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Biomedical subjects

D C Muir

Publications and source records attributed to D C Muir.

At least 73 records · Page 4Linked to original sources
PubMed1992

Polycyclic aromatic hydrocarbons (PAHs): a possible cause of lung cancer mortality among nickel/copper smelter and refinery workers.

A retrospective industrial hygiene investigation was undertaken to explain the cause of a statistically significant excess lung cancer mortality observed in a subset of a large cohort of nickel workers involved in mining, smelting, and refining of nickel and copper in Ontario. The focus of this paper is to demonstrate how an industrial hygiene follow-up assessment of an epidemiologic finding can help to identify a likely cause. Polycyclic aromatic hydrocarbons (PAHs) alone or in association with particulate and gaseous contaminants (e.g., SO2) were likely the causative agents of the excess lung cancer observed among the lead welders, cranemen, and arc furnace workers of the copper refinery.

Cohort Studies↗
PubMed1990

Polychlorinated dibenzo-p-dioxins and dibenzofurans in marine mammals in the Canadian North.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were determined in pooled samples of ringed seal (Phoca hispida) blubber, beluga (Delphinapterus leucas) blubber and polar bear (Ursus maritimus) liver and fat from several areas throughout the Canadian north and compared to mean PCB and HCB levels in the same samples. All seal samples, and all but one polar bear sample, had detectable 2,3,7,8-TCDD at concentrations ranging from 2 to 37 ng/kg, but TCDD was not found in beluga blubber (< 2 ng/kg). All seal samples and one of three beluga samples contained 2,3,7,8-TCDF at levels of 2 to 7 ng/kg, but TCDF was not found in any bear sample. TCDF must therefore be cleared rapidly by polar bears. No other PCDF congeners were found at detection limits of 4 to 8 ng/kg. OCDD concentrations in seal blubber and polar bear samples ranged from not detected (< 8 ng/kg) to 43 ng/kg. No apparent biomagnification of TCDD, OCDD or TCDF occurred from seal to bear fat, similar to previous findings for DDT, and unlike SigmaPCBs and HCB which biomagnified 6- to 17-fold. Highest concentrations of 2,3,7,8-TCDD and OCDD in seals and bears were found in the central Canadian Arctic Archipelago, and lowest were found in Hudson Bay, the reverse of PCB concentration distribution. The reason for higher levels of TCDD and OCDD in the Arctic than in the sub-Arctic is suggested to be trans-polar movement of aerosols with combustion-related origins in Eurasia. Levels of 2,3,7,8-TCDF were more evenly distributed throughout the North, and were positively correlated with PCB, but not with HCB or 2,3,7,8-TCDD levels in seals.

Journal Article↗
PubMed1990

Mortality of glass filament (textile) workers.

A historical prospective mortality study was conducted at a glass filament plant in Ontario, Canada. The cohort consisted of 1465 men and women who had worked for a total of at least one year between 1951 (when the operations began) and 1986. Ninety six deaths were found in the 96% of persons traced. Mortality was compared by the person-years method with that of the Ontario population. An estimate of cumulative dust exposure was made based on long term employees' recollections of past conditions. Overall mortality was below that expected (standardised mortality ratio (SMR) = 76) based on 82 deaths. There were 11 deaths due to lung cancer; slightly but not significantly more than expected (SMR = 136, p = 0.31). Analysis by both duration of employment and cumulative exposure showed this increase to be inconsistent with an occupational aetiology.

Adolescent↗
PubMed1989

Silica exposure and silicosis among Ontario hardrock miners: I. Methodology.

An epidemiological investigation was undertaken to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (crystalline silica--alpha quartz) dust. This first report describes the cohort, the method of classifying the radiographs, and the identification of a case of silicosis.

Cohort Studies↗
PubMed1989

Silica exposure and silicosis among Ontario hardrock miners: II. Exposure estimates.

An epidemiological investigation was carried out to determine the relationship between silicosis in hardrock miners in Ontario and cumulative exposure to silica (free crystalline silica--alpha quartz) dust. This second report describes a side-by-side air-sampling program used to derive a konimeter/gravimetric silica conversion curve. A total of 2,360 filter samples and 90,000 konimeter samples were taken over 2 years in two mines representing the ore types gold and uranium, both in existing conditions as well as in an experimental stope in which dry drilling was used to simulate the high dust conditions of the past. The method of calculating cumulative respirable silica exposure indices for each miner is reported.

Environmental Exposure↗
PubMed1989

A study of mortality in workers engaged in the mining, smelting, and refining of nickel. I: Methodology and mortality by major cause groups.

Following the publication of the NIOSH nickel criteria document in 1977, the Joint Occupational Health Committee of the International Nickel Company (INCO) commissioned a mortality study of the company's Ontario workforce. This paper describes the detailed methodology and primary mortality results of the ensuing study; subsequent papers will describe more detailed findings of cause-specific mortality. An historical prospective mortality study of approximately 54,000 INCO workers has been conducted. Men with six months or more of service were followed for mortality during a 35-year period by computerized record linkage to the Canadian National Mortality Data Base. From a company-provided list of men known to have died and through independent follow-up of a random sample of 1,000 subjects of unknown status, we estimate a mortality ascertainment rate of 95%. Cause-specific standardized mortality ratios calculated with respect to Ontario provincial mortality rates indicate an excess of accidental deaths in men working in the Sudbury area and an excess of cancer deaths at the company's Port Colborne nickel refinery. A strong healthy worker effect was found for both all-disease mortality ad cancer mortality. The lower than expected mortality persisted for about 15 years beyond initial hiring.

Adolescent↗
PubMed1989

A study of mortality in workers engaged in the mining, smelting, and refining of nickel. II: Mortality from cancer of the respiratory tract and kidney.

This paper describes observed and expected mortality from cancers of the lung, larynx, nose, and kidney in a cohort of 54,509 nickel workers followed for 35 years. For analysis purposes the cohort was subdivided into men with and without service in one of the three high nickel dust areas of the operation: the Sinter Plants at Copper Cliff and Coniston, and the Leaching, Calcining and Sintering (LC&S) department at Port Colborne. At Copper Cliff Sinter Plant workers experienced three times the expected number of lung cancer deaths; the SMR rose steeply with increasing duration of service peaking at 943 with 10 to 15 years. A similar overall excess risk of lung cancer was seen in the smaller Coniston Sinter Plant again with an indication of an exposure risk gradient. Men in the LC&S department at Port Colborne also experienced a dose related excess risk of lung cancer death that rose to an SMR of 806 with 20 to 25 years of service. Nasal cancer deaths were increased at both the Copper Cliff Sinter Plant (6 deaths) and the LC&S department at Port Colborne (19 deaths), representing SMRs of 3,704 and 7,755, respectively, for this rare cancer. Laryngeal cancer and kidney cancer, both previously associated with nickel, were not in excess in these high risk groups. A further exploration of death from these causes in the lower exposure remainder of the cohort revealed an epidemiologically modest elevation in lung cancer death in miners (probably not nickel related) and parts of the Copper Refinery. No evidence of laryngeal cancer excess was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Canada↗
PubMed1989

Use of noseclips in pulmonary function tests.

Spirometry was performed on 136 male industrial workers experienced in undergoing pulmonary function testing for the purpose of studying the effects of the use of noseclips on forced vital capacity (FVC) maneuvers. A cross-over design was employed with each subject serving as his own reference. Forced expiratory volume in 1 second (FEV1) and FVC measurements were recorded adhering closely to the guidelines set down by the American Thoracic Society. Assuming that a 30-ml difference in FVC and FEV1 is not important, we conclude that these measurements are not significantly affected by the use of noseclips. However, trial order was found to affect the outcome. The FVC and FEV1 values on the first trial were consistently lower than those on the second regardless of noseclip use. Many subjects experienced discomfort from noseclips and their use is not recommended for routine purposes.

Adult↗
PubMed1988

TLVs--what now?

Explore the source record for details and available documents.

Environmental Exposure↗
PubMed1988

Pneumoconiosis in iron ore surface mining in Labrador.

A cross-sectional survey of the work force at an iron ore surface mine and beneficiation plant in Labrador identified cases with a radiologic diagnosis compatible with simple pneumoconiosis by the International Labour Organization (ILO) classification (1980). Their distribution by ILO categories 1, 2, and 3, after excluding those with confounding diagnoses for pneumoconiosis, was 30, 10, and 2 cases, respectively. ILO category was related to age, duration of current employment, and cumulative respirable dust and quartz levels, as well as to decrement in ventilatory function.

Adult↗
PubMed1988

Aesthesiometric threshold changes over the course of a workshift in miners exposed to hand-arm vibration.

The objective of this study was to investigate whether aesthesiometric threshold changes occur over the course of a workshift in vibration exposed hard rock miners relative to workers unexposed to vibration during the shift. The subjects were 99 miners and 40 smelter workers; four subjects declined to participate and nine were excluded from the analysis because of apparent failure to comprehend the testing procedure. Two point discrimination and depth sense aesthesiometry were conducted at the beginning and at the end of the workshift in all digits of both hands excluding the thumbs. In addition to the use of a vibrating tool during the shift, age, digital temperature, signs of arm injury, presence of fingertip callus, and handedness were documented. In the analysis the difference between postshift and preshift readings was studied in relation to these variables, particularly exposure to the jackleg drill during the shift. With the exception of exposure of the jackleg drill, no associations were observed between these variables and change over the workshift in aesthesiometric results, on both unadjusted comparison of means and backward elimination regression analysis. A statistically significant association, however, was found between the use of a jackleg drill and change in two point discrimination and in depth sense aesthesiometric results over the course of the shift, for the right hand. Evidence of the occurrence of a learning effect, particularly for two point discrimination aesthesiometry, was observed. The occurrence of an effect in the right, but not the left, hand reflects dominant handedness and relatively greater vibration exposure in the right hand in our subjects. This study supports the incorporation of an exposure free interval before aesthesiometric testing of vibration exposed workers.

Fingers↗
PubMed1988

Laminar flow air cleaner bed attachment: a controlled trial.

Thirteen house dust mite-allergic young asthmatics were entered into a double-blind, crossover clinical trial to compare "in use" with "non-use" of a laminar flow air cleaner bed attachment. The study design encouraged maintenance of symptom control by adjustment of the dose of medications used. There was a significant reduction in the amount of medications required by the patients during the trial period that the air cleaner was in use. Histamine airway responsiveness was significantly decreased for a group of eight of the subjects tested at the end of a 3-month open trial.

Adolescent↗
PubMed1987

Herbicide levels in rivers draining two prairie agricultural watersheds (1984).

A monitoring survey was conducted during 1984 on the Ochre and Turtle Rivers, which flow into Dauphin Lake in western Manitoba, Canada, to determine levels of the herbicides MCPA, diclofop-methyl, dicamba, bromoxynil, 2,4-D, triallate and trifluralin which were widely used in each watershed. Triallate concentrations exceeded 4 ng/L in 50% and 10% of the 21 samples taken from each of the Turtle and Ochre River, respectively, during the period March to October 1984. Trifluralin concentrations exceeded 3 ng/L in 14% and 10% of the samples from the respective rivers. Maximum concentrations did not exceed 25 ng/L and were unrelated to changes in river flow. Bromoxynil and diclofop were detected in the Turtle River, at concentrations of 113 and 476 ng/L, respectively, following a major high water event in late June, but were undetectable (less than 2 and 12 ng/L, respectively) at other sampling times. Dicamba and 2,4-D were detectable throughout most of the sampling period in both rivers at low levels (less than 100 ng/L). High levels of dicamba and 2,4-D (5476 and 2568 ng/L respectively) were found in water from the Turtle River prior to the high water event event possibly caused by spraying of ditches or rights-of-way near the river. Discharges (grams/year) of all seven herbicides monitored in the study represented less than 0.1% of the amounts estimated to be used in each watershed. Unit loadings (mg/ha/year) of 2,4-D and dicamba were similar to those reported for Southern Ontario streams in the mid-1970's. The results indicate that herbicide contamination of Manitoba streams draining agricultural areas is generally low except when major runoff occurs during the application period in May and June.

Chromatography, Gas↗