Microbial contamination of laboratory eyewash stations

Status:

completed 12/2004

Aims:

Physical or chemical trauma to the eye should be treated swiftly and with large quantities of liquid. This is not possible with a hand-held eye rinse bottle. For this reason, the laboratories working group of the institution for statutory accident insurance and prevention in the chemical industry recommends the exclusive use of stationary eyewash units in laboratories. In recent years, it has been stated in a number of publications that owing to careless maintenance, the water delivered from such units in an emergency is frequently not hygienically perfect. Chemical trauma to the eye may therefore be followed by microbial infection. In the light of these observations and in response to a proposal by the laboratories working group, a questionnaire for the recording of circumstances and a measurement programme for recording the hygienic condition of stationary eyewash units were developed. More detailed recommendations for installation, maintenance, and perfectly hygienic use of such stationary safety facilities in laboratories were to be derived from the results of the study.

Activities/Methods:

The questionnaire elicited information describing the sampling point and the reference sampling point (a normal water tap in the same laboratory), the technical design of the eyewash units, non-biological background and accompanying information (temperature, pH value; water hardness and chlorine content where applicable), the visual impression and odour of the water samples, and the sample volumes and transport. One litre of water was sampled at all sampling points (eyewash units and reference water taps), both immediately and after three minutes of water flow. Emergency eyewash units for both one and both eyes were studied. Samples should be taken both for documentation of the basic status quo, and at two and four weeks after use of the emergency eyewash units. The following microbiological parameters were studied in the laboratory: total bacterial count [number of colony-forming units (CFUs)/ml] on trypticase-soy-agar (TSA) with fungicide (incubation: 30 °C, 24 h to 7 d); total pseudomonad colony count on cetrimide agar (incubation: 37 °C, 24 h to 7 d) with particular consideration of the incidence of Pseudomonas aeruginosa and of acanthamoeba on water agar infected with Enterobacter cloacae (German Collection of Microorganisms and Cell Cultures (DSMZ) strain number 6234) (incubation: 37 °C).

Results:

Two different types of emergency eyewash units were studied in four different laboratories at the BG Institute for Occupational Safety and Health (BIA). The results may be summarized as follows: With the majority of samples, a substantial reduction in the bacterial contamination was observed after three minutes' water flow. A new facility in one laboratory, which had been installed only three months previously, revealed similar colony counts to those in older facilities (in some cases in use since 1993). The highest bacterial concentrations, of > 3,000 CFU/ml water, were measured in a laboratory at ground-floor level. The lowest concentrations (< 1 CFU/ml) were measured in a laboratory on the first floor of the building. Higher bacterial counts were measured on eyewash units for one-hand operation (with flexible tube). This finding may be related to the greater ease with which biological film can form on the tube wall. Four weeks after the first sampling, higher colony counts were measured in the majority of cases. Pseudomonads were detected in very low concentrations (< 1 to 3 CFU/ml) in all samples. Nine different species of bacteria were identified physiologically. Conversely, no pathogenic acanthamoeba were detected in the samples; various other amoeba species were detected. A general recommendation for the selection, installation and maintenance of laboratory eyewash stations is not possible at the present time, owing to the lack of data available to date. The topic remains the subject of attention, however, in co-operation with the Laboratories working group within the BG expert committee Chemical Industry and the State Institute for Occupational Health and Safety of Northrhine-Westphalia (LAfA NRW): further studies are planned into the colonization of various materials with biofilms.

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