Kiefer M J, Buchan R M, Keefe T J, Blehm K D
Environ Res. 1987 Jun;43(1):31-8. doi: 10.1016/s0013-9351(87)80054-3.
The controversy of whether small asbestos fibers are biologically significant has not been resolved. The present standard method for evaluating asbestos fiber concentrations in workroom air excludes fibers less than 5 micron long even though it has been shown that small fiber concentrations dominate in a dust cloud. This research project was conducted to develop a mathematical model whereby one could predict small (less than 5 micron length) asbestos fiber concentration based on the fiber count concentration determined by phase contrast microscope analysis. Dry chrysotile asbestos was aerosolized into a chamber and sampled by membrane filtration. Segments from each filter were analyzed by both the NIOSH technique using phase contrast microscopy (PCM) and scanning electron microscopy (SEM) at 2000 X for fiber concentrations. A linear relationship was found to exist between the natural logarithm of the SEM-determined concentration and the natural logarithm of the PCM-determined concentration (r = 0.852). Using these data, a mathematical model was developed to predict SEM concentrations based on PCM counts. This model may have application in retrospective epidemiological studies for estimating small fiber exposure levels to determine if small fibers play a role in disease production. The greatest utility would be in those retrospective studies where the only exposure information available is based on PCM counts.
小石棉纤维是否具有生物学意义的争议尚未得到解决。目前评估工作场所空气中石棉纤维浓度的标准方法排除了长度小于5微米的纤维，尽管已经表明在尘云中短纤维浓度占主导地位。开展本研究项目是为了建立一个数学模型，据此可以根据相差显微镜分析确定的纤维计数浓度来预测小（长度小于5微米）石棉纤维浓度。将干燥的温石棉气溶胶化到一个腔室中，并用膜过滤进行采样。对每个过滤器的片段使用NIOSH技术通过相差显微镜（PCM）和在2000倍放大倍数下的扫描电子显微镜（SEM）分析纤维浓度。发现SEM测定的浓度的自然对数与PCM测定的浓度的自然对数之间存在线性关系（r = 0.852）。利用这些数据，建立了一个基于PCM计数预测SEM浓度的数学模型。该模型可能在回顾性流行病学研究中用于估计短纤维暴露水平，以确定短纤维是否在疾病发生中起作用。最大的用途将体现在那些仅有的暴露信息基于PCM计数的回顾性研究中。
