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Biomedical subjects

T M Spear

Publications and source records attributed to T M Spear.

7 recordsLinked to original sources
PubMed2000

An effective protection factor study of respirators used by primary lead smelter workers.

An industrial hygiene study was conducted at a primary lead smelter to determine the effective protection factors for negative pressure and powered air purifying half-mask respirators. The study involved 99 paired personal samples taken in six different work areas, in which randomly chosen subjects from the workforce wore dual sampling pumps connected to closed-face 37-mm cassettes. The cassettes were attached either to the workers' lapels for exposure measurements outside the respirator or to a ported respirator for exposure measurements inside the respirator. Samples were collected throughout the work shift and analyzed for lead according to National Institute of Occupational Safety and Health (NIOSH) Method 7082. Using particle size distribution data obtained for the same workplaces, the within-mask samples were corrected for sampling bias. The negative pressure half-mask respirators showed a mean effective protection factor of 6.5 and a mean corrected effective protection factor of 4.56, with a 5th percentile less than 0.5. Approximately 80 percent and 90 percent of the effective protection factors and the corrected effective protection factors, respectively, were equal to or less than the assigned protection factor of 10. For the powered air purifying half-mask respirators, the means for effective protection factor and corrected effective protection factor were 18.20 and 11.92, respectively, with a 5th percentile of 1.0 or less. Approximately 90 percent and 95 percent of the effective protection factors and the corrected effective protection factors, respectively, were equal to or less than the assigned protection factor of 50. The uncorrected and corrected within-mask lead concentrations for both types of respirators exceeded the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for lead by 19 percent to 58 percent. These results indicate that the straight application of assigned protection factors to actual workplace situations may not always be appropriate.

Adult↗
PubMed1999

The effects of strapped spectacles on the fit factors of three manufactured brands of full facepiece negative pressure respirators.

A study was conducted to determine the effects of strapped spectacles on the fit factors obtained during quantitative fit testing on three different brands of full facepiece negative pressure respirators. The three brands of respirators were evaluated with and without strapped spectacles worn by the test subjects. A total of 180 quantitative fit testing trials were conducted on ten male test subjects. For each test subject, three quantitative fit testing trials were performed with each brand of respirator with and without the spectacles. The average of the fit testing trials for each subject with each respirator was used for statistical analysis. The results demonstrated that the fit factor values were significantly lower during use of the spectacles (p < 0.05). The estimated percentage of test subjects who failed the American National Standards Institute pass/fail criteria for quantitative fit testing (1000) increased by 15-36% when spectacles were worn.

Adolescent↗
PubMed1998

Assessment of particle size distributions of health-relevant aerosol exposures of primary lead smelter workers.

Experiments were conducted at a primary lead smelter to investigate the particle size distributions of lead-containing aerosol to which workers were exposed, using personal inhalable dust spectrometers (PIDS) in specific smelter process areas. A total of 46 PIDS samples were evaluated, taken from the ore storage/mill, sinter plant, blast furnace and dross furnace process areas. Continuous particle size distributions were derived from the raw PIDS data employing a recently-developed optimisation routine, enabling determination of the percentages of inhalable, thoracic and respirable aerosol (in terms of lead content) as fractions of total lead aerosol. In addition, the mass ratios thoracic/inhalable and respirable/inhalable were also determined. Although the parameters of the measured particle size distributions ranged widely, some clear trends emerged. Firstly, the aerosols were coarser than had been expected based on measurements of previously reported workplace particle size distributions. This is thought to be due to the fact that the PIDS collects larger particles more efficiently than other instruments which have been used for such measurements. Secondly, there were significant differences in particle size distribution between process areas, in particular that the aerosol in the blast furnace area was generally finer than in the sinter plant. Such results may be used to support the results of workplace studies (reported elsewhere) into the differences between exposures to inhalable and 'total' aerosol as measured using different sampling instruments, especially when they are used together with knowledge of the physical processes governing the performances of such instruments.

Analysis of Variance↗
PubMed1998

Chemical speciation of lead dust associated with primary lead smelting.

The research presented in this article assessed geochemical factors relating to dust produced during primary lead smelting. Bulk dust samples and size-selective airborne dust samples were collected from four areas of a primary lead smelter and analyzed by X-ray diffraction and sequential chemical extraction. X-ray diffraction showed that the smelter dusts were composed primarily of sulfides, oxides, sulfates, and silicates of metal ores, with galena being the primary dust component. Sequential extraction revealed the solubility of lead compounds at less than 7% in the exchangeable and mildly acidic steps for the bulk dusts collected from four smelter areas. The later steps of the extraction procedure were more effective in dissolving the lead compounds associated with the bulk dust samples, with 43%, 26%, and 8% of the total lead, in the ore storage, sinter, and blast/dross smelter areas, respectively, being extracted in the residual step. Sequential extraction of coarse airborne dust samples from the ore storage and sinter plant showed that 1.2% and 4.1% of the total lead, respectively, was exchangeable. The finer particle size fractions from these areas of the smelter showed higher percentages of exchangeable lead. Of the course airborne dust from the blast/dross furnace processes, 65% of the total lead was exchangeable. However, the largest percentage of lead from these areas was associated with the finer particle-size fractions. If lead bioavailability is related to its solubility as determined through sequential extraction, the health hazards associated with lead exposure may be appreciably enhanced in the blast and dross furnace processes.

Air Pollutants, Occupational↗
PubMed1997

Comparison of methods for personal sampling of inhalable and total lead and cadmium-containing aerosols in a primary lead smelter.

It has been proposed that future occupational aerosol exposure standards be based on particle size-selective sampling criteria that more accurately reflect worker exposure. In relation to methods currently used for determining individual workers' lead exposures, the widely used 37-mm, closed-face, plastic sampling cassette is known from laboratory wind tunnel studies to undersample significantly compared with estimations of aerosol actually inhaled, especially for large particles. The present study investigated the degree to which this is borne out in field sampling by using side-by-side sampling in selected work sites in a primary lead smelter. Exposures to "total" airborne lead and cadmium as measured using the 37-mm sampler (E37) were compared with exposure measurements using the institute of Occupational Medicine (IOM) personal inhalable aerosol sampler (EIOM). There were 166 good sample pairs for lead and 55 for cadmium. The ratio (reflecting the fractional undersampling of the 37-mm sampler, as represented by the ratio EIOM/E37) was consistently greater than unity, by factors obtained by regression analysis ranging (for different parts of the plant) from 1.39 to 2.14 for lead and 1.29 to 2.12 for cadmium. The factor tended to be greater for parts of the plant characterized by coarser aerosol, consistent with the physical sampling characteristics of the two instruments. This research is important (1) in assessing the impact of implementation of new standards for lead- and cadmium-containing aerosols in the primary lead production industry, and (2) in the development of new occupational exposure limits based on the inhalable aerosol fraction.

Aerosols↗
PubMed1996

Investigation into the impact of introducing workplace aerosol standards based on the inhalable fraction.

Since the late 1970s, there has been considerable discussion about describing human aerosol exposure in terms of a scientific criterion based on the efficiency with which particles are inhaled through the nose and/or mouth during breathing. As international agreement on the quantitative form of this criterion has emerged, progress is quickening towards workplace and environment aerosol standards in which the current 'total aerosol' approach will be replaced by one based on 'inhalability'. Wind tunnel investigations of a range of personal samplers currently used in workplaces for sampling 'total' aerosol have shown that many of these are not adequate for collecting the inhalable fraction. Such experimental evidence is supported by considerations of the physical sampling characteristics of the various samplers. Studies have been conducted to investigate workers' exposures to 'total' and inhalable aerosol in the workplaces of several industries in several countries, using side-by-side sampling in which participating workers wear two samplers, one for 'total' aerosol and the other for inhalable aerosol. The results from the several hundred sample pairs taken so far show that the level of exposure based on inhalable aerosol consistently exceeds that for 'total' aerosol. The observed ratios between the inhalable and 'total' aerosol exposures range from 1.2 to > 3, tending to be greater for workplaces where the aerosol is expected to be coarser. Such results may be used to assess the impact on industry of new limit values based on inhalable aerosol. It is clear that measured levels of exposure will tend to rise, so that there will be generally increased proportions of exposure measurements where levels will come close to, or exceed, current exposure limits. Those proportions may be greater still if new, lower limit values for 'total' aerosol currently under consideration for some substances are implemented. This paper examines these issues by reference to examples of exposure data taken from a range of industries and proposes options for how such information might influence the setting of future occupational exposure limits.

Administration, Inhalation↗