Occupational Exposure to Asbestos: Effects of Unregulated Fibers

职业接触石棉：不受管制的纤维的影响

基本信息

批准号：
8936337
负责人：
DAVID B RICHARDSON
金额：
$ 7.43万
依托单位：
UNIV OF NORTH CAROLINA CHAPEL HILL
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-09-01 至 2016-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8936337
关键词：
Occupational Exposure Asbestos Effects Unregulated

项目摘要

DESCRIPTION (provided by applicant): Asbestos-related diseases remain a major public health problem in the US and abroad due to the large reservoir of asbestos in built infrastructure and the continued global trade in the material. Occupational standards for asbestos exposure in the US are based on visual counting of particles by phase contrast microscopy (PCM). Only fibers long and thick enough to reliably count using that method are regulated. However, in most occupational settings the majority of asbestos fibers are too small to count by PCM. Of particular concern are long fibers that are too thin to be visible using PCM but are believed to be very hazardous when inhaled. If asbestos exposure estimates based upon PCM methods were strictly proportional to total exposure to all etiologically-relevant asbestos fibers then a policy that regulated asbestos exposure as measured by PCM might suffice to control etiologically-relevant occupational asbestos exposures. However, there is strong evidence that the proportion of asbestos fibers that are not counted by PCM varies by work activity, fiber quality, and other conditions. Therefore, workers may have relatively low PCM-based metrics but high total asbestos exposure due to a large fraction of fibers that are too short or thin to count by PCM. In such settings, workers face risk of occupational disease due to the unmeasured, unregulated fraction of asbestos fibers. This issue has been raised repeatedly by workers and their advocates, who have argued for regulating exposure to asbestos using methods and rules that permit quantification of short (<5 �m) and thin (<0.25 �m) fibers, such as transmission electron microscopy (TEM) analysis of air samples. However, one obstacle to this has been that most occupational studies of asbestos workers have classified people based on PCM estimates of exposure. Regulators noted that it was unclear what level of exposure, as quantified by TEM, would be acceptable, since TEM estimates of the total number of fibers may not be well correlated with PCM estimates of fiber counts. We propose to draw upon unique existing data for US asbestos workers for whom high-quality estimates of asbestos exposure have been derived by PCM and fiber-size specific estimates of exposure have been derived by TEM. We propose to: 1) Use hierarchical regression methods to estimate the effects of the unregulated fraction of fibers; 2) Use G-methods to estimate TEM-based policies that would yield a comparable mortality to that obtained under current OSHA standards; and, 3) Use G- methods to estimate alternative TEM-based policies that would yield less mortality than that obtained under current OSHA standards. Aim 1 will assess the effects of the unregulated fraction of fibers using methods show to perform well in settings of correlated environmental exposures. Aims 2 and 3 draw upon contemporary methods to estimate public health impacts of policies in settings susceptible to bias due to the healthy worker survivor effect. The project, which addresses the NORA cross-sector priority to prevent work- related respiratory malignancies, applies innovative methods for estimating the effects of complex exposures. 1

描述（由适用提供）：由于石棉相关疾病在美国和国外仍然是一个主要的公共卫生问题，这是由于建筑基础设施中的石棉储备庞大以及材料中持续的全球贸易。在美国，石棉暴露的职业标准基于相反显微镜（PCM）对粒子的视觉计数。只有使用该方法的纤维长到足够厚到足够可靠的计数。但是，在大多数职业环境中，大多数石棉纤维太小而无法计数PCM。特别令人担忧的是长纤维太薄而无法使用PCM可见，但被认为是继承时非常危险。如果基于PCM方法的石棉暴露估算与所有与病因与病因相关的石棉纤维的总暴露严格成正比 PCM测量的调节石棉暴露可能足以控制与病因相关的职业石棉暴露。但是，有充分的证据表明，在工作活动，纤维质量和其他条件下，PCM不计算的石棉纤维的比例。因此，工人可能具有相对较低的基于PCM的指标，但由于大量的纤维太短或太薄而无法通过PCM计数，因此高石棉暴露量很高。在这种情况下，由于石棉纤维的未受监管的部分，工人面临发生疾病的风险。工人及其倡导者反复提出了这个问题，他们主张使用允许短量（<5 r）和薄（<0.25米）纤维的方法和规则调节石棉暴露，例如透射电子显微镜（TEM）空气样品分析。但是，这是一个障碍是，大多数对石棉工人的占领研究都根据PCM的暴露估计来对人员进行分类。监管机构指出，尚不清楚TEM量化的暴露水平是可以接受的，因为纤维总数的TEM估计值可能与纤维计数的PCM估计值不太息息相关。我们建议为我们的石棉工人借鉴独特的现有数据，在PCM中得出了石棉暴露的高质量估计，并且TEM已得出了光纤大小的特定暴露估计。我们建议：1）使用分层回归方法来估计纤维不受管制的效果； 2）使用G方法来估计基于TEM的策略，这些策略将产生与当前OSHA标准下获得的可比死亡率； 3）使用G方法来估计基于TEM的替代策略，这些策略将产生的死亡率少于目前的OSHA标准。 AIM 1将使用方法在相关环境暴露的环境中表现出很好的表现，以评估纤维不受监管的效果。目标2和3借鉴了当代方法，以估计由于健康工人的生存效应而容易偏见的环境中的公共卫生影响。该项目针对NORA跨部门的优先级，以防止与工作相关的呼吸道恶性肿瘤，它采用创新方法来估计复杂暴露的影响。 1