Summary
The authors found 38 studies that investigated the connection between intensive farming, as defined by the European Union (EU), and bioaerosols (airborne biological material which often contains microorganisms, like bacteria and fungi). This review includes findings about occupational and community exposure. 21 studies investigated occupational exposure and 18 focused on pig farms. For occupational exposure, all studies reported at least one adverse health effect. Specific results are reviewed for lung function and respiratory symptoms, asthma, and chronic bronchitis. For community samples, one of the most consistent findings was higher prevalence of self-reported asthma for children in close proximity (at home or at school) to an intensive farm. A strength of this review is its broad inclusion of different studies and its strong assessment of confounding factors. However, many included studies relied on self-reports, which makes interpretation more uncertain. The authors acknowledge that the hazards might be underestimated due to the “healthy worker effect”. It describes how workers who experience severe health issues are likely to change the workplace and are therefore underrepresented in studies. Overall, this review highlights that more quantitative research on a broad range of health issues is needed. The potential health hazard of bioaerosols should be closely monitored to gain more information and a more conclusive picture.
Background: Population growth, increasing food demands, and economic efficiency have been major driving
forces behind farming intensification over recent decades. However, biological emissions (bioaerosols) from
intensified livestock farming may have the potential to impact human health. Bioaerosols from intensive livestock farming have been reported to cause symptoms and/or illnesses in occupational-settings and there is
concern about the potential health effects on people who live near the intensive farms. As well as adverse health
effects, some potential beneficial effects have been attributed to farm exposures in early life. The aim of the study
was to undertake a systematic review to evaluate potential for adverse health outcomes in populations living
near intensive livestock farms.
Material and methods: Two electronic databases (PubMed and Scopus) and bibliographies were searched for
studies reporting associations between health outcomes and bioaerosol emissions related to intensive farming
published between January 1960 and April 2017, including both occupational and community studies. Two
authors independently assessed studies for inclusion and extracted data. Risk of bias was assessed using a customized score.
Results: 38 health studies met the inclusion criteria (21 occupational and 1 community study measured
bioaerosol concentrations, 16 community studies using a proxy measure for exposure). The majority of occupational studies found a negative impact on respiratory health outcomes and increases in inflammatory biomarkers among farm workers exposed to bioaerosols. Studies investigating the health of communities living near
intensive farms had mixed findings. All four studies of asthma in children found increased reported asthma
prevalence among children living or attending schools near an intensive farm. Papers principally investigated
respiratory and immune system outcomes.
Conclusions: The review indicated a potential impact of intensive farming on childhood respiratory health, based
on a small number of studies using self-reported outcomes, but supported by findings from occupational studies.
Further research is needed to measure and monitor exposure in community settings and relate this to objectively
measured health outcomes.