Hammond Duane R, Shulman Stanley A, Echt Alan S
a National Institute for Occupational Safety and Health, Division of Applied Research and Technology , Cincinnati , Ohio.
J Occup Environ Hyg. 2016 Jul;13(7):538-48. doi: 10.1080/15459624.2016.1153803.
Asphalt pavement milling machines use a rotating cutter drum to remove the deteriorated road surface for recycling. The removal of the road surface has the potential to release respirable crystalline silica, to which workers can be exposed. This article describes an evaluation of respirable crystalline silica exposures to the operator and ground worker from two different half-lane and larger asphalt pavement milling machines that had ventilation dust controls and water-sprays designed and installed by the manufacturers. Manufacturer A completed milling for 11 days at 4 highway construction sites in Wisconsin, and Manufacturer B completed milling for 10 days at 7 highway construction sites in Indiana. To evaluate the dust controls, full-shift personal breathing zone air samples were collected from an operator and ground worker during the course of normal employee work activities of asphalt pavement milling at 11 different sites. Forty-two personal breathing zone air samples were collected over 21 days (sampling on an operator and ground worker each day). All samples were below 50 µg/m(3) for respirable crystalline silica, the National Institute for Occupational Safety and Health recommended exposure limit. The geometric mean personal breathing zone air sample was 6.2 µg/m(3) for the operator and 6.1 µg/m(3) for the ground worker for the Manufacturer A milling machine. The geometric mean personal breathing zone air sample was 4.2 µg/m(3) for the operator and 9.0 µg/m(3) for the ground worker for the Manufacturer B milling machine. In addition, upper 95% confidence limits for the mean exposure for each occupation were well below 50 µg/m(3) for both studies. The silica content in the bulk asphalt material being milled ranged from 7-23% silica for roads milled by Manufacturer A and from 5-12% silica for roads milled by Manufacturer B. The results indicate that engineering controls consisting of ventilation controls in combination with water-sprays are capable of controlling occupational exposures to respirable crystalline silica generated by asphalt pavement milling machines on highway construction sites.
沥青路面铣刨机使用旋转的刀鼓来清除破损的路面以便回收利用。路面的清除有可能释放出可吸入的结晶二氧化硅，工人可能会接触到这种物质。本文描述了对操作人员和地面工人接触可吸入结晶二氧化硅情况的评估，评估对象是两台不同的半车道及更大规格的沥青路面铣刨机，这两台机器配备了由制造商设计和安装的通风除尘控制装置和喷水装置。制造商A在威斯康星州的4个公路建设工地进行了11天的铣刨作业，制造商B在印第安纳州的7个公路建设工地进行了10天的铣刨作业。为了评估除尘控制效果，在11个不同工地的沥青路面铣刨正常员工工作活动过程中，从一名操作人员和一名地面工人处采集了全工作日个人呼吸带空气样本。在21天内共采集了42份个人呼吸带空气样本（每天在一名操作人员和一名地面工人身上采样）。所有样本中可吸入结晶二氧化硅含量均低于美国国家职业安全与健康研究所建议的接触限值50微克/立方米。对于制造商A的铣刨机，操作人员个人呼吸带空气样本的几何平均值为6.2微克/立方米，地面工人为6.1微克/立方米。对于制造商B的铣刨机，操作人员个人呼吸带空气样本的几何平均值为4.2微克/立方米，地面工人为9.0微克/立方米。此外，两项研究中每个职业的平均接触量的95%置信上限均远低于50微克/立方米。制造商A铣刨的道路上，被铣刨的散装沥青材料中的二氧化硅含量为7%-23%，制造商B铣刨的道路上为5%-12%。结果表明，由通风控制与喷水相结合的工程控制措施能够控制公路建设工地沥青路面铣刨机产生的可吸入结晶二氧化硅的职业接触。
