Abstract
Xuanwei and the neighboring Fuyuan (XF) counties in Yunnan Province have the highest lung cancer incidence rates in China. Previous studies suggest that the nano-minerals released during the combustion of locally sourced "smoky" (bituminous) coal are the primary contributors to these elevated cancer rates. The coal ash generated during combustion predominantly consists of nano-minerals, which can be resuspended into the atmosphere during routine ash-handling activities. In this study, coal ash samples from XF counties and four additional provinces with lower lung cancer incidence rates were resuspended to simulate ash-handling activities and subsequently collected using a cascade PM(2.5) sampler. Individual particles were analyzed using a high-resolution scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). Based on their morphology and elemental composition, the particles were categorized into five major types: quartz, Si- and Al-rich (SiAl-rich), Ca-rich, Ca- and Mg-rich (CaMg-rich), and Fe-rich particles. The relative abundance of crystalline quartz particles was significantly higher in Xuanwei (22.2%) and Fuyuan (13.7%) compared to the other provinces, where quartz was also detected in lower concentrations. Similarly, the proportion of Fe-rich particles was notably higher in Xuanwei (10.9%) and Fuyuan (5.1%) than in other regions. These findings highlight the potential role of quartz and Fe-rich particles in contributing to the high lung cancer rates observed in XF counties. Further research is warranted to elucidate the toxicological mechanisms underlying the health effects of these particle types.