Impacts of Household Coal Combustion on Indoor Ultrafine Particles-A Preliminary Case Study and Implication on Exposure Reduction.

Ultrafine particles (UFPs) significantly affect human health and climate. UFPs can be produced largely from the incomplete burning of solid fuels in stoves; however, indoor UFPs are less studied compared to outdoor UFPs, especially in coal-combustion homes. In this study, indoor and outdoor UFP concentrations were measured simultaneously by using a portable instrument, and internal and outdoor source contributions to indoor UFPs were estimated using a statistical approach based on highly temporally resolved data. The total concentrations of indoor UFPs in a rural household with the presence of coal burning were as high as 1.64 × 105 (1.32 × 105-2.09 × 105 as interquartile range) #/cm3, which was nearly one order of magnitude higher than that of outdoor UFPs. Indoor UFPs were unimodal, with the greatest abundance of particles in the size range of 31.6-100 nm. The indoor-to-outdoor ratio of UFPs in a rural household was about 6.4 (2.7-16.0), while it was 0.89 (0.88-0.91) in a home without strong internal sources. A dynamic process illustrated that the particle number concentration increased by ~5 times during the coal ignition period. Indoor coal combustion made up to over 80% of indoor UFPs, while in an urban home without coal combustion sources indoors, the outdoor sources may contribute to nearly 90% of indoor UFPs. A high number concentration and a greater number of finer particles in homes with the presence of coal combustion indicated serious health hazards associated with UFP exposure and the necessity for future controls on indoor UFPs.

[Species of Iron in Size-resolved Particle Emitted from Xuanwei Coal Combustion and Their Oxidative Potential].

Many reports have claimed that high lung cancer mortality rate in Xuanwei is associated with the residential coal combustion. Considering iron is the main chemical element in the particles emitted from Xuanwei coal combustion, and especially, reactive oxygen species (ROS) could be generated by redox-active transition metals (TM) such as iron (Fe) in particles, therefore, raw coal samples from 4 coal mines in Xuanwei were sampled, and size-resolved particles emitted from the raw coal samples were collected by using of Andersen Five-stage High Volume Sampler. Species of iron in the raw coal sample, size-resolved particles and bottom ashes were analyzed by BCR sequential extraction method (community bureau of reference, BCR). The generation potential of·OH free radicals from coal emission particles in the surrogate lung fluid (SLF) solution was measured by using high pressure liquid chromatography (HPLC). Our results demonstrated that a large fraction of oxidizable Fe could be found in raw coal samples. However, the acid extractable, reducible and oxidizable fractions of Fe in the fly ash particles accounted for a large proportion (46%-78%) in the size-resolved particles after coal combustion. There was difference in levels of·OH free radicals generated from coal emission particles in the SLF for 24 hours among particles with different sizes. The concentration of·OH increased in both fine particles (<1 µm, 1.1-2 µm, 2-3.3 µm) and coarse particles (3.3-7 µm, >7 µm) as the particles size decreased. Linear correlation could be found between the oxidizable fractions of iron and the generation of·OH in particles emitted from coal combustion (R2=0.32).