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Biomedical subjects

K Teschke

Publications and source records attributed to K Teschke.

At least 55 records · Page 3Linked to original sources
PubMed1997

The relationship of lead in soil to lead in blood and implications for standard setting.

As part of a soil lead regulation process, this review was conducted to determine the association between lead in soil and established human health effects of lead or validated biomarkers of lead exposure. We reviewed only studies where soil exposure could be distinguished from other sources of lead and whose design could reasonably be used to infer a causal relationship between soil lead and either biomarkers or health effects. No such studies of health effects were found. Studies describing a quantitative relationship between soil lead and blood lead did meet our criteria: 22 cross-sectional studies in areas with polluted soil; and three prospective studies of soil lead pollution abatement trials. The cross-sectional studies indicated that, compared to children exposed to soil lead levels of 100 ppm, those exposed to levels of 1000 ppm had mean blood lead concentrations 1.10-1.86 times higher and those exposed to soil lead levels of 2000 ppm had blood lead concentrations 1.13-2.25 times higher. The prospective studies showed effects within the ranges predicted by the cross-sectional studies. Differences in results between studies were surprisingly modest and likely explainable by random sampling error, different explanatory variables included in data analyses and differences in methods of measuring lead in environmental specimens.

Adolescent↗
PubMed1997

What to do about softwood? A review of respiratory effects and recommendations regarding exposure limits.

Wood dust has been classified as a human carcinogen by the International Agency for Research on Cancer with a footnote that the evaluation was based on a marked excess of sino-nasal cancer among workers exposed primarily to hardwood dusts. Because the epidemiologic data on the carcinogenic effects of softwoods are weaker than for hardwoods, standard setting for softwood dust presents a greater dilemma. Unfortunately, the studies of wood dust and cancer do not have the quantitative exposure data necessary for standard setting for either hardwoods or softwoods. Asthma, non-asthmatic airflow obstruction, and both upper and lower respiratory symptoms have been associated with exposure to both 'allergenic' and 'non-allergenic' softwood dusts, and an association with increasing intensity of exposure has been observed in multiple studies. The available evidence seems to indicate that to prevent these nonmalignant effects, the level of exposure to all softwood dust should be at least as low 2 mg/m3. A standard of 1 mg/m3 may be more appropriate to provide a safety margin to protect more sensitive workers. It may be that some of the health effects observed are due to the natural components of wood, such as resin acids or monoterpenes, or to molds.

Air Pollutants, Occupational↗
PubMed1997

International data base of exposure measurements in the pulp, paper and paper product industries.

An international data base of exposure measurements in the pulp, paper and paper product industries was constructed to be used in exposure assessment for epidemiology studies and hazard control. Industrial hygiene and biological monitoring data were collected from countries participating in the multicentric study of the International Agency for Research on Cancer. Each measurement was characterized by country, mill type and number, department, job, agent measured, sampling method, measurement result in the standard unit, duration and date of sampling, assessment of representativeness, measurer, purpose of measurements, and remarks (e.g. on measurement sites and biases). Over 31,000 measurement results on 246 different chemical agents from 13 countries were available from pulp (45% of measurements), paper/paperboard/recycling (12%) and paper product (11%) mills or from their non-production departments (23%). Most measurements (82%) were carried out after 1980. The most frequently measured group of agents was inorganic gases (35%), followed by organic compounds (25%), solvents (18%), mineral dusts (12%), metals (6%) and bioaerosols (3%). Over 90% of the measurements were without an obvious bias, but their true representativeness is difficult to assess. Concentrations of various agents, including sulfur dioxide, chlorine dioxide, carbon monoxide, nitrogen dioxide, ozone, ammonia, formaldehyde and some solvents, often exceeded current occupational exposure limits. This data base summarizes a great deal of previously unpublished exposure data, provides a unique opportunity to study exposure patterns at the international level and identifies exposure situations that require further attention and investigation.

Bias↗
PubMed1997

Exposure levels and determinants of inhalable dust exposure in bakeries.

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m3 (range: 0.1-110 mg/m3). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels.

Analysis of Variance↗
PubMed1997

Surveillance of nasal and bladder cancer to locate sources of exposure to occupational carcinogens.

OBJECTIVE: To locate sources of occupational exposure to nasal and bladder carcinogens for surveillance follow up in British Columbia, Canada. METHODS: Incident cases of nasal cancer (n = 48), bladder cancer (n = 105), and population based controls (n = 159) matched for sex and age, were interviewed about their jobs, exposures, and smoking histories. Odds ratios (ORs) were calculated for 57 occupational groups with stratified exact methods to control for age, sex, and smoking. RESULTS: Occupational groups at increased risk of nasal cancer included: textile workers (six cases, OR 7.6); miners, drillers, and blasters (six cases, OR 3.5); welders (two cases, OR 3.5); pulp and paper workers (three cases, OR 3.1); and plumbers and pipefitters (two cases, OR 3.0). Nasal cancer ORs were not increased in occupations exposed to wood dust, possibly due to low exposures in local wood industries. Strongly increased risks of bladder cancer were found for sheet metal workers (four cases, OR 5.3), miners (19 cases, OR 4.5), gardeners (six cases, OR 3.7), and hairdressers (three cases, OR 3.2). Among occupations originally considered at risk, the following had increased risks of bladder cancer: painters (four cases, OR 2.8); laundry workers (five cases, OR 2.3); chemical and petroleum workers (15 cases, OR 1.8); machinists (eight cases, OR 1.6); and textile workers (three cases, OR 1.5). CONCLUSIONS: Occupational groups with increased risks and three or more cases with similar duties were selected for surveillance follow up. For nasal cancer, these included textile workers (five were garment makers) and pulp and paper workers (three performed maintenance tasks likely to entail stainless steel welding). For bladder cancer, these included miners (12 worked underground), machinists (five worked in traditional machining), hairdressers (three had applied hair dyes), and laundry workers (three were drycleaners).

Aged↗
PubMed1997

Mortality and cancer incidence among sawmill workers exposed to chlorophenate wood preservatives.

OBJECTIVES: This study examined the association between exposure to chlorophenates and the risk of soft tissue sarcoma; non-Hodgkin's lymphoma; Hodgkin's disease; and cancers of the lung, nose, and nasopharynx. METHODS: A retrospective cohort study was conducted of 26487 workers employed for at least 1 year between 1950 and 1985 in 11 chlorophenate-using and 3 non-using sawmills in British Columbia, Canada. Exposures by job were ascertained with interviews of senior employees. RESULTS: Probabilistic record linkage to the Canadian Mortality Data Base and the British Columbia Cancer Registry found 4710 deaths between 1950 and 1990, and 1547 incident cases of cancer between 1969 and 1989. None of the cancers of interest had elevated mortality related to chlorophenate exposure. Non-Hodgkin's lymphoma incidence (n = 65) increased with increasing chlorophenate exposure hours, yielding the following standardized incidence ratios: less than 120 hours 0.68; 120 to 1999 hours, 0.59; 2000 to 3999 hours, 1.04; 4000 to 9999 hours, 1.02; and 10000 or more hours, 1.30. CONCLUSIONS: These results are consistent with the borderline positive associations seen in other recently reported studies of chlorophenate-exposed workforces.

British Columbia↗
PubMed1996

Unrecognized asbestos-induced disease.

It is being slowly recognized that there is serious under-reporting of cancers that are occupationally related, in the sense that they would not have occurred without the occupational exposure. Data from the Workers' Compensation Boards of New South Wales in Australia and British Columbia in Canada relating to disease attributable to asbestos exposure indicate that in both jurisdictions the ratio of lung cancer cases to mesothelioma cases is much lower than epidemiological studies indicate must be occurring. Over the period from 1980 to 1994, if both jurisdictions are considered together, about 1,207 cases of lung cancer that would not have occurred without asbestos exposure went unrecognized as occupationally related. The data also suggest that it is unlikely that radiological asbestosis should be regarded as a necessary condition for there to be an increased risk of lung cancer following asbestos exposure.

Asbestos↗
PubMed1996

Reliability of retrospective chlorophenol exposure estimates over five decades.

For a cohort study of chlorophenate-exposed sawmill workers, historical exposures from the 1940s to the 1980s were estimated by teams of 9-20 employees (each interviewed individually). The mill histories were divided into eras when jobs and exposures were relatively stable. Raters with at least 5 years of work experience in an era were asked to estimate the frequency and duration of exposure for each job in the mill. Reliability measures for these estimates were calculated for each of the 39 mill and time period combinations, using the individual intraclass correlation coefficient (ICCind) to assess agreement between raters and the group intraclass correlation coefficient (ICCgroup) to assess the stability of the mean estimates of exposure. ICCind were low, with means that increased from 0.24 to 0.35 over the five decades. ICCgroup were considerably higher (means increasing from 0.78 to 0.88 over time), indicating that the number of raters used in this study was sufficient to produce stable average estimates of exposure throughout the study period. These data confirm the intuitive expectation that reliability of exposure estimates decreases when reconstruction of conditions in the distant past is required, and therefore that the random component of exposure misclassification is a greater threat to validity in these earlier time periods.

Analysis of Variance↗
PubMed1996

Pharmacokinetic model of dioxin and furan levels in adipose tissue from sawmill work involving chlorophenate fungicides.

Sawmill workers in British Columbia (B.C.), Canada, have been exposed to chlorophenate fungicides which are known to be contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Due to concern about the potential of these workers to have significant body burdens of PCDD/Fs, and the absence of measurements in these workers, a single-compartment pharmacokinetic model was developed to estimate the concentration of PCDD/Fs in the fat tissue of the sawmill workers. Data from a large cohort of B.C. sawmill workers and literature-based data on chlorophenate exposures and PCDD/F concentrations in chlorophenates were used in Monte Carlo simulations to predict a PCDD/F body burden distribution. The median concentrations of HxCDF and HpCDF predicted using the model for the B.C. sawmill worker population exceeded the range measured in unexposed populations. PeCDF and OCDF concentrations exceeded the range measured in unexposed populations at the 70th percentile of the model-predicted distribution, and PeCDD at the 90th percentile. The primary limitation of the model was the scarcity of input data about actual dermal and inhalation exposures to chlorophenates.

Adipose Tissue↗
PubMed1996

Reproductive effects of paternal exposure to chlorophenate wood preservatives in the sawmill industry.

OBJECTIVES: The purpose of the study was to determine whether paternal occupational exposure to dioxincontaminated chlorophenols is associated with an increased risk of congenital anomalies or other adverse reproductive outcomes in offspring. METHODS: As a result of a multistep linkage, 19675 births between 1952 and 1988 were identified as children of a cohort of 9512 fathers who had worked at least one year in British Columbia sawmills where chlorophenate wood preservatives had been used. A nested case-referent analysis was applied, using conditional logistic regression, with five referents matched per case according to year of birth and gender. Chlorophenate exposure was based on expert raters' estimations of hours of exposure applied to specific time windows prior to birth. RESULTS: The offspring of male sawmill workers were at increased risk for developing congenital anomalies of the eye, particularly congenital cataracts; elevated risks for developing anencephaly or spina bifida and congenital anomalies of genital organs were shown according to specific windows of exposure. No associations were found for low birthweight, prematurity, stillbirths, or neonatal deaths. CONCLUSIONS: The study adds further support to the hypothesis of male-mediated developmental toxicity. Paternal exposure to chlorophenates was associated with the development of certain congenital anomalies in offspring.

Abnormalities, Drug-Induced↗
PubMed1995

A classification scheme for aggregating U.S. census occupation and industry codes.

The use of occupation as a surrogate for workplace exposures when more specific information is unavailable is common yet is particularly challenging in studies involving many diverse occupations. A classification scheme that aggregates workers based on similar job tasks and potential exposures was developed for use in a Canadian study, and its adaptation for a similar U.S. study is described. The 56 occupational categories and 1980 U.S. census occupation and industry codes used to create each are presented. The scheme was developed using the distribution of occupations and industries in two limited study populations, and no exposure measurements were taken in its preparation. However, the aggregation of jobs with similar exposures has practical utility in the analysis of a large number of specific occupations, each with a small number of workers. As a result, the scheme presented can provide a starting point for researchers facing this task in the analysis of case-control occupational data.

Data Collection↗
PubMed1995

Maintenance of stellite and tungsten carbide saw tips: respiratory health and exposure-response evaluations.

OBJECTIVE: To study exposure to cobalt and chromium in saw maintenance rooms and test respiratory health among saw filers at lumber mills. Hard-metal lung disease is associated with cobalt in the manufacture of tungsten carbide tools; recently it has also been reported among tool maintenance workers. Lumber mills often use saws tipped with tungsten carbide or with a newer alloy, stellite (containing more cobalt, as well as chromium). METHODS: A cross sectional study of 118 saw filers at eight lumber mills was carried out that included a standardised questionnaire, spirometry, personal air sampling, and examination of tasks every 10 minutes (by observation). Comparison data were from a study of bus mechanics tested with similar methods. RESULTS AND CONCLUSION: Cobalt exposure was associated with tungsten carbide grinding but not with stellite grinding. Chromium exposure was associated mainly with stellite welding. Saw filers had a twofold increase in phlegm and wheeze (P < 0.01) and a threefold increase in cough, phlegm, and wheeze related to work (P < 0.001), but no increase in breathlessness. Stellite welding was associated with a significant increase in nasal symptoms and cough related to work and a small decrease in airflow (forced expiratory volume in one second/forced vital capacity (FEV1/FVC%), P < 0.05). Saw filers wet grinding with tungsten carbide had significant reductions in forced expiratory lung volumes (FEV1 and FVC, P < 0.05) and were significantly more likely to have FEV1 and FVC values in the abnormal range. Cobalt exposure (in wet grinding) and duration of work that involved tungsten carbide grinding were both associated with significant reductions in FEV1 and FVC. Average cobalt exposures in this study were about 5 micrograms/m3, well below the currently accepted permissible concentration, which suggests that the current workplace limit for cobalt may be too high.

Adult↗
PubMed1994

Effect of different questionnaire formats on reporting of occupational exposures.

During an exposure monitoring study, 78 saw maintenance tradesmen were randomly assigned to be interviewed about their exposures using one of two questionnaire formats: open-ended and partly prompted questions about five categories of materials; and detailed prompting about 75 agents. The more open-ended questionnaire elicited fewer exposure responses overall, but more responses about agents not included on the detailed questionnaire. Composite materials and trade name products were more frequently cited as exposures than individual metals or compounds. Validity of responses was ascertained using air measurements (individual metals) or observations of the employees (composite materials). Sums of sensitivities and specificities were very low (near 1.0) for most of the metals for both types of questionnaire. For composite materials, validity improved substantially. Sensitivities with the partly promoted format (0.44-0.85) were always lower than with detailed prompting (0.80-1.00). Specificities were usually, but not always, higher with partial prompting (0.66-0.92) than with detailed prompting (0.18-0.86). Selection of questionnaire format for an epidemiologic study would depend on the likely prevalence of exposure in controls and the effects of trade-offs in sensitivity and specificity.

Data Collection↗
PubMed1994

Strategies for determining occupational exposures in risk assessments: a review and a proposal for assessing fungicide exposures in the lumber industry.

To select an exposure monitoring protocol for assessing the occupational risk of fungicides in the lumber industry, the main strategies for determining exposures for risk assessment were reviewed. A survey of lumber industry work sites using fungicides observed the methods of application and opportunities for exposure. In addition, a review of existing measurement data was done. These investigations indicated that fungicide application techniques and process locations were varied from site to site, such that it would be extremely difficult to select a few representative locations for quasi-experimental studies, as is usually done in agricultural pesticide exposure assessment. Existing measurement data mainly describe exposures to fungicides no longer in use, and do not cover the range of application techniques or process technology observed in the survey. A probability sample of the exposed population was therefore proposed.

Environmental Monitoring↗
PubMed1994

Electric and magnetic fields at three pulp and paper mills.

Extremely low frequency (60 Hz) electric and magnetic field levels were measured at three Canadian pulp and paper mills, using area point-in-time measurements. Most electric field levels were below the limit of detection of 1 V/m (92 of 132 measurements); the highest measured field was 47 V/m. Measured magnetic field strengths ranged from less than the limit of detection (0.125 mG, 2 of 132 measurements) to 706 mG, with a median of 1.6 mG. Magnetic field levels were higher in mills that consume more electric power, but worker exposures could not be predicted according to plant power consumption. Overall, electric and magnetic field levels in the three pulp and paper mills were similar to those experienced by the general population. However, maximum magnetic field intensities in some areas were as high as those experienced by electrical workers.

British Columbia↗
PubMed1994

Level and distribution of employee exposures to total and respirable wood dust in two Canadian sawmills.

Personal respirable (N = 230) and total (N = 237) dust measurements were made in two coastal British Columbia sawmills using a sampling strategy that randomly selected workers from all jobs in the mills over two seasons. Information about job title, department, season, weather conditions, location of the job relative to wood-cutting machines, and control measures also was collected at the time of sampling. Only 16 respirable wood dust samples were above the detection limit of 0.08 mg/m3; all 16 had levels < or = 0.20 mg/m3. Total wood dust concentrations were also low (36% less than the detection limit), with a mean of 0.51 mg/m3, and ranging from < 0.08 to 52 mg/m3. Measurements of exposure taken close to chippers, planers, and multiple saws had the highest total wood dust levels. Sawmill department and booth enclosures also were associated with wood dust concentrations, while local exhaust ventilation and weather conditions were not. Wood dust levels in this study were generally lower than in other studies of this industry, but most sawmill investigations report mean wood dust concentrations lower than those measured in the furniture and cabinetmaking industries, where concerns about wood dust exposures initially were raised.

British Columbia↗
PubMed1992

Occupational cancer in Canada: what do we know?

OBJECTIVE: To examine the reporting of cases of occupational cancer in Canada in order to determine reporting requirements, the availability of data, the characteristics of reported cancers and the completeness of reporting. DESIGN: Descriptive epidemiologic study based on data requested from workers' compensation boards (WCBs) and cancer registries in each province and territory from 1980 to 1989. OUTCOME MEASURES: The number of claims accepted and rejected by the WCBs; year of claim, cancer site, sex of claimant, age of claimant at diagnosis, occupation, industry, exposure agent and reasons for rejection of claims; and new primary cancers according to site, age and sex. RESULTS: Reporting of occupational cancer by physicians is required in Alberta, Saskatchewan and Newfoundland. Only British Columbia, Saskatchewan and Ontario were able to provide all the requested information about the claims. Of the 1026 claims in these three provinces almost all were by men, and about two-thirds were for cancers of the respiratory tract. Asbestos was listed as the etiologic agent in more than one-third of the cases. A comparison of the proportion of incident cancers accepted as occupational by the WCBs with the estimated proportion of cancers in the general population attributable to occupation (based on population-attributable risk percentages from epidemiologic data) suggests that less than 10% of occupational cancers [corrected] are compensated. The main source of the deficit is underreporting to WCBs rather than rejection of claims. CONCLUSIONS: The availability of data about occupational cancers in Canada is inconsistent from jurisdiction to jurisdiction, and reporting is incomplete. An active disease surveillance system and additional education of physicians and workers about work-related illnesses may be required to improve reporting.

Age Factors↗