Surveillance for Silicosis — Michigan and New Jersey, 2003–2010

Margaret S. Filios, MSc1

Jacek M. Mazurek, MD, PhD1

Patricia L. Schleiff, MS1

Mary Jo Reilly, MS2

Kenneth D. Rosenman, MD2

Margaret E. Lumia, PhD, MPH3

Karen Worthington, MS3

1Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, CDC

2Division of Occupational and Environmental Medicine, Michigan State University, East Lansing, Michigan

3Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, Trenton, New Jersey

Corresponding author: Patricia L. Schleiff, Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, CDC. Telephone: 304-285-5874; e-mail: pls1@cdc.gov.

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 2003–2010. The data for this report were final as of December 31, 2010. Data are presented in tabular form on the prevalence of silicosis, the number of cases and the distribution of cases by year, industry, occupation, and the duration of occupational exposure to dust containing respirable crystalline silica (Tables 1–4). The number of cases by year is presented graphically (Figure). This report is a part of the first-ever Summary of Notifiable Noninfectious Conditions and Disease Outbreaks, which encompasses various surveillance years but is being published in 2015 (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 non-silica 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 approximately 2.2 million workers are currently exposed† to respirable crystalline silica in industries where exposure might occur: 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 can also 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. 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 classified crystalline silica as carcinogenic to humans (7), and this classification was reconfirmed in 2012 (8).

During 1968–2010, the number of deaths in the United States for which silicosis was listed on the death certificate declined from 1,065 (age-adjusted death rate: 8.21 per million persons aged ≥15 years) in 1968 to 101 (rate: 0.39) in 2010 (9). 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 (10). However, no decline occurred in the number of hospitalizations for which silicosis was listed as one of the discharge diagnoses during 1993–2011.§ Cases of silicosis continue to occur despite the existence of legally enforceable exposure limits.† Silicosis in any of its clinical forms is consistently undercounted by the Survey of Occupational Injuries and Illnesses (SOII), an employer-based surveillance system maintained by the Bureau of Labor Statistics (11). Estimates indicate that 3,600–7,300 new cases of silicosis might be occurring each year (11). In 2008, the National Academy of Sciences recommended that surveillance efforts to prevent silicosis and other interstitial lung diseases be continued and expanded (12).

Cases of silicosis are sentinel events that indicate the need for intervention (13). Silicosis was first designated as a notifiable condition at the national level in 1999¶ and reconfirmed in 2009.** In 2010, silicosis was a reportable condition in 25 states.††

NIOSH has supported efforts by states to conduct surveillance for silicosis under several cooperative agreements, including the Sentinel Event Notification system for Occupational Risks (SENSOR) and the State-Based Occupational Safety and Health Surveillance agreements. In 1987, states initiated active silicosis surveillance under SENSOR and began providing data voluntarily to NIOSH (14,15). 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 continue to maintain their sentinel case-based silicosis surveillance systems and intervention programs. 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 the period 2003–2010 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, states initiated active silicosis surveillance under SENSOR and began providing data voluntarily to NIOSH (13,14). The number of states conducting silicosis surveillance varies by year.¶¶ Two states, Michigan and New Jersey, continue to maintain their sentinel case-based silicosis surveillance systems and intervention programs 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 exposure. 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 that the case is ascertained from any data source.

Reporting practices affect how the data should be interpreted. Silicosis frequently is 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 Michigan and New Jersey, clinicians and hospitals are required to report cases of silicosis directly to the state health department or the state health department's bona fide agent (e.g., Michigan State University). In addition, in Michigan, employers are also required to report silicosis cases.

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 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 2003–2010, silicosis surveillance programs in Michigan and New Jersey identified and confirmed 273 cases; 25 (9.2%) had <10 years of potential exposure to silica dust. The manufacturing, construction, and mining industries accounted for 92% (n = 251) of the cases, with the greatest number of cases (175 [64%]) associated with manufacturing.

References

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