The air that we breathe

Abstract

Air pollution remains one of the biggest and most immediate environmental threats to human health, leading to millions of premature deaths each year and the loss of millions more healthy years of life. It has been linked to a range of adverse health effects, including cardiovascular and respiratory disease, cancer, neurological effects, and birth outcomes. This month The Lancet Planetary Health publishes a collection of four Articles (three from the issue and one published online first) exploring the health impacts of ambient air pollution. In the first of these papers, Veronica Southerland and co-authors examine PM2·5 concentrations and associated mortality trends in over 13 000 cities globally between 2000–19. They find that PM2·5 concentrations and associated mortality burdens have declined in some parts of the world, but that PM2·5 remains an important public health risk factor in urban areas worldwide. Interestingly, decreasing PM2·5 concentrations (for example, African, European, and North and South American cities experienced 18%, 21%, and 29% decreases in PM2·5 concentrations) did not always correspond to a proportionate decrease in PM2·5-attributable mortality rates, revealing that other demographic factors, such as an ageing population and poor general health, are influential drivers of pollution-related mortality burdens. A second and related paper by Susan Anenberg and co-authors examined 1 km resolution NO2 concentrations (constructed by adjusting a coarser resolution dataset using land use data) along with population and baseline asthma rates to estimate paediatric asthma incidence attributable to NO2 between 2000–19 in over 13 000 urban areas worldwide. They found that in 2019, there were 1·85 million new paediatric asthma cases associated with NO2; 8·5% of all new paediatric asthma cases reported that year. In urban areas, NO2 was responsible for 16% of all new paediatric asthma cases in 2019. Over the course of the study period the number of paediatric asthma cases in urban areas that could be attributed to NO2 pollution remained steady but the rate per 100 000 children decreased by 11% as the urban population grew. Despite effective air quality management benefiting children's respiratory health in many regions, current NO2 levels contribute substantially to paediatric asthma incidence. These two papers add to the already strong evidence for the negative health effects of air pollution around the world; however, what constitutes safe levels of air pollutants is still under investigation and there is some evidence that even very low levels of air pollution can have negative health consequences. Massimo Stafoggia and co-authors address this question by investigating associations between low-level air pollution (PM2·5, NO2, black carbon, and O3) and mortality in large population-based cohorts from Belgium, Denmark, England, the Netherlands, Norway, Italy, and Switzerland. They find that long-term exposure to levels of PM2·5 and NO2 well below European annual limit values, US EPA standards and WHO air quality guidelines was associated with mortality across the seven large European cohorts. Common emissions sources, primarily related to fossil fuel combustion, mean there are many links between air pollution and climate change policy and indeed a number of modelling studies have shown that climate policies have substantial health co-benefits through reduced air pollution. The final paper in this collection by Lara Aleluia Reis and co-authors investigates whether there might be an optimal climate change and air pollution policy mix. To do this they developed and implemented a benefit–cost, integrated air quality climate modelling framework that seeks to maximise regional welfare, internalising air pollution's economic impacts on human mortality under climate constraints. They find that accounting for air pollution's economic impacts leads to an estimated 1·62 million lives saved by 2050, three times their estimated co-benefits of climate policies alone. This strongly suggests that air quality controls are needed even if ambitious decarbonisation policies are in place and that these need not jeopardise climate policy objectives. Furthermore, they find that global and regional welfare increases when air pollution impacts are internalised, with no negative repercussions on global inequality. WHO recently revised their Global Air Quality Guidelines, recommending much more stringent pollution limits to protect health. The papers highlighted here reveal the tremendous potential for improved health and wellbeing as well as climate policy synergies if tackling air pollution is made a political priority.