Standardized risk assessment plays an important role in providing medical care of uniform quality to pregnant women, even though it is not a substitute for clinical judgement. This study was designed to determine whether the antepartum risk score currently used across Alberta is associated with neonatal morbidity and adverse pregnancy outcomes for singleton live births and to examine whether the current classification of "lower risk" pregnancies (score
The International Agency for Research on Cancer classifies specific polycyclic aromatic hydrocarbons (PAHs) as probable carcinogens. This study compares two PAH biomarkers and their relationship with geographic information system (GIS) based traffic density (a proxy of PAH exposure), and explores the determinants of the PAH biomarkers.
A cross-sectional study was conducted in Montreal with 200 volunteers (107 females and 93 males) ages 20 to 53 years. Data were collected by questionnaire, urine samples were used for biomarker analysis, and innovative GIS-based time- and distance-weighted traffic densities (TDWTD) were calculated for all locations of participants during the 48 h prior to urine collection.
Detection rates of the two biomarkers were greater than 95%. Female participants had higher 1-OHP and 1-OHPG levels than males, and no relationship was detected between TDWTD in 48 h and the two PAH biomarkers. Biomarker levels were related to smoking more than one pack of cigarettes in the previous 48 h, and among non-smokers, barbecued meat consumption increased the level of urinary 1-OHP (exp ß: 1.45, 95% CI: 1.07 to 1.98).
Both 1-OHP and 1-OHPG can be used to assess the relatively low PAH levels to which the general population is exposed. With the exception of smoking, the impact of PAH exposure factors on the biomarkers is relatively small in this study population.
Autism spectrum disorders (ASD) are associated with complications of pregnancy that implicate fetal hypoxia (FH); the excess of ASD in male gender is poorly understood. We tested the hypothesis that risk of ASD is related to fetal hypoxia and investigated whether this effect is greater among males.
Provincial delivery records (PDR) identified the cohort of all 218,890 singleton live births in the province of Alberta, Canada, between 01-01-98 and 12-31-04. These were followed-up for ASD via ICD-9 diagnostic codes assigned by physician billing until 03-31-08. Maternal and obstetric risk factors, including FH determined from blood tests of acidity (pH), were extracted from PDR. The binary FH status was missing in approximately half of subjects. Assuming that characteristics of mothers and pregnancies would be correlated with FH, we used an Estimation-Maximization algorithm to estimate HF-ASD association, allowing for both missing-at-random (MAR) and specific not-missing-at-random (NMAR) mechanisms.
Data indicated that there was excess risk of ASD among males who were hypoxic at birth, not materially affected by adjustment for potential confounding due to birth year and socio-economic status: OR 1.13, 95%CI: 0.96, 1.33 (MAR assumption). Limiting analysis to full-term males, the adjusted OR under specific NMAR assumptions spanned 95%CI of 1.0 to 1.6.
Our results are consistent with a weak effect of fetal hypoxia on risk of ASD among males. E-M algorithm is an efficient and flexible tool for modeling missing data in the studied setting.
To characterize exposures of asphalt workers in Norway and to evaluate exposure control measures.
Representative asphalt paving and mixing operations were monitored in Norway in 1991-92 for exposures to bitumen fume, organic vapor, polycyclic aromatic hydrocarbons (PAHs) and vehicle exhaust (NO2, CO). Linear regression was used to evaluate introduced control measures.
A total of 320 samples of airborne organic matter were gathered (279 from paving). Median personal bitumen fume measurements ranged from 0.03 to 0.15 mg/m3 and were similar in paving and asphalt mixing. According to principal component analysis, there were three independent sets of PAHs: (i) PAHs lighter than 228 g/mol; (ii) 4- to 6-ring PAHs non-detectable in 80-90% of samples; and (iii) naphthalene. Some NO2 (1/49) and CO (12/58) concentrations near paving equipment exceeded 15 min exposure limits, 2 and 25 p.p.m., respectively. Changing sampling methods midway through the study had a significant impact on the measured bitumen fume and organic vapor levels. For pavers, lower application temperatures reduced organic vapor, but not bitumen fume, exposures. Retrofitting a paving machine produced at least a 5-fold reduction in exposure to airborne organic matter. Work in tunnels increased PAH exposures, but general ventilation partially counteracted this effect.
The observed exposure levels indicate that some potentially hazardous exposures may have occurred during paving in Norway. Bitumen fume, organic vapor and PAH exposures can be reduced using appropriate engineering control measures.
Our objective was to characterize the association between body mass index (BMI) and childhood asthma while adjusting for individual and neighborhood socioeconomic factors. Data were obtained from 3,804 students 10 to 11 years of age in Nova Scotia, Canada. Asthma was defined as parent-reported doctor-diagnosed asthma or bronchitis. Smoothed curves suggested a linear association between BMI and asthma with a 6 % increase in prevalence per unit increase of BMI. This association was independent of allergies, sex, and socioeconomic factors. Girls from socioeconomically disadvantaged neighborhoods were less likely to be asthmatic as were boys from well-educated and wealthy families.
OBJECTIVES: The aim of the study was to investigate cancer risk following employment in the asphalt industry. METHODS :Cancer incidence was studied among 22 362 male asphalt workers employed for more than one season in jobs entailing exposure to bitumen (mainly road pavers) in Denmark, Finland, Norway, and Sweden. These workers are part of a European cohort of asphalt workers, for which results on mortality have been reported. The follow-up was almost complete, and reference rates were obtained from national cancer registries. RESULTS: The incidence of cancer was reduced in all four countries [overall standardized incidence ratio (SIR) 0.89, 95% confidence interval (95% CI) 0.86-0.94]. Lung cancer incidence was increased in all four countries, yielding an overall SIR of 1.21 (95% CI 1.07-1.36), but no trend was detected according to time since first employment. No overall increased incidence of bladder cancer was observed, but there was a suggestion of a tendency towards higher risk with longer time since first employment, with a relative risk of 1.85 (95% CI 0.90-3.78) for more than 30 years versus 1-14 years (P-value for trend 0.1). The incidence of lip and stomach cancer was nonsignificantly increased, and the excess was present mainly in Denmark. No increased incidence was detected for other neoplasms, notably malignant melanoma, nonmelanoma skin cancer, and kidney cancer. CONCLUSIONS: The results of this study confirm the pattern of cancer risk detected in the mortality analysis of the European cohort; in addition, they provide suggestive evidence of an excess risk of bladder cancer among asphalt workers.
Comment In: Scand J Work Environ Health. 2004 Oct;30(5):337-815529796
BACKGROUND: An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses. METHODS: In a multi-country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953-2000. Exposures to bitumen fume, coal tar, 4-6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job-exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated. RESULTS: The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99-1.18) was comparable to that of non-exposed workers (SMR 1.05, 95% CI 0.92-1.19). In a sub-cohort of bitumen-exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02-1.48). The analysis based on the semi-quantitative, matrix-based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose-response was suggested for average level of exposure, applying a 15-year lag, which was marginally reduced after adjustment for co-exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm. CONCLUSIONS: The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck.
BACKGROUND: Inhalation of bitumen fumes is potentially carcinogenic to humans. METHODS: We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow-up during 1953-2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers. RESULTS: The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90-0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04-1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89-1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89-1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers. CONCLUSIONS: European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out.
Background We conducted a nested case-control study in a cohort of European asphalt workers in which we have previously reported an increase in lung cancer risk among workers exposed to airborne bitumen fume, although potential bias and confounding were not fully addressed. Objective To investigate the contribution of exposure to bitumen, other occupational agents, and tobacco smoking, to the lung cancer risk of asphalt workers. Methods Cases were cohort members in Denmark, Finland, France, Germany, the Netherlands, Norway, and Israel who died from lung cancer between 1980 and the end of follow-up (2002-2005). Controls were individually matched to cases (3:1) on year of birth and country. Exposure estimates were derived for bitumen fume and condensate, organic vapour, PAH, as well as for asbestos, crystalline silica, diesel motor exhaust and coal tar. Odds ratios (OR) were calculated for ever exposure, duration, average and cumulative exposure, after adjusting for tobacco smoking and exposure to coal tar. Results A total of 433 cases and 1253 controls were included in the analysis. The OR for inhalation exposure to bitumen fume was 1.12 (95% CI 0.84-1.49), and for dermal exposure to bitumen condensate 1.17 (95% CI 0.88-1.56). There was no significant trend between lung cancer risk and duration, average or cumulative exposure to bitumen fume or condensate. Conclusions We found no consistent evidence of an association between indicators of either inhalation or dermal exposure to bitumen and lung cancer risk. A sizable proportion of the excess mortality from lung cancer relative to the general population observed in the earlier cohort phase is likely attributable to high tobacco consumption, and possibly to coal tar exposure, while other occupational agents do not appear to play an important role.
In epidemiological research, self-reported information about determinants and levels of occupational exposures is difficult to obtain, especially if the disease under study has a high mortality rate or follow-up has exceeded several years. In this paper, we present a semi-quantitative exposure assessment strategy for nested case-control studies of styrene exposure among workers of the Danish reinforced plastics industry when no information on job title, task or other indicators of individual exposure were readily available from cases and controls. The strategy takes advantage of the variability in styrene exposure level and styrene exposure probability across companies. The study comprised 1522 cases of selected malignancies and neurodegenerative diseases and controls employed in 230 reinforced plastics companies and other related industries. Between 1960 and 1996, 3057 measurements of styrene exposure level obtained from 191 companies, were identified. Mixed effects models were used to estimate expected styrene exposure levels by production characteristics for all companies. Styrene exposure probability within each company was estimated for all but three cases and controls from the fraction of laminators, which was reported by a sample of 945 living colleagues of the cases and controls and by employers and dealers of plastic raw materials. The estimates were validated from a subset of 427 living cases and controls that reported their own work as laminators in the industry. We computed styrene exposure scores that integrated estimated styrene exposure level and styrene exposure probability. Product (boats), process (hand and spray lamination) and calendar year period were the major determinants of styrene exposure level. Within-company styrene exposure variability increased by calendar year and was accounted for when computing the styrene exposure scores. Exposure probability estimates based on colleagues' reports showed the highest predictive values in the validation test, which also indicated that up to 67% of the workers were correctly classified into a styrene-exposed job. Styrene exposure scores declined about 10-fold from the 1960s-1990s. This exposure assessment approach may be justified in other industries, and especially in industries dominated by small companies with simple exposure conditions.