I enjoy feeling fit and healthy, but I am not good at sticking to a fitness plan that involves going to the gym and doing sets or reps on the equipment. But I do enjoy taking exercise in less formal ways; going on walks for pleasure or to get where I need to go, running around with my children in the park. Traditionally in China the most common forms of exercise have also been those that take place outdoors. However there is a conflict and it is increasing. Where do the benefits of exercising outside stop and the negative effects of pollution on our health start? This conflict is familiar to me, when I lived in London was it better for me to cycle to work inhaling everyone else’s exhaust fumes or add to the exhaust fumes myself by driving and miss out on the cardiovascular workout; and when I lived in China was it better to hop on the metro for a couple of stops or walk down busy Zhaojiabang Road.

So this week I will look at an article “Ambient air pollution in China poses a multifaceted health threat to outdoor physical activity” published in the Journal of Epidemiology and Community Health in March 2015, and some of its references to see what we know about this problem (1).

We know that exercising promotes health. There are physical and mental health benefits, and improved quality of life, and of course a decreased risk of premature morbidity and mortality. Whether there is any benefit to our health to exercise outside compared to exercising the same amount inside is more difficult to answer. A systematic review found some evidence that outdoor physical activity had benefits when compared to indoor activity (2). These benefits were generally self-reported feelings of well-being and the authors commented that strong conclusions were hampered by the poor quality of the methodology and data in the research reviewed. The other factor that needs to be considered is the air quality in the inside space being used for exercise, there is usually less polluted air inside, but if there is poor ventilation and air inlets are situated in polluted air this may not always be the case.

We also know that exercising in polluted environments can increase the risk of severe health outcomes, for example there are concurrent increases in emergency room attendances with cardiorespiratory dysfunction, for example heart attacks and asthma attacks when pollution levels are high. This article looked at whether there is also an indirect health threat because the potential for negative health consequences may ultimately prevent people from engaging in physical activity. This dilemma is particularly evident in the case of those with existing medical conditions, such as asthma, diabetes, heart or lung conditions, who could benefit from being active, but are also most susceptible to ill-effects of air pollution.

The Chinese Conundrum

This problem of where the benefits of exercising outdoors ends and risk of exercising in polluted air is of particular interest on China for several reasons. The first is the obvious high levels of air pollution which increases the potential risk when compared to many other countries. Other reasons include the fact that outdoor physical exercise has been a traditional practice in China; and the demographics of those undertaking outdoor physical exercise. Anyone who has spent any time in China will know that parks, roadsides and village squares are utilized widely for dancing, tai chi and physical therapy for recovering patients. A study looked at these types of exercise typically undertaken by middle-aged and elderly found that jogging, tai chi and dancing, with stronger effects for tai chi and dancing, are associated with a significantly lower risk of having metabolic syndrome in middle-age and older (3).

Many of the participants in these activities fall into low-income categories and are the least likely to be able to afford access to the limited number of fee-based indoor physical activities. The fact that outdoor settings can accommodate a much larger population at lower cost is also a big consideration for a China-sized population. This is also relevant at the other end of the age spectrum. In schools, indoor activities are relatively uncommon due to the lack of large indoor facilities, so most physical education curricula are outdoor-oriented. However, severe ambient air pollution may require cancellation, in some areas for days or weeks at a time, of sports for school children who constitute a major part of an increasing epidemic of overweight and obesity.

There is also evidence that increased pollution is linked to reduced outdoor leisure time. One study, from America, found that higher levels of PM2.5 were associated with decreased physical activity (4). Since both lack of exercise and high pollution are independent risk factors for cardiovascular ill-health there is the potential for a synergistic increased health-risk. Based on this many Chinese are trapped in a no-win scenario, compounded by characteristics including age, socioeconomic status and/or existing health conditions that make them more vulnerable to pollution-related health risks.

A large Asian study investigating the effects of air pollution on health found the city-combined effects of the four pollutants tended to be equal or greater than those identified in studies conducted in Western industrial nations (5). In addition, they also found that residents of Asian cities are likely to have higher exposures to air pollution than those in Western industrial nations because they spend more time outdoors and less time in air conditioning. However they concluded that it remained reasonable to apply estimates derived from previous health effect of air pollution studies in the West to Asia. Furthermore another study looking at physical activity levels in Chinese adults found that levels of activity are falling significantly due to the urbanization of the population. Between 1991 and 2006, average weekly physical activity among adults in China fell by 32% (6). We can see from all of this evidence that there are multiple compounding factors that together put a large proportion of the Chinese population at risk to their health from exposure to air pollution, or from lack of physical activity, or from both.

What is being done? What can be done? What should be done?

I don’t want to get too political in this blog, I set out to talk about health not politics. However there is of course an overlap and this article does cover this cross-over quite succinctly. In addition there has recently been a review of Chinese environmental policies and as such I felt it was worth covering here.

Increasing public pressure has pushed the central Chinese government to address the air pollution problem more seriously. The first National Action Plan on Air Pollution Prevention and Control was issued in 2012 (7). This policy requires that by 2017 PM10 concentrations be reduced by more than 10% compared with the 2012 level, and PM2.5 concentrations in the Beijing-Tianjin-Hebei Area, Yangtze River Delta and Pearl River Delta be decreased by 25, 20, and 15%, respectively. The plan also aims to reduce the number of heavily polluted days (AQI value above 200) all over China by reducing coal consumption and investing in alternative energy, public transportation and electric cars. However as with many policies there is a conflict between the government desire for the ongoing industrialisation and urbanisation process, and legislation to reduce environmentally damaging practices. It remains particularly challenging for central government policies to be effectively implemented at the local government level.

Further to the 2012 document there has been more recent legislation in the form of the revised Air Pollution Law. However commentators have highlighted where this legislation has significant omissions. For example it fails to enshrine a basic right for China’s public to have clean air, and lacks a system for environmental public interest litigation (8). The new law is also compromised by an emphasis on government statements to tackle air pollution, rather than a platform for broader organizational involvement and tangible action for example by NGOs and judicial oversight. On a more positive note the law does include articles about regional prevention and control of pollution, an alert system that gives warnings on weather conditions that worsen smog, and limits on particular levels of polluting compounds, particularly in vehicle fuels.

Currently, for example, concentrations of air pollutants in major cities, such as Shanghai and Beijing, and in various provinces can be observed in real time. These systems can provide useful information about the air quality; help track progress in reducing air pollution; and, through the AQI, inform the public when air pollution is likely to reach unhealthy levels. Although initiatives such as these are spreading geographically and becoming more widely used simply making data available is insufficient. There needs to be a way of linking current pollution levels with suggested activity guidance in order to bridge the gap between the general health benefits associated with being active outdoors and diminished health-related quality of life as a result of outdoor activity in the presence of poor air quality. Worryingly there have been no proposals related to protecting outdoor physical activity or creating more widely available affordable indoor space.

I have looked at what is being done, now let’s concentrate on where the focus should be going forward. The aim should be to raise awareness of the potential negative impact of outdoor physical activity in polluted environments, and to develop and implement public health policies that specifically combat health issues related to this emerging problem.

At a community level grass-roots campaigns to educate the local population about air quality data and the health implications for outdoor physical activity are essential. If possible these initiatives should also link into programs for safer forms of physical activity, for example away from industrial areas or main roadways (it is surprising how quickly levels of dangerous particles drop over relatively short distances), or indoor activities if available. Teaching residents how to chose and use protective devices such as filtration masks during outdoor activity to reduce exposure to pollution is another useful measure. As is modifying school physical education programs, for example perhaps by choosing times of day where pollution levels are generally lower to reduce the risk of either unsafe air quality or cancellation of physical activity. Once the monitoring technology is in place alert systems to inform the public about appropriate levels of air quality that are conducive or harmful to outdoor physical activity could be implemented.

A large barrier to any of these initiatives is that data that examines the relationship between the levels of ambient air pollution exposure and physiological responses to varying lengths of time spent exercising, physiological adaption to exercise in polluted air, long-term health consequences of exercising in a polluted area is lacking. The aim for the health authorities in China must be to address the critical dilemma of how to protect, and encourage, the active population until measures to reduce the long-term threat posed by air pollution are implemented.


morbidity — from the word morbid, a diseased state. The incidence or prevalence of a disease.

systematic review — a type of literature review that collects and critically analyzes multiple research studies or papers.

Demographics — data relating to the population and particular groups within it.

PM2.5/ PM2.5 concentrationsair pollutant particles with a median diameter of 2.5 micrometers or less, small enough to invade even the smallest airways.

metabolic syndrome — a cluster of biochemical and physiological abnormalities associated with the development of cardiovascular disease and type 2 diabetes.

PM10 concentrations — air pollutant particles with a median diameter of 10 microns.

AQI air quality index is a number used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. As the AQI increases, an increasingly large percentage of the population is likely to experience increasingly severe adverse health effects.


1. Li F, Liu Y, Lü J, et al. Ambient air pollution in China poses a multifaceted health threat to outdoor physical activity. J Epidemiol Community Health 2015;69:201—204. Published Online First 26 June 2014 doi:10.1136/jech-2014-203892

2. Thompson Coon J, Boddy K, Stein K, et al. Does participating in physical activity in outdoor natural environments have a greater effect on physical and mental wellbeing than physical activity indoors? A systematic review. Environ Sci Technol 2011;45:

3. Chen M, He M, Min X, et al. Different physical activity subtypes and risk of metabolic syndrome in middle-aged and older Chinese people. PLoS ONE 2013;8:e53258.

4. Wen X-J, Balluz LS, Shire JD, et al. Association of self-reported leisure-time physical inactivity with particulate matter 2.5 air pollution. J Environ Health 2009;72:40—4.

5. Wong CM, Vichit-Vadakan N, Kan H, et al.; PAPA Project Teams. Public health and air pollution in Asia (PAPA): A multicity study of short-term effects of air pollution on mortality. Environ Health Perspect 2008;116:1195—202.

6. Ng SW, Norton EC, Popkin BM. Why have physical activity levels declined among Chinese adults? Findings from the 1991–2006 China Health and Nutrition Surveys. Soc Sci Med 2009;68:1305—14.

7. The State Council issues action plan on prevention and control of air pollution introducing ten measures to improve air quality. Accessed from URL: http://english.mep.gov.cn/News_service/infocus/201309/t20130924_260707.htm on May 12th 2016.

8. China Dialogue. 2015. Air pollution law omits key measures in war on smog. Accessed from URL: https://www.chinadialogue.net/article/show/single/en/8156-China-s-new-Air-Pollution-Law-omits-key-measures-in-war-on-smog on May 12th 2016.