Halet G. Poovey

Field Performance of the RespiConTMfor Size-Selective Sampling of Industrial Wood Processing Dust

The RespiConTMsampler is a multistage virtual impactor that simultaneously collects the ISO/CEN/ACGIH size fractions of inhalable, thoracic, and respirable particulate matter. The field performance of the device for measurement of industrial wood processing dust was evaluated against reference size-selective samplers: the IOM sampler (inhalable dust), the GK 2.69 cyclone (thoracic dust), and the SKC aluminum cyclone (respirable dust). Seventy-one sets of area samples were collected from 10 wood processing plants, with the samplers mounted either in the free-field or on a two-dimensional “bluff body.” The geometric mean (range) dust levels across all plants measured by the reference samplers were: inhalable, 1.35 mg/ m3(0.11–11.06); thoracic, 0.31 mg/m3(0.05–1.38); and respirable, 0.10 mg/m3(0.02–0.54). In comparing the RespiCon with the reference samplers, there was no significant difference between sampling in the free-field versus bluff-body modes. For inhalable dust, there was no significant difference between the RespiCon and the IOM sampler after applying a correction factor of 1.5× to the extrathoracic data obtained from the RespiCon. Without the correction factor, the RespiCon undersample inhalable dust by an average of 23%. For thoracic dust, the RespiCon was shown to oversample the extrathoracic dust fraction resulting in an overall error of 48%. A simple correction based on the inhalable and thoracic dust levels reported by the RespiCon is proposed. For respirable dust, there was a significant difference between the RespiCon and the SKC cyclone, but the data were equivocal due to imprecision in measurement of the low respirable dust concentrations encountered and the likelihood of bias in the reference sampler. Overall, the RespiCon sampler appears to be a suitable size-selective sampling device for industrial wood processing dust, although adjustments should be made to the inhalable and thoracic dust results.

Pulmonary toxicity of polymeric hexamethylene diisocyanate aerosols in mice

The acute pulmonary response of male C57BL/6 mice exposed to respirable polymeric hexamethylene diisocyanate biuret trimer aerosol (HDI-BT), a component of polyurethane spray paints, was examined. Mice were exposed to concentrations of 1 and 10 mg/m(3) HDI-BT for 5 h and were evaluated 6, 18, 42, 90, 186, and 378 h after the end of exposure. Mice exposed to 1 or 10 mg/m(3) HDI-BT exhibited dose-dependent lung function impairment, edema, neutrophilic inflammation, cellular proliferation, and histologic lesions in terminal bronchioles and alveolar ducts. Impairment of pulmonary function, indicated by decreased frequency and increased enhanced pause (Penh), was maximal immediately after exposure and progressively recovered at later time points. Lung weight and lavage fluid protein content peaked at 6 and 18 h after exposure, respectively. Total cells and macrophages recovered in lavage fluid peaked 90 h after exposure. Neutrophils recovered in lavage fluid peaked between 18 and 42 h after exposure. Proliferative lesions, as identified histologically and by bromodeoxyuridine incorporation, were maximal 90 h after exposure. In contrast, no inflammatory cell influx, protein leakage, or lung pathology were observed in mice exposed to 360 ppb HDI monomer vapor. This model will be useful for investigating molecular mechanisms by which HDI-BT causes lung injury, which is known to occur in humans exposed occupationally to this pulmonary toxicant.

An HDI polyisocyanate aerosol exposure system for large-scale animal experiments.

An exposure system that allows large-scale exposure of animals to 1,6-hexamethylene diisocyanate (HDI)-based polyisocyanates at a stable concentration and aerosol size distribution was developed. The HDI polyisocyanate aerosol is generated by nebulizing a solution of a commercial polyisocyanate product dissolved in acetone. The aerosol is delivered with a constant airflow into a horizontal flow chamber. Complete mixing of aerosol in the chamber is ensured by a circulating fan. This method has been used to generate atmospheres containing HDI polyisocyanates at a concentration of 10.46+/-0.23 mg/m(3) over a 5-hour period. The overall mass median aerodynamic equivalent diameter was found to be 1.42 microm with a geometric standard deviation of 1.26. The HDI monomer concentration was 0.15+/-0.04 mg/m(3). The average chamber acetone concentration was determined to be 2481+/-222 ppm (mean+/-standard deviation). Different HDI polyisocyanate concentrations in the chamber can be achieved by altering the concentration of the commercial polyisocyanate product in acetone and the chamber flow rate. The described exposure system will be useful for performing toxicological studies involving HDI polyisocyanates.

On-filter determination of collected wood dust by diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS)

A new analytical technique based on DRIFTS spectroscopy has been developed for the specific and sensitive determination of size-fractionated wood dust from 37 mm glass fiber filter samples collected with the Respicon sampler. A translational diffuse reflectance apparatus was modified to accept filter samples by incorporating a special filter holder in the sample stage and a clockwork motor to drive the translational stage during infrared scanning, thus providing an average analysis across the filter face. Filter samples were pre-treated with ethyl acetate to uniformly redeposit dust onto the filter and extract potential chemical interferences. Two absorbance maxima (1251 and 1291 cm(-1)), corresponding to the cellulose content of the wood, were suitable for quantitation of wood dust. Analysis of seven species of wood at 1291 cm(-1) showed an equivalent quantitative response for all species except maple. The response at 1251 cm(-1) was more variable across species but more sensitive for the softwoods. There was a statistically significant effect of particle size on the analytical response, so that analytical standards should be matched to the samples in terms of particle size distribution. Analytical limit of detection was approximately 0.08 mg of wood dust per sample with overall precision of about 6%. Comparison of DRIFTS and gravimetric analyses of 51 pure wood dust samples ranging from about 0.2 to 2 mg yielded a slope of 1.08 and r2 equal to 0.9. Other particulate contaminants common in the industrial wood processing industry showed little or no interference with the determination of wood dust by this method.

Determination of Carbon Monoxide with a Modified Zeolite Sorbent and Methanization-Gas Chromatography

The purpose of this study was to develop an alternative sorbent sampling technique to concentrate CO from an air sample for subsequent instrumental analysis. Y52 zeolite doped with 9.4 wt % cuprous ions was found to have high capacity, stability to air, and thermal reversibility for CO. The Cu(I)-modified zeolite was packed in glass tubes, preceded by a drying tube containing silica gel. Air was sampled through the tubes at the flow rate of 100 mL/min. Collected CO was thermally desorbed at 300 degrees C and determined by gas chromatography with reduction of CO to methane and flame ionization detection (TD-GC-CH4-FID). Breakthrough capacity of the sorbent was found to be 2.74 mg CO per gram of sorbent. For 2-L air samples containing 12.5 to 100 ppm CO and 50% relative humidity at room temperature, recovery of CO was found to be 96.6% with pooled relative standard deviation of 5.8%. The estimated detection limit for a 2-L sample was 0.2 ppm. Collected CO was stable at room temperature for 1 day and up to 7 days at 4 degrees C if the sorbent tube was flushed with helium before storage. In field testing, the ratio of CO measured by the new technique and by a reference technique was found to be 0.93 with pooled relative standard deviation of 6.3%. This unique new sorbent coupled with TD-GC-CH4-FID shows promise as a sensitive and specific alternative for measurement of CO in air.

Collection of Airborne Free Chlorine on a Bromide/2,6-Dimethylphenol-Coated Solid Sorbent with Chromatographic Determination

Abstract A new solid sorbent has been developed that is suitable for personal monitoring of exposure to chlorine. The sorbent was prepared from silica gel coated with 2,6-dimethylphenol (DMP), sodium bromide, and sulfuric acid. Chlorine oxidizes bromide to bromine, which then brominates DMP to form 4-bromo-2,6-dimethylphenol (BDMP) through electrophilic aromatic substitution. The direct reaction of chlorine with DMP to form 4-chloro-2,6-dimethylphenol was found to be unsuitable due to competing reactions. BDMP was desorbed with methanol and determined by gas chromatography (GC) with flame ionization detection or high-performance liquid chromatography (HPLC) with ultraviolet absorbance detection. Recovery of collected chlorine as BDMP was quantitative from 0.05 to at least 2 ppm for 20-L air samples, and precision and accuracy were within National Institute for Occupational Safety and Health guidelines. Limits of detection for a 20-L air sample were approximately 10 ppb chlorine, when analyzed by either GC...