L’insorgenza delle malattie professionali negli operatori addetti alla coltivazione e manipolazione dei funghi: una revisione
10.6092/issn.2531-7342/9409
La produzione intensiva di funghi commestibili e medicinali è un'attività agricola comune in tutto il mondo e coinvolge un gran numero di operatori la cui salute deve essere salvaguardata poiché potrebbero esserci dei rischi. Le tecniche di crescita e le condizioni ambientali richieste per la produzione e la lavorazione dei funghi espongono i lavoratori a diversi tipi di allergeni che causano l'insorgenza di una serie di condizioni classificabili come malattie professionali. Vale a dire, i lavoratori di funghi soffrono di malattie polmonari allergiche e, più raramente, di forme di dermatite da contatto. La causa di queste manifestazioni cliniche si può riscontrare nell'esposizione a diversi fattori, come le particolari condizioni di produzione che portano allo sviluppo di molti allergeni (batteri, muffe, micotossine, endotossine) e il contatto diretto con alcune specie fungine, che sono esse stesse allergeni.
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The onset of occupational diseases in mushroom cultivation and handling operators: a review
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Ital J Mycol
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Yoshikawa S, Tsushima K, Yasuo M, Fujimoto K, Kubo K, Kumagai T, Yamazaki Y (2007) Hypersensitivity pneumonitis caused by Penicillium citrinum, not Enoki spores. American Journal of Industrial Medicine 50:1010-1017.
The onset of occupational diseases in mushroom cultivation and handling operators: a review
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Ficociello et al.                                                            Italian Journal of Mycology 48: 26-38 (2019)

DOI: https://doi.org/10.6092/issn.2531-7342/9409

Review

    The onset of occupational diseases in mushroom cultivation
                 and handling operators: a review
    Barbara Ficociello1, Eva Masciarelli1, Laura Casorri1, Angelo Cichelli2, Giovanni Pacioni3
1
 Department of Technological Innovations and safety of plants, products and anthropic settlements (DIT), National
Institute for Insurance against Accidents at Work, via Ferruzzi 38/40, 00143 Rome, Italy
2
 Department of Medical, Oral and Biotechnological Sciences – DiSMOB, "G. D'Annunzio" University of Chieti-Pescara,
via dei Vestini, Campus Univ. Chieti, Italy
3
 Department of Life, Health and Environmental Sciences - MeSVA, University of L’Aquila, Piazzale Salvatore Tommasi
1, 67100 Coppito, L’Aquila, Italy

Corresponding author e-mail: l.casorri@inail.it
Received 25/02/2019; accepted 18/04/2019.


Abstract
The paper presents a review on health hazards involving operators that cultivate and handle mushrooms. Intensive
production of edible and medicinal fungi is a common agricultural management all over the world and involves a number
of operators whose health must be safeguarded due the number of risks. Growth techniques and environmental conditions
for producing and handling mushrooms expose workers to several types of allergens that possibly cause occupational
diseases. Namely, mushroom workers suffer from allergic pulmonary diseases and, more rarely, from forms of contact
dermatitis. The cause of these clinical manifestations may be found in the exposure to several factors, such as the peculiar
production conditions leading to the presence of many allergens (bacteria, moulds, mycotoxins, endotoxins) and the direct
contact of workers with some fungal species, which are themselves allergens.

Key words: Antigens; bacteria; mycotoxins; hypersensitivity pneumonitis; contact dermatitis.




Introduction

Fungi are microorganisms that sometimes form reproductive structures (sporomata) big enough to be
handpicked. These structures are commonly called “mushrooms” or improperly “fruiting bodies” and
produce meiotic spores. Only edible fungi are picked up and sold for food use. For several centuries
many saprotrophic fungi have been cultivated in Europe and Asia (Chang and Miles, 2004), since
they can grow indoor on properly treated organic material (compost).
      Besides saprotrophic fungi, like champignon [Agaricus bisporus (J.E. Lange) Imbach],
pleurotus [Pleurotus (Fr.) P. Kumm.], velvet pioppini [Cyclocybe aegerita (V. Brig) Vizzini], the
market offers highly prized fungi that can only grow in nature, being symbionts of tree root systems,
like porcini (Boletus edulis Bull.), Caesar’s mushrooms [Amanita caesarea (Scop.) Persoon],
chanterelle (Cantharellus cibarius Fr.) and various species of truffles (Tuber spp.), which are
processed and transformed. World production of edible and medicinal mushrooms reaches a total of
approximately 10 million tons per year. Italy is among the top-ranking countries with a percentage
slightly below 7%, equal to approximately 680,000 tons (Food and Agriculture Organization of the
United Nations, 2016).
      The intensive production involves a number of workers and great attention must be paid to their
health. The process of fungal growth and environmental conditions needed for sporoma development
expose operators to various types of allergens, possibly leading to diseases classifiable as
‘occupational diseases’. Compost, which represents the food source for some mushrooms, is the first
source of exposure risk. Compost consists of variable percentages of various decaying organic
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Ficociello et al.                                                       Italian Journal of Mycology 48: 26-38 (2019)




materials (wheat straw and hay, oat, rice bran, virgin olive pomace, bird or horse manure, etc.),
sometimes mixed with inorganic matter (chalk, limestone gravel, agriperlite, etc.). Other cultivated
fungal species only require grinded plant materials, usually sterilised, or logs.
      The quantity of allergens dispersed in the working environment may vary according to
cultivation methods. Some species of edible mushrooms, such as Shiitake [Lentinula edodes (Berk.)
Pegler], are cultivated on a substratum of a mixture of wet wood sawdust, wheat straw, and protein
flour promoting the development of specific moulds (Penicillium spp. and Trichoderma spp.) that are
considered powerful immunogens (Gaitán-Hernández et al., 2014). All the stages of the process are
a source of environmental contamination due to several microbes (bacteria, moulds) and their
metabolites (toxins) that may be dangerous for the health of susceptible individuals. In some cases,
workers are exposed to allergens through the manipulation of fruiting bodies, hyphae and spores
(Koivikko and Savolainen, 1988). Moreover, mushrooms are kept in peculiar climate conditions (high
temperature and relative humidity) favouring microbial bioaerosol contamination, which is
considered the main cause of the inflammatory reactions of workers (O’Gorman and Fuller, 2008).
      Bioaerosols found in greenhouses or indoors where edible fungi are grown include particular
microbial species (Table 1). This demonstrates the widely diversified presence of allergens in the air,
with a concentration that can be higher than 109 colony-forming units (CFU)/m3 of air (Chun et al.,
2012).

           Table 1 - Microorganisms and toxins found in bioaerosols of fungal cultivations in indoor
           environments
            Gram-negative bacteria Pseudomonas spp., Acinetobacter spp., Pedobacter, Herbaspirillum,
                                   Flavobacterium, Chryseobacterium, Enterobatteriaceae
             Gram-positive bacteria   Bacillus spp., Staphylococcus spp., Enterococcus spp., Arthrobacter,
                                      Microbacterium, Rhodococcus, Actinomyces spp., Streptomyces spp.
             Fungi                    Penicillium spp., Cladosporium spp., Aspergillus spp., Trichoderma
                                      spp., Alternaria spp., Rhizopus spp., Epicoccum spp., Fusarium spp.,
                                      Geotricum spp., Botrytis spp., Mucor spp.
             Endotoxins               Molecules originated from gram-negative bacteria
             Mycotoxins               Aflatoxins, fumonisins, ochratoxins


      The most common clinical manifestations are lung-related diseases, like more or less serious
forms of sensitisation, fibrosis or chronic obstructive pulmonary diseases and interstitial pulmonary
diseases (Dudley et al., 2014). Workers have been found to suffer from a form of hypersensitivity
pneumonitis caused by an immune reaction of the organism to the inhalation of fungal antigens.
(Cano-Jiménez et al., 2016). Some antigens can induce hypersensitivity reactions of type I
(immediate: allergies, asthma, eczema), type III (immunocomplex-mediated: serum sicknesses such
as vasculitis, nephritis and arthritis), and type IV (delayed: contact hypersensitivity and dermatitis)
(Torricelli et al., 1997; Curnow and Tam, 2003).

Pneumonitis and hypersensitivity in mushroom workers

Over 300 antigens have been found that may induce severe or chronic forms of pulmonary diseases
(bronchial asthma, alveolitis, fibrosis) deriving from farming-related agents (exposure to ticks, mites,
arthropods, antigens of animal origin, above all birds, flours, moulds, fungi, plants, pollens)
(European Respiratory Society, 2018). Some of these affections have a short latent period between
exposure and clinical manifestation. Others have a longer latent period and a correlation between
cumulative exposure and symptomatology (European Respiratory Society, 2018).
      Not only exposure time but also exposure dose plays a role in the onset of the diseases. In fact,
high levels of organic dusts for a long exposure time may cause pneumoconiosis or chronic
obstructive pulmonary diseases (Barreiro et al., 2016). However, low exposure levels that comply
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with law limits may also cause some allergic forms in workers (Basketter et al., 2015). It has been
observed that agricultural workers may suffer from allergic alveolitis, with possible evolution to
hypersensitivity pneumonitis, due to continuous exposure to specific organic antigens (thermophilic
actinomycetes and fungal spores) (Table 2) (Lacey and Dutkiewicz, 1994; Hayes and Rooney, 2014;
Liu et al., 2015).

Table 2 - Correlation between diseases and exposure to specific organic antigens in agri-food workers (updated from
Mahmoudi, 2016)
 Antigen                         Source                                                    Disease
 Thermophilic actinomycetes†     Vegetable compounds (mouldy hay, ensiled wheat)          Farmer’s lung
 Fusarium spp.                   Dry leaves and grass
 Penicillium brevicompactum      Manure
 Saccharomonospora viridis       Mouldy fodder
 Absidia cerymbifera
 Wallemia sebi

 Thermophilic actinomycetes†     Fungal compost                                         Mushroom farmer’s lung
 Monocillium spp.                Indoor mushroom cultivation
 Pleurotus ostreatus*            Peat
 Hypsizygus marmoreus*           Mushrooms
 Lycoperdon perlatum*

 Botrytis cinerea                Mouldy grapes                                          Winemaker’s lung

 Penicillium expansum            Mouldy wood                                            Woodworker’s lung
 Penicillium cyclopium           Wood dust
 Penicillium chrysogenum
 Cephalosporium acremonium
 Alternaria spp.
 Bacillus subtilis

 Aspergillus spp.                Mouldy barley                                          Maltworker’s lung
 Aspergillus clavatus

 Candida spp.                    Mouldy sugarcanes                                      Sugarcane worker’s lung
 Ulocladium botrytis
 Thermoactinomyces vulgaris

 Aspergillus spp.                Greenhouse soil                                        Greenhouse      worker’s
 Penicillium spp.                                                                       lung

  Penicillium casei              Cheese moulds                                    Cheese worker’s lung
  Penicillium roqueforti         Salami moulds                                    Sausage worker’s lung
  Penicillium cyclopium
  Penicillium chrysogenum
  Penicillium camemberti
  Acarus siro
†
 Saccharopolyspora rectivirgula/Micropolyspora faeni, Thermoactinomyces vulgaris, Thermoactinomyces viridis,
Thermoactinomyces candidus, Thermoactinomyces sacchari
*
 Basidiospores

      Van den Bogart et al. (1993) compared the species of microorganisms identified in the
bioaerosol of compost fermentation tunnels with the antibodies found in the serum of workers
suffering from hypersensitivity pneumonitis. The identified immunocomplexes were exclusively
directed towards actinomycetes (Excellospora flexuosa, Thermomonospora alba, T. curvata, T.
fusca) and not towards fungal species [Aspergillus fumigatus Fresen., Penicillium brevicompactum
Dierckx, P. chrysogenum Thom, Scytalidium hyalinum C.K. Campb. & J.L. Mulder, S. thermophilum
(Cooney & R. Emers.) Austwick and Trichoderma viride Pers.]. Also, the study demonstrated a
positive correlation between the antibody titer, and the occupational seniority, particularly towards
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Ficociello et al.                                               Italian Journal of Mycology 48: 26-38 (2019)




actinomycetes, confirming the hypothesis that these microorganisms are the main causal agents of
hypersensitivity pneumonitis (Pereira et al., 2016). It is an inflammatory syndrome of the lower
respiratory tract resulting from inhalation of organic dusts containing antigens (bacteria spores, fungi,
animal proteins or bacterial products) and represents the most common disorder suffered by workers
employed in mushroom cultivation (Sakula, 1967). It was first identified in the United States in 1959,
in some workers exposed to compost used for mushroom cultivation, but the agent or substance that
induced it was still unknown (Bringhurst et al., 1959).
      Studies conducted on other agricultural workers suffering from lung disorders similar to
hypersensitivity pneumonitis showed that etiologic agents were antigens derived from bacteria of the
genus Actinomyces (particularly Micropolyspora faeni and more rarely Thermoactinomyces
vulgaris), that had developed in decomposing hay (Pepys et al., 1963; Pepys and Jenkinsp, 1965).
Sakula (1967) was the first to coin the specific term “mushroom worker’s lung” to identify
hypersensitivity pneumonitis. The author classified it as occupational disease after finding
immunocomplexes directed towards actinomycete antigens in the serum of mushroom workers.
      Hypersensitivity pneumonitis is a disorder resulting from an immunopathogenic IgG-mediated
inflammatory reaction cell-mediated by T-lymphocytes. It is characterized by a high antibody titer
towards the antigens causing alveolitis in the presence of normal IgE and eosinophil values. The
process is induced by a repeated exposure to antigens, present in the breathable fraction of organic
dust (particles with a dimeter below 5 µm, PM5) that reach bronchioles and alveoli, where they
combine with antibodies to form immunocomplexes. The antigens more frequently responsible for
the formation of immunocomplexes derive from fungi of the genus Aspergillus (e.g. A. fumigatus),
from thermophilic actinomycetes (e.g. T. vulgaris, Saccharopolyspora rectivirgula, M. faeni, etc.)
and from the basidiospores of some species of edible mushrooms (Kleyn et al., 1981; Shen et al.,
1991; Van den Bogart et al., 1993; Xu et al., 2002). On the other hand, immunocomplexes activate
macrophages to produce molecules mediating an acute inflammatory reaction (Suga et al., 1997;
Nance et al., 2005).
      Severe hypersensitivity pneumonitis is the most common form of this disease. It appears after
hours or days from the exposure to the antigen with fever, cough, dyspnoea, asthenia and discomfort
and is characterized by fibrosis and angiogenesis (Bertorelli et al., 2000). The symptoms may persist
for about a week after removing the causal agent.
      Repeated exposure in time to antigens causes a positive feedback cycle for T-lymphocytes,
constantly activated to produce pro-inflammatory molecules, creating a chronic inflammation
condition that, in the sub-severe form, leads to the formation of a granuloma. The clinical evolution
is devious, with productive cough, exertional dyspnoea and asthenia (Yamane and Paul, 2012). A
severe or sub-severe form or, more rarely, a chronic form of the disease may occur according to
intensity and frequency of exposure and to the different immunological response determined by
individual susceptibility (Riario Sforza and Marinou, 2017). The chronic form is less than 5% of
cases, in which a persistent inflammatory condition is caused by repeated acute or subacute episodes,
due to prolonged inhalation of low doses of antigens, and causes an irreversible lung damage. This
form is more devious than the sub-severe one and may stay silent for long, with recurring episodes
of dyspnoea and low-grade fever until the appearance of serious dyspnoea and full-blown respiratory
failure (Bourke et al., 2001; Patel et al., 2001).

Hypersensitivity pneumonitis: a multifactorial disease?

Histamine
The connection between the presence of specific antibodies to actinomycetes and moulds and
hypersensitivity pneumonitis is now widely ascertained. It has also been supposed that the
inflammatory state at the origin of the disorder may be multifactorial, including the production of
histamine or endotoxins of fungal or bacterial origin (Smuda and Bryce, 2011). For example, T. viride
conidia, even in very low concentrations (0.1 ng ml-1), increases the release of IgE-mediated

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Ficociello et al.                                               Italian Journal of Mycology 48: 26-38 (2019)




histamine by mastocytes in the mucosae of the respiratory tract, suggesting a role of this mediator as
co-factor of the pathological implications of pneumonitis (Larsen et al., 1996; Enríquez-Matas et al.,
2009). These results were also found on workers involved in activities not related to the production
of edible mushrooms (cork, cheese, salami processing) (Campbell et al., 1983; Cormier et al., 1998;
Guglielminetti et al., 2001; Winck et al., 2004; Merget et al., 2008; Marvisi et al., 2012). This shows
that exposure to some allergens (A. fumigatus, M. faeni and T. vulgaris), in different contexts, induces
hypersensitivity pneumonitis according to the same mechanisms (Che et al., 1989; Hinojosa et al.,
1996).
      Aspergillus fumigatus, like other mold species, through a high content of beta-glucans found in
cell walls, acts directly on macrophages and neutrophils inducing the production of pro-inflammatory
molecules and an IgE-mediated type I reaction (immediate hypersensitivity) (Hohl et al., 2005;
Geoffrey et al., 2006; Yoshikawa et al., 2007; Wang et al., 2016).

Gram-negative bacteria
Hypersensitivity pneumonitis may also due to gram-negative bacteria, which abound in fermented
plant products and animal faeces (materials present in compost) and produce a lipopolysaccharide
endotoxin (Lange et al., 2003; Henrik and Wolff, 2011). In vitro experiments have demonstrated that
a high concentration of this lipopolysaccharide can induce the production of the same pro-
inflammatory molecules (IL1, IL6, IL8 and TNF-alfa) found in severe hypersensitivity pneumonitis
in the macrophages of alveoli and lung epithelium cells (Dutkiewicz, 1978; Olenchock et al., 1983;
Jagielo et al., 1996a,b; Allermann and Poulsen, 2000, 2002; Thorn, 2001; Smit et al., 2006).
       Recently, a lipopolysaccharide endotoxin from Pantoea agglomerans has been identified as a
possible emerging occupational pathogen agent. Pantoea agglomerans, known above all for
opportunistic infections in immunocompromised individuals, is also considered responsible of
occupational diseases associated with exposure to wheat dust and other organic dusts of agricultural
origin (Al-Amluji et al., 1982; Naha et al., 2012; Dutkiewicz et al., 2015). The bacterium can reach a
relatively high concentration in bioaerosol where plant materials and their by-products are processed.
The immunogenic component of P. agglomerans lipopolysaccharide (10-50 nm globular
nanoparticles) allows the molecule to be inhaled and transferred to the lower respiratory tract.
Experiments conducted in vivo with various strains of P. agglomerans isolated from cereal dust and
their endotoxin have shown that these extracts can cause inflammatory processes and pulmonary
fibrosis (Dutkiewicz et al., 2015; Dutkiewicz et al., 2016). The in vivo results in agreement with
clinical studies show that agricultural workers exhibit a high immunological reactivity to wheat and
Pantoea allergenic extracts and a higher incidence of allergic alveolitis and asthma (Lantz et al., 1985;
Milanowski, 1994).
       The lipolysaccharide endotoxin of P. agglomerans is not the only one to induce hypersensitivity
pneumonitis. Other gram-negative bacteria, like Escherichia coli, may be involved too, confirming
the hypothesis that the cause of clinical manifestations (cough, breast pang, dyspnoea, decreased
respiratory function) identified in exposed individuals is the concentration of endotoxin in the air and
not of dust particulate (Ryan et al., 1994; Jagielo et al., 1996a; Von Essen, 1997; Burch et al., 2010).
A study performed in mushroom greenhouses (Simpson et al., 1999) measured a concentration of
endotoxins units (EU) in bioaerosol ranging from a minimum of 10 EU/m3 to a maximum of 1300
EU/m3. Concentrations above 100 EU/m3 may lead to respiratory tract inflammations and those above
1,000 EU/m3 cause acute effects with respiratory symptoms defined as organic dust toxic syndrome
(Simpson et al., 1999).

Spores
Spores of edible mushrooms may be allergens too; spores of some cultivated fungi [Hypsizygus
marmoreus (Peck) H.E. Bigelow, L. edodes, Pholiota nameko (T. Itô) S. Ito & S. Ima, Lyophyllum
aggregatum (Schaeff.) Kühner and Pleurotus eryngii (DC.) Quél.] consumed in Japan have caused
hypersensitivity pneumonitis in production workers (Nakazawa and Tochigi, 1989; Tsushima et al.,
                                                                                                          30
Ficociello et al.                                               Italian Journal of Mycology 48: 26-38 (2019)




2001; Saikai et al., 2002). The causes can be found in the exposure to small spores (4-6 μm in
diameter) of these Basidiomycetes, which reach alveoli easily, and in the high concentration of spores
in greenhouses during harvesting and packaging.
       Lentinula edodes can cause hypersensitivity pneumonitis because the IgG produced against the
antigens present in its spores have been found in cultivator serum (Sastre et al., 1990; Matsui et al.,
1992; Murakami et al., 1997; Senti et al., 2000; Suzuki et al., 2001; Ampere et al., 2012). Lentinula
edodes can produce a great quantity of spores: their indoor concentration can reach 40 million/m3 of
air (van Loon et al., 1992). Investigations have also highlighted a diversification in the quantity of
airborne spores among fungal species (Madsen et al., 2009). Shiitake and Pleurotus mushrooms
release large quantities of spores in the atmosphere determining high concentrations in indoor
cultivations (Sastre et al., 1990; Matsui et al., 1992; Senti et al., 2000).
       After champignon (A. bisporus), Shiitake is the second most cultivated and eaten fungus in the
world. It is important to stress that in recent years this mushroom has become quite common in
western markets as well. If large-scale cultivation of these fungi will spread in Europe, specific
measures of health protection will have to be adopted in order to safeguard the mushroom workers
against hypersensitivity pneumonitis. Likewise, Pleurotus ostreatus (Jacq.) P. Kumm. spores are
considered allergens involved in the etiogenesis of hypersensitivity pneumonitis. Since the gills of
this fungus, are not veiled like in Agaricus spp. or Lentinula spp., a great number of spores is spread.
A study conducted by Sonnenberg et al. (1996) demonstrated that, according to the development stage
of the fruiting body, the species Pleurotus can release up to a billion spores per day per gram of
fungus (Olsen, 1987).

Allergic dermatitis

Another health risk that has been investigated over the years regards dermatologic affections induced
by edible mushrooms. Such manifestations are rarer than hypersensitivity pneumonitis. However,
case studies have been reported for individuals exposed to mushrooms for professional reasons
(picking up, packaging, selling, processing). The fungal species most responsible for this disease are
champignons (A. bisporus) and porcini (B. edulis). To date, the origin of contact dermatitis has not
been ascertained, but this disorder has been put in connection with hypersensitivity reactions of type
I, III and IV or with forms of hypereosinophilia (Korstanje et al., 1990; Kanerva et al., 1998; Simeoni
et al., 2004; Baruffini et al., 2005).
        Shiitake may cause an IgE-mediated allergic form that may manifest as contact urticaria, protein
contact dermatitis (PCD) or both. Cutaneous symptoms are different from those of ‘Shiitake
dermatitis’ (toxicodermia), which is a non-allergic dermatitis caused by the consumption of raw
Shiitake. In fact, the patch test (allergy test to determine if a substance causes allergic inflammation
of the skin with cell-mediated mechanism) against Shiitake allergens is positive in patients with
allergic contact dermatitis (Tarvainen et al., 1991; Nakamura, 1992; Ueda et al., 1992; Hanada, 1998;
Aalto-Korte et al., 2005). Shiitake hyphae are moderately allergenic, as demonstrated by the Guinea
pig maximization test for hypersensitivity type IV (Ueda et al., 1992). Aalto-Korte et al. (2005) have
been the first to associate Shiitake as aetiological agent of an eczematous eruption on the hands of
two growers. The prick test (skin allergy test for the diagnosis of respiratory and food allergies)
showed that both patients had reactions to shiitake and that there were specific IgEs against this
fungus in their serums. The patients had an IgE-mediated allergy to shiitake with consequent
diagnosis of occupational protein contact dermatitis. Some cases of allergic contact dermatitis caused
by this fungus, also correlated to symptoms of asthma (Curnow and Tam, 2003), hypersensitivity
pneumonitis and contact urticaria have been reported in literature (Tarvainen et al., 1991; Ueda et al.,
1992). Some mushroom workers develop eczematous contact eruption and immediate allergy.
        White Pom Pom mushroom [Hericium erinaceum (Bull.) Pers.], also known as ‘monkey head
mushroom’ or ‘lion’s mane mushroom’, is a very valuable edible fungus used in medicine. This
fungus may cause allergic contact dermatitis too (Maes et al., 1999).

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Ficociello et al.                                                        Italian Journal of Mycology 48: 26-38 (2019)




Mycotoxins and pulmonary pathology

Another possible cause of diseases in those who work in this sector is exposure to mycotoxins
produced by moulds present in their working environment. It is necessary to stress that they are a risk
factor that is not completely known and, maybe, underestimated. Although mycotoxins are not much
volatile and human exposure to them is linked to the ingestion of contaminated food, there might be
a potential route of exposure to mycotoxin by inhalation, conveyed in alveoli by spores or
contaminated substrata (Emanuel et al., 1975; Sorenson, 1981; Dvorackova and Pichova, 1986).
Cases of pulmonary mycotoxicosis have been described in agricultural and textile workers. Although
the symptoms are similar to those of a disease induced by an allergic reaction, it was not possible to
determine the cause for the lack of granulomas in the lungs and circulating antibodies against fungal
antigens. Lougheed et al. (1995) have maybe been the first to associate pulmonary disease cases to
the presence of aflatoxin B1 by exposure to a working environment contaminated by Fusarium spp.

Conclusions

Although there is an evident correlation between occupational exposure to biological agents
(microorganisms, mycotoxins, allergens, mites, endotoxins) and effects on workers’ health, an
occupational exposure limit for biological risk has not been established yet. Even though values have
been suggested by several institutes, like the DECOS (Dutch Expert Committee on Occupational
Health Standard), which recommended for endotoxins an exposure limit of 90 units (EU)/m3 of air
sampled in 8 working hours.
      Two standards have been drawn up for evaluating occupational exposure to biological agents:
the EN 13098 (European Committee for Standardisation: UNI EN 13098, 2002), defining the rules
for measuring airborne microorganisms, and the EN 14031 (European Committee for
Standardisation: UNI EN 14031, 2003), totally dedicated to measuring airborne endotoxins. If limit
values for microorganisms, endotoxins or mycotoxins are established, it is not possible to separate an
evaluation of biological risk from the microorganism/host relationship. This does not mean that
complying with law limits may guarantee a complete safeguard of workers, because it is important to
take into account individual susceptibility determined by biological characteristics (lifestyle, genetics,
age, sex) of the individual exposed. Mushroom cultivation is a peculiar example of exposure to
bioareosol, because workers risk contracting diseases at all stages of production chain. Therefore, it
is important and necessary to train and inform workers as regards the biological risk they are exposed
to and the correct implementation of prevention and protection measures to avoid adverse health
effects. So, the main goal is to adopt collective prevention measures through an adequate air filtration
system in order to have an indoor bioaerosol with a very low allergen concentration. Gloves and dust
masks may offer a valid personal protective equipment, particularly for susceptible persons or in
contexts where it is not possible to install an air filtering system. In the case of individuals suffering
from clinical manifestations, the competent doctor must ensure that they remain away from the
allergen source (Pozzi et al., 1998).

Acknowledgments
We express our gratitude to the two anonymous reviewers who have greatly improved the quality of this paper with their
comments.


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