Silicosis Mortality Trends and New Exposures to Respirable Crystalline Silica — United States, 2001–2010

Ki Moon Bang, PhD; Jacek M. Mazurek, MD; John M. Wood, MS; Gretchen E. White, MPH; Scott A. Hendricks, MS; Ainsley Weston, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2015;64(5):117-120. 

In This Article

Abstract and Introduction

Introduction

Silicosis is a preventable occupational lung disease caused by the inhalation of respirable crystalline silica dust and can progress to respiratory failure and death.[1] No effective specific treatment for silicosis is available; patients are provided supportive care, and some patients may be considered for lung transplantation. Chronic silicosis can develop or progress even after occupational exposure has ceased.[1] The number of deaths from silicosis declined from 1,065 in 1968 to 165 in 2004.[2] Hazardous occupational exposures to silica dust have long been known to occur in a variety of industrial operations, including mining, quarrying, sandblasting, rock drilling, road construction, pottery making, stone masonry, and tunneling operations.[1] Recently, hazardous silica exposures have been newly documented during hydraulic fracturing of gas and oil wells and during fabrication and installation of engineered stone countertops.[3,4] To describe temporal trends in silicosis mortality in the United States, CDC analyzed annual multiple cause-of-death data for 2001–2010 for decedents aged ≥15 years.* During 2001–2010, a total of 1,437 decedents had silicosis coded as an underlying or contributing cause of death. The annual number of silicosis deaths declined from 164 (death rate = 0.74 per 1 million population) in 2001 to 101 (0.39 per 1 million) in 2010 (p = 0.002). Because of new operations and tasks placing workers at risk for silicosis, efforts to limit workplace exposure to crystalline silica need to be maintained.

For this analysis, decedents for whom the International Classification of Diseases, 10th Revision code J62 (pneumoconiosis due to dust containing silica [silicosis]§) was assigned as either the underlying or contributing cause of death were identified from 2001–2010 mortality data. Deaths of persons aged ≥15 years were analyzed. Trends in annual age-adjusted death rates per 1 million population were examined using a first-order autoregressive linear regression model. Differences in death rates were considered to be statistically significant if 95% confidence intervals did not overlap.

During 2001–2010, 1,437 decedents had silicosis coded as the underlying or contributing cause of death. Of these, 28 (1.9%) were aged 15–44 years, 1,370 (95.3%) were males, and 1,236 (86.0%) were whites ( Table ). The overall age-adjusted silicosis death rate for blacks (0.87 per 1 million) was significantly higher than the rate for whites (0.59) and other races (0.16). The age-adjusted silicosis death rate for males (1.39 per 1 million) was significantly higher than the rate for females. The annual number of silicosis deaths declined from 164 (0.74 per 1 million) in 2001 to 101 (0.39) in 2010 (p for trend = 0.002).

*Additional information available at http://webappa.cdc.gov/ords/norms.html.
Death rates were age-adjusted to the 2000 standard U.S. population. The age intervals used were 15–34, 35–44, 45–54, 55–64, 65–74, 75–84, and ≥85 years.
§Classic (chronic) silicosis results from exposure to respirable crystalline silica for >10 years; exposure to higher concentrations of silica for 5–10 years can cause accelerated silicosis, and symptoms of acute silicosis can sometimes develop within weeks of initial exposure to extremely high concentrations of silica.
Underlying cause of death is defined as "the disease or injury which initiated the train of morbid events leading directly to death, or the circumstances of the accident or violence which produced the fatal injury."

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