Surveillance for Silicosis — Michigan and New Jersey, 2003–2011

Preface

CDC’s National Institute for Occupational Safety and Health (NIOSH), state health departments, and other state entities maintain a state-based surveillance program of confirmed silicosis cases. Data on confirmed cases are collected and compiled by state entities and submitted to CDC. This report summarizes information for cases of silicosis that were reported to CDC for 2003–2011 by Michigan and New Jersey, the only states that continue to provide data voluntarily to NIOSH. The data for this report were final as of January 8, 2015. Data are presented in tabular form on the number and distribution of cases of silicosis by year (Table 1), duration of employment in occupations with potential exposure to dust containing respirable crystalline silica (Table 2), industry (Table 3), and occupation (Table 4). The number of cases by year is presented graphically (Figure). This report is a part of the Summary of Notifiable Noninfectious Conditions and Disease Outbreaks — United States, which encompasses various surveillance years but is being published in 2016 (1). The Summary of Notifiable Noninfectious Conditions and Disease Outbreaks appears in the same volume of MMWR as the annual Summary of Notifiable Infectious Diseases (2).

Background

Silicosis, a form of pneumoconiosis, is a progressive occupational lung disease caused by the inhalation, deposition, and retention of respirable dust containing crystalline silica. There is no effective specific treatment, and patients with silicosis can be offered only supportive care. Silicosis is preventable by using nonsilica substitution materials, effective dust control measures, and personal protective equipment.* Occupational exposure to respirable dust containing crystalline silica occurs in mining, quarrying, sandblasting, rock drilling, construction, pottery making, stone masonry, and tunneling operations (3). The Occupational Safety and Health Administration (OSHA) estimates that >2 million workers are currently exposed^† to respirable crystalline silica in industries where exposure might occur, including 1.85 million workers in the construction industry and 320,000 workers in general industry and maritime workplaces (4,5). Typically a disease of long latency, silicosis usually is diagnosed through a chest radiograph after ≥10 years of exposure to respirable crystalline silica dust. Nodular silicosis also can develop within 5–10 years of exposure to higher concentrations of crystalline silica. A clinical continuum exists between the accelerated and the chronic forms of silicosis. Acute silicosis has a different pathophysiology than accelerated or chronic silicosis in that it might develop within weeks of initial exposure and is associated with exposures to extremely high concentrations^† of crystalline silica. Respiratory impairment is severe, and the disease is usually fatal within a year of diagnosis. In addition, occupational exposure to respirable crystalline silica puts workers at increased risk for other serious health conditions, including chronic obstructive lung disease, kidney and connective tissue disease, tuberculosis and other mycobacterial-related diseases, and lung cancer (6). In 1997, the International Agency for Research on Cancer (IARC) classified crystalline silica as carcinogenic to humans (7), and this classification was reconfirmed in 2012 (8).

During 1999–2013, a total of 2,065 decedents (age-adjusted death rate: 0.57 per 1 million persons aged ≥15 years) had silicosis listed as the cause of death on the death certificate. ^§ The annual number of silicosis deaths declined from 185 in 1999 to 111 in 2013 (9,10). Analysis of 1968–2005 data indicated that silicosis-attributable years of potential life lost before age 65 years decreased substantially during 1968–2005, but the decline slowed during the last 10 years of that period (11). However, the number of hospitalizations for which silicosis was listed as one of the discharge diagnoses did not decline during 1997–2011.^¶ Cases of silicosis continue to occur despite the existence of legally enforceable exposure limits.^† In 2014, silicosis with progressive massive fibrosis was observed in a male aged 37 years who worked for an engineered stone countertop company as a polisher, laminator, and fabricator (12). Silicosis in any of its clinical forms is consistently undercounted by the Survey of Occupational Injuries and Illnesses, an employer-based surveillance system maintained by the Bureau of Labor Statistics (13). An estimated 3,600–7,300 new cases of silicosis might be occurring each year (13). In 2008, the National Academy of Sciences recommended the continuation and expansion of surveillance efforts to prevent silicosis and other interstitial lung diseases (14).

Cases of silicosis are sentinel events that indicate the need for intervention (15). Silicosis was put under nationwide surveillance as part of the National Public Health Surveillance System in 1999** and became a nationally notifiable and standard condition in 2009.^†† In 2010, the national surveillance case definition for silicosis was added to CDC’s National Notifiable Diseases Surveillance System (NNDSS).^§§

Since 2005, NIOSH has supported efforts by states to conduct surveillance for silicosis under the State-Based Occupational Health and Safety Surveillance cooperative agreement. Between 1987 and 2005, different cooperative agreements were in place, including the Sentinel Event Notification system for Occupational Risks (SENSOR). In 1987, some states initiated active silicosis surveillance under SENSOR and began providing data voluntarily to NIOSH (16,17). Since 1992, data summaries have been published in a series of reports.^¶¶ The number of states*** that conduct silicosis surveillance varies by year based on funding support by NIOSH. Currently, Michigan and New Jersey are funded to continue to conduct sentinel case-based silicosis surveillance and interventions. These two states are the only states that continue to provide data voluntarily to NIOSH.

This report summarizes data for silicosis cases that met the surveillance case definition for a confirmed silicosis case for 2003–2011 as reported by Michigan and New Jersey. Data from state programs are updated annually and are available through the CDC’s Work-Related Lung Disease Surveillance System (eWoRLD).^†††

Data Sources

In 1987, some states initiated active silicosis surveillance under SENSOR and began providing data voluntarily to NIOSH (16,17). The number of states conducting silicosis surveillance varies by year.^†† Two states, Michigan and New Jersey, continue to conduct sentinel case-based silicosis surveillance and interventions and provide data voluntarily to NIOSH.

Interpreting the Data

In this report, state surveillance data for confirmed silicosis cases are presented by the year of the reporting source, industry, occupation, and duration of employment in occupations with potential exposure to silica dust. The reporting source year is the year of a silicosis-related clinician report, hospital discharge, death, or year of a workers’ compensation claim. If a case is ascertained from multiple data sources over multiple years, the year reported is the first year the case is ascertained from any data source.

Reporting practices affect how the data should be interpreted. Silicosis is frequently not recognized or reported by clinicians. Although multiple data sources are used, case ascertainment likely is incomplete. The data provided in this report are based on data from two states and might not be generalizable.

Methods for Identifying Silicosis

State sentinel silicosis surveillance programs identify suspected cases of silicosis through health care provider reports, hospital discharge or outpatient data, state death certificate data, and Workers’ Compensation data. Other data sources include the identification by the index case of additional cases among co-workers at a work place, referrals from industrial hygienists conducting inspections at companies, employer screenings, and referrals from other state health departments.

In New Jersey, clinicians and hospitals are required to report cases of silicosis directly to the state health department. In Michigan, physicians, hospitals, clinics or employers are required to report cases of silicosis directly to the Michigan Department of Licensing and Regulatory Affairs or to the state’s bona fide agent, Michigan State University.

Cases are confirmed using the surveillance case definition, which requires a history of occupational exposure to airborne silica dust and either or both: 1) a chest radiograph (or other radiographic image, such as computed tomography) showing abnormalities interpreted as consistent with silicosis; or 2) lung histopathology consistent with silicosis.^§§ Medical record review and follow-up interviews are conducted with the reported case or their surviving next-of-kin, using a standardized telephone-administered questionnaire.

Publication Criteria

De-identified confirmed cases of silicosis case data are reported voluntarily to NIOSH on an annual basis. All confirmed cases are published.

Highlights

Silicosis is a progressive and preventable occupational lung disease caused by the inhalation, deposition, and retention of respirable dust containing crystalline silica. As a sentinel event, a case of silicosis indicates a failure to prevent exposure to crystalline silica dust.

For the period 2003–2011, silicosis surveillance programs in Michigan and New Jersey identified and confirmed 292 cases; 28 (9.6%) had <10 years of potential exposure to silica dust. The manufacturing, construction, and mining industries accounted for 92% (n = 270) of the cases, with the greatest number of cases (184 [63%]) associated with manufacturing.