Exposure and risk assessment in occupational exposure to fungi: aspects to consider in highly contaminated settings

Although a clear correlation between levels of fungi in the air and health impacts has not been shown in epidemiological studies, fungi must be regarded as potential occupational health hazards. Fungi can have an impact on human health in four different ways: (1) they can infect humans, (2) they may act as allergens, (3) they can be toxigenic, or (4) they may cause inflammatory reactions. Fungi of concern in occupational hygiene are mostly non-pathogenic or facultative pathogenic (opportunistic) species, but are relevant as allergens and mycotoxins producers. It is known that the exclusive use of conventional methods for fungal quantification (fungal culture) may underestimate the results due to different reasons. The incubation temperature chosen will not be the most suitable for every fungal species, resulting in the inhibition of some species and the favouring of others. Differences in fungi growth rates may also result in data underestimation, since the fungal species with higher growth rates may inhibit others species’ growth. Finally, underestimated data can result from non-viable fungal particles that may have been collected or fungal species that do not grow in the culture media used, although these species may have clinical relevance in the context. Due to these constraints occupational exposure assessment, in setings with high fungal contamination levels, should follow these steps: Apply conventional methods to obtain fungal load information (air and surfaces) regarding the most critical scenario previously selected; Guideline comparation aplying or legal requirements or suggested limits by scientific and/or technical organizations. We should also compare our results with others from the same setting (if there is any); Select the most suitable indicators for each setting and apply conventional-culture methods and also molecular tools. These methodology will ensure a more real characterization of fungal burden in each setting and, consequently, permits to identify further measures regarding assessment of fungal metabolites, and also a more adequate workers health surveillance. The methodology applied to characterize fungal burden in several occupational environments, focused in Aspergillus spp. prevalence, will be present and discussed.

Fungi spores dimension matters in health effects: a methodology for more detail fungi exposure assessment

Health effects resulting from dust inhalation in occupational environments may be more strongly associated with specific microbial components, such as fungi, than to the particles. The aim of the present study is to characterize the occupational exposure to the fungal burden in four different occupational settings (two feed industries, one poultry and one waste sorting industry), presenting results from two air sampling methods – the impinger collector and the use of filters. In addition, the equipment used for the filter sampling method allowed a more accurate characterization regarding the dimension of the collected fungal particles (less than 2.5 μm size). Air samples of 300L were collected using the impinger Coriolis μ air sampler. Simultaneously, the aerosol monitor (DustTrak II model 8532, TSI®) allowed assessing viable microbiological material below the 2.5 μm size. After sampling, filters were immersed in 300 mL of sterilized distilled water and agitated for 30 min at 100 rpm. 150 μl from the sterilized distilled water were subsequently spread onto malt extract agar (2%) with chloramphenicol (0.05 g/L). All plates were incubated at 27.5 ºC during 5–7 days. With the impinger method, the fungal load ranged from 0 to 413 CFU.m-3 and with the filter method, ranged from 0 to 64 CFU.m-3. In one feed industry, Penicillium genus was the most frequently found genus (66.7%) using the impinger method and three more fungi species/genera/complex were found. The filter assay allowed the detection of only two species/genera/complex in the same industry. In the other feed industry, Cladosporium sp. was the most found (33.3%) with impinger method and three more species/genera/complex were also found. Through the filter assay four fungi species/genera/complex were found. In the assessed poultry, Rhyzopus sp. was the most frequently detected (61.2%) and more three species/genera/complex were isolated. Through the filter assay, only two fungal species/genera/complex were found. In the waste sorting industry Penicillium sp. was the most prevalent (73.6%) with the impinger method, being isolated two more different fungi species/genera/complex. Through the filter assay only Penicillium sp. was found. A more precise determination of occupational fungal exposure was ensured, since it was possible to obtain information regarding not only the characterization of fungal contamination (impinger method), but also the size of dust particles, and viable fungal particles, that can reach the worker ́s respiratory tract (filters method). Both methods should be used in parallel to enrich discussion regarding potential health effects of occupational exposure to fungi.