On March 25, 2016, the Occupational Safety and Health Administration (OSHA) of the Department of Labor (DOL) published in the Federal Register new standards governing exposure to respirable crystalline silica in the workplace. Key features of the new crystalline silica standards include the following requirements for employers: protect workers when exposure to respirable crystalline silica exceeds the new permissible exposure limit (PEL) of 50 µg/m 3 (micrograms per cubic meter of air), as an 8-hour time-weighted average (TWA), through the use of engineering controls, or if such controls are not effective, the use of respirators; measure workers' exposure to respirable crystalline silica if such exposure may reach or exceed levels of 25 µg/m 3 as an 8-hour TWA; limit workers' access to areas where they may be exposed to respirable crystalline silica; offer medical exams, including chest x-rays and lung function tests, every 3 years to workers exposed to crystalline silica at or above the level of 25 µg/m 3 as an 8-hour TWA for 30 or more days in a year or to construction workers required to wear respirators for 30 or more days in a year; train workers to limit exposure to respirable crystalline silica; and maintain records of workers' exposure to respirable crystalline silica and employer-provided medical exams. These new standards are to be phased in over a five-year period, beginning June 23, 2017, with different implementation dates for construction, general industry, and hydraulic fracturing (fracking). The standards provide employers in the construction industry an exemption from the PEL and requirement to measure employee exposure to crystalline silica if these employers follow the engineering controls and work practices of the new standards, as outlined in Table 1 of the new standards. For example, if a stationary masonry saw is used in construction, the employer is exempt from the PEL and requirement to measure silica exposure if the following controls and practices are used: Use saw equipped with integrated water delivery system that continuously feeds water to the blade. Operate and maintain tool in accordance with manufacturer's instructions to minimize dust emissions. Crystalline silica is a compound found in the earth's crust. It is a component of soil, sand, and other natural materials. The three most common forms of crystalline silica are quartz, cristobalite, and tridymite. Crystalline silica in dust commonly occurs when workers cut, saw, grind, drill, or crush materials such as glass, stone, rock, concrete, brick, or industrial sand. Exposure also occurs when industrial sand is used in abrasive operations, such as sandblasting, and in the hydraulic fracturing process. The National Institute for Occupational Safety and Health (NIOSH) estimates that 1.7 million workers are exposed to crystalline silica in the workplace. However, NIOSH's estimates are based on 1986 data, which were published in 1991. In the preamble to its new crystalline silica standards, OSHA estimates that more than 2.3 million workers are potentially exposed to crystalline silica in the workplace, including more than 2 million workers in the construction industry. Crystalline silica particles can be 100 times smaller than normal sand particles. Because of their small size, these particles can easily enter the human respiratory system. The International Agency for Research on Cancer (IARC) and the Department of Health and Human Services (HHS) National Toxicology Program has identified crystalline silica as a human carcinogen. The respiration of crystalline silica has been associated with the incurable disease silicosis and other respiratory diseases, such as pulmonary tuberculosis and lung cancer; auto-immune diseases, such as scleroderma, rheumatoid arthritis, and lupus; and renal disease and renal changes. The health effects of crystalline silica and the link between occupational exposure to crystalline silica and silicosis and other diseases have been known since the beginning of the 20 th century, when cases of "consumption" and "phthisis" were documented among miners, stonecutters, glass workers, and other workers in the United States and other countries. In 1931, several hundred workers died of acute silicosis after being exposed to silica during the construction of Union Carbide and Carbon Corporation's Hawk's Nest Tunnel in Gauley Bridge, WV, making this exposure one of the deadliest single incidents of occupational disease in American history. The federal government, under the provisions of the Energy Employees Occupational Illness Compensation Program Act (EEOICPA), currently provides a $150,000 cash benefit and health benefits to workers, or their survivors, who contracted chronic silicosis as a result of digging tunnels in Alaska and Nevada used for the underground testing of atomic weapons. In the preambles to its Notice of Proposed Rulemaking (NPRM) and Final Rule, OSHA lays out a detailed rationale for the new crystalline silica standards. OSHA claims that based on an extensive review of existing literature and research that identifies links between exposure to crystalline silica and various medical conditions, including silicosis, cancers, renal conditions, and other diseases, the new standards will prevent more than 600 silica-related deaths each year and reduce monetarized benefits by reducing mortality and morbidity, which far exceed projected costs of compliance. In preparing its new crystalline silica standards, OSHA conducted a Preliminary Quantitative Risk Assessment and Final Quantitative Risk Assessment. Both assessments consisted of an extensive review of published literature and research on the health effects of occupational exposure to crystalline silica. OSHA performed these risk assessments in compliance with Section 6(b)(5) of the Occupational Safety and Health Act (OSH Act), which states, in part Development of standards under this subsection shall be based upon research, demonstrations, experiments, and such other information as may be appropriate. In addition to the attainment of the highest degree of health and safety protection for the employee, other considerations shall be the latest available scientific data in the field, the feasibility of the standards, and experience gained under this and other health and safety laws.... Before the Preliminary Quantitative Risk Assessment, a draft health effects review document was subject to external peer review in accordance with Office of Management and Budget (OMB) guidelines. As a result of the Final Quantitative Risk Assessment, OSHA concludes in the preamble to its Final Rule: [T]here is convincing evidence that inhalation exposure to respirable crystalline silica increases the risk of a variety of adverse health effects, including silicosis, NMRD [non-malignant respiratory disease] (such as chronic bronchitis and emphysema), lung cancer, kidney disease, immunological effects, and infectious tuberculosis (TB). The new standards set a uniform PEL of 50 µg/m 3 measured as an 8-hour TWA. If workers are exposed to crystalline silica above the PEL, they must be protected through engineering controls, such as using water to control dust generated by a work process or respirators provided by the employer. Because the PEL is measured as an 8-hour TWA, a worker can be exposed to levels above the PEL periodically during the work day, provided that his or her average exposure over 8 hours does not exceed the 50 µg/m 3 . Prior to the promulgation of the new crystalline silica standards, the OSHA occupational safety and health standards (the old standards) did not include a universal PEL for all industries and types of crystalline silica. In addition, the PELs in the old standards, as published in the Code of Federal Regulations (C.F.R. ), are not directly comparable to the new PELs. The PELs in the old standards are expressed as a formula of volume of crystalline silica per cubic meter of air, divided by the percentage of silicon dioxide (SiO 2 ); or as millions of particles per cubic foot of air, divided by the percentage of SiO 2 . In its NPRM on the new standards, OSHA reports that the particle-count methodology used to determine the number of particles per cubic foot of air is obsolete. In its NPRM, OSHA also provides the following estimates of the old-standard PELs expressed using the new methodology of µg/m 3 , measured as an 8-hour TWA: quartz in general industry: 100 µg/m 3 ; quartz in construction industry: 250 µg/m 3 ; quartz in shipyard industry: 250 µg/m 3 ; cristobalite in all industries: 50 µg/m 3 ; and tridymite in all industries: 50 µg/m 3 . The old-standard PELs trace their history to a report from the U.S. Public Health Service in 1929, which examined exposure to silica among workers in the granite-cutting industry in Barre, VT. The report recommended an exposure limit of between 10 million and 20 million particles per cubic foot (mppcf) for dust containing approximately 35% free silica (which includes crystalline silica) in the form of quartz and stated that this level could be "obtained by the use of economically practicable ventilating devices applied to the source of the dust." A review of the report stated It should be pointed out that the limit established was not found to prevent the occurrence of silicosis. It was found, however, that there seemed to be no particular liability to pulmonary tuberculosis where the concentration of dust was within this limit. Section 6(a) of the OSH Act required OSHA to convert existing federal occupational safety and health standards and national consensus standards into OSHA standards within two years of enactment of the OSH Act. In 1971, OSHA's original PELs for crystalline silica were promulgated based on the existing PELs provided in regulations implementing the Walsh-Healey Public Contracts Act of 1936, which established certain standards for federal contractors. The Walsh-Healey regulations were based on the 1968 Threshold Limit Values (TLVs) established by the American Conference of Governmental Industrial Hygienists (ACGIH).