Farmyard proximity benefit to respiratory health

Oct 30 2013

Data from the Netherlands indicate that living in close proximity to livestock farms is associated with decreased respiratory morbidity, including asthma, allergic rhinitis, and chronic obstructive pulmonary disease (COPD).

The research team, led by Lidwien Smit from the Institute for Risk Assessment Sciences in Utrecht, analyzed the medical records of 92,548 patients living in rural areas, including 22,406 children. Overall, more than half of all patients lived within 500 m of at least one animal farm, mainly of cattle and pigs.

Calculated exposure to particulate matter (PM10) emissions from nearby farms inversely correlated with the odds for asthma, allergic rhinitis, and COPD, which were observed in 2.5–3.0%, 2.0–2.5%, and 0.0–1.3% of patients, respectively.

And, the team found that the closer a patient lived to a farm the lower their odds for these respiratory conditions. For example, patients living between 50 m and 280 m from their nearest farm had a significant 34% lower odds for COPD and a 15% lower odds for allergic rhinitis than did patients living more than 640 m away.

There was also an association between respiratory morbidity and the number of nearby farms, with each additional farm within 500 m associated with a 2–6% reduced odds for the three conditions.

The only exception to these associations was the presence of mink farms within 500 m, which were associated with a 44% and 63% increased odds for asthma and allergic rhinitis, respectively.

“Results of the present analyses were somewhat unexpected, as the study was initiated by public health concerns related to intensive livestock farming,” comment Smit and colleagues.

They note that the results also conflict with previous findings among farmers. “It is not biologically plausible that farm-related exposures may protect against COPD,” they comment, suggesting that confounding may have played a role in their observations.

Writing in Occupational and Environmental Medicine, the researchers suggest that a protective effect of nearby farms against asthma and allergic rhinitis may be due to more diverse microbial exposures. However, they caution that this does not preclude the possibility that peak exposures may result in adverse respiratory events, including exacerbations among susceptible individuals.

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