Biomedical subjects

K Kreiss

Publications and source records attributed to K Kreiss.

At least 19 recordsLinked to original sources

PubMed2006

Fungal and endotoxin measurements in dust associated with respiratory symptoms in a water-damaged office building.

UNLABELLED: We investigated the associations of fungal and endotoxin levels in office dust with respiratory health in 888 (67% participation) occupants of a water-damaged building. We analyzed floor and chair dusts from 338 workstations for culturable fungi and endotoxin. Based on averages, we ranked each floor of the building as low, medium, or high for occupants' exposure to each of these agents. Multivariate logistic regression models for building-related symptoms included this ranking of fungi and endotoxin, age, gender, race, smoking status, and duration of occupancy. Using floor dust measures, we found significantly increased odds for lower respiratory symptoms [wheeze, chest tightness, attacks of shortness of breath, and attacks of cough: odds ratios (OR) = 1.7 (95% confidence interval (CI): 1.02-2.77) to 2.4 (95% CI: 1.29-4.59)], throat irritation [OR = 1.7, (95% CI: 1.06-2.82)], and rash/itchy skin [OR = 3.0, (95% CI: 1.47-6.19)] in the highest fungal exposure group compared to the lowest, with generally linear exposure-response relationships. Nonlinear relationships were observed for many of these symptoms and endotoxin in floor dust. Interaction models showed that endotoxin modified effects of fungi on respiratory symptoms. Our findings of exposure interactions and exposure-response relationships of fungal and endotoxin with increased risk of building-related symptoms contribute to an understanding of the role of microbial agents in building-related asthma and respiratory and systemic symptoms. PRACTICAL IMPLICATIONS: Our demonstration of exposure-response relationships between measurements of fungi and/or endotoxin in floor dusts and building-related symptoms implies that microbial agents in floor dust may be a good surrogate measure for dampness-related bioaerosol exposure, considering that measurements of microbial agents in air often fail to demonstrate the associations between exposure and health. In addition, our finding that endotoxin exposure may change the effect of fungal exposure (and vice versa) on respiratory heath suggests that exposure to both fungi and endotoxin should be assessed in epidemiological investigations examining the effect of fungal or endotoxin exposure on respiratory health in indoor environments.

Air Pollution, Indoor↗

PubMed2004

Building-related respiratory symptoms can be predicted with semi-quantitative indices of exposure to dampness and mold.

UNLABELLED: Using a semi-quantitative mold exposure index, the National Institute for Occupational Safety and Health (NIOSH) investigated 13 college buildings to examine whether building-related respiratory symptoms among employees are associated with environmental exposure to mold and dampness in buildings. We collected data on upper and lower respiratory symptoms and their building-relatedness, and time spent in specific rooms with a self-administered questionnaires. Trained NIOSH industrial hygienists classified rooms for water stains, visible mold, mold odor, and moisture using semi-quantitative scales and then estimated individual exposure indices weighted by the time spent in specific rooms. The semi-quantitative exposure indices significantly predicted building-related respiratory symptoms, including wheeze [odds ratio (OR) = 2.3; 95% confidence interval (CI) = 1.1-4.5], chest tightness (OR = 2.2; 95% CI = 1.1-4.6), shortness of breath (OR = 2.7; 95% CI = 1.2-6.1), nasal (OR = 2.5; 95% CI = 1.3-4.7) and sinus (OR = 2.2; 95% CI = 1.2-4.1) symptoms, with exposure-response relationships. We found that conditions suggestive of indoor mold exposure at work were associated with building-related respiratory symptoms. Our findings suggest that observational semi-quantitative indices of exposure to dampness and mold can support action to prevent building-related respiratory diseases. PRACTICAL IMPLICATIONS: Current air sampling methods have major limitations in assessing exposure to mold and other biological agents that may prevent the demonstration of associations of bioaerosol exposure with health. Our study demonstrates that semi-quantitative dampness/mold exposure indices, based solely on visual and olfactory observation and weighted by time spent in specific rooms, can predict existence of excessive building-related respiratory symptoms and diseases. Relative extent of water stains, visible mold, mold odor, or moisture can be used to prioritize remediation to reduce potential risk of building-related respiratory diseases. From a public health perspective, these observational findings justify action to correct water leaks and repair water damage in order to prevent building-related respiratory diseases. This approach can also be a basis for developing practical building-diagnostic tools for water-incursion.

Adult↗

PubMed2004

Bronchiolitis obliterans syndrome in popcorn production plant workers.

Following sentinel case recognition, an excess of fixed airways obstruction was found among current workers in a microwave popcorn plant associated with butter flavouring exposures. In order to characterise the clinical presentation of sentinel cases, the medical records of sentinel cases were reviewed, interviews conducted and serial spirometric testing performed. Cases worked in microwave popcorn production, and five of the nine cases had mixed flavourings. Most had never smoked or smoked minimally. Cases showed onset of cough, shortness of breath and wheezing 5 months to 9 yrs after starting work at the popcorn plant. Initial forced expiratory volume in one second ranged 14.0-66.8% of the predicted value. Eight high-resolution computed tomography scans showed marked bronchial wall thickening and mosaic attenuation with air trapping. Open lung biopsy results were consistent with, or diagnostic of, constrictive bronchiolitis in two of three cases. Five cases are on lung transplantation waiting lists. After leaving employment, nearly all cases experienced stabilisation of their lung function within 2 yrs. Astute clinicians can help identify new causes of airways obstruction by alerting public health authorities to unexplained disease cases occurring in groups of workers.

Adult↗

PubMed2001

Respiratory symptoms among crab processing workers in Alaska: epidemiological and environmental assessment.

BACKGROUND: Crab processing workers may develop respiratory symptoms and specific IgE responses, but the risk factors have not been fully described. METHODS: In 1998, 107 workers at a crab processing facility completed a survey both at the beginning and end of the processing season. The surveys included standardized symptom questionnaires, spirometry, and serological testing, as well as measurement of workplace airborne crab allergens and microscopic analysis of aerosolized materials. RESULTS: Over the crab processing season, asthma-like symptoms developed in 26% of study participants and bronchitic symptoms in 19%. Only 9% of those with new asthma-like symptoms were IgE-sensitized to crab at the end of the season. Among the crab processing jobs, butchering and degilling workers had the highest incidence of respiratory symptoms. CONCLUSIONS: Both personal and process-related factors appear to affect the development of respiratory symptoms in crab processing workers. In this study, crab specific IgE was not detected in most of the workers with new symptoms. Published 2001 Wiley-Liss, Inc.

Adolescent↗

PubMed2001

Beryllium sensitization and disease among long-term and short-term workers in a beryllium ceramics plant.

OBJECTIVE: Workers at a beryllium ceramics plant were tested for beryllium sensitization and disease in 1998 to determine whether the plant-wide prevalence of sensitization and disease had declined since the last screening in 1992; an elevated prevalence was associated with specific processes or with high exposures; exposure-response relationships differed for long-term workers hired before the last plant-wide screening and short-term workers hired since then. METHODS: Current workers were asked to complete a questionnaire and to provide blood for the beryllium lymphocyte proliferation test (BeLPT). Those with an abnormal BeLPT were classified as sensitized, and were offered clinical evaluation for beryllium disease. Task- and time-specific measurements of airborne beryllium were combined with individual work histories to compute mean, cumulative, and peak beryllium exposures for each worker. RESULTS: The 151 participants represented 90% of 167 eligible workers. Fifteen (9.9% of 151) had an abnormal BeLPT and were split between long-term workers (8/77 = 10.4%) and short-term workers (7/74 = 9.5%). Beryllium disease was detected in 9.1% (7/77) of long-term workers but in only 1.4% (1/74) of short-term workers (P = 0.06), for an overall prevalence of 5.3% (8/151). These prevalences were similar to those observed in the earlier survey. The prevalence of sensitization was elevated in 1992 among machinists, and was still elevated in 1998 among long-term workers (7/40 = 18%) but not among short-term workers (2/36 = 6%) with machining experience. The prevalence of sensitization was also elevated in both groups of workers for the processes of lapping, forming, firing, and packaging. The data suggested a positive relationship between peak beryllium exposure and sensitization for long-term workers and between mean, cumulative, and peak exposure and sensitization for short-term workers, although these findings were not statistically significant. Long-term workers with either a high peak exposure or work experience in forming were more likely to have an abnormal BeLPT (8/51 = 16%) than the other long-term workers (0/26, P = 0.05). All seven sensitized short-term workers either had high mean beryllium exposure or had worked longest in forming or machining (7/55 = 13% versus 0/19, P = 0.18). CONCLUSIONS: A plant-wide decline in beryllium exposures between the 1992 and 1998 surveys was not matched by a decline in the prevalence of sensitization and disease. Similar to findings from other studies, beryllium sensitization/disease was associated with specific processes and elevated exposures. The contrast in disease prevalence between long-term and short-term workers suggests that beryllium sensitization can occur after a short period of exposure, but beryllium disease usually requires a longer latency and/or period of exposure. The findings from this study motivated interventions to more aggressively protect and test workers, and new research into skin exposure as a route of sensitization and the contribution of individual susceptibility.

Air Pollutants, Occupational↗

PubMed2000

Analysis of construction injury burden by type of work.

BACKGROUND: To lay groundwork for identifying patterns of injury etiology, we sought to describe injury experience associated with types of work performed at construction sites by examining workers' compensation (WC) claims for the 32,081 construction workers who built Denver International Airport (DIA). METHODS: Injury rates and WC payment rates were calculated for 25 types of work based on claims and payroll data reported to DIA's owner-controlled insurance program according to National Council on Compensation Insurance job classifications. By linking DIA claims with corresponding lost-work-time (LWT) claims filed with Colorado's Workers' Compensation Division, we were also able to obtain and examine both total and median lost days for each type of work. RESULTS: Injury experience varied widely among the types of construction work. Workers building elevators and conduits and installing glass, metal, or steel were at particularly high risk of both LWT and non-LWT injury. Median days lost by injured workers was highest (202 days) for driving/trucking. Median days lost for most types of work was much greater than previously reported for construction: 40 days or more for 18 of the 25 types of work analyzed. WC payment rates reflect both number and severity of injuries and were generally not significantly different from expected losses. They were, however, significantly higher than expected for driving/trucking, metal/steel installation, inspection/analysis, and elevator construction. CONCLUSIONS: Analysis of injury data by type of work allows targeting of safety resources to high risk construction work and would be useful in prospective surveillance at large construction sites with centrally administered workers' compensation plans.

Absenteeism↗

PubMed2000

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.

Adult↗

PubMed1999

Contractor safety practices and injury rates in construction of the Denver International Airport.

BACKGROUND: We sought to explain the variation in injury rates found for categories of companies and contracts involved in the construction of the Denver International Airport (DIA) by surveying contractors about company and contract-level safety practices. METHODS: We conducted 213 telephone interviews (83% response) with representatives of contracts with payrolls of more than $250,000. We investigated the bivariate relationship between safety actions reported in the survey and injury occurrence by calculating the aggregate injury rates (lost work-time (LWT) rates and non-LWT rates) for the group of respondent contracts reporting always taking the action and for the group not always taking the action. Using Poisson regression, we examined the association between contract injury rates and contract safety practices while controlling for variables previously shown to affect contract-level injury rates. RESULTS: In Poisson regression, two actions, 1) disciplinary action always resulting when safety rules were violated and 2) always considering experience modification ratings when selecting subcontractors, were associated with lower LWT injury rates. Three actions or contract characteristics resulted in lower non-LWT rates: management always establishing goals for safety for supervisors, conducting drug testing at times other than badging or after an accident, and completing the DIA contract on budget, rather than over budget. Reportedly consistent use of a number of accepted safety practices was associated with significantly higher injury rates in bivariate and multivariate analyses. CONCLUSIONS: The pattern of counterintuitive results found in this study suggests that questions reflecting agreed-upon safety practices, when asked of the person responsible for all on-site construction activities, are likely to elicit normative responses. Objective validation of reported safety practices is critical to evaluating their efficacy in reducing injury rates, along with measures of both time at risk and outcome and control for prevailing risk of the work performed.

Absenteeism↗

PubMed1999

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.

Adult↗

PubMed1998

Construction injury rates may exceed national estimates: evidence from the construction of Denver International Airport.

BACKGROUND: Construction of Denver International Airport (DIA) provided a unique opportunity to describe the magnitude of injury on a major construction project for which complete data on injury and hours at risk were available for over 32,000 employees working 31 million hours. METHODS: Comprehensive payroll data for all workers, who were paid standard Davis-Bacon wages, allowed calculation of person-hours at risk by job classification. Complete reporting, facilitated by a single workers' compensation plan covering all contracts and by an on-site medical clinic and designated provider system, allowed us to determine both total and lost-work-time (LWT) injury rate per 200,000 hours at risk by industrial sector, company size, and year of construction. Workers' compensation payment rates were calculated and compared with expected loss rates, derived by the National Council on Compensation Insurance, by sector, company size, and year. RESULTS: DIA's overall total injury rates were over twice those published by the Bureau of Labor Statistics (BLS) for the construction industry for each year of DIA construction. Differences in LWT injury rates were more modest. Total injury rates were also at least twice BLS's rates for all contractor sizes. The injury rate pattern by company size at DIA differed from BLS's in that small firms had injury rates that were lower than or comparable to most other size categories; BLS's rates for small firms were lower than those for all but the very largest (250 or more employees) contractors. DIA's total workers' compensation (WC) payment rate of $7.06 per $100 payroll was only 11% higher than Colorado-specific expected loss rates reported by the National Council on Compensation Insurance. DISCUSSION: Complete reporting, facilitated by the existence of a single WC plan, an on-sites medical clinic, and designated medical providers, yielded injury rates significantly higher than previously reported. The relatively small difference between DIA payment rates significantly higher than previously that the discrepancy between DIA's injury rates and national estimates is due to underreporting of non-LWT injuries of the BLS. The burden of on-site work-related construction injury may be higher and more costly than has been evident from national data.

Accidents, Occupational↗

PubMed1998

Risk factors for injury among construction workers at Denver International Airport.

BACKGROUND: The Denver International Airport construction project provided a rare opportunity to identify risk factors for injury on a large construction project for which 769 contractors were hired to complete 2,843 construction contracts. Workers' compensation claims and payroll data for individual contracts were recorded in an administrative database developed by the project's Owner-Controlled Insurance Program. METHODS: From claims andy payroll data linked with employee demographic information, we calculated injury rates per 200,000 person-hours by contract and over contract characteristics of interest. We used Poisson regression models to examine contract-specific risk factors in relation to total injuries, lost-work-time (LWT), and non-LWT injuries. We included contract-specific expected loss rates (ELRs) in the model to control for prevailing risk of work and used logistic regression methods to determine the association between LWT and non-LWT injuries on contracts. RESULTS: Injury rates were highest during the first year of construction, at the beginning of contracts, and among older workers. Risk for total and non-LWT injuries was elevated for building construction contracts, contract for special trades companies (SIC 17), contracts with payrolls over $1 million, and those with overtime payrolls greater than 20%. Risk for LWT injuries only was increased for site development contracts and contract starting in the first year of construction. Contracts experiencing one or more minor injuries were four times as likely to have at least one major injury (OR = 4.0, 95% CI (2.9, 5.5)). CONCLUSIONS: Enhancement of DIA's safety infrastructure during the second year of construction appears to have been effective in reducing serious (LWT) injures. The absence of correlation between injury rates among contracts belonging to the same company suggest that targeting of safety resources at the level of the contract may be an effective approach to injury prevention. Interventions focused on high-risk contracts, including those with considerable overtime work, contracts held by special trades contractors (SIC 17), and contracts belonging to small and mid-sized companies, and on high-risk workers, such as those new to a construction site or new to a contract may reduce injury burden on large construction sites. The join occurrence of minor and major injuries on a contract level suggests that surveillance of minor injuries may be useful in identifying opportunities for prevention of major injures.

Accidents, Occupational↗

PubMed1998

"Lifeguard lung": endemic granulomatous pneumonitis in an indoor swimming pool.

OBJECTIVES: Two sequential outbreaks of respiratory disease among lifeguards at an indoor swimming pool with water spray features were investigated. METHODS: Questionnaires were administered to recreation center employees following each outbreak. Respondents reporting 2 or more pool-related symptoms were offered clinical evaluation, including bronchoscopy with bronchoalveolar lavage and transbronchial biopsy. Pool air and water were sampled for fungi, bacteria, amoebae, endotoxin, and respirable particulates. RESULTS: Thirty-three lifeguards had noncaseating granulomas on biopsy and/or bronchoalveolar lavage lymphocytosis. Attack rates for the outbreaks were 27% and 65%. Case patients had higher cumulative hours of work and tended to work more hours per week. Analyses indicated increased levels of endotoxin in pool air and water (relative to control pools) and gram-negative bacterial colonization of water sprays. Use of water spray features generated a 5.2-fold increase in the number of respirable particles and up to an 8-fold increase in air endotoxin levels. CONCLUSIONS: Lifeguards in this indoor swimming pool developed granulomatous lung disease associated with endotoxin-containing respirable bioaerosols from water spray features, which ventilation system improvements did not prevent.

Adolescent↗

PubMed1997

Serum neopterin in chronic beryllium disease.

We evaluated serum neopterin as a biomarker of chronic beryllium disease (CBD), for use in conjunction with the beryllium lymphocyte proliferation test (BeLPT) in workplace screening. Serum neopterin levels were determined by radioimmunoassay, and we compared levels in three groups: CBD (n = 86), beryllium sensitized (BeS) (n = 22), and normal (Nor) (n = 20). Those in the diseased group underwent pulmonary function tests, bronchoalveolar lavage (BAL), and maximal exercise testing. We correlated neopterin levels with results of these clinical parameters of disease severity. To evaluate the optimum sensitivity, specificity, and neopterin cut-off value, receiver operator characteristic (ROC) curves were generated. The median serum neopterin level in CBD was significantly higher than in BeS or in Nor [median 1.45, 25th, 75th percentiles (1.00, 2.7) ng/ml, 0.82 (0.67, 1.16) ng/ml, and 0.92 (0.86, 1.16) ng/ml, respectively] (P < 0.05). In CBD, we observed statistically significant associations between neopterin and measures of gas exchange and BAL cellularity. Using a neopterin value of 1.27 ng/ml, test specificity is 88%. In those workers with an abnormal BeLPT, serum neopterin has high positive predictive value (92%), and can identify disease, helping to distinguish it from BeS without the risks of biopsy.

Adult↗

PubMed1997

Interaction of genetic and exposure factors in the prevalence of berylliosis.

Prevalence of berylliosis, a lung disorder driven by the activation of beryllium-specific T cells, is associated with a major histocompatibility complex (MHC) class II marker (HLA-DPB1Glu69) and with the type of industrial exposure. We evaluated the interaction between marker and exposure in a beryllium-exposed population in which the prevalence of berylliosis was associated with machining beryllium. The presence of the marker was associated with higher prevalence (HLA-DPB1Glu69-positive machinists 25%; HLA-DPB1Glu69-negative machinists 3.2%, P = 0.05) and predicted berylliosis independent of machining history (odds ratios 11.8 and 10.1). The study shows that in berylliosis the carrier status of a genetic susceptibility factor adds to the effect of process-related risk factors.

Adult↗

PubMed1997

Metalworking fluid-associated hypersensitivity pneumonitis: a workshop summary.

A workshop discussing eight clusters of hypersensitivity pneumonitis in the automotive industry among metalworking fluid-exposed workers concluded that a risk exists for this granulomatous lung disease where water-based fluids are used and unusual microbial contaminants predominate. Strong candidates for microbial etiology are nontuberculous mycobacteria and fungi. Cases of hypersensitivity pneumonitis occur among cases with other work-related respiratory symptoms and chest diseases. Reversibility of disease has occurred in many cases with exposure cessation, allowing return to work to jobs without metalworking fluid exposures or, in some situations, to jobs without the same metalworking fluid exposures. Cases have been recognized with metalworking fluid exposures generally less than 0.5 mg/m3. The workshop participants identified knowledge gaps regarding risk factors, exposure-response relationships, intervention efficacy, and natural history, as well as surveillance needs to define the extent of the problem in this industry. In the absence of answers to these questions, guidance for prevention is necessarily limited.

Alveolitis, Extrinsic Allergic↗

PubMed1997

Risks of beryllium disease related to work processes at a metal, alloy, and oxide production plant.

OBJECTIVES: To describe relative hazards in sectors of the beryllium industry, risk factors of beryllium disease and sensitisation related to work process were sought in a beryllium manufacturing plant producing pure metal, oxide, alloys, and ceramics. METHODS: All 646 active employees were interviewed; beryllium sensitisation was ascertained with the beryllium lymphocyte proliferation blood test on 627 employees; clinical evaluation and bronchoscopy were offered to people with abnormal test results; and industrial hygiene measurements related to work processes taken in 1984-93 were reviewed. RESULTS: 59 employees (9.4%) had abnormal blood tests, 47 of whom underwent bronchoscopy. 24 new cases of beryllium disease were identified, resulting in a beryllium disease prevalence of 4.6%, including five known cases (29/632). Employees who had worked in ceramics had the highest prevalence of beryllium disease (9.0%). Employees in the pebble plant (producing beryllium metal) who had been employed after 1983 also had increased risk, with a prevalence of beryllium disease of 6.4%, compared with 1.3% of other workers hired in the same period, and a prevalence of abnormal blood tests of 19.2%. Logistic regression modelling confirmed these two risk factors for beryllium disease related to work processes and the dependence on time of the risk at the pebble plant. The pebble plant was not associated with the highest gravimetric industrial hygiene measurements available since 1984. CONCLUSION: Further characterisation of exposures in beryllium metal production may be important to understanding how beryllium exposures confer high contemporary risk of beryllium disease.

Adult↗

PubMed1996

Machining risk of beryllium disease and sensitization with median exposures below 2 micrograms/m3.

We examined the prevalence of beryllium sensitization in relation to work process and beryllium exposure measurements in a beryllia ceramics plant that had operated since 1980. We interviewed 136 employees (97.8% of the workforce), ascertained beryllium sensitization with the beryllium lymphocyte proliferation blood test, and reviewed historical industrial hygiene measurements. Of eight beryllium-sensitized employees (5.9%), six (4.4% of participating employees) had granulomatous disease on transbronchial lung biopsy. Machinists had a sensitization rate of 14.3% compared to a rate of 1.2% among other employees. Machining had significantly higher general area and breathing zone measurements than did other processes in the time period in which most beryllium-sensitized cases had started machining work. Daily weighted average (DWA) estimates of exposure for matching processes also exceeded estimates for other work processes in that time period, with a median DWA of 0.9 microgram/m3. Machining process DWAs accounted for the majority of DWAs exceeding the 2.0 micrograms/m3 OSHA standard, with 8.1% of machining DWAs above the standard. We conclude that lowering machining process-related exposures may be important to lowering risk of beryllium disease.

Air Pollutants, Occupational↗

PubMed1996

Risk of silicosis in a Colorado mining community.

We investigated exposure-response relations for silicosis among 134 men over age 40 who had been identified in a previous community-based random sample study in a mining town. Thirty-two percent of the 100 dust-exposed subjects had radiologic profusions of small opacities of I/O or greater at a mean time since first silica exposure of 36.1 years. Of miners with cumulative silica exposures of 2 mg/m3-years or less, 20% had silicosis; of miners accumulating > 2 mg/m3 years, 63% had silicosis. Average silica exposure was also strongly associated with silicosis prevalence rates, with 13% silicotics among those with average exposure of 0.025-0.05 mg/m3, 34% among those with exposures of > 0.05-0.1 mg/m3, and 75% among those with average exposures > 0.1 mg/m3. Logistic regression models demonstrated that time since last silica exposure and either cumulative silica exposure or a combination of average silica exposure and duration of exposure predicted silicosis risk. Exposure-response relations were substantially higher using measured silica exposures than using estimated silica exposures based on measured dust exposures assuming a constant silica proportion of dust, consistent with less exposure misclassification. The risk of silicosis found in this study is higher than has been found in workforce studies having no follow-up of those leaving the mining industry and in studies without job title-specific silica measurements, but comparable to several recent studies of dust exposure-response relationships which suggest that a permissible exposure limit of 0.1 mg/m3 for silica does not protect against radiologic silicosis.

Adult↗