Since Prime Minister Li Keqiang declared war against air pollution in March 2014, five years have passed. Last year, reports were coming out spreading good news. For example, concentrations of fine particulate matter with an aerodynamic diameter of 2.5 microns or less, known as PM2.5,were down, on average, by 32 percent from 2014 to 2018(Greenstone, 2018). Awareness about air pollution has also skyrocketed, so much so that no Chinese would likely tell me that the air pollution we see in the sky is just fog, as they used to in 2006 when I first visited Beijing. Some were going so far as to state that China was winning in the war on air pollution based on the significant progress it has made on improving air quality at the beginning of 2018.
As clearly seen in Figure 1(BeijingAirNow), the number of days with heavy or extremely heavy pollution in Beijing have reduced substantially since 2013, and days with excellent air quality have increased over the five years. In Beijing, the annual average PM2.5concentrations dropped to 58 micrograms per cubic meter (μg/m3) in 2017, meeting the 2013 action plan to improve air quality in the region around the capital(Xu and Stanway, 2018). Of course, the data need to be taken with a grain of salt as the standard used here for PM2.5in Beijing is an annual average concentration of 75 μg/m3 or less, which is substantially higher than the official national standard of 35 μg/m3, as well as the standard of the World Health Organization (10 μg/m3), the U.S. (12 μg/m3), or EU (10 μg/m3), as I discussed in 2014 (Saikawa, 2014). Still, Beijing’s PM2.5 was 35 percent lower in early 2018 compared to 2013, and such a decrease is significant; some argue that it is equivalent to the change that took 12 years in the U.S. (Greenstone, 2018).
Figure 1. Difference in air quality in five years in Beijing
Air Pollution Policies
What has been done to combat air pollution in China? One of the major changes was probably the replacement of the main household energy source from coal to natural gas. Since 2017, the Chinese government says around four million homes in the North have seen the change(Yu, 2018). This energy transition is important because it impacts not only ambient air pollution but also household air pollution (HAP). After all, we are interested in reducing air pollution mainly because of the large health problems it creates. Exposure to air pollution leads to substantial adverse health impacts, such as cardiovascular and respiratory diseases. The latest Global Burden of Disease (GBD) study estimated that in 2017, more than 1.6 million deaths were attributable to HAP exposure from solid fuels, and 3.4 million deaths were attributable to ambient air pollution (Stanaway et al., 2018).
For the past five years, my research group has worked on measuring HAP in three different parts of Tibet. We have been interested in assessing residents’ exposure to HAP, their awareness of HAP, and the link between the two. Until the late 1990s, most Tibetan nomads lived in black woven yak hair tents. Today, these yak hair tents are scarce in all nomadic villages we visited, as most nomads have transitioned to store-bought plastic tarp tents, which are lighter, better waterproofed, and easier to set up, or to temporary houses that are more spacious and comfortable. This transition is important because of the type of stove used in each household. In yak hair tents, residents have an open fire using an iron ring or a homemade adobe mud stove with an opening in the ceiling of the tent for ventilation (Sclar and Saikawa, 2019). Tarp tents or temporary houses, on the other hand, utilize improved cast iron cookstoves with stovepipes that vent the smoke through the ceiling. In Nam Co in the Tibetan Autonomous Region, we found that four households out of 23 used natural gas instead of yak dung (Xiao et al., 2015). Those households had the lowest six-hour mean PM2.5concentrations (43 μg/m3) compared to others varying from 178 – 1530 μg/m3, and those were also the only houses meeting the national 24-hour standard of 75 μg/m3. In some households in Tibet, the instantaneous PM2.5concentrations went as high as 157,000 μg/m3(Sclar and Saikawa, 2019). It clearly showed that the fuel type was an important factor for HAP, and the transition to natural gas was reducing both HAP and ambient air pollution at the same time.
While the residential sector clearly plays an important role for PM2.5, industry is also equally or more important, especially for those areas close to it. Steel, aluminum and cement producers were told to cut output by as much as 50 percent in the winter of 2016-2017 (October-March) in the region surrounding Beijing to avoid smog (Lelyveld, 2018). This was a part of the “Airborne Prevention and Control Action Plan (2013-17),” which targeted Beijing, Tianjin, and Hebei to reduce emissions by implementing strict policies (Greenstone, 2018). A similar action plan was issued for the Fenwei Plain and also in the Yangtze River Delta region as well.
In 2013, $277 billion was pledged by China’s Academy for Environmental Planning to mitigate urban air pollution (Yu, 2018). In addition to closing down industry, China prohibited new coal-fired power plants, restricted the number of cars on the road, banned high-emission vehicles, and shut down coal mines (Greenstone, 2018, Xu and Stanway, 2018). These strategies make sense, as two other important sectors for air pollution are power and transport (Saikawa et al., 2017).
Air Quality Trends in Cities
Unfortunately, the air quality trend has not continued to improve from 2018 onward. Although the clear sky was visible at the start of 2018, by the end of November, smog was thick again in the sky, with pollution levels 10 percent higher than in 2017(Stanway, 2018). In the 2018-2019 winter period, for example, air pollution levels increased by 10 percent from the previous year(Hu, 2019).
It is not fair, however, to blame a lack of policies or enforcement because air quality does not solely depend on emissions. Terrain and meteorological conditions are also important. Researchers have found that atmospheric transport of pollution to downwind areas and stagnant meteorological conditions are equally important factors linked to the severe air pollution episodes in northern China (Zhang and Cao, 2015, Sun et al., 2016, Wang et al., 2017). It is also important to note that this past winter was one of the coldest years on record in China, with snow in Shanghai, which most likely also increased the heating demand across the country (Leister and Richards, 2018). Henan province government officials had a point when they explained their 27 percent increase in PM2.5concentrations, which was the highest across China, as a result of “unfavorable weather conditions(Stanway, 2019).”
Despite the closures of coal-fired power plants across China in 2017, there was a report of satellite imagery showing pre-construction and/or construction phases of new coal-fired power plants again. It appeared that the quick and stringent regulations backfired and led to the national government loosening restrictions on these plants in five provinces in early 2018(Hao, 2018). The 13thFive-Year Plan limits the total coal power capacity to 1,100 gigawatts. The current capacity is 993 gigawatts. Adding 46 gigawatts found in pre-construction and construction mode and 57 gigawatts of shelved projects would bring the total to 1,096 gigawatts, allowing China to stay just below the plan ceiling by 2020 (Hao, 2018).
Despite last year’s early celebration that China was winning in the war on air pollution, the war does not seem to be ending just yet. In the summer of 2018, China published a new three-year action plan on air pollution that added no new targets to the existing policies (Ma, 2018). The question now is whether China can maintain its commitment to improving air quality. With the signs of renewed construction of coal-fired power plants, what we should be prepared for may be higher PM2.5concentrations again this coming winter.
China’s war on air pollution is also not just about PM2.5. Some researchers are finding that even when PM2.5 concentrations were going down, another important air pollutant, tropospheric ozone (O3), was going up. Stratospheric ozone, higher up in the atmosphere, is a good ozone, protecting us from the harmful ultraviolet radiation. Tropospheric ozone, on the other hand, is a bad ozone and is an air pollutant, having harmful health impacts. O3is not directly emitted but is produced in the atmosphere through a chemical reaction under sunlight. Li et al. (2018), for example, have shown that O3increased since 2013 after the decrease in PM2.5concentrations, especially in megacities such as Beijing and Shanghai. The researchers explain that this increase may be due to the decrease in PM2.5concentrations reducing the sink of hydroperoxyl radicals and enhancing O3production.
In our work, we also found a similar trend of increased O3concentrations in future simulations (Zhong et al., 2019). We assessed the sensitivity of health estimates due to PM2.5and O3exposure in China in 2050 to various uncertainties, including emissions, concentration-response function linking the relationship between air pollution exposure and health impacts, and population projections. We found that concentration-response function is the largest source of uncertainty for PM2.5-related health estimates, while future emissions are the greatest source of uncertainty for estimated O3-related health outcomes in China. Other parameters are much less influential compared with emissions. Our results highlight the importance of constraining emissions to better assess PM2.5– and O3-related human health impacts. It is important to mention that the projected changes in future O3 are much more variable. Eight out of 12 cases show that at least 50 percent of future population will be exposed to higher O3, while in all cases, more than 80 percent of the future population would be subjected to reduced PM2.5exposure.
The Chinese government also recognizes the increase in O3concentrations and made a statement that in 74 cities, they increased by 10.8 percent from 2013 to 2016(Ministry of Ecology and Environment, 2017). Among 338 areas, 59 cities observed O3levels above the second national standard. In 2017, based on the increasing trend, the Chinese government emphasized the importance of volatile organic compounds (VOCs) emission reduction. Nitrogen oxides (NOx) and VOCs are the major sources of O3production. The chemical reaction to produce O3is non-linear and thus the effective control depends on the existing mix of chemicals. China’s case illustrates an example of where the efficient O3reduction results from a reduction in VOCs, and not in NOx(Saikawa et al., 2017).
It is important to realize that both PM2.5and O3also affect climate and so we are not just dealing with air pollution. Reducing O3concentrations can improve air quality and climate at the same time. However, to make the matter more complicated, PM2.5can both cool and warm the atmosphere, depending on its chemical composition. So, reducing PM2.5concentrations does not necessarily translate to a win-win situation of improving air quality and mitigating climate change at the same time. Considering the health impacts associated with PM2.5exposure, reducing their concentrations is important for human welfare, but more efforts are also essential to reduce greenhouse gas emissions and to mitigate climate change.
Air pollution is complicated and is also linked to other problems, such as food production. Crop yields can be significantly reduced by being exposed to air pollution, especially O3(Van Dingenen et al., 2009, Avnery et al., 2011). In China, because of the change to natural gas in residential homes, domestic fertilizer production was also directly affected in 2017. China is the largest nitrogen fertilizer consumer in the world (International Fertilizer Association, 2019) and it has relied on its domestic fertilizer production. However, because of the shortage of natural gas this winter, fertilizer production was cut in half. This decline led to a spike in agricultural production costs and a sharp increase in prices for urea, synthetic ammonia, and compound fertilizers(Gu and Mason, 2018).
Looking Ahead in the War on Air Pollution
Many of the studies give us more reason to look at the inter-related issues of pollution holistically rather than to focus on one specific problem. It is probably time to start linking multiple problems. These can include air pollution, climate change, and water pollution, but we might also start linking ecosystem conservation and sustainable production, and other social issues. Multiple improvements in diverse fields would be possible; it is important to look at our environment as a complex system, with multiple components. One such mechanism might be to find food production methods that do not emit so much greenhouse gas and air pollutants. China’s large fertilizer consumption is leading to large nitrous oxide emissions from farms (Saikawa et al., 2014). It is a great beginning to switch household fuel from coal to natural gas, but it is also time to emphasize the need for reduced fertilizer use in China’s agricultural fields. We forget how agriculture is linked to air pollution and soil pollution sometimes and yet, it is significant. Individuals can also do things to make our planet more sustainable. Instead of relying on the governments, maybe it is also time to consider what different ways are available for us to be closer to more blue-sky days in the coming years.
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