Scottish air pollutant levels show sharp fall

Levels of several major air pollutants have fallen in Scotland by more than two-thirds since 1990.

The largest drop was recorded in lead, which fell by 99% between 1990 and 2015.

There was a 92% drop in sulphur dioxide over the same period, while an 83% fall in carbon monoxide was measured.

Nitrogen oxide levels are down 71% over the 25 years, a group of chemicals called non-methane volatile organic compounds (NMVOCs) which include benzene, ethanol and formaldehyde have dropped 66%, while the level of tiny particles of pollutants known as PM10 has fallen 63%.

Ammonia has fallen the least since 1990, with a 10% drop.

The latest figures in the National Atmospheric Emissions Inventory report to 2015 showed little change from the previous year - ammonia increased from 36 to 37 kilotonnes (kt) in that period, while carbon monoxide dropped from 113kt to 112kt and nitrogen oxides fell by 4kt to 84kt, driven by improvements in the energy industries.

Sulphur dioxide showed the largest change year on year, falling from 30kt to 23kt, also due to a drop in energy industries, while NMVOCs rose three kt to 140kt mainly due to a rise in emissions from industrial processes including the whisky industry, which contributes around 42% of total Scottish emissions.

Both lead and PM10 remained the same at 3kt and 12kt respectively.

The report also revealed the increasing use of wood-burning stoves in homes are leading a rise in carbon monoxide and PM10 in the residential and other combustion category.

Statisticians point out the uncertainties around the estimates for any given year are "considerable'' and trends over time are likely to be more reliable, with the uncertainty rating high for ammonia, carbon monoxide and PM10, moderate for NMVOCs and lead and low for nitrogen oxides and sulphur dioxide.