A major manufacturer has been receiving complains from his employees about incidents of frequent, often respiratory, illnesses in the workplace. The employees were concerned that maybe a high level of pathogenic bacteria and moulds on the work surfaces may be responsible for their illnesses. I have been appointed to evaluate the atmospheric concentration of viable moulds and bacteria in the working areas, to measure the level of surface bacterial contamination and to evaluate whether the employees are really at risk to health.
The manufacturing facility I have evaluated consist of several production and ancillary buildings. The main production areas are situated in three individual locations. The first area in the main building complex is an open floor production facility with a large number of various metal working and testing machines. The second area is situated in another building and consists of a small metal working area situated in the centre of the building. The third area is an open plan workshop housing several metal working machines such as lathes and mills.
To representatively evaluate the levels of bacterial contamination in the air, firstly air samples have been collected on to TSA agar from the outside environment and also from similar but non-problem areas. The non-problem areas were selected on the bases they contained similar kind of machinery and working processes. These samples served as a baseline for normal bacterial and mould burden in the outside and non-problem areas air.
The concentration of viable moulds in the non-problem areas ranged between 230 CFU/m3 and 570 CFU/m3. The average environmental background concentration of viable moulds was 390 CFU/m3. The concentration of viable bacteria in the non-problem areas ranged between 520 CFU/m3 and 8800 CFU/m3.
Following the collection of background samples several air samples have been collected in the problem area of the factory. The concentration of viable moulds in the problem area ranged between 300 CFU/m3 and 660 CFU/m3. The concentration of viable bacteria in the problem area ranged between 260 CFU/m3 and 340 CFU/m3.
Following the collection of air samples a number of samples have been collected from the work surfaces both in problem and non-problem areas. Surface bacterial contamination on metal working machines in the non-problem area ranged between 1 CFU/100cm2 and 40 CFU/100cm2.
Surface bacterial contamination on metal working machines in the problem area ranged between 0 CFU/100cm2 and 330 CFU/100cm2.
Evaluation of airborne viable moulds in the working environment indicates that there is no significant difference of the airborne mould levels between the problem area and the environmental background and non-problem areas. Evaluation of airborne viable bacteria in the working environment indicates that there is no significant difference of the airborne mould levels between the problem area and the environmental background and non-problem areas. Overall evaluation of surface bacterial contamination between the problem and the non-problem areas indicates that there is not a significant difference in the surface bacterial contamination of both working areas.
By Tomas Gabor
