Question: Do you have the normal mold levels for various types of mold, i.e. Cladosporium cladosporioides? Thank you.
Answer: Currently there are no widely accepted normal airborne mold levels. Although no exposure standards have been established that relate health effects to specific airborne mold levels, there are concerns from public health agencies regarding exposure to mold. Much evidence exists indicating that indoor exposures to molds contribute to occupant respiratory disease and symptoms. Mold levels are used to give us an indication of whether the occupants are exposed to mold originating from indoor environment. According to the American Conference of Government Industrial Hygienists (ACGIH), indoor mold levels should be less than 1/3 of outdoors levels. If indoor levels are above this amount, action should be taken to identify the source or location of mold growth and remove it. It’s important to note that the outdoor levels of mold can vary quite a lot over the different seasons and even week to week and the same is reflected indoors.
In the literature, 3000 spores per cubic meter of air is quoted as the allergenic threshold for Cladosporium. More recently a figure of 4000 spores per cubic meter of air has been cited. For Alternaria, 100 spores per cubic meter of air is cited in the literature as the allergenic threshold.
It is normal to find mold spores in any indoor environment in the air and surfaces such as clothes, walls, and furniture. Most of the time mold spores found indoors during a mold inspection is from outside sources and do not pose a hazard. Regular housekeeping cleaning helps keep mold levels low. Cleaning small areas of visible mold, like the mold around your shower, is important to maintain sanitary conditions.
References
- Hollins, P.D., P.S. Kettlewell, M.D. Atkinson, D.B. Stephenson, J.M. Corden, W.M. Millington and J. Mullins. Relationships between airborne fungal spore concentration of Cladosporium and the summer climate at two sites in Britain. International Journal of Biometeorology Volume 48, Number 3, 137-141.