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Biomedical subjects

D K Verma

Publications and source records attributed to D K Verma.

At least 19 recordsLinked to original sources
PubMed2005

Quantitative histological features and ultrastructure of opercula of human teeth showing normal and delayed eruption.

BACKGROUND: Failure of eruption of human permanent molars has been attributed to opercular lesions, although comparisons with specimens from normally erupting teeth are scarce. The aim of this study was to quantitatively analyse opercula associated with normal and delayed tooth eruption. METHOD: Twenty opercula covering permanent molars delayed in eruption were obtained from 13 patients aged 7.3-18.1 years. Six opercula from normally erupting molars of five 7.3-17.5-year-old subjects served as controls. Specimens were analysed light and electron microscopically and morphometrically. RESULTS: In addition to features recognized previously, prominent numbers of nerves, high endothelial-like venules and mast cells were observed. Ultrastructurally, large multinucleated cells did not reveal cell boundaries running between the nuclei, and mast cells seemed belonging to the MC(TC)-type. None of the features differed significantly between opercula from cases of delayed and normal tooth eruption. CONCLUSIONS: Disturbances of tooth eruption that are attributed to opercular lesions may represent retentions resulting from the failure of the eruption mechanism, rather than impactions because of a physical barrier.

Adolescent↗
PubMed2004

A cohort study of mortality among Ontario pipe trades workers.

AIMS: To study mortality in a cohort of members of the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry of the United States and Canada and to compare results with two previous proportional mortality studies. METHODS: A cohort of 25,285 workers who entered the trade after 1949 was assembled from records of the international head office. Mortality was ascertained by linkage to the Canadian Mortality Registry at Statistics Canada. Standardised mortality ratios were computed using Ontario general population mortality rates as the reference. RESULTS: There were significant increases in lung cancer mortality rates (SMR 1.27; 95% CI 1.13 to 1.42). Increased lung cancer risk was observed among plumbers, pipefitters, and sprinkler fitters. Increased risk was observed among workers joining the Union as late as the 1970s. A random effects meta-analysis of this study and the two PMR studies found significant increases in oesophageal (RR 1.24; 95% CI 1.00 to 1.53), lung (RR 1.31; 95% CI 1.19 to 1.44), and haematological/lymphatic (RR 1.21; 95% CI 1.08 to 1.35) malignancies. CONCLUSIONS: The mortality pattern is consistent with the effects of occupational exposure to asbestos. Increased risk due to other respiratory carcinogens such as welding fume cannot be excluded. There are substantial amounts of asbestos in place in industrial and commercial environments. The education and training of workers to protect themselves against inhalation hazards will be necessary well into the future.

Aged↗
PubMed2003

Measurement of beryllium in lung tissue of a chronic beryllium disease case and cases with sarcoidosis.

BACKGROUND: The clinical features of chronic beryllium disease (CBD) are similar to many other chronic lung diseases. In particular, it may be difficult to distinguish it from pulmonary sarcoidosis since the two conditions may be very alike in clinical, pathological and radiological features. Aim To determine if the amount of beryllium found in the lungs could be used to differentiate CBD from sarcoidosis and controls. METHODS: Analyses for beryllium in the autopsied lung tissues of 29 cases and controls were carried out. The cases included one CBD, three confirmed sarcoidosis and 25 controls. Blocks of formalin-fixed tissues were analysed by an atomic absorption spectrophotometer equipped with a graphite furnace. A method for analysis of beryllium in air was modified to permit tissue analysis. RESULTS: The CBD case had a much higher average beryllium level, but some individual results were similar to controls and patients with sarcoidosis. CONCLUSION: The CBD case had beryllium levels within the range of values reported in the literature. The differentiation between CBD and sarcoidosis could not be made with reasonable assurance based only on the analytic result. Occupational history is very important in making a diagnosis of CBD, along with the analysis of tissues. Tissue analysis helped confirm the diagnosis of compensatable CBD in this particular case.

Berylliosis↗
PubMed2002

Primary cutaneous amoebiasis: case report with review of the literature.

BACKGROUND: Primary cutaneous amoebiasis is a rare clinical entity. The lesions can be successfully treated if suspected and correctly diagnosed. We report an interesting case with review of the literature. METHODS: A 25-year-old man presenting with primary cutaneous amoebiasis with extensive involvement of the anterior abdominal wall is described. Correct diagnosis eluded us for 2 years. Clinical suspicion and a simple bedside test (wet drop preparation examination) were sufficient to diagnose the lesion. Successful treatment was achieved with oral Metronidazole followed by split skin grafting. Only six cases of primary cutaneous amoebiasis could be traced in the literature. CONCLUSIONS: Primary cutaneous amoebiasis is extremely rare. Diagnosis is usually not suspected because of its rarity. Cutaneous amoebiasis responds readily to proper treatment, yet, if unrecognized and neglected, produces significant morbidity and may be fatal.

Abdominal Wall↗
PubMed2001

A comparison of international silica (alpha-quartz) calibration standards by Fourier transform-infrared spectrophotometry.

Seven international silica (alpha-quartz) standards were examined for relative purity to the US National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1878 Respirable alpha-quartz by Fourier Transform-Infrared Spectrophotometry (FT-IR). The standards examined have been used in North America, the UK, Australia and Germany. The 189 samples analyzed included NIST-SRM 1878, Min-U-Sil 5, Ottawa Silica Sand, Sikron F-600, A9950 (AUST 1), DQ12-Robock, DQ12-Bergbau. Size distributions of the standards were determined by Coulter Counter to be broadly similar with equivalent spherical volume median diameter ranging between 1.2 and 3 microm. The results showed the standards to differ by as much as 30% in relative purity. Consequently, an internationally agreed upon calibration standard is urgently needed. Min-U-Sil 5 based NIST-SRM 1878 or Sikron F-600 are the two most likely candidates. Any agreed standard must have a well characterized size distribution and closely match the respirable dust criteria. It should also be studied by both infrared spectrophotometry and X-ray diffraction techniques.

Calibration↗
PubMed2001

A laboratory evaluation of the accuracy and precision of the photovac snapshot portable gas chromatograph and the Dräger Chip Measurement System monitor for benzene in air measurements.

A laboratory evaluation of the accuracy and precision of two field instruments, the Photovac Snapshot Gas Chromatograph and the Dräger Chip Measurement System (CMS) Monitor, both capable of specific determination of benzene, was carried out. The evaluation was based on the generation of a test atmosphere of known concentration of benzene in a stainless steel calibration chamber and simultaneous sampling of the test atmosphere by each instrument. At the same time, the chamber atmosphere was continuously monitored by one or two data logging photoionization detector (PID) hydrocarbon analysers. A series of six, 10-minute charcoal tube air samples of the test atmosphere was also collected over the 1-hour run and analyzed by gas chromatography. Nine different concentrations ranging from 0.25 ppm to 8 ppm were used. Accuracy was evaluated using National Institute for Occupational Safety and Health (NIOSH) criteria. The Photovac GC consistently met the NIOSH recommended accuracy criteria of +/- 25 percent at or below 1 ppm of benzene, whereas the Drager CMS results generally fell slightly outside this criteria. Compared against less stringent accuracy criteria of +/- 35 percent, all Photovac GC results were acceptable but about 40 percent of Drager CMS results were not. The precision of Photovac GC (CV +/- 10%) is better than Drager CMS (CV = +/- 20% to 40%). Both instruments are, however, good field instruments provided their limitations are taken into account in their use.

Air Pollutants↗
PubMed1999

A comparison of sampling and analytical methods for assessing occupational exposure to diesel exhaust in a railroad work environment.

Methods of assessing occupational exposure to diesel exhaust were evaluated in a railroad work environment. The American Conference of Governmental Industrial Hygienists (ACGIH)-recommended elemental carbon and respirable combustible dust methods of sampling and analysis for assessing diesel exhaust were included in the study. A total of 215 personal and area samples were collected using both size-selective (nylon cyclone and Marple) and non-size-selective samplers. The results demonstrate that the elemental carbon method is suitable for the railroad environment and the respirable combustible dust method is not. All elemental carbon concentrations measured were below the proposed ACGIH Threshold Limit Value (TLV) of 0.15 mg/m3. The concentrations of oxides of nitrogen (nitric oxide and nitrogen dioxide) were also found to be below their respective TLVs. There is no correlation between elemental carbon or respirable combustible dust and the oxides of nitrogen. The elemental carbon as fraction of total carbon is about 13 percent, except for onboard locomotives where it is about 24 percent. Comparison of elemental carbon and respirable combustible dust measurements showed consistent relationships for most sampling locations, with respirable combustible dust concentrations 12 to 53 times higher than the elemental carbon levels.

Data Interpretation, Statistical↗
PubMed1998

Assessment of triethylamine and diethylamine emission from military gas mask canisters.

A study was undertaken to evaluate the suitability of four types of amine modified charcoal filter canisters (cartridge) for use with gas masks (respirators) by measuring emissions of triethylamine (TEA) and diethylamine (DEA). Sampling and analysis methods for TEA and DEA were validated and optimized to ensure accurate measurement at low levels. A total of 88 air samples were taken by the validated methods to measure concentrations of TEA and DEA emitted from gas mask canisters during simulated use in an environmental chamber. Samples were collected on a mannequin equipped with a breather pump and also on human volunteers. Very low levels of TEA and moderately low levels of DEA emissions were measured during the simulations. The C7 (KOH-TEA-BPL/ASC3T) gas mask canister giving the lowest emission has been selected for use by the Canadian Forces. The potential health hazard from TEA and DEA for soldiers using the gas masks, under normal conditions, based on estimated use of one to two days per month, for a maximum of 4 hours/day for a normal working lifetime, was considered to be minimal and acceptable.

Canada↗
PubMed1994

Evaluation of professional competency in occupational hygiene in Canada--the CRBOH program. Canadian Registration Board of Occupational Hygienists.

The Canadian Registration Board of Occupational Hygienists (CRBOH) was established in 1986 to provide a registration system for professional occupational hygienists in Canada. It was decided that registration would be based on a competency examination following an appropriate combination of academic qualification and relevant professional experience. While the examination was being developed hygienists who met certain educational and experience requirements and who held other certifications by examination (such as those of the American Board of Industrial Hygiene, the British Examining and Board in Occupational Hygiene, or the Conseil d'Accrediation en Hygiene Industrielle du Quebec) were registered. In 1989 CRBOH, after much deliberation and review of other existing certification examinations, selected a two-part scheme consisting of both written and oral examinations. The written examination includes both multiple choice and essay style questions. Only those candidates successfully completing the written examination are eligible for the oral examination. The first group of candidates was examined in the fall of 1990. The authors outline the strengths and weaknesses of various forms of evaluation of professional competency. The rationale for the selection of the CRBOH examination format is discussed in relation to forms of evaluation currently being used in the United States and the United Kingdom. The implication of CRBOH registration on the training and education of occupational hygienists in Canada is highlighted.

Canada↗
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↗
PubMed1992

Hydrocarbon exposures at petroleum bulk terminals and agencies.

Occupational exposures to the 55 hydrocarbon components of gasoline and petroleum products were measured at the bulk terminals and agencies of six Ontario petroleum companies during the summer of 1986. A total of 82 long-term (full-shift) and 111 short-term personal samples were taken over 3 months. The data, expressed as concentrations in milligrams per cubic meter, were highly variable and appeared to fit the lognormal distribution well. Full-shift exposures of bulk terminal drivers, agency drivers, and plantmen to total hydrocarbons (THC), computed as an n-hexane equivalent, and other hydrocarbon components for which exposure limits exist can be expected to exceed their respective 1986-1987 threshold limit value-time-weighted average (TLV-TWA) no greater than 1% of the time on the basis of the lognormal model. The short-term THC exposures of agency truck drivers can be expected to exceed the 1986-1987 TLV-short-term exposure limits about 7% of the time while top-loading and more than 17% while off-loading. For benzene, the short-term exceedance percentages are 1% and 4% for top- and off-loading operations, respectively. For long-term benzene exposures, up to 69% of the assessments can be expected to exceed the 1990-1991 proposed TLV-TWA of 0.3 mg/m3 (0.1 ppm). The full-shift hydrocarbon exposures of agency drivers were significantly higher than those for bulk terminal drivers. At the bulk terminals, the short-term hydrocarbon exposures during top-loading were significantly higher than during bottom-loading.

Dose-Response Relationship, Drug↗
PubMed1991

An evaluation of airborne nickel, zinc, and lead exposure at hot dip galvanizing plants.

Industrial hygiene surveys were conducted at three hot dip galvanizing plants to determine occupational exposure to nickel, zinc, and lead. All three plants employed the "dry process" and used 2% nickel, by weight, in their zinc baths. A total of 32 personal and area air samples were taken. The air samples were analyzed for nickel, zinc, and lead. Some samples were also analyzed for various species of nickel (i.e., metallic, soluble, and oxidic). The airborne concentrations observed for nickel and its three species, zinc, and lead at the three plants were all well below the current and proposed threshold limit values recommended by the American Conference of Governmental Industrial Hygienists (ACGIH).

Air Pollutants, Occupational↗
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 pragmatic approach to standard setting--the example of coal tar products and asphalt.

This article will outline a pragmatic approach directed to incorporating key elements of a scientific review of the literature and derive a proposal for an occupational exposure standard for coal tar, coal tar pitch, creosote, petroleum pitch, bitumen and asphalt, six substances which contain polynuclear aromatic hydrocarbons. Five approaches to the standard setting process are reviewed and their strengths and weaknesses discussed. Unfortunately there does not exist an acceptable epidemiological data set, other than the coke oven emission studies, on which to base a valid and reliable risk assessment model. Based on comparative potency experiments of complex mixtures, consideration of the state-of-the-art sampling and analytical methods, prevention of acute human health effects, and current existing standards for these substances throughout the world, a set of recommended exposure standards are derived for health policy makers.

Animals↗
PubMed1988

Cancer morbidity in lamp manufacturing workers.

A historical prospective study of cancer in lamp manufacturing workers in one plant was conducted. All men and women who worked for a total of at least 6 months and were employed at some time between 1960 and 1975 were included. Work histories were abstracted and subjects were divided according to whether they had worked in the coiling and wire drawing area (CWD). Cancer morbidity from 1964 to 1982 was ascertained via the provincial registry, and was compared with the site-specific incidence in Ontario, adjusting for age, sex and calendar period. Of particular interest were primary breast and gynecological cancers in women. The cancers of a priori concern were significantly increased in women in CWD, but not elsewhere in the plant. The excess was greatest in those with more than 5 yr exposure (in CWD) and more than 15 yr since first working in CWD, with eight cases of breast and gynecological cancers observed in this category compared with 2.67 expected. Only three cancers occurred in men in CWD. Environmental measurements had not been made in the past and little information was available on substances used in the 1940s and 1950s, the period when the women with the highest excess began employment. It is known that methylene chloride and trichlorethylene have been used, but not enough is known about the dates and patterns of use to draw any conclusions about their relationship with the increase in disease.

Breast Neoplasms↗