KAN Report 13
|Microorganisms in the workplace atmosphere - Actionomycetes; 2nd edition 04/1999
G. Danneberg/A. Driesel (388 KB)
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Within the framework of the study, existing information has been compiled and an initial approach for possible standardization drawn up in preparation for a standardized measuring process for recording airborne actinomycetes (Gram-positive, mainly aerobic, mycel-forming bacteria) in the workplace atmosphere.
This kind of measuring process is needed since airborne actinomycetes - particularly thermophilic, thermotolerant and mesophilic types - represent a risk for workers, especially as they can cause an allergic lung disease known as extrinsic allergic alveolitis (EAA). Actinomycetes which can be damaging to workers' health are found above all in composting, recycling and mechanical/biological residual waste treatment plants, in closed stables, silos, grain mills and air conditioning systems. High actinomycete concentration in the air we breathe can also occur during soil purification and mushroom cultivation.
2. Developing a measuring strategy for determining actinomycetes
2.1 Problems involved with developing a standardized measuring strategy
One of the main problems involved with developing a standardized measuring process is that all conventional processes used to quantify the aerogenous germ concentration of living and multiplying microorganisms are based on cultivating the germs collected. In the long term, however, the sampling procedures must also make it possible to determine the proportion of dead cells or cell fragments which cannot be cultivated, since these can also cause an allergic reaction.
2.2 Measuring procedure requirements
The measuring process must satisfy the following requirements:
- Simple to use (highly mobile apparatus, easily changeable media, simple cleaning and disinfection, insensitivity towards outside influences)
- Minimum staff, time and financial requirements
- High efficiency (good reproducibility, large measuring range, distinction between different parameters and particle sizes, dead cells and cell fragments also recorded)
- Establishing representative measurement results for worker exposure (average and maximum (worst case) level)
- Provable limit, sensitivity and precision of the measuring procedure must be selected in accordance with a temporary, national guide value (still to be developed) for actinomycetes and their allergy-causing structural units in the workplace air. This guide value represents the standard for occupational hygiene which must be met and, if possible, bettered with the help of technical measures.
- Several parallel measurements should be carried out. The number of individual measurements depends on the sampling period, but there should be at least three.
- In order to determine background exposure, a check measurement should be taken outdoors on the side facing into the wind.
2.3 Proposal for a measuring procedure
The filtration process already tried and tested in practice for measuring dust is recommended for sampling actinomycetes in the workplace atmosphere. As well as analyzing living cells, this process has the advantage that in principle, the proportion of dead cells and cell fragments contained in the sample can also be determined (e.g. of specific allergens by immunoassays or of relevant actinomycetes using specific DNA probes or PCR processes). Further research in this field is, however, necessary.
2.4 Sampling strategy
First of all, the workplace should be assessed with regard to the microorganisms which could possibly occur and the time for which workers are exposed to them.
It is important that
- samples are taken at the level at which air is breathed in and in the worker's direct proximity,
- samples are taken when concentration is at its highest. Relevant operations which are known to subject workers to a lower level of concentration should, however, also be tested if an average level is to be established,
- short sampling times are used in order to minimize damage to the biological material (max. 60 minutes),
- filter materials used are selected to suit external conditions (temperature, humidity).
Special requirements concerning the transport system for actinomycete samples are as follows:
- Time between sampling and laboratory examination: < 24 hours,
- The sample has to be protected from moisture,
- Transport temperature should be no higher than room temperature.
2.6 Detection and differentiation of actinomycetes in the laboratory
Since actinomycetes generally grow more slowly than other bacteria and fungi, it is important to chose for the treatment in the laboratory a culture medium that puts actinomycetes in a better position to be selected.
- As far as the culture medium is concerned, media components which are precisely defined in chemical terms should be used as far as possible (proposal: glycerine-arginine-agar according to El-Nakeeb and Lechevalier, with the addition of suitable antibiotics, e.g. cycloheximide and/or nystatine).
- Incubation should take place at 50°C (thermophilic and thermotolerant actinomycetes) or at 28°C (mesophilic actinomycetes).
- Vaccinated plates should not be incubated for longer than 14 days.
3. Proposal to KAN
This proposal for a measuring procedure should be evaluated in an inter-laboratory test before being introduced into standardization.
Research in the field of measuring procedures for actinomycetes should be supported in order to
- evaluate precisely the effects of sampling strategy, number of samples, sample transport, sample treatment and the culture media used on the quality of measuring results,
- develop the draft of the measuring procedure for airborne actinomycetes on the basis of the aspects just mentioned above.
In addition to the measuring procedure itself, there is need for research in the following areas:
- Comparing conventional procedures for establishing living germs in the workplace atmosphere with alternative procedures which record overall exposure to living and dead germs and their fragments,
- Developing the measuring strategy, supporting epidemiological studies on worker exposure to actinomycetes and creating the basis for establishing a national guide value for actinomycetes.
KAN endorses the results of the study and has decided to publish them as a KAN report.
The report provides a good overview of the information available at the time of the study concerning the measurement of airborne actinomycetes. All measuring procedures relevant to this field have been compared and an initial draft (see annex) developed for a possible measuring procedure suitable for standardization.
Need for KAN and its Secretariat to take action
The proposal for a measuring procedure developed in the study must be evaluated and developed further. KAN sees a particular need for research in the following areas:
- Assessing the effect of examinations carried out in different laboratories
- Effect of sampling procedures, number of samples, sample transport, sample treatment and the culture media used on the quality of measuring results
- Comparability of conventional procedures used to establish living germs in the workplace atmosphere with alternative procedures which record overall exposure to living and dead germs and their fragments
- Developing these procedures with the aim of recording dead cells and cell fragments
- Developing a national guide value
In addition, research projects (e.g. at Bundesanstalt für Arbeitsschutz und Arbeitsmedizin [BAuA], Berufsgenossenschaftlichen Institut für Arbeitssicherheit [BIA]) should be encouraged.
Parallel to this, the proposed measuring procedures should be tried and tested in practice and the proposal revised for the first time before being passed on to the standardization stage. The members of the working group accompanying the project have agreed, within their means, to take part in a necessary one-off inter-laboratory test coordinated by the contractor of the KAN project. KAN is to bear the travel expenses of working group members incurred during on-site sampling.
KAN will then submit the subsequently revised measuring procedure to DIN as a standard proposal.
The results of the study, KAN’s recommendations and the measuring procedure should be passed on to the "Ausschuß für Biologische Arbeitsstoffe" (ABAS). The ABAS should be requested to adapt the measuring strategy in line with existing measuring strategies which it has developed for determining biological work substances.
Need for DIN to take action
DIN should be informed of the results of the study and KAN’s recommendations so that they can be incorporated into the work of WG 5 "Procedures for sampling biological agents" of CEN/TC 137 "Assessment of workplace exposure". DIN is requested to adopt ABAS' results for the measuring strategy and KAN's standard proposal for the measuring procedure.
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