Mesophilic

Aspergillus unguis

Aspergillus unguis is a member of Aspergillus section Nidulantes, a group that includes several species associated with water-damaged indoor environments.

Water-damage indicatorMesophilic · Aw ≥ 0.83

Moisture niche · where this species can grow

XerophilicAw < 0.80
MesophilicAw 0.80–0.89
HydrophilicAw ≥ 0.90
Min Aw 0.83
← Drier conditions toleratedRequires liquid water →
Minimum Aw
0.83
EPA reference (GM)
2 SE/mg
Mycotoxin profile
2+ documented
Ecological role
Secondary colonizer

About Aspergillus unguis

Aspergillus unguis is a member of Aspergillus section Nidulantes, a group that includes several species associated with water-damaged indoor environments. It has been documented as a producer of sterigmatocystin in some strains. Like other section Nidulantes members, it requires moderate moisture to grow and is generally found in areas with secondary moisture problems such as condensation zones, damp crawl spaces, or materials with sustained water contact.

Ecology and water requirements

Aspergillus unguis is classified as a secondary colonizer with mesophilic moisture requirements: capable of growing at water activity in the range Aw 0.83 and above[2], typical of condensation surfaces and freshly damp materials. Secondary colonizers follow primary xerophilic species in the ecological succession that develops on damp building materials. Detection of elevated Aspergillus unguis on an ERMI suggests intermittent or recent moisture conditions consistent with condensation, vapor permeation, or short-lived water events: chronically cool surfaces (uninsulated walls, single-pane windows, plumbing chases) and bathrooms or kitchens with insufficient ventilation are typical contexts.

Mycotoxin biology

Aspergillus unguis produces a range of secondary metabolites with biological activity. The compounds documented in the literature for this species are listed in the chips below. Mycotoxin production is not uniform across all strains and is influenced by substrate, temperature, and water activity[3]. The same isolate may produce substantially different metabolite profiles on drywall paper versus wood versus settled dust[4]. DNA-based detection via the ERMI panel identifies species presence but does not directly measure mycotoxin presence; detection of a mycotoxin-producing species in household dust does not establish exposure to that mycotoxin at any specific concentration.

Detection in dust versus visual inspection

DNA-based detection of Aspergillus unguis in settled household dust (the basis of the ERMI panel[1]) integrates spore material from current and recent growth in the home, capturing exposure history over weeks to months. A positive detection in dust does not necessarily indicate currently-active growth at the time of sampling; conversely, an active growth site can produce relatively low dust spore counts if the spores are not being aerosolized (sealed wall cavities, behind vapor barriers, or under flooring). Interpretation requires considering the dust signal alongside building inspection, occupant symptom history, and the broader pattern of species detected on the panel.

Where it’s typically found

Aspergillus unguis is documented on the following substrates and locations:

  • Water-damaged building materials
  • damp indoor surfaces
  • soil

Mycotoxins

Compounds documented as produced by Aspergillus unguis (presence and quantity vary by chemotype, strain, and substrate):

Sterigmatocystin· some strainsPenicillic acid

Mycotoxin production is not uniform across all strains and is influenced by substrate, temperature, and water activity. Detection of a mycotoxin-producing species in household dust does not directly establish exposure to that mycotoxin at any specific concentration.

On your ERMI report

Aspergillus unguis is one of the 26 EPA water-damage indicator species used to compute the SLG1 component of the ERMI score (sometimes labeled "Group 1" in EPA documentation). Whether the level detected in any specific home is concerning depends on the broader pattern: which other species are elevated, the water-activity profile of the elevated species, the home's climate context, and (where relevant) the occupant's sensitivity history. Our interpretation report puts Aspergillus unguis in that broader pattern.

Related species

Aspergillus flavus/oryzaeAw ≥ 0.78 · XerophilicAspergillus fumigatusAw ≥ 0.82 · MesophilicAspergillus nigerAw ≥ 0.77 · XerophilicAspergillus ochraceusAw ≥ 0.77 · Xerophilic

References

  1. Vesper SJ, McKinstry C, Haugland RA, et al. Development of an Environmental Relative Moldiness Index for U.S. homes. J Occup Environ Med. 2007;49(8):829–833.
  2. Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.
  3. Nielsen KF. Mycotoxin production by indoor molds. Fungal Genet Biol. 2003;39(2):103–117.
  4. Miller JD, McMullin DR. Fungal secondary metabolites as harmful indoor air contaminants: 10 years on. Appl Microbiol Biotechnol. 2014;98(24):9953–9966.