Inflammation of the airways and microbiological exposure of composting plant workers: a longitudinal study

Outline of reasons and objectives
Composting is based on considerable proliferation of microorganisms, which can then be found in the air due to the handling operations necessary for the process to take place properly. Such microorganisms and the ones that are present initially in the waste, be they alive or dead, then take part in forming bioaerosols in the atmosphere of the workplace. Occupational exposure during composting work would appear to generate relatively non-specific acute disorders in which the mucous membranes of the eyes and of the upper airways are irritated. Currently, in France, there is no official rule for good composting practice and nor are there any mandatory collective or personal prevention measures that are specific to composting. A survey has been conducted to determine whether the working conditions are associated with the existence or the intensity of chronic inflammation of the airways of the workers (symptoms, and functional respiratory exploration). The working conditions correspond to types of plant defined on the basis of type of waste treated, of whether or not they are in the open air (or confined), and of whether the composting process uses forced aeration or is constituted merely by mixing the waste by turning it over.
Approach
A cross-cutting study of respiratory morbidity was repeated with, in all, 4 measurement times per subject, at intervals of about 6 months. The exposed group was made up of 90 employees working in the composting plants and who are exposed to waste and/or to compost. A group of 17 employees whose usual occupational activity does not involve exposure to bioaerosols, and who were comparable in terms of age and of socio-professional level, were also monitored.
Main results
Handling green waste is associated more with eye irritation, and handling shredded green waste is associated more with a higher level of lower airway inflammation marker. Doing cleaning tasks on foot at the plant is associated with greater bronchial reactivity, without going as far as bronchial hyperreactivity, which is present in cases of asthma, in particular. Use of vehicles that are less well equipped with air-conditioning is associated with more symptoms of irritation of the nose. Washing work clothes at home rather than them being cleaned by the company is associated with more symptoms of irritation of the lower airways.
Discussion
The study has highlighted the effect of absence of air-conditioning in the cabs of site vehicles, and the effect of absence of company cleaning of work clothes on symptoms of irritation of the airways. Equipping cabs with air-conditioning and having work clothes cleaned by the company could contribute to preventing risks for respiratory health. Translation, in terms of respiratory health, of the small effects observed on the pre-clinical markers remains to be clarified.