"Controlling an Ancient Disease in a New Environment: Industrial Hygiene Assessment and Interventions to Reduce Silica Exposure During Urban Infrastructure Rehabilitation"

Mark Goldberg, Urban Public Health

As the aging physical infrastructures of cities around the world are rehabilitated, the disruptions as well as the improvements caused by such work are well known.  The environmental hazards have also been described.  Less well documented are the health hazards to workers whose labor is responsible for the work.  One such health hazard is silicosis.

In the USA in recent years, there has been a dramatic increase in highway and bridge rehabilitation. In New York City over the past 10 years, every large bridge spanning its waterways, and every major highway, have been the sites of intensive rehabilitation.  All of this work involves concrete demolition and concrete pouring.  Since concrete is produced from aggregates such as sand and gravel, crystalline silica is almost always present to some degree in these materials.

Workers exposed to silica are at risk for contracting silicosis, an untreatable fibrotic disease of the lungs.  Silicosis  originated in antiquity with the mining and processing of metals and building stone. In his work De Re Metallica published in 1556 Agricola  was probably the first to recognize, or at least describe, the adverse effects of inhaled dust.  Much more recently, in the United States, silicosis became a cause celebré of trade unions, public health professionals, and the US Department of Labor.  A national campaign was waged to prevent the disease in mines and factories.  By 1970, with the passage of the Occupational and Safety and Health Act and the adoption of a legal occupational exposure limit for silica, it was thought that the disease was a thing of the past.

This was not to be.  Today, large numbers of construction workers are potentially exposed to dusts that contain crystalline silica during the performance of many routine tasks.  In spite of the fact that silicosis was documented so long ago, and more recently associated with pulmonary cancer, there is little recent information concerning the extent of silica exposure and disease among this group.

This report describes an investigation of silica exposure and controls for workers engaged in pneumatic drilling and chipping during bridge and road rehabilitation work.  Respirable dust and crystalline silica samples were collected at 6 rehabilitation sites in New York City. In addition, a survey was conducted of available information concerning engineering control technologies to reduce worker exposure to dust during these tasks.   The results indicate that workers are commonly overexposed to crystalline silica.  The control technology to reduce exposure is not commonly manufactured nor is it employed at construction sites.  Workers, therefore, remain at risk for developing silica-related diseases.