Maternal occupational noise exposure during pregnancy and children's early language acquisition.

INTRODUCTION: Noise exposure during pregnancy may affect a child's auditory system, which may disturb fetal learning and language development. We examined the impact of occupational noise exposure during pregnancy on children's language acquisition at the age of one. METHODS: A cohort study was conducted among women working in the food industry, as kindergarten teachers, musicians, dental nurses, or pharmacists who had a child aged <1 year. The analyses covered 408 mother-child pairs. Language acquisition was measured using the Infant-Toddler Checklist. An occupational hygienist assessed noise exposure individually as no (N = 180), low (70-78 dB; N = 108) or moderate/high exposure (>79 dB; N = 120). RESULTS: Among the boys, the adjusted mean differences in language acquisition scores were -0.4 (95% CI -2.5, 1.8) for low, and -0.7 (95% CI -2.9, 1.4) for moderate/high exposure compared to no exposure. Among the girls the respective scores were +0.1 (95% CI -2.2, 2.5) and -0.1 (95% CI -2.3, 2.2). Among the children of kindergarten teachers, who were mainly exposed to human noise, low or moderate exposure was associated with lower language acquisition scores. The adjusted mean differences were -3.8 (95% CI -7.2, -0.4) for low and -4.9 (95% CI -8.6, -1.2) for moderate exposure. CONCLUSIONS: In general, we did not detect an association between maternal noise exposure and children's language acquisition among one-year-old children. However, the children of kindergarten teachers exposed to human noise had lower language acquisition scores than the children of the non-exposed participants. These suggestive findings merit further investigation by level and type of exposure.

Work-Related Outcomes in Self-Employed Cancer Survivors: A European Multi-country Study.

Purpose To describe: (i) patterns of self-employment and social welfare provisions for self-employed and salaried workers in several European countries; (ii) work-related outcomes after cancer in self-employed people and to compare these with the work-related outcomes of salaried survivors within each sample; and (iii) work-related outcomes for self-employed cancer survivors across countries. Methods Data from 11 samples from seven European countries were included. All samples had cross-sectional survey data on work outcomes in self-employed and salaried cancer survivors who were working at time of diagnosis (n = 22-261 self-employed/101-1871 salaried). The samples included different cancers and assessed different outcomes at different times post-diagnosis. Results Fewer self-employed cancer survivors took time off work due to cancer compared to salaried survivors. More self-employed than salaried survivors worked post-diagnosis in almost all countries. Among those working at the time of survey, self-employed survivors had made a larger reduction in working hours compared to pre-diagnosis, but they still worked more hours per week post-diagnosis than salaried survivors. The self-employed had received less financial compensation when absent from work post-cancer, and more self-employed, than salaried, survivors reported a negative financial change due to the cancer. There were differences between self-employed and salaried survivors in physical job demands, work ability and quality-of-life but the direction and magnitude of the differences differed across countries. Conclusion Despite sample differences, self-employed survivors more often continued working during treatment and had, in general, worse financial outcomes than salaried cancer survivors. Other work-related outcomes differed in different directions across countries.

Paternal occupational lead exposure and offspring risks for schizophrenia.

This register-based cohort study investigated whether paternal occupational exposure to inorganic lead was related to offspring risk for schizophrenia spectrum disorder (SSD). Exposed men (n=11,863) were identified from blood lead measurements taken at the Finnish Institute of Occupational Health in 1973-1983. Data on mothers and their offspring born from 1972-1984 were obtained from the national Population Information System. Two population comparison offspring for each exposed offspring were matched on date of birth, sex and area (n=23,720). SSD cases were identified from The Finnish Hospital Discharge Register. Hazard ratios of SSD between exposed groups were analyzed using conditional proportional hazards regression, adjusted for parental history of psychoses, parental ages, language of offspring, father's employment, and father's self-employment. After 26-38years of follow up, there were no significant differences in the incidence of schizophrenia, either between the offspring of exposed (188/11,863; 1.6%) and unexposed fathers (347/23,720; 1.5%) or based on blood lead levels (adjusted hazard ratios (aHR): 0.97, CI 0.52-1.83, 1.25, CI 0.85-1.82, 0.90, CI 0.54-1.49, and 1.38, CI 0.65-2.92 for lead categories <0.5, 0.5-0.9, 1.0-1.4, and ≥1.5µmol/L, respectively, as compared to population comparison). Parental psychosis, paternal age and offspring language were associated with offspring risk. The findings suggest that paternal exposure to lead is not a risk factor for schizophrenia in offspring. However, the majority of exposed fathers had low-level exposure, and we cannot exclude the possibility of an effect for higher exposures to lead.

Psychosocial factors at work and obesity among young finnish adults: a cohort study.

OBJECTIVE: To examine the associations between occupational psychosocial factors and obesity among 31-year-olds, adjusting for adolescent body mass index, physical strenuousness of work, and adverse health behaviors (ie, stress-related eating/drinking, leisure-time physical inactivity, smoking, and high alcohol consumption). METHODS: The study population comprised 2083 men and 1770 women from the Northern Finland Birth Cohort 1966. Obesity was defined as a body mass index of 30.0 kg/m or more. Psychosocial exposures were defined in terms of demands, control, and social support at work. RESULTS: Among men, high job demands and low worksite social support were independently associated with obesity. Among women, stress-related eating/drinking and physical inactivity seemed to promote obesity. Body mass index at age 14 was an important predictor of obesity for both sexes. CONCLUSIONS: In workplace obesity prevention programs, it might be beneficial to improve the psychosocial work environment and promote healthy behaviors simultaneously.

Selection bias due to parity-conditioning in studies of time trends in fertility.

BACKGROUND: Studies of couple fertility over time have often examined study populations with broad age ranges at a cross-section of time. An increase in fertility has been observed in studies that followed episodes of fertility events either prospectively among nulliparous women or retrospectively among parous women. Fertility has a biological effect on parity. If defined at a cross-section of time, parity will also be affected by year of birth, and thus becomes a collider. Conditioning (stratifying, restricting, or adjusting) on a collider may cause selection bias in the studied association. METHODS: A study with prospective follow-up was taken as the model to assess the validity of fertility studies. We demonstrate the potential for selection bias using causal graphs and nationwide birth statistics and other demographic data. We tested the existence of parity-conditioning bias in data including both parous and nulliparous women. We also used a simulation approach to assess the strength of the bias in populations with prior at-risk cycles. Finally, we evaluated the potential for selection bias due to conditioning on parity in various sampling frames. RESULTS: Analyses indicate that the observed increase in fertility over time can be entirely explained by selection bias due to parity-conditioning. CONCLUSION: Heterogeneity in fertility and differential success in prior at-risk cycles are the ultimate factors behind the selection bias. The potential for selection bias due to parity-conditioning varies by sampling frame. A prospective multidecade study with representative sampling of birth cohorts and follow-up from menarche to menopause would bypass the described bias.

Risk of schizophrenia and minority status: a comparison of the Swedish-speaking minority and the Finnish-speaking majority in Finland.

Approximately five percent of the Finnish population are Swedish-speaking and have higher socioeconomic position and longer life expectancy than the Finnish-speaking majority. Previous studies have not investigated whether Swedish-speaking Finns have lower risk of schizophrenia spectrum disorders (SSD) than Finnish-speaking Finns. We investigated this in a representative sample of 47 445 Finns born in 1972-1984. Hazard ratios of SSD between language groups were assessed with conditional proportional hazards regression. Sex, parental ages at birth, paternal employment around conception, parental psychosis and place and residence in the capital area were used as other explanatory variables. The prevalence of SSD was 0.7% in the Swedish-speaking minority and 1.5% in the Finnish-speaking majority. In the adjusted regression model, belonging to the Swedish-speaking minority was associated with lower risk of SSD (hazard ratio (HR) 0.41, 95% confidence interval (CI) 0.24-0.69). In a subset analysis by gender, the protective effect was evident among Swedish-speaking males (HR 0.32, 95% CI 0.15-0.68) but marginal in females (HR 0.75, 95% CI 0.41-1.37). Parental psychosis and place of birth in the capital area were associated with higher risk of SSD, whereas paternal employment at the time of conception was associated with lower risk of SSD. Our results support the role of social factors in the etiology of schizophrenia. Belonging to a minority with high socioeconomic status and social capital may be protective against schizophrenia, especially for males.

Increased risk of human parvovirus B19 infection in day-care employees: a cohort study among pregnant workers during an epidemic in Finland.

BACKGROUND: Human parvovirus B19 (B19V) infection during early pregnancy increases the risk of miscarriage. Studies have inconsistently shown an elevated risk of infection among women with occupational contacts with children. Methodological differences, particularly in defining occupational exposure and in the type of reference group, may explain the conflicting findings. METHODS: This cohort study compared B19V infections in pregnant day-care employees and healthcare professionals during a B19V epidemic in Finland. Women were identified from the files of nationwide trade unions and the National Supervisory Authority for Welfare and Health. Early-pregnancy maternal B19V IgG was analysed in 3710 women, and infections were defined as seroconversions after analysing in parallel the available umbilical cord blood samples of the 847 seronegative mothers. Independently of the serological status, the actual employment during pregnancy was assessed using registered information on employment history. RESULTS: B19V infections were more common among day-care employees (22/331, 6.6%), than among those working in healthcare (12/326, 3.7%). The adjusted HRs of B19V infection, using proportional hazard regression, was 2.63 (95% CI 1.27 to 5.46) among all women and 5.59 (95% CI 1.40 to 22.4) among nulliparous women. CONCLUSIONS: Day-care employees are at an increased risk of B19V infection, which warrants preventive measures.

Employment participation and work experience of male cancer survivors: a NOCWO study.

OBJECTIVE: To investigate whether employment status and work experiences, assessed in terms of job resources (organizational culture and superiors' and co-workers' support), commitment to organization, work motives, and experiences of discrimination, differ between survivors of prostate or testicular cancer or lymphoma and cancer-free reference subjects. METHODS: Questionnaires were sent to 1349 male cancer survivors and 2666 referents in Denmark, Finland, Iceland, and Norway. Valid responses were 59% and 45%, respectively. Odds ratios (OR) and 95% confidence intervals (CI) were estimated with logistic regression models. RESULTS: Compared to the referents, survivors of lymphoma and prostate cancer were less likely to be employed (OR=0.53; CI: 0.30-0.95 and OR=0.50; CI: 0.35-0.73, respectively), but decreased employment was not evident among testicular cancer survivors. Testicular cancer survivors experienced less discrimination at work than did the referents, for example, testicular cancer survivors were less likely to report that their colleagues doubted their ability to carry out their work tasks (OR=0.38; CI: 0.17-0.83). Lymphoma survivors were less likely than the referents to praise their workplace as an enjoyable place to work (OR=0.48; CI: 0.26-0.88). The prostate cancer survivors were more likely than the referents to find the organizational climate competitive, distrustful, and suspicious. CONCLUSIONS: Employment participation and work experiences of male cancer survivors varied substantially according to type of cancer. Occupational therapists and other health care personnel should keep this in mind when assisting cancer survivors in identifying their strengths and limitations at work.

Night-shift work and breast cancer--a systematic review and meta-analysis.

OBJECTIVE: The aim of this review was to synthesize the evidence on the potential relationship between nightshift work and breast cancer. METHODS: We searched multiple databases for studies comparing women in shift work to those with no-shift work reporting incidence of breast cancer. We calculated incremental risk ratios (RR) per five years of night-shift work and per 300 night shift increases in exposure and combined these in a random effects dose-response meta-analysis. We assessed study quality in ten domains of bias. RESULTS: We identified 16 studies: 12 case-control and 4 cohort studies. There was a 9% risk increase per five years of night-shift work exposure in case-control studies [RR 1.09, 95% confidence interval (95% CI) 1.02-1.20; I (2) = 37%, 9 studies], but not in cohort studies (RR 1.01, 95% CI 0.97-1.05; I (2) = 53%, 3 studies). Heterogeneity was significant overall (I (2) = 55%, 12 studies). Results for 300 night shifts were similar (RR 1.04, 95% CI 1.00-1.10; I (2) = 58%, 8 studies). Sensitivity analysis using exposure transformations such as cubic splines, a fixed-effect model, or including only better quality studies did not change the results. None of the 16 studies had a low risk of bias, and 6 studies had a moderate risk. CONCLUSIONS: Based on the low quality of exposure data and the difference in effect by study design, our findings indicate insufficient evidence for a link between night-shift work and breast cancer. Objective prospective exposure measurement is needed in future studies.

Exposure to tetrachloroethylene in dry cleaning shops in the Nordic countries.

OBJECTIVES: Tetrachloroethylene is the dominant solvent used in dry cleaning worldwide and many workers are potentially exposed. We report here on results of 1296 measurements of tetrachloroethylene undertaken in Nordic dry cleaning shops 1947-2001. METHODS: We searched documents and files in the Nordic institutes of occupational health for air measurements of tetrachloroethylene. Repeated measurements from the same facility during a short time interval were registered only once using the time-weighted average. We registered also changes over time in occupational exposure limits (OELs) to tetrachloroethylene. RESULTS: Only scattered measurements were available from the early years, and the exposure level seemed fairly stable up until the mid 1970s. The median exposure level was 20 p.p.m. in 1976 and decreased to 3 p.p.m. in 2000. Exposure levels in the four Nordic countries followed similar trends. In the late 1960s, the OELs varied between the Nordic countries from 30 to 100 p.p.m. Sweden was first to lower the limit, but limits gradually converged over time. At present, Denmark, Finland, and Sweden use 10 p.p.m., while Norway uses 6 p.p.m. Over time, the average observed exposure level was lower than the OEL in all countries, but in Denmark and Sweden, up to one-third of measured exposures exceeded the OEL. Overall, the stationary measurements for maintenance work showed 36 p.p.m., while the personal measurements showed 7.5 p.p.m. for dry cleaners and 6.25 p.p.m. for shop assistants. CONCLUSION: The Nordic data illustrate that it is possible over time to control chemical exposures even in an industry consisting of many small and scattered work places.

Exposure assessment for a nested case-control study of lung cancer among European asphalt workers.

OBJECTIVE: Development of a method for retrospective assessment of exposure to bitumen fume, bitumen condensate, organic vapour, polycyclic aromatic hydrocarbons, and co-exposures to known or suspected lung carcinogens for a nested case-control study of lung cancer mortality among European asphalt workers. METHODS: Company questionnaires and structured questionnaires used in interviews and industry-specific job-exposure matrices (JEMs) were elaborated and applied. Three sources of information were eventually used for exposure assessment and assignment: (i) data obtained in cohort phase, (ii) data from living subjects, next-of-kin, and fellow-workers questionnaires, and (iii) JEMs for bitumen exposure by inhalation and via skin and co-exposures to known or suspected lung carcinogens within and outside cohort companies. Inhalation and dermal exposure estimates for bitumen were adjusted for time trends, time spent in a job, and other determinants of exposure (e.g. oil gravel paving). Clothing patterns, personal protective devices, and personal hygiene were taken into consideration while estimating dermal exposure. RESULTS: Occupational exposures could be assessed for 433 cases and 1253 controls for relevant time periods. Only 43% of work histories were spent inside original asphalt and construction companies. A total of 95.8% of job periods in cohort companies could be coded at a more detailed level. Imputation of work time and 'hygienic behaviour' multipliers was needed for <10% of work history years. Overall, downward trends in exposure were present and differences existed between countries and companies. As expected, correlations were strongest (r > 0.7) among bitumen-related agents, while correlations between coal tar, bitumen-related agents, and established lung carcinogens were weaker (r < 0.4). CONCLUSIONS: A systematic and detailed approach was developed to estimate inhalation and dermal exposure for a nested case-control study among asphalt workers.

A case-control study of lung cancer nested in a cohort of European asphalt workers.

BACKGROUND: We conducted a nested case-control study in a cohort of European asphalt workers in which an increase in lung cancer risk has been reported among workers exposed to airborne bitumen fume, although potential bias and confounding were not fully addressed. OBJECTIVE: We investigated the contribution of exposure to bitumen, other occupational agents, and tobacco smoking to the risk of lung cancer among asphalt workers. METHODS: Cases were cohort members in Denmark, Finland, France, Germany, the Netherlands, Norway, and Israel who had died of lung cancer between 1980 and the end of follow-up (2002-2005). Controls were individually matched in a 3:1 ratio to cases on year of birth and country. We derived exposure estimates for bitumen fume and condensate, organic vapor, and polycyclic aromatic hydrocarbons, as well as for asbestos, crystalline silica, diesel motor exhaust, and coal tar. Odds ratios (ORs) were calculated for ever-exposure, duration, average exposure, and cumulative exposure after adjusting for tobacco smoking and exposure to coal tar. RESULTS: A total of 433 cases and 1,253 controls were included in the analysis. The OR was 1.12 [95% confidence interval (CI), 0.84-1.49] for inhalation exposure to bitumen fume and 1.17 (95% CI, 0.88-1.56) for dermal exposure to bitumen condensate. No significant trend was observed between lung cancer risk and duration, average exposure, 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, whereas other occupational agents do not appear to play an important role.

Pregnancy outcomes among daycare employees in Finland.

OBJECTIVE: The aim of this study was to investigate whether working as a daycare employee increases the risk of perinatal death, pre-term birth, low birth weight, smallness for gestational age, or congenital malformations. METHODS: We conducted a register-based cohort study among daycare employees and women from various occupations of healthcare (reference group). Study subjects were identified from the files of Finnish trade unions and the National Authority for Medicolegal Affairs. Pregnancy outcomes, antenatal occupation, and working status were obtained by linkage to national registers. The final data consisted of 13 299 and 12 182 singleton births in the study and reference groups, respectively. We analyzed pregnancy outcome data using generalized estimating equations and linear regression. RESULTS: The occurrences of pre-term birth [odds ratio (OR) 0.91, 95% confidence interval (95% CI) 0.79-1.06], perinatal death (OR 0.91, 95% CI 0.62-1.34), smallness for gestational age (OR 1.01, 95% CI 0.91-1.12), and congenital malformation (OR 1.10, 95% CI 0.92-1.32) were similar among the children of the daycare employees and the reference group. The adjusted mean birth weight of the children of the daycare employees was slightly higher (14 g, 95% CI -1-29) than that of the reference group, but the difference was attenuated to 6 g in the subset of the first births. CONCLUSION: Daycare employees were not, in general, at an increased risk of an adverse pregnancy outcome. However, efforts should nevertheless be made to prevent their exposure to harmful viruses and heavy physical load during pregnancy.

Risk of liver cancer and exposure to organic solvents and gasoline vapors among Finnish workers.

We investigated the association between exposure to various groups of solvents and gasoline vapors and liver cancer. A cohort of economically active Finns born between 1906 and 1945 was followed up during the period 1971-1995. The incident cases of primary liver cancer (n = 2474) were identified in a record linkage with the Finnish Cancer Registry. Occupations from the 1970 census were converted to exposures using a job-exposure matrix. Cumulative exposure was calculated as the product of estimated prevalence, level and duration of exposure, and we used Poisson regression to calculate the relative risks (RR). Among the occupations entailing exposure to organic solvents, an elevated liver cancer incidence was observed in male printers, and varnishers and lacquerers. Among men, the risk was increased in the highest exposure category of aromatic hydrocarbons [RR 1.77, 95% confidence interval (CI) 1.30-2.40], aliphatic/alicyclic hydrocarbons (RR 1.47, 95% CI 0.99-2.18), chlorinated hydrocarbons (RR 2.65, 95% CI 1.38-5.11) and "other solvents" (RR 2.14, 95% CI 1.23-3.71). Among women, the risk was increased for the group "other solvents" that includes mainly alcohols, ketones, esters and glycol ethers (RR 2.73, 95% CI 1.21-6.16). Our finding of an increased risk among workers exposed to chlorinated hydrocarbons is in line with several earlier studies on trichloroethylene. The results also suggest a link between exposure to other types of solvents and the risk of liver cancer. The possibility that alcohol consumption contributes to the observed risks cannot be totally excluded.

Received and needed social support at the workplace in Norwegian and Finnish stage 1 breast cancer survivors: a study from the Nordic Study Group of Cancer and Work (NOCWO).

BACKGROUND: Cross-cultural studies of comparable patients can identify differences of health care services and point to issues of possible improvement. In this cross-sectional study we compared self-reported received and needed social support at the workplace of disease-free breast cancer survivors (BCSs) stage I from Norway and Finland. METHODS: Age-matched samples of 135 BCSs from Norway and 148 from Finland were examined using a questionnaire including socio-demographic factors, employment data, measurements of social support at work from supervisors, colleagues and the occupational health service (OHS), and several other measurements. RESULTS: Finnish BCSs had significantly higher education and a higher rate of full-time employment than Norwegian ones. With adjustment for education and work time, Finnish compared to Norwegian BCSs reported significantly less received social support from supervisors, while they received significantly more social support from OHS. No differences were observed in received support from colleagues between Finnish and Norwegian BCSs. Somatic health was most strongly associated with received and needed support from supervisors, colleagues and OHS. CONCLUSIONS: The differences in received and needed social support at work observed between Norwegian and Finnish BCSs treated for stage I disease challenge strengthening of OHS for Norwegian BCSs and increased attention by supervisors in Finnish BCSs.