Metalworking fluids are used to cool and/or lubricate metal works during machining, grinding, cutting, milling, etc. MWFs can get contaminated when good hygiene practices are not followed or when fluids are not properly managed or maintained. Bacterial and fungal contamination of metalworking fluids (MWFs) is a major concern in the industries which use these fluids. Contamination may cause equipment malfunction, off-odors, degradation in the fluid quality, economic losses and finally, they pose as a major health hazard. Several Gram +ve and Gram -ve bacteria are found as contaminants. These include Staphylococcus sp., Bacillus sp., Pseudomonas sp., Proteus sp. and Coliforms. Fungal contaminants include, Aspergillus sp., Penicillium sp., Fusarium sp. and Cephalosporium sp.
Major health concerns of bacterial and fungal Contaminated metalworking fluids include skin irritation, allergic contact dermatitis, irritation of the eyes, nose and throat, and, occasionally, breathing difficulties such as bronchitis and asthma. Learn more about contamination of metalworking fluids.
Viable air samples are often collected on agar media either in strips (if using Reuter Centrifugal Sampler) or in Petri-dishes for Andersen sampler. Unlike non-viable air sampling, detection and subsequent enumeration and identification of airborne fungal particulates collected on growth media depends on whether the spores and hyphal fragments are viable and whether the media used can support their growth into colonies. For this reason, colony counts are usually lower than spore counts. Even if all the fungal structures were viable, colony counts are likely to be lower than the spore/hyphal fragment counts because what is counted as a single colony could have developed from more than a single spore or hyphal fragment. In one study it was found that the ratios between the total fungal spores collected by the Burkard sampler and the viable fungi collected by the Andersen sampler ranged between 0.29 and 7.61.
Is Non-viable Fungal Air Sampling Alone Adequate? In most cases viable air sampling is only used in situations where identification of the moulds to species level is required. However, our observation in the lab seems to suggest use of spore traps alone may not be adequate for airborne fungal sampling. On many occasions we have recovered moulds in viable samples that were not observed in non-viable samples even when viable and non-viable samples were taken side by side. For example Chaetomium and Stachybotrys spores, which are fairly easy to identify from spore traps have appeared in viable samples, yet, they were not detected from the non-viable samples. We have also observed that although non-viable sampling gives higher counts than viable sampling in most cases, this is not always the case. There are many factors that can contribute to these “unexpected” results.
Since both non-viable and viable air sampling have limitations, using either method singly is not adequate. To obtain conclusive information on the level of contamination and the diversity of airborne fungi in a building, taking both viable and non-viable air samples is preferable. We recommend the Calgary Health Region’s protocol, “Fungal Air Testing, Investigation and Reporting Requirements for Residential Marihuana Grow Operations (Revised May 2006)”. With few exceptions, the protocol requires that fungal air sampling consist of both viable samples (e.g. RCS or similar) and non-viable samples (e.g., Air-O-Cell) taken side by side.