Development of and Selected Performance Characteristics of CANJEM, a General Population Job-Exposure Matrix Based on Past Expert Assessments of Exposure.

Objectives: We developed a job-exposure matrix called CANJEM using data generated in population-based case-control studies of cancer. This article describes some of the decisions in developing CANJEM, and some of its performance characteristics. Methods: CANJEM is built from exposure information from 31673 jobs held by study subjects included in our past case-control studies. For each job, experts had evaluated the intensity, frequency, and likelihood of exposure to a predefined list of agents based on jobs histories and descriptions of tasks and workplaces. The creation of CANJEM involved a host of decisions regarding the structure of CANJEM, and operational decisions regarding which parameters to present. The goal was to produce an instrument that would provide great flexibility to the user. In addition to describing these decisions, we conducted analyses to assess how well CANJEM covered the range of occupations found in Canada. Results: Even at quite a high level of resolution of the occupation classifications and time periods, over 90% of the recent Canadian working population would be covered by CANJEM. Prevalence of exposure of specific agents in specific occupations ranges from 0% to nearly 100%, thereby providing the user with basic information to discriminate exposed from unexposed workers. Furthermore, among exposed workers there is information that can be used to discriminate those with high exposure from those with low exposure. Conclusions: CANJEM provides good coverage of the Canadian working population and possibly that of several other countries. Available in several occupation classification systems and including 258 agents, CANJEM can be used to support exposure assessment efforts in epidemiology and prevention of occupational diseases.

Assessment of workers' exposure to microorganisms when using biological degreasing stations.

Biological degreasing stations (BDSs) are used by mechanics. These BDSs use a water-based solution with a microbial degradation process. Occupational exposure during the use of BDSs has not been reported and few studies have identified the bacteria present. The objectives were to measure the concentration of microorganisms during BDSs' use and monitor the bacterial community in the liquid over time. Five mechanical workshops were studied. Six 30-min samples were taken at each workshop over one year. Bioaerosols in the ambient air samples were collected with Andersen impactors near the BDS Bioaerosols in the workers' breathing zone (WBZ) were collected on filters. Fresh bio-degreasing fluids were collected from unopened containers, and used bio-degreasing fluids were collected in the BDS. The results show that the use of BDSs does not seem to increase bioaerosols concentrations in the WBZ (concentrations lower than 480 CFU/m3) and that the bacterial communities (mainly yeasts, Bacillus subtilis and Pseudomonas aeruginosa) in the bio-degreasing fluids change through time and differ from the original community (B. subtilis). This study established that workers using BDSs were exposed to low levels of bioaerosols. No respiratory protection is recommended based on bioaerosols concentrations, but gloves and strict personal hygiene practices are essential.

Investigation of occupational asthma: Do clinicians fail to identify relevant occupational exposures?

BACKGROUND: Specific inhalation challenges (SIC) enable the identification of the agent responsible of occupational asthma (OA). A clinician may fail to identify a specific agent in the workplace, which may potentially lead to a misdiagnosis. The expert assessment method performed by an occupational hygienist has been used to evaluate occupational exposures in epidemiological studies. OBJECTIVE: The broad aim of the present study was to evaluate the contribution of an expert assessment performed by an occupational hygienist to the diagnosis of OA. The specific aim was to compare workplace exposures identified by an occupational hygienist and by chest physicians in subjects with positive SICs and subjects with asthma, but with a negative SIC. METHODS: SICs were performed in 120 cases: 67 were positive and 53 were negative. A clinician assessed occupational exposures to sensitizers during a routine clinical evaluation preceding the performance of the SIC. An expert assessment of occupational exposures was performed by an occupational hygienist blind to the result of the SIC. RESULTS: The occupational hygienist identified the causal agent in 96.7% of the 61 cases of positive SIC. In 33 (62.3%) cases of negative SICs, the occupational hygienist identified ≥1 sensitizing agent(s) that had not been identified by the clinician. CONCLUSION: The hygienist identified the causal agent in almost all subjects with OA. In contrast, the clinician failed to identify potential exposures to sensitizers in >60% of the negative SIC subjects, which may have resulted in some subjects being misdiagnosed as not having OA.

Silica exposure during construction activities: statistical modeling of task-based measurements from the literature.

Many construction activities can put workers at risk of breathing silica containing dusts, and there is an important body of literature documenting exposure levels using a task-based strategy. In this study, statistical modeling was used to analyze a data set containing 1466 task-based, personal respirable crystalline silica (RCS) measurements gathered from 46 sources to estimate exposure levels during construction tasks and the effects of determinants of exposure. Monte-Carlo simulation was used to recreate individual exposures from summary parameters, and the statistical modeling involved multimodel inference with Tobit models containing combinations of the following exposure variables: sampling year, sampling duration, construction sector, project type, workspace, ventilation, and controls. Exposure levels by task were predicted based on the median reported duration by activity, the year 1998, absence of source control methods, and an equal distribution of the other determinants of exposure. The model containing all the variables explained 60% of the variability and was identified as the best approximating model. Of the 27 tasks contained in the data set, abrasive blasting, masonry chipping, scabbling concrete, tuck pointing, and tunnel boring had estimated geometric means above 0.1mg m(-3) based on the exposure scenario developed. Water-fed tools and local exhaust ventilation were associated with a reduction of 71 and 69% in exposure levels compared with no controls, respectively. The predictive model developed can be used to estimate RCS concentrations for many construction activities in a wide range of circumstances.

Occupational exposure to silica in construction workers: a literature-based exposure database.

We created an exposure database of respirable crystalline silica levels in the construction industry from the literature. We extracted silica and dust exposure levels in publications reporting silica exposure levels or quantitative evaluations of control effectiveness published in or after 1990. The database contains 6118 records (2858 of respirable crystalline silica) extracted from 115 sources, summarizing 11,845 measurements. Four hundred and eighty-eight records represent summarized exposure levels instead of individual values. For these records, the reported summary parameters were standardized into a geometric mean and a geometric standard deviation. Each record is associated with 80 characteristics, including information on trade, task, materials, tools, sampling strategy, analytical methods, and control measures. Although the database was constructed in French, 38 essential variables were standardized and translated into English. The data span the period 1974-2009, with 92% of the records corresponding to personal measurements. Thirteen standardized trades and 25 different standardized tasks are associated with at least five individual silica measurements. Trade-specific respirable crystalline silica geometric means vary from 0.01 (plumber) to 0.30 mg/m³ (tunnel construction skilled labor), while tasks vary from 0.01 (six categories, including sanding and electrical maintenance) to 1.59 mg/m³ (abrasive blasting). Despite limitations associated with the use of literature data, this database can be analyzed using meta-analytical and multivariate techniques and currently represents the most important source of exposure information about silica exposure in the construction industry. It is available on request to the research community.

Occupational risk factors associated with work-exacerbated asthma in Quebec.

BACKGROUND: There is limited information regarding the occupational exposures of subjects with a diagnosis of work-exacerbated asthma (WEA). OBJECTIVES: To: (1) identify potential specific occupational, chemical, biological and physical agents associated with incident cases of WEA and (2) compare these agents with occupational exposures of occupational asthma (OA) and non-work-related asthma (NWRA) cases. METHODS: Subjects were workers with work-related asthma (WRA) or NWRA referred between 2005 and 2008 to two Quebec clinics specialised in the field of WRA. Specific inhalation challenges were performed to differentiate OA from WEA. Work exposures were assessed using a detailed occupational questionnaire. Exposures to 41 chemical and biological agents were coded in a semiquantitative way according to a combination of indices for concentration in workplace air, frequency and confidence of exposure by an occupational hygienist expert in occupational exposure coding. This expert was blind to the medical status of WEA, OA or NWRA. Five physical agents were coded on a yes/no scale. RESULTS: 153 subjects were enrolled (53 WEA, 67 OA and 33 NWRA). WEA cases were significantly more exposed to ammonia, engine exhaust fumes, silica, mineral fibres, aerosol propellants and solvents, and significantly less exposed to animal derived dust and enzymes than were OA cases. Exposure to physical conditions did not differ between WEA and OA. CONCLUSIONS: Exposures associated with WEA differ from those associated with OA in this study. A proportion of subjects with WEA may suffer from low-dose irritant asthma, which remains a hypothesis to be tested.

Statistical modeling of crystalline silica exposure by trade in the construction industry using a database compiled from the literature.

A quantitative determinants-of-exposure analysis of respirable crystalline silica (RCS) levels in the construction industry was performed using a database compiled from an extensive literature review. Statistical models were developed to predict work-shift exposure levels by trade. Monte Carlo simulation was used to recreate exposures derived from summarized measurements which were combined with single measurements for analysis. Modeling was performed using Tobit models within a multimodel inference framework, with year, sampling duration, type of environment, project purpose, project type, sampling strategy and use of exposure controls as potential predictors. 1346 RCS measurements were included in the analysis, of which 318 were non-detects and 228 were simulated from summary statistics. The model containing all the variables explained 22% of total variability. Apart from trade, sampling duration, year and strategy were the most influential predictors of RCS levels. The use of exposure controls was associated with an average decrease of 19% in exposure levels compared to none, and increased concentrations were found for industrial, demolition and renovation projects. Predicted geometric means for year 1999 were the highest for drilling rig operators (0.238 mg m(-3)) and tunnel construction workers (0.224 mg m(-3)), while the estimated exceedance fraction of the ACGIH TLV by trade ranged from 47% to 91%. The predicted geometric means in this study indicated important overexposure compared to the TLV. However, the low proportion of variability explained by the models suggests that the construction trade is only a moderate predictor of work-shift exposure levels. The impact of the different tasks performed during a work shift should also be assessed to provide better management and control of RCS exposure levels on construction sites.

Frequency of work-related respiratory symptoms in workers without asthma.

BACKGROUND: Clinicians are faced with subjects complaining of work-related respiratory symptoms (WRS) without any evidence of asthma. We sought to assess the prevalence of subjects with WRS without asthma in a cohort of workers referred for possible work-related asthma (WRA) as well as compare the characteristics and the work environment of subjects with WRS to subjects with WRA. METHODS: A prospective observational study of workers referred for possible WRA over a 1-year period. Detailed medical and occupational questionnaires were administered. Pulmonary function tests as well as specific-inhalation challenges were performed. RESULTS: One hundred twenty workers were investigated. Fifty-one had WRA while 69 had WRS. The type and the severity of the respiratory symptoms were similar in both groups, except for wheezing which was more frequently reported in subjects with WRA (32 (62.7%)) than in subjects with WRS (16 (23.2%)) (P < 0.01). Both the workers with WRS and WRA were mainly employed in the manufacturing sector (64.7% (WRA) and 71% (WRS)). At the time of the first assessment 64.7% of subjects with WRA and 56.5% with WRS had left their workplace because of their bothersome respiratory symptoms. CONCLUSIONS: Subjects with WRS without asthma represent a large proportion of the subjects assessed in clinics specialized in the field of WRA. Like subjects with WRA, the population with WRS is likely to represent a significant medical burden. The similarity of the symptoms between the WRA and the WRS groups emphasizes the need to perform a thorough and objective investigation to diagnose WRA.

A web tool for the identification of potential interactive effects of chemical mixtures.

This project was undertaken to develop a toxicological database allowing the identification of possible additive or other interactive effects of mixtures present in the work environment. In the first phase of the project, whose findings have already been published, critical toxicological data were compiled for each of the 695 chemical substances in the Quebec Occupational Health Regulation, allowing the prediction of potential additivity among components of a mixture. In the second phase of this project, the types of interactions for mixtures most likely to be found in workplaces and for which primary literature data are available were specified. The toxicological data were evaluated only for realistic exposure concentrations up to the short-term exposure limit or ceiling value or five times the 8-hr time-weighted average (TWA) permissible exposure limit (PEL) for human data and up to 100 times the 8-hr TWA PEL or ceiling value for animal studies. In total, 675 studies were evaluated covering 209 binary mixtures of substances. For the majority of cases where potential additivity was identified in Phase 1, there is a lack of toxicological data in the primary literature. In these cases, the results of the first phase will be useful as the default hypothesis. The resulting database integrates the results from both phases of the project. A web-based computer tool allows the user to determine whether there is potential additivity or interaction among components of a mixture.

Technical, occupational health and environmental aspects of metal degreasing with aqueous cleaners.

Aqueous cleaners used for metal degreasing are detergent formulations containing surfactants (such as linear alkylbenzene sulphonates, alkylphenol ethoxylates or alcohol ethoxylates), builders (such as hydroxides, phosphates or silicates), sequestrants (such as EDTA or NTA), anti-corrosive agents (such as ethanolamines), solvents (such as glycol ethers or d-limonene) and other specialty additives. Generally sold as concentrates, they are typically diluted between 3 and 20 times in water, leading to solutions containing only a few per cent active products. The cleaning efficiency depends on physicochemical phenomena such as wetting, solubilization, emulsification, dispersion, sequestration and saponification, and is enhanced by thermal and mechanical energy. Cleaning equipment is based on spraying or immersion of the parts and may include drying and rinsing steps. Because of the complexity and variability of the mixtures, the occupational health and environmental evaluation of aqueous cleaners is based on the study of their components. Aqueous cleaners are generally believed to present a low risk to workers' health and to the environment. However, some anionic surfactants and strong alkalis are skin and eye irritants, ethanolamines are allergenic and several glycol ethers of the ethylene glycol family are proven systemic toxicants that are easily absorbed through the skin. Although most components of aqueous cleaners are biodegradable and of low ecotoxicity, alkylphenol ethoxylates degrade into persistent and toxic compounds. Phosphates, if released directly into the environment, may cause eutrophication of rivers and lakes. Waste recycling or treatment by specialized facilities is usually required for spent solutions containing contaminants such as oils and heavy metals. From a technical, toxicological and environmental standpoint, aqueous cleaners can be used successfully to replace traditional organic solvents used in metal degreasing.

Sinonasal cancer and occupational exposures: a pooled analysis of 12 case-control studies.

OBJECTIVE: In order to examine the associations between sinonasal cancer and occupational exposures other than wood dust and leather dust, the data from 12 case-control studies conducted in seven countries were pooled and reanalyzed. METHODS: The pooled data set included 195 adenocarcinoma cases (169 men and 26 women), 432 squamous cell carcinomas (330 men and 102 women), and 3136 controls (2349 men and 787 women). Occupational exposures to formaldehyde, silica dust, textile dust, coal dust, flour dust, asbestos, and man-made vitreous fibers were assessed with a job-exposure matrix. Odds ratios (ORs) were adjusted for age, study, wood dust, and leather dust, or other occupational exposures when relevant. 95% confidence intervals (CIs) were estimated by unconditional logistic regression. RESULTS: A significantly increased risk of adenocarcinoma was associated with exposure to formaldehyde. The ORs for the highest level of exposure were 3.0 (Cl = 1.5-5.7) among men and 6.2 (CI=2.0-19.7) among women. An elevated risk of squamous cell carcinoma was observed among men (OR=2.5, CI=0.6-10.1) and women (OR = 3.5, CI = 1.2-10.5) with a high probability of exposure to formaldehyde. Exposure to textile dust was associated with non-significantly elevated risk of adenocarcinoma, among women only: the OR for the high level of cumulative exposure was 2.5 (CI = 0.7-9.0). High level of asbestos exposure was associated with a significantly increased risk of squamous cell carcinoma among men (OR = 1.6, CI = 1.1-2.3). CONCLUSIONS: The results of this pooled analysis support the hypothesis that occupational exposure to formaldehyde increases the risk of sinonasal cancer, particularly of adenocarcinoma. They also indicate an elevated risk of adenocarcinoma among women exposed to textile dust, and suggest that exposure to asbestos may increase the risk of squamous cell carcinoma.