We think of the countryside as being a place of fresh air. Each weekend thousands of us leave our cities to hike or cycle in rural areas or simply to enjoy time in nature. Increasing attention is being given, however, to air pollution from farming. Ammonia from fertiliser and slurry mixes with air pollution from cities, traffic and industry to add to the particle pollution that plagues many parts of the world. It is estimated that halving ammonia from farming could avoid about 52,000 premature deaths from air pollution across Europe each year and 3,000 in the UK.

Increasing attention is also being paid to bioaerosol from intensive farming. In animal houses these are tiny particles and dust from the animals themselves, their food, bedding and waste. They can also include fungi, bacteria and pollen. A recent review by Imperial College and Public Health England found evidence of respiratory problems in farm workers and raised concerns about exposure for people living close to intensive livestock farms, including some evidence of increased asthma in children. Bioaerosol concerns mean that composting facilities need to be at least 250 metres from UK homes and schools, but farms can be nearer and only require assessment if they are closer than 100 metres.