Home > NAEI Index > Data and Methodology

UK Emissions of Air Pollutants 1970 to 1998
(1970 to 1996 version)      (1970 to 1997 version)

1. The following report constitutes the twelfth annual report from the UK National Atmospheric Emissions Inventory (NAEI), and is produced by the National Environmental Technology Centre.
2. UK air pollutants - This report presents the latest estimates of emissions to the atmosphere from the UK for the period 1970 to 1998 in a UN/ECE format where appropriate. The total number of pollutant species included in the 1998 annual inventory is 33- however this includes seven pollutant groups (NMVOC, Particulate Matter, PCDD/F, PAH, PCB, HFC and PFC). Of these pollutant groups size fractionation is available for particulate matter and speciation is available for: NMVOCs, PAHs and PCBs. This speciation gives individual emissions of the 500 most significant NMVOCs, the 16 PAHs identified as "priority pollutants" by the USEPA and speciated PCB emissions. The pollutants considered in this report are:

• carbon dioxide, CO₂
• methane, CH₄
• nitrous oxide, N₂O
• hydrofluorocarbons (HFC)
• perfluorocarbons (PFC)
• sulphur hexafluoride

• PM₁₀ , PM_2.5 , PM₁ , PM_0.1
• black smoke
• carbon monoxide, CO
• benzene
• 1,3-butadiene

• nitrogen oxides, NO_x
• sulphur dioxide, SO₂
• hydrogen chloride, HCl
• non-methane volatile organic compounds (NMVOC) and associated speciation
• ammonia, NH₃

• polyaromatic hydrocarbons (PAH) and associated speciation
• dioxins and furans (PCDD/F)
• polychlorinated biphenyls (PCB) and associated speciation
• pesticides

- lindane

- hexachlorobenzene

- pentachlorophenol

• heavy metals:

- arsenic, As - cadmium, Cd - chromium, Cr

- copper, Cu - lead, Pb - mercury, Hg

- nickel, Ni - selenium, Se - vanadium, V

- zinc, Zn

3. CO₂ – Emission estimates for CO₂ (as Carbon) from the UK show an overall decrease from 185 Mt in 1970 to 148 Mt in 1998. The most significant reductions arise from the public power and industrial combustion sectors. 1998 road transport emissions account for 21% of the total emission and indicate a small decrease on the 1997 emission estimates. Since 1990 total emissions have declined by 7.0%.
4. CH₄ - Estimates of methane emissions show a decline from 3.78 Mt in 1970 to 2.64 Mt in 1998. The largest sources are landfills, agriculture, natural gas distribution and coal mining. The reduced emissions are dominated by the decline in the coal mining industry- in addition, increased levels of methane recovery are now present on landfill sites. The uncertainties associated with the emission estimates of methane are high.
5. N₂O - UK emissions of nitrous oxide were 0.181 Mt in 1998. Emissions of nitrous oxide are dominated by agricultural emissions and the production of nylon and nitric acid. Reductions have primarily arisen from the production processes sector.
6. HFC,PFC and SF₆- Estimates of emissions of halocarbons which contribute to global warming are discussed. The 1998 UK emissions were 3.7 kt HFCs, 94 t PFCs and 54 t sulphur hexafluoride.
7. PM – The UK emissions of PM₁₀ declined from 0.49 Mt in 1970 to 0.16 Mt in 1998. This reflects a trend away from coal use particularly by domestic users. However, more recent increases in road transport emissions (particularly from diesel road transport) have off-set a more dramatic decline in PM₁₀ emissions. Coal use and road transport contribute 51% of UK emissions of PM₁₀ in 1998. Other PM size fractions are also included here. PM_2.5 emissions have also fallen- the largest source sector being road transport, accounting for 35% of the 1998 total emission.
8. BS - Black smoke emissions in the UK declined from 1.07 Mt in 1970 to 0.28 Mt in 1998. This is largely due to a switch away from coal to solid smokeless fuels and natural gas by domestic users. The reduction in emissions from domestic sources has been partially offset by an increase in emissions from diesel engined vehicles.
9. CO - UK emissions of CO are dominated by those from road transport (73% of UK emissions in 1998). Emissions in 1998 (4.78 Mt) represent a 43% reduction on the 8.41 Mt emission in 1970 and a 31% decrease on the 1990 emission of 6.94 Mt. The change in emissions between 1990 and 1998 is dominated by the reduction in emissions from the road transport sector, caused by the increased use of catalytic converters in cars.
10. Benzene –Fuel combustion in the road transport sector is the most significant source of benzene, accounting for some 62% of the 1998 UK emission. The use of benzene in the chemical industry give rise to stack and fugitive emissions, which sum to contribute 14% to the UK total emission.
11. 1,3-Butadiene – Emissions of 1,3-butadiene are dominated by fuel combustion in the road transport sector, which account for some 88% of the 1998 UK emission. There have been significant reductions in the emissions from this sector due to the increase in the number of cars equipped with catalytic convertors.
12. NO_x - UK emissions of NO_x were 2.50 Mt in 1970, and 2.79 Mt in 1990. However, emissions have fallen significantly to 1.75 Mt in 1998, representing a 37% reduction on the 1990 emissions estimate. This is primarily a consequence of: abatement measures in road transport, abatement measures in coal fired power stations and the increased use of other fuels for power generation. Road transport and coal combustion combine to account for 64% of UK emissions in 1998.
13. SO₂ - UK emissions of sulphur dioxide have fallen from 6.51 Mt in 1970 to 1.62 Mt in 1998. This is a result of reduced emissions from the industrial and public power sectors arising from the decreasing use of coal, and increasing use of abatement equipment. However, coal combustion still accounts for 72% of the 1998 UK SO₂ emissions.
14. HCl - UK emissions of hydrogen chloride have fallen from 0.33 Mt in 1970 to 0.09 Mt in 1998 largely as a result of declining coal use.
15. NMVOC - UK emissions of NMVOC are estimated as 2.27 Mt for 1970, 2.62 Mt for 1990 and 1.96 Mt for 1998. Reductions from 1990 to 1998 arise primarily from the road transport and industrial sectors. NMVOC emission estimates have been significantly improved since the 1997 inventory, and more certain speciation is available.
16. NH₃ - The total UK emission of ammonia for 1998 is estimated at 0.35 Mt, comparable to the 1990 estimate of 0.37 Mt. The agricultural sector dominates the total ammonia emissions, and the reductions more than offset the increased emission from the road transport sector (caused by increased use of catalytic convertors).
18. POPs – The 1998 UK emissions of persistent organic compounds may be summarised as follows: 1745 t PAH (USEPA 16), 325 gTEQ PCDD/F (grammes of "toxic equivalent" of dioxins & furans) and 2.75 t PCB. Emissions from all three of these pollutant groups have greatly decreased. Emissions in 1998 equate to decreases of 74%, 70% and 61% on the 1990 emission, for PAHs, PCDD/Fs and PCBs respectively.
19. Pb - UK Emissions of lead have declined sharply following reductions in the lead content of leaded petrol and the increasing use of unleaded petrol. Emissions in 1998 are estimated to be 1.03 kt compared with 7.56 kt in 1970. Road transport still contributes 57% of UK emissions in 1998. Emissions of other metals are also reported, and show a strongly declining trend.
20. The 1998 emission inventory indicates that many of the total emission estimates for pollutants are dominated by emissions from road transport and the use of coal see table below.

Contribution to UK 1998 emissions from road transport and coal combustion

It is therefore likely that future trends in emissions will be substantially determined by market demand and UK Government/devolved administration policies associated with these areas.

20. A copy of this report may be found at the NAEI web site (/netcen/airqual/index.html) along with a facility for local interrogation of the data and links to data on emissions in other countries.