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Dave K Verma

Publications and source records attributed to Dave K Verma.

14 recordsLinked to original sources
PubMed2006

An evaluation of analytical methods, air sampling techniques, and airborne occupational exposure of metalworking fluids.

This article summarizes an assessment of air sampling and analytical methods for both oil and water-based metalworking fluids (MWFs). Three hundred and seventy-four long-term area and personal airborne samples were collected at four plants using total (closed-face) aerosol samplers and thoracic samplers. A direct-reading device (DustTrak) was also used. The processes sampled include steel tube making, automotive component manufacturing, and small part manufacturing in a machine shop. The American Society for Testing and Materials (ASTM) Method PS42-97 of analysis was evaluated in the laboratory. This evaluation included sample recovery, determination of detection limits, and stability of samples during storage. Results of the laboratory validation showed (a) the sample recovery to be about 87%, (b) the detection limit to be 35 microg, and (c) sample stability during storage at room temperature to decline rapidly within a few days. To minimize sample loss, the samples should be stored in a freezer and analyzed within a week. The ASTM method should be the preferred method for assessing metalworking fluids (MWFs). The ratio of thoracic aerosol to total aerosol ranged from 0.6 to 0.7. A similar relationship was found between the thoracic extractable aerosol and total extractable aerosol. The DustTrak, with 10-microm sampling head, was useful in pinpointing the areas of potential exposure. MWF exposure at the four plants ranged from 0.04 to 3.84 mg/m3 with the geometric mean ranging between 0.22 to 0.59 mg/m3. Based on this data and the assumption of log normality, MWF exposures are expected to exceed the National Institute for Occupational Safety and Health recommended exposure limit of 0.5 mg/m3 as total mass and 0.4 mg/m3 as thoracic mass about 38% of the time. In addition to controlling airborne MWF exposure, full protection of workers would require the institution of programs for fluid management and dermal exposure prevention.

Aerosols↗
PubMed2005

Mortality among Ontario members of the International Union of Bricklayers and Allied Craftworkers.

BACKGROUND: Dust exposed workers may be at increased risk of pneumoconiosis, stomach cancer, lung cancer, and obstructive lung disease. Bricklayers may experience high exposures to silica and inorganic dusts. The aim of this study was to examine the mortality pattern of bricklayers to identify occupational associations with mortality. METHODS: A cohort of 10,953 workers was assembled from records of the International Union of Bricklayers and Allied Craftworkers (IUBAC). Mortality was ascertained by linkage to the Canadian Mortality Registry at Statistics Canada. Standardized Mortality Ratios (SMRs) were computed using Ontario general population mortality rates as the reference. RESULTS: Twenty or more years from first membership, SMRs for lung (158; 130-190) and stomach (235; 140-370) cancers were significantly elevated. There were four deaths from pneumoconiosis, but non-malignant respiratory mortality SMRs were not increased. CONCLUSIONS: Bricklayers and Allied Craftworkers are at risk from diseases associated with heavy exposure to inorganic dust: lung cancer, stomach cancer, and pneumoconiosis. Dust control as well as education and training of these workers to protect themselves against inhalation hazards is necessary.

Adult↗
PubMed2005

Occupational exposure limits: an approach and calculation aid for extended work schedule adjustments.

Past reviews of occupational exposure limit (OEL) adjustments have covered both decision logic and calculation methods to derive factors to assure protection of workers on extended (also known as unusual) work shifts. The approaches reviewed included several Haber's rule based methods, several variants of single compartment toxicokinetic (TK) models, and physiologically based pharmacokinetic modeling. These models calculate OEL adjustment factors based on the work shift and the uptake and elimination of the toxicant. A key parameter of the TK models is the biologic half-life of the toxicant, but reliable data for the half-life are not available for all substances of concern. A spreadsheet is presented that implements TK calculations, with one of the presented TK calculation alternatives not dependent on half-life data. This half-life data independent approach is suggested as a viable option for situations when the toxicant's half-life is unknown or uncertain.

Environmental Pollutants↗
PubMed2004

Ischemic heart disease mortality among heavy equipment operators.

BACKGROUND: Inhalation of fine particulate is hypothesized to increase risk of heart disease events. METHODS: Seven Ontario construction unions participated in a retrospective cohort mortality study. Proportional mortality ratios (PMRs) were computed and a mortality odds ratio (MOR) analysis was performed to compare the risk of ischemic heart disease (IHD) mortality among heavy equipment operators (HEO) to that of members of other unions. Deaths attributed to lung cancer, mesothelioma, and accidental causes were excluded from the comparison. RESULTS: Two hundred fifty nine of 1,009 deaths among the HEO were attributed to IHD. The PMR was 1.09 (0.96-1.2). None of the IHD PMRs among the other six unions exceeded 0.89. The MOR for IHD mortality, comparing the HEO to all other workers combined was 1.47 (1.17-1.84) for ages 25-64, was 1.20 (0.96-1.50) for ages 65 or more, and was 1.32 (1.13-1.55) for all ages combined. CONCLUSIONS: Increased risk of IHD mortality among HEO is consistent with the hypothesis that exposure to diesel fume has adverse effects upon the heart and circulatory system.

Adult↗
PubMed2004

Current man-made mineral fibers (MMMF) exposures among ontario construction workers.

Current occupational exposures to man-made mineral fibers (MMMF), including refractory ceramic fibers (RCF), were measured as part of an exposure assessment program for an epidemiological study pertaining to cancer and mortality patterns of Ontario construction workers. The assessments were carried out at commercial and residential sites. A total of 130 MMMF samples (104 personal and 26 area) was collected and included 21 RCF (16 personal and 5 area). The samples were analyzed by the World Health Organization method in which both respirable and nonrespirable airborne fibers are counted. The results show that Ontario construction workers' full-shift exposure to MMMF (excluding RCF) is generally lower than the American Conference of Governmental Industrial Hygienists' (ACGIH) recommended threshold limit value-time-weighted average (TLV-TWA) of 1 fibers/cc and thus should not present any significant hazard. However, approximately 40% of the occupational exposures to RCF are higher than ACGIH's TLV-TWA of 0.2 fibers/cc and present a significant potential hazard. Workers generally wore adequate approved respiratory protection, especially while performing particularly dusty tasks such as blowing, spraying, and cutting, so the actual exposure received by workers was lower than the reported values. Adequate control measures such as ventilation and respiratory protection should always be used when work involves RCF.

Air Pollutants, Occupational↗
PubMed2004

A simultaneous job- and task-based exposure evaluation of petroleum tanker drivers to benzene and total hydrocarbons.

A simultaneous job- and task-based exposure study was conducted for tanker drivers delivering petroleum products from several bulk terminals and an agency to retail outlets. Full-shift (job-based) samples and job component tasks samples were collected simultaneously. The tasks sampled included loading, unloading, and travel. Three hundred sixty-six personal charcoal tube samples were collected. Full-shift visual observations of work practices and real-time monitoring using a data logging hydrocarbon analyzer were also conducted. Multiple measurements per worker were made, which permitted an assessment of sampling variability within and between workers. The highest exposures for drivers occurred during unloading at the agency. The mean benzene exposure for agency drivers was 0.88 ppm for full-shift time-weighted average, 2.86 ppm for unloading, and 0.54 ppm for loading. For bulk terminal drivers, the mean benzene level without vapor control was 0.12 ppm for time weighted average, 0.24 ppm for unloading, and 0.33 ppm for loading. The time-weighted average exposure of the agency and bulk terminal drivers based on the data collected and the lognormal model can be expected to exceed threshold limit value-time weighted average of 0.5 ppm for benzene about 70 and 2% of the time, respectively. Agency drivers' unloading and loading tasks accounted for approximately 30% and 7% of the total time, and 95% and 4% of total exposure, respectively. For the bulk terminal drivers, mean unloading and loading tasks constituted 24% and 12% of the total time, and 68% and 19% of the total exposure, respectively. Travel activity accounted for an average of 63% of the total time for agency and 64% for bulk terminal drivers, but only contributed < 1 and 13% of the total exposure, respectively. The actual job-based time-weighted average concentration and the calculated time-weighted average derived from the time-weighted summation of the components tasks are in very good agreement. Within-worker variability was generally higher than between-worker variability. Exposure control strategies are required primarily for unloading at the agencies. Vapor control technology at the terminal effectively reduces exposure (by almost 50%) and fugitive emissions.

Automobile Driving↗
PubMed2003

Relation between income, air pollution and mortality: a cohort study.

BACKGROUND: Community levels of air pollution have been associated with variability in mortality rates, but previous studies have inferred exposure to pollutants on a citywide basis. We investigated mortality in relation to neighbourhood levels of income and air pollution in an urban area. METHODS: We identified 5228 people in the Hamilton-Burlington area of southern Ontario who had been referred for pulmonary function testing between 1985 and 1999. Nonaccidental deaths that occurred in this group between 1992 and 1999 were ascertained from the Ontario Mortality Registry. Mean household income was estimated by linking the subjects' postal codes with the 1996 census. Mean neighbourhood levels of total suspended particulates and sulfur dioxide were estimated by interpolation from data from a network of sampling stations. We used proportional hazards regression models to compute mortality risk in relation to income and pollutant levels, while adjusting for pulmonary function, body mass index and diagnoses of chronic disease. Household incomes and pollutant levels were each divided into 2 risk categories (low and high) at the median. RESULTS: Mean pollutant levels tended to be higher in lower-income neighbourhoods. Both income and pollutant levels were associated with mortality differences. Compared with people in the most favourable category (higher incomes and lower particulate levels), those with all other income-particulate combinations had a higher risk of death from nonaccidental causes (lower incomes and higher particulate levels: relative risk [RR] 2.62, 95% confidence interval [CI] 1.67-4.13; lower incomes and lower particulate levels: RR 1.82, 95% CI 1.30-2.55; higher incomes and higher particulate levels: RR 1.33, 95% CI 1.12-1.57). Similar results were observed for sulfur dioxide. The relative risk was lower at older ages. INTERPRETATION: Mortality rates varied by neighbourhood of residence in this cohort of people whose lung function was tested. Two of the broader determinants of health--income and air pollution levels--were important correlates of mortality in this population.

Aged↗
PubMed2003

Diesel exhaust exposure in the Canadian railroad work environment.

An investigation of occupational exposure to diesel exhaust, in terms of elemental carbon, was conducted as part of a feasibility study in the Canadian railroad industry. Both personal and area samples were collected from three major operating divisions of the railways: mechanical service, transportation, and engineering. A total of 255 elemental carbon samples have been described. The results show that all but six elemental carbon concentrations, expressed as size-selective respirable air samples taken using a 10 mm nylon cyclone, are well below the 2001 proposed American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV) of 20 microg/m3. The concentration of diesel exhaust, expressed as elemental carbon, in the railroad industry is much lower than that in some other major industries such as mining and forklift truck operations. If the TLV is to be applicable to a broad range of workplace settings such as railroad, construction, and mining, the use of a TLV that is based on an elemental carbon measurement of size selective respirable samples, as recommended in the 2001 ACGIH proposal, would appear to be the most valid strategy for control of exposure to diesel exhaust.

Canada↗
PubMed2003

Coal tar pitch volatiles and polycyclic aromatic hydrocarbons exposures in expansion joint-making operations on a construction site: a case study.

This case study describes occupational exposures to coal tar pitch volatiles (CTPV) as benzene soluble fraction (BSF), polycyclic aromatic hydrocarbons (PAHs) and total particulates at a unique operation involving the use of coal tar in the making of expansion joints in construction of a multi-level airport parking garage. A task-based exposure assessment approach was used. A set of 32 samples was collected and analyzed for total particulate and CTPV-BSF. Twenty samples of this set were analyzed for PAHs. Current American Conference of Governmental Industrial Hygienists (ACGIH(R)) respective threshold limit value-time weighted average (TLV-TWA) for insoluble particulates not otherwise specified (PNOS) is 10 mg/m(3) as inhalable dust, which roughly corresponds to 4 mg/m(3) total particulate; for CTPV as BSF the TLV is 0.2 mg/m(3), and for specific PAHs such as benzo(a)-pyrene (B[a]P), ACGIH suggests keeping exposure as low as practicable. The recommended Swedish exposure limit for B(a)P is 2 microg/m(3). The highest exposure levels measured were 12.8 mg/m(3) for total particulate, 1.9 mg/m(3) for coal tar pitch volatiles as BSF, and 12.8 microg/m(3) for B(a)P. Several of the CTPV-BSF results were over the TLV of 0.2 mg/m(3). The data set is limited; therefore, caution should be used in its interpretation.

Coal Tar↗
PubMed2003

Current chemical exposures among Ontario construction workers.

Current occupational exposures to chemical agents were assessed as part of an epidemiological study pertaining to the cancer and mortality patterns of Ontario construction workers. The task-based exposure assessment involved members from nine construction trade unions. Air samples were taken using personal sampling pumps and collection media. A DustTrak direct-reading particulate monitor was also employed. Exposure assessments included measurements of airborne respirable, inhalable, total, and silica dust; solvents; metals; asbestos; diesel exhaust and man-made mineral fibers (MMMF). In total, 396 single- or multi-component (filter/tube), 798 direct-reading, and 71 bulk samples were collected. The results showed that Ontario construction workers are exposed to potentially hazardous levels of chemical agents. The findings are similar to those reported by other researchers, except for silica exposure. In our study, silica exposure is much lower than reported elsewhere. The difficulty associated with assessing construction workers' exposures is highlighted.

Air Pollutants, Occupational↗
PubMed2002

A method for determining crystalline silica in bulk samples by Fourier transform infrared spectrophotometry.

A method for determining crystalline silica (alpha-quartz) in bulk samples has been developed. This procedure requires the bulk sample to be homogenized and sieved down to particle sizes <10 micro m in diameter. The obtained fraction is analysed by Fourier transform infrared spectrophotometry. Method validation was carried out using 55 real-world bulk samples, containing between 1 and 75% (w/w) alpha-quartz. The method is capable of quantifying alpha-quartz down to 1% (w/w) in routine analysis. However, the method is unlikely to allow routine quantification at 0.1% (w/w) as currently mandated by regulations.

Particle Size↗
PubMedDate not supplied

Benzene in gasoline and crude oil: occupational and environmental implications.

A review of studies, published in peer-reviewed journals and articles available as technical reports of various organizations, regarding benzene in gasoline and crude oil was performed. The summarized data will be useful for retrospective exposure assessments in epidemiological studies. It shows that in the past, benzene in gasoline has been quite high, but now, there is a distinct trend in North America and Europe to reduce benzene in gasoline to a level of about 1%. The reduction of benzene in gasoline results not only in the lowering of occupational exposure for workers, but it also has far greater influence in decreasing the environmental benzene exposure for the general public.

Benzene↗