Papers by Christina Isaxon
Placenta, Aug 6, 2018
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PLOS ONE, Jul 18, 2019
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Annals of Work Exposures and Health, May 1, 2023
Construction and demolition workers are exposed to high levels of particulate matter (PM) from bu... more Construction and demolition workers are exposed to high levels of particulate matter (PM) from building materials throughout their working life. Although nano-enabled building materials (NEBMs) may improve the performance and functionality of buildings, concerns are being raised regarding health risks from occupational exposure to PM from NEBMs. In this work, an experimental set-up for integrated resuspension and characterization of PM from NEBMs was developed and tested using three types of concrete (low density, normal, high strength), each enhanced with Carbon Nanotubes (CNTs) at different concentrations (0, low, high). The performance of portable devices used in occupational exposure assessments (DustTrak and NanoTracer) was compared with stationary instruments and gravimetric filter techniques. 40-70% of the mass and 90-98% of the number of particles were within the respirable fraction, with primary modes at 150 nm and 2-3 µm. Addition of CNTs significantly decreased mean particle number concentrations (PNCs) across the entire characterized size range (7 nm - 20 µm) for low density concrete, whereas the opposite was the case for normal strength and high strength concrete. It was hypothesised that the concrete matrix primarily governs the PM formation, which is in turn modulated by CNT-matrix interactions either suppressing or supporting fragmentation during crushing. SEM imaging could display partially submerged CNTs protruding from concrete fragments. Fundamental interactions at the interface of the nanomaterial and the surrounding matrix needs to be investigated to determine how the PM generated from NEBMs differ from their non-nano counterparts and how to prevent future exposure during demolition.
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International Journal of Environmental Research and Public Health, Mar 7, 2020
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Clinical Infectious Diseases, Jul 29, 2019
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Clinical Proteomics, May 11, 2018
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Frontiers in toxicology, May 26, 2021
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Nanotoxicology, Feb 12, 2021
Abstract Engineered nanomaterials (ENMs) are increasingly produced and used today, but health ris... more Abstract Engineered nanomaterials (ENMs) are increasingly produced and used today, but health risks due to their occupational airborne exposure are incompletely understood. Traditionally, nanoparticle (NP) toxicity is tested by introducing NPs to cells through suspension in the growth media, but this does not mimic respiratory exposures. Different methods to introduce aerosolized NPs to cells cultured at the air-liquid-interface (ALI) have been developed, but require specialized equipment and are associated with higher cost and time. Therefore, it is important to determine whether aerosolized setups induce different cellular responses to NPs than traditional ones, which could provide new insights into toxicological responses of NP exposure. This study evaluates the response of human alveolar epithelial cells (A549) to zinc oxide (ZnO) NPs after dry aerosol exposure in the Nano Aerosol Chamber for In Vitro Toxicity (NACIVT) system as compared to conventional, suspension-based exposure: cells at ALI or submerged. Similar to other studies using nebulization of ZnO NPs, we found that dry aerosol exposure of ZnO NPs via the NACIVT system induced different cellular responses as compared to conventional methods. ZnO NPs delivered at 1.0 µg/cm2 in the NACIVT system, mimicking occupational exposure, induced significant increases in metabolic activity and release of the cytokines IL-8 and MCP-1, but no differences were observed using traditional exposures. While factors associated with the method of exposure, such as differing NP aggregation, may contribute toward the different cellular responses observed, our results further encourage the use of more physiologically realistic exposure systems for evaluating airborne ENM toxicity.
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Journal of Exposure Science and Environmental Epidemiology, Jun 16, 2020
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BMC Public Health, Jan 13, 2023
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Annals of Work Exposures and Health, May 1, 2023
Waste of electrical and electronic equipment (WEEE) is one of the fastest-growing waste streams i... more Waste of electrical and electronic equipment (WEEE) is one of the fastest-growing waste streams in the EU. The airborne occupational and environmental exposures generated by this waste handling are poorly quantified, and the growing use of nanomaterials in electronics adds to the uncertainty of risk assessment. Emission and personal exposure measurements were carried out during industrial recycling for three different metal waste flows: WEEE, metal scrap and cables. Size distributions and number-, mass- and lung deposited surface area concentrations were assessed by on-line techniques, and filter samples were collected for gravimetric analyses, metal content, and electron microscopy. Samples for elemental analyses with Particle Induced X-ray Emission (PIXE) was collected by a 12-stage low-pressure impactor . Additionally, low-cost sensors were deployed for long term monitoring. By number, the size distributions from all three flows were heavily dominated by particles <100 nm. Electron microscopy showed that there are many different elements in the same particle and that the composition of different particles vary considerably. Abundant elements, according to ICP-MS, were Fe, Al, Zn, and Cu, but Pb, Mn, Ba, and Co were also detected. PIXE analysis showed that the chemical composition indeed is different in different particle sizes, with e.g. Cr almost exclusively being present in particles < 200 nm. Low-cost sensors, not previously used for monitoring in highly polluted industrial settings, functioned well after 30 days. This study shows that detailed particle characterization is crucial for understanding of today’s and tomorrow’s waste recycling exposures, and as input to future toxicological assessments.
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Annals of Work Exposures and Health, May 1, 2023
Graphene is a nanomaterial suitable for a wide variety of applications. The industrial production... more Graphene is a nanomaterial suitable for a wide variety of applications. The industrial production and use of graphene is, hence, increasing rapidly. The main challenge in assessing graphene exposure is that graphene is a carbon structure, making it comparable to look for a needle in a haystack. We have explored the possibility to analyze elemental carbon and black carbon as a measure of personal graphene exposure. Exposure and emission measurements for graphene were conducted at two pilot plants using on- and off-line techniques. One plant produces graphene, up to 10 tons per year, using liquid exfoliation technique. The other plant uses graphene to coat paper in a conventional roll-to-roll process. The measurements were conducted both stationary (in the emission zone and in the background) and as personal measurements (in the breathing zone of the workers). We have analyzed elemental carbon and black carbon as a measure of the personal exposure. In the emission and background zone we have measured number of particles and lung deposited surface area concentration of particles <300nm, mass concentration, and we have collected samples for electron microscopy analysis. The exposure was in general low, but we identified tasks with an increase emissions. Measurements of elemental carbon is a promising technique for occupational hygienists to find possible exposure to graphene.
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Papers by Christina Isaxon