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).
A statistically significant decline in silicosis death rates was observed during 2001–2010.
However, silicosis deaths still occurred among persons aged 15–44 years. Of 28 decedents
aged 15–44 years, the youngest was aged 19 years. This would be consistent with the
decedent developing acute silicosis after an extremely high exposure to respirable
crystalline silica. Such findings indicate the importance of educating at-risk workers
and their employers regarding the dangers of exposure to respirable crystalline silica
in the workplace. The disparities by sex and by race reflect differences in the composition
of the workforces in the industries and occupations placing workers at risk for exposure
to crystalline silica dust.**
Approximately 2 million U.S. workers remain potentially exposed to respirable crystalline
silica (5). Occupational exposures to dust containing crystalline silica have long
been known to occur in mining, quarrying, sandblasting, pottery making, rock drilling,
road construction, stone masonry, and tunneling operations (1,5). Despite enforceable
limits†† on worker exposure to respirable crystalline silica, substantial overexposures
continue to occur in the United States (3). Moreover, new job tasks that place workers
at risk for silicosis continue to emerge.
In 2004, occupational disease surveillance programs in Michigan, New Jersey, Massachusetts,
New York, and Ohio reported nine confirmed cases of silicosis among technicians who
performed sandblasting in dental laboratories (6); in 2013, there were approximately
37,000 dental laboratory technicians in the United States.§§ In a 2012 report from
Israel, a 2014 report from Spain, and a 2015 report from the United States, silicosis
has been documented among workers exposed to respirable crystalline silica dust during
the fabrication and installation of quartz-containing engineered stone products used
primarily for kitchen and bathroom countertops (4,7,8). A 2013 report documented high
levels of exposure to respirable crystalline silica during hydraulic fracturing of
gas and oil wells (3). Moreover, a 2010 study reported an excess risk for silicosis
in coal miners that was associated with silica as a component of coal mine dust formed
during drilling, crushing, and loading of mine material (9). In 2013, there were approximately
204,000 oil and gas extraction industry workers and approximately 80,000 coal mining
industry workers in the United States.¶¶ Finally, although not in the United States,
silicosis cases have been reported in other occupational settings, including among
denim sandblasters (10).
What is already known on this topic?
Silicosis is an occupational lung disease caused by inhalation of respirable crystalline
silica in a variety of industrial operations, including mining, quarrying, road construction,
masonry, and tunneling. From 1968 to 2004, silicosis deaths in the United States declined
from 1,065 per year to 165.
What is added by this report?
Although silicosis deaths decreased significantly from 164 in 2001 to 101 in 2010,
they continued to occur among young persons, with 28 deaths reported among persons
aged 15–44 years during 2001–2010. New work tasks, including hydraulic fracturing,
sandblasting denim, and engineered stone countertop fabrication and installation,
can lead to overexposure to respirable crystalline silica.
What are the implications for public health practice?
Because of the serious health and socioeconomic consequences of silicosis, new operations
and tasks placing workers at risk for silicosis, and the continuing occurrence of
silicosis deaths, efforts to limit workplace exposure to crystalline silica need to
be maintained. In addition, the long latency of silicosis warrants continuing surveillance.
The Occupational Safety and Health Administration and CDC recommend best practices
for protecting workers, including the use of engineering controls and respiratory
In 1999, the Council of State and Territorial Epidemiologists made silicosis a nationally
notifiable condition.*** In addition, because current permissible exposure limits
for respirable crystalline silica do not adequately protect workers, the Occupational
Safety and Health Administration (OSHA) has proposed amending the current standards.
One of the proposed changes is a lower permissible exposure limit (5).
The findings in this report are subject to at least three limitations. First, silicosis
deaths were not validated by medical records or follow-up with health care providers,
thus findings might be subject to misclassification. Second, no individual work history
is reported on death certificates. Therefore, it was not possible to identify those
industries and occupations where the decedents’ exposures to crystalline silica occurred.
Finally, inhalation of respirable crystalline silica can cause diseases other than
silicosis, such as lung cancer and chronic obstructive pulmonary disease (1,5), which
are not considered in this analysis.
Effective silicosis prevention strategies for employers recommended by OSHA††† and
CDC’s National Institute for Occupational Safety and Health§§§ are available. Comprehensive
silicosis prevention programs include substituting less hazardous noncrystalline silica
alternatives when possible, implementing engineering controls (e.g., blasting cabinets,
local exhaust ventilation, not using compressed air for cleaning surfaces, using water
sprays to control airborne dust, and using surface wetting to prevent dust from becoming
airborne when cutting, drilling, grinding, etc.), administrative and work practice
controls, personal respiratory protective equipment, medical monitoring of exposed
workers, and worker training. Because of the serious health and socioeconomic consequences
of silicosis, new operations and tasks placing workers at risk for silicosis, and
the continuing occurrence of silicosis deaths among young workers, effective primary
prevention through elimination of exposure to respirable crystalline silica is critical.
At the same time, because of the sometimes long latency of silicosis, with cases diagnosed
years after exposure and often in retirement, ongoing silicosis surveillance is needed
to track its prevalence in the United States.