Long-term decrease in air pollutants, report finds

Defra report covering 1970-2011 shows long-term decrease in UK air pollutant emissions but a slowing in particulate matter and sulphur dioxide emissions in recent years, writes Michael Holder

There has been a long-term decrease in various air pollutant emissions in the UK in the last 40 years, according to a Defra report.

However, the ‘Emissions of air pollutants in the UK, 1970-2011’ report shows that the decline in particulate matter and sulphur dioxide since 1970 has slowed in recent years.

Graph showing UK air pollutant emissions from 1970-2011

Defra graph showing UK air pollutant emissions from 1970-2011

Also, the report shows an increase in levels of ammonia emissions in each of the last three years by a total of 4%. Defra believes this is partly due to the increased use of urea as a nitrogen-containing fertiliser in agriculture and also the wider use of anaerobic digestion for waste management.

Among various impacts on UK ecosystems, ammonia can also contribute to poor air quality by reacting in the atmosphere to form fine particles that can cause respiratory health problems.

The news follows a Defra report published in April 2012, ‘Air quality statistics in the UK, 1987 to 2011’, which found that despite long term improvements there had been little change in air quality figures in recent years (see story here

Overall, the 1970-2011 report covers UK emissions of sulphur dioxide (SO2); nitrogen oxides (NOx); non-methane volatile organic compounds (NMVOCs); ammonia (NH3); and particulate matter (PM10 and PM2.5) — all of which there has been a decline of during the last 40 years.

According to Defra, the UK has met EU member state targets set out in the National Emissions Ceilings Directive (NECD) to reduce emissions of all of these pollutants. Similar increased targets for EU member states by 2020 for reducing these pollutants have been established in the 1999 Gothenburg Protocol, which was revised in May 2012.

Commenting on the report, a Defra spokesperson said: “We want to keep improving air quality and reduce the impact it can have on human health and the environment and after successfully achieving previous emission targets in 2010, we have now committed to further emissions reductions by 2020.

The spokesperson added: “Emissions of harmful air pollutants have fallen significantly in recent years.  The reductions have largely been driven by UK, EU and UN policies over the last two decades that have targeted improvements in industrial and road transport emissions and fuel quality.”

Regarding the overall decrease in air pollutant emissions over the last 40 years in the UK, the report states: “Reductions in air pollutant emissions are being achieved through regulatory controls and other means across industry, domestic and transport sectors. Examples include changes in fuel use (such as switching from coal to gas power stations), reducing fuel use, changes to industrial processes, pollutant capture or conversion (for example catalytic convertors on vehicles).”

It continues: “Changes in behaviour such as making more sustainable transport choices also contribute to emissions reductions. Wider economic conditions also impact on pollutant emissions.”

Pariculate matter

Despite a 77% fall in PM10 emissions and a 72% fall in PM2.5 emissions since 1970, there has only been a slight decrease in recent years.

Levels of both PM10 and PM2.5 decreased by 3% and 4.5% respectively between 2010 and 2011, while levels stayed almost the same between 2009 and 2010.

The UK has agreed to reduce PM2.5 emissions in 2020 by 30% from the 2005 total of 84,000 tonnes per year. The 2011 level stated in the report was 67,000 tonnes per year.

According to the report, emissions from road transport accounted for around a quarter of the total PM2.5 emissions and just over one fifth of the total PM10 emissions in 2011.

Nitrogen oxides

The report found that road transport still accounts for around a third of total nitrogen oxide emissions, although it states that stricter regulations and exhaust filters have helped levels to decrease since 1970.

Since 1970, emissions of nitrogen oxides have fallen by 61% and the UK has met current international targets to reduce these emissions, according to Defra.

However, the UK has agreed to reduce nitrogen oxide emissions from 2020 and beyond by 55% from the 2005 level of 1.57 million tonnes per year.

Defra believes increases in road traffic account for the steep rises in nitrogen oxide emissions between 1984 and 1989.


The report found that ammonia emissions increased by 1.6% between 2010 and 2011 and have increased in each of the last three years by a total of 4%. However, levels of ammonia recorded for 2011 still show an improvement on 2007 levels.

The report notes that emissions from agriculture accounted for 86% of total ammonia emissions in 2011.

It adds, however: “Agriculture’s contribution to the total has decreased slightly since 1980, largely due to reductions in cattle numbers and more efficient fertiliser use. However, more recently there has been increased use of urea as a nitrogen-containing fertiliser and a resulting slight increase in emissions from agriculture. The increased use of anaerobic digestion for waste management has also led to additional ammonia emissions.”


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