Amosite Asbestos Fibers Research Articles

Identification and counting of asbestos fibers.

A combined analytical electron microscopic/optical count method for the determination of airborne asbestos fibers was tested for precision and bias. A modified phase contrast microscopic count method (NIOSH Method 7400) was used to determine total fiber content. The analytical electron microscope (AEM) procedure was added to identify the fraction of amosite asbestos fibers in airborne, laboratory-generated samples containing amosite and wollastonite fibers. Then this fraction was applied to the routine optical counts of all the samples in the set to estimate the asbestos fiber concentration. The effects of sample to sample, wedge to wedge, within wedge and between and counter variability were examined. In addition, the variabilities of the elemental ratio within a fiber and between fibers was also determined to find their possible influence on the ability to identify the fiber as amosite in the presence of other silicate fibers. A precision of 20.1% relative standard deviation (RSD) and a bias of -9.1% for the AEM count method compared with the optical count procedure were found for these mixed fiber samples.

Identification and Counting of Asbestos Fibers

A combined analytical electron microscopic/optical count method for the determination of airborne asbestos fibers was tested for precision and bias. A modified phase contrast microscopic count method (NIOSH Method 7400) was used to determine total fiber content. The analytical electron microscope (AEM) procedure was added to identify the fraction of amosite asbestos fibers in airborne, laboratory-generated samples containing amosite and wollastonite fibers. Then this fraction was applied to the routine optical counts of all the samples in the set to estimate the asbestos fiber concentration. The effects of sample to sample, wedge to wedge, within wedge and between counter variability were examined. In addition, the variabilities of the elemental ratio within a fiber and between fibers was also determined to find their possible influence on the ability to identify the fiber as amosite in the presence of other silicate fibers. A precision of 20.1% relative standard deviation (RSD) and a bias of −9.1% for the AEM count method compared with the optical count procedure were found for these mixed fiber samples.

Tumorigenesis by a ferroactinolite mineral

In lifetime exposure of male Fischer-344 rats to ferroactinolite fibers ∗ ∗ The term ‘fiber’ refers to mineral particles having parallel sides and a length to width (aspect) ratio > 3. and to UICC amosite asbestos fibers by means of intratracheal and intrapleural treatments, oncogenesis was greater in the lung for the ferroactinolite and in the pleura for the amosite. The lack of correlation between the effects of the two methods of exposure suggests that in this instance, intrapleural inoculation was not a good predictor of pulmonary response on the basis of mass dose. Another feature of the ferroactinolite was that pleural tumors resulted from intratracheal instillations. Conversely, lung tumors or tumorlike lesions were also induced by intrapleural inoculations of ferroactinolite. These facts suggest a greater in vivo transport for the ferroactinolite than for the amosite. Since there are far fewer mineral fibers per mass unit in the ferroactinolite the tumor yield per unit of mineral fibers was strikingly greater by both routes of administration for ferroactinolite than for amosite.