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Surveillance for Silicosis, 1993 -- Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin

Roy Maxfield, M.S.(1) Celan Alo, M.D.(1) Mary Jo Reilly, M.S.(2) Kenneth Rosenman, M.D.(2) Doug Kalinowski, C.I.H.(3) Martha Stanbury, M.S.P.H.(4) David J. Valiante, C.I.H.(4) Bill Jones, M.P.H, R.S.(5) Susan Randolph, M.S.N., R.N., C.O.H.N.(5) Edward Socie, M.S.(6) Keith Gromen(6) Adeline Migliozzi, R.N., M.S.N., C.O.H.N.(6) Teresa M. Willis(7) Patricia Schnitzer, Ph.D.(7) Dennis M. Perrotta, Ph.D(7) George Gruetzmacher, C.I.H, P.E.(8) Henry Anderson, M.D.(8) Ruth Ann Romero Jajosky, D.M.D., M.P.H.(9) Robert M. Castellan, M.D., M.P.H.(9) Steven Game, M.P.H.(9) (1)Illinois Department of Public Health, Springfield, IL (2)Michigan State University, East Lansing, MI (3)Michigan Department of Consumer and Industry Services, Lansing, MI (4)New Jersey Department of Health, Trenton, NJ (5)North Carolina Department of Environment, Health and Natural Resources, Raleigh, NC (6)Ohio Department of Health, Columbus, OH (7)Texas Department of Health, Austin, TX (8)Wisconsin Department of Health and Social Services, Madison, WI (9)Division of Respiratory Disease Studies National Institute for Occupational Safety and Health (NIOSH), CDC

Abstract Problem/Condition: Silicosis is an occupational respiratory disease caused by the inhalation of respirable dust containing crystalline silica. Public health surveillance programs to identify workers at risk for silicosis and target workplace-specific and other prevention efforts are currently being field-tested in seven U.S. states. Reporting Period Covered: Confirmed cases ascertained by state health departments during the period January 1, 1993, through December 31, 1993; the cases and associated workplaces were followed through December 1994. Description of Systems: As part of the Sentinel Event Notification System for Occupational Risks (SENSOR) program initiated by CDC's National Institute for Occupational Safety and Health (NIOSH), development of state-based surveillance and intervention programs for silicosis was initiated in 1987 in Michigan, New Jersey, Ohio, and Wisconsin and in 1992 in Illinois, North Carolina, and Texas. Results: From January 1, 1993, through December 2, 1994, the SENSOR silicosis programs in Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin confirmed 256 cases of silicosis that were initially ascertained in 1993. Overall, 185 (72%) were initially identified through review of hospital discharge data or through hospital reports of silicosis diagnoses; 188 (73%) were associated with silica exposure in manufacturing industries (e.g., foundries; stone, clay, glass, and concrete manufacturers; and industrial and commercial machinery manufacture). Overall, 42 (16%) cases were associated with silica exposure from sandblasting operations. Among the 193 confirmed cases for which information was available about duration of employment in jobs with potential exposure to silica, 37 (19%) were employed less than or equal to 10 years in such jobs and 156 (81%) were employed greater than or equal to 11 years.

A total of 192 primary workplaces associated with potentially hazardous silica exposures were identified for the 256 confirmed silicosis cases. Of these, nine (5%) workplaces were inspected by state health department (SHD) industrial hygienists, 19 (10%) were referred to the Occupational Safety and Health Administration (OSHA) for follow-up, and seven (4%) were routinely monitored by the Mine Safety and Health Administration. Of the 157 (82%) remaining workplaces, follow-up activities determined that 82 were no longer in operation, eight were no longer using silica, 18 were assigned a lower priority for follow-up, six were associated with building trades and could not be inspected because of the transient nature of work in the construction industry, and 43 workplaces were not inspected for other reasons. Fourteen (7%) of the 192 workplaces were inspected. At 10 of the 14 workplaces, airborne levels of crystalline silica were measured; in nine, silica levels exceeded the NIOSH-recommended exposure level of 0.05 mg/m,3 and in six, airborne silica levels also exceeded federal permissible exposure limits. Actions Taken: Employee-specific and other preventive interventions have been initiated in response to reported cases. In addition, special silicosis prevention projects have been initiated in Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin. To facilitate the implementation of silicosis surveillance by other states, efforts are ongoing to identify and standardize core data needed by surveillance programs to describe cases and the workplaces where exposure occurred. These core variables will be incorporated into a user-friendly software system that states can use for data collection and reporting.

INTRODUCTION

Silicosis is an occupational lung disease that develops after dust containing respirable crystalline silica is inhaled and deposited in the lungs. It is both progressive and incurable, yet preventable. In response to high concentrations of crystalline silica, disease can develop within a year after initial exposure. This acute form of the disease is associated with the accumulation of a proteinaceous fluid in the alveolar spaces of the lungs; it typically causes death within months of initial diagnosis. More commonly, chronic silicosis occurs after greater than or equal to 10 years of relatively low, but still hazardous, exposure to crystalline silica. Chronic silicosis manifests as scarring of the lung tissue; it can be debilitating and cause death. In addition, silicosis is a risk factor for tuberculosis (1). The 1987 International Agency for Research on Cancer (IARC) Monograph on the Evaluation of Carcinogenic Risks to Humans classified crystalline silica as a probable human carcinogen (2). In October 1996, IARC reconvened a Monograph Working Group to reevaluate the carcinogenicity of silica, some silicates, and organic fibers. The Monograph Group concluded that inhaled crystalline silica in the form of quartz or cristobalite from occupational sources is carcinogenic to humans (IARC, unpublished data). In view of this assessment, persons occupationally exposed to crystalline silica in one or more of these two forms, regardless of whether they have silicosis, should be considered at potentially increased risk for lung cancer.

In 1987, CDC's National Institute for Occupational Safety and Health (NIOSH) awarded 5-year cooperative agreements to four state health departments (SHDs) (Michigan, New Jersey, Ohio, and Wisconsin) to develop and implement silicosis surveillance and preventive intervention projects under the Sentinel Event Notification Systems for Occupational Risks (SENSOR) program (3). The Michigan and New Jersey SENSOR projects were modeled after another NIOSH-supported cooperative agreement that began in 1984. * In an attempt to build on the experience gained by the states during the first 5-year phase of SENSOR, in 1992 these four states were granted additional 5-year cooperative agreements to continue refining and field-testing their approaches to silicosis surveillance and intervention. In 1992, three other states (Illinois, North Carolina, and Texas) were awarded SENSOR cooperative agreements to establish similar silicosis projects. This report summarizes data for confirmed silicosis cases ascertained during 1993 from the silicosis surveillance and intervention programs in all seven states.

METHODS Surveillance Case Report Ascertainment

All seven states with SENSOR silicosis programs actively solicit case reports from physicians likely to evaluate patients with silicosis, such as pulmonary and occupational medicine physicians and B-Readers (physicians trained and certified in the use of the International Labour Office system for classification of radiographs for pneumoconioses) (4,5).

Before 1993, physicians were required to report silicosis cases to SHDs in Michigan, New Jersey, Ohio, Texas, and Wisconsin (Table_1). Physicians were not required to report silicosis diagnoses in North Carolina until January 1, 1994, and in Illinois, physician reporting of silicosis cases continues to be voluntary. The states with SENSOR silicosis programs actively solicit silicosis case reports from mandated and voluntary reporters (Table_1). North Carolina is the only state that did not begin to solicit case reports actively from physicians until after the end of the 1993 reporting period.

Although the original SENSOR model was based primarily on physician reporting (6), other data sources are utilized in each state for ascertaining silicosis cases. All seven SHDs review death certificate data. In Illinois, Michigan, and New Jersey, computerized hospital discharge data are reviewed to identify silicosis diagnoses. In addition, hospitals in Michigan and New Jersey are required to report hospital discharge diagnoses of silicosis directly to their SHDs. Although surveillance staff in Texas and Ohio do not have access to computerized hospital discharge data, staff in Texas review medical records of selected hospitals for diagnoses of silicosis, and, in 1993, Ohio began active solicitation of silicosis diagnosis reporting from hospitals (7). In addition, in Ohio and Michigan reports of workers' compensation claims are reviewed to identify potential cases. One source of data unique to North Carolina is the North Carolina Dusty Trades Program, a long-standing medical screening program, supported by the state health department, for workers exposed to silica and asbestos. Finally, in Michigan, New Jersey, and Ohio, cases have also been identified through selected surveys targeting silica-exposed coworkers of index cases.

Case Confirmation

In all seven states, demographic, work history, and medical information is collected about each reported silicosis case. This information is obtained through a combination of the initial case ascertainment source, a review of medical records, and follow-up telephone interviews with persons with cases or their next of kin. For SENSOR surveillance purposes, silicosis case confirmation requires a history of occupational exposure to airborne silica dust and a) a chest radiograph interpreted as characteristic of silicosis and/or b) lung histopathology characteristic of silicosis. These criteria have been modified from the previously published surveillance case definition for silicosis, which did not cite a requirement for a history of occupational exposure to airborne silica when the lung pathology criterion was used for case confirmation (3,8). To enhance the specificity of silicosis surveillance, some states also apply exclusion criteria for persons with occupational work histories of coal mining, ** because coal workers' pneumoconiosis and silicosis have many clinical features in common.

The primary workplace associated with silica exposure for each worker is the job that is considered by surveillance staff as most likely responsible for the longest or highest potential exposure to silica. This assessment is based on a review of the detailed work history solicited for each case, combined with the surveillance staff's knowledge of high-risk industries, occupations, and word processes. Surveillance staff attempt to locate and contact all workplaces, both primary and secondary, that are potentially associated with silica exposure to collect information about current work practices and activities that may involve exposure to silica. This information, combined with information regarding nature of the disease (e.g., age of patient, severity of disease, number of years exposed) and number of cases reported in association with a specific workplace, assists surveillance staff in prioritizing workplace inspections by SHD industrial hygienists and in making appropriate referrals to consultative or enforcement agencies.

Preventive Intervention

Prevention efforts differ among the states, but generally include one or more of the following activities: a) follow-up interviews with persons with reported and/or confirmed silicosis or their next of kin; b) follow-up investigations to determine whether the workplace identified by the person with silicosis or his/her next of kin is currently active and engaged in work processes that have the potential for continuing hazardous silica exposure; c) educational outreach to persons with cases and their coworkers, employers, physicians, and unions; d) workplace inspections by SHD industrial hygienists or referrals to consultation programs such as that of the Occupational Safety and Health Administration (OSHA) to assess current silica exposure and to provide workplace-specific recommendations for reducing or eliminating hazardous silica exposure; and e) referrals to appropriate enforcement agencies -- OSHA or the Mine Safety and Health Administration (MSHA) -- if information obtained during the workplace follow-up indicates excessive exposures and/or hazardous work practices.

RESULTS Epidemiology

The SENSOR silicosis programs in Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin confirmed 256 cases of silicosis that were initially ascertained in 1993. Of these, 245 (96%) were male and 11 (4%) were female; 189 (74%) were white, 62 (24%) were black, three (1%) were of other races, and the race of two (0.8%) persons was unknown (Table_2). The race and sex distribution of cases is presented here because past differential hiring practices have put minority workers at greater risk than white workers of being placed in jobs with a high potential risk of exposure to airborne crystalline silica (9). Consequently, if adequate dust control measures are not properly employed, these workers are placed at greater risk for silicosis. ***

The year of birth ranged from 1898 to 1968 (median=1924). By state, the median year of birth ranged from 1907 (n=2; range: 1905-1909) in North Carolina to 1943 (n=42; range: 1908-1968) in Texas.

Overall, 185 (72%) confirmed cases were initially identified through review of hospital discharge data or through hospital reports of silicosis diagnoses, 37 (15%) through physician reports, 26 (10%) through review of death certificate data, and eight (3%) through a combination of workers' compensation claims reports, other health-care providers, and referrals from other SHDs (Table_3).

Silica exposure in manufacturing industries accounted for 73% of the 256 confirmed cases (Table_4). The primary metal industries were associated with silica exposure in 86% of the cases in Wisconsin, 74% of the cases in Michigan, 46% of the cases in Ohio, and 30% of the cases in Illinois. Industries manufacturing stone, clay, glass, and concrete products accounted for 29% of the cases in New Jersey. In Texas, 21% of the cases were associated with the industrial and commercial machinery and computer equipment manufacturing industries.

Overall, 37 (14%) of the persons with cases had less than or equal to 10 years of employment in industries with potential for silica exposure, 89 (35%) had 11-30 years, 67 (26%) had greater than 30 years, and for 63 (25%) this information is unavailable. The year of first reported exposure to airborne silica dust in an occupational setting ranged from 1917 to 1990 (median=1950).

Workplace Follow-up

Overall, 192 primary workplaces associated with potentially hazardous silica exposures were identified for the 256 confirmed silicosis cases (Table_5). Of these, nine (5%) workplaces were inspected by SHD industrial hygienists, 19 (10%) were referred to OSHA for follow-up, and seven (4%) had routine monitoring by MSHA. Of the 157 (82%) remaining workplaces, follow-up activities determined that 82 workplaces were no longer in operation, eight were in operation but no longer using silica, 18 were assigned a lower priority for follow-up, **** six were associated with building trades and could not be inspected because of the transient nature of work in the construction industry, and 43 workplaces were not inspected by SHD staff for other reasons (e.g., workplace-specific information was unavailable or had not been confirmed, workplaces could not be located or were located out of state, SHD staff were denied entry into the workplaces, or follow-up was pending).

Workplace inspections were conducted at 14 (7%) of the 192 workplaces. These 14 workplaces include nine workplaces inspected by SHD industrial hygienists and five workplaces (all foundries) that the Michigan OSHA @ program inspected. The workplaces represented by the nine SHD inspections include a foundry in Illinois; a foundry, a sand mine, and a sanitary ware (i.e., vitreous china plumbing fixtures {SIC code 3261}) manufacturer in New Jersey; three foundries and a quarry in Ohio; and a quarry in North Carolina. At 10 of the 14 workplaces, airborne levels of crystalline silica were measured; in nine (90%) of these workplaces the silica levels exceeded the NIOSH-recommended exposure level (REL), @@ and in six (60%) workplaces airborne silica levels also exceeded federal permissible exposure limits (PEL) @@@ @@@@ (Table_6).

DISCUSSION

Data aggregation for this report was based on the year a person with a confirmed case of silicosis was ascertained by the SHD SENSOR program and therefore depends on timing of access to data sources and intensity and completeness of surveillance and follow-up efforts. This method of data aggregation differs from the data aggregation methods used in previously published summary reports of SENSOR silicosis data (3,12,13). In previously published reports, data have been aggregated according to the source year -- the year of a silicosis-related hospital discharge, death, year of a workers' compensation claim, or physician report. The method of data aggregation for this report was changed to facilitate administrative tracking of reported cases. The summary results in this report are therefore not directly comparable with those of previously published summary reports and should not be used to calculate silicosis incidence rates.

The methods for silicosis surveillance initially developed by Michigan, New Jersey, Ohio, and Wisconsin are being adopted by Illinois, North Carolina, and Texas. Overall findings demonstrate the importance of hospital discharge diagnoses for identification of silicosis cases. Only the Illinois, Michigan, and New Jersey SHDs have routine access to computerized hospital discharge data for silicosis case identification. Ohio and North Carolina, however, began to actively solicit hospital reports of silicosis diagnoses in 1993 and 1994, respectively. Although Wisconsin does not yet have access to hospital discharge data for 1993, surveillance staff in Wisconsin expect to review computerized hospital discharge tapes by 1997 for silicosis case identification. Although hospital discharge data are an important case ascertainment source, other case identification sources need to be developed, because many patients with silicosis may not be hospitalized for silicosis or may not mention a previous diagnosis of silicosis if hospitalized for another condition.

The year of initial silicosis diagnosis, the optimal year to use for silicosis incidence rate calculations, is not usually known by SHD surveillance staff. As an alternative, the Michigan SENSOR program has used the source year (previously defined) as the reference year for silicosis incidence rate calculations, since the source year represents the first time the surveillance program staff became aware of the silicosis diagnosis. Using the source year, the Michigan SENSOR program reports that, among counties where average annual silicosis incidence rates were compared for black and white workers, black workers had consistently higher incidence rates than white workers because of past differential hiring practices that increased this group's risk of exposure (see Epidemiology) (14). In Michigan, the overall average annual incidence rate for black males (14.3 cases per 100,000) ages greater than 40 years was seven times higher than for white workers (2.1 cases per 1000,000) in the same age group (denominator data from the 1990 U.S. census for men ages greater than 40). Silicosis count data in Michigan indicate that the number of black males with silicosis is greater than that of silicosis cases in all other race and sex groups, reflecting past hiring practices in foundries, where black males were more likely to be given dustier jobs with increased likelihood of exposure to silica (14). Knowledge about high-risk race and sex groups can be useful for targeting public health prevention programs. For example, the Michigan SENSOR program has recommended that select counties (those with high silicosis incidence rates and numbers of cases) target tuberculosis screening tests for black males, because this group is at the highest risk for silicosis and because silicosis increases one's susceptibility to tuberculosis.

The word "sandblaster" was listed in the occupation narratives of 42 (16%) persons with confirmed cases of silicosis ascertained in 1993. At least one of these persons was first occupationally exposed to silica sand in abrasive blasting operations as late as 1983, 9 years after NIOSH recommended that materials containing greater than 1% crystalline silica be prohibited as abrasive blasting materials and that less hazardous materials be used (10). Because of the continuing occurrence of severe silicosis associated with sandblasting, NIOSH published an Alert in 1992 reiterating this recommendation (15). Data were not available at the time of data aggregation regarding whether an individual had ever conducted sandblasting activities in the workplace and/or whether an individual had ever worked in an uncontrolled plume of dust generated from sandblasting; therefore, other SENSOR silicosis cases ascertained in 1993 may be related to exposures generated during sandblasting activities. The risk of silicosis is high in workers exposed to sandblasting operations, and the quantity of dust generated by these operations is often difficult to control. Sandblasting also produces dust containing freshly fractured surfaces of crystalline silica, which appears to represent a greater hazard than crystalline silica dust characterized predominantly by aged cleavage surfaces (16).

In 1993, three states with SENSOR silicosis programs -- Michigan, New Jersey, and Ohio -- developed special silicosis prevention projects to identify workplaces where abrasive blasting activities are conducted and to target these workplaces for intervention activities, including workplace surveys, industrial hygiene inspections, and distribution of educational literature regarding health hazards of silica exposure and practices to prevent silica exposure. With information gathered to date by NIOSH and New Jersey regarding silica sand substitutes, the New Jersey SHD prepared a fact sheet for employers aimed at promoting the use of alternatives to silica sand in abrasive blasting operations. The fact sheet includes information about the properties, equipment needs, specific applications, advantages, limitations, and cost of the major silica sand substitutes (aluminum oxide, baking soda, coal slag, corn cob granules, dry ice, garnet, glass beads, nickel slag, nut shells, olivine, plastic media, staurolite, and steel grit/shot). In addition, the fact sheet underscores the need for continued use of appropriate measures to control exposure, because the health effects of the substitutes have not yet been fully determined and because the substrate material being removed by abrasive blasting can contain silica or other hazardous materials (e.g., lead). The fact sheet has been shared with other states with SENSOR silicosis programs and has been distributed to 1,969 companies (1,795 in Michigan, 133 in New Jersey, and 41 in Ohio) identified as having a potential to conduct sandblasting operations.

A component of the silicosis prevention project in Michigan included evaluating whether the recommendations issued during initial SENSOR-prompted workplace inspections for silica exposure hazards had been implemented or had led to reduced airborne silica levels. To assess whether airborne silica levels had been reduced, industrial hygienists from Michigan OSHA reinspected 10 companies where airborne silica levels exceeded the OSHA PEL during the initial SENSOR-prompted inspections. Air sampling conducted during the reinspections showed substantially lower airborne silica levels-eight of the 10 workplaces (six foundries, a pottery, and a fabricated metal products manufacturer) had levels below the OSHA PEL for respirable crystalline silica. In the other two workplaces (both foundries), employees in jobs with high silica exposure were using supplied-air respirators or air-purifying respirators with high-efficiency particulate filters (17). The Michigan Department of Health (recently renamed the Michigan Department of Consumer and Industry Services) also sent letters to 10 additional companies who were not in violation of the OSHA PEL for respirable crystalline silica, inquiring whether they had followed the workplace-specific prevention recommendations made as a result of initial SENSOR-prompted inspections for silica. The companies receiving these inquiries included nine foundries and an abrasive products manufacturer. Results of the survey, reported elsewhere, indicate that most of the recommendations had been implemented (17). Although Michigan did not validate the accuracy of this self-reported information, these results, together with the results of the reinspections, generally indicate that the prevention recommendations made by the Michigan SENSOR program are prompting silica hazard reduction.

Projects for SENSOR silicosis intervention activities also were developed by North Carolina, Texas, and Wisconsin. Although the activities and/or final reports from these projects are still in process, the primary focus of the activities in North Carolina and Wisconsin relates to assessing respirable silica exposures during road construction and maintenance activities. In Wisconsin, the primary activities of interest involve concrete and asphalt cutting operations; in North Carolina, the primary activities of interest involve rock drilling during road construction and abrasive blasting operations for bridge cleaning and maintenance. The Texas project involves a survey of companies engaged in the manufacture of cut stone and stone products to assess their potential for silica exposure, to determine the type of medical screening procedures implemented, and to identify opportunities for early case identification and silicosis prevention.

To facilitate the implementation of silicosis surveillance by additional states, efforts are in progress to refine and standardize core surveillance program elements needed to describe cases and their workplaces. Plans include the incorporation of core silicosis variables into a user-friendly software system, which can be used for data collection and reporting at the state level and for data aggregation across the states.

References

  1. Cowie RL. The epidemiology of tuberculosis in gold miners with silicosis. Am J Respir Crit Care Med 1994;150:1460-2.

  2. International Agency for Research on Cancer (1987). Overall evaluation of carcenogenicity: an updating of IARC Monographs Volumes 1-42 1987. Lyon: WHO, Supplement 7:341-3.

  3. CDC. Silicosis Surveillance-Michigan, New Jersey, Ohio, and Wisconsin, 1987-1990. MMWR 1993; 42(No. SS-5):23-8.

  4. Wagner GR, Attfield MD, Kennedy RD, Parker JE. The NIOSH B-reader certification program: an update report. J Occup Med 1992;34:879-84.

  5. International Labour Office. Guidelines for the use of ILO international classification of radiographs of pneumoconioses. Revised ed. Geneva, Switzerland: International Labour Office, 1980. Occupational Safety and Health Series 22 (Rev 80).

  6. Baker EL. SENSOR: the concept. Am J Public Health 1989; 79 (suppl):18-20.

  7. CDC. Occupational silicosis -- Ohio, 1989-1994. MMWR 1995;44(4):61-4.

  8. CDC. Silicosis: cluster in sandblasters -- Texas, and occupational surveillance for silicosis. MMWR 1990;39:433-7.

  9. Cherniac M. The Hawk's Nest incident: America's worst industrial disaster. Yale University Press: New Haven, 1986.

  10. NIOSH. Criteria for a recommended standard: occupational exposure to crystalline silica. US Department of Health, Education, and Welfare, Public Health Service, CDC, 1974; HEW publication no. (NIOSH) 75-120.

  11. CFR. Code of Federal Regulations. Washington, DC: US Government Printing Office, Office of the Federal Register.

  12. NIOSH. Work-related lung disease surveillance report, 1994. US Department of Health and Human Services, Public Health Service, CDC, 1994; DHHS(NIOSH) publication no. 94-120.

  13. NIOSH. Work-related lung disease surveillance report: supplement 1992. US Department of Health and Human Services, Public Health Service, CDC, 1992; DHHS(NIOSH) publication no. 91-113S.

  14. Rosenman KD, Reilly MJ, Watt FC. 1995 Annual report on silicosis in Michigan. Lansing: Michigan Department of Health; 1995:6-7.

  15. NIOSH. Request for assistance in preventing silicosis and deaths from sandblasting. Cincinnati, Ohio: 1992 DHHS(NIOSH) publication no. 92-102.

  16. Castranova V. Generation of oxygen radicals and mechanism of injury prevention. Environ Health Perspect 1994;102:Suppl 10:65-8.

  17. Rosenman KD, Reilly MJ, Watt FC. 1994 Annual report on silicosis in Michigan. Lansing: Michigan Department of Health; 1994: 24-5.

* NIOSH supported a cooperative agreement program for capacity building in occupational safety and health for state, territorial, and local health departments before the inception of the SENSOR program. 

** Cases ordinarily meeting the silicosis surveillance case definition are excluded on the basis of a work history indicating greater than 10 years of tenure in coal mining and less than 3 years of tenure in a silica-using industry. The coal mining exclusion criterion does not apply in Ohio if a coal mining occupation with high potential for silica exposure (e.g., roof bolter, driller, or motorman) is reported. North Carolina does not plan to apply coal mining exclusion criteria. 

*** This differential risk for silicosis is exemplified by the history of the construction of the Gauley Bridge Tunnel in southern West Virginia during 1930-31. Congressional reports revealed that 476 workers died of silicosis during the construction of the tunnel, and another 1,500 developed silicosis within a few years after the tunnel project was completed. The silica content of the rock drilled for the tunnel was high (up to 99.44% silica). Labor force figures indicate that of the nearly 5,000 men who worked on the tunnel project, more than half performed some work underground (i.e., inside the tunnel). Underground work, which included such jobs as rock drilling and mucking (removing pulverized rock left from drilling), placed a worker at high risk for silicosis. Black workers were largely unskilled, worked primarily as laborers, and were more likely than white workers to have worked underground. Although 66% of the labor force for the tunnel was made up of black males, this group composed 80% of the underground workers. 

**** Criteria for prioritization of workplace follow-up include age of person with the case, disease severity, number of years employed at workplace with potential for exposure, and number of cases associated with workplace. 

@ The Michigan OSHA program is organizationally located within the Michigan Department of Health (recently renamed the Michigan Department of Consumer and Industry Services); therefore, the results of Michigan OSHA inspections are readily available to the Michigan SENSOR program. 

@@ The NIOSH REL for respirable crystalline silica is 0.05 mg/m3 (or 50 ug/m3) as a time-weighted average (TWA) for up to 10 hours per day during a 40-hour work week. This REL is intended to prevent silicosis (10). 

@@@ The current OSHA PEL as an 8-hour TWA for crystalline silica (as respirable quartz) is either 10 mg/m3 divided by the value "% silicon dioxide + 2" for general industry {29 Code of Federal Regulations (CFR) 1910.1000} or 250 million particles per cubic foot divided by the value "% silicon dioxide + 5" for construction {29 CFR 1926.55} and shipyard employment {29 CFR 1915.5} (11). 

@@@@ For metal and nonmetal surface and underground mines, the MSHA PEL (in mg/m3) for respirable dust (30 CFR 56.500) is calculated by dividing 10 by the quantity "% crystalline silica + 2" (11).

Table_1
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TABLE 1. Year silicosis became reportable, mandated reporters, and year active solicitation efforts were
initiated, by state, 1978-1994 *
==================================================================================================================
State            Year required to report  Mandated reporters    Year Reports Solicited: Sources of Reports
------------------------------------------------------------------------------------------------------------------
Illinois         NR                       NA                    1993: Physicians, hospitals
Michigan         1978                     Physicians, hospitals 1988: Physicians, hospitals, clinics, employers
                                            clinics, employers
New Jersey       1985: Hospitals          Hospitals, physicians 1985: Hospitals
                 1990: Physicians                               1988: Physicians
North Carolina   1994                     Physicians            1994: Physicians, hospitals
Ohio             1990                     Physicians            1989: Physicians
                                                                1993: Hospitals
Texas            1985                     Physicians            1992: Physicians
Wisconsin        --                       Physicians            1988: Physicians
------------------------------------------------------------------------------------------------------------------
NR = silicosis not required to be reported
NA = category not applicable
-- Specific year unknown, but before 1987

* Active solicitation efforts are facilitated through NIOSH-funded SENSOR programs, which began in 1987, or
  through capacity-building cooperative agreements, which were initiated in 1984 and were the model for the
  SENSOR program.
==================================================================================================================

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Table_2
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TABLE 2. Distribution of confirmed silicosis cases, by race, sex, and state -- 1993
=============================================================================================================================================================
                       IL *             MI *              NJ *            NC + &             OH * +            TX +               WI +            Total
                  -------------   --------------    --------------    --------------    --------------   --------------     -------------   -----------------
Race/Sex          No.       (%)    No.       (%)     No.       (%)    No.        (%)     No.       (%)    No.       (%)     No.       (%)     No.       (%)
-------------------------------------------------------------------------------------------------------------------------------------------------------------
White male         22    (73.3)     23    (46.0)      22    (78.6)      2    (100.0)      73    (75.3)     35    (83.3)       4    (57.1)     181    (70.7)
White female       --     (0.0)      1     (2.0)       1     (3.6)     --      (0.0)       4     (4.1)      1     (2.4)       1    (14.3)       8     (3.1)
Black male          7    (23.3)     24    (48.0)       3    (10.7)     --      (0.0)      18    (18.6)      6    (14.3)       1    (14.3)      59    (23.0)
Black female       --     (0.0)     --     (0.0)       2     (7.1)     --      (0.0)       1     (1.0)     --     (0.0)      --     (0.0)       3     (1.2)
Other race
 Male               1     (3.3)      2     (4.0)      --     (0.0)     --      (0.0)      --     (0.0)     --     (0.0)      --     (0.0)       3     (1.2)
 Female            --     (0.0)     --     (0.0)      --     (0.0)     --      (0.0)      --     (0.0)     --     (0.0)      --     (0.0)      --     (0.0)
Unknown race
 Male              --     (0.0)     --     (0.0)      --     (0.0)     --      (0.0)       1     (1.0)     --     (0.0)       1    (14.3)       2     (0.8)
 Female            --     (0.0)     --     (0.0)      --     (0.0)     --      (0.0)      --     (0.0)     --     (0.0)      --     (0.0)      --     (0.0)
Total              30   (100.0)     50   (100.0)      28   (100.0)      2    (100.0)      97   (100.0)     42   (100.0)       7   (100.0)     256   (100.0)
-------------------------------------------------------------------------------------------------------------------------------------------------------------
* Solicits reports of silicosis diagnoses from hospitals.
+ Does not have access to computerized hospital discharge data.
& Did not solicit case reports from physicians and hospitals until 1994.
=============================================================================================================================================================

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Table_3
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TABLE 3. Initial case ascertainment sources for confirmed silicosis cases reported to state health departments in 1993, by state and case identification source year *
==========================================================================================================================================================================
                                   IL +              MI +             NJ +             NC & @           OH + &             TX &             WI &             Total
                             ---------------   --------------   ---------------   --------------   ---------------   --------------   ---------------   ------------------
Source/ Source year           No.        (%)    No.       (%)    No.        (%)    No.       (%)    No.        (%)    No.       (%)    No.        (%)     No.       (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hospital discharges
 1976-1986                     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     11     (11.3)     --     (0.0)     --      (0.0)      11     (4.3)
 1987                           3     (10.0)     --     (0.0)     --      (0.0)     --     (0.0)      2      (2.1)     --     (0.0)     --      (0.0)       5     (2.0)
 1988                           2      (6.7)     --     (0.0)     --      (0.0)     --     (0.0)      2      (2.1)     --     (0.0)     --      (0.0)       4     (1.6)
 1989                           5     (16.7)      2     (4.0)      2      (7.1)     --     (0.0)      2      (2.1)     --     (0.0)     --      (0.0)      11     (4.3)
 1990                           7     (23.3)      3     (6.0)      3     (10.7)     --     (0.0)      4      (4.1)     --     (0.0)     --      (0.0)      17     (6.6)
 1991                           4     (13.3)      4     (8.0)      3     (10.7)     --     (0.0)     33     (34.0)     --     (0.0)     --      (0.0)      44    (17.2)
 1992                          --      (0.0)     28    (56.0)      6     (21.4)     --     (0.0)     33     (34.0)      3     (7.1)     --      (0.0)      70    (27.3)
 1993                           2      (6.7)     --     (0.0)      9     (32.1)     --     (0.0)      6      (6.2)      6    (14.3)     --      (0.0)      23     (9.0)
Subtotal                       23     (76.7)     37    (74.0)     23     (82.1)     --     (0.0)     93     (95.9)      9    (21.4)     --      (0.0)     185    (72.3)
Death certificates
 1988                           1      (3.3)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       1     (0.4)
 1989                          --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)      --     (0.0)
 1990                           1      (3.3)     --     (0.0)      1      (3.6)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       2     (0.8)
 1991                           1      (3.3)     --     (0.0)      1      (3.6)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       2     (0.8)
 1992                           1      (3.3)      5    (10.0)      1      (3.6)     --     (0.0)     --      (0.0)      4     (9.5)     --      (0.0)      11     (4.3)
 1993                           1      (3.3)     --     (0.0)      2      (7.1)      2   (100.0)     --      (0.0)      5    (11.9)     --      (0.0)      10     (3.9)
Subtotal                        5     (16.6)      5    (10.0)      5     (17.9)      2   (100.0)     --      (0.0)      9    (21.4)     --      (0.0)      26    (10.2)
Physician reports
 1992                          --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)      3     (42.9)       3     (1.2)
 1993                          --      (0.0)      5    (10.0)     --      (0.0)     --     (0.0)      2      (2.1)     23    (54.8)      4     (57.1)      34    (13.3)
Subtotal                       --      (0.0)      5    (10.0)     --      (0.0)     --     (0.0)      2      (2.1)     23    (54.8)      7    (100.0)      37    (14.5)
Workers' Compensation
 1988                          --      (0.0)      1     (2.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       1     (0.4)
 1992                          --      (0.0)      2     (4.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       2     (0.8)
Subtotal                       --      (0.0)      3     (6.0)     --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)       3     (1.2)
Other health-care provider
 1993                           2      (6.7)     --     (0.0)     --      (0.0)     --     (0.0)     --      (0.0)      1     (2.4)     --      (0.0)       3     (1.2)
SHD referrals
 1993                          --      (0.0)     --     (0.0)     --      (0.0)     --     (0.0)      2      (2.1)     --     (0.0)     --      (0.0)       2     (0.8)

Total                          30    (100.0)     50   (100.0)     28    (100.0)      2   (100.0)     97    (100.0)     42   (100.0)      7    (100.0)     256   (100.0)
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Source year represents the year of hospital discharge, death, diagnosis by health care reporter, or year of workers' compensation claim for silicosis.
+ Solicits reports of silicosis diagnoses from hospitals.
& Does not have access to computerized hospital discharge data.
@ Did not solicit case reports from physicians and hospitals until 1994.
==========================================================================================================================================================================

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Table_4
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TABLE 4. Primary industry reported as source of silica exposure for silicosis cases, by state, 1993
========================================================================================================================================================================================================================
                                                                       IL                 MI                 NJ                NC                 OH                TX                  WI                Total
                                                               ------------------    --------------    --------------    ---------------    --------------    ---------------     ----------------  --------------------
Industry (SIC * code)                                           No.         (%)      No.       (%)     No.       (%)      No.        (%)     No.       (%)     No.        (%)      No.       (%)     No.        (%)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Manufacturing
Primary metals (33)                                               9       (30.0)      37     (74.0)       6    (21.4)      --      (0.0)      45     (46.4)      --      (0.0)       6     (85.7)     103     (40.2)
Stone, clay, glass and concrete products (32)                     3       (10.0)       2      (4.0)       8    (28.6)       1     (50.0)      19     (19.6)      --      (0.0)       1     (14.3)      34     (13.3)
Industrial and commercial machinery and computer equipment (35)   1        (3.3)       1      (2.0)       1     (3.6)      --      (0.0)       5      (5.2)       9     (21.4)      --      (0.0)      17      (6.6)
Fabricated metal products, except machinery and                   3       (10.0)      --      (0.0)       1     (3.6)      --      (0.0)       7      (7.2)       2      (4.8)      --      (0.0)      13      (5.1)
 transportation equipment (34)
Other Manufacturing                                               3       (10.0)       2      (4.0)       4    (14.3)      --      (0.0)       5      (5.2)       7     (16.7)      --      (0.0)      21      (8.2)
(28,30,36,37)
Subtotal Manufacturing                                           19       (63.3)      42     (84.0)      20    (71.4)       1     (50.0)      81     (83.5)      18     (42.9)       7    (100.0)     188     (73.4)

Construction
 Construction, special trade contractors (17)                     2        (6.7)       3      (6.0)       1     (3.6)      --      (0.0)       7      (7.2)       3      (7.1)      --      (0.0)      16      (6.3)
 Other Construction (15,16)                                      --        (0.0)       2      (4.0)       2     (7.1)      --      (0.0)      --      (0.0)       4      (9.5)      --      (0.0)       8      (3.1)
 Subtotal Construction                                            2        (6.7)       5     (10.0)       3    (10.7)      --      (0.0)       7      (7.2)       7     (16.7)      --      (0.0)      24      (9.4)
Mining
 Mining and quarrying of nonmetallic minerals (14)                4       (13.3)      --      (0.0)       3    (10.7)       1     (50.0)       6      (6.2)      --      (0.0)      --      (0.0)      14      (5.5)
 Other Mining (10,13)                                             1        (3.3)       2      (4.0)       1     (3.6)      --      (0.0)      --      (0.0)       1      (2.4)      --      (0.0)       5      (2.0)
 Subtotal Mining                                                  5       (16.6)       2      (4.0)       4    (14.3)       1     (50.0)       6      (6.2)       1      (2.4)      --      (0.0)      19      (7.5)
Other Industries
 (40,47,59,76,80)                                                 4       (13.3)      --      (0.0)       1     (3.6)      --      (0.0)      --      (0.0)      --      (0.0)      --      (0.0)       5      (2.0)
Unknown Industries                                               --        (0.0)       1      (2.0)      --     (0.0)      --      (0.0)       3      (3.1)      16     (38.1)      --      (0.0)      20      (7.8)

Total                                                            30      (100.0)      50    (100.0)      28   (100.0)       2    (100.0)      97    (100.0)      42    (100.0)       7    (100.0)     256    (100.0)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* 1987 Standard Industrial Classification
========================================================================================================================================================================================================================

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Table_5
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TABLE 5. State health department follow-up of workplaces identified as being associated with silica exposure for 256 silicosis cases ascertained in 1993, by state *
==================================================================================================================================================================================
                                            IL               MI +               NJ                NC               OH                TX               WI              Total
                                     ---------------    --------------   ---------------   ---------------   -------------  -----------------   -------------      ---------------
Number of primary workplaces           No.       (%)     No.       (%)    No.       (%)     No.       (%)    No.       (%)     No.       (%)    No.       (%)      No.       (%)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
No longer in operation                  15    (50.0)      18    (54.5)     14    (58.3)       1    (50.0)     33    (45.2)      --                1    (16.7)       82    (42.7)
No longer using silica                   2     (6.7)      --                4    (16.7)      --                2     (2.7)      --               --                  8     (4.2)
Inspected by SHD                         1     (3.3)      --                3    (12.5)       1    (50.0)      4     (5.5)      --               --                  9     (4.7)
Referred to OSHA                        --                 5    (15.2)     --                --                2     (2.7)       7    (29.2)      5    (83.3)       19     (9.9)
Routinely inspected by MSHA              2     (6.7)       1     (3.0)     --                --                4     (5.5)      --               --                  7     (3.6)
Assigned low priority for follow-up     10    (33.3)      --               --                --                8    (11.0)      --               --                 18     (9.4)
Transient building trades workplace     --                 5    (15.2)     --                --                1     (1.4)      --               --                  6     (3.1)
Other &                                 --                 4    (12.1)      3    (12.5)      --               19    (26.0)      17    (70.8)     --                 43    (22.4)

Total                                   30   (100.0)      33   (100.0)     24   (100.0)       2   (100.0)     73   (100.0)      24   (100.0)      6   (100.0)      192   (100.0)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Provisional data as of December 1994.
+ Michigan OSHA is organizationally located within the Michigan Department of Consumer and Industry Services, formerly the Michigan Department of Health.
& For Michigan, this category includes two unspecified employers and two out-of-state workplaces.
  For New Jersey, this category includes three out-of-state workplaces.
  For Ohio, this category includes four workplaces to which entry was denied, five workplaces that SHD staff were unable to locate, and 10 workplaces for which follow-up is
  pending.
  For Texas, this category includes 17 workplaces identified through review of hospital medical records or death certificates, and confirmation of workplace-specific information
  is incomplete.

-- Indicates no workplaces in the category.
SHD = State health department.
OSHA = Occupational Safety and Health Administration.
MSHA = Mine Safety and Health Administration.
==================================================================================================================================================================================

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Table_6
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TABLE 6. Distribution of 14 silica-related workplace inspections conducted by state health departments and Michgan OSHA and results of airborne silica level
measurements, by state * +
==============================================================================================================================================================
                                       IL              MI              NJ               NC              OH              TX            WI            Total
                                  ------------    -------------    ------------    -------------    -----------    -----------   -----------      ------------
Number of primary workplaces       No.     (%)     No.      (%)    No.      (%)     No.      (%)    No.     (%)     No.    (%)    No.    (%)      No.     (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Inspected                             1   (3.3)       5   (15.2)      3   (12.5)       1   (50.0)      4   (5.5)      --            --              14   (7.3)
Inspected workplaces where
 Airborne silica levels measured     --               5               3                1               1              --            --              10
 Silica levels exceeded REL          --               5               3               NA               1              --            --               9
 Silica levels exceeded PEL          --               3               2               NA               1              --            --               6
--------------------------------------------------------------------------------------------------------------------------------------------------------------
* Provisional data as of December 1994.
+ The Michigan OSHA program is organizationally located within the Michigan Department of Health. Michigan OSHA inspection reports are readily available to
  the Michigan SENSOR program.

-- Indicates no workplaces in this category.
NA = airborne silica measurements taken at this workplace did not exceed the federal permissible exposure limits or the NIOSH recommended exposure limit
for respirable crystalline silica.
OSHA = Occupational Safety and Health Administration.
==============================================================================================================================================================

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