Nakadate T
Department of Hygiene and Public Health, Tokyo Women's Medical College, Japan.
Occup Environ Med. 1995 Jun;52(6):368-73. doi: 10.1136/oem.52.6.368.
To examine whether or not workers with pre-existing mild pulmonary fibrosis have accelerated decline in forced expiratory volume in one second (FEV1) or forced vital capacity (FVC), under low level exposure to chrysotile asbestos.
All male workers in two asbestos manufacturing factories were followed up annually for six years to compare their declines in FEV1 and FVC. The values of FEV1 and FVC were divided by the square of the person's height to adjust for body size differences (FEV1/Ht2 and FVC/Ht2, respectively). Annual change was calculated for each subject as a slope of the simple linear regression with FEV1/Ht2 or FVC/Ht2 regressed according to age. Analysis was conducted on 242 middle aged workers who had normal routine spirometry values, normal chest radiographs or mild pneumoconiosis up to 1/2 grade, without changes either in smoking habit or severity of pneumoconiosis during the study period, and with acceptable spirograms in three or more surveys. The occupational environment, in terms of chrysotile asbestos, had been well controlled below the threshold limit value of Japan at that time--namely, 2 fibres/micromilligrams. RESULTS-There was no significant effect from the interaction between pre-existing mild pulmonary fibrosis and low level of exposure to chrysotile asbestos on the accelerated annual decline of FEV1/Ht2, or FVC/Ht2. Fibrosis significantly contributed to annual changes in FEV1/Ht2, even after adjustment for mean FEV1 and smoking. The point estimate of the contribution was - 4.9 ml/m2/y. No significant independent contribution of exposure was found in decline of either FEV1/Ht2 or FVC/Ht2.
Pre-existing pulmonary fibrosis is an independent risk factor for accelerated annual decline of FEV1, even when mild and stable. Additional decline due to exposure to chrysotile asbestos is less probable if it is well controlled under the current threshold limit value.
研究在低水平温石棉暴露情况下，已患有轻度肺纤维化的工人一秒用力呼气量（FEV1）或用力肺活量（FVC）是否加速下降。
对两家石棉制造厂的所有男性工人进行了为期六年的年度随访，以比较他们FEV1和FVC的下降情况。FEV1和FVC的值除以身高的平方，以校正体型差异（分别为FEV1/Ht2和FVC/Ht2）。计算每个受试者的年度变化，作为根据年龄对FEV1/Ht2或FVC/Ht2进行简单线性回归的斜率。对242名中年工人进行了分析，这些工人常规肺功能测定值正常，胸部X光片正常或尘肺程度达1/2级，在研究期间吸烟习惯或尘肺严重程度无变化，且在三次或更多次调查中肺功能图可接受。当时，就温石棉而言，职业环境已得到很好的控制，低于日本的阈限值——即2纤维/微毫克。结果：已有的轻度肺纤维化与低水平温石棉暴露之间的相互作用，对FEV1/Ht2或FVC/Ht2的年度加速下降没有显著影响。即使在调整了平均FEV1和吸烟因素后，纤维化对FEV1/Ht2的年度变化仍有显著影响。贡献的点估计值为-4.9毫升/平方米/年。在FEV1/Ht2或FVC/Ht2的下降中，未发现暴露有显著的独立贡献。
即使轻度且稳定，已有的肺纤维化也是FEV1年度加速下降的独立危险因素。如果在当前阈限值以下得到很好的控制，接触温石棉导致的额外下降可能性较小。
