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.

Influence of Water on the Dynamic Adsorption of Chlorinated VOCs on Active Carbon: Relative Humidity of the Gas Phase versus Pre-Adsorbed Water

The present work deals with the influence of water on the adsorption of two chlorinated volatile organic compounds (VOCs) on activated carbons (ACs) having very different pore textures and surface chemistry. Two kinds of moisture were considered, viz. pre-adsorbed on the AC or present as steam in the gaseous phase, at various relative humidities ranging from 30% to 75%.

It is shown that the adsorption of the VOCs depends on the kind of moisture. If the latter is pre-adsorbed, water is just displaced by the VOCs (overshoot). The adsorption capacities of the AC remain unchanged and only some minor changes in the shape of the breakthrough front, corresponding to hindered diffusion, may sometimes occur.

In contrast, the simultaneous adsorption of steam and VOC leads to competition between water and the chlorinated compound, with direct consequences on the adsorption kinetics and capacities of the AC. However, the decrease of the water-induced adsorption performances depends strongly on the AC and the VOC (through different VOC/AC and water/VOC interactions), and on the concentration of the VOC.

Towards nanoprinting with metals on graphene

Graphene and carbon nanotubes are envisaged as suitable materials for the fabrication of the new generation of nanoelectronics. The controlled patterning of such nanostructures with metal nanoparticles is conditioned by the transfer between a recipient and the surface to pattern. Electromigration under the impact of an applied voltage stands at the base of printing discrete digits at the nanoscale. Here we report the use of carbon nanotubes as nanoreservoirs for iron nanoparticles transfer on few-layer graphene. An initial Joule-induced annealing is required to ensure the control of the mass transfer with the nanotube acting as a ‘pen' for the writing process. By applying a voltage, the tube filled with metal nanoparticles can deposit metal on the surface of the graphene sheet at precise locations. The reverse transfer of nanoparticles from the graphene surface to the nanotube when changing the voltage polarity opens the way for error corrections.

The precise delivery of materials onto graphene is important for nano-processing but little is known about the mechanisms of such processes. Here, the authors use a range of microscopic techniques for the real-time observation of nanoparticle transfer from the inner channel of a carbon nanotube onto graphene.

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.

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 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.

Solvent substitution: an analysis of comprehensive hazard screening indices

The air index (ψ(i)(air)) of the PARIS II software (Environmental Protection Agency), the Indiana Relative Chemical Hazard Score (IRCHS), and the Final Hazard Score (FHS) used in the P2OASys system (Toxics Use Reduction Institute) are comprehensive hazard screening indices that can be used in solvent substitution. The objective of this study was to evaluate these indices using a list of 67 commonly used or recommended solvents. The indices ψ(i)(air), IRCHS and FHS were calculated considering 9, 13, and 33 parameters, respectively, that summarized health and safety hazards, and environmental impacts. Correlation and sensitivity analyses were performed. The vapor hazard ratio (VHR) was used as a reference point. Two good correlations were found: (1) between VHR and ψ(i)(air) (ρ = 0.84), (2) and between IRCHS and FHS (ρ = 0.81). Values of sensitivity ratios above 0.2 were found with ψ(i)(air) (4 of 9 parameters) and IRCHS (3 of 13 parameters), but not with FHS. Overall, the three indices exhibited important differences in the way they integrate key substitution factors, such as volatility, occupational exposure limit, skin exposure, flammability, carcinogenicity, photochemical oxidation potential, atmospheric global effects, and environmental terrestrial and aquatic effects. These differences can result in different choices of alternatives between indices, including the VHR. IRCHS and FHS are the most comprehensive indices but are very tedious and complex to use and lack sensitivity to several solvent-specific parameters. The index ψ(i)(air) is simpler to calculate but does not cover some parameters important to solvents. There is presently no suitably comprehensive tool available for the substitution of solvents. A two-tier approach for the selection of solvents is recommended to avoid errors that could be made using only a global index or the consideration of the simple VHR. As a first tier, one would eliminate solvent candidates having crucial impacts. As a second tier, other parameters would be considered, with emphasis on the VHR.

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.

Monte Carlo simulation to reconstruct formaldehyde exposure levels from summary parameters reported in the literature

OBJECTIVES

This study presents a procedure allowing the numerical synthesis of exposure data reported in different ways in the literature, including summary parameters and single measurements. The procedure was applied to literature regarding formaldehyde exposure in the reconstituted wood panels industry, including oriented-strand board (OSB), medium density fibre board (MDF) and particle board (PB).

METHODS

For each publication providing summary parameters we estimated geometric means (GM) and geometric standard deviations (GSD) by assuming lognormality of exposure levels. Monte Carlo simulation was performed to re-create datasets from the sample sizes and estimated GMs and GSDs, allowing their subsequent formatting together with the single measurements. The precision and bias of the methods used to estimate GMs and GSDs were evaluated.

RESULTS

Altogether, the 13 articles included in our study yielded a final database of 874 data, of which 732 were simulated. For both area and personal data, exposures corresponding to MDF and PB were similar while OSB levels were lower. The most recent available personal levels (1985-1994) were highest in PB for jobs performed in the vicinity of the press (GM=0.63 mg m-3). Corresponding area levels were highest for PB in the main production zone (GM=0.43 mg m-3). Mixed-effects models fitted to area PB data explained 38% of the total variability. A 6-fold decrease in exposures from 1965 to 1995 was estimated. Replication of the simulation process yielded relative standard deviations of the calculated GMs and GSDs between 10 and 20%. The relative biases of the methods used to estimate GMs and GSDs varied across methods and decreased with higher sample sizes (from approximately 15% for n=5 to less than 5% for n=30, in absolute value). The precision also varied across methods and improved with higher sample sizes (from approximately 30% for n=5 to approximately 10% for n=30).

DISCUSSION

This methodology constitutes a new meta-analysis tool that should improve the interpretation of industrial hygiene literature data, but needs to be further validated.

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.

Laryngeal and hypopharyngeal cancers and occupational exposure to formaldehyde and various dusts: a case-control study in France

OBJECTIVES

A case-control study was conducted in France to assess possible associations between occupational exposures and squamous cell carcinomas of the larynx and hypopharynx.

METHODS

The study was restricted to men, and included 201 hypopharyngeal cancers, 296 laryngeal cancers, and 296 controls (patients with other tumour sites). Detailed information on smoking, alcohol consumption, and lifetime occupational history was collected. Occupational exposure to seven substances (formaldehyde, leather dust, wood dust, flour dust, coal dust, silica dust, and textile dust) was assessed with a job exposure matrix. Exposure variables used in the analysis were probability, duration, and cumulative level of exposure. Odds ratios (ORs) with their 95% confidence intervals (95% CIs) were estimated by unconditional logistic regression, and were adjusted for major confounding factors (age, smoking, alcohol, and when relevant other occupational exposures).

RESULTS

Hypopharyngeal cancer was found to be associated with exposure to coal dust (OR 2.31, 95% CI 1.21 to 4.40), with a significant rise in risk with probability (p<0.005 for trend) and level (p<0.007 for trend) of exposure. Exposure to coal dust was also associated with an increased risk of laryngeal cancer (OR 1.67, 95% CI 0.92 to 3.02), but no dose-response pattern was found. A significant relation, limited to hypopharyngeal cancer, was found with the probability of exposure to formaldehyde (p<0.005 for trend), with a fourfold risk for the highest category (OR 3.78, 95% CI 1.50 to 9.49). When subjects exposed to formaldehyde with a low probability were excluded, the risk also increased with duration (p<0.04) and cumulative level of exposure (p<0.14). No significant association was found for any other substance.

CONCLUSION

These results indicate that exposure to formaldehyde and coal dust may increase the risk of hypopharyngeal cancer.

A study on the substitution of trichloroethylene as a spot remover in the textile industry

Since the ban on 1,1,1-trichloroethane, the textile industry has been using trichloroethylene (TCE) as a spot remover to clean oil and grease stains from fabrics at inspection stations. TCE is a toxic substance recently classified as a probable human carcinogen. The purpose of this study was to use a systematic substitution procedure to replace TCE with a less hazardous option for spot removing in a textile company. After documenting the problem and understanding the processes involved, numerous sources of information were searched to identify the greatest number of plausible solutions. Then criteria were established to help consider only the options that seemed technically acceptable. Five options were retained: 1-bromopropane, a petroleum-based solvent, a hydrochlorofluorocarbon-based solvent, an appliance that uses hot steam, and the elimination of the oil and grease spots at the source. The latter option, which had been partially implemented by the textile company, was not considered in this study. After being tested in the workplace and evaluated on their technical plausibility and impact on health, safety, and environment, the remaining four options were not considered as suitable replacements for TCE. Thus, local ventilation with the implementation of further measures for the reduction/elimination of stains at the source were recommended to lower TCE exposure for workers.

Sinonasal cancer, occupation, and tobacco smoking in European women and men

BACKGROUND

In this analysis of European case-control studies on sinonasal cancer, we examined the risk for occupation and smoking, by gender and histological type.

METHODS

The pooled data included 104 female and 451 male cases, and 241 female and 1,464 male controls. Lifetime smoking and occupational history were recoded following uniform criteria, and job-exposure matrices were applied for wood and leather dust.

RESULTS

Wood dust exposure was associated with an excess risk in men (OR = 2.36, 95% CI 1.75-3.2) but not in women (OR = 1.17, 95% CI 0.31-4.47). Exposure to leather dust was associated with an excess risk in both genders. Both wood and leather dust were associated with adenocarcinomas rather than squamous cell carcinomas. Excess risks for smoking were higher for squamous cell carcinomas and higher in men than in women.

CONCLUSIONS

In these European populations, occupation was associated with about 11% of all sinonasal cancers in women and 39% in men. This difference can, in part, be attributed to variation in exposure patterns between genders.

A study of ethylene glycol exposure and kidney function of aircraft de-icing workers

Ethylene glycol levels were measured in 154 breathing zone air samples and in 117 urine samples of 33 aviation workers exposed to de-icing fluid (basket operators, de-icing truck drivers, leads and coordinators) studied during 42 worker-days over a winter period of 2 months at a Montreal airport. Ethylene glycol as vapour did not exceed 22 mg/m3 (mean duration of samples 50 min). Mist was quantified at higher levels in 3 samples concerning 1 coordinator and 2 basket operators (76-190 mg/m3, 45-118 min). In 16 cases workers' post-shift or next-morning urine contained quantities of ethylene glycol exceeding 5 mmol/mol creatinine (up to 129 mmol/mol creatinine), with most of these instances occurring in basket operators and coordinators, some of whom did not wear paper masks and/or were accidentally sprayed with de-icing fluid. Diethylene glycol was also found in a few air and urinary samples at levels around one tenth those of ethylene glycol. Urinary concentrations of albumin, beta-N-acetyl-glucosaminidase, beta-2-microglobulin and retinol-binding protein were measured and compared over various periods, according to subgroups based on exposure level and according to the frequency of extreme values. These analyses did not demonstrate acute or chronic kidney damage that could be attributed to working in the presence of ethylene glycol. In conclusion, this study does not suggest important health effects of exposure to de-icing fluid in this group of workers. Potential for overexposure exists, however, in certain work situations, and recommendations on preventive measures are given. In addition, these results suggest that other routes of absorption than inhalation, such as the percutaneous route, may be important and that urinary ethylene glycol may be a useful indicator of exposure to ethylene glycol.

Occupational and environmental exposure of garage workers and taxi drivers to airborne manganese arising from the use of methylcyclopentadienyl manganese tricarbonyl in unleaded gasoline

Occupational and environmental exposure to airborne manganese has been measured for two groups of workers in Montreal, taxi drivers and garage mechanics. In Canada methylcyclopentadienyl manganese tricarbonyl (MMT) has replaced lead as an anti-knock agent in gasoline and represents a potentially important source of manganese contamination for the population in general and for the two chosen groups of workers in particular. Twenty workers (10 taxi drivers and 10 garage mechanics) wore a personal air sampler for five consecutive working days and two off-work periods. The amount of total Mn on each filter was determined by neutron activation analysis and then converted to atmospheric Mn concentrations. The values obtained varied from 0.004 microgram m-3 to 2.067 micrograms m-3. At work the garage mechanics were exposed to an average of 0.250 microgram m-3 and the taxi drivers to 0.024 microgram m-3. Off-work, the two groups were exposed respectively to an average of 0.007 microgram m-3 and 0.011 microgram m-3. In the garages there was twice as much Mn in the air on days when the doors were closed compared to days when they were left opened (0.314 micrograms m-3/0.152 microgram m-3). The levels found in this study remain well below the established limits for occupational and environmental airborne exposure. These results will lead to further studies to positively identify the source of Mn as MMT and to explore other pathways leading to the contamination of the general population.

Mediation by the androgen receptor of the stimulatory and antiandrogenic actions of 17 beta-estradiol on the growth of androgen-sensitive Shionogi mammary carcinoma cells in culture

Increasing concentrations of 17 beta-estradiol (E2) led to a maximal 7-fold stimulation of growth of the highly androgen-sensitive clone (SEM-1) of the mammary carcinoma Shionogi cell line. Half-maximal stimulation by the estrogen was observed at 100 nM E2. Diethylstilbestrol (DES), on the other hand, a synthetic estrogen with no affinity for the androgen receptor, had no significant stimulatory effect on cell growth but caused growth inhibition at concentrations above 1 microM. Mediation of the action of E2 by the androgen receptor is indicated by the absence of interference of E2 action by the antiestrogen LY156758 while the antiandrogen hydroxyflutamide (3 microM) caused a 50% inhibition of E2 action. While increasing concentrations of E2 led to a progressive increase in cell growth, a progressive shift in the ED50 value of action of dihydrotestosterone (DHT) was observed at intermediate (10-100 nM) concentrations of E2 while 10 microM E2 completely inhibited DHT action. At those high E2 concentrations, however, E2 itself led to a stimulation of cell growth equivalent to approximately 50% of the maximal value achieved by DHT. E2 competed with the specific uptake of [3H]testosterone in intact cells at an inhibition constant (Ki) value of 15 nM, thus indicating direct interaction of E2 with the androgen receptor. Preincubation with E2 had no influence on the apparent affinity of testosterone for the androgen receptor nor on the number of androgen binding sites. The present data demonstrate that both the stimulatory and antiandrogenic action of E2 on the growth of the androgen-sensitive mammary carcinoma cell line SEM-1 are mediated through direct interaction of the estrogen with the androgen receptor. Such data may offer an explanation for the subjective improvements reported in prostate cancer patients receiving a high dose of E2 when relapsing after castration.

Adrenal precursor C19 steroids are potent stimulators of growth of androgen-sensitive mouse mammary carcinoma Shionogi cells in vitro

Since there is convincing evidence for a role of adrenal steroids as precursors of active sex steroids in peripheral tissues, especially prostate cancer, we have studied the effect of the four main adrenal steroids, namely dehydroepiandrosterone sulfate (DHEA-S), DHEA, 5-androstene-3 beta,17 beta-diol (delta 5-diol) and 4-androstene-3,17-dione (delta 4-dione) on the growth of an androgen-sensitive clone (SEM-1) of the mouse mammary carcinoma Shionogi. From a control doubling time of 6.69 +/- 0.03 days, 0.1 microM DHT, 1.0 microM delta 4-dione, 10 microM delta 5-diol, 10 microM DHEA-S and 10 microM DHEA decreased generation time to 1.60 +/- 0.01, 1.69 +/- 0.01, 1.95 +/- 0.01, 4.37 +/- 0.02 and 5.66 +/- 0.03 days, respectively (P less than 0.01 vs. control). The same compounds exerted their stimulatory effects on cell growth at the following ED50 values: 0.06 nM, 16 nM, 90 nM, 150 nM and 16 microM for DHT, delta 4-dione, DHEA, delta 5-diol and DHEA-S, respectively. The stimulatory effect of all compounds was inhibited in a competitive manner by the pure antiandrogen hydroxyflutamide. Further evidence for an action of the adrenal steroids through the androgen receptor is indicated by competition of [3H]testosterone uptake in the tumor cells at the following IC50 values: 0.21 nM, 0.63 nM, 50 nM, 75 nM and 680 nM for DHT, testosterone, delta 4-dione, delta 5-diol and DHEA, respectively. The present data show that the four main adrenal steroids present in the serum of adult men can exert potent stimulatory effects on the growth of an androgen-sensitive cancer cell line through an androgen receptor-mediated mechanism.

Smoking and degree of occupational exposure: are internal analyses in cohort studies likely to be confounded by smoking status?

Occupational cohort studies are usually carried out without the benefit of information on smoking habits of cohort members. One common approach to avoid confounding bias related to smoking habits is to carry out an internal analysis, comparing workers with different degrees of occupational exposure. The premise behind this approach is that within a cohort there is unlikely to be correlation between degree of exposure and smoking habits. If this were untrue, smoking could confound the disease-exposure relationships. Our purpose was to verify the premise. The study sample consisted of 857 French-Canadian men born between 1910 and 1930, with 11 or fewer years of education, and interviewed around 1980 in the context of an occupational cancer case-control study. For each man we had information on smoking habits, job history, and a history of the chemicals he was exposed to in each of his jobs. We computed two indices of the dirtiness of workers' job histories: one based on the job titles held by the man and a second based on the degree of exposures to workplace substances. There was no correlation between these indices of job dirtiness and smoking history. We also examined the smoking-exposure relationship among the subsets of men who had been occupationally exposed to ten especially noticeable substances. Within the subsets, there was no indication of a consistent difference among the smoking subgroups in level or duration of exposure to these index substances. These findings do not support the view that nonsmokers sought out cleaner job environments than smokers; they imply that internal analyses of "dose-response" in cohort studies are unlikely to be seriously confounded by smoking habits.

Combination therapy in stage C and D prostatic cancer: rationale and five year clinical experience

In 1941, Huggins and his colleagues discovered that testicular androgens exert a stimulatory effect on prostate cancer growth. Our group has made the key observations that the human adrenals, in addition to the tests, also secrete important amounts of androgens and cancer cells exhibit a marked heterogeneity of androgen sensitivity. In fact, human adrenals secrete large amounts of precursor steroids that are converted into active androgens in peripheral tissues (including the prostate), thus providing 40% to 50% of total androgens in adult men. The action of these androgens remaining after castration can be inhibited in prostatic cancer tissue by administering a pure antiandrogen that also decreases the local concentration of dihydrotestosterone (DHT). The castration levels of serum testosterone left in men after castration have an important stimulatory activity on the growth of androgen-sensitive normal as well as cancer tissues. Cancer cells have markedly different requirements for androgens. Some cell clones can grow in the presence of minimal amounts of androgens, requiring more complete androgen blockade and more potent antiandrogens for inhibiting growth. Among the compounds recommended as antiandrogens, the most unexpected finding is that many of them are devoid of any antiandrogenic activity. In fact, medroxyprogesterone acetate, chlormadinone acetate, and megestrol acetate have androgenic activity, but do not inhibit the peripheral action of DHT in prostatic tissue. These compounds should not be classified as antiandrogens. Cyproterone acetate, on the other hand, is a mixed agonist-antagonist. The only compounds showing pure antiandrogenic activity are Flutamide and its analogues. There is thus a need for a more complete blockade of androgens of both testicular and adrenal origins in order to exert a maximal inhibitory effect on cancer growth. We have therefore performed clinical studies in previously untreated stage D2 and C prostate cancer patients with the combination therapy using the LHRH agonist [D-Trp6, des Gly NH2(10)] LHRH ethylamide and the antiandrogen Flutamide. There was a significant increase in patients with a complete response, as compared with studies limited to the removal or blockade of testicular androgens. There was also a significant decrease in the number of non-responders, an increased duration of positive response, and a decrease in the death rate. This was achieved with minimal or no side effects, thus preserving a good quality of life.

Obtaining occupational exposure histories in epidemiologic case-control studies

In a large population-based case-control study designed to generate hypotheses regarding possible associations between cancer sites and occupational exposures, an innovative methodology is utilized to infer the subjects' chemical exposures. It features (1) a probing interview to obtain a detailed portrait of each job the subject has held, (2) exposure coding by a team of chemists and hygienists who review each interview, (3) a coding checklist of nearly 300 occupational exposures including the most common ones, and (4) indication by the coders of the level, frequency, and mode of exposure, as well as of their degree of confidence that the exposure occurred. In making coding decisions, the chemists draw upon their experience and upon consultants and bibliographic sources. Resultant data can be combined to produce a variety of semi-quantitative indices of exposure for epidemiologic analyses.