Bioaerosol exposure from composting facilities and health outcomes in workers and in the community: A systematic review update.

BACKGROUND: Rapid population growth and urbanisation around the world has led to increasing waste generation rates. Composting of organic waste in large-scale facilities is part of a growing trend in the UK, and elsewhere, to better manage and re-use the organic waste. However, composting inevitably generates bioaerosols, which have been associated with human health effects. In 2015, we reported that there was some, albeit limited, qualitative evidence linking bioaerosol emissions from composting facilities to poor respiratory health in nearby residents. However, the limited evidence precluded any quantitative assessment. Since then, the number of operational industrial-scale composting facilities in England has increased by 9% - nearly twice the growth from 2012 to 2014. At the same time, rapid urbanisation has led to expansion of city borders with more people living near large composting facilities and exposed to bioaerosol pollution. It is essential that regulatory authorities have access to the most up to date and accurate information.

OBJECTIVE: In this update of a systematic review published in 2015, we review and summarise the evidence from more recent studies that have assessed bioaerosol exposures within and near composting facilities and their associated health effects in both community and occupational health settings. Specifically, we wanted to find out if new evidence has emerged since the previous review to strengthen and confirm its conclusions.

MATERIAL AND METHODS: Two electronic databases (Medline and Embase) and bibliographies were searched for studies reporting on health outcomes and/or exposure to bioaerosols from composting facilities published between 1 January 2014 and 15 June 2018. Identification of relevant articles and data extraction was undertaken and studies were assessed for risk of bias.

RESULTS: 23 studies met the inclusion criteria (15 exposure studies, 4 health studies, 4 health and exposure studies (one of which used an exposure proxy)). The majority of studies were conducted in occupational settings, and over short time periods. Some progress has been made in the characterisation of bioaerosol emissions from these composting facilities, with the application of molecular-based methods. Whilst the latest health studies do not rely solely on subjective self-reported measures of health status but include more objective health measures, these studies were almost exclusively carried out in compost workers and were characterised by profound methodological limitations. Only one community health study was identified and used a proxy measure of bioaerosol exposure.

CONCLUSIONS: Although this review identified an additional 23 studies since the earlier review, the conclusions remain largely unchanged. Given the absence of any consistent evidence on the toxicity of bioaerosols from composting facilities, there is insufficient evidence to provide a quantitative comment on the risk to nearby residents from exposure to compost bioaerosols. To improve risk assessment and to best advise on risk management, it is important to ensure that the research recommendations outlined in this review are addressed.