A "dust bunny" seen under a microscope.
Dusts are ubiquitous. They can be generated from many sources, indoors and outdoors, human/animal activities, construction, combustion, etc.
Benefits of Dust Characterization
Dust characterization can be a very useful and important tool for industrial hygienists (IH) or indoor air quality (IAQ) professionals to evaluate a building-related illness.
Traditional IAQ investigation involves air sampling for a short period of time. For example: Spore trap sampling for fungal spores are typically performed between 5 and 10 minutes, for a snapshot of the indoor air.
In comparison, dust characterization can obtain crucial information about the history of the living environment ranging from weeks to even months as long as the selected surfaces have not been thoroughly cleaned for that period of time.
Our human bodies shed approximately 10 grams of skin scales each day, which is a significant portion of a typical household dust sample.
Certain constituents in the dust can have health consequences, such as pollen, fungal spores, and soot, but most people are immune to a normal amount of dust exposure.
Approximately 30% of Americans have an allergy and/or asthma, especially young children. Anyone can get sick in an environment filled with allergens such as cat or dog danders, or get skin irritation from fiberglass exposure.
Other constituents of the dust may not be a direct health concern themselves, but can be an indicator of something significant. For example, excessive percentage of skin cells in a dust sample may indicate an inefficient HVAC filtration system.
If an investigator needs to know what’s in the air at the moment of sampling, spore trap sampling can be used. Spore trap sampling may be utilized to find out if the air in a house is contaminated with soot after a nearby wildfire, for example.There are many ways for collecting samples for dust characterization analysis. The easiest way is to collect bulk dust from the concerned areas using microvac method or even a household vacuum cleaner. Alternatively, dusts can be collected using swab or tape lift method.
Polarized Light Microscopy
Polarized light microscopy (PLM) is the most common method for dust characterization because it is fast and affordable.
Under this method, dust components are identified based on morphology and optical properties. The bulk dust is first examined under a stereoscope and then identified under PLM. Each component is semi-quantified using calibrated visual estimation. The detection limit of dust characterization using optical microscopy is 1%.
At Eurofins, dust components are broken into five common categories:
- human/animal activities (e.g., skin scales, dandruff, animal fecal, hair, cellulose fibers, etc.)
- food particles (e.g., salt, sugar, starch, etc.)
- combustion product (e.g., ash, carbon, soot, iron oxides, etc.)
- building material (e.g., fiberglass, gypsum, calcite, silicates, paint, plaster, etc.),
- miscellaneous (e.g., rubber, plastic, soil, stellate hair, air distribution system debris, etc.)
- Polarized light microscopy does not provide you with the chemical composition of the dust and it is difficult to identify small particles and especially at low concentrations.
- Interpretation of results can be difficult sometimes because there is currently no regulation on acceptable dust constituents.
- There is no accreditation to perform this type of analytical work. Therefore, it is imperative dust characterization samples be analyzed by experienced analysts.
Eurofins has been performing this type of testing for our satisfied customers for over twenty years and helped them solve many IAQ mysteries.