Loading Rates of Dust and Bioburden in Dwellings in an Inland City of Southern Europe

Abstract

Sampling campaigns indoors have shown that occupants exposed to contaminated air generally exhibit diverse health outcomes. This study intends to assess the deposition rates of total settleable dust and bioburden in the indoor air of dwellings onto quartz fiber filters and electrostatic dust collectors (EDCs), respectively. EDC extracts were inoculated onto malt extract agar (MEA) and dichloran glycerol (DG18) agar-based media used for fungal contamination characterization, while tryptic soy agar (TSA) was applied for total bacteria assessment, and violet red bile agar (VRBA) for Gram-negative bacteria. Azole-resistance screening and molecular detection by qPCR was also performed. Dust loading rates ranged from 0.111 to 3.52, averaging 0.675 μg cm−2 day−1. Bacterial counts ranged from undetectable to 16.3 colony-forming units (CFU) m−2 day−1 and to 2.95 CFU m−2 day−1 in TSA and VRBA, respectively. Fungal contamination ranged from 1.97 to 35.4 CFU m−2 day−1 in MEA, and from undetectable to 48.8 CFU m−2 day−1 in DG18. Penicillium sp. presented the highest prevalence in MEA media (36.2%) and Cladosporium sp. in DG18 (39.2%). It was possible to observe: (a) settleable dust loadings and fungal contamination higher in dwellings with pets; (b) fungal species considered indicators of harmful fungal contamination; (c) Aspergillus section Candidi identified in supplemented media with voriconazole and posaconazole; (d) specific housing typologies and (e) specific housing characteristics influencing the microbial contamination.

Aspergillus Section Fumigati in Firefighter Headquarters

“…Previous studies also identified passive sampling as suitable to determine Aspergillus section Fumigati by culture-based methods through sampling of filtering respiratory protective devices and other environmental matrices in settings such as waste-sorting plants, veterinary clinics, dairies, ambulances, and many other indoor and occupational environments [4,10,16,18,32]. In fact, passive sampling is able to characterize contamination levels over a wider period of time, compared to air sampling [21,36]. Thus, higher fungal counts and greater fungal diversity are expected by passive sampling.…”

“…Aspergillus section Fumigati was more frequent in DG18 compared to MEA counts. Despite the recommendation of using MEA for aerobiological studies in a Portuguese regulatory framework dedicated to the assessment of indoor air quality (IAQ) (25APA 2010), DG18 is an efficient option due to its restrictive character, inhibiting the development of fastidious fungal species [21]. The results of some fungal overgrowth on the MEA plates may have influenced the development of Aspergillus sp.…”

“…The ability to use protection against respiratory devices or filters as a sampling approach depends on the features of the assessed setting, activities developed and duration of use, e.g., mop sampling depends on cleaning procedures. The EDC device, on the other hand, allows for the recovery of fungal contamination in a consistent and standardized manner (regarding retention material and collection period), and it is a low-cost, low-maintenance sampling strategy that has been increasingly used in the assessment of occupational exposure to fungal burden [19] and in indoor air quality studies [21,32].…”

“…Concerning passive sampling methods, the floor surfaces were swabbed using a 10 × 10 cm square stencil, which was disinfected between each sample with a 70% alcohol solution [11]. The EDCs were placed in each sampling area 1.5 m above the ground for 30 days [21]. All samples (filters, settled dust, mops, cleaning cloths and identification badges) were kept in sterilized bags and transported under refrigeration (0-4 • C) to the laboratory [18].…”

Electrostatic Dust Cloth: A Useful Passive Sampling Method When Assessing Exposure to Fungi Demonstrated in Studies Developed in Portugal (2018–2021)

“…This sampling method is appropriate for large-scale epidemiological studies intending to measure microbial exposure, and to complement exposure information collected by building inspections dedicated to spotting dampness and mold [ 3 , 4 ]. EDC is also being used to assess microbial contamination using molecular tools as stand-alone analyses [ 4 , 5 , 6 , 7 , 8 ], even the most refined ones such as sequencing [ 2 ], or using side by side, culture-dependent, and independent methods [ 3 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. In fact, the use of qPCR analyses from EDC is a promising tool to accurately measure microbial contamination in dwellings [ 4 , 8 , 24 ].…”