Blasting Abrasive Safety

Summary 

This page compares what is known about abrasive media safety at the highest tiers of toxicological evidence, where the actual response of humans and animals exposed to abrasive material dust is studied through epidemiology and controlled animal inhalation. The blasting industry typically makes abrasive selection decisions based on the presence or absence of trace hazardous constituents in the material, which is the lowest tier of evidence and should be used only when exposure data for the material as a whole are unavailable. The toxicology literature has established that this lower tier is not predictive of actual lung disease in workers (IARC, 2019; NTP, 2020; OSHA, 2024).

The evidence base for mineral wool includes more than 10,000 production workers followed across U.S. and European cohorts (Marsh et al., 1990; Marsh et al., 1996; Boffetta et al., 1997), multi-year chronic animal inhalation studies up to 24 months (McConnell et al., 1994), and the 2002 IARC Monograph review (IARC, 2002). After reviewing this evidence, IARC classified rock and slag wool as Group 3, not classifiable as carcinogenic to humans. ACGIH independently assigned the material to category A4. NTP has never listed it as a carcinogen.

No other commercially used blasting abrasive has comparable evidence. Most have been studied only in short-term animal exposure work, and the studies that exist consistently show harm. Coal slag contains essentially no crystalline silica, yet it caused greater lung damage than silica sand in National Institute for Occupational Safety and Health (NIOSH) animal exposure testing (Hubbs et al., 2001). Olivine, marketed as a silica-free alternative, was the most toxic abrasive tested in either NIOSH study (Porter et al., 2002). Aluminum oxide is named in a recognized occupational fibrosis (pulmonary aluminosis) that has been documented in abrasives production workers (Jederlinic et al., 1990). The presence or absence of trace hazardous constituents in a material does not predict whether its dust will cause occupational lung disease. Occupational Safety and Health Administration (OSHA) Hazard Communication Standard 10X superoxalloy abrasives are made from mineral wool, the only commercially used blasting material whose respirable dust has been independently documented to be biosoluble and rapidly cleared from the lungs, and the only one that the International Agency for Research on Cancer (IARC), the American Conference of Governmental Industrial Hygienists (ACGIH), and the US National Toxicology Program (NTP) have determined does not belong on lists of possible human carcinogens. recognizes this explicitly, requiring that whole-material testing be used as a higher tier of evidence than ingredient-based hazard inference (29 CFR 1910.1200).

The single property that distinguishes mineral wool from every other abrasive in commercial use is biosolubility. Mineral wool dust dissolves in lung fluids and is cleared by alveolar macrophages, with a half-life of 5 days measured in standardized testing (Hesterberg et al., 1996). By contrast, NTP measured the clearance half-life of garnet at approximately 89 to 90 days (NTP, 2020). Aluminum oxide cleared at approximately 9% over 20 weeks in a rat instillation study (Stone et al., 2000). Coal slag, crystalline silica, olivine, crushed glass, copper slag, nickel slag, staurolite, specular hematite, and steel grit are all biopersistent, all produced documented lung damage in controlled toxicology studies.

The difference is clearance. Materials whose respirable dust dissolves and is cleared do not produce the chronic inflammation, fibrosis, and other adverse outcomes that biopersistent materials produce in long-term exposure. Safety in blasting operations depends not only on the operational controls a facility maintains, but on the underlying toxicology of the abrasive media being used. The toxicological evidence varies enormously across the materials currently in use commercially. This page presents this evidence in detail to help you make properly informed decisions for safe abrasive blasting.

How to evaluate the safety of abrasive materials 

The three D’s of dust toxicity 

Toxicologists who study inhalation hazards consider three factors when assessing risk to the lungs. These
are sometimes called the three D’s of dust toxicity, and they form the foundation of any rigorous
approach to abrasive media safety evaluation.

Dose. How much dust does the abrasive generate during use, and how much is inhaled at the breathing
zone? Higher dust generation and higher airborne concentrations mean greater exposure.

Dimension. What are the particle sizes and shapes? Particles smaller than approximately 10 microns can
reach the deep gas exchange regions of the lung. Long, thin, durable fibers are more damaging than
shorter or more soluble particles because they are harder for alveolar macrophage cells to phagocytose
and clear.

Duration. How long do the particles persist in lung tissue once inhaled? Particles that dissolve in lung
fluids (biosoluble) clear quickly and cause little to no long-term harm. Particles that resist dissolution
(biopersistent) accumulate and can initiate chronic inflammation, fibrosis, and, in some cases, cancer.

The hierarchy of toxicological evidence 

There is a fourth dimension that determines how much confidence anyone can have in a safety claim. What is the tier of evidence behind it? Not all toxicology data is equal. From strongest to weakest, the hierarchy runs roughly as follows:

1. Comprehensive review by IARC, ACGIH, or equivalent toxicological bodies synthesizing decades of animal data and human worker epidemiology and issuing formal conclusions from the data.
2. Human worker cohort studies and occupational epidemiology
3. Multi-year chronic inhalation studies in animals
4. Multi-month inhalation studies in animals
5. Multi-week intratracheal instillation studies in animals
6. In vitro (laboratory) cell studies and short-term acute exposure studies
7. Material composition assumptions (e.g., “no crystalline silica means safe,” or “no hazardous metals means safe”)

The general principle that human epidemiological evidence outweighs animal data, which in turn outweighs laboratory and mechanistic studies, is codified in the IARC Monographs Preamble (IARC, 2019), which describes the standard weight-of-evidence framework used by international regulatory bodies for hazard identification. Most blasting abrasives have been tested at tiers 5 through 7. Mineral wool material has been tested at all seven tiers, including the human worker epidemiology, which no other commercially used blasting abrasive has. The comparison table below illustrates this important distinction. The degree, completeness, and validation of the testing are the central reasons that mineral wool material and 10X abrasives stand out as a safe abrasive blasting material in the published
toxicology literature.

Conclusive testing of whole materials supersedes hazardous ingredients

Another critically important principle is whether the toxicology evidence comes from testing the whole material as it actually exists in use, or whether hazards are being inferred from the presence of individual hazardous ingredients in the material. These are not equivalent. Whole-material testing measures what a worker is actually exposed to under realistic conditions, with all of its constituents, surface chemistry, particle morphology, and biopersistence in the lung. Ingredient-based hazard inference assumes that the toxicity of a mixture equals the sum of the toxicities of its components, which often overstates or understates the actual risk depending on how the constituents interact. This is not just an academic distinction. The OSHA Hazard Communication Standard (29 CFR 1910.1200) explicitly recognizes whole-material testing as the higher tier of evidence and instructs that "if a mixture has been tested as a whole, the results should be used to determine whether the mixture is hazardous" (OSHA, 2007). Only when whole-mixture data is unavailable does the standard fall back to the lower tier of evaluating ingredients individually. The same hierarchy is built into the Globally Harmonized System of Classification and Labeling of Chemicals (GHS), which OSHA's standard implements (United Nations, 2023). The implications for abrasive selection are important to understand as safety professionals and
operators navigate worker exposure risks. An abrasive whose components include only naturally occurring oxides may still produce damaging dust in use, as findings from NIOSH and NTP concerning exposure to abrasive dusts demonstrate. Conversely, a material whose individual constituents include trace hazardous metals may still produce dust that has been shown not to cause lung disease in actual workers, as decades of mineral wool worker epidemiology and multi-year animal inhalation studies demonstrate. The presence of trace hazardous ingredients does not necessarily render a material dust toxic, nor does their absence render a material dust safe. The whole-material evidence is what matters in real-world risk assessment where the health and lives of workers are at stake.

What if hazardous ingredients have been designated carcinogens?

OSHA’s framework treats carcinogenicity with extra caution. Where a mixture contains an ingredient that has been classified as a carcinogen by an authoritative body, the standard does not allow ingredient-based hazard to be overridden by whole-material testing alone. Whole-material evidence can apply only when it is conclusive and consistent with the determinations of authoritative bodies including IARC and NTP (29 CFR 1910.1200, Appendix A, A.6). The evidence from the human and animal data for mineral wool meet this higher bar because IARC, ACGIH, and NTP have evaluated the whole-mixture data and have issued official decisions that the evidence does not support including it in lists of possible human carcinogens.

The IARC Working Group classified rock and slag wool as not classifiable as carcinogenic to humans (Group 3) in 2002 after reviewing the conclusive chronic inhalation and worker cohort evidence (IARC, 2002). ACGIH independently assigned mineral wool to category A4, also not classifiable as a human carcinogen. NTP has never listed rock and slag wool in its Report on Carcinogens, and in 2011 it removed biosoluble fibers from the related glass wool category on the basis of the same biosolubility property that defines mineral wool (NTP, 2011). The whole-material evidence on mineral wool has been independently affirmed by the authoritative bodies whose determinations are required under OSHA’s carcinogen provision.

Does the trace presence of beryllium in 10X abrasives make them unsafe?

These evidentiary frameworks established by toxicological authorities and regulatory bodies provide a definitive response to a claim being made by competitors that the trace beryllium content of 10X abrasives makes them toxic. Mineral wool, like many naturally occurring mineral materials, does contain beryllium at trace levels similar to the average level in crustal rock (less than 10 parts per million). The inferential leap from “10X contains beryllium” to “10X is toxic” could only be true if excess disease or cancer were observed and documented in the decades of whole-material exposure studies that were reviewed by IARC, ACGIH, and NTP. 

Beryllium is classified as a Group 1 carcinogen by IARC, which means that under OSHA’s framework, whole-material evidence for mineral wool must clear the higher bars of conclusive evidence and concurrence of authoritative bodies before it can override an ingredient-based hazard inference. Mineral wool clears those bars. The IARC Working Group placed mineral wool in Group 3 after reviewing production worker cohorts followed across decades, United Kingdom installer studies documenting mineral wool exposures reaching peak levels of 51.5 mg/m³ total dust (Head & Wagg, 1980, as cited in IARC, 2002), and multi-year chronic animal inhalation studies in which rock and slag wool produced no excess lung tumors at any tested dose (IARC, 2002; McConnell et al., 1994).  If the trace levels of beryllium in mineral wool posed a genuine inhalation hazard, the adverse effects would have surfaced in this conclusive body of evidence. IARC, ACGIH, and NTP would have been forced to categorize mineral wool differently.

Comparative toxicology of blasting abrasives

The table summarizes published toxicology evidence for the major blasting abrasives currently in commercial use, drawing from IARC Monograph Volume 81 (2002), NIOSH studies by Hubbs et al. (2001) and Porter et al. (2002), NTP Technical Report 91 (2020), McConnell et al. (1994), and the occupational health literature on aluminum oxide.

Mineral wool is the only abrasive that has been studied across more than 10,000 production workers in U.S. and European cohorts followed for decades, plus multiple chronic animal inhalation studies and a full IARC evidence review concluding that the evidence does not support classifying the material as carcinogenic. Most other abrasives have been studied in one or two short-term animal studies and have no human cohort data at all. When operators ask which products qualify as safe blasting abrasives based on toxicology evidence, the table provides a scientifically backed answer.

The evidence base for 10X Superoxalloy Abrasives and mineral wool

The preceding section described the regulatory frameworks that govern abrasive safety claims and the determinations those frameworks have produced for mineral wool. This section presents the underlying evidence that those frameworks reviewed. 10X abrasives are made from particles separated and cleaned from the byproduct of mineral wool insulation manufacturing. The particles share the chemical composition and biosolubility properties of the mineral wool fibers that have been studied extensively by independent researchers and regulatory bodies. This shared chemistry is what makes 10X a safe blasting abrasive in the strict toxicological sense. This section presents the body of evidence for mineral wool in more detail.

Human worker epidemiology

The IARC Working Group reviewed two large worker cohorts when evaluating mineral wool in 2002. The U.S. University of Pittsburgh cohort followed 1,846 male rock and slag wool production workers across six plants, with employment dating to 1945 and mortality follow-up through 1985 (Marsh et al., 1990). A later follow-up expanded the cohort to 3,035 male and female workers across five plants employed between 1945 and 1978 (Marsh et al., 1996). The European cohort followed more than 10,000 rock and slag wool workers across seven plants with 114,228 person-years of observation (Boffetta et al., 1997).

The Working Group’s conclusion from these cohort studies: “Results from the most recent cohort and nested case–control studies of United States workers exposed to glass wool and continuous glass filament and of European workers exposed to rock (stone) and slag wool have not provided consistent evidence of an association between exposure to fibres and risk for lung cancer or mesothelioma” (IARC, 2002, p. 331). No increased risk for mesothelioma or tumors was found in any rock or slag wool cohort.

Chronic animal inhalation evidence

The most rigorous animal study of rock and slag wool is McConnell et al. (1994), published in Inhalation Toxicology. Male Fischer 344/N rats were exposed by nose-only inhalation to rock wool or slag wool at concentrations of 3, 16, or 30 mg/m³ for six hours per day, five days per week, for 24 months, with lifetime observation through 28 months. Crocidolite asbestos served as the positive control. The high exposure concentration of 243 WHO fibers/cm³ exceeded typical workplace airborne fiber levels by more than two orders of magnitude.

The results: no increase in lung tumors or mesotheliomas in any rock wool or slag wool exposure group compared to unexposed controls. Crocidolite asbestos in the same study produced lung tumors in 14% of exposed animals and one mesothelioma. Rock wool produced minimal focal pulmonary fibrosis at the two highest doses; slag wool produced no fibrosis at any dose. 10X superoxalloy abrasives are produced from the byproducts of slag wool.

Lung clearance was rapid. After 12 months of exposure followed by 12 months of recovery, the number of rock wool fibers longer than 20 micrometers retained in the lung dropped by approximately 93%, and slag wool fibers longer than 20 micrometers dropped by approximately 96%. Crocidolite asbestos fibers in the same study cleared by only about 25% over a comparable recovery period. Electron microscopy showed mineral wool fibers visibly pitted, eroded, and segmentally dissolved after six months in lung tissue. Asbestos fibers showed no morphological change after 24 months. Particle dusts, like those from abrasive blasting, are well known to be more easily cleared and less toxic than longer fibrous particle dusts (McConnell et al., 1994; Padmore et al., 2017).

IARC classification and what Group 3 means

The IARC Working Group’s unanimous Group 3 classification of rock and slag wool was the formal output of the synthesis of human and animal evidence summarized above. The classification reflects a specific finding that the evidence does not support placing mineral wool on lists of possible human carcinogens. In fact, this IARC classification removed mineral wool from lists of possible human carcinogens worldwide. Group 3 is distinct from Group 2B (possibly carcinogenic), Group 2A (probably carcinogenic), and Group 1 (carcinogenic). Group 3 is currently the safest classification IARC currently assigns. It places mineral wool in the same category as coffee, which IARC reclassified to Group 3 in 2016 after decades of review. Several common substances, including aloe vera whole-leaf extract and traditional Asian pickled vegetables, carry the more concerning Group 2B (possibly carcinogenic) classification that mineral wool does not.

Biosolubility by design

Mineral wool manufacturers have, since the 1980s, reformulated the chemistry of their products specifically to ensure that respirable mineral wool dust particles dissolve in lung fluids. The calcium-magnesium-aluminum-silicate composition of slag wool causes respirable dusts to dissolve rapidly in both intracellular fluid (pH 4.5, inside macrophages) and extracellular lung fluid (pH 7.4) (Christensen et al., 1994; Potter and Mattson, 1992). This engineered chemistry is the underlying reason for the rapid lung clearance documented in animal studies of mineral wool.

10X abrasives share this chemistry. The particles produced during mineral wool manufacturing have the same composition as the fibers and the same biosolubility behavior. Because the particles have lower aspect ratios than the long fibers, they are more readily phagocytosed by alveolar macrophages and cleared more rapidly than the fibers, which already cleared at approximately 90% within 12 months in the McConnell chronic inhalation study.

The importance of this clearance behavior is established by a separate body of toxicology research focused on what are called “poorly soluble particles,” materials at the opposite end of the biosolubility spectrum from mineral wool. Oberdörster’s foundational 1995 paper in Regulatory Toxicology and Pharmacology established the framework that has governed the field since (Oberdörster, 1995). When respirable particles deposit in the deep lung faster than alveolar macrophages can clear them, the result is “lung overload,” a condition of impaired clearance in which particles accumulate, macrophage function becomes dysregulated, and a cascade of pathological events follows. Oberdörster identified clearance rate as the determinative factor in whether inhaled particles produce long-term harm, and identified biosolubility, the capacity of particles to dissolve in lung fluids, as the primary determinant of clearance rate.

The Bevan et al. (2018) synthesis of the two decades of research that followed Oberdörster’s original work, also published in Regulatory Toxicology and Pharmacology, confirmed and extended the central finding. The adverse pathway that leads to particle-induced lung disease is initiated by impaired clearance, which leads to persistent inflammation, oxidative stress, and cell proliferation. Repeated, chronic exposure eventually leads to fibrosis and, in some cases, to tumor formation. Bevan and colleagues also documented that the pathway is threshold-related at every step. When particles dissolve and are cleared, the downstream events of inflammation, oxidative stress, fibrosis, and tumor formation do not follow. The adverse pathway is not initiated.

This is why biosolubility is the central property in any assessment of long-term inhalation hazard. A material whose respirable dust dissolves in lung fluids and is cleared by macrophages does not accumulate, does not produce sustained inflammation, and does not progress through the pathway that leads to chronic lung disease. Mineral wool is specifically formulated to have this property, and the absence of lung tumors, mesotheliomas, or fibrosis-mortality excesses in decades of worker cohort studies is the real-world confirmation that the engineering succeeded.

Biosolubility and the rapid clearance it enables illuminate the central finding of the comparative toxicology table presented earlier on this page. Every abrasive material other than 10X in that table, regardless of its specific constituents, is biopersistent. Silica sand, coal slag, garnet, olivine, crushed glass, copper slag, nickel slag, staurolite, specular hematite, steel grit, and aluminum oxide all have respirable particles that resist dissolution in lung fluids and clear slowly when they clear at all.

The contrast between mineral wool and the alternative abrasives is most direct when expressed as clearance half-lives. Direct measurement of slag wool fiber biopersistence in rat lungs, cited in the IARC Monograph review of mineral wool, documented a fiber disappearance half-life of approximately 5 days for fibers longer than 20 micrometers (Hesterberg et al., 1996). NTP’s 2020 inhalation testing of garnet, by contrast, documented a clearance half-life of approximately 89 to 90 days, more than fifteen times longer than slag wool, with corresponding consequences that garnet produced the highest steady-state lung burdens and the highest incidence of chronic active inflammation among the alternatives tested (NTP, 2020). NTP also reported half-lives of 33 to 35 days for blasting sand and 16 to 17 days for crushed glass, both multiples higher than slag wool.

The Hesterberg study established that long slag wool fibers disappear quickly because the material itself dissolves in lung fluids, fragmenting the long fibers into shorter pieces that are then cleared by other macrophages. Because 10X abrasive dust is comprised of particles with much shorter lengths than the long fibers measured by Hesterberg, and are smaller than the diameter of an alveolar macrophage, they can be fully phagocytosed from the outset and dissolved through the same intracellular mechanism. The 5-day half-life for long slag wool fibers therefore represents a conservative upper bound estimate of 10X particle clearance in the lung.

The contrast with aluminum oxide is equally stark. In a 20-week rat instillation study, aluminum oxide cleared at approximately 9% after exposure ended (Stone et al., 2000). Over a comparable timeframe, the long mineral wool fibers in the McConnell chronic inhalation study cleared at approximately 90%. Aluminum oxide and mineral wool, both inorganic mineral materials marketed as abrasives, differ by roughly an order of magnitude in their ability to be cleared from the lung, and the corresponding occupational health record reflects that difference. Mineral wool workers have been followed over decades without an excess of lung tumors or fibrosis mortality. Aluminum oxide abrasives workers, by contrast, are among the occupational populations in which pulmonary aluminosis has been documented, with one 1990 study finding pulmonary fibrosis in all nine workers examined from a single aluminum oxide abrasives plant (Jederlinic et al., 1990). 

The evidence base for other abrasives

The U.S. National Institute for Occupational Safety and Health (NIOSH) tested 11 commercially available silica sand substitutes across two studies published in 2001 and 2002 (Hubbs et al., 2001; Porter et al., 2002). The U.S. National Toxicology Program (NTP) conducted follow-up inhalation studies on five of these materials in 2020 (NTP Technical Report 91). These studies were specifically designed to evaluate whether commonly marketed alternative materials qualify as safe blasting media under controlled toxicological conditions. None of them qualify.

Silica-free does not mean safe

The most consequential finding from these studies concerns coal slag, the most widely used silica sand substitute. Despite containing essentially no crystalline silica, coal slag caused greater lung damage than blasting sand itself in the NIOSH testing. Rats exposed to a single 10 mg dose of coal slag showed higher lactate dehydrogenase release, higher neutrophil influx, and elevated lung hydroxyproline, a biochemical marker of fibrosis, than rats exposed to blasting sand four weeks after exposure (Hubbs et al., 2001). NTP confirmed in 2020 inhalation studies that coal slag caused focal lung inflammation and alveolar proteinosis. The NTP authors noted: “The presence of crystalline silica was not the only determinant of lung toxicity in the 2-week studies because the coal slag tested contained no crystalline silica, yet there was some incidence of focal inflammation and proteinosis in the lungs of coal slag-exposed rats” (NTP, 2020, p. 64). The implication for abrasive selection is that “silica-free” or “low-silica” is not by itself evidence that an abrasive is safe for blasters, which is why whole-material test results represent a higher tier of evidence than data regarding ingredients.  The presence or absence of hazardous ingredients does not necessarily establish the safety or toxicity of a material. And clearance rate, the most important of all characteristics, can only be appropriately measured in whole-material testing.

Eight of ten substitutes showed persistent lung damage in NIOSH testing

Across the two NIOSH studies, eight of the ten non-sand substitutes tested (coal slag, garnet, staurolite, treated sand, copper slag, nickel slag, crushed glass, and olivine) produced persistent pulmonary cytotoxicity, persistent inflammation, or histopathologic evidence of fibrosis 28 days after a single 10 mg exposure. The NIOSH authors’ conclusion: “The persistent pulmonary inflammation and damage caused by the abrasive blasting substitutes… suggest that they are not nontoxic alternatives to blasting sand” (Porter et al., 2002, p. 1137).

Olivine, often marketed as a silica-free or environmentally preferable alternative, was the most toxic abrasive tested in either NIOSH study. Olivine caused higher polymorphonuclear neutrophil influx, higher lactate dehydrogenase release, higher serum albumin in bronchoalveolar lavage fluid, and more alveolitis than blasting sand itself. Alveolar lipoproteinosis, which is a pathological condition associated with severe particulate exposure, was observed in 100% of olivine-exposed rats (Porter et al., 2002).

Even the cleanest alternative to silica sand produced harm under chronic exposure

NTP selected specular hematite for its 39-week inhalation study because it had appeared cleanest in the 2001 and 2002 NIOSH screening studies. The 39-week results showed that specular hematite still produced chronic active inflammation, interstitial fibrosis, alveolar epithelial hyperplasia, and squamous metaplasia of the larynx at exposure concentrations of 15 mg/m³ and higher. “After 39 weeks of exposure to specular hematite, the lowest-observed-effect level was 15 mg/m³ for chronic active inflammation and interstitial fibrosis within the lung” (NTP, 2020, p. xiii). 

Garnet produced chronic lung inflammation in all exposed animals in NTP testing

The slow clearance of garnet documented in the biosolubility section above caused clear toxicological consequences in NTP’s inhalation testing. All five rats in both the 15 mg/m³ and 30 mg/m³ garnet exposure groups developed chronic active inflammation in the lung, which was the highest incidence among the alternative abrasives tested. The paper concludes that garnet was “the most toxic of the alternative blasting agents in regard to the incidence of chronic active inflammation in the lung” (NTP, 2020, p. 63). The slow clearance and the inflammation finding together place garnet as the alternative abrasive with both the longest lung retention and the highest documented incidence of chronic inflammatory response in controlled testing.

Separate studies of aluminum oxide document occupational lung disease

Aluminum oxide was not included in the NIOSH or NTP comparative studies, but the occupational health literature on aluminum oxide exposure is substantial.  Pulmonary aluminosis, also known as Shaver’s disease, is a recognized occupational lung disease caused by inhalation of aluminum-containing dust, including aluminum oxide. First described in 1947, it is an interstitial pulmonary fibrosis with upper-lung predominance that can progress rapidly and was historically fatal in approximately 20% of affected workers (Taiwo, 2014). Although exposure controls in aluminum production have reduced the incidence of the disease, contemporary case reports continue to document new diagnoses. A 2006 paper described aluminosis as “an almost forgotten disease” still detectable by high-resolution computed tomography in current workers (Kraus et al., 2006).

The most directly relevant published study for blasting media is Jederlinic et al. (1990), published in the American Review of Respiratory Disease. The authors investigated nine workers from a plant that produced aluminum oxide abrasives from alundum ore. Mean exposure duration was 25 years and mean time since first exposure was 28 years. All nine workers had abnormal chest radiographs. Pathological examination of three workers confirmed pulmonary fibrosis with elevated aluminum content in lung tissue.

Lung clearance of aluminum oxide has been measured to be slow. A 20-week instillation study in rats found that approximately 9% of the lung aluminum burden cleared after exposure ended (Stone et al., 2000). For comparison, mineral wool fibers in the McConnell study cleared by approximately 90% over a 12-month recovery period.

The aluminum industry’s own commissioned review of aluminum oxide health risks, conducted by Krewski et al. (2007) at the University of Ottawa and published as a 269-page supplement in the Journal of Toxicology and Environmental Health, classified the evidence for aluminum dust inhalation causing lung irritation and physiological changes, including fibrosis, as “strong,” the highest classification in their evidence hierarchy. The same review incorporates the Jederlinic et al. (1990) finding that aluminum oxide was the causative agent in the pulmonary fibrosis observed in nine of nine aluminum oxide abrasive workers studied.

What the authors of exposure studies of other abrasives concluded

Across the two NIOSH studies, the 2020 NTP technical report, and the broader occupational health literature on aluminum oxide, none of the alternative abrasives tested were deemed to qualify as safe blasting media under controlled toxicological conditions. The authors of the two NIOSH abrasive exposure studies stated their findings directly. The blasting sand substitute abrasives “are not nontoxic alternatives to blasting sand” (Porter et al., 2002, p. 1137). The 2020 NTP technical report of inhalation studies essentially confirmed the findings of the NIOSH instillation studies. Krewski et al. (2007), in the aluminum industry’s own commissioned review, concluded that the evidence for lung irritation and adverse physiological changes from inhalation of aluminum-containing material, including aluminum oxide, was strong. For every material studied, the authors stated explicitly that exposure produced persistent lung damage in animal testing, induced occupational disease in worker populations, or both.

What this means for you and your team

Abrasive blasting is a profession where workers spend months and years on end in an inherently risky environment. Blasting involves very high-energy, high-pressure, high-speed particles, and working at high elevation and in enclosed spaces. There are many risks to be mitigated.  We at 10X Engineered Materials always recommend following OSHA guidelines and using best-in-class practices with personal protective equipment and safe operational procedures. Yet, even if all of this is implemented perfectly, there will still be dust exposure. Exposure certainly can and should be minimized, but respirable dust is invisible, and it settles very slowly or not at all. Even if only limited exposure occurs during entry into or exit from the working environment, during clean-up, or outside of containment or a cabinet, the effects can build over time if our lungs can’t clear the dust. 

The upshot of the gold-standard mineral wool dust exposure studies presented here, and the conclusions of global toxicological authorities after reviewing the studies, is that the lungs of blasters can handle and eliminate respirable mineral wool dust in the same way that their lungs handle the billions of dust particles that we all inhale in the 17,000+ breaths we take every day. Hazardous compounds that may be present in trace quantities dissolve and are removed with the dust particles.  This is what the studies showed, and it is the basis on which the expert working groups of IARC, ACGIH, and NTP issued their official conclusions. 

The same cannot be said for any of the other abrasives for which similar studies have been conducted. Regardless of the presence or absence of trace toxic constituents like crystalline silica or hazardous metals, all of them were shown in peer-reviewed, published studies to induce some form of chronic or permanent lung damage. The difference is clearance. 10X abrasive dust was demonstrated to dissolve and be cleared efficiently. The dusts of the other abrasives studied were not.

Dust exposure is probably the least controllable risk in an abrasive blasting work environment. Abrasive media selection is one of the few aspects of this risk that is fully controllable. The blasting industry relies heavily on the lowest tier of toxicological evidence, material composition, to make these decisions when far better information from whole-material human and animal exposure studies is available. The studies and evidence provided here can allow blasters and their leaders to be confident that health is not being sacrificed in the pursuit of business objectives.

Frequently asked questions

What is the safest blasting abrasive?

Based on the toxicology literature, the abrasive with the strongest evidence of safety is the one made from the most thoroughly studied parent material. 10X superoxalloy abrasives are made from mineral wool, which has been reviewed by the International Agency for Research on Cancer (IARC) after decades of human worker epidemiology and chronic animal inhalation studies. IARC classified rock and slag wool as Group 3, not classifiable as carcinogenic to humans (IARC, 2002). Every other commercially used blasting abrasive has either been classified as carcinogenic (silica sand), has shown harm in controlled testing (coal slag, garnet, olivine, crushed glass, and others), or has not been tested at comparable rigor.

What media is safe for sandblasting?

The toxicology evidence points to 10X superoxalloy abrasives as the blasting media with the strongest published safety record. 10X is made from mineral wool, which has been classified by IARC as Group 3 (not classifiable as carcinogenic to humans) following decades of human worker epidemiology and chronic animal inhalation studies (IARC, 2002; McConnell et al., 1994). Silica sand containing crystalline forms of silica is an IARC Group 1 carcinogen and should be avoided. Coal slag, garnet, olivine, crushed glass, and other commonly marketed silica substitutes all showed persistent lung damage in NIOSH and NTP testing (Hubbs et al., 2001; Porter et al., 2002; NTP, 2020). Aluminum oxide has a recognized occupational lung disease, pulmonary aluminosis, associated with its long-term inhalation (Jederlinic et al., 1990). Of the commercially available materials, only 10X Engineered Materials’ mineral wool abrasive has been studied at the highest evidentiary tiers and emerged with formal safety classification by toxicological authorities.

Is silica free abrasive safe?

Not necessarily. The toxicology evidence does not support the assumption that a silica-free designation equates to safety. Coal slag, which contains essentially no crystalline silica, caused greater lung damage than blasting sand in NIOSH testing (Hubbs et al., 2001). Olivine, which also contains low crystalline silica, was the most toxic abrasive tested in NIOSH studies and caused alveolar lipoproteinosis in 100% of exposed rats (Porter et al., 2002). The U.S. National Toxicology Program concluded that “the presence of crystalline silica was not the only determinant of lung toxicity” (NTP, 2020, p. 64). Other factors, primarily poor solubility in lung fluids and impaired lung clearance rate, contribute to harm. A “silica-free” specification is, by itself, not evidence of safety. In fact, the presence or absence of any hazardous constituent does not guarantee toxicity or safety. Only exposure testing of a material as a whole can resolve the question.

Is aluminum oxide safe to use as a blasting abrasive?

Aluminum oxide has not been tested in the same comparative studies as other blasting abrasives, but the occupational health literature documents a recognized lung disease, pulmonary aluminosis, also called Shaver’s disease, caused by inhalation of aluminum-containing dust. A 1990 study of nine workers in an aluminum oxide abrasives production plant found pulmonary fibrosis in all nine after a mean 25-year exposure (Jederlinic et al., 1990). Lung clearance of aluminum oxide is slow, with one study showing only about 9% clearance after a 20-week exposure (Stone et al., 2000). 

Does coal slag cause lung damage?

Yes, in controlled animal studies. NIOSH found that rats exposed to a single 10 mg dose of coal slag developed greater lung damage than rats exposed to blasting sand, including elevated lactate dehydrogenase, persistent neutrophil influx, and increased lung hydroxyproline, which is a biochemical marker of fibrosis (Hubbs et al., 2001). The U.S. National Toxicology Program confirmed these findings in 2020 inhalation studies, observing focal lung inflammation and alveolar proteinosis (NTP, 2020). Coal slag contains essentially no crystalline silica, demonstrating that “silica-free” does not guarantee safety.

Is garnet abrasive safe for blasters?

Garnet performed poorly in both NIOSH and NTP testing. In NIOSH instillation studies, garnet caused pulmonary cytotoxicity, inflammation, and fibrotic changes comparable to blasting sand (Hubbs et al., 2001). In NTP 2020 inhalation studies, garnet was “the most toxic of the alternative blasting agents in regard to the incidence of chronic active inflammation in the lung” (NTP, 2020, p. 63). Garnet has a lung clearance half-life of approximately 89–90 days, about three times slower than blasting sand, leading to high lung burdens with chronic exposure.

What does IARC say about mineral wool?

After reviewing human worker cohort studies covering more than 10,000 production workers in the U.S. and Europe, plus multiple chronic animal inhalation studies and supporting biopersistence research, the IARC Working Group concluded in 2002 that there is inadequate evidence to support listing mineral wool as a possible human carcinogen. Their official classification of Group 3, not classifiable as to carcinogenicity to humans (IARC, 2002, p. 339), removed mineral wool from lists of possible carcinogens worldwide. The dust produced from blasting with 10X abrasives is not fibrous, making clearance from the lungs even more efficient (McConnell et al., 1994; Padmore et al., 2017).

Why is 10X safer than other blasting abrasives?

10X is made from mineral wool material that has been studied across more tiers of evidence than any other commercially available blasting abrasive. The evidence base includes more than 10,000 production workers followed for decades in U.S. and European cohort studies, multiple chronic animal inhalation studies running up to 24 months, in vitro biopersistence and dissolution research, and a comprehensive 2002 review by the International Agency for Research on Cancer. The material is engineered to be biosoluble, or to dissolve in lung fluids, which results in rapid lung clearance documented at 90% or more within 12 months of exposure ending (McConnell et al., 1994).

Has mineral wool been studied in human workers?

Yes, extensively. The two major cohorts reviewed by IARC are the U.S. University of Pittsburgh cohort, which followed 1,846 to 3,035 rock and slag wool production workers across six plants from 1945 onward (Marsh et al., 1990; Marsh et al., 1996), and the European cohort, which followed more than 10,000 rock and slag wool workers across seven plants with 114,228 person-years of observation (Boffetta et al., 1997). These cohorts provide the human epidemiological foundation for the IARC Group 3 classification. No other blasting abrasive has comparable human cohort evidence.

Does 10X contain beryllium, and is that a safety concern?

Mineral wool, like many naturally occurring mineral materials, contains beryllium at trace levels similar to the average level in crustal rock (less than 10 parts per million). The presence of a trace ingredient does not, by itself, make a material’s dust hazardous. The OSHA Hazard Communication Standard recognizes whole-material testing as a higher tier of evidence than ingredient-based hazard inference (29 CFR 1910.1200), and for materials containing a Group 1 carcinogen ingredient, requires concordance from authoritative bodies including IARC and NTP before whole-material evidence can override that inference. Mineral wool clears this bar. IARC classified rock and slag wool as Group 3, or not classifiable as carcinogenic to humans, after reviewing decades of worker cohort epidemiology and multi-year chronic animal inhalation studies (IARC, 2002; McConnell et al., 1994). ACGIH independently assigned the material to category A4, also meaning not classifiable as carcinogenic in humans. NTP has never listed rock and slag wool as a carcinogen. If trace beryllium in mineral wool posed a genuine inhalation hazard, that hazard would have surfaced in this body of evidence, and the authoritative bodies would have classified the material differently.

What is pulmonary aluminosis?

Pulmonary aluminosis, also called Shaver’s disease, is an occupational interstitial pulmonary fibrosis caused by chronic inhalation of aluminum-containing dust including aluminum oxide. First described in 1947, it has upper-lung predominance and can progress rapidly, with historical fatality rates around 20% (Taiwo, 2014). A 1990 study of nine workers in aluminum oxide abrasives production documented pulmonary fibrosis in all nine after a mean 25-year exposure (Jederlinic et al., 1990). Although exposure controls have reduced incidence, current case reports continue to document aluminosis in working populations (Kraus et al., 2006).

How does 10X compare to coal slag?

10X is made from mineral wool, which the IARC Working Group classified as Group 3 (not classifiable as carcinogenic to humans) after reviewing decades of evidence from more than 10,000 worker cohorts and multiple chronic inhalation studies (IARC, 2002). Coal slag has no IARC classification and has been tested in two NIOSH studies and a single 2020 NTP inhalation study. In all three studies, coal slag caused lung damage equal to or exceeding silica sand, including persistent inflammation, elevated lung hydroxyproline indicating fibrosis, and alveolar proteinosis (Hubbs et al., 2001; NTP, 2020). The evidence asymmetry between the two materials is substantial. 10X’s parent material has been studied at the highest tiers of toxicology evidence and emerged with the safest available classification, while coal slag has been studied at lower tiers and has shown harm in every controlled study to date.

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