二氧化硅接触会增加肺癌风险 Review calls for increased attention to cancer risk from silica

亚特兰大2013年12月10日 – 一项新的评论强调了解二氧化硅对健康影响的新发展,并呼吁采取行动减少二氧化硅暴露在工作中的疾病和死亡,包括加强监管,提高意识和预防,以及提高对早期的关注使用低剂量CT扫描检测矽肺和肺癌。

几个世纪以来,已知二氧化硅会引起肺部疾病(矽肺病)。二氧化硅导致肺癌的证据近年来越来越多,并在过去几十年中不断积累。在CA撰写:临床医生的癌症期刊,亚特兰大埃默里大学罗林斯公共卫生学院的Kyle Steenland博士和美国癌症协会的Elizabeth Ward博士强调了三项具有预防疾病潜力的重要发展二氧化硅在工作中暴露致死。

第一个发展是最近的研究发表,提供详细的暴露 – 反应数据,实现基于定量风险评估的法规。新的研究还表明,没有矽肺病且不吸烟的二氧化硅暴露工人的肺死亡率仍然会增加死亡率。

其次,目前正在考虑一项新规则,目前正在考虑降低目前约有220万名目前接触二氧化硅的美国工人的职业接触率。风险评估估计,从当前标准到拟议标准的职业接触限值的降低将使矽肺病和肺癌死亡率降低到现行标准预测的约一半。

第三,低剂量计算机断层扫描现已被证明是一种有效的肺癌筛查方法。作者建议临床医生询问职业病史,以确定是否已发生二氧化硅暴露,如果有,可以特别注意早期发现矽肺病和肺癌,以及额外强调戒烟。作者建议,如果他们每天至少吸烟一包,至少20包年,那么从事二氧化硅职业暴露的个人可以从50岁开始接受筛查;专家称吸烟20包年。

该报告称,尽管海滩和环境空气中存在一些低水平的二氧化硅暴露,但没有证据表明这种低水平暴露会对健康产生影响。在工作中发生的风险越大,通常在建筑行业。当工人切割,研磨,压碎或钻出含二氧化硅的材料(如混凝土,砖石,瓷砖和岩石)时,就会发生暴露。大约有320,000名工人暴露在一般的工业运营中,如砖,混凝土和陶器制造,以及使用砂制品,如铸造工作。其他人在喷砂过程中暴露在外。二氧化硅暴露也发生在石油和天然气井的水力压裂(压裂)中。

控制职业二氧化硅暴露的最有效措施包括禁止喷砂,用金属砂粒代替喷砂,改造工艺和设备,以及通过使用外壳,气帘,喷水和通风技术控制粉尘传播,以及使用个人防护装备。

“目前的法规大大降低了美国的矽肺死亡率,但新的矽肺病例仍在继续诊断,”斯蒂兰德博士说。 “尽管与二氧化硅接触相关的肺癌风险并不像其他一些肺癌致癌物一样大,如吸烟或接触石棉,但有强烈而一致的证据表明二氧化硅接触会增加肺癌风险。”

PUBLIC RELEASE: 

Review calls for increased attention to cancer risk from silica

Action could help millions of Americans exposed to silica at work

AMERICAN CANCER SOCIETY

ATLANTA December 10, 2013–A new review highlights new developments in understanding the health effects of silica, and calls for action to reduce illness and death from silica exposure at work, including stronger regulations, heightened awareness and prevention, and increased attention to early detection of silicosis and lung cancer using low dose CT scanning.

For centuries, silica has been known to cause lung disease (silicosis). Evidence that silica causes lung cancer has been more recent, accumulating over the last several decades. Writing in CA: A Cancer Journal for Clinicians, Kyle Steenland, PhD, at the Rollins School of Public Health at Emory University in Atlanta, and Elizabeth Ward, PhD, of the American Cancer Society highlight three important developments that hold potential to prevent illness and death from silica exposure at work.

The first development is the publication of recent studies providing detailed exposure-response data, enabling regulations based on quantitative risk assessment. New studies have also shown that silica-exposed workers who do not have silicosis and who do not smoke still have increased rates of death from lung mortality.

Second, a new rule lowering the permissible occupational exposure for the estimated 2.2 million US workers currently exposed to silica is currently under consideration. Risk assessments estimate that lowering occupational exposure limits from the current to the proposed standard will reduce silicosis and lung cancer mortality to approximately one-half of the rates predicted under the current standard.

Third, low-dose computed tomography scanning has now been proven to be an effective screening method for lung cancer. The authors recommend that clinicians ask about occupational history to determine if silica exposure has occurred, and if it has, that extra attention might be given to the early detection of silicosis and lung cancer, as well as extra emphasis on quitting smoking. The authors recommend that individuals with significant occupational exposure to silica be offered screening beginning at age 50 years if they also have smoked the equivalent of one pack a day for at least 20 pack-years; what experts call 20 pack-years of smoking.

The report says while there is some low-level silica exposure on beaches and in ambient air in general, there is no evidence such low-level exposure causes health effects. The more concerning exposures occur on the job, most often in the construction industry. Exposure occurs when workers cut, grind, crush, or drill silica-containing materials such as concrete, masonry, tile, and rock. About 320,000 workers are exposed in general industry operations such as brick, concrete, and pottery manufacturing, as well as operations using sand products, such as foundry work. Others are exposed during sandblasting. Silica exposure also occurs from hydraulic fracturing (fracking) of oil and gas wells.

The most effective measures for the control of occupational silica exposures include banning sandblasting, substituting metal grits for abrasive blasting, modifying processes and equipment, and controlling dust transmission by using enclosures, air curtains, water spray, and ventilation techniques, and the use of personal protective equipment.

“Current regulations have substantially reduced silicosis death rates in the United States, but new cases of silicosis continue to be diagnosed,” says Dr. Steenland. “And while the lung cancer risk associated with silica exposure is not as large as some other lung carcinogens, like smoking or asbestos exposure, there is strong and consistent evidence that silica exposure increases lung cancer risk.”

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Article: Silica: A Lung Carcinogen: Steenland K and Ward E. CA Cancer J Clin 2013; doi: 10.3322/caac.21214/

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