A field investigation of the acute respiratory effects of metal working fluids. II. Effects of airborne sulfur exposures

A comprehensive review of the literature on exposure to metalworking fluids

An extensive literature review was conducted of studies with exposure measurements to metalworking fluids (MWFs). A database of 155 arithmetic means based on 9379 aerosol measurements from published studies was compiled. Weighted arithmetic means (WAMs) and their variance calculated across studies were summarized based on decade (prior to 1970s through 2000s), industry (auto, auto parts, small job shops, and others), operation (grinding and machining), and fluid type (straight, soluble, synthetic, and semisynthetic). Total mass and total extractable mass measurements that were simultaneously collected were compared. Average concentrations by size fractions and mass median aerodynamic diameters (MMADs) were also analyzed. Analysis of the WAMs indicated a reduction in exposure levels over time regardless of industry or type of operation or fluid, with mean levels prior to the 1970s of 5.4 mg/m(3), which dropped to 2.5 mg/m(3) in the 1970s, to 1.2 mg/m(3) in the 1980s, and to 0.5 mg/m(3) in the 1990s. No further reduction was seen in the 2000s. A comparison by industry, operation, and fluid type found no consistent patterns in the measurement results. The percent extractable mass in the total aerosol samples varied by fluid type, with an average 84% in straight fluids, 58% in synthetic fluids, 56% in soluble fluids, and 42% in the semisynthetic fluids. Exposure means from the thoracic fraction (0.3-0.5 mg/m(3)) were slightly less than those for total aerosol for both the 1990s and 2000s, the only decades for which thoracic data were available. Respirable means did not change from the 1980s to the 2000s (generally about 0.2-0.3 mg/m(3)). The MMADs of the MWF aerosols averaged 4-6 microm. These measurement data indicate a clear reduction of exposure levels over time. They will be used for the retrospective assessment of exposure levels to MWFs in a population-based, case-control study of bladder cancer.

Short-term effects of formaldehyde on peak expiratory flow and irritant symptoms

The authors studied the respiratory effects of formaldehyde exposure among students who dissected cadavers in a gross anatomy laboratory. Peak expiratory flow and respiratory symptoms were measured before and after each weekly laboratory session. Each of 38 students was exposed to formaldehyde for 2.5 hr/wk for 14 wk. Individual, daily formaldehyde measurements averaged 1.1 ppm (standard deviation = 0.56 ppm). Multivariate models demonstrated two different time scales of effect of formaldehyde on peak expiratory flow: (1) exposure during the previous 2.5 hr reduced peak expiratory flow by -1.0% per ppm, and (2) average exposure during all preceding weeks reduced peak expiratory flow by an additional -0.5% per ppm of formaldehyde. However, the short-term exposure effect was diminished during the first 4 wk, suggesting at least partial acclimatization. Symptom reporting was also associated with exposure during the previous 2.5 hr, and similar evidence of acclimatization was observed. These results suggest that there are two different time scales of response to formaldehyde, and they emphasize the need for longitudinal studies, characterized by quantitative exposure characterization, and frequent measurements of outcome.