Fw: IAQ Tech Tip #38 - Surface Sampling Versus Swab Sampling

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> Surface Sampling, Tape Sampling Versus Swab Sampling: IAQ Tech Tip #38

>

> Surface sampling during IAQ investigations is a common tool used by

investigators. It is often performed in conjunction with air and bulk

sampling techniques and its nondestructive nature serves several useful

purposes. Surface sampling can be performed to determine whether microbial

levels in various areas are greater than background levels and to determine

possible sources of microbial contaminants that may be a source of

aerosolization. Surface sampling is also useful for performing

presence/absense analyses and measuring relative degrees of contamination.

>

> Microbial contamination on surfaces can be caused by the settling of

previously aerosolized organisms or by the actual surface acting as a medium

for the growth of the organism. Sampling strategies vary from randomly

picking areas to highly targeted sampling strategies. Two of the most

common surface sampling techniques for fungi include swab sampling and tape

sampling. Each method has its advantages and disadvantages and should be

chosen based on the sampling strategy and the purpose of the investigation.

>

> Tape sampling is a common and easy to perform surface sampling technique.

It is a very useful tool so long as information about the viability of the

microorganism is not required since tape samples cannot be cultured. The

investigator needs only clear adhesive tape for obtaining the samples and

glass slides or a sterile container or ziplock bag to transport the samples

to a laboratory. The investigator removes a portion of the clear tape,

approximately one to two inches long, and places the adhesive side on the

surface to be sampled. If the sample contains to much debris it may then be

difficult to examine in the laboratory and the sample should be retaken.

>

> There are a number of benefits to tape sampling. These include the ease

of sampling, lack of expensive sampling supplies, and no requirements to

ship the samples rapidly in any type of refrigerated containers. Tape

samples are also rapidly processed and generally an investigator can expect

to receive results in approximately one day. The value of the data

generated by tape sampling depends heavily on the investigators choice of

sample locations. A single surface with visible growth may have multiple

fungi present in different areas and thus one sample may not give an

accurate representation of the various species present. Tape samples cannot

be cultured for the determination of viable versus nonviable contamination

nor is it useful for the determination of bacteria.

>

> Swab sampling is the other common nondestructive surface sampling

technique. It can be used for a microscopic screen and fungi identification

and it can also be cultured onto a media for viable fungi and bacteria

indentification. One weakness of using swabs for microscopic identification

over tape methods is that more fungal stuctures tend to be disrupted and

thus makes laboratory identification more difficult. It is of course

important to use a sterile swab when performing this sampling technique and

it should be clearly stated to the laboratory if the sample is for

microscopic identification and/or culture methods.

>

> The ability to recover various organisms is also dependent on the surface

material to be tested. Generally smoother surfaces are more easily and

effectively sampled using surface sampling techniques. Porous and fleecy

areas are often more difficult to sample utilizing tape and swab sampling

techniques. When utilizing these methods it is a good procedure to send a

blank to the laboratory for quality control purposes.

>

> " Several attempts have been made to identify surface concentrations of

biological materials that indicate unhealthy conditions. No currently

available guidelines have been generally accepted due to the large

variability in surface sampling results and poor correlations with

inhalation exposre " (ACGIH, Bioaerosols Assessment and Control, 12.2.4).

This position by the ACGIH exemplifies the need to use surface sampling data

as a tool in conjunction with other aspects of the IAQ investigation to help

support or disprove a hypothesis of an investigation.

> __________________________

> IAQ and Related News & Events

> ^^^^^^^^^^^^^^^^^^^^^^^^^^

> Microbial Fact #1: Bacillus and Clostridium are gram-positive, rod

shaped bacteria able to produce highly resistant endospores. The spores can

be found in soil and air. Species of Bacillus grow aerobically, and

Bacillus anthracis is the cause of anthrax. Clostridium species grow

anaerobically and different species cause tetanus, botulism, and gas

gangrene.

>

> Fungal Fact #1: Penicillium notatum and some closely related species of

penicillium are occasional causes of infections in man. Pulmonary infections

are rare, but it can infect the ear and cornea. It has been identified as a

contributing cause in some cases of Sick Building Syndrome. Penicillium

notatum can produce penicillin, and some people are highly allergic to this

antibiotic.

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> NEWSLINK

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> _________________

> IAQ CONFERENCES

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> *** IAQ Conference: 2000 Northwest Occupational Health

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>

> *** A unique conference for industrial hygienists brought to you

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Opryland Hotel, Nashville, TN. Any questions, please contact

aihaupdate@...

> ______________

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