly true for rural populations, which contribute more to emissions and face higher premature death risks than urban populations. The impacts of both residential and nonresidential emissions are interconnected, and efforts are necessary to simultaneously mitigate both emission types.

Fig. 1. Relative contributions of residential and nonresidential energy consumption to the emissions of primary PM_2.5 and SO₂ (as a representative secondary aerosol precursor), indoor/outdoor PM_2.5 concentrations, population exposure to PM_2.5, and premature deaths associated with PM_2.5 exposure.

The emissions of both primary PM_2.5 and SO₂ are shown. Residential energy sources were further categorized into coal, biomass fuels, and clean energy for cooking and heating. Urban and rural usages are separated as both sources and receptors. The quantified contributions from one step to the next are shown as numbered arrows. Total quantities are shown in the centers of the pie charts. The relative contributions by the residential sector are presented for the individual steps on the right side.

Fig. 2. Cumulative distributions of the annual mean population exposures to PM_2.5 originating from residential sources and all sources in urban and rural China in 2014.

The WHO air quality guideline (AQG) and interim targets 1 to 3 (IT-1, IT-2, and IT-3) (17), which are also applicable to indoor air, are shown as vertical lines. IT-1 (35 μg/m³) is the same as the Chinese national ambient air standard (16).

Fig. 3. Spatial distributions of premature deaths per square kilometer associated with residential emissions of both primary PM_2.5 and secondary PM_2.5 precursors at the municipality level.

The number of premature deaths per square kilometer in rural areas is shown with shaded blue backgrounds, and that in urban areas is shown as shaded circles; the areas of the symbols are proportional to the urban populations.

Fig. 4. Spatial distributions of the relative contributions of residential emissions to total PM_2.5 exposures.

Relative contributions of residential coal (A), biomass fuels (B), cooking (C), and heating (D) to total PM_2.5 exposures are shown, respectively. Both urban (symbols) and rural (shaded background) areas are shown. Rural areas are shown at the municipality scale, and urban areas are shown as individual cities, for which the symbol areas are proportional to the urban populations. Biomass fuels are not available in urban areas.