ASBESTOS ON THE RAILROAD What to know: Locomotives often contained asbestos, usually in the form of pipe wrapping. During one remediation in 1991, technicians found cloth-like wrapping around an air compressor pipe that consisted of 85-90 percent asbestos. Seven years later, during another remediation, technicians found an average of 75 linear feet of asbestos per locomotive, with one unit having 250 linear feet of asbestos material. Remediators during the 1990s and early 2000’s found asbestos on exhaust pipes, manifold pipes, governor lines, cab heater lines and even water lines. Asbestos was also found wherever there were steam lines, such as beneath passenger and dining cars. Rail workers whose job was to check lines beneath such cars could potentially come into contact with material from asbestos-wrapped steam lines. Asbestos-containing materials (ACM) were also identified in rail yards, in boiler buildings and associated steam pipes as well as part of roofing materials, floor tile and even so-called “pipe mud” or caulking compound. One remediation report noted that “pipe-fitting mud” contained 2 percent amosite, a form of asbestos. An inspection report from the 1990s noted that a signal shack built in 1980 contained transite (concrete building material mixed with asbestos) wallboard consisting of 29.8 percent chrysotile. Additionally:

1. Exposure to asbestos causes a chronic, (currently) incurable disease called asbestosis which involves scarring of the lung tissue. The latency period between exposure to asbestos and onset of asbestosis can range between 10 and 40 years.
2.  Exposure to asbestos can also cause lung cancer.
3. According to OSHA, the current maximum allowable exposure limit, 0.1 fiber (>5microns)/cc results in an excess cancer risk of 3.4 per 1,000 workers and a 20-year exposure risk of 2.3 per 1,000 workers.
4. There are several kinds of asbestos, but chrysotile is most commonly used on the railroad. Some pipe wrapping materials used on the railroad are composed of both (a) chrysotile, sometimes called white asbestos, and (b) amosite, sometimes called brown asbestos.
5. Chrysotile asbestos is slightly soluble in the lung and is thought to disintegrate over time. Other forms of asbestos, like amosite, are not soluble in the lung.
6. Airborne asbestos can float in the air for many hours, depending on length of the fibers.

Discussion: Asbestos Asbestos is not a single substance, but rather several–all minerals, and all toxic to the respiratory system.  Asbestos can be divided into two large groups: amphibole and serpentine. Amphibole Asbestos The amphibole asbestos types of industrial importance are crocidolite, tremolite, amosite, actinolite and anthophyllite. Scanning electron microscopy reveals that most amphibole asbestos fibers are between 0.03 to less than 5 microns in length.¹ Amphibole asbestos fibers are not particularly soluble in the lung and can persist many years after the initial exposure.² As Ann Wylie noted in her chapter in Asbestos and Mesothelioma: Current Cancer Research, “Surface area of amphibole-asbestos used in manufacturing is quite high, approaching 90,000 square centimeters per gram as measured by nitrogen absorption, while unprocessed ore may have a surface area an order of magnitude smaller. After ore is mined, it is normally “fiberized” in the mill to differing degrees, depending on its intended use. Fiberization liberates fibrils, affects fiber size, and increases surface area. In comparing lung fibrosis after exposure to Cape crocidolite, Hammersley crocidolite, amosite and Paakila anthophyllite-asbestos, Lippman and Timbrell³ have concluded that it is the surface area of inhaled fibers that controls the degree of lung fibrosis, not mineral type per se, so surface area is an important variable in characterizing asbestos.”⁴ The importance of surface area, however, is clearly at odds with OSHA’s position that fiber length is the only criteria for asbestos sampling and analysis. If Lippmann and Timbrell are correct, then an exposure to a dense cloud of asbestos consisting only of fibers less than 4 microns in length would result in an extremely high surface area but would be in compliance with OSHA’s asbestos standard–which requires fibers to be five microns before they can be counted. Serpentine Asbestos There are several types of asbestiform minerals in the serpentine group, but the one most commonly used in industry is chrysotile. Chrysotile fibers appear under a light microscope as singular objects but are actually composed of and often surrounded by even smaller fibers called fibrils. Fibrils, in turn, when viewed with a transmission electron microscope, resemble bundles of soda straws. These straw-like tubes are extremely small–on the order of 70-80 angstroms (Å) in diameter (one Angstrom is equal to 0.1 nanometer). The fibrils of chrysotile are generally 220-270 Å (22-27 nanometers) in diameter but can be as wide as 650 Å (65 nanometers)⁵. Chrysotile fibers and fibrils are hydrophilic, and in the lung will tend to dissolve with time ⁶ OSHA’s asbestos standard requires that only fibers 5 microns or larger with a length/width aspect greater than 3:1 are counted. But, in fact in any distribution of chrysotile fibers there are far more smaller fibers than larger ones. In a sample taken from the Coalinga Deposit in California, the range of lengths was between a tenth of a micron (0.1μ) and 45 μ with 92 percent of the fibers having a length less than 5 microns⁷. Had this sample been suspended in air and sampled to determine compliance with the OSHA asbestos standard, the analyst would have had to reject all but 8 percent of the fibers. Airborne asbestos is generally composed of a far greater number of smaller particles than larger particles. It is not generally well-known or appreciated that particulate sizes in air are not distributed normally, i.e. as with a bell-shaped curve, but usually follow what is called a log-normal distribution. That is, there are usually far more smaller particles in the air than there are larger ones. In other words, for every single particle seen on an analysis grid, there are likely many small fibrils that cannot be seen, even with electron microscopes. And the greater the number of smaller particles, the greater the surface area. Recall Wylie’s observation that one gram of milled amosite asbestos could result in a surface area of 90,000 square centimeters–an area equal to 96.875 square feet. It follows that the surface area of one pound of refined amosite would theoretically equal (453.52 x 96.875 sq ft) 43981.25 square feet, or a square 209.7 ft on a side. And, again, if each of the fibrils were smaller than 5 microns in length, the dispersed cloud would not be in violation of OSHA’s asbestos standard. However, this does not necessarily mean that particles shorter than 5 microns in length, are not toxic to the lungs. The NIOSH 7400 method used PCM, or phase contrast microscopy ⁸. The method required counting only particles longer than 5 microns with an aspect ratio of at least 3:1. Not only does this method exclude smaller fibers, by using light microscopy, the technician will simply fail to see smaller particles below the resolution of the microscope. A paper published in 1984 by A.P. Rood and R.R. Streeter studied asbestos fiber samples from an asbestos textile plant. As usual, the airborne asbestos fibers were distributed lognormally (where there are a greater number of smaller fibers in the distribution than larger ones) with the median lengths and diameters 1.6 microns and 0.08 microns respectively. Their conclusions: “The results indicate that about 60% of fibers would not be seen by scanning electron microscopy, under the usual conditions, and an even larger proportion would be missed by optical microscopy. For fibers longer than 5 microns, then, about 70% of fibers would be seen by the scanning electron microscope. An optical microscope with a resolution of 0.3 microns would see approximately one quarter of all fibers greater than this length.” In their paper, Rood and Streeter noted that a “good, correctly adjusted” phase contrast optical microscope may have a detection limit of 0.15 microns, but under normal operating conditions, the detection limit is not so low. Importantly, they also reported: • “About 60% of all fibers had sizes below the detection limit of the usual scanning electron microscope method and about 93% had sizes below the detection limit of the phase contrast optical microscope; and, • “For fibers longer than 5 microns, then about 26% of fibers were of sizes below the detection limit of the usual scanning electron microscope technique, and 75% had sizes below the detection limit of the phase contrast optical microscope.”⁹. Asbestos fibers can float in the air literally for days. The smaller the particle or fiber, the longer it will float in air. For a fiber’s propensity to remain airborne, the diameter is more important than the length. Authors of the book Environmental Measurement Methods for Asbestos note: “. . .the fastest falling speed for a single fibril of chrysotile with a diameter of 0.5 microns is approximately 0.0001 centimeters per second. (Within 20 and 30 minutes) in still air, a single fibril could fall a distance of less than 2 millimeters in this period of time. The fastest time, in still air, for a single fibril to fall the 40 centimeters from the test sample to the collection surface is approximately 110 hours.^{10, 11} What this means, if workers shake the asbestos dust off a worn brake pad at 8:00 am on a Monday, some of those fibers will theoretically still be floating in the air by 8:00 pm Friday. In practice, by that time these fibers will travel with air currents to other parts of the shop, far from the original source. Stokes diameter equations can be solved using appropriate resources found online¹². Inhalation rates affect exposure In 1980, when the OSHA PEL was 1 fiber/cc, George A. Peters and Barbara J. Peters, authors of the Sourcebook on Asbestos Diseases¹³ wrote: “Even at 1 fiber/cc level, this corresponds to about one million fibers per cubic meter of air. Even a resting young man will ventilate his lungs with about 6000 ml of air per minute and thus will breathe in approximately 2,880,000 fibers in one 8-hour workday. Thus, a man at work will breathe into his lungs a rather substantial number of fibers, even in a relatively short duration exposure, at exposure levels within the permissible or allowable limits¹⁴.” The above passage highlights an unfortunate truth about asbestos: like most airborne particulates there are generally a far greater number of smaller fibers than there are larger ones. That is, as noted earlier in this section, the relative sizes of the fibers or particles are distributed log-normally.^{15, 16} The shape of a lognormal distribution differs from the normal distribution (the Gaussian or “bell-shaped curve) in that the highest point of the curve is not in the center, but rather on the left part of the graph. Additionally, there is a long tail to the right. This reflects the much larger fraction of smaller particles in comparison to the smaller fraction (and thus number) of large particles. Additionally, the distribution’s long tail tells us that there is a very large range of particle sizes, often spanning several orders of magnitude. That is, there may be small particles on the left side of the graph that might be 1/1,000th the size of some of the larger particles on the far-right side of the graph.¹⁷ The Peters’ estimate in their 1980 book likely assumes a tidal volume (normal breath, relaxed) of 500 ml per inspiration and with 12 inspirations per minute. In fact, breathing rate varies with work effort: as one burns more calories, the greater the respiration rate, and thus the more air introduced into the lungs. This data will be included in this website at a later date. At this point, it is reasonable to ask: what is considered a safe, or at least, an air concentration of asbestos that is found far away from industry? As it turns out, from the early 1970s to the mid-1980s, the EPA contracted with scientists to sample the ambient air around the United States. This is what they found: Ambient Levels Sooner or later, in most cases involving air concentrations of asbestos the issue of ambient levels will come up: what can be considered an ambient level for asbestos fibers in the community breathing air? The answer comes from a 1984 book published by the National Research Council, Committee on Non-occupational Health Risks: Asbestiform Fibers–Non-occupational Health Risks. The book compiled the results of eleven studies where a total of 612 air samples were taken at various sites in the United States. The maximum equivalent median concentration of fibers was only 0.00003 fibers/cc while the maximum equivalent median concentration of asbestos fibers was 0.00405 fibers/cc. That maximum amount was based on 27 air samples taken in U.S. schoolrooms with damaged asbestos surfacing materials. In the United States, asbestos has been used in brakes since 1906. According to Richard A. Lemen, in his 2004 article, “Asbestos in Brakes: Exposure and Risk of Disease”, chrysotile has been used almost exclusively “as the amphibole asbestos type tended to be too harsh and tended to score the brake drums, making them wear much faster.¹⁸¹⁹ of brake wear debris, . . .“demonstrate that 90,000 asbestos fibers per nanogram remain in that dust. Fibers less than 5 micrometers (μg) in length outnumber fibers greater than 5 μg in length by a ratio of 300:1. This translates to approximately 300 billion asbestos fibers greater than 5 μm per gram of wear debris and 90 trillion asbestos fibers less than 5 μg.”²⁰ In his article, Lemen discusses the toxicity of short asbestos fibers: “Any assumption that short fibers, less than 5 microns (μm) in length, are not hazardous cannot be justified based on the available science. Because the analytical method of choice, for regulatory purposes, has been the phase contrast method (PCM) which counts only fibers greater than 5 microns in length, epidemiology studies have been forced to compare doses in their cohorts to fibers greater than 5 microns in length. It must be noted that the PCM analytical method was chosen based on its ability to count fibers only and not on a health effect basis. While PCM has been the international regulatory method for analysis it is not able to detect thin diameter fibers (<0.2μm in diameter), and because of this, it is suggested that transmission electron microscopy (TEM) should be an adjunct to PCM, since the evidence suggests that PCM may underestimate exposures and the health risks as found in the analysis of brake residue (Yeung et al, 1999)²¹. Other asbestos containing materials used by railroads include the following: • Gaskets • Pipe wraps • Transite (asbestos-containing cement) building material including movable walls • Open deck bridges • Pipe units for overhead lines • Roofing materials • Fire curtains • Smoke jacks • Building interiors and exteriors • Ceiling panels • Flooring • Locomotive cab roofs • Fiberglass materials cemented to asbestos cloth • Safety equipment such as gloves • Brake shoes Among the brake shoes used by the railroad up until the early 1980s was the Cobra brand, sold by Railroad Friction Products Corporation (RFPC), a company originally founded in 1954. According to court records in Scholar v. Railroad Friction Products, RFPC was jointly owned by Westinghouse Air Brake Company (“WABCO”) and the Johns-Manville Corporation, which manufactured and sold asbestos products. In 1978, WABCO sold its interest in Railroad Friction Products Corporation to American Standard, Inc. In 1990, however, WABCO purchased American Standard’s interest in Railroad Friction Products, along with Johns-Manville’s interest in 1992. Prior to all of that, Railroad Friction Products Corporation had purchased composition tread brake shoes for railroad cars from Johns-Manville, and sold the brake shoes under the brand name COBRA. From 1959 until 1980, the backing stock of most COBRA brake shoes contained varying amounts of asbestos. In 1980, RFPC officially removed asbestos from the COBRA brake shoes.²² That is not to say, of course, that the COBRA and other asbestos-containing brake shoes were no longer used on rail cars and locomotives after 1980. Asbestos in Locomotives Asbestos has been used as pipe wrap in locomotives. Remediation activity occasionally lists the amount of asbestos removed and from which locations inside particular locomotive models. The true risk of airborne asbestos at the OSHA PEL The OSHA permissible exposure limit is currently 0.1 fiber per cubic centimeter of air averaged over an 8-hour period with an excursion limit of 1.0 fiber per cubic centimeters over a 30-minute period²³. Some people, even some industrial hygienists may believe that 0.1 fiber/cc (and a minimum length of 5 microns) is the regulation, therefore it must be protective. It is not. As OSHA noted in their final rule of June 17, 1986²⁴, the 0.1 fiber/cc limit was chosen because it is, in part “reliably measurable,” and it is “at the limit of feasibility for those workplaces in which asbestos levels are most difficult to control, and an assumption that average exposures will be substantially below the PEL will clearly be unrealistic for such workplaces.”⁵⁰ In fact, OSHA admitted that “the 0.1 f/cc leaves a remaining significant risk.” “The 0.1 f/cc level leaves a remaining significant risk. However, as discussed below, and in earlier documents, OSHA believes this is the practical lower limit of feasibility for measuring asbestos levels reliably. However, the work practices and engineering controls specified. . .for specific operations and required respirator use will in OSHA’s view further reduce the risk.” “OSHA has always considered that a working lifetime risk of death of over 1 per 1000 from occupational causes is significant. This has been consistently upheld by the courts. See the recent discussion in the cadmium preamble 57 FR (Federal Register) 42102, 42204 and the earlier asbestos preambles. “OSHA believes that compliance with these final amendments to reduce the PEL to 0.1 f/cc as a time-weighted average measured over 8 hours will further reduce a significant health risk which existed after imposing a 0.2 f/cc PEL. “OSHA’s risk assessment accompanying the 1986 standard, showed that lowering the TWA PEL from 2 f/cc to 0.2 f/cc reduces the asbestos cancer mortality risk from lifetime exposure from 64 deaths per 1,000 workers to 7 deaths per 1,000 workers. OSHA estimated that the incidence of asbestosis would be 5 cases per 1,000 workers exposed for a working lifetime under the TWA PEL of 0.2 f/cc. Counterpart risk figures for 20 years of exposure are excess cancer risks of 4.5 per 1,000 workers and an estimated asbestosis incidence of 2 cases per 1,000 workers.”⁽²⁶⁾; “OSHA’s risk assessment also showed that reducing exposures to 0.1 f/cc would reduce excess cancer risk to 3.4 per 1,000 workers and a 20-year exposure risk to 2.3 per 1,000 workers. OSHA concludes therefore that reducing the exposure limit to 0.1 f/cc will further reduce significant risk.” NOTE: To request the full document with end notes, use the Contact Form on this website and ask for “Asbestos II doc.” (c)Legis Corp 2025.  All rights reserved.