Recently published study reveals improvements in air quality in China over the last 25 plus years – but is the trend now set to be reveresed?

Much has been written over the past few months about the the relationship with the COVID-19 pandemic and air quality. Based on past experiences – e.g. the so-called Spanish Flu pandemic of 1918-1919 caused by a H1N1 virus – we know that the symptoms and effects of respiratory illnesses are made worse by poor air quality. We have feasible mechanisms that explain the link too – air pollution facilitates both the ability of a pathogen (such as a virus) to invade a human body, by damaging the epithelial cells that line the respiratory tract, and, once in, proceed to modulate the host’s immune response. Thus it is perhaps not so surprising that studies (e.g. by Wu et al.) have revealed a link between poor air quality and a high incidence of the most severe cases of and highest death rates due to COVID-19. Of course there are likely to be other factors at play too that are also linked to poor air quality, such as poverty, poor diet, inadequate access to health facilities etc. Therefore it is perhaps best to see poor air quality as an amplifier of the effects of existing inequalities.

A lot has also been written about the positive effects on air quality of lock-downs around the world in response to COVID-19. Reduced industrial activity and reduced travel (particularly in airplanes) have contributed to reduced pollution emissions, including those to the atmosphere. As a result, clear skies have been reported in many places where such experiences had become the subject of distant memories. But these positive effects are likely to be short-term, and unlikely to outlive lock-downs, as is already evident in some places that have seen something of a recovery in economic activity in recent weeks. They also come at a huge economic cost too, which itself will have profound, negative health effects ~ and could also reverse some of the pre-COVID-19 successes in dealing with some of the more intractable environmental problems, such as climate change, as governments focus more on the future health of national economies rather than existing international obligations. A recent article in Nature Sustainability (see here) focused on China makes the point very well that while lock-downs resulted in improvements in air quality those improvements were relatively small, were least in warmer, sub-tropical parts of the country (where a large proportion of China’s population and industry is located but where consumption of polluting fossil fuels for heating is generally lower) and came at huge economic cost. Hu et al., the authors of the study, go on to opine that the same improvements in air quality, but over the long term, could be made at a much lower cost through the implementation of anti-pollution measures targeted at individual large emitters of air pollutants.

Fortunately, when relatively short-term variations in air quality – due to, for example, lock-downs associated with disease pandemics or major sporting events such as the Beijing Olympics of 2008 – are placed in the context of air quality measurements over the longer-term, it seems that air pollution and its health effects have been reduced throughout much of China since 1997. The date 1997 is significant in China because it shortly precedes the Chinese Government’s declaration of war on air pollution in its capital, Beijing (see UN report here).

According to research recently published last month (August 2020) by Yin et al in Lancet Planetary Health it seems that improvements in air quality as a result of reductions in fine particulate matter (PM2.5) in the atmosphere have occurred across China since 1997 following implementation of a series of national and regional control measures. For example, the National Air Pollution Prevention and Control Action Plan was introduced in 2013, and this has led to widely observed reductions in ambient concentrations of PM2.5. Improvements in air quality, including indoor air quality, have also followed a ban on the use of coal for domestic heating and cooking.

Population-weighted mean ambient PM2·5 concentration in provinces of China in 1990 (A) and 2017 (B) (from Yin et al 2020)

Despite these improvements, however, the vast majority of people in China (about 80% according to Yin et al) still live in areas where air quality does not meet even the most basic World Health Organisation (WHO)’s recommended levels, and mortality rates linked to poor air quality although on the decline in many parts of the country remain high overall (over a million premature deaths due to air pollution in 2017, according to Yin et al). Major differences in mortality rates linked to air quality remain within China, presumably reflecting differences in socio-economic conditions, access to health facilities etc, with 12 provinces actually showing an increase in mortality rates over the ca 30-year long study.

China and indeed many parts of the world now stand at something of a crossroads with regard to air quality. Will recent improvements in air quality, either linked to COVID-19 related lock-downs or to policies and regulations implemented over the longer-term, be maintained into the future? Or will potentially highly polluting and health-threatening fossil fuels once again be returned to as the convenient engine of global economic growth, as they were following World War II? Such a return may now be taking place in China (see here).