- OSHA regulates all aspects of worker health and safety, including exposure to hazardous dust and fumes. Companies in the mining industry must meet health and safety standards under OSHA’s General Duty Clause as well as specific standards for permissible exposure levels (PELs) for different types of dust and fumes. Mining falls under the General Industry category for OSHA.
- EPA regulates environmental emissions for the mining industry, which includes quarrying, open-pit mining, surface mining and underground mining for metal and nonmetallic mineral mining, along with processing activities such as crushing, screening and washing. Mines must follow EPA Clean Air regulations for PM10 and PM 2.5 dust.
- MSHA provides additional regulation, oversight and enforcement of worker health and safety and environmental protections for the mining industry.
Permissible Exposure Limits for Mining and Mineral Processing Dust
OSHA has issued specific regulations for many different metallic and nonmetallic dusts found in mining applications. These are expressed as Permissible Exposure Limits (PELs), which are measured and averaged over a worker’s 8-hour shift.
Companies involved with mineral extraction and processing must first consider the general limit for exposure to particulate of any kind (i.e., nuisance dust, PM10 dust). The limit for “Particulates Not Otherwise Regulated” (PNOLs) is 15 mg/m3 (8-hour TWA limit) for total particulate and 5 mg/m3 for respirable particulate. Employers must also follow general housekeeping standards (OSHA 1910.22, Walking-Working Surfaces) to prevent accumulation of dust on surfaces.
Manufacturers are responsible for ensuring that workers are not exposed to hazardous dusts in levels above the PELs. Failure to control dust in areas where workers may be exposed can result in serious fines and legal action. For some highly toxic substances, such as lead and crystalline silica, OSHA also sets a separate action limit; exposures above this limit may require specific compliance activities such as blood testing. These are PELs for some of the metals and other elements found in surface mining, quarrying and mineral ore processing.
- Respirable Crystalline Silica: 50 μg/m3 (PEL)/action limit 25 μg/m3
- Asbestos 0.1 fiber per cubic centimeter (pcc) of air; excursion limit (30 minute) 1.0 fiber pcc
- Lead: 50 μg/m3 (PEL)/action limit 30 μg/m3
- Iron oxide: 10 mg/m3
- Nickel: 1.0 mg/m3
- Tin: 2.0 mg/m3
- Cadmium: 0.005 mg/m3
- Manganese: 5.0 mg/m3
- Cobalt: 0.1 mg/m3
- Lithium hydride: 0.025 mg/m3
- Talc (not containing asbestos fibers): 20 million particles per cubic foot
In general, companies are expected to use engineering controls to reduce exposure levels to within the PELs wherever possible. Personal protection equipment (PPE) should only be relied on in situations where it is not technically possible to meet the PEL through engineering controls.
Companies in the mining industry must meet certain environmental standards, which may include:
- Limits on inhalable particulate emissions (PM 10, PM 2.5) set by the EPA as part of the Clean Air Act.
- National Emissions Standards for Hazardous Air Pollutants (NESHAP)
- Reporting requirements for the Greenhouse Gas Reporting Program (GHGRP)
- State and local air quality regulations
While particles of sand and large dust are not currently regulated, the EPA regulates inhalable (PM 10/10 μm and smaller) and fine respirable (PM 2.5/2.5 μm and smaller) particulate. The EPA sets clean air standards for inhalable and fine respirable particulate that state and local governments are required to enforce. Large particulate producers, including mining companies and mineral processors, are subject to state and local limits on particulate emissions to keep local air quality within EPA regulations.
In general, companies involved in mineral extraction and processing cannot simply allow dust and emissions to go into the atmosphere. That means that companies must have a dust control system in place to collect excess dust for proper disposal.
Combustible Dust Regulations
Some dust types produced by the mining industry are combustible, most notably coal dust. Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. OSHA’s Combustible Dust National Emphasis Program (NEP) outlines policies and procedures for inspecting workplaces that create or handle combustible dusts.
In addition, manufacturers dealing with combustible dusts must follow National Fire Protection Association (NFPA) standards for prevention of fires and explosions. Mining dust from metal and nonmetal mining and mineral processing falls under NFPA 122, Standard for Fire Prevention and Control in Metal/Nonmetal Mining and Metal Mineral Processing Facilities. Material handlers in the mining industry may also need to follow NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids.
Sand, silica, limestone and gravel dust are generally inert and do not require special combustion precautions. However, these dusts should be tested to determine whether there are other combustible dusts commingled with the rock dust.