Comparative cytotoxicity of respirable surface-treated/untreated calcium carbonate rock dust particles in vitro

Abstract

Calcium carbonate rock dust (RD) is used in mining to reduce the explosivity of aerosolized coal. During the dusting procedures, potential for human exposure occurs, raising health concerns. To improve RD aerosolization, several types of anti-caking surface treatments exist. The aim of the study was to evaluate cytotoxicity of four respirable RD samples: untreated/treated limestone (UL/TL), untreated/treated marble (UM/TM), and crystalline silica (SiO2) as a positive control in A549 and THP-1 transformed human cell lines. Respirable fractions were generated and collected using FSP10 high flow-rate cyclone samplers. THP-1 cells were differentiated with phorbol-12-myristate-13-acetate (20 ng/ml, 48 h). Cells were exposed to seven different concentrations of RD and SiO2 (0–0.2 mg/ml). RD caused a slight decrease in viability at 24 or 72 h post-exposure and were able to induce inflammatory cytokine production in A549 cells, however, with considerably less potency than SiO2. In THP-1 cells at 24 h, there was significant dose-dependent lactate dehydrogenase, inflammatory cytokine and chemokine release. Caspase-1 activity was increased in SiO2- and, on a lesser scale, in TM- exposed cells. To test if the increased toxicity of TM was uptake-related, THP-1 cells were pretreated with Cytochalasin D (CytD) or Bafilomycin A (BafA), followed by exposure to RD or SiO2 for 6 h. CytD blocked the uptake and significantly decreased cytotoxicity of all particles, while BafA prevented caspase-1 activation but not cytotoxic effects of TM. Only TM was able to induce an inflammatory response in THP-1 cells, however it was much less pronounced compared to silica.

Effects of chemical composition on the lung cell response to coal particles: Implications for coal workers' pneumoconiosis

“…In addition, further work is required to confirm that the association is causal and identify the molecular processes driving the cellular response with a view to identifying potential therapeutic approaches. While the exposure protocol we used is well justified on the basis of previous work, 7,16,26 a time course and dose–response study is needed to investigate whether the association between chemical characteristic of particle and cellular response remains consistent under a range of conditions. Nonetheless, our study used a systematic approach to identify associations between the chemistry of coal particles and the response in a range of lung cell types.…”

“…This notion is supported by epidemiological studies showing correlations between coal seam geochemistry and the prevalence of CWP 12 and early in vitro studies showing that cell growth is inhibited to a greater extent by leachates of coal collected from areas with a higher incidence of CWP 8 . Recent in vitro studies have focused on exploring non‐carbon components of coal mine dust as the key reactive compounds leading to coal‐induced lung injury 7,12–16 . However, data from these studies are contradictory, highlighting the necessity for new studies that consider all components of coal mine dusts and how these impact responses in a range of cell types.…”

Thermogravimetry and Mass Spectrometry of Extractable Organics from Manufactured Nanomaterials for Identification of Potential Coating Components

“…NRCWE-013, NRCWE-014, and NRCWE-015 were apparently also associated with a silica contamination indicated by the relatively large amounts of TMOS in the PLE extracts. Calcium carbonate particles are often surface treated with stearic acid [67] which may also change the toxicity [68].…”

Direct-on-Filter FTIR Spectroscopy to Estimate Calcite as A Proxy for Limestone ‘Rock Dust’ in Respirable Coal Mine Dust Samples

“…While acute exposure to calcite dust has not been shown to induce significant cytotoxicity, respiratory irritation is possible, which might contribute to a higher risk of chronic obstructive pulmonary disease (COPD) [7][8][9]. That said, whenever health effects due to RD products have been reported, the respirable crystalline silica (RCS) content was proposed to be the most likely cause [9].…”

“…While acute exposure to calcite dust has not been shown to induce significant cytotoxicity, respiratory irritation is possible, which might contribute to a higher risk of chronic obstructive pulmonary disease (COPD) [7][8][9]. That said, whenever health effects due to RD products have been reported, the respirable crystalline silica (RCS) content was proposed to be the most likely cause [9]. It is noted that United States regulation does allow for a small percentage of respirable crystalline silica (RCS) in RD products (≤4% by mass, per 30CFR §75.2), but studies have consistently indicated that common products typically do not exceed the standard [7,[10][11][12].…”