Alexander W. Teass

Effect of inhaled crystalline silica in a rat model: time course of pulmonary reactions.

Numerous investigations have been conducted to elucidate mechanisms involved in the initiation and progression of silicosis. However, most of these studies involved bolus exposure of rats to silica, i.e. intratracheal instillation or a short duration inhalation exposure to a high dose of silica. Therefore, the question of pulmonary overload has been an issue in these studies. The objective of the current investigation was to monitor the time course of pulmonary reactions of rats exposed by inhalation to a non-overload level of crystalline silica. To accomplish this, rats were exposed to 15 mg/m3 silica, 6 h/day, 5 days/week for up to 116 days of exposure. At various times (5–116 days exposure), animals were sacrificed and silica lung burden, lung damage, inflammation, NF-κB activation, reactive oxygen species and nitric oxide production, cytokine production, alveolar type II epithelial cell activity, and fibrosis were monitored. Activation of NF-κB/DNA binding in BAL cells was evident after 5 days of silica inhalation and increased linearly with continued exposure. Parameters of pulmonary damage, inflammation and alveolar type II epithelial cell activity rapidly increased to a significantly elevated but stable new level through the first 41 days of exposure and increased at a steep rate thereafter. Pulmonary fibrosis was measurable only after this explosive rise in lung damage and inflammation, as was the steep increase in TNF-α and IL-1 production from BAL cells and the dramatic rise in lavageable alveolar macrophages. Indicators of oxidant stress and pulmonary production of nitric oxide exhibited a time course which was similar to that for lung damage and inflammation with the steep rise correlating with initiation of pulmonary fibrosis. Staining for iNOS and nitrotyrosine was localized in granulomatous regions of the lung and bronchial associated lymphoid tissue. Therefore, these data demonstrate that the generation of oxidants and nitric oxide, in particular, is temporally and anatomically associated with the development of lung damage, inflammation, granulomas and fibrosis. This suggests an important role for nitric oxide in the initiation of silicosis.

TIME COURSE OF PULMONARY RESPONSE OF RATS TO INHALATION OF CRYSTALLINE SILICA: NF-kappa B ACTIVATION, INFLAMMATION, CYTOKINE PRODUCTION, AND DAMAGE

In vitro studies suggest that silica-induced lung disease may be linked to processes regulated by nuclear factor- κ B (NF- κ B) activation, but this has not been examined in vivo. Rats were exposed to a silica aerosol of 15 mg/m 3 (6 h/day, 5 days/wk) for 116 days, and bronchoalveolar lavage (BAL) was conducted at various times during the exposure. Silica-induced pulmonary inflammation and damage were determined by measuring BAL cell differentials and first BAL fluid lactate dehydrogenase (LDH) activity and serum albumin concentrations, respectively. NF- κ B activation and production of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) by BAL cells were also measured. The results demonstrate that NF- κ B activation occurred after 5 days exposure, and continued to increase thereafter. BAL cell production of IL-1 and TNF-α had increased incrementally by 10 and 30 days of exposure, respectively. This elevation continued through 79 days of exposure before further increasing at 116 days of exposure. Pulmonary inflammation and damage in silica-exposed rats were also significantly elevated at 5 days of exposure, further increased at a slow rate through 41 days of exposure, and dramatically increased thereafter. Taken together, the results indicate that the initial molecular response of NF- κ B activation in BAL cells occurs in response to low levels of silica deposition in the lung and increases more rapidly versus exposure duration than silica-induced pulmonary inflammation, cellular damage, and cytokine production by BAL cells. This suggests that NF- κ B activation in BAL cells may play an important role in the initiation and progression of silica-induced pulmonary inflammation, cellular damage, and fibrosis.

A Biological Monitoring Method for o-Toluidine and Aniline in Urine Using High Performance Liquid Chromatography with Electrochemical Detection

Abstract A urinalysis method for o-toluidine and aniline was developed for biological monitoring. Urine specimens were made 4.7 M in sodium hydroxide and heated at 80°C for 2 hours to convert the metabolites acetanilide and N-acetyl-o-toluidine to the free amines. Extraction of the hydrolysate with butyl chloride and back extraction with 0.1 M aqueous hydrochloric acid gave an amine fraction, which was subjected to paired-ion reversed-phase liquid chromatography with coulometric electrochemical detection. For o-toluidine and aniline, respectively, the average recovery was 91 and 100 percent, the precision for field specimens was 13 and 16 percent relative standard deviation, and the limit of detection was 0.6 and 1.4 μg/L. This method was applied to 171 urine specimens from chemical plant workers. The median levels for o-toluidine were: exposed preshift, 11 μg/L; exposed postshift, 65 μg/L; nonexposed preshift, 0.7 μg/L; non-exposed postshift, 2.6 μg/L. For aniline the median levels were: exposed preshift...

The Determination in Air of Selected Low-Molecular Weight Aldehydes as Their Oxazolidines by Capillary Gas Chromatography

Abstract The sampling of 2-furaldehyde, pentanedial, and pentanal from air has been accomplished using sorbent tubes containing 120-mg and 60-mg beds of XAD-2 coated with 10 percent 2-(hydroxymethyl)piperidine. Samples were collected at ca. 50 cm3/min for a maximum of 4 hours for 2-furaldehyde, ca. 80 cm3/min for a maximum of 8 hours, or ca. 200 cm3/min for minimum of 15 minutes for pentanedial and ca. 40 cm3/min for a maximum of 4 hours for pentanal. The oxazolidines, formed by reaction of the 2-(hydroxymethyl)piperidine with the aldehydes, were desorbed from the sorbent with 2 ml of toluene. Recovery from the sorbent was essentially quantitative for the aldehydes, and the resulting solution was analyzed by gas chromatography using a fused-silica capillary DB-5 column. Typical limits of detection ranged from 0.2–0.6 μg/sample for 2-furaldehyde, pentanedial, and pentanal. Pooled relative standard deviations for sets of 18 samples were 7.6 percent (3–41 mg/m3) for 2-furaldehyde, 8.7 percent (1–8 mg/m3) for...

Investigation of the Inaccuracy of NIOSH Method 5505 for Estimating the Concentration of Isocyanate in Air

Abstract NIOSH Method 5505 for estimating isocyanate in workplace air is based on sampling air with an impinger containing a standard solution of 1-(2-methoxyphenyl)piperazine in toluene and relating the measured loss of reagent from the sample to the total quantity of isocyanate trapped from the air. An experiment, in which 0–740 L of isocyanate-free air was sampled at 0.4–1.6 L/min and analyzed following Method 5505, demonstrated a loss of reagent which increased with the volume of air sampled. Entrainment of reagent in the exit stream was shown to be at least a minor cause of this loss. The results dictate against further use of Method 5505.

Development and Evaluation of a Method to Estimate Potential Formaldehyde Dose from Inhalable Dust/Fibers

Abstract A method for the estimation of formaldehyde dose from inhalable dust/fibers using a commercially available inhalable sampler was developed. Filters containing sampled dust/fibers were placed in 10 ml of distilled water and incubated at 37°C for 4 hours to liberate the formaldehyde from the dust/fibers. After incubation, the filter extracts were passed with a 0.45 μm filter to remove particles left in the extracts. Two analytical procedures were used for the analysis of the filter extracts. Either a 4-ml aliquot was analyzed using the chromotropic acid procedure, as outlined in NIOSH Method 3500, or a 1-ml aliquot was treated with 2,4-dinitrophenylhydrazine and a catalytic amount of perchloric acid and analyzed by high-performance liquid chromatography for the resulting 2,4-dinitrophenylhydrazone. The limits of detection for the chromotropic acid procedure and the 2,4-dinitrophenylhydrazine procedure were 0.44 and 0.08 μg per filter sample, respectively. Relative standard deviations of replicate d...