Current Trends Occupational Silicosis -- Ohio, 1989-1994

Silicosis is a chronic lung disease associated with the inhalation and pulmonary deposition of dust that contains crystalline silica. Through the Sentinel Event Notification System for Occupational Risks (SENSOR) * program, CDC's National Institute for Occupational Safety and Health (NIOSH) is assessing practical models for implementing state-based surveillance of silicosis and linking follow-up intervention activities to surveillance reports. From 1989 through 1992, the Ohio Department of Health (ODH) SENSOR program identified silicosis cases through reports of Bureau of Workers' Compensation (BWC) claims, physician reports, and death certificates. The addition in 1993 of hospital discharge reports as an ascertainment source resulted in a substantial increase in the number of silicosis case reports identified annually Table_1. This report describes the investigation of a case of occupational silicosis in Ohio and summarizes the impact of hospital-based reporting on surveillance for silicosis in Ohio during 1993-1994. Case Report

In September 1991, a case report ** was sent to ODH by an infectious disease specialist who was treating a 55-year-old sandblaster with advanced silicosis and an associated Mycobacterium kansasii infection *** (2). In January 1992, NIOSH and ODH conducted a joint investigation at the worker's place of employment -- a metal preparation shop -- to evaluate current levels of exposure to respirable crystalline silica and to screen co-workers for silicosis. The investigation detected excessive exposures to respirable crystalline silica (2-5). Chest radiology revealed radiographic abnormalities consistent with pneumoconiosis in four of 16 current and former workers (including one case of advanced silicosis {International Labour Organization, category C (6)}). At the time of the initial survey, ODH recommended that the company discontinue use of silica sand in abrasive blasting operations. In March 1992, the company substituted aluminum oxide for silica sand in all abrasive blasting operations. Direct Hospital Discharge Reporting

In February 1993, ODH designated silicosis as a disease warranting special assessment; although not requiring reporting by hospitals, this designation authorized ODH surveillance staff to gain access to medical records of persons with potential cases. In April 1993, ODH notified all general (i.e., nonpediatric and nonpsychiatric) hospitals by mail about this designation and requested copies of medical records of all patients who had been discharged since March 1991 with a primary or secondary diagnosis coded as "Pneumoconiosis due to silica or silicates" (International Classification of Diseases, Ninth Revision {ICD-9}, code 502). In response, hospitals sent the discharge records of 262 suspected silicosis cases for the period covered by the initial request (through 1993); ODH determined that 257 (98%) of these were unique cases that did not duplicate cases reported by the other sources Table_1. An additional 147 cases (all of which were unique reports) were forwarded by hospitals during 1994 in response to a similar request mailed in March 1994. For 1993-1994, OHD received a total of 404 suspected silicosis cases that were reported only by hospitals; all other sources combined reported a total of 24 cases during these 2 years.

Of the 404 hospital-based reports, 99 (24%) were confirmed **** as silicosis using information contained in the hospital records and, for some cases, direct contacts with discharged patients. An additional 69 (17%) cases met the objective medical criterion specified in the silicosis surveillance case definition; however, final confirmation for these is pending verification of a history of occupational exposure to airborne silica dust. Reported by: E Socie, MS, A Migliozzi, MSN, S Wagner, MPH, TJ Halpin, MD, State Epidemiologist, Ohio Dept of Health. Epidemiological Investigations Br, Div of Respiratory Disease Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: The findings in this report demonstrate the potentially crucial role of direct hospital discharge reporting in surveillance for silicosis. In particular, compared with other information sources (e.g., computerized death certificate reviews and reports of BWC claims), advantages of hospital discharge-based reporting for silicosis are 1) case reports are submitted to ODH on a more timely basis -- an action that is necessary to enable follow-up investigations, such as that described in this report, and 2) this source enables the provision of clinical information that is necessary for case confirmation. Although reports from physicians also are similarly useful, hospitals are more likely than physicians to report cases.

Other states have used direct hospital discharge reporting for surveillance for occupational asthma (7). Because occupational-related information is usually not included in hospital medical records, a phone interview is conducted with persons with identified cases to determine if the condition was work related. This approach to case identification may be useful for other conditions (e.g., asbestosis and coal workers' pneumoconiosis).

Hospital discharge data-based reporting for silicosis is subject to at least three limitations. First, most persons with silicosis are not hospitalized at the time of initial diagnosis and, therefore, will not be identified by hospital-based reporting during early stages of disease. Second, silicosis may not be entered as a discharge diagnosis if it is an incidental diagnosis and not a primary reason for hospitalization or if it is not mentioned in the patient's past medical history. Third, Ohio has no mechanism to assess completeness of direct hospital discharge reporting. Because of these limitations and to ensure complete case ascertainment, a comprehensive surveillance system for silicosis should employ other methods, including workers' compensation claim data, death certificate data, and direct physician reports.

In addition to Ohio, four other states (Illinois, Michigan, New Jersey, and Wisconsin) use hospital discharge data for silicosis surveillance; programs in Illinois and Wisconsin rely on voluntary direct reporting by physicians and hospitals while programs in Michigan and New Jersey mandate direct reporting by physicians and hospitals. In Illinois, Michigan, and New Jersey, computerized hospital discharge data also are reviewed annually, and investigation of discrepancies between cases identified through direct discharge reporting and through the review of computerized hospital discharge data tapes has enabled these states to improve ascertainment of cases and to assess underreporting by hospitals.

An important goal of the SENSOR projects for silicosis is to develop a model of silicosis surveillance that can be implemented in any state that has targeted the prevention of silicosis. Other conditions targeted by SENSOR include asthma, tuberculosis, burns, amputations, cadmium overexposure, carpal tunnel syndrome, childhood injuries, dermatitis, noise-induced hearing loss, pesticide health effects, and spinal cord injuries. Such systems most likely will require the use of multiple data sources for comprehensive case ascertainment.

References

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

2. Liston R. Silica survey report. Columbus Ohio: Ohio Department of Health, March 1992. (Computer no. 12292).

3. NIOSH. Health hazard evaluation report: commercial steel treating company. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1992; DHHS publication no. (NIOSH)92-0174-2363.

4. NIOSH. Request for assistance in preventing silicosis and deaths from sandblasting. Cincinnati: US Department of Health and Human Services, Public Health Service, CDC, 1992; DHHS publication no. (NIOSH)92-102.

5. Short S, Liston R, O'Brien D, Migliozzi N, Wagner G, Parker J. Silico-tuberculosis death in a sandblaster: the utility of the Sentinel Event Notification System for Occupational Risks (SENSOR) program. Am Rev Respir Dis 1993;147:4:A898.

6. International Labour Office. Guidelines for the use of ILO International Classification of Radiographs of pneumoconioses. Revised ed. Geneva: International Labour Office, 1980:6-7. (Occupational safety and health series 22 {Rev.80}).

7. CDC. Surveillance for occupational asthma -- Michigan and New Jersey, 1988-1992. In: CDC surveillance summaries (June). MMWR 1994;43(no. SS-1):9-17.

* SENSOR is a program of cooperative agreements with state health departments to develop surveillance and intervention strategies for selected occupational conditions. The National Institute for Occupational Safety and Health currently supports SENSOR silicosis programs in seven states (Illinois, Michigan, New Jersey, North Carolina, Ohio, Texas, and Wisconsin). 

** Case reports should be submitted for persons with a physician's provisional diagnosis of silicosis, a chest radiograph interpreted as consistent with silicosis, or pathologic findings consistent with silicosis (1). 

*** Silicosis is often complicated by severe Mycobacterium infections (e.g., M. tuberculosis, M. kansasii, and M. avium complex). 

**** Case confirmation requires 1) a history of occupational exposure to airborne silica dust (exposure criterion) and 2) either a chest radiograph consistent with silicosis or pathologic findings characteristic of silicosis (medical criterion) (1).

TABLE 1. Silicosis reports, by initial reporting source and year of ascertainment * -- Ohio, 1989-1994
==============================================================================================================
                 1989 +         1990         1991         1992         1993         1994         Total
Reporting      ------------  ----------   ----------   ----------  -----------   -----------  -----------
 source        No.    (%)    No.    (%)   No.    (%)   No.    (%)   No.    (%)    No.    (%)   No.    (%)
---------------------------------------------------------------------------------------------------------
Hospital       --            --           --           --          257 ( 93.1)   147 ( 96.7)  404 ( 71.9)
Death
 certificate    7   ( 23.3)   2 (  9.1)   18 ( 46.2)   29 ( 67.4)   12 (  4.3)    --           68 ( 12.1)
Bureau of
 Worker's
 Compensation   8   ( 25.7)   7 ( 31.8)   18 ( 46.2)   12 ( 27.9)   --            --           45 (  8.0)
Physician      15   ( 50.0)   5 ( 22.7)    3 (  7.7)    2 (  4.7)    5 (  1.8)     4 (  2.6)   34 (  6.0)
Other          --             8 ( 36.4)   --           --            2 (  0.7)     1 (  0.7)   11 (  2.0)

Total          30   (100.0)  22 (100.0)   39 (100.0)   43 (100.0)  276 (100.0)   152 (100.0)  562 (100.0)
--------------------------------------------------------------------------------------------------------------
* Reports are classified by the year in which the report is received by the Ohio Department of
  Health, rather than by the year of diagnosis or hospitalization.
+ The Sentinel Event Notification System for Occupational Risks (SENSOR) surveillance system
  was implemented in Ohio during 1988, and 1989 data may not be directly comparable with data
  for succeeding years.
==============================================================================================================

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