Effect of Söderberg smelting technology, anode paste composition, and work shift on the relationship between benzo[a]pyrene and individual polycyclic aromatic hydrocarbons.

This follow-up study of Farant and Gariepy study investigates the relationship between benzo[a]pyrene (B[a]P) and other polycyclic aromatic hydrocarbons (PAHs) found in coal tar pitch volatiles in two types of Soderberg aluminum smelters-horizontal and vertical stud. The study confirms the strong relationships between B[a]P and total PAHs, and that B[a]P was a good indicator for other PAHs in this industry. The PAH profiles were consistent within each smelter, but the smelter technology used and the changes in the raw material formulation resulted in significantly different profiles. B[a]P toxic equivalency factors for emitted PAH mixtures were greater in the horizontal stud smelter than in the vertical stud smelter. Overall, this study illustrates the potential usefulness of B[a]P relative abundance ratios to simplify exposure assessment in the workplace and reduce associated costs.

Performance of small evacuated canisters equipped with a novel flow controller for the collection of personal air samples.

Small evacuated canisters have become more common in industrial hygiene personal sampling in recent years. The smaller canisters necessitate a low flow rate to ensure a full-shift air sample can be collected. Evaluation of small evacuated canisters compared to sorbent sampling methods is essential to ensure that the canisters accurately monitor airborne contamination. This data, in a controlled environment, will provide practitioners with valuable reference information when considering air-sampling campaigns. Six 300-mL evacuated canisters were used to collect 6-hour breathing zone samples of styrene on volunteers in a large exposure chamber. The canisters were specially designed with a capillary flow controller developed at McGill University in the mid-1990s. Based on the geometry of the capillary the airflow into the canisters was controlled to a low flow rate, approximately 0.3 mL/min. This low sampling flow rate allowed for the use of small-volume canisters as personal samplers to collect styrene vapors. Charcoal tubes and diffusive badges were simultaneously used to collect side-by-side samples for comparison. In addition, an online gas chromatograph (GC) documented the concentration in the chamber throughout the duration of the exposure. The three methods did not disclose any significant statistical difference when compared to the online GC values and to each other. In addition, linear regression analysis between the charcoal tubes and the canisters resulted in a correlation (R(2) > 0.95). An evaluation of the bias and precision (overall uncertainty) of the capillary-canister method, charcoal tubes, and diffusive badges found them to be within criteria established by European Committee for Standardization 482. The results indicate that the capillary-canister sampling device can be an acceptable alternative to sorbent samplers as a personal sampler providing reliable results that are representative of exposures.

A novel personal air sampling device for collecting volatile organic compounds: a comparison to charcoal tubes and diffusive badges.

Evacuated canisters have been used for many years to collect ambient air samples for gases and vapors. Recently, significant interest has arisen in using evacuated canisters for personal breathing zone sampling as an alternative to sorbent sampling. A novel flow control device was designed and built at McGill University. The flow control device was designed to provide a very low flow rate, <0.5 mL/min, to allow a sample to be collected over an extended period of time. Previous experiments run at McGill have shown agreement between the mathematical and empirical models to predict flow rate. The flow control device combined with an evacuated canister (capillary flow control-canister) was used in a series of experiments to evaluate its performance against charcoal tubes and diffusive badges. Air samples of six volatile organic compounds were simultaneously collected in a chamber using the capillary flow control-canister, charcoal tubes, and diffusive badges. Five different concentrations of the six volatile organic compounds were evaluated. The results from the three sampling devices were compared to each other and to concentration values obtained using an online gas chromatograph (GC). Eighty-four samples of each method were collected for each of the six chemicals. Results indicate that the capillary flow control-canister device compares quite favorably to the online GC and to the charcoal tubes, p > 0.05 for most of the tests. The capillary flow control-canister was found to be more accurate for the compounds evaluated, easier to use, and easier to analyze than charcoal tubes and passive dosimeter badges.

Photochemical degradation of selected nitropolycyclic aromatic hydrocarbons in solution and adsorbed to solid particles.

To examine the relationship between the nitro group orientation and photochemical degradation, a series of NPAHs, including 6-nitrochrysene, 9-nitroanthracene and 6-nitrobenzo(a)pyrene were irradiated both dissolved in CH3CN and adsorbed onto a surface (alumina, silica, carbon and cellulose). In solution, not all NPAHs displayed a relationship between their relative and nitro group orientation. In the adsorbed state, the nature of the particle appeared to have more of an influence than did the structure of the NPAH. If the compound degraded, the main product was generally a quinone.

Development of a flow controller for long-term sampling of gases and vapors using evacuated canisters.

Anthropogenic activities contribute to the release of a wide variety of volatile organic compounds (VOC) into microenvironments. Developing and implementing new air sampling technologies that allow for the characterization of exposures to VOC can be useful for evaluating environmental and health concerns arising from such occurrences. A novel air sampler based on the use of a capillary flow controller connected to evacuated canisters (300 mL, 1 and 6 L) was designed and tested. The capillary tube, used to control the flow of air, is a variation on a sharp-edge orifice flow controller. It essentially controls the velocity of the fluid (air) as a function of the properties of the fluid, tube diameter and length. A model to predict flow rate in this dynamic system was developed. The mathematical model presented here was developed using the Hagen-Poiseuille equation and the ideal gas law to predict flow into the canisters used to sample for long periods of time. The Hagen-Poiseuille equation shows the relationship between flow rate, pressure gradient, capillary resistance, fluid viscosity, capillary length and diameter. The flow rates evaluated were extremely low, ranging from 0.05 to 1 mL min(-1). The model was compared with experimental results and was shown to overestimate the flow rate. Empirical equations were developed to more accurately predict flow for the 300 mL, 1 and 6 L canisters used for sampling periods ranging from several hours to one month. The theoretical and observed flow rates for different capillary geometries were evaluated. Each capillary flow controller geometry that was tested was found to generate very reproducible results, RSD < 2%. Also, the empirical formulas developed to predict flow rate given a specified diameter and capillary length were found to predict flow rate within 6% of the experimental data. The samplers were exposed to a variety of airborne vapors that allowed for comparison of the effectiveness of capillary flow controllers to sorbent samplers and to an online gas chromatograph. The capillary flow controller was found to exceed the performance of the sorbent samplers in this comparison.

Investigation of the presence of amino and nitro polycyclic aromatic hydrocarbons in a Söderberg primary aluminum smelter.

An excessive risk of bladder cancer among Söderberg primary aluminum smelter potroom workers has been reported by several authors, and to date, a causal agent has not been identified. Certain nitro and amino polycyclic aromatic hydrocarbons (PAHs) are either known or suspected human bladder carcinogens, and their presence in this work environment would be cause for concern. In fact, one of these, 2-aminonaphthalene, has been found in both the air and the coal tar pitch used to fabricate process electrodes following an investigation in a Söderberg plant. During the present study, monitoring was conducted in a primary Söderberg aluminum smelter over a 3-week period using novel methods having very good specificity, reproducibility, and sensitivity. Results indicated that 1-aminonaphthalene and 2-aminonaphthalene and 1-nitronaphthalene and 2-nitronaphthalene were present at low parts-per-million levels in the coal tar pitch used to prepare the process electrodes. 1-aminonaphthalene and 2-aminonaphthalene were measured 40 cm above the electrolytic cells on days 1 and 2 of the investigation when the cells' ventilation systems had been shut down for repairs and maintenance. 2-aminonaphthalene was measured at concentrations ranging from 0.080 to 0.350 microg/m3. 1-nitronaphthalene and 2-nitronaphthalene, predominant in coal tar pitch, were not detected in any of the 43 air samples collected. A plausible explanation is their reduction to their respective amine during the electrolytic process. The routine screening of coal tar pitch used to prepare the process's electrode for both amino and nitro PAHs should be adopted by the aluminum industry as an effective means of controlling the presence of these carcinogenic pollutants in their workplace.