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Abstract
Fungal spores are ubiquitous in the environment. However, exposure levels in workplaces where mouldy materials are handled are much higher than in common indoor and outdoor environments. Spores of all tested species induced inflammation in experimental studies. The response to mycotoxin-producing and pathogenic species was much stronger. In animal studies, nonallergic responses dominated after a single dose. Allergic responses also occurred, especially to mycotoxin-producing and pathogenic species, and after repeated exposures. Inhalation of a single spore dose by subjects with sick building syndrome indicated no observed effect levels of 4 × 103 Trichoderma harzianum spores/m3 and 8 × 103 Penicillium chrysogenum spores/m3 for lung function, respiratory symptoms, and inflammatory cells in the blood. In asthmatic patients allergic to Penicillium sp. or Alternaria alternata, lowest observed effect levels (LOELs) for reduced airway conductance were 1 × 104 and 2 × 104 spores/m3, respectively. In epidemiological studies of highly exposed working populations lung function decline, respiratory symptoms and airway inflammation began to appear at exposure levels of 105 spores/m3. Thus, human challenge and epidemiological studies support fairly consistent LOELs of approximately 105 spores/m3 for diverse fungal species in nonsensitised populations. Mycotoxin-producing and pathogenic species have to be detected specifically, however, because of their higher toxicity.
Acknowledgements
This criteria document was prepared in cooperation with the Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals (NEG). NEG’s main task is to produce criteria documents to be used by the regulatory authorities as the scientific basis for setting occupational exposure limits for chemical substances. Whereas NEG adopts the document by consensus procedures, thereby granting the quality and conclusions, the author is responsible for the factual content of the document. The final version was accepted by NEG October 10, 2006. The following individuals participated in the elaboration of the document: Gunnar Johanson (Sweden, chairman), Maria Albin (Sweden), Karin Sørig Hougaard (Denmark), Kristina Kjærheim (Norway), Vidir Kristjansson (Iceland), Kai Savolainen (Finland), Vidar Skaug (Norway), Jill Järnberg (Sweden, secretary), Anna-Karin Alexandrie (Sweden, secretary). We gratefully acknowledge Aino Nevalainen for valuable comments on the draft document. Editorial work and technical editing were performed by the NEG secretariat. This work was financially supported by the Swedish National Institute for Working Life, the Norwegian Ministry of Labour and Social Inclusion, and the Nordic Council of Ministers.
All criteria document produced by the Nordic Expert Group can be down-loaded from www.nordicexpertgroup.org.
Declaration of interest: This paper was prepared during the normal course of the author’s employment as identified on the first page. The author has no other interests to declare.
| Abbreviations and acronyms | ||
| ACGIH | = | American Conference of Governmental Industrial Hygienists |
| AED | = | aerodynamic diameter |
| bw | = | body weight |
| CAMNEA | = | collection of airborne microorganisms on nucleopore filters, estimation and analysis |
| cfu | = | colony-forming units |
| CI | = | confidence interval |
| ECP | = | eosinophilic cationic protein |
| EU | = | endotoxin units |
| FEV1 | = | forced expiratory volume in 1 second |
| FVC | = | forced vital capacity |
| IFNγ | = | interferon gamma |
| IgE | = | immunoglobulin E |
| IgG | = | immunoglobulin G |
| IL | = | interleukin |
| LD50 | = | lethal dose for 50% of the animals at single exposure |
| LOEL | = | lowest observed effect level |
| MCP | = | monocyte chemoattractant protein |
| MEF25 | = | maximum expiratory flow at 25% of FVC |
| MIP | = | macrophage inflammatory protein |
| MVOC | = | microbial volatile organic compound |
| NEG | = | The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals |
| NO | = | nitric oxide |
| NOEL | = | no observed effect level |
| ODTS | = | organic dust toxic syndrome |
| OEL | = | occupational exposure limit |
| OR | = | odds ratio |
| PaO2 | = | arterial oxygen tension |
| PMN | = | polymorphonuclear leukocytes (mainly neutrophils) |
| PPR | = | prevalence proportion ratio |
| RAST | = | radio-allergosorbent test |
| ROS | = | reactive oxygen species |
| SEM | = | scanning electron microscope |
| sp/spp | = | species (singular/plural) |
| TGFβ | = | transforming growth factor beta |
| Th cells | = | T helper cells |
| TLco | = | lung transfer factor for carbon monoxide |
| TLR | = | Toll-like receptor |
| TLV | = | threshold limit value |
| TNFα | = | tumour necrosis factor alpha |
Data bases used in the search for literature
A literature search was conducted in the Medline, Toxline, Arbline, OSH-ROM, and ISI bases as well as the author’s own database. Further references were obtained from reviewed papers. The last search was performed in November 2006. The following terms were used in the literature search: