A chronology of global air quality

Abstract

Air pollution has been recognized as a threat to human health since the time of Hippocrates, ca 400 BC. Successive written accounts of air pollution occur in different countries through the following two millennia until measurements, from the eighteenth century onwards, show the growing scale of poor air quality in urban centres and close to industry, and the chemical characteristics of the gases and particulate matter. The industrial revolution accelerated both the magnitude of emissions of the primary pollutants and the geographical spread of contributing countries as highly polluted cities became the defining issue, culminating with the great smog of London in 1952. Europe and North America dominated emissions and suffered the majority of adverse effects until the latter decades of the twentieth century, by which time the transboundary issues of acid rain, forest decline and ground-level ozone became the main environmental and political air quality issues. As controls on emissions of sulfur and nitrogen oxides (SO₂ and NO_x) began to take effect in Europe and North America, emissions in East and South Asia grew strongly and dominated global emissions by the early years of the twenty-first century. The effects of air quality on human health had also returned to the top of the priorities by 2000 as new epidemiological evidence emerged. By this time, extensive networks of surface measurements and satellite remote sensing provided global measurements of both primary and secondary pollutants. Global emissions of SO₂ and NO_x peaked, respectively, in ca 1990 and 2018 and have since declined to 2020 as a result of widespread emission controls. By contrast, with a lack of actions to abate ammonia, global emissions have continued to grow. This article is part of a discussion meeting issue 'Air quality, past present and future'.

Keywords: acid rain; air quality; eutrophication; ozone.

Figure 1.

John Evelyn and the title page of Fumifugium (1661). (Online version in colour.)

Figure 2.

The decline in SO₂ and smoke in London following the Clean Air Act (1956), including data from the ‘bubbler method’ sampling air through a peroxide solution in water and ultraviolet (UV) spectroscopy. (M. L. Williams, personal communication, 2017). (Online version in colour.)

Figure 3.

Global and regional emissions of SO₂, NO_x, NH₃ and NMVOC between 1750 and 2010. Adapted from Hoesly et al. [37]. The dots show global estimates of an earlier study (CMIP5 [38]). (Online version in colour.)

Figure 4.

Annual mean European SO₂ concentrations (µg m⁻³) in 1970, at around the time of peak SO₂ emissions, modelled using EMEP4UK with 1970 emissions and 2012 meteorology (M. Vieno et al., personal communication, 2020). (Online version in colour.)

Figure 5.

Distributions of the population as a function of annual (2013) average ambient PM_2.5 concentration for the world's 10 most populous countries and the rest of the world. Dashed vertical lines indicate World Health Organization Interim Targets (IT) and the Air Quality Guideline (AQG). Source: Brauer et al. [107]. (Online version in colour.)

Figure 6.

Trends in the tropospheric NO₂ column over East China between 1995 and 2018 (A. Richter and J. P. Burrows, personal communication, 2020). (Online version in colour.)

Figure 7.

Annual emissions of (a) SO₂, (b) NO_x and (c) NMVOC in China between 2010 and 2017 (adapted from Zheng et al. [115]). (Online version in colour.)

Figure 8.

Annual death rates attributed to outdoor PM_2.5, outdoor ground-level ozone and indoor pollution from solid fuels 1990–2017. Source: www.ourworldindata.org/air-pollution/ based on data from the Global Burden of Disease project. (Online version in colour.)