Scottish Government

Key Scottish Environment Statistics 2003

air quality

Particulate (PM₁₀) Concentrations: 1992-2002

Particulate pollution can harm the human respiratory and cardiovascular systems, and is linked to asthma and mortality. Smaller particles are the most damaging and current targets focus on particles less than 10m in diameter (PM ₁₀).

The greatest source of PM ₁₀ is combustion. In particular, road transport and domestic sources each account for around 20% of UK emissions of PM ₁₀. ² Other sources are mining, construction, secondary reactions between nitrates and sulphates, and suspended dusts and pollen. Between 1990 and 2001, UK emissions of PM ₁₀ fell by 44%. ²

The Air Quality Strategy3 objectives for PM ₁₀ come in two stages. Stage 1 (to be met by the end of 2004): a 24-hour mean of 50g/m3 not to be exceeded more than 35 times a year, and an annual mean of 40g/m3. Stage 2 (to be met by the end of 2010): a 24-hour mean of 50g/m3 not to be exceeded more than seven times a year, and an annual mean of 18g/m3. Stage 1 objectives were met at all five automatic monitoring sites in 2002.

SOURCE: NETCEN

High concentrations of nitrogen dioxide (NO ₂) can affect human health, particularly by causing inflammation of the airways. Ecosystem health is also damaged by NO ₂ by reducing plant growth, contributing to acid deposition and promoting the formation of ground level ozone.

All combustion processes in air produce oxides of nitrogen (NO _x). Road transport accounts for about half of all NO _x emissions in the UK; this contribution is greatly increased in urban areas. Between 1990 and 2001, UK emissions of NO _x decreased by 39% ² due to the installation of catalytic converters in vehicles.

The Air Quality Strategy ³ objectives for NO ₂ (to be met by the end of 2005) are (1) an annual mean of 40g/m3 and (2) an hourly mean of 200g/m3 not to be exceeded more than 18 times a year. In 2002, the first objective was not met at three of the eight automatic monitoring sites in Scotland - Glasgow City Chambers, Glasgow Kerbside and Edinburgh Centre. The second objective was met at all automatic monitoring sites, except Glasgow Kerbside.

SOURCE: NETCEN

Carbon monoxide (CO) is a gas formed by the incomplete combustion of carbon-based fuels. The greatest threat to human health from exposure to CO is the formation of carboxyhaemoglobin. This reduces the capacity of the blood to carry oxygen resulting in drowsiness, headaches, and in severe cases unconsciousness and death.

The Air Quality Strategy ³ (AQS) objective for CO is a maximum concentration of 10mg/m3 measured as an 8-hour running mean, to be achieved by the end of 2003. In 2002, this objective was met at all seven automatic monitoring sites in Scotland.

The main outdoor source of carbon monoxide is currently road transport, in particular petrol-fuelled vehicles, which in 2001 accounted for 62% of UK emissions. ² Between 1990 and 2001, UK emissions of CO from road transport have fallen by 57%, a decline attributed to the installation of catalytic converters in vehicles.

SOURCE: NETCEN

Ozone in the stratosphere forms a layer that protects the earth against harmful ultra-violet radiation, but tropospheric (ground level) ozone is a damaging oxidant. Exposure to high ozone concentrations can cause respiratory damage, and affects vegetation by damaging leaves and reducing yields.

Ozone is formed by a slow, complicated series of reactions from other pollutants that may be blown over from Europe. The most important man-made precursors are nitrogen oxides and volatile organic compounds (VOCs) produced by road transport, industrial processes and solvent use. Ozone concentrations tend to be lower in urban areas where it is converted to nitrogen dioxide by reacting with nitrogen oxides.

The Air Quality Strategy ³ objective for ground level ozone (to be met by 2005) is for the maximum daily concentration (measured as an 8-hour running mean) of 100mg/m3 not to be exceeded more than 10 times a year. ⁷ In 2002, this objective was met at all four monitoring sites in Scotland, except Strath Vaich.

SOURCE: NETCEN

Annual means (from non-automatic stations) (g/m³)

The predominant source of atmospheric sulphur dioxide (SO2) is the combustion of sulphur-containing fossil fuels, mainly coal and heavy oils. Annual urban SO2 levels have fallen by around 75% since the 1956 Clean Air Act was introduced to combat smog.

High SO2 levels over a short period of time are important as SO2 can cause respiratory difficulties almost immediately after exposure. The Air Quality Strategy ³ objective for SO2 stipulates that a 15-minute mean of 266g/m3 should not be exceeded more than 35 times a year (to be met by the end of 2005). All four automatic monitoring sites meet this objective.

In cold weather, SO2 can contribute to acidification that damages vegetation and ecosystems. The AQS objective for ecosystem protection, a winter (1 October-31 March) mean of 20g/m3,
is currently met at all Scottish automatic monitoring stations.

SOURCE: NETCEN

Annual emissions (thousand tonnes)

Sulphur dioxide (SO2) and oxides of nitrogen (NOx) affect human health through respiratory damage, and ecosystem health through acidification. SO2 and NOx are released into the atmosphere through the combustion of fossil fuels. In 2001, large combustion plants (LCPs) accounted for 73% of the SO2 emissions and 21% of NOx emissions in the UK. ²

The revised EC LCP Directive (2001/80/EC) called for a 60% reduction in SO2 emissions by 2003 and a 30% reduction in NOx emissions by 1998, from a 1980 baseline. By 2001, UK emissions for SO2 and NOx were 76% and 63% respectively below 1980 levels. ² In Scotland, SO2 emissions from the electricity supply industry fell between 1996 and 1999, but rose in 2000. This was due to the increased use of coal-fired power stations, necessary to offset the reduced capacity of the nuclear sector because of refurbishment work at certain plants.

Acid deposition is a transboundary problem. In 1994, it was estimated that 81% of sulphur deposited in Scotland was emitted in other parts of Europe. ¹¹ Similarly, most Scottish emissions are deposited elsewhere.

SOURCE: SCOTTISH ENVIRONMENT PROTECTION AGENCY