br China experienced unprecedented heavy smog pollution in t
China experienced unprecedented heavy smog pollution in the winter of 2016–17. Northern Chinese areas surrounding Beijing suffered most seriously. At the beginning of 2017, the Ministry of Science and Technology of China started to implement a special focus research programme on the causes and control technology of air pollution with financial input of ¥2·47 billion, and the Beijing Municipal Government released its 13th 5-year plan (2016–20) for environmental protection and kainate receptors construction. Both events emphasised a series of plans, goals, and measures and aimed to understand why, how, and from where the smog arises. These questions are complicated to answer because the smog pollution has been attributed to various sources and mixed chemical reactions between the source pollutants. At the same time, concerns over the health effects of heavy smog pollution are rising, increasing the need to better understand the interlinkages. Existing knowledge on the health impacts of smog pollution is mostly based on statistical records of patients and mortalities, which are descriptive but lack deeper insights in the context of China. So far, no systematic understanding exists of the causal chain from smog conditions to human exposure and health outcomes (eg, diseases). Because there might be no immediate solution to stop smog pollution, it is especially important to reduce its impacts on humans as soon as possible. But recent strategies of addressing smog are overwhelmingly focusing on the physical conditions of smog exposure and not on the human side. One of the most pressing and urgent problems is that polluted air can severely endanger human health and life. Individual residents who are affected by smog pollution can often do very little to prevent it, but they can apply adaptive and protective measures to reduce their risk. At the individual level, although people cannot prevent the smog, they can diminish their exposure to it. For example, people often prefer to drive instead of taking public transport to be less exposed to open air, which however goes against the government strategy of encouraging less driving to mitigate emissions that contribute to smog pollution. The real situation is much more complicated, as many people change their normal lifestyles and habits in response to poor air quality, whereas others continue outdoor activities and wear a mask. Thus our understanding on actual behaviour patterns of urban individuals is insufficient, and typical Chinese daily lifestyles differ from western ones. Only a few studies have discussed the interlinkages of travel behaviour and exposure to smog pollution. But they did not focus on the related health risks. Many key questions remain to be answered: how long and to what degree are different urban residents exposed to smog concentrations? How could the individual exposure be measured considering local people\'s typical daily life habits? How does the accumulated exposure affect the human respiratory system? How promising are people\'s spontaneous measures (eg, wearing a mask or using indoor air purifiers)? What are the best strategies to avoid and prevent smog impacts? To address knowledge deficits on these aspects, new scientific approaches are needed. Reduction of the health effects of smog will require a deeper understanding of the unprecedented complexity of exposure to smog pollution associated with individual actions. Very little is known about these effects, in particular in the Chinese urban environment, since they are strongly related to people\'s culture and habits that lead to specific daily activities and behaviours. In addition, the human body has some capacity to adapt to smog impacts, but there are thresholds. Cumulative exposures that exceed such thresholds will threaten health. It is a challenge to quantify the accumulation of exposures, which highly depends on individual daily routes and behavioural routines. It is also a challenge to identify the relevance of exposure to sickness, as well as the biochemical reactions of pollutants in the body.