A chronology of global air pollution
Professor David Fowler CBE FRS, Centre for Ecology and Hydrology (Edinburgh Research Station), UK
Many human activities result in emissions of contaminants to the atmosphere, releasing a range of gases and particulate matter. These pollutants were recognised as a problem for human health and ecosystems long before their chemical identity was known and prior to measurements of their ambient concentrations. In fact widespread direct measurements to show the change in atmospheric composition for the reactive pollutants are limited to the last 100 years or so.
The early evidence that air pollutants were harmful was sufficient to lead to regulations to limit emissions, before measurements and thresholds for effects were established. The presentation explores the early evidence of air pollution and some of the steps taken to control it followed by a chronology developed from models and measurements of the main pollutant emissions of sulphur, volatile organic and nitrogen compounds and the products of their chemical interactions in the atmosphere.
Recent global chemistry-transport model intercomparisons provide a description of the rapid increase in sulphur and nitrogen pollutants through the early 20th century and the gradual decline in sulphur, VOC and to a lesser extent oxidized nitrogen emissions between 1980 and 2010. Measurement networks at the surface and more recently satellite remote sensing reveal the spatial and temporal detail of the changes in chemical composition over the last few decades. The presentation describes the time course of anthropogenic emissions to the atmosphere and their effects on global and regional air quality.
Air pollution and human health: research challenges and future directions
Professor Michelle Bell, Yale University, USA
A wealth of research has shown that exposure to ambient air pollution is associated with increased risk of adverse human health outcomes such as premature mortality, hospital admissions, birth outcomes, and asthma, among others. The Global Burden of Disease project estimates that air pollution is among the top ten causes of morbidity and mortality worldwide. These associations have been demonstrated through different study designs and in different populations and regions. Still many critical research questions remain. This presentation will review key findings and research needs in the field of air pollution and human health. These include the analysis of complex mixtures and the impact of climate change on air pollution and subsequently on human health. The talk will focus on future directions for such work and paths forward to address air quality and climate change in order to improve public health.
Effects of air pollution on managed and natural terrestrial habitats over the last 100 years
Dr Carly Stevens, Lancaster Environment Centre, UK
Over the last 100 years the abundance of different air pollutants, their geographic distributions and impacts on managed and natural habitats, have undergone large changes. Some pollutants, including oxidized and reduced nitrogen compounds have steadily increased, while others have declined. The concentrations and effects of sulphur compounds peaked and then declined over this time period allowing some ecosystems to recover. The potential for air quality to have an impact on the natural environment was recognised long before the twentieth century. During the nineteenth and first half of the twentieth centuries, impacts including changes in lichen distribution, moth pigmentation, bird feathers and black snow were noted. During the second half of the twentieth century, studies on the effects of air pollution became broader and much more systematic, notably due to acid deposition, tropospheric ozone and nitrogen deposition and we now know a great deal about the damage that air pollutants can cause to sensitive habitats. This presentation reviews some of the most important impacts that air pollution has had on terrestrial habitats the developed world, including the lichen deserts, forest dieback on both continents, the loss of heathland habitats in the Netherlands, and reductions in vegetation species richness. Although our knowledge base regarding the impacts of air pollution on ecosystems has increased considerably since the early twentieth century, there remain many gaps. This is especially the case in less developed regions of the world, which are experiencing increasing air pollution problems coincident with economic development.
Effects of ozone on food security and natural ecosystems
Professor Lisa Emberson, University of York, UK
The damage and injury that ground level ozone causes vegetation has become increasingly evident over the past half century with a large body of observational and experimental evidence demonstrating a variety of effects at ambient concentrations that include: visible injury, changes to plant physiology, alterations in the developmental rate of plant growth, reductions in yield, productivity and forage quality, shifts in species composition and reductions in carbon sequestration for a variety of crop, forest and semi-natural vegetation species and ecosystems. This paper explores the use of experimental data to develop dose-response relationships for use in risk assessment studies; these studies have typically identified the US mid-West, much of Europe, the Indo Gangetic plain in South Asia and the Eastern coastal region of China as global regions where ozone is currently likely to threaten food supply. Experimental data can also be used to identify thresholds for effects to support establishment of air quality guidelines for use in policy development of emission reductions for mitigation efforts. In this respect, understanding emission trends is crucial as ozone concentrations tend to follow patterns of industrialisation with key precursor pollutants being NOx and NMVOCs. However, methane (CH4), which is less tightly linked to industrialisation, is increasingly being recognised as an important determinant of global background levels of O3 pollution with implications on the appropriate geographical scale at which effective policy responses might be required. Finally, the paper also explores adaptation options to enhance ozone tolerance. Most work has focused on arable crops through identification of crop cultivars resistant to ozone or management practices that will reduce ozone exposure and uptake. Such adaptation options should ideally also consider other stresses (heat stress, water stress, soil fertility stress) that often co-occur with pollution episodes to ensure responses are appropriate. This requires an improved understanding of the mechanisms by which ozone impacts on plants (i.e. physiological processes that trigger the cascade of plant growth, development, productivity and ecosystem function responses). Such understanding is also critical for the new generation of Earth System Models that hope to incorporate pollution impacts and feedbacks on terrestrial systems.
The role of international policy instruments in improving European Air Quality
Ms Anna Engleryd, Chair of UNECE Air Convention, Swedish Environmental Protection Agency, Sweden
The acid rain issue was first identified as a problem in the early 1970s and was during the following decades one of the most discussed environmental problems in Europe and North America. Although it was initially postulated that transboundary transport was an important cause, there was initial scientific scepticism on the transboundary question, and there were certainly no coordinated international attempts to solve the problem. Eventually the scientific findings provided the foundation for a determined policy response resulting in a treaty under the United Nations’ Economic Commission for Europe (UNECE), the Convention on Long-range Transboundary Air Pollution (the Air Convention) agreed in 1979. The Convention has successively been extended with eight protocols requiring monitoring and modelling and subsequently reductions in emissions to combat acid rain and in later versions, which were based on effects-based strategies, to reduce impacts of ozone, NOx, VOCs, ammonia, particulate matter as well several heavy metals and persistent organic pollutants. Alongside the activity in the UNECE which initially focussed on damage to ecosystems, the European Union produced air quality Directives which dealt with the effects on human health, primarily in urban areas. The first Directive appeared in 1980 and dealt with ‘smoke’ and sulphur dioxide. Since then there has followed a series of ambient air legislation and Directives dealing with industrial emissions and emissions from road vehicles, as well as national emissions where the obligations mirror those in the Air Convention and extend them to longer timeframes. These actions in the EU and under the Air Convention have led to substantial reductions in emissions of many pollutants, which have resulted in positive effects on ecosystems and human health and in a virtual solution of the acid rain problem. However, despite a significantly improved situation over the last 30 years, problems still remain, especially concerning the health effects from particulate matter and the wider ecosystem issues around excess nutrient nitrogen. There is a continuing need for concerted action as well as increased cooperation in a global context to clean up the air.