Familiarity breeds complacency.
The pervasiveness of portland cement in both industry and home applications means that users tend to approach PC with reduced vigilance in terms of hazard controls and prevention. For job tasks that could result in PC exposure, users should review package directions and warnings as well as updated Safety Data Sheets, which have been affected by OSHA’s recent respirable crystalline silica regulation. After fabrication, PC may have about 25 percent silica-containing material. (Editor's note: after fabrication, most of the silica in portland cement may be amorphous silica. As explained below, according to NIOSH, PC can contain less than one percent crystalline silica, while OSHA defines PC as a substance that can contain greater than one percent crystalline silica.) An exact figure is elusive due to variations in formula by type, the effects of additives, and the lack of standardized reporting methods (for example, some products report percentage silica by volume; others, by weight). Therefore, RCS concentrations will likewise vary within PC-containing products, which include concrete, mortar, plaster, spackle, stucco, terrazzo, and grout. NOT ONE TYPE From the standpoint of industrial hygiene, it is a fallacy to discuss PC as if it were a single easily defined and characterized material; ambiguity and significant dissimilarities abound in the data on PC properties and hazards.  OSHA considers PC a “generic term used to describe a variety of building materials valued for their strong adhesive properties when mixed with water.” Manufacturers may use trade names, but common synonyms include cement, hydraulic cement, and PC silicate. The spectrum of PC products is assigned Chemical Abstract Service No. 65997-15-1 by OSHA’s permissible exposure limits and within sampling methods. The inherent hazards of this mixture change by formula, physical state (for example, dry precuring, wet, curing, and dry postcuring), and the addition of diverse admixtures.  To create concrete, PC is mixed with water to form a paste that binds with aggregates such as sand, gravel, and crushed stone. Admixtures and supplementary cementing materials may be added before or during mixing to  modify properties or reduce costs. Variety in worldwide standard cement types allows for choice in performance but influences product formulas and installation considerations. In the United States, commonly used standards for PC are defined by the American Society for Testing and Materials and the American Association of State Highway and Transportation Officials. 
Generalized statements about hazardous components of concern within PC often conflict, possibly due to different definitions or intended context. For example, NIOSH defines PC as containing less than 1 percent silica of the crystalline variety, while OSHA lists PC as a substance that may contain greater than 1 percent crystalline silica. Additional inconsistencies become evident when comparing OSHA’s documents with trade, manufacturer, and geological references. Consequently, IHs must interpret product and material data.  OSHA’s Hazard Communication Standard requires hazard classifications for all hazardous chemicals manufactured, imported, or distributed in the United States. In addition to obtaining the safety data sheets, IHs should contact manufacturers and request additional studies or product information (for example, recommended devices for control of hazards, studies performed on personal protective equipment). IHs should also review the material’s physical and chemical properties as well as any hazards posed by the substance. HAZARDS OF PC Commonly cited health effects of PC include irritation of the eyes, skin, and nose; cough or expectoration; and exertional dyspnea (breathing difficulty), wheezing, and chronic bronchitis. The effects of exposure to cement dust have been associated with many common preexisting health conditions, including asthma and even periodontal tissue destruction. There are fewer studies that broadly examine the adverse health effects of cement dust than the specific hazardous components within cements.  PC exposure routes are inhalation, ingestion, and contact with skin or eyes with the potential to cause both surface and deep tissue damage. Generally, damage increases cumulatively with duration of exposure and concentration.  Two well-documented hazardous components within PC are RCS and hexavalent chromium [Cr(VI)].
Respirable Crystalline Silica
RCS is among the most common carcinogens to which workers are exposed. Breathing RCS dust can cause silicosis, and it is well established that exposure to RCS increases the risk for respiratory diseases, lung cancer, and cardiovascular disease as well as many other health problems.  Workplaces that use PC and other cement products must now comply with OSHA’s new RCS standards, CFR 1926.1153 for construction and CFR 1910.1053 for both general industry and maritime. Both regulations have a PEL of 50 µg/m3 as an eight-hour time-weighted average. As clarified in an OSHA interpretation letter, materials (whether wet or dry) containing 0.1 percent or more crystalline silica by weight or volume are generally covered by OSHA’s HAZCOM requirements and should be noted on SDSs. When the RCS regulation is triggered, OSHA’s HAZCOM requires addressing at least cancer and effects to the lungs, immune system, and kidneys.
It is a fallacy to discuss portland cement as if it were a single easily defined and characterized material; ambiguity and significant dissimilarities abound in the data  on PC properties and hazards. 
While we can now expect manufacturers to provide better labeling and documentation alerting users to the RCS hazards in new materials and products, we still need clarification to determine which components are the actual regulated materials to apply in situations lacking documentation (for example, demolition and renovation). This lack of clarity leaves room for debate and misunderstanding.  OSHA’s RCS regulation defines crystalline silica as “quartz, cristobalite, and/or tridymite.” Geologists recognize these three forms as the major forms of crystalline silica, with quartz as the most common among them. Note that OSHA’s website often uses quartz as a stand-in term for crystalline silica.  OSHA lists no single CAS number for crystalline silica or silica in general, though CAS numbers for some silica-containing materials, including PC, can be found under such generic terms as “mineral dusts.” OSHA’s final rule on Occupational Exposure to Respirable Crystalline Silica warns that “[t]he CAS number is for information only. Enforcement is based on the substance name.”  Lacking an encompassing definition or clear list of CAS numbers associated with crystalline silica causes inconsistent interpretation of manufacturers’ product information and regulatory application. Combine this confusion with insights from studies showing considerable variability in information on SDSs, and it becomes obvious that our profession needs to collaborate with other experts to create a semblance of consensus. At a minimum, IHs should maintain clear paths of communication with analytical laboratories when assessing workplace RCS exposures. On SDSs, silica and silica-containing materials are listed under many synonyms and CAS numbers that cover both crystalline and noncrystalline forms. Synonyms include crystalline silica, quartz, diatomaceous earth, diatomaceous silica, silica amorphous or amorphous silica, glass, sand, silicon oxide, rock crystal, and silica particles.  Per OSHA, SDSs must list components for mixtures that “may contain silica particles that are not respirable, but can become respirable during normal conditions of use or foreseeable emergencies (e.g., blasting or grinding).” It is advantageous to review the constituents (trade names and synonyms) listed in SDSs when developing sampling plans for determining compliance with OSHA’s RCS PELs. Using sample data, in time, IHs can hope to make sense of CAS number confusion.

As one illustration of CAS number inconsistencies within and across government agencies, OSHA Analytical Method ID-142 v4 is listed as acceptable for mixed RCS of quartz, cristobalite, and tridymite, with the following CAS numbers: 14808-60-7, 14464-46-1, and 15468-32-3. However, the method’s webpage includes a link to the NIOSH Pocket Guide to Chemical Hazards page for RCS dust, where the only CAS number listed is 14808-60-7. NIOSH’s Registry of Toxic Effects of Chemical Substances webpage for crystalline silica (quartz) relists CAS number 14808-60-7 and adds 1317-79-9. The three forms of crystalline silica specified in OSHA’s RCS regulations—quartz, cristobalite, and tridymite—encompass only the major natural forms; there are also man-made versions of crystalline silica. How should this gap in OSHA’s RCS regulation be addressed? Should we treat those forms not specified by the new RCS rule as unregulated by OSHA? How do we ensure that this carcinogen is controlled consistently?  Hexavalent Chromium and Other Heavy Metals Trace amounts of the carcinogen Cr(VI) are found in PC and cement products. The presence of Cr(VI) is considered an impurity—that is, an unnecessary component of the material. Attempts to lower Cr(VI) content have led to varied concentrations in manufacturers’ formulas and more variety in available products. Cr(VI) concentrations within a product and its leachate are affected by the manufacturing process, elapsed time since manufacturing, stage of installation, and admixture content. OSHA’s Cr(VI) standards (29 CFR 1926.1126 and 29 CFR 1910.1026) exclude PC because Cr(VI) is expected to be present at only low, trace concentrations in PC. OSHA anticipates that compliance with the PELs for airborne PC would also control Cr(VI) to below both the action level and the PEL. Raw materials introduce other heavy metals of concern—including lead, mercury, cadmium, nickel, cobalt, arsenic, and manganese—to PC and cement products; nickel and cobalt have been linked to inflammatory skin changes. Concentrations of heavy metals fluctuate across geographic regions and are further affected by adjustments made in the PC manufacturing process to produce colors.  Contact Hazards Exposure to PC can result in skin problems that range from mild and brief to severe and chronic. Dermatitis (inflammation of the skin), both the nonallergic and allergic varieties, is one concern. Wet PC may cause irritant contact dermatitis, a nonallergic form. Dermatitis may develop from a single exposure or repeated exposures, and it can affect a worker for years after exposure has ended, causing local or systemic reactions. (It’s also possible that dermatitis won’t develop at all.) Unaddressed dermatitis can progress to chronic skin problems. Workers should alert healthcare providers to their use of PC when seeking early diagnosis for suspected dermatitis.
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After fabrication, portland cement may have about 25 percent silica-containing material; an exact figure is elusive. (Editor's note: after fabrication, most of the silica in PC may be amorphous silica.)
Dry portland cement can have a corrosive alkaline pH as high as 12 to 13.
At least 22 different solid phases of portland cement have been identified, some of which are not stable.
OSHA has an inhalation PEL for dry portland cement of 15 mg/m3 for total dust and 5 mg/m3 for respirable dust.
Cr(VI) can lead to the development of skin sensitization, which is called allergic contact dermatitis. Once sensitized, reactions can be triggered from even small Cr(VI) exposures. Workers can remain sensitized for extended periods. Medical testing for Cr(VI) sensitization is available. When dry, PC is easily airborne, coating nearby workers and surfaces. Dry PC is abrasive and hygroscopic (water-absorbing). It can have a corrosive alkaline (caustic) pH as high as 12 to 13. Third-degree cement burns may develop after only two hours of contact; therefore, workers cannot rely on pain or discomfort as warning signs—at that point, substantial damage may have already occurred. Burns can become worse even after washing the area because the corrosive burn can penetrate skin and beyond, reaching down to muscle and bone. Skin contact with PC can also lead to chrome ulcers.  Dry PC is considered less caustic compared with wet PC, but bodily accumulations of dry PC can activate with moisture (for example, moisture in eyes, sweat, the respiratory system, and water mists). Corrosive moisture can also wick from uncured PC to contaminate a worker’s clothes, tools, and materials.  CONTROLS Engineering controls (for example, barricades and draft control) should be used to reduce the formation and spread of airborne dusts. Long contact times with unprotected skin can be avoided through use of administrative controls and PPE, but workers can often experience long contact times if the PPE itself becomes contaminated. The NIOSH Pocket Guide to Chemical Hazards lists respirator recommendations based on concentrations. OSHA mandates that employers provide washing and hygiene facilities with clean water; nonalkaline, pH-neutral soap; and clean towels for workers exposed to PC. Rinsing or washing of hands in the same water used for cleaning tools is ineffective—the pH of contaminated water will not be affected by the settling of solids to the bottom, a phenomenon that workers often falsely interpret as an indication of cleaner water. ADDITIONAL AIRBORNE EXPOSURE LIMITS OSHA, NIOSH, and ACGIH publish airborne exposure limits for PC and its components, addressing respirable fraction, total dust, and mineral dust. In addition to its new standards specific to RCS, OSHA has an inhalation PEL for dry PC of 15 mg/m3 for total dust and 5 mg/m3 for respirable dust. OSHA has construction regulations (29 CFR 1926.55) for gases, vapors, fumes, dusts, and mists and general industry regulation (29 CFR 1910.1000) for air contaminants of mineral dusts and other related materials. This article does not address the particulars to consider when creating sampling plans and interpreting data. Individuals who perform such tasks should review the details of available methods and select a method applicable to the material targeted for sampling (for example, RCS as quartz, cristobalite). Considerations should be made for contributions from background and simultaneous activities, whether a representative pure bulk sample is necessary for comparison, impacts of PC morphing between phases (at least 22 different solid phases have been identified, some of which are not stable), and the validation range of the analytical method for target material. Bear in mind that airborne background concentrations on construction sites may be affected by disturbance of soil and cement dust contamination from other employers. Airborne concentrations are affected by the location of the work and environmental conditions. Analytical laboratories should be consulted for guidance and critical information such as sampling interferences, which affect the labs’ ability to detect lower levels of analyte.  EDUCATION PC hazard communication must cover Cr(VI), worker access to hygiene facilities, and the importance of hygiene. Show workers how to remove PPE safely—that is, without self-contamination. To help workers avoid tracking contaminants to their vehicles and homes, employers should consider providing changing facilities and lockers in addition to adequate hygiene facilities. TOWARD CONSENSUS As this article demonstrates, substantial confusion can result when IHs try to interpret generally available information on PC. Although the industrial hygiene field is indeed known to be a science and an art that rests on professional judgment, we must create consensus on the definitions and hazards of PC.  My experience has shown that many workers and supervisors fail an informal “pop quiz” on the basics of working with PC safely and the substance’s possible long-term effects. I challenge you to gauge worker knowledge at all levels and to determine if your organization can benefit from refresher training.   VERONICA STANLEY, MSPH, CIH, CESCP, is an industrial hygienist for U.S. Army Medical Command, Atlantic, and owner of Hygiene Health and Safety Consulting LLC in Brookville, Md., specializing in policy and regulation, research, integration, and technical writing. She is a member of the AIHA Construction and IEQ Committees. Ms. Stanley can be reached at (240) 888-2371 or via email Disclaimer: The author of the information herein is a federal government employee. The content is unrelated to official work and/or duties and does not necessarily represent any position or opinion of the government. Acknowledgments: The author thanks Eugene Satrun and Jerome Spear of AIHA’s Construction Committee for reviewing this article.

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RESOURCES ASTDR: Chromium Toxicity. NIOSH: Pocket Guide to Chemical Hazards, Portland cement. NIOSH: Pocket Guide to Chemical Hazards, Silica, crystalline (as respirable dust). NIOSH: Portland Cement. NIOSH: Registry of Toxic Effects of Chemical Substances—Silica, crystalline – quartz. OSHA: Chemical Sampling Information: Silica, Crystalline, Mixed Respirable (Quartz, Cristobalite, Tridymite). OSHA: Occupational Exposure to Respirable Crystalline Silica; Correction. OSHA: Occupational Safety and Health Standards, Toxic and Hazardous Substances, Respirable Crystalline Silica. OSHA: Preventing Skin Problems from Working with Portland Cement. OSHA: Safety and Health Regulations for Construction, Occupational Health and Environmental Controls—Gases, vapors, fumes, dusts, and mists.  OSHA: Safety and Health Regulations for Construction, Toxic and Hazardous Substances, Respirable Crystalline Silica. OSHA: Sampling and Analytical Methods, Quartz And Cristobalite In Workplace Atmospheres. OSHA: Silica, Crystalline: Exposure Evaluation. OSHA: Standard Interpretations, 1910.1200, 1910.1200(b)(2), 1910.1200(c) (February 2015).
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Respirable Crystalline Silica and Other Hazards of a Familiar Substance
BY VERONICA STANLEY




Editor's note: This article has been amended to clarify that, after fabrication, most of the silica in portland cement may be amorphous silica.
A Close Look at
Portland Cement
Although the print version of The Synergist indicated The IAQ Investigator's Guide, 3rd edition, was already published, it isn't quite ready yet. We will be sure to let readers know when the Guide is available for purchase in the AIHA Marketplace.
 
My apologies for the error.
 
- Ed Rutkowski, Synergist editor
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers