Suchergebnisse

The potential for para‐occupational (or take‐home) exposures from contaminated clothing has been recognized for the past 60 years. To better characterize the take‐home asbestos exposure pathway, a study was performed to measure the relationship between airborne chrysotile concentrations in the workplace, the contamination of work clothing, and take‐home exposures and risks. The study included air sampling during two activities: (1) contamination of work clothing by airborne chrysotile (i.e., loading the clothing), and (2) handling and shaking out of the clothes. The clothes were contaminated at three different target airborne chrysotile concentrations (0–0.1 fibers per cubic centimeter [f/cc], 1–2 f/cc, and 2–4 f/cc; two events each for 31–43 minutes; six events total). Arithmetic mean concentrations for the three target loading levels were 0.01 f/cc, 1.65 f/cc, and 2.84 f/cc (National Institute of Occupational Health and Safety [NIOSH] 7402). Following the loading events, six matched 30‐minute clothes‐handling and shake‐out events were conducted, each including 15 minutes of active handling (15‐minute means; 0.014–0.097 f/cc) and 15 additional minutes of no handling (30‐minute means; 0.006–0.063 f/cc). Percentages of personal clothes‐handling TWAs relative to clothes‐loading TWAs were calculated for event pairs to characterize exposure potential during daily versus weekly clothes‐handling activity. Airborne concentrations for the clothes handler were 0.2–1.4% (eight‐hour TWA or daily ratio) and 0.03–0.27% (40‐hour TWA or weekly ratio) of loading TWAs. Cumulative chrysotile doses for clothes handling at airborne concentrations tested were estimated to be consistent with lifetime cumulative chrysotile doses associated with ambient air exposure (range for take‐home or ambient doses: 0.00044–0.105 f/cc year).

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 mu m images. At the simplest level, we distinguish five environments: centres, bars, spiral arms, interarm regions, and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, which are publicly released but not explicitly used in this paper. We examine trends with environment in the molecular gas content, star formation rate, and depletion time using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals clearly dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties and without significant slope differences among environments. In contrast to what has been suggested by early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle. ; Instituto de Salud Carlos III Spanish Government PID2019-106027GA-C44 European Research Council (ERC) 694343 National Science Foundation (NSF) National Research Foundation of Korea 1615105 1615109 1653300 National Aeronautics and Space Administration (NASA) under ADAP grants NNX16AF48G NNX17AF39G German Research Foundation (DFG) SFB 881 138713538 Heidelberg Cluster of Excellence "STRUCTURES" in the framework of Germany's Excellence Strategy EXC-2181/1 390900948 European Research Council via the ERC Synergy Grant "ECOGAL" 855130 SKA South Africa 694343 721463 726384/Empire Academy of Finland 297738 German Research Foundation (DFG) KR4801/1-1 KR4598/2-1 KR4801/2-1 BI1546/3-1 European Research Council (ERC) 714907 National Science Foundation (NSF) 1903946 Spanish Government AYA2016-79006-P Spanish Government European Commission PID2019-108765GB-I00 Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU INP IN2P3 French Atomic Energy Commission Centre National D'etudes Spatiales Programme National 'Physique et Chimie du Milieu Interstellaire' (PCMI) of CNRS/INSU INC/INP - CEA Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2017-03987 Spanish funding grant (MINECO/FEDER) AYA2016-79006-P Spanish funding grant (MCIU/AEI/FEDER) PGC2018-094671-B-I00 Spanish funding grant (MICINN) PID2019-108765GB-I00 German Research Foundation (DFG) 138713538 - SFB 881 ; Versión sometida a revisión - Preprint