Is Portland Cement Covered By the Respirable Crystalline Silica in Construction Standard?
Portland cement is one of the most commonly used formulations of cement in construction and is used in concrete, mortar, stucco, and non-specialty grout. Portland cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Cement is made from materials mined from the earth and trace amounts of naturally occurring but potentially harmful chemical compounds such as free crystalline silica, organic compounds, potassium and sodium compounds, heavy metals including cadmium, chromium (including hexavalent chromium), nickel and lead may be present. The majority of safety data sheets of Portland cement indicate less than 1% free crystalline silica. However since there is variability in formulation and it may be possible to have a greater concentration of free crystalline silica, is Portland cement covered by the respirable crystalline silica in construction standard?
The table below shows the typical composition of Portland cement.
|Tricalcium silicate||12168-85-3||20 – 70|
|Dicalcium silicate||10034-77-2||10 – 60|
|Tetracalcium aluminoferrrite||12068-35-8||5 – 15|
|Gypsum (Calcium Sulfate)||13397-24-5||2 – 10|
|Tri-calcium Aluminate||12042-78-3||1 – 15|
|Limestone (Calcium Carbonate)||1317-65-3||0 – 20|
|Nuisance Dusts (Particulates not otherwise regulated)||None||<1-5|
|Crystalline Silica (Quartz)||14808-60-7||0<1|
The occupational health hazards of Portland cement are generally well recognized. These include inhalation, dermal, and eye hazards. Portland cement is caustic, and can result in chemical burns. The powder can cause irritation or, with severe exposure, lung cancer, and can contain some hazardous components; such as crystalline silica and hexavalent chromium (Cr(VI)). Crystalline silica and Cr(VI) are trace constituents of Portland cement not because they are added ingredient but because they are contaminants that enter the mixture during its manufacture. Generally there is less than 20 µg Cr(VI) per gram of cement, or 20 parts per million (ppm). OSHA’s Cr(VI) standards do not apply to operations with Portland cement because OSHA determined that compliance with pre-existing OSHA general standards provides adequate protection for employees exposed to the trace amounts of Cr(VI) found in Portland cement. Other applicable OSHA standards include air contaminants, personal protective equipment, sanitation, and hazard communication.
For Portland cement, OSHA has established a permissible exposure limit (PEL) of 50 mppcf time weighted average (TWA) (PEL listed in Mineral Dusts Table under Silicates (less than 1% crystalline silica), Portland Cement) (29 CFR 1926.55 Appendix A). The American Conference of Governmental Industrial Hygienists (ACGIH) has established a threshold limit (TLV) value of: 10 mg/m3 TWA; The value is for particulate matter containing no asbestos and <1% crystalline silica. Similarly, the National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) of 10 mg/m3 TWA.
Since the exact composition of crystalline silica in Portland cement is variable and even OSHA states that a percentage of greater than 1% is possible, my recommendation is to conduct an exposure assessment for respirable silica during work with Portland cement to ensure employees are not exceeding the action level. If the TWA result is below the action level the reparable crystalline silica standard is not applicable. In the event the TWA exceeds the action level the standard will apply. In both cases the controls outlined in the respirable crystalline silica standard should be implemented when feasible to minimize employee exposures to Portland cement dust.
For assistance with compliance with the respirable crystalline silica standard including initial exposure assessments, written exposure control plans, engineering controls/PPE , training programs, etc. please contact ECOthink Group: firstname.lastname@example.org 646.705.1593. Our certified industrial hygienists (CIHs) are ready to resolve your compliance concerns.