Wagner J.,Environmental Health Laboratory Branch
Environmental Sciences: Processes and Impacts | Year: 2015
This work investigates potential analytical variability in environmental investigations of natural occurrences of asbestos (NOA) due to intergrown serpentine minerals. Franciscan complex and serpentinite rock samples were obtained from likely NOA sites in coastal Northern California with geographic information system (GIS) maps, then analyzed using polarized light microscopy (PLM), transmission electron microscopy with energy-dispersive X-ray analysis and selected area electron diffraction (TEM/SAED/EDS), and environmental scanning electron microscopy with EDS (ESEM/EDS). Non-asbestos serpentine fibers were superficially similar to chrysotile but were differentiated quickly using TEM morphology criteria and reference SAED overlays. 94 NOA fibers were classified as asbestiform chrysotile (62%), polygonal serpentine (34%), lizardite scrolls (2%), and lizardite laths (2%). Chrysotile fibril widths (mean = 42 nm) were significantly different from those of polygonal serpentine and lizardite laths (167 and 505 nm, respectively), but not lizardite scrolls (37 nm). Due to differing preparations and microscope resolutions, TEM analyses investigated a distinct, smaller population of particles (0.01-10 μm) than did PLM analyses (10-100 μm). A higher proportion of asbestiform phases in the finer fraction could potentially bias TEM bulk percent asbestos determinations. ESEM/EDS of intermediate particle size ranges revealed 20-200 μm, elongated particles with intermixed asbestiform and non-asbestiform structures on their surfaces. These particles were too thick and complex to be resolved by PLM, and too massive to be detected by TEM. These large particles are likely to exist in samples prepared by mechanical crushing or grinding, but are not likely to be generated by "releasable asbestos" methods. This journal is © The Royal Society of Chemistry 2015.
Guo L.-C.,CAS Guangzhou Institute of Geochemistry |
Guo L.-C.,University of Chinese Academy of Sciences |
Bao L.-J.,CAS Guangzhou Institute of Geochemistry |
She J.-W.,Environmental Health Laboratory Branch |
Zeng E.Y.,CAS Guangzhou Institute of Geochemistry
Atmospheric Environment | Year: 2014
Rainwater samples were simultaneously collected from three locations in Guangzhou, a mega metropolitan center in South China, during the entire year of 2010, and analyzed for particulate matter (PM), total organic carbon and polycyclic aromatic hydrocarbons (PAHs), with the objectives of assessing the seasonality of washout effects and efficiency for removal of pollutants from the atmosphere by wet deposition. The contents of PM, particulate organic carbon, and dissolved organic carbon were in the ranges of 0.74-420 (average: 8.1mgL-1), 0.16-40 (average: 1.3mgL-1), and 0.34-6.9mgL-1 (average: 1.4mgL-1), respectively. Concentrations of σ15PAH (sum of the 16 priority PAH compounds defined by the United States Environmental Protection Agency minus naphthalene) in wet deposition samples ranged from 39 to 1580ngL-1 with an average of 170ngL-1. The PAH concentration levels were slightly abated compared to those acquired previously in Guangzhou during the year of 2005, probably indicating a favorable change of energy consumption patterns in the region. There were moderately significant negative correlations between washout ratios and rainfall intensities (0-4.3mmh-1). The total annual fluxes of wet and dry depositions combined for PM and PAHs in the urban area of Guangzhou were 34gm-2yr-1 and 6.0×102μgm-2yr-1 with 50 and 57% being contributed from wet deposition, respectively. The monthly capacity for removal (CR) of PM and PAHs (calculated as the wet deposition flux dividing the total flux) varied widely with different months, and was lower during the dry weather season (January-March and October-December) than during the wet weather season (April-September). Finally, the air quality index related to PM10 was negatively correlated to CR values of PM and PAHs, indicating the need to control the emissions of anthropogenically derived pollutants during the dry weather season. © 2013 Elsevier Ltd.
Ghosal S.,Environmental Health Laboratory Branch |
MacHer J.M.,Environmental Health Laboratory Branch |
Ahmed K.,University of California at Berkeley
Environmental Science and Technology | Year: 2012
We present an application of Raman microspectroscopy (RMS) for the rapid characterization and identification of individual spores from several species of microfungi. The RMS-based methodology requires minimal sample preparation and small sample volumes for analyses. Hence, it is suitable for preserving sample integrity while providing micrometer-scale spatial resolution required for the characterization of individual cells. We present the acquisition of unique Raman spectral signatures from intact fungal spores dispersed on commercially available aluminum foil substrate. The RMS-based method has been used to compile a reference library of Raman spectra from several species of microfungi typically associated with damp indoor environments. The acquired reference spectral library has subsequently been used to identify individual microfungal spores through direct comparison of the spore Raman spectra with the reference spectral signatures in the library. Moreover, the distinct peak structures of Raman spectra provide detailed insight into the overall chemical composition of spores. We anticipate potential application of this methodology in the fields of public health, forensic sciences, and environmental microbiology. © 2012 American Chemical Society.
Wagner J.,Environmental Health Laboratory Branch |
Naik-Patel K.,Centers for Disease Control and Prevention |
Wall S.,Environmental Health Laboratory Branch |
Harnly M.,Environmental Health Investigations Branch
Atmospheric Environment | Year: 2012
Computer-controlled scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to obtain ambient PM mass concentrations, elemental size distributions, morphologies, and particle types during four Bermuda grass burn events in Imperial Valley, California. Passive PM samplers were deployed to three to six locations surrounding each burn for durations of 24-120 h. Average PM 2.5 and PM 10 levels were modestly but significantly higher at locations less than 3.2 km (two miles) from the nearest burn (n = 37). During one monitored burn, higher winds caused an intense ground-level plume to envelop two samplers mounted on telephone poles very close to the field. For this event, 24-h PM 2.5 exposures downwind were up to 17 times higher than that measured upwind. Particles were classified into five distinct chemical types consistent with local area sources. Burn-related particle types, primarily submicron carbonaceous particles, contributed 95% of the PM 2.5 in the location directly impacted by the ground-level plume, compared to only 12% in the upwind location. Downwind PM 10-2.5 particles were enriched in potassium, phosphorus, chlorine, calcium, silicon, and sulfur, consistent with analyses of bulk and partially-burned Bermuda grass. The accuracy and precision of passive sampler PM measurements were all within 4 μg m -3, though low median values caused high percent differences for PM 2.5. The use of electron microscopy and passive sampling in this study enabled detailed PM characterizations, spatial comparisons, and rapid deployment in often dynamic sampling scenarios. © 2012 Elsevier Ltd.
Mendell M.J.,Environmental Health Laboratory Branch |
Mendell M.J.,Lawrence Berkeley National Laboratory |
Mirer A.G.,University of Wisconsin - Madison |
Cheung K.,Massey University |
And 2 more authors.
Environmental Health Perspectives | Year: 2011
OBjectives: Many studies have shown consistent associations between evident indoor dampness or mold and respiratory or allergic health effects, but causal links remain unclear. Findings on measured microbiologic factors have received little review. We conducted an updated, comprehensive review on these topics. D ata sources: We reviewed eligible peer-reviewed epidemiologic studies or quantitative meta-analyses, up to late 2009, on dampness, mold, or other microbiologic agents and respiratory or allergic effects. D ata extraction: We evaluated evidence for causation or association between qualitative/subjective assessments of dampness or mold (considered together) and specific health outcomes. We separately considered evidence for associations between specific quantitative measurements of microbiologic factors and each health outcome. D ata synthesis: Evidence from epidemiologic studies and meta-analyses showed indoor dampness or mold to be associated consistently with increased asthma development and exacerbation, current and ever diagnosis of asthma, dyspnea, wheeze, cough, respiratory infections, bronchitis, allergic rhinitis, eczema, and upper respiratory tract symptoms. Associations were found in allergic and nonallergic individuals. Evidence strongly suggested causation of asthma exacerbation in children. Suggestive evidence was available for only a few specific measured microbiologic factors and was in part equivocal, suggesting both adverse and protective associations with health. C onclusions: Evident dampness or mold had consistent positive associations with multiple allergic and respiratory effects. Measured microbiologic agents in dust had limited suggestive associations, including both positive and negative associations for some agents. Thus, prevention and remediation of indoor dampness and mold are likely to reduce health risks, but current evidence does not support measuring specific indoor microbiologic factors to guide health-protective actions.