Maternal smoking during pregnancy and risk of stillbirth: results from a nationwide Danish register-based cohort study.

INTRODUCTION: Maternal smoking during pregnancy has been associated with an increased risk of stillbirth. Only a few studies have been conducted to determine whether smoking affects the risk of antepartum and intrapartum stillbirth differently or whether smoking cessation in early pregnancy reduces the risk. Previous results are inconclusive. We addressed these questions in a large Danish population-based cohort study. MATERIAL AND METHODS: From the Danish Medical Birth Register, we identified 841 228 singleton births in Denmark between 1997 and 2010 and gathered detailed information on maternal smoking during pregnancy and the vital status of the infant. Associations (odds ratios with 95% confidence intervals) between maternal smoking and risk of stillbirth overall and separately for antepartum and intrapartum stillbirth were analyzed using logistic regression models (generalized estimating equations), adjusting for potential confounders. RESULTS: Any smoking during pregnancy increased the risk of stillbirth, both overall (odds ratio 1.42, 95% confidence interval 1.30-1.55) and for antepartum (odds ratio 1.38, 95% confidence interval 1.25-1.53) and intrapartum (odds ratio 1.52, 95% confidence interval 1.18-1.96) stillbirths. Women who quit smoking at the beginning of the second trimester at the latest had no increased risk of stillbirth overall (odds ratio 1.03, 95% confidence interval 0.80-1.32). CONCLUSIONS: Maternal smoking during pregnancy increases the risk of stillbirth, both overall and for antepartum and intrapartum stillbirth separately. Women who quit smoking in the beginning of their pregnancy reduce their risk compared with that of non-smokers.

Maternal smoking in pregnancy and risk for congenital malformations: results of a Danish register-based cohort study.

OBJECTIVE: To examine the association between maternal smoking during pregnancy and risk for congenital malformations. DESIGN: Population-based prospective cohort study. SETTING: Denmark. POPULATION: A total of 838 265 singleton liveborn babies delivered in Denmark between 1997 and 2010 and registered in the Danish Medical Birth Register containing detailed information on smoking during pregnancy and congenital malformations. METHODS: Associations [odds ratios (OR) with 95% CI] between maternal smoking and risk for various groups of congenital malformations, investigated using the generalized estimating equation for binary outcomes, with adjustment for potential confounders. MAIN OUTCOME MEASURES: Groups of congenital malformations. RESULTS: Ever smoking during pregnancy did not increase the overall risk for congenital malformations, but increased risks were observed for multiple malformations (i.e. when two or more malformations are diagnosed in a child) (odds ratio 1.06, 95% confidence interval 1.01-1.10) and various main groups of congenital malformations including the cardiovascular system (odds ratio 1.13, 95% confidence interval 1.07-1.19), the respiratory system (odds ratio 1.25, 95% confidence interval 1.11-1.41), the digestive system (odds ratio 1.15, 95% confidence interval 1.07-1.24) and oral clefts (odds ratio 1.29, 95% confidence interval 1.14-1.46), as well as for some specific congenital malformations including cardiac septal defects, malformations of the pulmonary and tricuspid valves, malformations of the great arteries, pyloric stenosis and clubfoot. Infants of women who quit smoking during the first two trimesters had no increased risk for most groups of congenital malformations. CONCLUSIONS: Maternal smoking increases the risk for a number of congenital malformations. Future smoking cessation programs should focus on this adverse health aspect in order to encourage more women to quit smoking before or in early pregnancy.

Characterization of particle exposure during tunnel excavation by tunnel boring machines.

Tunnel boring machines (TBMs) are used to excavate tunnels in a manner where the rock is constantly penetrated with rotating cutter heads. Fine particles of the rock minerals are thereby generated. Workers on and in the vicinity of the TBM are exposed to particulate matter (PM) consisting of bedrock minerals including α-quartz. Exposure to respirable α-quartz remains a concern because of the respiratory diseases associated with this exposure. The particle size distribution of PM and α-quartz is of special importance because of its influence on adverse health effects, monitoring and control strategies as well as accurate quantification of α-quartz concentrations. The major aim of our study was therefore to investigate the particle size distribution of airborne PM and α-quartz generated during tunnel excavation using TBMs in an area dominated by gneiss, a metamorphic type of rock. Sioutas cascade impactors were used to collect personal samples on 3 separate days. The impactor fractionates the dust in 5 size fractions, from 10 µm down to below 0.25 µm. The filters were weighted, and the α-quartz concentrations were quantified using X-ray diffraction (XRD) analysis and the NIOSH 7500 method on the 5 size fractions. Other minerals were determined using Rietveld refinement XRD analysis. The size and elemental composition of individual particles were investigated by scanning electron microscopy. The majority of PM mass was collected on the first 3 stages (aerodynamic diameter = 10 to 0.5 µm) of the Sioutas cascade impactor. No observable differences were found for the size distribution of the collected PM and α-quartz for the 3 sampling days nor the various work tasks. However, the α-quartz proportion varied for the 3 sampling days demonstrating a dependence on geology. The collected α-quartz consisted of more particles with sizes below 1 µm than the calibration material, which most likely affected the accuracy of the measured respirable α-quartz concentrations. This potential systematic error is important to keep in mind when analyzing α-quartz from occupational samples. Knowledge of the particle size distribution is also important for control measures, which should target particle sizes that efficiently capture the respirable α-quartz concentration.

Occupational exposure limits for reproductive toxicants - A comparative analysis.

We investigated the level of protection of reproductive and developmental toxicity offered through occupational exposure limits (OELs) and Derived No-Effect Levels for workers' inhalation exposure (wDNELs). We compared coverage of substances that have a harmonised classification as reproductive toxicant 1 A or 1B (Repr.1 A/B), numerical values and scientific basis of 12 lists of OELs and wDNELs from REACH Registrants' and the Committee for Risk Assessment. Across the 14 sources of OELs and wDNELs, 53 % of the Repr1A/B-substances had at least one exposure limit (counting groups of metals as one entry). Registrants' wDNELs covered the largest share, 40 %. The numerical values could be highly variable for the same substance across the lists. How often reproductive toxicity is identified as the critical effect varies between the examined lists, both due to different assessments of the same substance and different substance coverage. Reviewing the margin of safety to reproductive toxicity cited in the documents, we found that 15 % of safety margins were lower to reproductive toxicity than the critical effect. To conclude, neither the REACH nor work environment legislation supply wDNELs or OELs for a substantial share of known reproductive toxicants. EU OELs cover among the fewest substances in the range, and in many cases national OELs or wDNELs are set at more conservative levels.

Narrative review of occupational exposures and noncommunicable diseases.

OBJECTIVE: Within the scope of the Exposome Project for Health and Occupational Research on applying the exposome concept to working life health, we aimed to provide a broad overview of the status of knowledge on occupational exposures and associated health effects across multiple noncommunicable diseases (NCDs) to help inform research priorities. METHODS: We conducted a narrative review of occupational risk factors that can be considered to have "consistent evidence for an association," or where there is "limited/inadequate evidence for an association" for 6 NCD groups: nonmalignant respiratory diseases; neurodegenerative diseases; cardiovascular/metabolic diseases; mental disorders; musculoskeletal diseases; and cancer. The assessment was done in expert sessions, primarily based on systematic reviews, supplemented with narrative reviews, reports, and original studies. Subsequently, knowledge gaps were identified, e.g. based on missing information on exposure-response relationships, gender differences, critical time-windows, interactions, and inadequate study quality. RESULTS: We identified over 200 occupational exposures with consistent or limited/inadequate evidence for associations with one or more of 60+ NCDs. Various exposures were identified as possible risk factors for multiple outcomes. Examples are diesel engine exhaust and cadmium, with consistent evidence for lung cancer, but limited/inadequate evidence for other cancer sites, respiratory, neurodegenerative, and cardiovascular diseases. Other examples are physically heavy work, shift work, and decision latitude/job control. For associations with limited/inadequate evidence, new studies are needed to confirm the association. For risk factors with consistent evidence, improvements in study design, exposure assessment, and case definition could lead to a better understanding of the association and help inform health-based threshold levels. CONCLUSIONS: By providing an overview of knowledge gaps in the associations between occupational exposures and their health effects, our narrative review will help setting priorities in occupational health research. Future epidemiological studies should prioritize to include large sample sizes, assess exposures prior to disease onset, and quantify exposures. Potential sources of biases and confounding need to be identified and accounted for in both original studies and systematic reviews.

Exposure to Particulate Matter and Respirable Crystalline Silica in Tunnel Construction Workers Using Tunnel Boring Machines.

OBJECTIVES: This study aimed to assess the exposure to a selection of aerosols and gases in the work environment for workers performing tunnel construction using tunnel boring machines (TBMs), to identify determinants of exposure based on the information available and to calculate robust estimates of exposure using a statistical model. The focus was particulate matter (PM) and respirable crystalline silica (RCS). In addition, concentrations of nitrogen dioxide (NO2), elemental carbon (EC), and oil mist were assessed. METHODS: Personal sampling was conducted from February 2017 to February 2019. PM in the thoracic and the respirable aerosol fractions was collected, and RCS was determined in the respirable aerosol fraction. Context information was collected on questionnaires. Because the workers could participate in the sampling more than once and multiple measurements were performed on the same date a mixed model was used in the analysis. Concentrations of PM and RCS are presented as estimated and measured geometric means (GMest and GMmea) and estimated arithmetic mean (AMest) in addition to the median. Measured concentrations of NO2, EC, and oil mist are presented as geometric means. RESULTS: A total of 290 and 289 personal samples of PM in the thoracic and respirable aerosol fractions were available for analysis, respectively. Work title/work location, type of work (production, maintenance, or a combination of the two), and date of sampling were identified as determinants of exposure. Workers in the front of the TBMs had the highest exposure to PM and RCS. The GMest of RCS exposure varied from 35 to 413 µg m-3 depending on the work title. The geometric standard deviations for measured RCS concentrations by work title ranged from 1.6 to 3.5. A total of 16 samples of NO2 and EC and 12 samples of oil mist were collected. Maximum values of NO2 and EC were 54 µg m-3 and 23 µg m-3, respectively. The maximum measured value of oil mist was 0.08 mg m-3. CONCLUSIONS: All TBM workers were exposed to PM and RCS. Exposure to RCS may be substantial, and workers in front of the TBM were exposed to the highest concentrations of both PM and RCS. A day-to-day variation was found, probably caused by differences in drilling activities. Preventive measures are warranted to keep the exposure to PM and consequently the exposure to RCS as low as possible to protect the health of workers in tunnel construction.