Air pollution 2

Air pollution is a mix of different particles, gases and chemicals, the proportions of which vary by site and source. The major contributors are anthropogenic (originating from human activity), although in some circumstances natural sources may be major contributors. High levels of air pollution are a major public health risk. They can affect human health, damage crops and degrade sensitive ecosystems. In the UK, control of air quality is exercised at national level by Government, but only deals with locally produced anthropogenic emissions. This is because natural sources are uncontrollable as, to an extent, is transport of air pollution between countries. The UK Government, European Community, and WHO set guidelines and standards for levels of air pollution, based on concentrations that are considered acceptable in light of knowledge regarding health and environmental effects. The Environment Act 1995 made wide-ranging provision for the management and improvement of air quality in Great Britain. The Clean Air Strategy, adopted by the Government in 2019, forms the framework for UK Government policy on air quality. Continued exposure to air pollution generally confers a greater risk to health than discrete episodes (a notable exception being the Great London Smog of 1952, which killed at least 4000 people and was instrumental to the introduction of the Clean Air Act 1956). Sources of Outdoor Air Pollution Particulate air pollution Sources of UK emissions- Anthropogenic sources include domestic fuel burning (38%), industrial combustion (16%), industrial processes (13%), and road transport (12%). Natural sources include sea salt, disturbed dust and volcanic activity. Measurement is by mass (expressed as microns/m3 of air), which can be achieved in several ways. Measurement by gravimetric analysis or light scattering express mass as PM10 (particulate matter <10microns in diameter) or PM2.5 (particulate matter <2.5microns in diameter).  Reflectance measures the blackness of a filter. Mass can also be expressed numerically (as particle numbers per cm3 of air). These measures are normally expressed as 24-h or annual means. Gaseous air pollution Sources of UK emissions- The principal gaseous pollutants are sulphur dioxide (industry and power generation), nitrogen dioxide (vehicle emissions), ozone (generated from action of UV light on oxides of nitrogen and hydrocarbons), and carbon monoxide (vehicle emissions). Measurements are expressed as ppb or microns/m3, and for the timescale relevant to the air quality standard. Other substances Other relevant air pollutants include carcinogens (benzene; 1,3-butadiene; PAHs) and lead.

Health Effects of Outdoor Air Pollution In the case of diffuse pollution, increased particles are associated with increased mortality and increased hospital admissions for cardiopulmonary disease on a day-to-day basis. Similar effects are seen with ozone and sulphur dioxide, but to a lesser degree. Effects on asthma are limited to increased hospital admissions and, inconsistently, to symptoms and lung function. Effects of long-term exposure on disease prevalence and severity may be more marked. Studies in the USA have shown association with incidence of lung cancer (but not other cancers). Disease clusters may arise from emissions from point sources. Examples include epidemic asthma in Barcelona in the 1980s from aeroallergen-containing soybean dust release into the atmosphere during unloading processes in the city docks. The worst recorded peacetime incident occurred in Bhopal, India in 1984 when an incident at the Union Carbide (India) Ltd pesticide factory led to the release of a cloud of methyl isocyanate gas, causing over 3800 deaths. More commonly, concerns arise regarding the potential for an identified source to be a cause of disease clusters. Many disease clusters are chance events, unrelated to point sources of pollution, but can generate considerable public concern. Control Air quality standards are based on health effects worldwide, even though air pollution impacts on other factors (including crop yields and the integrity of buildings). In the UK, responsibility for air quality falls to local councils. Similar regulations apply across the UK. Currently, the UK follows the EU Ambient Air Quality Directive for threshold limit values on ambient air, but these limits are higher than the air pollution limits set by the World Health Organisation. In China, new air pollution prevention and control law came into effect in 2016 (the New Air Law). This law prioritises air quality management, strengthens enforcement, and raises standards for public data disclosure and protection measures. Cities are required to regularly release and submit definitive plans to ensure they are on track to meet national air quality targets. Control of greenhouse gas emissions is included, addressing sources including coal, vehicles, marine vessels, agricultural machinery, construction and food industries. The New Air Law also recognises public participation as a crucial part of environmental protection, encouraging the public to contribute to enforcement efforts through protection of confidentiality and, if claims are correct, reward of the reporter.