6. Mitigation Strategies and Practical Recommendations
The individual person can only partially protect his/her health by personal protection measures, as briefly described below and reviewed previously [135]. As suggested by the report of The Lancet Commission on Pollution and Public Health, it is more important that governments and health decision makers improve the protection of the general population, e.g., by lowering legal thresholds for air pollutants [136], which is also strongly recommended by planetary health experts [137]. The problem is that national legislation does not uniformly implement the air quality limits (e.g., average exposure to maximally 5 µg/m3 of PM2.5), as recommended by the WHO [138] and atmospheric chemistry experts [139]. Whereas the legal thresholds for annual mean PM2.5 are currently 12 µg/m3 in the USA, 10 µg/m3 in Canada, and even 8 µg/m3 in Australia, the EU still recommends an average maximum exposure of 25 µg/m3 [32], which is clearly too high, as demonstrated by significant health effects at lower concentrations [140,141]. Three prominent examples have demonstrated the dramatic health improvement and also lowering of health costs by strict adherence to higher air quality standards: (1) the pollution control measures before the 2008 Beijing Olympic Games leading to a lower output of traffic and industrial exhaust pollutants, with the dramatic improvement of air quality and beneficial health effects [142] that, however, immediately returned to the same levels as before the Olympic Games when pollution control measures were stopped. (2) A decrease in diesel emissions by new restrictive laws in Tokyo, leading to a 44% decrease in PM2.5 from traffic over the period 2003–2012 and a decrease in cardiovascular mortality by 11% (mainly due to a 10% decrease in ischemic heart disease mortality) [143]. (3) The reduction of air pollution during the COVID-19 pandemic caused by the shutdown of major factories and low transport volume was estimated to be associated with a significant decrease of up to 13,600 premature deaths in Europe [144]. Besides the legal thresholds, healthy city design (urban planning) with a lot of green spaces, placing main roads and airports to the outskirts with low population density, short distances between residences, working places, schools, shops and places of social life, and efficient ecological public transportation, contribute largely to better air quality and the improvement of (cardiovascular) health [145,146,147,148]. Providing attractive and accessible urban environments may encourage people to spend more time outdoors and facilitate physical activity. Herein, the quality of the urban green space is an important factor facilitating physical activity in older and the most susceptible populations. Numerous studies have demonstrated that increased physical activity is associated with access to, and use of, green space among senior citizen, working adults, and children. The availability of green space has also been associated with reduced prevalence of obesity and type 2 diabetes, reduced cardiovascular morbidity and mortality, improved mental health and cognitive function, improved pregnancy outcomes, and overall reduced all-cause mortality and increased life span [149,150,151,152]. In addition, the presence of trees in urban green spaces has been related with improvements in air quality, due to trees’ capacity of removing pollutants from the atmosphere [153]. This reduction can occur directly by deposition on the tree surface and/or by stomatal uptake of gases [154]. Due to the shading effect trees have on surfaces and/or the cooling effect of the water they transpire, they can also mitigate extreme air temperatures by changing microclimatic conditions on their surroundings. Thus, increasing urban green space may result in a win–win situation, related to increases in physical activity and improvements of air quality. However, a sustainable and striking improvement in air quality, e.g., by significantly lowering PM concentrations, can probably only be achieved if we quit fossil fuel-based energy sources [14,155,156]. Moreover, recent studies indicate biodiversity to be a cornerstone of human (mental) health and wellbeing. Importantly, pathways linking biodiversity to beneficial human health effects include less environmental exposures, such as air and noise pollution, as well as increased building capacities, such as green space, to promote physical activity [157,158,159].
