About Aspergillus niger
Aspergillus niger is one of the most immediately recognizable indoor molds: the black fuzzy growth found on damp drywall, bathroom grout, and food items like onions and spices. It is a documented allergen capable of causing respiratory sensitization, sinus infections, and ear infections (otomycosis). Certain strains produce ochratoxin A (nephrotoxic and potentially carcinogenic). Its large, easily aerosolized spores create a significant airborne allergen load, and disturbing A. niger growth during vacuuming or renovation can dramatically spike indoor spore counts.
Ecology and water requirements
Aspergillus niger is classified as a primary colonizer with xerophilic adaptations: capable of germinating and growing at water activity as low as Aw 0.77[2], well below what most molds tolerate. Primary colonizers establish first in damp or even mildly humid environments, often before any visible moisture problem is apparent. Elevated Aspergillus niger on an ERMI test is more often associated with long-term high humidity than with a sudden water event[3]. Common contexts include poorly ventilated areas, conditioned-vs-unconditioned boundary zones (attics, crawl spaces, unfinished basements), and dusty environments where ambient relative humidity is sufficient to support growth on settled organic material.
Mycotoxin biology
Aspergillus niger 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[4]. The same isolate may produce substantially different metabolite profiles on drywall paper versus wood versus settled dust[5]. 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 niger 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 niger is documented on the following substrates and locations:
- Damp drywall
- concrete
- bathroom surfaces
- food items (onions
- spices
- grapes)
- mattresses
- house dust
- HVAC
Mycotoxins
Compounds documented as produced by Aspergillus niger (presence and quantity vary by chemotype, strain, and substrate):
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 niger 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 niger in that broader pattern.
Mycotoxins and extended panels
Related reference pages: the mycotoxins Aspergillus niger can produce, and the extended-panel species most closely related to it:
Related species
References
- 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.
- Pitt JI, Hocking AD. Fungi and Food Spoilage. 3rd ed. New York: Springer; 2009.
- World Health Organization. WHO Guidelines for Indoor Air Quality: Dampness and Mould. Copenhagen: WHO Regional Office for Europe; 2009.
- Nielsen KF. Mycotoxin production by indoor molds. Fungal Genet Biol. 2003;39(2):103–117.
- Miller JD, McMullin DR. Fungal secondary metabolites as harmful indoor air contaminants: 10 years on. Appl Microbiol Biotechnol. 2014;98(24):9953–9966.