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.

Industry and new vehicles have to meet ever tightening emission standards, but targets for controlling ammonia from farming are less ambitious. Over-use of fertiliser costs farmers money. It harms our rivers and our air and releases powerful greenhouse gases. Ammonia from farming decreased substantially in the early 1990s, but progress has stalled since. In Turkey and eastern Europe it has increased, while Denmark halved ammonia emissions between 2000 and 2010 showing what can be done.

The particles from the ammonia, traffic and industry mixture can drift a long way. Around one third of the health impacts from western Europe’s particle pollution occurs in other parts of the world, but this is not the only way that we export pollution. Based on goods traded in 2007, western Europe’s consumption of Chinese products causes around 55,000 early deaths from air pollution deaths across China each year.