What to know: Silica is a compound made up of the element silicon and oxygen. The formula for the silica molecule is SiO₂. It makes up approximately 27.7 percent of the earth’s crust. Quartz contains between 90-95 percent crystalline silica. Sand also contains silica, as well as other types of materials, such as igneous rock and shell fragments.¹ Silica also makes up about 28 percent of the mineral content of soil. Common road dust can contain between 1 and 30 percent of silica, however the composition of road dust depends on the geographic location of the road itself. Silica is not the only toxic material in road dust. Other potentially toxic elements have been identified in road dust studies from Barcelona, Spain. ² In a 2023 study by Navarro-Ciurana, Corbella and Merono ³,the most common potentially toxic element found was barium. In addition to barium and silicates, the researchers also found chromium, arsenic, lead, cobalt and nickel in the Barcelona road dust. Silica is found in the railroad environment.  Every locomotive uses silica-containing sand to gain traction on rails.  While ballast composition varies by geographic location, most ballast contains significant amounts of silica–which means that there is a potential for silica exposure to maintenance-of-way crews. Silica exposure can damage the lungs Exposure to silica has long been known to cause lung damage. The May 29, 1971 edition of the Federal Register⁴ includes respirable crystalline silica on OSHA’s very first list of Threshold Limit Values of Airborne Contaminants.”⁵ In the human lung, crystalline silica particles causes both injury to epithelial tissue as well as macrophage activation, which in turn leads to the eventual development of such conditions as chronic silicosis, emphysema, obstructive airways disease, and lymph node fibrosis. It wasn’t until March 25, 2016 that the OSHA standard for silica was lowered to 50 micrograms of silica per cubic meter of air for an 8-hour Time Weighted Average, while the action level is 25 micrograms/M3 for an 8 hr Time-Weighted Average.⁶⁶ The ACGIH (American Conference of Governmental Industrial Hygienists) Threshold Limit Concentration is 25 micrograms per cubic meter of air. In the OSHA Final Rule for Silica (2016) the agency notes: “The Agency considers the level of risk remaining at the new PEL (50 micrograms/cubic meter) to be significant. However, based on the evidence evaluated during the rulemaking process, OSHA has determined a PEL of 50 microgram/cubic meter is appropriate because it is the lowest level feasible for all affected industries.”⁷ Environmental and workplace silica exposure and lung cancer In the aforementioned Final Rule on silica exposure, OSHA noted: “The evidence in the record for this rulemaking indicates that workers exposure to respirable crystalline silica are at increased risk of developing silicosis and other non-malignant respiratory diseases, lung cancer, and kidney disease.⁸” Many peer-reviewed studies have shown a link between silica exposure an lung cancer. As David Goldsmith, PhD testified during the 2015 OSHA hearings regarding reducing the PEL for crystalline silica: “There have been literally thousands of research studies on exposure to crystalline silica in the past 30 years. Almost every study tells the occupational research community that workers need better protection to prevent severe chronic respiratory diseases, including lung cancer and other diseases in the future. What OSHA is proposing to do in revising the workplace standard for silica seems to be a rational response to the accumulation of published evidence.”⁹ Risk estimates In the Final Rule for Silica, OSHA included this short paragraph regarding an early estimate of risk of a 50 microgram silica Permissible Exposure Limit: “Charles Gordon, a retired occupational safety and health attorney, commented that the revised PEL (permissible exposure limit) ‘leaves a remaining risk of 97 deaths per 1,000 workers from silicosis, lung cancer, and renal disease combined.”¹⁰ However, one would have to read another 356 pages before finding OSHA’s official risk estimates, the first set of risk values based on a 45-year exposure at the previous PEL, and the second based on the new (50-microgram) PEL published in 2016. “After considering the evidence in the rulemaking record, OSHA is establishing a PEL of 50 micrograms per cubic meter. OSHA’s examination of health effects evidence, discussed in Section V, Health Effects, and Section VI, Final Quantitative Risk Assessment and Significance of Risk, confirms the Agency’s preliminary conclusion that exposure to respirable crystalline silica at the previous PELs results in a significant risk of material health impairment to exposed workers, and that compliance with the revised PEL will substantially reduce that risk. OSHA’s Quantitative Risk Assessment indicates that a 45-year exposure to respirable crystalline silica at the PRECEDING general industry PEL would lead to between 11 and 54 excess deaths from lung cancer, 11 deaths from silicosis, 85 deaths from all forms of non-malignant respiratory disease (including silicosis as well as other diseases such as chronic bronchitis and emphysema), and 39 deaths from renal disease per 1000 workers. “Exposures at the preceding construction and shipyard PEL would result in even higher levels of risk. “As discussed in Section VII of this preamble, Summary of the Final Economic Analysis and Final Regulatory Flexibility Analysis, these results clearly represent a risk of material impairment of health that is significant with the context of the “Benzene” decision (Indus. Union Dep’t AFL-CIO v. Am. Petroleum Inst., 448 U.S. 607 (1980). OSHA has determined that lowering the PEL to 50 micrograms/meter cubed will reduce the lifetime excess risk of death per 1000 workers to between 5 and 23 deaths from lung cancer, 7 deaths from silicosis, 44 deaths from non-malignant respiratory disease, and 32 deaths from renal disease. “The Agency considers the level of risk remaining at the revised PEL to be significant. However, based on the evidence evaluated during the rulemaking process, OSHA has determined a PEL of 50 micrograms/m3 is appropriate because it is the lowest level feasible. As discussed in Chapters IV and VI of Final Economic Analysis and Final Regulatory Flexibility Analysis (FEA) and summarized in Section VII of this preamble, the PEL is technologically and economically feasible for all industry sectors, although it will be a technological challenge for several affected sectors and will require the use of respirators for certain job categories and tasks¹¹.” History Silica-associated illness has a long history in America. Lung disease was known to be associated with so-called hard rock mining as early as 1913. It was then that the U.S. Public Health Service and the Bureau of Mines began a study of 720 miners only to find that 60 percent of them were suffering from lung diseases directly related to exposure to rock dust.^{12, 13} Despite this, very little was done to prevent workers from being exposed to dust from mining and rock crushing operations. In March 1930, shortly after the Great Depression began, the Kanawha and New River Power Company began a project to divert West Virginia’s New River to supply hydroelectric power to a plant in Alloy, West Virginia. However, the three-mile-wide Gauley Mountain stood in the way. The engineers working for the contractor, Rhinehart and Dennis decided that, with enough workers, they could cut a tunnel through the mountain to the other side. Additional work included a dam that would divert the river into the new tunnel, after which it would re-enter the river near Gauley Bridge, W. VA.^{14, 15} The mountain consisted mostly of quartz in the form of sandstone. Three-thousand men–three-quarters of them black, worked ten to fifteen-hour shifts to cut drill and blast the tunnel through the mountain. Members of management wore respirators while checking the progress of the project, but no respirators were afforded the men removing the quartz rock. Several years later, in 1936, former workers at Hawks Nest testified to Congress that they were not afforded respirators or breaks, and were forced to work at gunpoint.¹⁶ The Hawk’s Nest Tunnel, projected to take four years, was completed in only a year and a half–18 months. However, many of the Hawk’s Nest workers became ill from what was likely silicosis. The historical site lists only 109 deaths, however, a Congressional hearing estimated the death toll at 476.¹⁷ Researcher Patricia Spangler, author of “The Hawks Nest Tunnel” places the estimate between 700-1000 workers.^18< Pneumoconiosis due to asbestos and silica was known by the Railroad as early as 1932. In the spring of 1932 the American Railway Association Medical and Surgical Section met to discuss health problems encountered among railroad workers. At the meeting, they discussed dust as an “industrial hazard that demands attention and causes pneumoconiosis.”¹⁹ Meeting the next year, the same group discussed “the subject of dust as an industrial hazard. . .the subject cannot be considered as inherently as a railroad problem; however, it may arise in connection with various lines of work and when it does so, presents a problem which demands attention. . .use of water to wet down the dust at the point of origin, or by forced ventilation to remove the dust particles. In the event that neither of these methods is practicable, respirators should be made available to employees who are required to work in the presence of the dust.²⁰” In 1935, at the 15th meeting of the Medical and Surgical section both silicosis and asbestos were discussed: “Pneumoconiosis is a condition that may be caused by any kind of dust entering the lung; but we as railroad surgeons are undoubtedly more interested in silicosis and asbestosis than other types. . .asbestosis is caused by breathing fine fibres of asbestos which consists of magnesium calcium silicate. Asbestosis is not a common condition but it causes extensive pulmonary fibrosis and takes on a more rapid course than does silicosis.²¹” Is there a toxicity difference between aged and freshly-crushed silica? Between 1988 and 2011 there were several reports evaluating the importance of reactive oxygen species on the surfaces of freshly-crushed silica. Two examples follow: In Jan 1988, Val Valyathan, Xianglin Shi, Nar Dalal, William Irr and Vincent Castranova reported in The American Review of Respiratory Disease (Vol 138 Issue 5)²² that freshly-fractured silica exhibits different surface characteristics and also has a distinct biologic reactivity different than that of aged silica. The researchers proposed that this increased reactivity may result in an enhanced lung injury. According to the abstract, grinding silica produces approximately 10¹⁸ , or (1,000,000,000,000,000,000) Silicon and Si-O radicals on the particulate surface. According to the researchers, these radicals when remaining in silica have a half-life of about thirty hours. When stored in an aqueous media, the ability of the silica to generate -OH radicals decreases significantly with a half-life between a few minutes and twenty hours. The researchers concluded that freshly-ground silica was, therefore more cytotoxic than aged silica. In 2002, Dale Porter et al. ²³reported that exposure of rat lungs to freshly fractured silica “causes greater generation of reactive oxygen species from alveolar macrophages, measured as alveolar macrophage chemiluminescence, in comparison to aged silica, but there is an apparent threshold below which this difference does not occur.” OSHA’s Silica Standard of 2016 In 2016, OSHA reduced the permissible exposure limit to silica to 50 micrograms per cubic meter with an action level of one-half the PEL, or 25 micrograms per cubic meter. The OSHA silica standard, 29 CFR 1910.1053 includes, but is not limited to, the following requirements which may be applicable to Railroads. 1910.1053(c): Permissible exposure limit (PEL). The employer shall ensure that no employee is exposed to an airborne concentration of respirable crystalline silica in excess of 50 μg/m3, calculated as an 8-hour TWA. 1910.1053(d)(1): General. The employer shall assess the exposure of each employee who is or may reasonably be expected to be exposed to respirable crystalline silica at or above the action level in accordance with either the performance option in paragraph (d)(2) or the scheduled monitoring option in paragraph (d)(3) of this section. 1910.1053(d)(3)(i): The employer shall perform initial monitoring to assess the 8-hour TWA exposure for each employee on the basis of one or more personal breathing zone air samples that reflect the exposures of employees on each shift, for each job classification, in each work area. Where several employees perform the same tasks on the same shift and in the same work area, the employer may sample a representative fraction of these employees in order to meet this requirement. In representative sampling, the employer shall sample the employee(s) who are expected to have the highest exposure to respirable crystalline silica. 1910.1053(d)(3)(v): Where the most recent (non-initial) exposure monitoring indicates that employee exposures are below the action level, the employer shall repeat such monitoring within six months of the most recent monitoring until two consecutive measurements, taken 7 or more days apart, are below the action level, at which time the employer may discontinue monitoring for those employees whose exposures are represented by such monitoring, except as otherwise provided in paragraph (d)(4) of this section. 1910.1053(d)(6)(i): Within 15 working days after completing an exposure assessment in accordance with paragraph (d) of this section, the employer shall individually notify each affected employee in writing of the results of that assessment or post the results in an appropriate location accessible to all affected employees. 1910.1053(d)(7)(i): Where air monitoring is performed to comply with the requirements of this section, the employer shall provide affected employees or their designated representatives an opportunity to observe any monitoring of employee exposure to respirable crystalline silica. 1910.1053(e)(1): The employer shall establish a regulated area wherever an employee’s exposure to airborne concentrations of respirable crystalline silica is, or can reasonably be expected to be, in excess of the PEL. 1910.1053(e)(4): Provision of respirators. The employer shall provide each employee and the employee’s designated representative entering a regulated area with an appropriate respirator in accordance with paragraph (g) of this section and shall require each employee and the employee’s designated representative to use the respirator while in a regulated area. 1910.1053(f)(1): Engineering and work practice controls. The employer shall use engineering and work practice controls to reduce and maintain employee exposure to respirable crystalline silica to or below the PEL, unless the employer can demonstrate that such controls are not feasible. Wherever such feasible engineering and work practice controls are not sufficient to reduce employee exposure to or below the PEL, the employer shall nonetheless use them to reduce employee exposure to the lowest feasible level and shall supplement them with the use of respiratory protection that complies with the requirements of paragraph (g) of this section. 1910.1053(f)(2): Written exposure control plan. 1910.1053(f)(2)(i): The employer shall establish and implement a written exposure control plan that contains at least the following elements: 1910.1053(f)(2)(i)(A):  A description of the tasks in the workplace that involve exposure to respirable crystalline silica; 1910.1053(f)(2)(i)(B):  A description of the engineering controls, work practices, and respiratory protection used to limit employee exposure to respirable crystalline silica for each task; and, 1910.1053(f)(2)(i)(C):  A description of the housekeeping measures used to limit employee exposure to respirable crystalline silica. 1910.1053(f)(2)(ii):  The employer shall review and evaluate the effectiveness of the written exposure control plan at least annually and update it as necessary. 1910.1053(f)(2)(iii):  The employer shall make the written exposure control plan readily available for examination and copying, upon request, to each employee covered by this section, their designated representatives, the Assistant Secretary and the Director. 1910.1053(g): Respiratory protection General. Where respiratory protection is required by this section, the employer must provide each employee an appropriate respirator that complies with the requirements of this paragraph and 29 CFR 1910.134. Respiratory protection is required: 1910.1053(g)(1)(i): Where exposures exceed the PEL during periods necessary to install or implement feasible engineering and work practice controls; 1910.1053(g)(1)(ii): Where exposures exceed the PEL during tasks, such as certain maintenance and repair tasks, for which engineering and work practice controls are not feasible; 1910.1053(g)(1)(iii):  During tasks for which an employer has implemented all feasible engineering and work practice controls and such controls are not sufficient to reduce exposures to or below the PEL; and, 1910.1053(g)(1)(iv) During periods when the employee is in a regulated area. 1910.1053(g)(2):  Respiratory protection program. Where respirator use is required by this section, the employer shall institute a respiratory protection program in accordance with 29 CFR 1910.134. Medical surveillance -1910.1053(i)(1): General. 1910.1053(i)(1)(i):  The employer shall make medical surveillance available at no cost to the employee, and at a reasonable time and place, for each employee who will be occupationally exposed to respirable crystalline silica at or above the action level for 30 or more days per year. 1910.1053(i)(1)(ii): The employer shall ensure that all medical examinations and procedures required by this section are performed by a PLHCP (physician or other licensed health care professional) as defined in paragraph (b) of this section. 1910.1053(i)(5): PLHCP’s written medical report for the employee. The employer shall ensure that the PLHCP explains to the employee the results of the medical examination and provides each employee with a written medical report within 30 days of each medical examination performed. The written report shall contain: 1910.1053(i)(5)(i):  A statement indicating the results of the medical examination, including any medical condition(s) that would place the employee at increased risk of material impairment to health from exposure to respirable crystalline silica and any medical conditions that require further evaluation or treatment; 1910.1053(i)(5)(ii):  Any recommended limitations on the employee’s use of respirators; 1910.1053(i)(5)(iii) Any recommended limitations on the employee’s exposure to respirable crystalline silica; and, 1910.1053(i)(5)(iv): A statement that the employee should be examined by a specialist (pursuant to paragraph (i)(7) of this section) if the chest X-ray provided in accordance with this section is classified as 1/0 or higher by the B Reader, or if referral to a specialist is otherwise deemed appropriate by the PLHCP. 1910.1053(j)(1): Hazard communication. The employer shall include respirable crystalline silica in the program established to comply with the hazard communication standard (HCS) (29 CFR 1910.1200). The employer shall ensure that each employee has access to labels on containers of crystalline silica and safety data sheets, and is trained in accordance with the provisions of HCS and paragraph (j)(3) of this section. The employer shall ensure that at least the following hazards are addressed: Cancer, lung effects, immune system effects, and kidney effects. 1910.1053(j)(2): Signs. The employer shall post signs at all entrances to regulated areas that bear the following legend: DANGER RESPIRABLE CRYSTALLINE SILICA MAY CAUSE CANCER CAUSES DAMAGE TO LUNGS WEAR RESPIRATORY PROTECTION IN THIS AREA AUTHORIZED PERSONNEL ONLY 1910.1053(j)(3): Employee information and training. 1910.1053(j)(3)(i): The employer shall ensure that each employee covered by this section can demonstrate knowledge and understanding of at least the following: 1910.1053(j)(3)(i)(A):The health hazards associated with exposure to respirable crystalline silica; 1910.1053(j)(3)(i)(B): Specific tasks in the workplace that could result in exposure to respirable crystalline silica; 1910.1053(j)(3)(i)(C):Specific measures the employer has implemented to protect employees from exposure to respirable crystalline silica, including engineering controls, work practices, and respirators to be used; 1910.1053(j)(3)(i)(D): The contents of this section; and 1910.1053(j)(3)(i)(E): The purpose and a description of the medical surveillance program required by paragraph (i) of this section. 1910.1053(j)(3)(ii): The employer shall make a copy of this section readily available without cost to each employee covered by this section. Recordkeeping- 1910.1053(k)(1) Air monitoring data. 1910.1053(k)(1)(i) The employer shall make and maintain an accurate record of all exposure measurements taken to assess employee exposure to respirable crystalline silica, as prescribed in paragraph (d) of this section. 1910.1053(k)(1)(ii) This record shall include at least the following information: 1910.1053(k)(1)(ii)(A) The date of measurement for each sample taken; 1910.1053(k)(1)(ii)(B) The task monitored; 1910.1053(k)(1)(ii)(C) Sampling and analytical methods used; 1910.1053(k)(1)(ii)(D) Number, duration, and results of samples taken; 1910.1053(k)(1)(ii)(E) Identity of the laboratory that performed the analysis; 1910.1053(k)(1)(ii)(F) Type of personal protective equipment, such as respirators, worn by the employees monitored; and, 1910.1053(k)(1)(ii)(G) Name and job classification of all employees represented by the monitoring, indicating which employees were actually monitored. 1910.1053(k)(1)(iii) The employer shall ensure that exposure records are maintained and made available in accordance with 29 CFR 1910.1020. 1910.1053(k)(2) Objective data. 1910.1053(k)(2)(i) The employer shall make and maintain an accurate record of all objective data relied upon to comply with the requirements of this section. 1910.1053(k)(2)(ii) This record shall include at least the following information: 1910.1053(k)(2)(ii)(A) The crystalline silica-containing material in question; 1910.1053(k)(2)(ii)(B) The source of the objective data; 1910.1053(k)(2)(ii)(C) The testing protocol and results of testing; 1910.1053(k)(2)(ii)(D) A description of the process, task, or activity on which the objective data were based; and, 1910.1053(k)(2)(ii)(E) Other data relevant to the process, task, activity, material, or exposures on which the objective data were based. 1910.1053(k)(2)(iii) The employer shall ensure that objective data are maintained and made available in accordance with 29 CFR 1910.1020. 1910.1053(k)(3) Medical surveillance. 1910.1053(k)(3)(i) The employer shall make and maintain an accurate record for each employee covered by medical surveillance under paragraph (i) of this section. 1910.1053(k)(3)(ii) The record shall include the following information about the employee: 1910.1053(k)(3)(ii)(A) Name; 1910.1053(k)(3)(ii)(B) A copy of the PLHCPs’ and specialists’ written medical opinions; and, 1910.1053(k)(3)(ii)(C) A copy of the information provided to the PLHCPs and specialists. 1910.1053(k)(3)(iii) The employer shall ensure that medical records are maintained and made available in accordance with 29 CFR 1910.1020. 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