Fungal fragments in moldy houses: A field study in homes in New Orleans and Southern Ohio

Abstract

Smaller-sized fungal fragments (<1 μm) may contribute to mold-related health effects. Previous laboratory-based studies have shown that the number concentration of fungal fragments can be up to 500 times higher than that of fungal spores, but this has not yet been confirmed in a field study due to lack of suitable methodology. We have recently developed a field-compatible method for the sampling and analysis of airborne fungal fragments. The new methodology was utilized for characterizing fungal fragment exposures in mold-contaminated homes selected in New Orleans, Louisiana and Southern Ohio. Airborne fungal particles were separated into three distinct size fractions: (i) >2.25 μm (spores); (ii) 1.05-2.25 μm (mixture); and (iii) < 1.0 μm (submicrometersized fragments). Samples were collected in five homes in summer and winter and analyzed for (1→3)-β-D-glucan. The total (1→3)-β-D-glucan varied from 0.2 to 16.0 ng m −3 . The ratio of (1→3)-β-D-glucan mass in fragment size fraction to that in spore size fraction (F/S) varied from 0.011 to 2.163. The mass ratio was higher in winter (average = 1.017) than in summer (0.227) coinciding with a lower relative humidity in the winter. Assuming a mass-based F/S-ratio=1 and the spore size = 3 μm, the corresponding number-based F/S-ratio (fragment number/spore number) would be 10 3 and 10 6 , for the fragment sizes of 0.3 and 0.03 μm, respectively. These results indicate that the actual (field) contribution of fungal fragments to the overall exposure may be very high, even much greater than that estimated in our earlier laboratory-based studies.

Indirect Immunodetection of Fungal Fragments by Field Emission Scanning Electron Microscopy

“…This difference may be associated to the assay efficiency or the size range that was wider in the present study. Other studies that focused on the occurrence of submicronic fragments in mold-contaminated indoor or outdoor air used methods to detect ␤-glucan (14,16,18,47) and NAHA (21) as biomarkers of fungal fragments in size-fractionated samples. However, these studies were limited by the imprecise fractionation of particles due to confounding variables such as spore bounce (18,47,48).…”

“…Methodological advances have been made in a number of studies by using fungal membrane constituents such as ergosterol, phospholipid fatty acids, and (1¡3)-␤-D-glucans to demonstrate the presence of fungal biomass in size-fractionated fungal aerosols (9)(10)(11)(12)(13)(14)(15)(16). Further, sugar alcohols (arabitol and mannitol) (17), enzymes (N-acetyl hexosaminidase and N-acetyl-D-glucosaminidase) (18)(19)(20)(21)(22), antigens, allergens (23)(24)(25)(26), and DNA (27)(28)(29) have been used as proxies for total fungal exposure or occurrence of airborne fungal particles.…”

Fungi, Bacteria, Nano-particulates, Mycotoxins and Human Health in Water- Damaged Indoor Environments

“…Of the mold particulates the greatest concern is the nano-particulates at or less than 0.3 microns shed from mold colonies. Field studies of water-damaged homes have shown concentrations of nano-particulates in indoor dust that are at least 1000 times or greater than the indoor air mold spore counts [12][13][14][15][16][17][18]. These particulates contain 1, 3-beta glucans, a variety of fungal proteins that include substrate enzymes as well as mycotoxins.…”

“…It is associated with nano-particulates shed by mold that contain 1, 3-beta glucans, mycotoxins and a variety of antigenic proteins [14,21,25,[48][49][50][51][52][53][54][55].…”

“…All of these situations lead to both hidden as well visual signs of fungal and bacterial growth. For simplicity, "water intrusion" will be used as all encompassing term [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”