An Evaluation of Analytical Methods, Air Sampling Techniques, and Airborne Occupational Exposure of Metalworking Fluids

Abstract

This article summarizes an assessment of air sampling and analytical methods for both oil and water-based metalworking fluids (MWFs). Three hundred and seventy-four long-term area and personal airborne samples were collected at four plants using total (closed-face) aerosol samplers and thoracic samplers. A direct-reading device (DustTrak) was also used. The processes sampled include steel tube making, automotive component manufacturing, and small part manufacturing in a machine shop. The American Society for Testing and Materials (ASTM) Method PS42-97 of analysis was evaluated in the laboratory. This evaluation included sample recovery, determination of detection limits, and stability of samples during storage. Results of the laboratory validation showed (a) the sample recovery to be about 87%, (b) the detection limit to be 35 microg, and (c) sample stability during storage at room temperature to decline rapidly within a few days. To minimize sample loss, the samples should be stored in a freezer and analyzed within a week. The ASTM method should be the preferred method for assessing metalworking fluids (MWFs). The ratio of thoracic aerosol to total aerosol ranged from 0.6 to 0.7. A similar relationship was found between the thoracic extractable aerosol and total extractable aerosol. The DustTrak, with 10-microm sampling head, was useful in pinpointing the areas of potential exposure. MWF exposure at the four plants ranged from 0.04 to 3.84 mg/m3 with the geometric mean ranging between 0.22 to 0.59 mg/m3. Based on this data and the assumption of log normality, MWF exposures are expected to exceed the National Institute for Occupational Safety and Health recommended exposure limit of0.5 mg/m3 as total mass and 0.4 mg/m3 as thoracic mass about 38% of the time. In addition to controlling airborne MWF exposure, full protection of workers would require the institution of programs for fluid management and dermal exposure prevention.

Characterization of exposures among cemented tungsten carbide workers. Part I: Size-fractionated exposures to airborne cobalt and tungsten particles

“…An analogous situation exists for the evaluation of the respiratory effects of metalworking fluids, for which NIOSH recommends a thoracic exposure limit (NIOSH, 1998) and using a ratio of 0.8 for converting exposure estimates from total to thoracic concentration, representing a more biologically relevant exposure metric for respiratory effects. Similar ratios of thoracic to total exposure in the range of 0.6 to 0.7 have been reported in a number of studies of metalworking fluid exposures (Reh et al, 2005;Verma et al, 2006).…”

“…Thus, it is important to develop an exposure metric that represents the specific agent(s) that is related to the disease process in order to detect small risks, or risk related to mixed exposures. In the case of occupational asthma among CTC workers, a ratio (conversion factor) of 0.6 to 0.8, as observed in this and other (NIOSH, 1998;Reh et al, 2005;Verma et al, 2006) studies, may be used to convert total cobalt exposure concentrations measured via 37-mm cassette to thoracic equivalent exposures, which represent a biologically more valid metric.…”

Development of a New Method for Analysis of Oil Mists

“…Generally, the presented data in this study, with regards to accuracy, precision, LOD and LOQ, was superior compared to the published validation parameters of the methods presented by NIOSH (24), HSE MDHS NO. 84 (22) ASTM method (25). Overall, the FT-IR spectroscopy method recommended by the present study offers an alternative method for the analysis of the mists of mineral oil, other than methods offered by scientific organizations such as NIOSH.…”

“…International organizations (22)(23)(24) and researchers (11,13,25) No.5026 (23) and NIOSH No.5524 (24), is the lack of specificity for analysis of toxic ingredients found in mineral oils. These methods do not recognize carcinogenic ingredients of mineral oils that would allow for a precise evaluation of occupational exposure.…”

Evaporation of Liquid Semi-Volatile Aerosols Collected on Fibrous Filters

“…More recently, other studies have focused on the re-entrainment in vapor form of cutting oils deposited on fibrous filters, when treating metalworking oil mist (Cooper et al 1998;Riss et al 1999) or during control sampling of ambient concentrations of aerosols (Volckens et al 1999;Simpson et al 2000;Volckens et al 2002;Park et al 2003;Simpson et al 2003;Verma et al 2006;Lim et al 2008).…”