Spring is not the only thing in the air

Warmer days are welcome, but this is often our most polluted time of year, with agriculture one of the biggest culprits

Longer days are here at last, but in terms of air quality, spring is often our most polluted time of year. Pollutants left over from the northern hemisphere winter cause increased ozone at ground level. Coastal areas are most vulnerable and the problem tends to move south through spring.

During March, ozone on Shetland reached four on the UK's 10-point warning scale. Heavy fertiliser use and spreading manure that was stored over winter causes big releases of ammonia each spring. This reacts chemically with pollution from traffic and industry to create particles that can stay in the air for a week or more. These caused pollution to reach eight on the UK's 10-point scale across England in February, and six during March.