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Abstract. The rapid growth of economy makes China the largest energy consumer and sulfur dioxide (SO 2 ) emitter in the world. In this study, we estimated the trends and step changes in the planetary boundary layer (PBL) vertical column density (VCD) of SO 2 from 2005 to 2015 over China measured by the Ozone Monitoring Instrument (OMI). We show that these trends and step change years coincide with the effective date and period of the national strategy for energy development and relocation in northwestern China and the regulations in the reduction of SO 2 emissions. Under the national regulations for the reduction of SO 2 emissions in eastern and southern China, SO 2 VCD in the Pearl River Delta (PRD) of southern China exhibited the largest decline during 2005-2015 at a rate of −7 % yr −1 , followed by the North China Plain (NCP) (−6.7 % yr −1 ), Sichuan Basin (−6.3 % yr −1 ), and Yangtze River Delta (YRD) (−6 % yr −1 ). The Mann-Kendall (MK) test reveals the step change points of declining SO 2 VCD in 2009 for the PRD and 2012-2013 for eastern China responding to the implementation of SO 2 control regulation in these regions. In contrast, the MK test and regression analysis also revealed increasing trends of SO 2 VCD in northwestern China, particularly for several "hot spots" featured by growing SO 2 VCD in those large-scale energy industry bases in northwestern China. The enhanced SO 2 VCD is potentially attributable to increasing SO 2 emissions due to the development of large-scale energy industry bases in energy-abundant northwestern China under the national strategy for the energy safety of China in the 21st century. We show that these largescale energy industry bases could overwhelm the trends and changes in provincial total SO 2 emissions in northwestern China and contribute increasingly to the national total SO 2 emissions in China. Given that northwestern China is more ecologically fragile and uniquely susceptible to atmospheric pollution than the rest of China, increasing SO 2 emissions in this part of China should not be overlooked and merit scientific research.

Food ingestion is a major route for human exposure and body burden to dioxins. We estimated the potential influence of changes in dietary patterns in Chinese population on human health risk to 2,3,7,8-TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) over the last three decades. We performed multiple modeling scenario investigations to discriminate the contribution of 2,3,7,8-TCDD emissions and changes in dietary patterns to the cancer risks (CR) to dioxins. Results showed that changes in dietary patterns, featured by decreasing consumption of total grain (including all unprocessed grains) and vegetables and increasing intake of animal-derived foodstuffs, caused increasing CR from 7.3 × 10−8 in 1980 to 1.1 × 10−7 in 2009. Varying dietary patterns contributed 17% to the CR of Chinese population in 2009 under the fixed emission in 1980. The CR to 2,3,7,8-TCDD in urban and eastern China residents was higher considerably than those who lived in rural area and western China, attributable to higher emissions, household income, and greater intake of animal-derived foodstuffs in urban and eastern China inhabitants. On the other hand, more rapid increasing trend of the CR was found in rural residents due to their more rapid increase in the consumption of fat-dominated foods as compared with urban residents.

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