• Abstract and Figures
• Public Full-text

Occupational and Environmental Medicine 1995;52: 185-19 1 185 Maintenance of stellite and tungsten carbide saw tips: respiratory health and exposure-response Occup Environ Med: first published as 10.1136/oem.52.3.185 on 1 March 1995. Downloaded from evaluations Susan M Kennedy, Moira Chan-Yeung, Steve Marion, John Lea, Kay Teschke Abstract Hard-metal lung disease occurs in workers Objective-To study exposure to cobalt exposed to cobalt in association with tungsten and chromium in saw maintenance carbide (hard-metal)1 2 and in other metal rooms and test respiratory health among working processes that involve exposure to saw filers at lumber mills. Hard-metal cobalt, such as diamond polishing.3 The dis- lung disease is associated with cobalt in ease is an interstitial pneumonitis charac- the manufacture of tungsten carbide terised by radiographic infiltrates, reduced tools; recently it has also been reported diffusing capacity and lung volume,4 and a among tool maintenance workers. histology of fibrosing alveolitis with unusual Lumber mills often use saws tipped with multinucleated giant cells.' Prevalence of tungsten carbide or with a newer alloy, about 1% is generally reported although some stellite (containing more cobalt, as well studies suggest higher rates.46 Fatal cases have as chromium). been reported,7 and the predictors of fatality Methods-A cross sectional study of 118 are not clear. Also, cobalt is known to cause saw filers at eight lumber mills was car- occupational asthma' 8 and asthma like symp- ried out that included a standardized toms.2 questionnaire, spirometry, personal air Most studies of hard-metal lung disease in sampling, and examination of tasks every association with tungsten carbide have been 10 minutes (by observation). Comparison limited to the tool manufacturing industry. data were from a study of bus mechanics We are aware of only one recent report of four tested with similar methods. cases of hard-metal lung disease among work- Results and Conclusion-Cobalt expo- ers who use or maintain these tools.' We sure was associated with tungsten carbide report here results from a study of saw filers, grinding but not with stellite grinding. who maintain saws in lumber mills. Chromium exposure was associated Saw blades in lumber mills are generally mainly with stellite welding. Saw filers made of hardened steel, but the cutting tips had a twofold increase in phlegm and are often composed of specialty compounds wheeze (P < 0.01) and a threefold welded or soldered to the saw body. In the increase in cough, phlegm, and wheeze past two decades, soldered tungsten carbide http://oem.bmj.com/ related to work (P < 0.001), but no tips have become widely used. Tungsten car- increase in breathlessness. Stellite weld- bide is a sintered metal composite with cobalt ing was associated with a significant (from 3-30%) as the binder for the tungsten increase in nasal symptoms and cough carbide and other trace metals.'0 More related to work and a small decrease in recently, saw tips have been welded with a airflow volume in one stellite (Deloro Stellite, Belleville, Occupational and (forced expiratory superalloy, Environmental Lung second/forced vital capacity (FEV1/ Ontario). In this alloy, cobalt (50-60%), on October 1, 2021 by guest. Protected copyright. Diseases Research FVC%), P < 0.05). Saw filers wet grind- chromium (30-35%), and other trace metals Unit, Respiratory ing with tungsten carbide had significant are heated above their melting points to create Division, Department of Medicine reductions in forced expiratory lung vol- prealloyed powder, which is mixed with an S M Kennedy umes (FEV1 and FVC, P < 0.05) and were organic binder before final sintering.10 Some M Chan-Yeung significantly more likely to have FEV1 and saw filers also sharpen chipper knives that are Department ofHealth FVC values in the abnormal range. predominantly iron (85-90%), but also con- Care and wet and tain some chromium " In lumber Epidemiology Cobalt exposure (in grinding) (8-9%). S M Kennedy duration of work that involved tungsten mills in British Columbia, Canada, neither S Marion carbide grinding were both associated tungsten carbide nor stellite tips are univer- JLea with significant reductions in FEV1 and sally used, although many mills use one or the K Teschke FVC. Average cobalt exposures in this other, and some use both. Occupational Hygiene Programme, study were about 5 pglm3, well below the Depending on the saw type and the University of British currently accepted permissible concen- process, saws in the lumber industry are used Columbia, Vancouver, tration, which suggests that the current for only a few work shifts and then require Canada be too Saw filers a of S M Kennedy workplace limit for cobalt may sharpening. perform variety K Teschke high. tasks including removing saws from produc- Correspondence to: tion lines, transferring them to the filing Dr Susan M Kennedy, (Occup Environ Med 1995;52:185-191) room for maintenance, and reinstalling saws Occupational Hygiene Programme, University of into production. The maintenance work British Columbia, 2206 East involves setting up and operating machinery Mall, Vancouver, British Columia, Canada V6T 1Z3. Keywords: hard-metal lung disease; cobalt; tungsten to solder or weld new tips to the saw body, Accepted 24 November 1994 carbide grinding and sharpening tips, and occasionally 186 Kennedy, Chan-Yeung, Marion, Lea, Teschke soldering and welding tips manually. which metal concentrations were quantified Grinding and sharpening often requires lubri- by inductively coupled argon plasma atomic cation with soluble machining fluids. Also, emission spectrophotometry. A total of 278 Occup Environ Med: first published as 10.1136/oem.52.3.185 on 1 March 1995. Downloaded from tasks for quality control and safety assurance air samples were obtained from 112 workers. of the saw bodies are performed. Although Every worker in the saw filing room was workers with different levels of training and involved in the exposure monitoring, regard- seniority perform some of these tasks prefer- less of his job tasks or suspected exposure entially to others, no saw filers are engaged in potential. Coincident with air sampling, every grinding for an entire shift. 10 minutes, an industrial hygiene technician This report describes the results of a survey recorded each worker's specific activity, the of respiratory health among saw filers in eight name of the nearest operating machine, the volunteer lumber mills in coastal British distance between the breathing zone and the Columbia. Our principal objective was to generation point of the contaminant, and determine whether or not these workers were whether or not the worker was smoking. As exposed to excessive concentrations of cobalt well as monitoring airborne exposure, 73 bulk or chromium, and if so, to evaluate the deter- samples of used coolant were obtained from minants of exposure; the respiratory health lubricated grinding machines and analysed for assessment was conducted as a pilot survey metals. only. It should be noted that the study design More than half of the monitored values for (volunteer mills) does not ensure a represen- cobalt and chromium in air were below the tative picture of the entire industry, and that detection limit-that is, severe left censor- the sample size was not expected to be suffi- ing-and the remaining data did not meet cient to detect clinically relevant cases of tests of normality, even with log transforma- hard-metal lung disease. Results from the tion.'2 This presented a challenge for statisti- exposure evaluation are reported separately.'2 cal analysis of the determinants of exposure. Details and rationale for the technique of analysis of the exposure data are presented Methods elsewhere. 12 Briefly, linear regression analyses PARTICIPANTS were conducted with the cobalt or chromium Saw filers were identified from lists provided concentration (original scale) as the depen- by the management at each mill. Each eligible dent variable (with a value of half the detec- participant (all men) was contacted by letter tion limit entered for concentrations below and invited to participate. Participation was the detection limit). Seven activity and 10 entirely voluntary and each participant signed a location variables were considered as the "consent to participate" form before the tests, potential predictors. Both dichotomous (ever after having the aims and objectives of the during the day v never) and continuous study explained to him. The study protocol (number of times observed during the day) was approved by the University of British versions of these variables were considered; Columbia Committee on Ethics in Research however, the dichotomous versions were pre- Involving Human Subjects. ferred in almost all cases. Modelling was done with generalised estimating equations and http://oem.bmj.com/ EXTERNAL COMPARISON POPULATION robust estimation of variance (thus taking into As this was a pilot study, no external compari- account both non-conformance with the son population was included in the protocol. equal variance assumption of ordinary least For some analyses comparisons were made squares regression and the presence of with results obtained from bus mechanics repeated measures from the same worker). studied by us in December 1990 with the This approach has the advantage that each identical respiratory symptom questionnaire regression coefficient for a dichotomous vari- on October 1, 2021 by guest. Protected copyright. and pulmonary function testing procedures able represents the mean exposure for that and equipment. The technicians and inter- activity or location. viewers for both studies were all trained by the same study coordinator. This group was stud- EVALUATION OF RESPIRATORY HEALTH ied due to their concern about past use of An expanded version of the American asbestos products. Results indicated that Thoracic Society standard respiratory ques- there was little or no impairment of health tionnaire"3 was given by a trained interviewer. among the bus mechanics.

Load more

  7

Copy Link