James S. Webber

Mn/V ratio as a tracer of aerosol sulfate transport

Abstract Concentrations of SO 4 2− , Al, V and Mn were determined in airborne particles during July-August 1981 at five sites in New York State: for 6-h intervals at Mayville, Brewerton and Whiteface Mountain and for 24-h intervals at Oneonta and West Haverstraw. Episodic high [SO 4 2− ] were observed during 18–21 and 24–26 July and 1–4 August. Air trajectories showed that during the 18–21 July and 1–4 August episodes peak [SO 4 2− ] coincided with slow-moving air masses which had spent 1 or more days in the midwestern states of Indiana, Michigan, Ohio or Pennsylvania prior to entering New York. During the episodes [SO 4 2− ] decreased from west to east. No significant local sources of SO 4 2− exist at the 6-h sites. All these lines of evidence together show that during these episodes SO 4 2− were transported from the industrial Midwest. During the 24–26 July episode, peak [SO 4 2− ] at Mayville coincided with air masses entering the state from Ohio, but at Brewerton and Whiteface Mountain the highest [SO 4 2− ] occurred when air masses came from metropolitan New York City and the mid-Atlantic states. The average [SO 4 2− ] at Mayville were 2-fold higher than at Brewerton and Whiteface Mountain. The average manganese/vanadium ratio (Mn/V) in aerosols from the Midwest (1–10) has been suggested to be ~ 10 times that in the Northeast ( 4 2− ] were due to transport from the Midwest. On 25–26 July the average Mn/V was high at Mayville (2.8) but low at Brewerton (0.29) and Whiteface Mountain (

Asbestos-contaminated drinking water: its impact on household air

Asbestos contamination in excess of 10 billion fibers per liter was detected in a communitys drinking water. To assess the possibility of waterborne asbestos becoming airborne, air samples were collected from impacted houses receiving contaminated water from three control houses. Collected within each house were three samples on 0.6-micrometer-pore Nuclepore filters and three samples on 0.8-micrometer-pore Millipore filters. In addition, bulk samples of suspect material and water samples were collected. Mean waterborne asbestos concentrations were 24 million fibers per liter (MFL) in the impacted houses versus only 1.1 MFL in the control houses. Transmission electron microscopy revealed that airborne asbestos concentrations were highest in impacted houses, with airborne asbestos concentrations positively correlated with waterborne concentrations. For fiber and mass measurements on both filter types, airborne asbestos concentrations were significantly higher in the impacted houses: mean concentrations in impacted houses were 0.12 fibers/cm3 and 1.7 ng/m3 on Nuclepore filters and 0.053 fibers/cm3 and 2.3 ng/m3 on Millipore filters versus only 0.037 fibers/cm3 and 0.31 ng/m3 on Nuclepore filters and 0.0077 fibers/cm3 and 0.14 ng/m3 on Millipore filters from control houses. Also detected in the air samples from impacted houses were clusters of chrysotile, often with several hundreds of fibers. When estimates of these individual fibers were added to the total fiber count, the difference between the impacted and control houses became even greater. The increased concentrations in impacted houses were due primarily to short (less than 1 micrometer) fibers. Bulk samples did not reveal likely materials within the impacted houses to account for these differences. Thus high levels of waterborne asbestos were apparently the source of increased concentrations of airborne asbestos within these houses.

Identification of submicrometer coal fly ash in a high-sulfate episode at Whiteface Mountain, New York

Abstract The most direct evidence yet of a coal-burning source of a high-sulfate air mass reaching the Northeast has been detected in a brief episode at Whiteface Mountain, NY, on 23 June 1983. Individual microparticles were characterized by electron microscopy in three samples from this period: 12 h before the SO2−4 peak ( [SO 2− 4 ] = 2.7 μg m −3 ), during the peak (24 μg m −3) and 12 h after the peak (2.2 μg m −3). This analysis provided the first confirmation of the association of coal fly ash and high [SO2−4] at a rural acid-stressed site. Common at the time of peak [SO 2−4] were sub-μm magnetite and glass spheres as identified by morphology, elemental composition and mineralogy. This coal fly ash was essentially absent 12 h before or 12 h after the episode. A midwestern source of this episode was indicated by Mn/V ratios and by meteorologic conditions.

Performance of Membrane Filters Used for TEM Analysis of Asbestos

This article presents findings related to characteristics of membrane filters that can affect the recovery of asbestos and the quality of preparations for transmission electron microscopy (TEM) analysis. Certain applications and preparation steps can lead to unacceptable performance of membrane filters used in analysis of asbestos by TEM. Unless substantial care is used in the collapsing of mixed-cellulose ester (MCE) filters with an acetone hot block, grid preparations can suffer and fiber recoveries can be compromised. Calibration of the etching depth of MCE filters, especially at differing locations in an ashers chamber, is critical for reliable fiber recovery. Excessive etching of MCE filters with aerosol-deposited asbestos can lead to loss of short fibers, while insufficient etching of MCE filters with aqueous-deposited asbestos can, paradoxically, also lead to loss of short fibers. Interlaboratory precision on MCE filters is improved by aerosol-deposited asbestos, as opposed to aqueous deposition. In comparison, straightforward preparation, improved solvents, and reduced contamination make PC filters an increasingly acceptable alternative. Variations in the geometric configuration during application of carbon films can lead to fiber loss and unacceptable grid quality for either type of filter.

Asbestos in water

Abstract Asbestos is not uncommon in water, usually originating from asbestos‐cement pipes or asbestos‐containing aquifers. Although asbestos concentrations are typically less than one million fibers per liter, concentrations have occasionally exceeded one billion fibers per liter. Some epi‐demiological and laboratory‐animal studies have revealed an association of asbestos ingestion with various types of cancer, while other studies have not. Ingested asbestos, usually short fibers, is capable of penetrating the intestinal wall and being eliminated in urine or accumulating in various tissues and organs. Elevated asbestos concentrations have recently been detected in colon cancers of asbestos workers. Drinking‐water systems should attempt to minimize asbestos concentrations by focusing on actual or potential sources of asbestos. Transmission electron microscopy is the analytical method of choice but revisions are needed in the U.S. method to accommodate recently promulgated drinking‐water standards. Laborat...

Quantitating Asbestos Content in Friable Bulk Samples: Development of a Stratified Point-Counting Method

Intralaboratory and interlaboratory investigations were used to evaluate the precision and accuracy of point counting versus visual estimation of asbestos in friable bulk materials. Interlaboratory analyses revealed that the commonly used “equivalent” visual-estimation methods were significantly less accurate than the Environmental Protection Agency (EPA) 400-point-count method, especially at low asbestos concentrations. In an effort to produce a method that is statistically “equivalent” yet less time consuming than the EPA method, several strategies were assessed to reduce preparation and analysis time. False negatives were produced by schemes that unconditionally reduced the number of slides/points analyzed. The best modification was a stratified scheme in which effort was inversely proportional to the Percentage of asbestos in a sample, Although precision was sacrificed at higher concentrations, that precision was deemed superfluous because such materials were categorically asbestos-containing material...

Using Microparticle Characterization to Identify Sources of Acid-Rain Precursors Reaching Whiteface Mountain, New York

This chapter is largely an elaboration of a paper which was presented at the Forensic, Occupational and Environmental Health Symposium at the 1985 joint national meetings of the Electron Microscopy Society of America and the Microbeam Analysis Society in Louisville, Kentucky. An extended abstract of that presentation has been published by San Francisco Press.1

Amphibole Asbestos in Tree Bark—A Review of Findings for This Inhalational Exposure Source in Libby, Montana

In June 2009, the U.S. Environmental Protection Agency (EPA) designated the town of Libby, Montana, a public health emergency—the first and only time the EPA has made such a determination under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). From about 1920 until 1990, the leading source of vermiculite ore for the United States and the world was from a mine near Libby. This vermiculite ore was contaminated with fibrous and asbestiform amphibole in veins throughout the deposit. Today, areas surrounding the abandoned vermiculite processing/mining facilities and much of the town of Libby are contaminated with these asbestos fibers, contributing to an outbreak of asbestos-related diseases in the Libby population. Trees in Libby and in forested areas surrounding the abandoned mine have accumulated amphibole asbestos fibers on their bark surface, providing for inhalational exposures. Several studies have been conducted to further understand this exposure pathway. To address exposures to the public, Libby amphibole (LA) was measured in personal breathing zone and Tyvek surface wipe samples collected during firewood harvesting simulations, as well as in the ash and emissions of woodstoves when amphibole-contaminated firewood was combusted. Occupational studies simulating wildland firefighting and routine U.S. Department of Agriculture (USDA) Forest Service activities have also been conducted in the forested areas surrounding the abandoned mine, demonstrating the potential for inhalational exposures during common regional workplace activities. We present a review of the findings of this emerging environmental health concern impacting not only the residents of Libby but applicable to other populations living near asbestos-contaminated areas.

Quality-control testing for asbestos analysis with synthetic bulk samples

Asbestos-containing bulk samples which are routinely synthesized in the laboratory from known masses of readily available materials are part of an internal quality-control testing program. Quantitative analysis of asbestos in these samples by a laboratorys standard procedure yields precision and accuracy of that procedure. Permanent microscope-slide preparations of these samples are used specifically to assess polarized-light microscopic (PLM) analyses. Archives of these samples become references for field samples and allow determination of long-term precision and accuracy. The reliability of a two-step PLM method is determined by the above method.

Evidence and Reconstruction of Airborne Asbestos From Unconventional Environmental Samples

The understanding of historical ambient asbestos concentrations is critical to exposure mapping and retrospective health impact studies involving asbestos related diseases. Two presentations at the University of Montana Center for Environmental Health Sciences Asbestos Conference (July 28, 2005) introduced novel methods for detecting evidence of past airborne asbestos contamination. In each of these studies, transmission electron microscopy was used to identify and measure asbestos fibers collected in samples from unconventional environmental sources. In the first study, paleolimnology, analytical transmission electron microscopy, particle-separation techniques, and empirical aerosol-sediment modeling were combined to provide the first measurements of airborne asbestos concentrations prior to the 1980s. In an upstate New York study area, airborne concentrations of chrysotile followed its 20th-century usage, with highest concentrations near mid-century (∼0.1 fibers/cm3), followed by a decrease in the last quarter century. Airborne concentrations of anthophyllite asbestos (a contaminant from nearby talc mines and mills) increased from <0.004 to 0.022 fibers/cm3 from 1847 to 1995. In the second study, tree bark and core samples were collected from areas near the asbestos-contaminated vermiculite mine in Libby, MT. We originally hypothesized that trees in the areas surrounding the mine could serve as reservoirs for ambient amphibole fibers. Though gravimetric reduction of a tree core sample did not indicate the presence of amphibole fibers, transmission electron microscopy analysis of bark samples yielded substantial amphibole fiber concentrations ranging from 14 to 260 million amphibole fibers/cm2. Based on these preliminary results, we conclude that trees in the Libby valley can serve as reservoirs for amphibole fibers, and that a continued potential for exposure exists for those who harvest contaminated wood.