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Occupational noise exposure is a known risk factor for hearing loss and also adverse cardiovascular effects have been suggested. A job exposure matrix (JEM) would enable studies of noise and health on a large scale. The objective of this study was to create a quantitative JEM for occupational noise exposure assessment of the general working population. Between 2001–2003 and 2009–2010, we recruited workers from companies within the 10 industries with the highest reporting of noise-induced hearing loss according to the Danish Working Environment Authority and in addition workers of financial services and children day care to optimize the range in exposure levels. We obtained 1343 personal occupational noise dosimeter measurements among 1140 workers representing 100 different jobs according to the Danish version of the International Standard Classification of Occupations 1988 (DISCO 88). Four experts used 35 of these jobs as benchmarks and rated noise levels for the remaining 337 jobs within DISCO 88. To estimate noise levels for all 372 jobs, we included expert ratings together with sex, age, occupational class, and calendar year as fixed effects, while job and worker were included as random effects in a linear mixed regression model. The fixed effects explained 40% of the total variance: 72% of the between-jobs variance, −6% of the between-workers variance and 4% of the within-worker variance. Modelled noise levels showed a monotonic increase with increasing expert score and a 20 dB difference between the highest and lowest exposed jobs. Based on the JEM estimates, metal wheel-grinders were among the highest and finance and sales professionals among the lowest exposed. This JEM of occupational noise exposure can be used to prioritize preventive efforts of occupational noise exposure and to provide quantitative estimates of contemporary exposure levels in epidemiological studies of health effects potentially associated with noise exposure.

Poul Frost and colleagues (1) argue that the excess work disability that we observed following notification of occupational disease is small and reassuring indicating no need for major concern. We agree with respect to patients who are not at work when notified because for them we observed no increased risk of subsequent work disability. For patients, who were at work when notified, we do not agree however. For them, we observed a hazard ratio of 1.46 [95% confidence interval (95% CI) 1.17–1.82] and a risk difference of 12.5% (risk notified - risk not notified = 48.1% - 35.6%) (2). Whether an absolute risk of 12.5% is small or not depends on the comparison. One example among many is Acheson and colleagues’ seminal work on sinonasal adenocarcinoma in wood-dust-exposed Buckinghamshire furniture workers, a milestone in occupational epidemiology (3, 4). In a population of 5371, they observed 8 cases of sinonasal adenocarcinoma while the expected number was 0.06. This corresponds to a risk difference of 0.15% which is about 1/80 of that observed in our study. Had their findings been neglected because of arguments about low public health impact, we would have been denied information with immense impact on our understanding of carcinogenesis as well as the prevention of sinonasal cancer. Another way of assessing the size of the problem is by estimating the excess number in the general population. Annually, about 18 000 patients are notified of occupational disease in Denmark. If we assume that 50% are at work when notified, as in our data, this means that 1125 patients are work-disabled annually due to notification if our findings represent a causal effect (18 000 × 50% × 12.5%). This is in our opinion not a negligible number of patients even if it is expected to represent a small fraction of all work-disabled patients as only about 0.6% of the workforce is notified annually. A low population-attributable fraction is generally seen in occupational medicine because of low population exposure prevalence (5). The high prevalence of work disability in our study population indicates a multifactorial etiology that includes more and frequent causes than for sinonasal adenocarcinoma, but this should not inveigle us into neglecting individual risk factors that step by step may improve our understanding of the mechanisms behind work disability and furthermore may be amendable and thus targeted by preventive initiatives that can improve workers’ health (6). In our opinion, the major problem is thus not the magnitude of the effect we observed but how workers’ compensation systems can implement our results, bearing in mind the methodological limitations of the study and the fact that this is a delicate topic in occupational health. In a second commentary on our original research, Kuijer and colleagues (7) argue – based on Dutch experiences – that our suggestions for changing worker’s compensation might be counterproductive for preventing work disability. They refer to a national survey showing that patients who presumed that their disease was work-related and who were not notified had longer sick leave. In our opinion, this indicates that patients’ perception of work-relatedness may be an important confounder when studying the effect of notification. Because all patients included in our study were referred to our occupational medicine department explicitly because their health problems were presumed to be work-related this should, however, not have confounded our results. By the same token, the side-effect of notification that we observed should add on top of the effect associated with the mere presumption of work-relatedness. Kuijer and colleagues recommend a randomized, controlled intervention study as more appropriate than our observational design. We agree that this would have addressed the key problem of higher levels of clinical, occupational, and social characteristics, which predict a poorer vocational prognosis, among the notified patients. However, this was and is not an option due to ethical and statutory reasons. Kuijer et al recommend that occupational physicians discuss the work-relatedness of the illness with their patients, make a timely diagnosis, and provide appropriate care and intervention at the workplace to prevent work disability. We fully agree, and this is the focus of our clinical as well as our scientific work (8–10) as it should be for any occupational physician regardless of whether the patient’s disease is caused by the occupation or not, or whether the patient is notified to the compensation board or not. Our data suggest that the latter may be an important predictor of work disability. Conflicts of interest Lone Donbæk Jensen and Ane Marie Thulstrup prepare specialist’s statements for the National Board of Industrial Injuries. Vivi Schlünssen is advisor for the labor union “HK Danmark” in notification issues. Jens Peter Bonde prepares expert testimonies concerning industrial injuries for the Medico-Legal Council.

The aetiology of systemic sclerosis (Ssc) is unknown, but there is evidence of environmental factors playing a part in disease development in a number of cases. By examining a group of male patients with Ssc we found significant exposure to silica in 26% (6/23) of the patients compared to 2,1% in the general working population in Denmark. In the article we review the association between silica and Ssc and suggest how to question and refer patients with SSc who are suspected to have been exposed to silica.

Some peope react to smells or chemicals at levels far below toxicological thresholds with nonspecific symptoms, fear and social isolation. They may be diagnosed with multiple chemical sensitivity. There is no empirical evidence indicating that this condition is explained by toxicological mechanisms, even though a number of theories have been proposed. The authors of this review conclude that this is a functional condition. These patients need information and treatment in accordance with this fact. Instead of being advised how to avoid exposure to chemicals, they should be properly trained in appropriate confrontation with the chemicals encountered in everyday life.

Little is known about the etiology of small bowel carcinoid tumor (SBC), but a few studies have pointed to certain medical and lifestyle factors as potential risk factors. This study aims to evaluate these findings and to identify new associations.

This paper presents design and methods of a follow-up study of fecundability (defined as the probability of conception during one menstrual cycle) in first-pregnancy planners. We recruited 430 couples by postal letter among 52,255 members of four trade unions. Couples without earlier reproductive experience were enrolled when they discontinued contraception and were followed in six complete menstrual cycles or until a pregnancy was recognized. Data included daily recordings of coitus and menstrual bleeding. Blood, semen, and urine specimens were collected to assess endocrine profile, semen quality, occult embryonal loss, and occupational exposures. Information was obtained about 1661 menstrual cycles (94% of expected). The proportion of couples obtaining a clinical pregnancy during 6 months of follow-up was 65%, and the average probability to obtain a pregnancy across all cycles was 16% (95% CI 14-18%). Among all conceptions the proportion of early embryonal loss was 17% (95% CI 12-22%). This study demonstrates the feasibility of a prospective study of fertility and that the established study base can provide useful information on environmental risk to subfertility.

To discover whether tobacco smoking and intake of different types of alcoholic drinks are associated with small bowel adenocarcinoma (SBA).A population-based European multi-center case-control study was conducted from 1995 to 1997.After a histological review using uniform diagnostic criteria, 47 (33%) of the 142 identified cases of SBA were excluded due to reclassification as either tumors of the papilla of Vater (n = 22), stromal tumors, or metastases; 95 cases were accepted for study. In all, 70 cases of SBA together with 2070 controls matched by age, sex, and region were interviewed. A high intake (more than 24 g alcohol per day) of beer or spirits was associated with SBA, an odds ratio (OR) of 3.5 and 95% confidence intervals (CI) of 1.5-8.0 and 3.4 (95% CI 1.3-9.2), respectively). There was no association with wine intake or total alcohol intake. Tobacco smoking was probably unrelated to SBA.A high intake of beer or spirits seems to be a risk factor for SBA. Since this association was not seen for wine drinkers, protective components of wine may counterbalance a carcinogenic effect of alcohol on the small bowel. Alternatively, the result may be confounded by other factors, e.g. dietary factors.

Organic solvents have been suspected to exert detrimental effects on human spermiogenesis. Styrene, which is both mutagenic and neurotoxic, was selected as a suitable organic solvent for further assessment of a possible effect on semen quality and sperm DNA damage.

Increased mortality is often reported among workers in short term employment. This may indicate either a health-related selection process or the presence of different lifestyle or social conditions among short term workers. The authors studied these two aspects of short term employment among 16,404 Danish workers in the reinforced plastics industry who were hired between 1978 and 1985 and were followed to the end of 1988. Preemployment hospitalization histories for 1977-1984 were ascertained and were related to length ofemployment between 1978 and 1988. Workers who had been hospitalized prior to employment showed a 20% higher risk of early termination of employment than those never hospitalized (rate ratio (RR) = 1.20, 95% confidence interval (Cl) 1.16-1.29), and the risk increased with number of hospitalizations. For workers with two or more preemployment hospitalizations related to alcohol abuse or violence, the rate ratios for short term employment were 2.30 (95% Cl 1.74-3.06) and 1.86 (95% Cl 1.35-2.56), respectively. An unhealthy lifestyle may also be a determinant of short term employment. While it is possible in principle to adjust for lifestyle factors if proper data are collected, the health-related selection of workers requires careful consideration when choosing a reference group for comparative studies of cumulative occupational exposure.

Little is known about the importance of semen quality in male infertility. We followed 430 first pregnancy planners with no previous reproductive experience recruited among more than 50,000 cohabiting trade-union members. The couples were consecutively enrolled into the study as they discontinued contraception and were followed up for six month menstrual cycles or until a pregnancy was verified. Each man provided a semen sample at enrollment. Women kept daily record of vaginal bleeding and sexual activity. The probability of conception increased with increasing sperm concentration up to 40 x 10(6)/ml, but any higher sperm density was not associated with additional likelihood of pregnancy. The proportion of sperm with normal morphology was strongly related to likelihood of pregnancy, independently of sperm concentration. In conclusion, sperm concentration and morphology are valuable biological markers of male fecundity. Reference values for semen quality based on biological knowledge can be established.

To assess the effect of psychological distress on time to first pregnancy.

To examine the effect of alcohol consumption on the probability of conception.

The association between fertility and job strain defined as high job demands and low job control has not previously been studied. A follow-up study was conducted with prospective collection of information on job strain among women, achievement of pregnancy, and potential confounding variables.

A cohort of 34,560 men and 6128 women employed in 660 European factories manufacturing reinforced plastic products, followed up originally to assess the risk of cancer, was used to assess the risk of non-malignant respiratory diseases associated with exposure to styrene. Mortality from pneumonia was associated with intensity of exposure to styrene, but this may have been due to chance. Mortality from bronchitis, emphysema, and asthma was not associated with styrene exposure.

To study the occurrence of non-malignant diseases and solid cancers in workers exposed to styrene in the Danish reinforced plastics industry.

Increased occurrences of malignancies of the lymphatic and haematopoietic tissues have been reported from industries in which employees are potentially exposed to styrene. The aim of the study reported here was to describe cancer incidence in the reinforced plastics industry in Denmark. A total of 64,000 employees of 552 Danish companies assessed to have produced reinforced plastics at any time since the 1960s were identified from a public administrative registry of all Danish employers and wage earners. Cancer incidence in the population was compared with similar rates for the population at large. No excess risk for all neoplasms was observed. Among male employees, increased risks were found for cancer of the lung (396 cases; relative risk [RR], 1.15; 95% confidence interval, 1.04-1.27), of the pleura (20 cases; RR, 2.33; 1.42-3.60), of the nasal cavities (nine cases; RR, 1.55; 0.71-2.94), of non-Hodgkin's lymphoma (61 cases; RR, 1.27; 0.97-1.63) and for leukaemia (61 cases; RR, 1.15; 0.88-1.48). Among female employees, a reduced risk for non-Hodgkin's lymphoma was observed (one case; RR, 0.16; 0.00-0.88). Some support was thus found for previous reports of increased risk for respiratory cancers and for malignancies of the lymphatic and haematopoietic tissues. The results must be interpreted with caution, however, owing to shortcomings in the design of the study.

The Danish Cancer Register recorded a significant excess incidence of bladder tumours among men in West Lolland during the period 1970 and 1979. No corresponding excess incidence of cancer of the lung was recorded. This might suggest that causes other than increased prevalence of smokers explain the recorded findings. A case-control investigation was carried out to illustrate possible occupational causal factors with the aid of the Cancer Register database concerning cancer and occupation which is based on linking of the Cancer Register with the Supplementary Pension Fund (additional pensions supplementary pension fund awarded via the Labour Market.) Increased risks of bladder tumours were demonstrated in several occupations which are recognized as involving a risk for this disease. A significantly increased risk was demonstrated in the transport occupation. No evidence was found to suggest that the peculiar occupational structure of the region could explain the excess risk registered.

Mental distress has often been suggested as a cause of unexplained infertility. However, the causal direction may well be from infertility to distress, and prospective data are needed. We therefore followed 393 couples, who were planning their first pregnancy, with prospective collection of information on distress from termination of birth control until pregnancy for a maximum of six menstrual cycles. The analyses included 1,475 menstrual cycles, and mental distress was measured in each cycle by the General Health Questionnaire (GHQ). Urine samples from each period of vaginal bleeding were analyzed for human chorionic gonadotrophic hormone, indicating early embryonal loss. We found that for cycles with the highest distress score (GHQ score above the 80 percentile) the probability of conception per cycle was 12.8% compared to 16.5% in other cycles (adjusted OR 0.6; 95% CI 0.4-1.0). The effect of distress was almost exclusively found among women with long menstrual cycles (OR 0.1; 95% CI 0.01-0.4 and OR 0.9; 0.5-1.4 for women with cycles > or = 35 and