Emissions from livestock farms cause asthma（哮喘） and COPD patients living nearby to experience more exacerbations（发作，恶化） , according to research presented at the European Respiratory Society's Annual Congress in Amsterdam. Also, chances of contracting Q fever from nearby sheep and goat farms increased with the number of animals rather than with the number of farms, the research found, hinting at higher health risks from 'mega farms'.

The researchers, from Utrecht University, measured increased levels of particulate（微粒） matter containing microbes and microbial toxins near livestock farms. They studied health effects by screening medical records from 50 general practitioners servicing 200,000 patients in regions with high and low densities of livestock farms.

In regions with many livestock farms, doctors reported less asthma, COPD, upper respiratory tract（呼吸道） infections and hay fever, a result that mimics some earlier studies that saw less allergies in children who grown up on farms. In this study, the medical records did not specify whether symptoms were allergy- related, so the researchers do not know whether the effect is indeed limited to allergies.

The research however also showed that in areas with many livestock farms, people who suffer from asthma or COPD developed twice as much pneumonia and upper respiratory tract infections than people in regions with little livestock activity. The overall prevalence of pneumonia also was higher in high-density areas.

The study period included an unusually severe outbreak of Q fever, an infectious disease of cattle, sheep or goats, which can cause flu-like symptoms and pneumonia in humans. Between 2007 and 2010, close to 4,000 people in the Netherlands became ill; at least ten of them died.

The researchers found that the risk of contracting Q fever increased with the proximity of sheep farms or goat farms. An even stronger correlation was found between Q fever risk and the number of animals kept in the area, suggesting that mega farms could bring more environmental health risks than smaller farms.

The study contributes to on-going debates about intensive animal farming in densely populated regions in countries such as Germany and the Netherlands.

Lead researcher Dr Lidwien Smit said: "Our study is one of the first to show that living close to farms leads to exacerbation of symptoms for people with lung conditions and that during a Q fever outbreak, the risk of contracting Q fever increased with the number of livestock animals kept close by."