Air pollution and China's ageing society
Authors: John S Ji
Journal: The Lancet Public Health (2018)

During the cold winter of 1952, low temperature and high concentrations of air pollution from factories and coal-burning homes caused an excess of 4000 deaths in London.1Logan WPD Mortality in the London fog incident, 1952.Lancet. 1953; 261: 336-338Abstract Scopus (344) Google Scholar This episode, commonly known as the Great Smog of London, instigated public recognition of, and scientific research into, the harms of air pollutants. More than half a century later, China is similarly experiencing a burgeoning public awareness of fine particulate matter (PM2·5). In 2008, the US Embassy in Beijing began collecting real-time air-quality data on its rooftop and disseminated readings on Twitter. Demands for ambient air-quality information followed, leading to more than 5000 monitoring stations built across the country by 2017.2Zheng J Monitoring network to be further expanded.http://www.chinadaily.com.cn/china/2017-04/07/content_28827498.htmDate: 2017Date accessed: August 6, 2018Google Scholar Mandates were given to governmental authorities at various levels to monitor air pollutants (including PM2·5, PM10, sulphur dioxide, nitrogen dioxide, ozone, and carbon monoxide), although data reliability has been questioned.3Ghanem D Zhang J Effortless perfection: do Chinese cities manipulate air pollution data?.J Environ Econ Manage. 2014; 68: 203-225Crossref Scopus (205) Google Scholar Declining concentrations of PM2·5 can have an important effect on the lifespan of Chinese people. According to WHO, air pollution alone causes 6·5 million deaths worldwide each year.4WHOSeventy-First World Health Assembly. Health, environment and climate change.http://apps.who.int/gb/ebwha/pdf_files/WHA71/A71_10-en.pdfDate accessed: August 20, 2018Google Scholar Air pollution is a particularly important risk factor in China: according to estimates from the Global Burden of Disease study,5IHMEChina.http://www.healthdata.org/chinaDate accessed: August 21, 2018Google Scholar air pollution is the fourth leading cause of death and disability combined (behind dietary risks, high blood pressure, and tobacco). With China aiming to raise the average life expectancy from 76·3 years in 2015 to 79·0 years by 2030, as described in the Healthy China 2030 plan,6Ministry of Ecology and Environment of the People's Republic of ChinaReport on the state of the ecology and environment in China.http://english.mep.gov.cn/Resources/Reports/soe/SOEE2017/201808/P020180801597738742758.pdfDate: 2017Date accessed: August 20, 2018Google Scholar air pollution must be curbed. Increased political will and tightened regulations have led to progress: average PM2·5 concentrations in the Beijing-Tianjin-Hebei, Yangtze River Delta, and Pearl River Delta regions were 39·6%, 34·3%, and 27·7% lower, respectively, in 2017 than in 2013.7Yang J Siri JG Remais JV et al.The Tsinghua–Lancet Commission on Healthy Cities in China: unlocking the power of cities for a healthy China.Lancet. 2018; 391: 2140-2184Summary Full Text Full Text PDF PubMed Scopus (111) Google Scholar However, urban air pollution remains high, with average PM2·5 concentrations in 2017 of 58 μg/m3 in Beijing and 39 μg/m3 in Shanghai. These concentrations are still far from the WHO air quality annual mean threshold of 10 μg/m3. An ageing society and urbanisation change the number of people exposed to harmful air pollution. In the past few decades, China has experienced a large rural-to-urban migration, with more than half of the country's population now residing in cities.6Ministry of Ecology and Environment of the People's Republic of ChinaReport on the state of the ecology and environment in China.http://english.mep.gov.cn/Resources/Reports/soe/SOEE2017/201808/P020180801597738742758.pdfDate: 2017Date accessed: August 20, 2018Google Scholar Identifying the harms of air pollution is crucial to improve policy making. In The Lancet Public Health, Tiantian Li and colleagues8Li T Zhang Y Wang J et al.All-cause mortality risk associated with long-term exposure to ambient PM2.5 in China: a cohort study.Lancet Public Health. 2018; 3: e470-e477Summary Full Text Full Text PDF PubMed Scopus (150) Google Scholar present timely research on the association between PM2·5 exposure and premature mortality. The study is based on the Chinese Longitudinal Healthy Longevity Survey of individuals aged 65 years and older, which has more than 14 years of follow-up and which surveys participants roughly every 2 years. This cohort includes individuals from 22 of 31 provinces to encompass China's geographical diversity. The investigators used residential addresses of participants to ascertain PM2·5 exposure concentrations through remote sensing in 1 km × 1 km satellite-imaging grids. Study participants had varying dates of entry into the study, and the investigators used a Cox proportional hazards model to account for time at risk and calculated hazard ratios (HRs) for risk of mortality that were adjusted for confounders and predictors. The investigators estimated an adjusted HR of 1·08 (95% CI 1·06–1·09) for each 10 μg/m3 increase in PM2·5 concentration. This estimate is similar to those from other large cohort studies of low-concentration air pollution.9Zhang J Low-level air pollution associated with death: policy and clinical implications.JAMA. 2017; 318: 2431-2432Crossref PubMed Scopus (16) Google Scholar China is a heterogeneous country: although most cities have high concentrations of PM2·5, many places have reasonably low concentrations. In the study by Li and colleagues, the annual average PM2·5 concentration ranged from 7 to 113 μg/m3. The authors found a higher risk of premature mortality in areas with lower concentrations of PM2·5 (<60·9 μg/m3; HR 1·14 [95% CI 1·11–1·17]) than in areas with higher concentrations of PM2·5 (≥60·9 μg/m3; 1·07 [1·01–1·12]). This finding is informative, showing risks at different concentrations of pollutants in different populations.10Landrigan PJ Fuller R Acosta NJR et al.The Lancet Commission on pollution and health.Lancet. 2018; 391: 462-512Summary Full Text Full Text PDF PubMed Scopus (1963) Google Scholar The authors also provide insight on differences between urban versus rural settings and northern versus southern regions. In particular, individuals living in rural or southern regions of China were more susceptible to the effects of air pollution than were individuals living in urban or northern regions. The concentration–response finding from this study confirms that there is no safe concentration of PM2·5. Some questions remain to be explored. First, evidence is sparse for ozone and its interactive effect with PM2·5 on mortality. Second, China has the largest number worldwide of people who smoke, and epidemiological evidence is needed for the interactive effect of smoking and PM2·5 exposure, particularly on incidence of lung cancer, which is increasing in the country. Third, cause-specific mortality in addition to all-cause mortality should be studied to further understand the effect of PM2·5. Lastly, air pollution avoidance behaviours, such as use of filtration devices and real-time monitoring systems (eg, smog alerts), need to be assessed as viable public health intervention strategies. I declare no competing interests. All-cause mortality risk associated with long-term exposure to ambient PM2·5 in China: a cohort studyLong-term exposure to PM2·5 is associated with an increased risk of all-cause mortality among adults aged 65 years and older in China, but the magnitude of the risk declines as the concentration of PM2·5 increases. Full-Text PDF Open Access