This paper summarizes the analytical and occupational hygiene findings from a recent survey of occupational exposure to metalworking fluids (MWFs) in the engineering industry. The aim of the survey was to link MWF mist exposure measurements with particular engineering processes and controls, and utilize the data obtained to develop exposure standards. At the same time the opportunity was taken to assess fluid management and control, including bacterial and fines contamination in the machine sumps. In general, occupational exposure to mineral oil MWF mist was controlled to <3 mg/m(3) (8 h time-weighted average) and to <1 mg/m(3) for water-mix MWF mist (in terms of the concentrate). These exposure values do not necessarily represent best practice, but are believed to be achievable and representative of industry as a whole. Gravimetric analysis of the total inhalable particulate was found to be a good predictor of mineral oil MWF mist but not for water-mix MWF mist. Grinding and drilling operations produced higher exposures than turning and milling for water-mix fluids. There were insufficient data to compare machining operations for mineral oil MWFs. On the whole, fluid management was found to be poor, with most sites failing to meet industry good practice or Health & Safety Executive (HSE) standards. Some of the operating procedures utilized were deficient or unsatisfactory. Poor standards of fluid management were found at all sizes of company. High levels of bacteria, endotoxin and fines were found in sumps, and control of other factors, such as water-mix fluid concentration, was often poor. Mineral oils had higher levels of fines than water-mix fluids (medians of 395 and 18 mg/l, respectively), and grinding produced high levels of fines in both types of MWF. Many water-mix sumps contained bacterial levels of >1 x 10(6) CFU/ml, and endotoxin levels of >100 000 EU/ml were not uncommon. The median values were 109 000 CFU/ml and 8039 EU/ml, respectively. Mists could potentially contain extensive contamination from bacteria and endotoxin. Analysis of the data suggests that sumps operating under typical conditions for machining (a temperature of 20 degrees C, a pH of 9 and a fluid strength below 10%), also appear to provide optimum conditions for the proliferation of bacteria. Low levels of benzo[a]pyrene (median 0.03 micro g/g) were found in the mineral oils, and low levels of N-nitrosodiethanolamine (median 0.4 micro g/ml) were found in the water-mix MWFs. The results of this work will contribute to guidance from the HSE, setting out accepted industry good practice, including guide values for MWF mist and sump fluid contaminants, with significant emphasis on sump fluid management (maintenance and monitoring), as well as control issues.
On October 15, 2002, the United Kingdom (UK) Health and Safety Executive (HSE) launched new guidance for the engineering industry, aimed at reducing health risks from metalworking fluids (MWFs). This guidance was the culmination of many years of work on this subject. In the early 1990s, the UK occupational exposure standards (OES) for oil mist were 5 mg/m(-3) 8-hour time-weighted average (TWA), and 10 mg/m(-3) short-term exposure limit (STEL). This was only applicable to highly refined mineral oil mists and there was no exposure limit for water-mix MWFs (emulsions, semi-synthetics, and synthetics). HSE therefore undertook to review the existing exposure limit for neat mineral oil mists (neat oils are fluids that contain highly refined mineral oils and additives, and are used neat without mixing with water) and consider developing one for water-mix MWFs. This led to the development of new air-sampling methods, a comprehensive survey, and the development of new good practice guidance in the place of statutory exposure limits. This new good practice guidance has been endorsed and launched with the help of relevant industry supplier, employer, and employee associations. The guidance builds on the philosophy of tackling health risks as a holistic approach; for example, not just tackling mist control through the use of ventilation, but also fluid selection, fluid delivery, and fluid management (fluid management means to effectively manage all aspects of the fluid, from storage and stock preparation to sump cleaning and fluid disposal, etc.). Tools, such as laminated task sheets, are provided to make it user friendly. It also demonstrates the business benefits from this approach, that managing your MWFs effectively can reduce the incidence of ill health, reduce fluid and disposal costs, increase tool life, and improve machining performance.
This article provides a summary of the Health and Safety Executive’s (HSE) work over recent years to address occupational exposure to particulates during the manufacture and use of coating powders. It contends, in particular, that many users of coating powders are not controlling exposure to total inhalable particulate (TIP) (i.e. the total inhalable dust in the air from all sources), and that these control issues would exist even if TGIC (triglycidyl isocyanurate) was not being used. TGIC is a curing agent for polyester coating powders which is classified as a Category 2 mutagen. HSE is raising awareness that control of exposure is generally poor whatever powders are being used.
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