Indoor Molds


Fate and Transport in the Environment

Methods for Monitoring in the Environment

Exposure Pathways

Methods for Measuring Human Exposure

Strategies for Preventing or Controlling Mold Exposure

Harmful Effects

Absorption, distribution, metabolism, and sites of toxicity


Molecular mechanism of action

Risk Assessment

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Methods for measuring human exposure to molds

Personal sampling is the most accurate method to a get fairly good measurement of mold exposure. A mold spore-sampling cassette is worn by a person within the breathing zone. Due to the limited flow rate capacity of a personal sampling pump, personal sampling should be conducted with a flow rate between 0.5 to 5.0 liters per minute. For workers, the ideal sample time is 8 hours in order to calculate an 8-hour time weighted average for a typical workday. A 30-minute excursion sample can also be collected at the time of estimated maximum exposure. The same principles can be applied to sampling in a residential setting.

Most airborne sampling methods for mold require high flow rates that only can be obtained from high volume pumps. Determining the airborne mold concentration by personal sampling is fairly limited due to the typical requirement of high flow rate. Two sampling methods are particularly well suited to measuring exposure using personal sampling because they do not require a high flow rate. These methods include using Laro 100 cassettes and Micro5 Microcell cassettes attached to a personal sampling pump.

Personal sampling during mold abatement

Laro 100

The Laro 100 air-sampling cassette is an ideal method to analyze personal exposure to mold. Mold spores are collected on 0.8 micron mixed cellulose ester filter (like an asbestos PCM cassette). It is capable of capturing 100% of all airborne fungal particulate as well as any particulate or fibers 0.8 microns and greater in size. The sample can be analyzed immediately after collection by optical microscopy. Eight hour personal samples can be taken at 1.0 to 2.0 liters per minute to obtain 300 to 480 liters. Overloading the sample can be a problem in dirty environments. Blank samples and outdoor control samples should be submitted with the personal samples. Laro 100 samples can also be cultured by dissolving the filter in water, extracting the water, and culturing the water on an agar plate.

Cultured mold sample on MEA (Malt extract agar)


The Micro5 Microcell airborne mold-monitoring cassette is another method to analyze personal exposure to mold. The Micro5 cassette contains a glass slide with adhesive that captures the mold spores when they impact the slide. The Micro5 has a 50% collection efficiency of 0.8 microns at 5 liters per minute. Micro5 samples can be analyzed immediately after collection by optical microscopy. The flow rate for the Micro5 must be set at 5 liters per minute to obtain a target sampling volume of 25 liters. Like the Laro 100, overloading the sample can be a problem in dirty environments. Blank samples and outdoor control samples should be submitted with the personal samples. The weakness of this method is the short time duration used to collect the sample. A five-minute sample may not give an accurate exposure concentration for an eight-hour workday. In order to collect 8 hours of sampling data, 96 samples would need to be collected.

Micro5 microcell cassette
Correct placement of a personal sampler

Limitations of personal sampling for airborne mold

After personal sample analysis is conducted, reaching a conclusion about the results can be problematic. There are no current established standard occupational exposure limits or Threshold Limit Values (TLVs) for personal sampling with regard to concentration or specific species of mold. However, laboratory testing does exist to generally evaluate mold concentrations and populations. Airborne mold testing can be used, in conjunction with control samples, to determine if the workers are experiencing elevated concentrations and abnormal populations of mold. Calculating acceptable exposure is at the discretion of the investigator.

Personal sampling for a small time period can give a limited "snapshot" view of the mold concentration. With a short sample period it is difficult to determine if the sample is representative of a minimum, average, or maximum concentration. Additionally, analyzing some species of mold spores can be difficult. It is not possible to differentiate between Aspergillus and Penicillium spores by direct examination. In fact many fungal spores cannot be positively identified by direct examination and can only be identified by growing a cultured sample.


Goddish, Thad. Indoor Environment Notebook: Everything You Wanted to Know About Indoor Air Pollution and More. Ball State University, Department of Natural Resources and Environmental Management. Updated 02/15/02. 10/6/03

LARO-100 Product Information, 2002. 10/6/03

EMSL Analytical, LARO-100 Sampling Guide. 10/6/03

Grinshpun, Surgey A. Collection and Enumeration of Airborne Spores Using Aerosol Impactors with Low Jet-To-Plate Distance, Project 3, Micro5 Microcell (5 lpm). University of Cincinnati Environmental Health Foundation. 4/15/02.