Mouse pulmonary response to dust from sawing Corian®, a solid-surface composite material

Hazardous dusts from the fabrication of countertop: a review

Artificial countertop materials, including solid surface composites (SSC) and engineered stone (ES) may pose significant pulmonary health risks for workers who manipulate them. These materials have rapidly become popular in the multibillion-dollar countertop industry, rivaling that of natural materials such as granite and marble due to their variety of desirable esthetic qualities and reduced costs. Both SSC and ES consist of a mineral substrate bound together in a polymer matrix. For SSC the mineral is about 70% aluminum trihydrate (ATH) while ES contains up to 95% crystalline silica by weight. Both materials emit airborne dusts when being manipulated with power tools during the fabrication process. Several deaths and dozens of cases of silicosis have been identified worldwide in workers who fabricate ES, while a single case of fatal pulmonary fibrosis has been associated with SCC dust exposure. This review examines the current state of knowledge for both SSC and ES regarding the composition, particle emission characteristics, workplace exposure data, particle constituent toxicity, and possible methods for reducing worker exposure.

Compositional and structural analysis of engineered stones and inorganic particles in silicotic nodules of exposed workers

Background

Engineered stone silicosis is an emerging disease in many countries worldwide produced by the inhalation of respirable dust of engineered stone. This silicosis has a high incidence among young workers, with a short latency period and greater aggressiveness than silicosis caused by natural materials. Although the silica content is very high and this is the key factor, it has been postulated that other constituents in engineered stones can influence the aggressiveness of the disease. Different samples of engineered stone countertops (fabricated by workers during the years prior to their diagnoses), as well as seven lung samples from exposed patients, were analyzed by multiple techniques.

Results

The different countertops were composed of SiO₂ in percentages between 87.9 and 99.6%, with variable relationships of quartz and cristobalite depending on the sample. The most abundant metals were Al, Na, Fe, Ca and Ti. The most frequent volatile organic compounds were styrene, toluene and m-xylene, and among the polycyclic aromatic hydrocarbons, phenanthrene and naphthalene were detected in all samples. Patients were all males, between 26 and 46 years-old (average age: 36) at the moment of the diagnosis. They were exposed to the engineered stone an average time of 14 years. At diagnosis, only one patient had progressive massive fibrosis. After a follow-up period of 8 ± 3 years, four patients presented progressive massive fibrosis. Samples obtained from lung biopsies most frequently showed well or ill-defined nodules, composed of histiocytic cells and fibroblasts without central hyalinization. All tissue samples showed high proportion of Si and Al at the center of the nodules, becoming sparser at the periphery. Al to Si content ratios turned out to be higher than 1 in two of the studied cases. Correlation between Si and Al was very high (r = 0.93).

Conclusion

Some of the volatile organic compounds, polycyclic aromatic hydrocarbons and metals detected in the studied countertop samples have been described as causative of lung inflammation and respiratory disease. Among inorganic constituents, aluminum has been a relevant component within the silicotic nodule, reaching atomic concentrations even higher than silicon in some cases. Such concentrations, both for silicon and aluminum showed a decreasing tendency from the center of the nodule towards its frontier.

Exposure to respirable dust among workers fabricating aluminium trihydroxide-containing synthetic countertops

The aim of this study is to characterize personal exposure of workers to respirable particulate matter (PM) generated in cutting and other fabrication activities when fabricating acryl polymer/aluminium trihydroxide synthetic countertops. We collected 29 personal full-day samples of respirable PM from three workers in a small private workshop. We tested differences between- and within-worker variances of mass concentrations using the Kruskall-Wallis test. We used segmented regression to test the means and medians 15-min interval concentrations changes over time and to identify a breakpoint. Respirable PM concentrations ranged nearly 100-fold, from 0.280 to 25.4 mg/m³ with a median of 2.0 mg/m³ (1-min concentrations from 13,920 data points). There were no statistical difference in daily median or geometric mean concentrations among workers, whereas the concentrations were significantly higher on days with three versus two workers present. The 15-min median concentrations (n = 974 measures) increased until 2.35 h (beta 0.177; p < 0.05), representing a 0.70 mg increase in exposure per hour. This was followed by a plateau in concentrations. The high levels of respirable PM we observed among workers fabricating aluminium trihydroxide-containing synthetic countertops highlight an unmet early prevention need.

Air Pollution and the Airways: Lessons from a Century of Human Urbanization

Since the industrial revolution, air pollution has become a major problem causing several health problems involving the airways as well as the cardiovascular, reproductive, or neurological system. According to the WHO, about 3.6 million deaths every year are related to inhalation of polluted air, specifically due to pulmonary diseases. Polluted air first encounters the airways, which are a major human defense mechanism to reduce the risk of this aggressor. Air pollution consists of a mixture of potentially harmful compounds such as particulate matter, ozone, carbon monoxide, volatile organic compounds, and heavy metals, each having its own effects on the human body. In the last decades, a lot of research investigating the underlying risks and effects of air pollution and/or its specific compounds on the airways, has been performed, involving both in vivo and in vitro experiments. The goal of this review is to give an overview of the recent data on the effects of air pollution on healthy and diseased airways or models of airway disease, such as asthma or chronic obstructive pulmonary disease. Therefore, we focused on studies involving pollution and airway symptoms and/or damage both in mice and humans.

Pulmonary and systemic toxicity in rats following inhalation exposure of 3-D printer emissions from acrylonitrile butadiene styrene (ABS) filament

BACKGROUND

Fused filament fabrication 3-D printing with acrylonitrile butadiene styrene (ABS) filament emits ultrafine particulates (UFPs) and volatile organic compounds (VOCs). However, the toxicological implications of the emissions generated during 3-D printing have not been fully elucidated.

AIM AND METHODS

The goal of this study was to investigate the in vivo toxicity of ABS-emissions from a commercial desktop 3-D printer. Male Sprague Dawley rats were exposed to a single concentration of ABS-emissions or air for 4 hours/day, 4 days/week for five exposure durations (1, 4, 8, 15, and 30 days). At 24 hours after the last exposure, rats were assessed for pulmonary injury, inflammation, and oxidative stress as well as systemic toxicity.

RESULTS AND DISCUSSION

3-D printing generated particulate with average particle mass concentration of 240 ± 90 µg/m³, with an average geometric mean particle mobility diameter of 85 nm (geometric standard deviation = 1.6). The number of macrophages increased significantly at day 15. In bronchoalveolar lavage, IFN-γ and IL-10 were significantly higher at days 1 and 4, with IL-10 levels reaching a peak at day 15 in ABS-exposed rats. Neither pulmonary oxidative stress responses nor histopathological changes of the lungs and nasal passages were found among the treatments. There was an increase in platelets and monocytes in the circulation at day 15. Several serum biomarkers of hepatic and kidney functions were significantly higher at day 1.

CONCLUSIONS

At the current experimental conditions applied, it was concluded that the emissions from ABS filament caused minimal transient pulmonary and systemic toxicity.

In vitro toxicity assessment of respirable solid surface composite sawing particles

Solid surface composites (SSCs) are a class of popular construction materials composed of aluminum trihydrate and acrylic polymers. Previous investigations have demonstrated that sawing SSC releases substantial airborne dusts, with a number-based geometric mean diameter of 1.05 µm. We reported that in mice, aspiration exposure to airborne SSC dusts induced symptoms of pulmonary inflammation at 24-h postexposure: neutrophilic influx, alveolitis, and increased lactate dehydrogenase (LDH) and pro-inflammatory cytokine levels in lavage fluid. The particles appeared to be poorly cleared, with 81% remaining at 14-day postexposure. The objective of this study was to determine the toxicity specifically of respirable particles on a model of human alveolar macrophages (THP-1). The relative toxicities of subfractions (0.07, 0.66, 1.58, 5.0, and 13.42 µm diameter) of the airborne particles were also determined. THP-1 macrophages were exposed for 24 h to respirable particles from sawing SSC (0, 12.5, 25, 50, or 100 µg/ml) or size-specific fractions (100 µg/ml). Exposure to respirable SSC particles induced THP-1 macrophage toxicity in a dose-dependent manner. Viability was decreased by 15% and 19% after exposure to 50 and 100 µg/ml SSC, respectively, which correlated with increased cell culture supernatant LDH activity by 40% and 70% when compared to control. Reactive oxygen species (ROS) production and inflammatory cytokines were increased in a dose-dependent manner. A size-dependent cytotoxic effect was observed in the cells exposed to subfractions of SSC particles. SSC particles of 0.07, 0.66, and 1.58 µm diameter killed 36%, 17%, and 22% of cells, respectively. These results indicate a potential for cytotoxicity of respirable SSC particles and a relationship between particle size and toxicity, with the smallest fractions appearing to exhibit the greatest toxicity.

A Systematic Safety Evaluation of Nanoporous Mannitol Material as a Dry-Powder Inhalation Carrier System

For carrier-based dry-powder inhaler (DPI) formulations, the adhesion between carrier particles and active pharmaceutical ingredients (API) particles have a significant influence on the aerosolization performance of the API-carrier complexes and the desired detachment of the API for efficient pulmonary delivery. In our previous study, nanoporous mannitol material was successfully fabricated as carriers by a one-step nonorganic solvent spray drying method with the thermal degradation of ammonium carbonate. These carriers were shown to achieve excellent aerosolization performance. In addition, no residue of ammonium carbonate was detected on the powder surface. However, the safety of nanoporous mannitol carriers (Nano-PMCs) during pulmonary administration/delivery was still unknown because the lung is vulnerable to the inhaled particles. To address this question, the present study was conducted to construct a systematic safety evaluation for DPIs carriers to investigate the safety of Nano-PMCs in the whole inhalation, which would make up for the lack of detailed and standardized method in this field. In vitro safety evaluation was carried out using respiratory and pulmonary cytotoxicity tests, hemolysis assay, and ciliotoxicity test. In vivo safety evaluation was studied by measuring inflammatory indicators in the bronchoalveolar lavage fluid, assessing the pulmonary function and observing pulmonary pathological changes. Nano-PMCs showed satisfactory biocompatibility on respiratory tracts and lungs in vitro and in vivo. It was suggested that Nano-PMCs were safe for intrapulmonary delivery and potential as DPI carriers.