Discriminant analysis of amphiboles: Additional considerations.

Amphibole minerals are found throughout nature and could pose a respiratory hazard if these exist in the asbestiform growth habit. Though amphibole asbestos has not been used in commercial products as an added material for more than 30 years, these minerals could exist in other materials as trace contaminants as well as occurring in mines and earth-moving environments. It is necessary, then, that the asbestiform amphibole minerals be properly identified in order to appropriately use health-protective measures. Recent analyses of various amphibole data sets have been used to derive a discriminant function that can be used to differentiate asbestiform amphibole from non-asbestiform amphibole minerals. This paper expands on this function and examines the validity of the procedure for different size fractions of minerals. This analysis suggests that the derived function is appropriate for fibers 10 µm and longer. For fibers shorter than 10 µm, the data suggest that a broader acceptance limit may be needed. The data also suggest that current analytical procedures may require some adjustment to provide more accurate details on the widths of fibers. With additional samples, the accuracy of the discriminate function can be improved by calculating functions for each mineral.

Elongate mineral particles (EMP) characteristics and mesothelioma: Summary and resolution for session I of the Monticello II conference.

The summary contains a consensus opinion regarding the current state of the science about the dimensions of Elongate Mineral Particles (EMPs) as a factor impacting their carcinogenicity.

Identification and analysis of ambient EMPs.

Mineral particles have long been observed in the ambient air and for >40 years, samples of these airborne particulate have been collected in attempt to identify and quantify the amount of asbestos particles in the air. For most of this time, regulated asbestos particles (in the shape of fibers) were the target for these analyses. However, since the turn of the century, more emphasis has been placed on finding and identifying elongate mineral particles (EMPs). For EMPs (particularly serpentine and amphibole minerals), these airborne particles have generally been associated with industrial activities and were reported as "asbestos". Recent monitoring around construction activities involving earth moving have reported concentrations of different mineral particles at sites of varying distance from the activity. The location of detected ambient elongate mineral particles (EMPs) is similar to the locations of soils that also contain EMPs. This close association indicates the necessity for proper mineral identification and valid morphological characterization to allow for source identification. Unfortunately, there continues to be problems with mineral identifications in many studies, regardless of the morphological habit of the particle. This paper addresses the issue of proper mineral identification in ambient air samples.

Asbestos exposures of mechanics performing clutch service on motor vehicles.

A study was conducted to assess historical asbestos exposures of mechanics performing clutch service on motor vehicles. For most of the 20th century, friction components used in brakes and manual transmission clutches contained approximately 25-60% chrysotile asbestos. Since the late 1960s, asbestos exposure assessment studies conducted on mechanics performing brake service have frequently reported levels below the current OSHA permissible exposure limit (PEL) of 0.1 fiber/cc (flcc). Although there is a robust asbestos exposure data set for mechanics performing brake service, there are almost no data for mechanics removing and replacing clutches in manual transmission vehicles. Personal and area airborne asbestos samples were collected during the removal of asbestos-containing clutches from 15 manual transmissions obtained from salvage facilities by an experienced mechanic. Clutch plates and debris were analyzed for asbestos using EPA and ISO published analytical methods. More than 100 personal and area air samples were collected and analyzed for asbestos fibers using NIOSH methods 7400 and 7402. A separate study involved a telephone survey of 16 automotive mechanics who began work prior to 1975. The mechanics were asked about the duration, frequency, and methods used to perform clutch service. Wear debris in the bell housing surrounding clutches had an average of 0.1% chrysotile asbestos by weight, a value consistent with similar reports of brake debris. Asbestos air sampling data collected averaged 0.047 flcc. Mechanics participating in the telephone survey indicated that clutch service was performed infrequently, the entire clutch assembly was normally replaced, and there was no need to otherwise handle the asbestos-containing clutch plates. These mechanics also confirmed that wet methods were most frequently used to clean debris from the bell housing. Combining the asbestos exposure that occurred when mechanics performed clutch service, along with the duration and frequency of this task, the incremental contribution of this task to mechanics' 8-hr time-weighted average (TWA) asbestos exposures was 0.0016 flcc. Using the range of data inputs that were obtained, the authors calculated a range of TWA exposures of 3.75 x 10(-5) flcc to 0.03 flcc. The mean value of 0.0016 flcc is below background levels of asbestos that have been reported in garages during this time and below the current OSHA PEL of 0.1 flcc.

Airborne asbestos concentration from brake changing does not exceed permissible exposure limit.

The use in the past, and to a lesser extent today, of chrysotile asbestos in automobile brake systems causes health concerns among professional mechanics. Therefore, we conducted four separate tests in order to evaluate an auto mechanic's exposure to airborne asbestos fibers while performing routine brake maintenance. Four nearly identical automobiles from 1960s having four wheel drum brakes were used. Each automobile was fitted with new replacement asbestos-containing brake shoes and then driven over a predetermined public road course for about 2253 km. Then, each car was separately brought into a repair facility; the brakes removed and replaced with new asbestos-containing shoes. The test conditions, methods, and tools were as commonly used during the 1960s. The mechanic was experienced in brake maintenance, having worked in the automobile repair profession beginning in the 1960s. Effects of three independent variables, e.g., filing, sanding, and arc grinding of the replacement brake shoe elements, were tested. Personal and area air samples were collected and analyzed for the presence of fibers, asbestos fibers, total dust, and respirable dust. The results indicated a presence in the air of only chrysotile asbestos and an absence of other types of asbestos. Airborne chrysotile fiber exposures for each test remained below currently applicable limit of 0.1 fiber/ml (eight-hour time-weighted average).