Occupational exposure to fungi on recyclable paper pots and growing media and associated health effects – A review of the literature

Highlights: • Peziza ostracoderma is found on many different growing and casing media. • Other fungal species are also found on/in growing and casing media. • Hypersensitivity pneumonitis is caused by fungi from growing and casing media. • The air and hands are important routes of exposure to consider. • Limited knowledge on occupational health associated with growing and casing media. Different types of pots and growing and casing media, including biodegradable materials, are used for plant and mushroom production. The fungus Peziza ostracoderma has gained attention for its visible growth on growing media for plants and casing media for mushrooms. Through a review of the literature we aim to evaluate whether exposure to fungi from recyclable pots and different growing and casing media occurs and causes occupational health effects. Based on the published papers, specific fungal species were not related to a specific medium. Thus P. ostracoderma has been found on paper pots, peat, sterilized soil, vermiculite, and rockwool with plants, and on peat, pumice, and paper casing for mushrooms. It has been found in high concentrations in the air in mushroom farms. Also Acremonium spp., Aspergillus niger, A. fumigatus, Athelia turficola, Aureobasidium pullulans, Chaetomium globosum, Chrysonilia sitophila, Cladosporium spp., Cryptostroma corticale, Lecanicillium aphanocladii, Sporothrix schenckii, Stachybotrys chartarum, and Trichoderma spp. have been found on different types of growing or casing media. Most of the fungi have also been found in the air in greenhouses, but the knowledge about airborne fungal species in mushroom farms is very limited. Eight publications describe cases of health effects associated directly with exposure to fungi from pots or growing or casing media. These include cases of hypersensitivity pneumonitis caused by exposure to: A. fumigatus, A. niger, Au. pullulans, Cr. corticale, P. ostracoderma, and a mixture of fungi growing on different media. Different approaches have been used to avoid growth of saprophytes including: chemical fungicides, the formulation of biodegradable pots and growing media and types of peat. To increase the sustainability of growing media different types of media are tested for their use and with the present study we highlight the importance of also considering the occupational health of the growers who may be exposed to fungi from the media and pots.