Epidemiologic investigation of respiratory morbidity at a nylon flock plant.

BACKGROUND: A cluster of biopsy-confirmed interstitial lung disease among workers at a nylon flock plant led to a request for National Institute for Occupational Safety and Health investigators to conduct a health hazard evaluation. METHODS: Part of the overall evaluation, reported here, involved a cross-sectional medical survey of current employees. The survey consisted of a questionnaire, spirometry and diffusing capacity testing, and chest radiograph. RESULTS: Workers assigned to production and maintenance jobs reported frequent eye and throat irritation, respiratory symptoms, and systemic symptoms (i.e., generalized aches and fevers). Most reported improvement when away from work. Frequent respiratory/systemic symptom prevalence was significantly associated with departmental category, with days and hours worked per week, and with working on a flocking range. Compared to asymptomatic workers, symptomatic workers had similar mean ratios of forced expiratory volume in one second to forced vital capacity, but lower mean percent of predicted values for both forced vital capacity and diffusing capacity. All acceptable chest radiographs were classified as category 0 for small opacities. CONCLUSIONS: Findings of this study, along with those from studies reported elsewhere, implicate occupational exposure to flock-associated dust as a significant respiratory health hazard at this plant.

Nylon flock-associated interstitial lung disease.

A work-related interstitial lung disease has been diagnosed in workers at five nylon flock facilities in three different states and a Canadian province. The National Institute for Occupational Safety and Health hosted a workshop at which consulting pulmonary pathologists reviewed lung tissue samples from all the cases for which lung biopsy material was available (15 of 20 cases known in January 1998). After independent review and scoring of these lung tissue specimens, the pathologists reached consensus that the histopathological findings revealed a characteristic lesion-a lymphocytic bronchiolitis and peribronchiolitis with lymphoid hyperplasia represented by lymphoid aggregates. The pathologists noted that the pathological findings were distinctive when compared with known lung conditions. The clinical presentation for the cases generally included cough, dyspnea, restrictive ventilatory defect with reduction in diffusing capacity, and interstitial markings on chest radiographs or high-resolution computed tomography (HRCT) scans. Six of the cases improved after removal from workplace exposure without medical treatment. Six others, who had recovered with medical treatment and removal from the workplace, had relapses in both symptoms and objective findings after attempting to return to nylon flock work. With this and other evidence supporting the existence of chronic interstitial pneumonitis associated with nylon flock processing, workshop participants recommended surveillance for early identification of affected workers and their removal from further workplace exposure.

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

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 < or = 10 years in such jobs and 156 (81%) were employed > or = 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, 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.

Mortality of a cohort of U.S. workers employed in the crushed stone industry, 1940-1980.

The mortality of 3,246 males who had been employed 1 or more years during 1940-1980 at 20 crushed stone operations was evaluated for possible association between employment and death from lung cancer, pneumoconiosis, and other respiratory diseases. Four deaths were attributed to pneumoconiosis. Based on available work histories, at least two of these deaths were probably due to dust exposures in the crushed stone industry. Mortality attributed to pneumoconiosis and other nonmalignant respiratory diseases, including chronic obstructive lung disease, was significantly increased overall (SMR: 1.98; 95% CI: 1.21-3.05), and especially so for a subcohort of crushed stone workers that processed granite (SMR: 7.26; 95% CI: 1.97-18.59). With regard to lung cancer, overall SMRs were elevated (although not statistically significant). Analyzed by rock type, there was a significantly elevated lung cancer SMR among granite workers with at least 20 years latency (SMR: 3.35; 95% CI: 1.34-6.90). Although not definitive, results of this study are consistent with the hypothesis that exposure to respirable silica dust is a risk factor for lung cancer.

Silicosis and lung cancer among workers in North Carolina dusty trades.

In 1940-1983, 760 cases of silicosis were identified among male North Carolina (NC) workers in dusty trades. Vital status was ascertained through 1983 for 714 silicotics, and death certificates were obtained for 546 of the 550 decedents. The standardized mortality ratio (SMR) for lung cancer based on United States rates was 2.6 [95% confidence interval (95% CI) 1.8-3.6] for whites, 2.3 (95% CI 1.5-3.4) for whites unexposed to other known occupational carcinogens, and 2.4 (95% CI 1.5-3.6) for whites with no other exposure and diagnosed with silicosis while still employed in dusty trades. In addition, the age- and smoking-adjusted rate for silicotics was 3.9 times higher (95% CI 2.4-6.4) than that of nonsilicotic metal miners. This analysis effectively controlled for confounding by age, cigarette smoking, exposure to other occupational carcinogens, and detection bias. The results congrue with the hypothesis of an association between silicosis and lung cancer.

Surveillance for occupational asthma--Michigan and New Jersey, 1988-1992.

PROBLEM/CONDITION: A case of occupational asthma is a sentinel health event indicating a need for preventive intervention. REPORTING PERIOD COVERED: 1988-1992. 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 in 1987, state-based surveillance and intervention programs for occupational asthma (OA) have been under development in Michigan and New Jersey. The initial 5-year projects in these states have been completed. RESULTS: From 1988 through 1992, the SENSOR programs in these states identified a total of 535 cases of occupational asthma and related conditions. Of these 535 cases, 328 cases met the SENSOR surveillance case definition for OA. In addition, 128 cases were classified as possible OA, 42 as reactive airways dysfunction syndrome, and 37 as occupationally aggravated asthma. In both Michigan and New Jersey, manufacturing was the industrial sector with the largest proportion of cases. In Michigan, > 40% of the case-patients worked in transportation equipment manufacturing. In New Jersey, 15% of case-patients worked in manufacturing of chemicals and allied products. Overall, isocyanates were the most frequently reported asthma-causing agents (19.4% of cases). Follow-up industrial hygiene sampling measured suspect agents at airborne concentrations generally below the permissible exposure limits established by the Occupational Safety and Health Administration. INTERPRETATION: In its first 5 years, the SENSOR system has led to the identification of previously unrecognized causes of occupational asthma. Overall findings indicate the need for more comprehensive control of such well-known occupational allergens as the isocyanates. In addition, SENSOR interventions have prompted improvements in protection for workers. ACTIONS TAKEN: Approaches to state-based surveillance and intervention for OA are being developed through newly funded 5-year SENSOR projects in four states (California, Massachusetts, Michigan, and New Jersey). The goal is to develop a model for effective state-based OA surveillance that can be applied by any state health department.

Epidemiological data on US coal miners' pneumoconiosis, 1960 to 1988.

OBJECTIVES: Statistics on prevalence of pneumoconiosis among working underground coal miners based on epidemiologic data collected between 1960 and 1988 are presented. The main intent was to examine the time-related trend in prevalence, particularly after 1969, when substantially lower dust levels were mandated by federal act. METHODS: Data from studies undertaken between 1960 and 1968 were collected and compared. Information for the period 1969 to 1988 was extracted from a large ongoing national epidemiologic study. Tenure-specific prevalence rates and summary statistics derived from the latter data for four consecutive time intervals within the 19-year period were calculated and compared. RESULTS: The results indicate a reduction in pneumoconiosis over time. The trend is similar to that seen in a large radiologic surveillance program of underground miners operated concurrently. CONCLUSIONS: Although such factors as x-ray reader variation, changes in x-ray standards, and worker self-selection for examination may have influenced the findings to some extent, adjusted summary rates reveal a reduction in prevalence concurrent with reductions in coal mine dust levels mandated by federal act in 1969.

Reevaluation of silicosis and lung cancer in North Carolina dusty trades workers.

We previously reported on the lung cancer mortality through 1983 of 760 males who were diagnosed with silicosis during 1930-1983 by the State of North Carolina's medical examination program for dusty trades workers. The lung cancer SMR (95% confidence interval) was 2.6 (1.8-3.6) among 655 white members of this group. In this paper, we report the results of a reanalysis of mortality among a subgroup for whom chest radiographs were currently available for rereading. Technically acceptable radiographs were available for 306 white males and were independently reclassified for pneumoconiosis by 3 "B" readers using the 1980 ILO Classification. Lung cancer SMRs were 1.7 (0.8-3.1) for the entire group of 306 white males, 2.5 (1.1-4.9) for 143 subjects reclassified as simple silicosis, and 1.0 (0.1-3.5) for 96 subjects whose radiographs were reclassified as ILO category 0. There were no lung cancer deaths among 67 subjects whose radiographs were reclassified as progressive massive fibrosis. Corresponding lung cancer SMRs for subjects who had never been employed in a job with exposure to known occupational carcinogens were 1.2 (0.2-4.4) for those reclassified as category 0, and 2.4 (1.0-5.0) for those reclassified as having simple silicosis. The age-adjusted lung cancer rate ratio among subjects with simple silicosis compared to those with category 0 was 1.5 (0.4-5.8). Our findings from this reanalysis, which effectively controls for misclassification of silicosis due to errors in radiograph interpretation by North Carolina program readers, offer additional evidence consistent with the hypothesis of an association between silicosis and lung cancer in this study group.

Victoria M. Trasko: champion of state-based surveillance of occupational diseases in the United States, 1937 to 1971.

Victoria M. Trasko (1907-1979), a relatively unknown figure to many currently practicing occupational health specialists, was a pioneer in state-based surveillance of occupational diseases in the United States. To highlight her accomplishments during her career with the United States Public Health Service from 1937 to 1971, this report briefly reviews her publications on occupational disease surveillance. Her span of work includes guidelines for state industrial hygiene programs, numbers of workers in state occupational health programs, compilation of state and local laws related to industrial hygiene, proposals for standardized reporting of occupational disease, and analysis of trends in workers' compensation and mortality statistics for occupational diseases. She pilot tested the first state-based model system for occupational disease reporting in the United States. She documented the great difficulty experienced by states in getting physicians to report cases of occupational diseases, and pointed out that surveillance of other existing data sources was worthwhile, at least for some occupational diseases. She was the first to report on the distribution of silicosis cases in the United States by state, industry, and job title. She was the first to comment on mortality trends for the pneumoconioses and to document problems in comparability between different International Classification of Disease (ICD) periods.

Changes in forced expiratory volume in one second and peak expiratory flow rate across a work shift among unexposed blue collar workers.

Pre- and postshift spirometry was obtained on 1,113 blue collar workers employed at 35 work sites judged to have no hazardous occupational respiratory exposures on the basis of inspection visits and environmental sampling. In addition to spirometry, a standardized questionnaire was administered by trained personnel. A study population of 944 remained after exclusion of workers for incomplete demographic data and/or spirometry with poor within-session reproducibility, i.e., greater than or equal to 10% variability in the two largest values of either FVC and/or FEV1. Overall mean values of changes across the work shift in FEV1 and peak expiratory flow rate (PEFR) were -0.8% (-0.04 L) and +2.1% (+0.13 L/s), respectively. Standard deviations for these across-shift changes were 5.8% (0.19 L) and 13.2% (1.19 L/s) for FEV1 and PEFR, respectively. In univariate analyses, mean values of across-shift changes were not statistically related to age, race, sex, smoking status, work shift, or FEV1/FVC ratio. However, variability (i.e., standard deviation) of across-shift changes were significantly related to some of these factors. These observations provide a basis for interpreting results of occupational respiratory morbidity surveys involving measurement of changes in FEV1 and/or PEFR across a work shift.

Inhaled endotoxin and decreased spirometric values. An exposure-response relation for cotton dust.

The early stages of byssinosis, the chronic lung disorder caused by the inhalation of cotton dust, are characterized by repeated episodes of mild and reversible obstruction of airways on exposure to cotton dust. To define the relation between exposure to endotoxin and the airway response to inhaled cotton dust, we pooled and analyzed data from several previous studies of experimental exposure. The pooled data set involved a total of 108 separate sessions of exposure to dust and 32 different cottons. Each dust-exposure session had involved exposing a group of 24 to 35 prescreened healthy subjects to dust from one of the cottons for six hours. The following data were obtained for each session: average concentrations of airborne dust (range, 0.12 to 0.55 mg per cubic meter) and endotoxin (range, 6 to 779 ng per cubic meter) as determined in air samples collected by vertical elutriators, and group mean percentage change in forced expiratory volume in one second (range, +0.5 to -9.1 percent), as determined by preexposure and postexposure spirometry. When data from the 108 exposure sessions were pooled, the dust concentration was not correlated with the group mean percentage change in forced expiratory volume in one second (r = -0.08; P = 0.43). In contrast, a clear exposure-response relation was observed between endotoxin concentration and group mean percentage change in forced expiratory volume in one second (r = -0.74; P less than 0.0001). Logarithmic transformation of endotoxin values clarified this relation at low-exposure concentrations and improved the correlation (r = -0.85; P less than 0.0001). Our observations strongly support the hypothesis that endotoxin has a causative role in the acute pulmonary response to inhaled cotton dust.

Knuckle pads in live-chicken hangers.

A study of live-chicken hangers in a poultry processing plant demonstrated a high prevalence of callosities over the knuckles (knuckle pads) of both hands. Knuckle pads were observed in 56% (23/41) of live-chicken hangers, but in no (0/41) workers from other departments (p less than 0.001). The probable cause was the repeated striking and sliding of the knuckles against metal shackles in which live birds were being placed. Additional medical and ergonomic evaluation would be worthwhile to confirm the probable cause, to determine whether associated tissue disorders are present in the digits of chicken hangers who develop knuckle pads, and to suggest preventive measures.

Spirometry variability criteria--association with respiratory morbidity and mortality in a cohort of coal miners.

To clarify the association between spirometry variability and respiratory morbidity and mortality, the authors analyzed data for miners examined in the first round of the National Coal Study, 1969-1971, and they compared groups of miners who failed with those who met each of two spirometry variability criteria: a 5% criterion recommended by the American Thoracic Society, and a 200 ml criterion used in prior research studies. Compared with miners who met the 5% criterion (the best two forced vital capacities must be within 5% or 100 ml of one another), the group that failed had a lower mean for forced expiratory volume in one second (FEV1), and odds ratios for cough, phlegm, wheeze, shortness of breath, and death of 1.75, 1.67, 1.76, 2.71, and 1.30, respectively. The findings for the 200 ml criterion (the best two FEV1s must be within 200 ml of one another) were somewhat different. The group that failed versus the group that met this criterion had a higher mean for FEV1, and odds ratios for cough, phlegm, wheeze, shortness of breath, and death of 1.13, 1.07, 1.15, 1.43, and 0.94, respectively. Although the findings differ for the two criteria, the findings demonstrate that increased spirometry variability is associated with poorer health.

Respiratory health status of gilsonite workers.

Gilsonite, a solidified hydrocarbon used in the manufacture of automotive body seam sealers, is mined only in the Uinta Basin of Eastern Utah and Western Colorado. Health effects of gilsonite dust exposure have not previously been published and exposure to gilsonite dust is not regulated. To examine potential respiratory health effects associated with gilsonite dust exposures, this cross-sectional study surveyed the 100 current male employees who had been exposed to gilsonite dust at 3 existing gilsonite companies. Total dust exposures up to 28 times the nuisance dust standard were found, and 5 of 99 (5%) workers had chest radiographs consistent with pneumoconiosis of low profusion. Increased prevalences of cough and phlegm were found in workers with high-exposure jobs, but no evidence for dust-related pulmonary function impairment was noted. To prevent pulmonary health effects, we recommend reducing dust exposures for those workers in jobs currently characterized by relatively high dust exposures.

Effect of spirometer temperature on measurement of FEV1 shift changes.

Spirometric parameters are generally obtained at ambient (spirometer) temperature pressure saturated (ATPS) and then converted to body temperature pressure saturated (BTPS) by multiplying each observed value by a BTPS correction factor. At ambient temperatures of 23 degrees C or higher, the accepted practice of using a constant BTPS factor introduces a relatively small error in forced expiratory volume in one second (FEV1), but as the temperature decreases below 23 degrees C the error in FEV1 increases. A dynamic BTPS correction factor model has recently been developed to reduce this error. Analysis of across-shift spirometry data from a recent survey indicates that, with an increase in temperature over a work shift of greater than 3 degrees C, 27.1% of 302 subjects were classified as having a greater than or equal to 5% FEV1 drop over the shift using the dynamic BTPS factor model, compared with 41.4% when the standard BTPS correction factor was used (P less than .005). These results indicate the importance of correcting for ambient temperature differences when analyzing for shift changes in spirometric parameters.