Improving the detection limit in lung counting with a segmented HPGe detector.

A segmented High-Purity Germanium (HPGe) detector with a thin front segment together with various active and passive shield configurations was simulated with the aim of reducing the level of background events in lung counting applications. Eight different detector models were tested in a Geant4 simulation environment in a scenario where inhaled 241Am activity was deposited in the lungs of an ICRP adult reference computational phantom. In lung counting measurements, the Compton continuum in the spectrum is generated by the natural and man-made radionuclides inside the human body and the natural background radiation from the environment. The reduction in Minimum Detectable Activity (MDA) using the segmented HPGe detector combined with an active shield compared to a model with a single germanium crystal was investigated. A reduction in MDA up to 30% and 66% was obtained for internal and external sources, respectively. The results show that the detection limit and/or the measurement time in lung counting can be reduced using such a detector configuration. Furthermore, combining the segmented HPGe detector with an active shield would be particularly useful in field measurements.

Technical note: Simulation of lung counting applications using Geant4.

A Geant4 simulation package has been developed to investigate and test detector configurations for lung counting applications. The objective of this study was to measure radiation emitted from the human body and to make a qualitative comparison of the results of the simulation with an experiment. Experimental data were measured from a plastic phantom with a set of lungs containing 241Am activity. For comparison, simulations in which 241Am activity was uniformly distributed inside the lungs of the ICRP adult reference computational phantom were made. The attenuation of photons by the chest wall was simulated and from this photopeak efficiency and photon transmission were calculated as a function of photon energy. The transmission of 59.5 keV gamma rays, characteristic of the decay of 241Am, was determined from the computational phantom as a function of the angular position of the detector. It was found that the simulated detector response corresponds well with that from an experiment. The simulated count rate below 100 keV was 10.0(7) % greater compared to the experimental measurement. It was observed that 58.3(4) % of photons are attenuated for energies below 100 keV by the chest wall. In the simulation, the transmission of 59.5 keV gamma rays varied from 13.8(2) % to 38.0(4) % as a function of the angular position of the detector. The results obtained from the simulations show a satisfactory agreement with experimental data and the package can be used in the development of future body counting applications and enables optimization of the detection geometry.

Concentrations and number size distribution of fine and nanoparticles in a traditional Finnish bakery.

In bakeries, high concentrations of flour dust can exist and ovens release particles into the air as well. Particle concentrations (mass, number) and number size distribution may vary considerably but the variation is not commonly studied. Furthermore, the role of the smallest size fractions is rarely considered in the exposure assessment due to their small mass. The objectives of this work were to find out how concentrations and number size distribution of fine and nanoparticles vary in a traditional Finnish bakery and to determine the exposure of a dough maker to the nanoparticle fraction of the inhalable dust. Two measurement campaigns were carried out in a traditional, small-scale bakery. Sampling was performed at the breathing zone of the dough maker and three stationary locations: baking area, oven area, and flour depository. Both real-time measurements and conventional gravimetric sampling were conducted. Nanoparticle fraction of the inhalable dust was determined using an IOM sampler with a customized precyclone. Number concentration of fine and nanoparticles, and mass concentrations of both the inhalable dust and nanoparticles were high. The nanoparticle fraction was 9-15% of the inhalable dust at the breathing zone of the dough maker. Different sources, such as ovens and doughnut baking affected the number size distribution. Flour dust contained nanoparticles but most of the fine and nanoparticles were released into the air from the oven operations. However, nanoparticles are not a primary concern in bakeries compared to health effects linked to the large flour particles such as flour-induced sensitization or asthma and development of occupational rhinitis.

In vitro toxicological effects of zinc containing nanoparticles with different physico-chemical properties.

Nanomaterials (NM) exhibit novel physicochemical properties that determine their interaction with biological substrates and processes. Recent nano-technological advances are leading to wide usage of metallic nanoparticles (NPs) in various fields. However, the increasing use of NPs has led to their release into environment and the toxicity of NPs on human health has become a concern. Moreover, there are inadvertently generated metallic NPs which are formed during various human activities (e.g. metal processing and energy production). Unfortunately, there are still widespread controversies and ambiguities with respect to the toxic effects and mechanisms of metallic NPs, e.g. metal oxides including ZnO. In this study, we generated zinc containing NMs, and studied them in vitro. Different nano-sized particles containing Zn were compared in in vitro study to elucidate the physicochemical characteristics (e.g. chemical composition, solubility, shape and size of the particles) that determine cellular toxicity. Zn induced toxicity in macrophage cell line (RAW 264.7) was detected, leading to the cell cycle disruption, cell death and excitation of release of inflammatory mediators. The solubility and the size of Zn compounds had a major role in the induced toxic responses. The soluble particles reduced the cell viability, whereas the less soluble NPs significantly increased inflammation. Moreover, uptake of large ZnO NPs inside the cells was likely to play a key role in the detected cell cycle arrest.

Aerosol emissions of a ship diesel engine operated with diesel fuel or heavy fuel oil.

Gaseous and particulate emissions from a ship diesel research engine were elaborately analysed by a large assembly of measurement techniques. Applied methods comprised of offline and online approaches, yielding averaged chemical and physical data as well as time-resolved trends of combustion by-products. The engine was driven by two different fuels, a commonly used heavy fuel oil (HFO) and a standardised diesel fuel (DF). It was operated in a standardised cycle with a duration of 2 h. Chemical characterisation of organic species and elements revealed higher concentrations as well as a larger number of detected compounds for HFO operation for both gas phase and particulate matter. A noteworthy exception was the concentration of elemental carbon, which was higher in DF exhaust aerosol. This may prove crucial for the assessment and interpretation of biological response and impact via the exposure of human lung cell cultures, which was carried out in parallel to this study. Offline and online data hinted at the fact that most organic species in the aerosol are transferred from the fuel as unburned material. This is especially distinctive at low power operation of HFO, where low volatility structures are converted to the particulate phase. The results of this study give rise to the conclusion that a mere switching to sulphur-free fuel is not sufficient as remediation measure to reduce health and environmental effects of ship emissions.

Physicochemical Characterization of Aerosol Generated in the Gas Tungsten Arc Welding of Stainless Steel.

OBJECTIVES: Exposure to stainless steel (SS) welding aerosol that contain toxic heavy metals, chromium (Cr), manganese (Mn), and nickel (Ni), has been associated with numerous adverse health effects. The gas tungsten arc welding (GTAW) is commonly applied to SS and produces high number concentration of substantially smaller particles compared with the other welding techniques, although the mass emission rate is low. Here, a field study in a workshop with the GTAW as principal welding technique was conducted to determine the physicochemical properties of the airborne particles and to improve the understanding of the hazard the SS welding aerosols pose to welders. METHODS: Particle number concentration and number size distribution were measured near the breathing zone (50cm from the arc) and in the middle of the workshop with condensation particle counters and electrical mobility particle sizers, respectively. Particle morphology and chemical composition were studied using scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy. RESULTS: In the middle of the workshop, the number size distribution was unimodal with the geometric mean diameter (GMD) of 46nm. Near the breathing zone the number size distribution was multimodal, and the GMDs of the modes were in the range of 10-30nm. Two different agglomerate types existed near the breathing zone. The first type consisted of iron oxide primary particles with size up to 40nm and variable amounts of Cr, Mn, and Ni replacing iron in the structure. The second type consisted of very small primary particles and contained increased proportion of Ni compared to the proportion of (Cr + Mn) than the first agglomerate type. CONCLUSIONS: The alterations in the distribution of Ni between different welding aerosol particles have not been reported previously.

Particulate matter from both heavy fuel oil and diesel fuel shipping emissions show strong biological effects on human lung cells at realistic and comparable in vitro exposure conditions.

BACKGROUND: Ship engine emissions are important with regard to lung and cardiovascular diseases especially in coastal regions worldwide. Known cellular responses to combustion particles include oxidative stress and inflammatory signalling. OBJECTIVES: To provide a molecular link between the chemical and physical characteristics of ship emission particles and the cellular responses they elicit and to identify potentially harmful fractions in shipping emission aerosols. METHODS: Through an air-liquid interface exposure system, we exposed human lung cells under realistic in vitro conditions to exhaust fumes from a ship engine running on either common heavy fuel oil (HFO) or cleaner-burning diesel fuel (DF). Advanced chemical analyses of the exhaust aerosols were combined with transcriptional, proteomic and metabolomic profiling including isotope labelling methods to characterise the lung cell responses. RESULTS: The HFO emissions contained high concentrations of toxic compounds such as metals and polycyclic aromatic hydrocarbon, and were higher in particle mass. These compounds were lower in DF emissions, which in turn had higher concentrations of elemental carbon ("soot"). Common cellular reactions included cellular stress responses and endocytosis. Reactions to HFO emissions were dominated by oxidative stress and inflammatory responses, whereas DF emissions induced generally a broader biological response than HFO emissions and affected essential cellular pathways such as energy metabolism, protein synthesis, and chromatin modification. CONCLUSIONS: Despite a lower content of known toxic compounds, combustion particles from the clean shipping fuel DF influenced several essential pathways of lung cell metabolism more strongly than particles from the unrefined fuel HFO. This might be attributable to a higher soot content in DF. Thus the role of diesel soot, which is a known carcinogen in acute air pollution-induced health effects should be further investigated. For the use of HFO and DF we recommend a reduction of carbonaceous soot in the ship emissions by implementation of filtration devices.

Effective density and morphology of particles emitted from small-scale combustion of various wood fuels.

The effective density of fine particles emitted from small-scale wood combustion of various fuels were determined with a system consisting of an aerosol particle mass analyzer and a scanning mobility particle sizer (APM-SMPS). A novel sampling chamber was combined to the system to enable measurements of highly fluctuating combustion processes. In addition, mass-mobility exponents (relates mass and mobility size) were determined from the density data to describe the shape of the particles. Particle size, type of fuel, combustion phase, and combustion conditions were found to have an effect on the effective density and the particle shape. For example, steady combustion phase produced agglomerates with effective density of roughly 1 g cm(-3) for small particles, decreasing to 0.25 g cm(-3) for 400 nm particles. The effective density was higher for particles emitted from glowing embers phase (ca. 1-2 g cm(-3)), and a clear size dependency was not observed as the particles were nearly spherical in shape. This study shows that a single value cannot be used for the effective density of particles emitted from wood combustion.

Reference particles for toxicological studies of wood combustion: formation, characteristics, and toxicity compared to those of real wood combustion particulate mass.

Multiple studies show that particulate mass (PM) generated from incomplete wood combustion may induce adverse health issues in humans. Previous findings have shown that also the PM from efficient wood combustion may induce enhanced production of reactive oxygen species (ROS), inflammation, and cytotoxicity in vitro and in vivo. Underlying factors of these effects may be traced back to volatile inorganic transition metals, especially zinc, which can be enriched in the ultrafine fraction of biomass combustion particulate emission. In this study, nanoparticles composed of potassium, sulfur, and zinc, which are the major components forming inorganic fine PM, were synthesized and tested in vitro. In addition, in vitro toxicity of PM from efficient combustion of wood chips was compared with that of the synthesized particles. Cytotoxicity, cell cycle arrest, ROS generation, and tumor necrosis factor alpha release were related to zinc concentration in PM. Potassium sulfate and potassium carbonate did not induce toxic responses. In light of the provided data, it can be concluded that zinc, enriched in wood combustion emissions, caused the toxicity in all of the measured end points.

Nanosized TiO2 caused minor airflow limitation in the murine airways.

The use of nanotechnology is increasing exponentially, whereas the possible adverse health effects of engineered nanoparticles (NPs) are so far less known. Standardized mouse bioassay was used to study sensory and pulmonary irritation, airflow limitation, and inflammation potency of nanosized TiO(2). Single exposure (0.5 h) to in situ generated TiO(2) (primary particle size 20 nm; geometric mean diameters of 91, 113, and 130 nm at mass concentrations of 8, 20, and 30 mg/m(3), respectively; crystal phase anatase + brookite (3:1)) caused airflow limitation in the conducting airways at each studied exposure concentration, which was shown as a reduction in expiratory flow, being at the lowest 73% of baseline. The response was not dose dependent. Repeated exposures (altogether 16 h, 1 h/day, 4 days/week for 4 weeks) to TiO(2) at mass concentration of 30 mg/m(3) caused as intense airflow limitation effect as the single exposures, and the extent of the responses stayed about the same along the exposure days. Sensory irritation was fairly minor. Pulmonary irritation was more pronounced during the latter part of the repeated exposures compared to the single exposures and the beginning of the repeated exposures. Sensory and pulmonary irritation were observed also in the control group, and, therefore, reaction by-products (NO(2) and C(3)H(6)) may have contributed to the irritation effects. TiO(2) NPs accumulated mainly in the pulmonary macrophages, and they did not cause nasal or pulmonary inflammation. In conclusion, the irritation and inflammation potencies of studied TiO(2) seemed to be low.