ABSTRACT
Objectives: Previous types of rock wool has been recently replaced with high-temperature wool (HT wool). HT wool is characterized by a chemical composition with a higher concentration of Al2O3 and a lower concentration of SiO2, lower biopersistence, and a higher melting point than previous types of rock wool. To evaluate the safety of HT wool, an asbestos substitute, we examined the biopersistence of HT wool in the lungs, based on changes in fiber count according to the length and fiber size (length and width), by performing a nose-only inhalation exposure study in rats. Methods: Male Fischer 344 rats were exposed to fibers at the target exposure concentration of 30 mg/m3 continuously for 3 hours daily for 5 consecutive days. Rats were sacrificed shortly after exposure, and 1, 2, and 4 weeks after exposure, and their lung tissues were incinerated at a low temperature. Then, fiber counts and sizes in the lungs were analyzed using a phase contrast microscope. Results: The fiber count in the lungs 4 weeks after exposure significantly decreased from the baseline value (shortly after exposure). The half-life of fibers calculated from the approximation curve was 34 days for all fibers and 11 days for fibers longer than 20 μm. Conclusions: Both the length and width significantly decreased 4 weeks after exposure, probably because fibers were ingested by alveolar macrophages, discharged to outside of the body by mucociliary movement, or lysed by body fluid. In future studies, it is necessary to examine the long-term persistence of fibers in the lungs.
Subject(s)
Hypertension , WoolABSTRACT
<p><b>OBJECTIVES</b>Previous types of rock wool has been recently replaced with high-temperature wool (HT wool). HT wool is characterized by a chemical composition with a higher concentration of Al(2)O(3) and a lower concentration of SiO(2), lower biopersistence, and a higher melting point than previous types of rock wool. To evaluate the safety of HT wool, an asbestos substitute, we examined the biopersistence of HT wool in the lungs, based on changes in fiber count according to the length and fiber size (length and width), by performing a nose-only inhalation exposure study in rats.</p><p><b>METHODS</b>Male Fischer 344 rats were exposed to fibers at the target exposure concentration of 30 mg/m(3) continuously for 3 hours daily for 5 consecutive days. Rats were sacrificed shortly after exposure, and 1, 2, and 4 weeks after exposure, and their lung tissues were incinerated at a low temperature. Then, fiber counts and sizes in the lungs were analyzed using a phase contrast microscope.</p><p><b>RESULTS</b>The fiber count in the lungs 4 weeks after exposure significantly decreased from the baseline value (shortly after exposure). The half-life of fibers calculated from the approximation curve was 34 days for all fibers and 11 days for fibers longer than 20 μm.</p><p><b>CONCLUSIONS</b>Both the length and width significantly decreased 4 weeks after exposure, probably because fibers were ingested by alveolar macrophages, discharged to outside of the body by mucociliary movement, or lysed by body fluid. In future studies, it is necessary to examine the long-term persistence of fibers in the lungs.</p>
ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the effect of exposure to rush-mat dust on the health of workers.</p><p><b>METHODS</b>A cross sectional study of 661 workers (349 men, 312 women) from 35 rush-mat plants was carried out by using occupational health investigation, questionnare and physical examination.</p><p><b>RESULTS</b>The geometric mean total dust concentration in the workshop was up to 20.00 mg/m3, and the geometric mean respirable dust concentration reached 8.22 mg/m3. The mean free SiO2 concentration of accumulated dust was 25.6%. The prevalence of radiographic small opacities profusion category > or = 1/0, according to the China Classification for pneumoconiosis (GB 5906-2000), and compared with the ILO 1980 system, was 2.57%. Even more, one man had category 2 pneumoconiosis with progressive massive fibrosis. However, the incidence of pneumoconiosis (1/0 at least) was correlated with work duration and dust concentration(r = 1.156, P < 0.001; r = 0.106, P = 0.006, respectively). Some positive correlations were found between the incidence of cough or expectoration and occupational exposure (r = 0.085, P = 0.028; r = 0.094, P = 0.016, respectively).</p><p><b>CONCLUSION</b>To our knowledge, this is the first report of rush pneumoconiosis in China. The results have offered the possibility of a dose-response relationship between rush-mat dust and pneumoconiosis. More investigation in this area is need.</p>