Characteristics of Individual Particles Emitted from an Experimental Burning Chamber with Coal from the Lung Cancer Area of Xuanwei, China

Pollutants emitted from household coal burning in Xuanwei, China, have been recognized as the reason for the high lung cancer mortality and morbidity rates in the area. To examine the characteristics of particles emitted from coal burning, a coal burning-dilution chamber was designed, and the individual particles emitted from the chamber at different burning stages were collected. The morphologies and elemental compositions of the individual particles were analyzed by high resolution transmission electron microscopy. Four types of particles, namely, organic particles, soot particles, S-rich particles, and mineral particles, were identified. The largest percentage of particles by number in the ignition stage, fierce-burning stage, and char-burning stage was composed of organic particles (66%), soot particles (71%), and mineral particles (73%), respectively. A distinctive characteristic was the remarkable abundance of Si- and Fe-rich particles during the char burning stage, compared with emissions from other types of coal. According to the elemental composition, 49% of the mineral particles were Si-rich, 25% were Ca-rich, 14% were Fe-rich, and 7% were Ti-rich. The Si-rich particles were partly identified as quartz (SiO_2), the Ca-rich particles were found to be CaSO_4 or CaCO_3, the Fe-rich particles were primarily Fe_2O_3 or Fe_3O_4, and the Ti-rich particles were mainly TiO_2. Notably, SiO_2 is a human carcinogen, and Fe-rich particles possess a high reactive potential with DNA-markers.