Cancer incidence in a cohort of Danish firefighters: An extended long-term follow-up 1968-2021.

OBJECTIVES: To update and extend the examination of cancer incidence in a cohort of Danish firefighters, now adding 7 years of follow-up and 2766 additional firefighters. The primary focus was directed toward cancer sites that recently contributed to the hazard evaluation conducted by the International Agency for Research on Cancer (IARC). METHODS: The updated cohort consisted of 11,827 male Danish firefighters who were followed up for cancer from 1968 to 2021. Cohort cancer morbidity was compared with a working population reference group, and standardized incidence ratios (SIR) were used for estimation of relative risks, along with 95% confidence intervals (95% CI). RESULTS: Among full-time firefighters, SIR of skin melanoma was 1.30 (95% CI: 1.02-1.66), and SIR = 1.37 (95% CI: 1.02-1.85) for over 5 years of employment. Slightly positive associations were also observed for cancer of the urinary bladder (SIR = 1.16; 95% CI: 0.93-1.45), prostate (SIR = 1.11; 95% CI: 0.97-1.28), and testis (SIR = 1.11; 95% CI: 0.75-1.63). CONCLUSIONS: This updated study provides evidence indicating an elevated risk of skin melanoma in firefighters. Consistent with IARC's evaluation, we also identified positive associations for urinary bladder, prostate, and testis cancer. In contrast, our findings did not suggest an increased risk of colon cancer, non-Hodgkin lymphoma, and mesothelioma. The latter may be due to small numbers in our still relatively young cohort. Continuous follow-up for cancer in firefighters is warranted, including assessment of influence from surveillance bias.

Work stress and loss of years lived without chronic disease: an 18-year follow-up of 1.5 million employees in Denmark.

We aimed to examine the association between exposure to work stress and chronic disease incidence and loss of chronic disease-free life years in the Danish workforce. The study population included 1,592,491 employees, aged 30-59 in 2000 and without prevalent chronic diseases. We assessed work stress as the combination of job strain and effort-reward imbalance using job exposure matrices. We used Cox regressions to estimate risk of incident hospital-diagnoses or death of chronic diseases (i.e., type 2 diabetes, coronary heart disease, stroke, cancer, asthma, chronic obstructive pulmonary disease, heart failure, and dementia) during 18 years of follow-up and calculated corresponding chronic disease-free life expectancy from age 30 to age 75. Individuals working in occupations with high prevalence of work stress had a higher risk of incident chronic disease compared to those in occupations with low prevalence of work stress (women: HR 1.04 (95% CI 1.02-1.05), men: HR 1.12 (95% CI 1.11-1.14)). The corresponding loss in chronic disease-free life expectancy was 0.25 (95% CI - 0.10 to 0.60) and 0.84 (95% CI 0.56-1.11) years in women and men, respectively. Additional adjustment for health behaviours attenuated these associations among men. We conclude that men working in high-stress occupations have a small loss of years lived without chronic disease compared to men working in low-stress occupations. This finding appeared to be partially attributable to harmful health behaviours. In women, high work stress indicated a very small and statistically non-significant loss of years lived without chronic disease.

Maternal pre-pregnancy overweight and infertility in sons and daughters: A cohort study.

INTRODUCTION: Overweight and obesity in pregnancy is increasing worldwide and may harm the developing fetus, including its future reproductive health. We therefore studied the association between in utero exposure to maternal overweight and obesity and infertility in adulthood. No studies have previously assessed this association. MATERIAL AND METHODS: We performed a cohort study with 9232 adult sons and daughters whose mothers were enrolled in the Danish Healthy Habits for Two cohort during pregnancy in 1984-87. Participants were sons and daughters followed in the Danish In-Vitro-Fertilization-Register and Danish National Patient Register until February 2018 for diagnoses of infertility. RESULTS: In total, 1203 (13%) sons and daughters were born to mothers with a body mass index (BMI) >25 kg/m2 ; 871 (9.4%) of the participants were identified as being infertile during follow-up. Sons of overweight mothers had slightly increased odds of infertility compared with sons of mothers with normal body weight (BMI 18.5-24.9 kg/m2 , adjusted odds ratio 1.4, 95% confidence interval [CI] 1.0-1.9). Cubic spline analyses with continuous BMI levels showed increasing odds with higher levels of BMI; however, for BMI >29 kg/m2 the confidence intervals were too wide to draw conclusions. No association between maternal overweight and infertility was found among daughters (adjusted odds ratio 0.9, 95% CI 0.7-1.2)). CONCLUSIONS: Sons born to overweight mothers had higher odds of infertility compared with sons of normal weight mothers. No association between maternal overweight and infertility was observed in daughters. Prevention of overweight during pregnancy may be an important tool to preserve fecundity in future generations.

Infertility in a Cohort of Male Danish Firefighters: A Register-Based Study.

Our aim in this study was to examine infertility among male firefighters in Denmark. Thus, we established a cohort of 4,710 past and present male Danish firefighters through personnel and membership records obtained from employers and trade unions. Information on vital status and infertility from the Danish Civil Registration System, the In Vitro Fertilisation Register, and the National Patient Register for the period 1984-2017 was linked to cohort members using their Danish personal identification numbers. Hazard ratios and corresponding 95% confidence intervals were estimated for male-factor infertility and overall infertility through Cox regression analyses comparing the firefighters with 2 reference groups: a sample of employees and military men. Among the full-time firefighters, the risk of male-factor infertility was increased in comparison with the sample of employees (In Vitro Fertilisation Register model: hazard ratio = 1.46 (95% confidence interval: 1.10, 1.94); National Patient Register model: hazard ratio = 1.53 (95% confidence interval: 1.18, 1.98)). Results were less consistent using the military men as the reference group. Further, the increase in infertility seemed restricted to duration of time employed as a firefighter. No increase in risk of either male-factor infertility or overall infertility was seen among the part-time/volunteer firefighters. Thus, full-time firefighting was associated with a greater risk of being diagnosed with male-factor infertility in our cohort.

Occupational hand eczema and/or contact urticaria: factors associated with change of profession or not remaining in the workforce.

BACKGROUND: Occupational hand eczema and/or contact urticaria may have social consequences such as change of profession or not remaining in the workforce. OBJECTIVES: To identify factors associated with job change in a cohort of participants with recognised occupational hand eczema/contact urticaria METHODS: A registry-based study including 2703 employees with recognised occupational hand eczema/contact urticaria in Denmark in 2010/2011. Four to five years later the participants received a follow-up questionnaire, comprising questions on current job situation (response rate 58.0%). RESULTS: At follow-up, 51.3% of the participants were no longer in the same profession. 32.5% had changed profession and 18.8% were no longer in employment. Change of profession was associated with young age, positive patch test, low educational level and severity of hand eczema/contact urticaria. With regard to specific professions, cleaning personnel changed profession significantly more often than other workers [71.4% (OR = 2.26)], health care workers significantly less often than other workers [34.0% (OR = 0.36)]. CONCLUSION: Job change occurs frequently during the first years after recognition of occupational hand eczema/contact urticaria and more often among patients with positive patch test reactions, with severe hand eczema/contact urticaria. Whether job changes improve the prognosis of occupational hand eczema/contact urticaria remains to be established.

Impact of hand eczema on quality of life: metropolitan versus non-metropolitan areas.

BACKGROUND: An inverse relationship between disease severity and health-related quality of life (HR-QoL) in patients with hand eczema is well established, but modifying effects of demographic variables have been less well studied. OBJECTIVE: To identify the influence of metropolitan versus non-metropolitan residence on the relationship between disease severity and HR-QoL in patients with occupational hand eczema. METHODS: The city of Copenhagen and the rest of Zealand were defined as metropolitan and non-metropolitan areas, respectively. Participants were 773 persons with occupational hand eczema. A questionnaire on the severity of hand eczema and HR-QoL was sent to all participants. RESULTS: The odds for reporting moderate to high severity of occupational hand eczema were significantly lower in the metropolitan population than in the non-metropolitan population [odds ratio (OR): 0.42; 95%CI: 0.23-0.75], whereas low dermatology-related quality of life was more prevalent in metropolitan than in non-metropolitan patients (OR: 1.31; 95%CI: 0.83-2.05), indicating that hand eczema had a more pronounced negative effect in metropolitan patients, in spite of less severe eczema. CONCLUSION: Our data indicate that area of residence has a modifying effect on the relationship between disease severity and HR-QoL, with a more negative impact on HR-QoL in metropolitan than in non-metropolitan areas. This information is important with respect to fully appreciating the burden of occupational hand eczema.

Hand eczema and wet work: dose-response relationship and effect of leaving the profession.

BACKGROUND: Wet work is an important risk factor for occupational hand eczema. OBJECTIVES: To examine the effect of job change in workers with occupational hand eczema caused by wet work, and to evaluate the dose-response relationship between intensity of wet work and eczema. METHOD: The study is based on a subgroup (n = 954) from a descriptive, registry-based study including all participants with occupational hand eczema caused by wet work recognized by the Danish Labour Market Insurance Authority in 2010 and 2011. A follow-up questionnaire was sent out 4-5 years later (response 58%). RESULTS: Change of profession and being outside the labour market had a positive effect on healing and improvement of hand eczema. Inverse dose-response relationships were found between the amount of time spent with wet hands at work and healing (p = 0.001) and improvement (p < 0.001), and between the frequency of hand washing at work and healing (p = 0.013) and improvement (p < 0.001). CONCLUSIONS: Leaving the profession has a positive effect on eczema; however, even minor changes in exposure to wet work were associated with healing and improvement. This information has implications with respect to advice given to patients with occupational hand eczema caused by wet work.

Simple, low-cost group-counselling programme vs treatment as usual for patients with newly notified occupational hand eczema-Exploratory analyses of effects on knowledge, behaviour and personal resources of the randomized PREVEX clinical trial.

BACKGROUND: Sickness absence in hand eczema patients has been associated with stress rather than disease severity, indicating that personal aspects regarding hand eczema should be investigated further. OBJECTIVES: To examine whether patient education vs treatment as usual can influence behaviour and knowledge regarding skin protection and care, as well as personal resources, in patients with occupational hand eczema. METHODS: PREVEX is an individually randomized clinical trial investigating the 1-year effects of a simple, low-cost group-counselling programme vs treatment as usual for patients with notified occupational hand eczema. Exploratory outcomes were behaviour, knowledge, self-efficacy, and self-evaluated skin care ability. RESULTS: In total, 1668 patients with notified occupational skin disease were invited to participate, of whom 769 were randomized and 756 were analysed: intervention group (n = 376) vs control group (n = 380). Behaviour was improved and the knowledge score increased in the intervention group as compared with the control group (respectively: estimate 0.08; 95%CI: 0.02-0.19; P = .01; and estimate 0.49; 95%CI: 0.28-0.70; P < .001). Self-efficacy was lower in the intervention group as compared with the control group (estimate -0.78; 95%CI: -1.25 to -0.30; P = .001). No difference was found regarding skin care abilities. CONCLUSIONS: The intervention had a positive influence on 1-year behaviour and knowledge, but was insufficient to result in long-term positive changes in personal resources regarding dealing with hand eczema.

Noise-Induced Hearing Loss - A Preventable Disease? Results of a 10-Year Longitudinal Study of Workers Exposed to Occupational Noise.

AIMS: To survey current, Danish industrial noise levels and the use of hearing protection devices (HPD) over a 10-year period and to characterise the association between occupational noise and hearing threshold shift in the same period. Furthermore, the risk of hearing loss among the baseline and the follow-up populations according to first year of occupational noise exposure is evaluated. MATERIALS AND METHODS: In 2001-2003, we conducted a baseline survey of noise- and hearing-related disorders in 11 industries with suspected high noise levels. In 2009-2010, we were able to follow up on 271 out of the 554 baseline workers (49%). Mean noise levels per industry and self-reported HPD use are described at baseline and follow-up. The association between cumulative occupational noise exposure and hearing threshold shift over the 10-year period was assessed using linear regression, and the risk of hearing loss according to year of first occupational noise exposure was evaluated with logistic regression. RESULTS: Over the 10-year period, mean noise levels declined from 83.9 dB(A) to 82.8 dB(A), and for workers exposed >85 dB(A), the use of HPD increased from 70.1 to 76.1%. We found a weak, statistically insignificant, inverse association between higher ambient cumulative noise exposure and poorer hearing (-0.10 dB hearing threshold shift per dB-year (95% confidence interval (CI): -0.36; 0.16)). The risk of hearing loss seemed to increase with earlier first year of noise exposure, but odds ratios were only statistically significant among baseline participants with first exposure before the 1980s (odds ratio: 1.90, 95% CI: 1.11; 3.22). CONCLUSIONS: We observed declining industrial noise levels, increased use of HPD and no significant impact on hearing thresholds from current ambient industrial noise levels, which indicated a successful implementation of Danish hearing conservation programs.

Difficulties in using Material Safety Data Sheets to analyse occupational exposures to contact allergens.

BACKGROUND: Information on the occurrence of contact allergens and irritants is crucial for the diagnosis of occupational contact dermatitis. Material Safety Data Sheets (MSDS) are important sources of information concerning exposures in the workplace. OBJECTIVE: From a medical viewpoint, to evaluate the information available from MSDSs, and to ascertain whether MSDS are easy to obtain, whether they serve their purpose, and whether they provide sufficient information regarding allergens to enable correct diagnosis. METHODS: MSDS and ingredients labelling were collected from consecutive patients and reviewed. If it was suspected that the MSDS were incomplete, the manufacturer, supplier, salesperson or workplace was contacted to gather more information. RESULTS: Twenty-five per cent (79/316) of patients provided material for the exposure assessment. One or more shortcomings were found in 18.6% (137/738) of the MSDS. The most frequent shortcoming was 'Missing R43/H317 while known contact allergen was present', which was observed in 63.1% (84/137). Other shortcomings were 'Names of preservatives not included in section 3 despite containing preservatives', in 48.9% (67/137), and 'Nothing about allergy in sections 2, 3, 11, 15 or 16 in the MSDS despite the content of allergens', in 20.4% (28/137). The information retrieved led to additional testing of 21 patients. CONCLUSION: Systematic exposure assessment is time-consuming. The main shortcomings are errors/omissions in the MSDS.

Occupational irritant contact dermatitis diagnosed by analysis of contact irritants and allergens in the work environment.

BACKGROUND: Irritant contact dermatitis (ICD) is a common diagnosis in patients with occupational contact dermatitis (OCD). Studies are lacking on the usefulness of material safety data sheets (MSDSs) in making the diagnosis of ICD. OBJECTIVE: To characterize irritant exposures leading to the diagnosis of occupational ICD (OICD), and to evaluate the occurrence of concomitant exposures to contact allergens. METHODS: We included 316 patients with suspected occupational hand dermatitis, referred to the Department of Dermato-Allergology, Copenhagen University Hospital Gentofte, Denmark during January 2010-August 2011, in a programme consisting of a clinical examination, exposure assessment, and extensive patch/prick testing. RESULTS: OCD was diagnosed in 228 patients. Of these patients, 118 were diagnosed with OICD. The main irritant exposures identified were wet work (n = 64), gloves (n = 45), mechanical traumas (n = 19), and oils (n = 15). Exposure to specific irritant chemicals was found in 9 patients, and was identified from MSDSs/ingredients labelling in 8 of these patients. Review of MSDSs and ingredients labelling showed that 41 patients were exposed to 41 moderate to potent contact allergens, and 18 patients were exposed to 25 weak workplace contact allergens. CONCLUSION: In the present study, the systematic exposure assessment did not reveal any new irritants. MSDSs have a limited role in the investigation of ICD.

Associations between an international COVID-19 job exposure matrix and SARS-CoV-2 infection among 2 million workers in Denmark.

OBJECTIVES: This study investigates the associations between the Danish version of a job exposure matrix for COVID-19 (COVID-19-JEM) and Danish register-based SARS-CoV-2 infection information across three waves of the pandemic. The COVID-19-JEM consists of four dimensions on transmission: two on mitigation measures, and two on precarious work characteristics. METHODS: The study comprised 2 021 309 persons from the Danish working population between 26 February 2020 and 15 December 2021. Logistic regression models were applied to assess the associations between the JEM dimensions and overall score and SARS-CoV-2 infection across three infection waves, with peaks in March-April 2020, December-January 2021, and February-March 2022. Sex, age, household income, country of birth, wave, residential region and during wave 3 vaccination status were accounted for. RESULTS: Higher risk scores within the transmission and mitigation dimensions and the overall JEM score resulted in higher odds ratios (OR) of a SARS-CoV-2 infection. OR attenuated across the three waves with ranges of 1.08-5.09 in wave 1, 1.06-1.60 in wave 2, and 1.05-1.45 in those not (fully) vaccinated in wave 3. In wave 3, no associations were found for those fully vaccinated. In all waves, the two precarious work dimensions showed weaker or inversed associations. CONCLUSIONS: The COVID-19-JEM is a promising tool for assessing occupational exposure to SARS-CoV-2 and other airborne infectious agents that mainly spread between people who are in close contact with each other. However, its usefulness depends on applied restrictions and the vaccination status in the population of interest.

Parental occupational exposure to endocrine disrupting chemicals and male genital malformations: a study in the Danish National Birth Cohort study.

BACKGROUND: Sex hormones closely regulate development of the male genital organs during fetal life. The hypothesis that xenobiotics may disrupt endogenous hormonal signalling has received considerable scientific attention, but human evidence is scarce. OBJECTIVES: We analyse occurrence of hypospadias and cryptorchidism according to maternal and paternal occupational exposure to possible endocrine disrupting chemicals. METHODS: We conducted a follow-up study of 45,341 male singleton deliveries in the Danish National Birth Cohort during 1997-2009. Information on work during pregnancy was obtained by telephone interviews around gestational week 16. Parents' job titles were classified according to DISCO-88. A job exposure matrix for endocrine disrupting chemicals (EDCs) was implemented to assess occupational exposures. The Medical Birth and National Hospital Register provided data on congenital anomalies diagnosed at birth or during follow-up, which ended in 2009. Crude and adjusted hazard ratios (HR) were obtained from Cox regression models. RESULTS: Among all pregnancies, 6.3% were classified as possibly or probably exposed to EDCs. The most prevalent occupations conferring possible exposure were cleaners, laboratory technicians, hairdressers and agricultural workers (58% of all potentially exposed). The final cumulative incidence of cryptorchidism in boys was 2.2% (1002 cases), and of hypospadias 0.6% (262 cases). The occurrence of hypospadias increased when mothers were probably [HRa = 1.8 (95% CI 1.0-2.6)] or possibly exposed to one or more EDCs [HRa = 2.6 (95% CI 1.8-3.4). Possible paternal exposure to heavy metals increased the risk of hypospadias [HRa 2.2 (95% CI: 1.0-3.4)] and cryptorchidism [HRa 1.9 (95% CI: 1.1-2.7)]. None of the exposure groups reached statistical significance. CONCLUSION: The study provides some but limited evidence that occupational exposure to possible endocrine disrupting chemicals during pregnancy increases the risk of hypospadias.

Unemployment and pregnancy outcomes: a study within the Danish National Birth Cohort.

AIMS: To explore the relation between employment status, type of unemployment and pregnancy outcomes. METHODS: A cohort study of 7,282 pregnancies of unemployed women and 56,014 pregnancies among women in paid jobs was performed within the Danish National Birth Cohort. Pregnancy outcomes were ascertained and information about lifestyle, occupational, medical, and obstetric factors was obtained. Logistic regression was used to calculate odds ratios (OR) for fetal loss, congenital anomalies, multiple births, sex ratio, preterm and very preterm birth and small for gestational age status, adjusting for lifestyle, medical and obstetric factors. RESULTS: There were no differences in pregnancy outcomes between employed and unemployed women but women receiving unemployment benefit had an increased risk of preterm birth (adjusted OR (aOR) 1.16, 95% confidence interval (95% CI) 1.03-1.31) and having a small for gestational age child (aOR 1.08, 95% CI 1.00-1.19) compared with employed women. Women receiving sickness or maternity benefit had an increased risk of multiple birth (aOR 1.70, 95% CI 1.43-2.04), preterm (aOR 1.47, 95% CI 1.22-1.77) and very preterm birth (aOR 1.88, 95% CI 1.22-2.89), while those receiving an unreported type of support had an increased risk of preterm birth (aOR 1.40, 95% CI 1.02-1.93). CONCLUSIONS: We found no indication that being unemployed during pregnancy benefits or endangers the health of the child. Within the subgroups of unemployed women, we observed that women receiving unemployment and sickness or maternity benefits were at higher risk for some adverse pregnancy outcomes.

Testing the association between psychosocial job strain and adverse birth outcomes--design and methods.

BACKGROUND: A number of studies have examined the effects of prenatal exposure to stress on birth outcomes but few have specifically focused on psychosocial job strain. In the present protocol, we aim to examine if work characterised by high demands and low control, during pregnancy, is associated with the risk of giving birth to a child born preterm or small for gestational age. METHODS AND DESIGN: We will use the Danish National Birth Cohort where 100.000 children are included at baseline. In the present study 49,340 pregnancies will be included. Multinomial logistic regression will be applied to estimate odds ratios for the outcomes: preterm; full term but small for gestational age; full term but large for gestational age, as a function of job-strain (high strain, active and passive versus low strain). In the analysis we control for maternal age, Body Mass Index, parity, exercise, smoking, alcohol use, coffee consumption, type of work (manual versus non-manual), maternal serious disease and parents' heights as well as gestational age at interview. DISCUSSION: The prospective nature of the design and the high number of participants strengthen the study. The large statistical power allows for interpretable results regardless of whether or not the hypotheses are confirmed. This is, however, not a controlled study since all kinds of 'natural' interventions takes place throughout pregnancy (e.g. work absence, medical treatment and job-redesign). The analysis will be performed from a public health perspective. From this perspective, we are not primarily interested in the effect of job strain per se but if there is residual effect of job strain after naturally occurring preventive measures have been taken.

Fetal loss and maternal serum levels of 2,2',4,4',5,5'-hexachlorbiphenyl (CB-153) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) exposure: a cohort study in Greenland and two European populations.

BACKGROUND: In the present study, the aim is to examine the risk of fetal loss related to environmental 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) or 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) exposure. METHODS: We related LC/MS/MS measurements of CB-153 and p,p'-DDE in serum samples to interview-data on previous fetal loss in populations of pregnant women from Poland, Ukraine and Greenland. RESULTS: In total, 1710 women were interviewed, and 678 of these had at least one previous pregnancy. The risk of ever experiencing a fetal loss increased at higher levels of CB-153 and p,p'-DDE exposure, with an adjusted odds ratio (OR) of 2.4; confidence interval (CI) (1.1-5.5) for CB-153>200 ng/g lipid compared to 0-25 ng CB-153/g lipid and OR of 2.5 CI (0.9-6.6) for p,p'-DDE>1500 ng/g lipid compared to 0-250 ng DDE/g lipid. However, no clear dose response associations were observed. The results further suggest that high level of organochlorine serum concentrations may be related to repeated loss. CONCLUSIONS: The risk of fetal loss may increase at higher levels of CB-153 and p,p'-DDE exposure, although lack of dose response and inconsistencies between countries did not allow for firm conclusions.

Risk of infection and adverse outcomes among pregnant working women in selected occupational groups: A study in the Danish National Birth Cohort.

BACKGROUND: Exposure to infectious pathogens is a frequent occupational hazard for women who work with patients, children, animals or animal products. The purpose of the present study is to investigate if women working in occupations where exposure to infections agents is common have a high risk of infections and adverse pregnancy outcomes. METHODS: We used data from the Danish National Birth Cohort, a population-based cohort study and studied the risk of Infection and adverse outcomes in pregnant women working with patients, with children, with food products or with animals. The regression analysis were adjusted for the following covariates: maternal age, parity, history of miscarriage, socio-occupational status, pre-pregnancy body mass index, smoking habit, alcohol consumption. RESULTS: Pregnant women who worked with patients or children or food products had an excess risk of sick leave during pregnancy for more than three days. Most of negative reproductive outcomes were not increased in these occupations but the prevalence of congenital anomalies (CAs) was slightly higher in children of women who worked with patients. The prevalence of small for gestational age infants was higher among women who worked with food products. There was no association between occupation infections during pregnancy and the risk of reproductive failures in the exposed groups. However, the prevalence of CAs was slightly higher among children of women who suffered some infection during pregnancy but the numbers were small. CONCLUSION: Despite preventive strategies, working in specific jobs during pregnancy may impose a higher risk of infections, and working in some of these occupations may impose a slightly higher risk of CAs in their offspring. Most other reproductive failures were not increased in these occupations.

Increased incidence of infertility treatment among women working in the plastics industry.

Several plastic chemicals adversely affect reproductive ability. This study examined the possible association between employment in the plastics industry and infertility. Dynamic cohorts of economically active women and men were followed for hospital contacts due to infertility in the Danish Occupational Hospitalisation Register, from 1995 to 2005. A person was considered to be at increased risk in a particular year if plastic work was the main occupation in the previous year. Analyses were standardized according to county, socio-economic group, year and age. 107 cases of treatment for female infertility were observed among female plastic workers, as opposed to an expected 87.15 cases, i.e. relative risk was 1.23 (95% CI: 1.01-1.48). For male workers the numbers were 41 respectively 49.9 cases, with relative risk being 0.82 (95% CI: 0.59-1.11). The increased incidence of infertility treatment in female plastics workers motivates more specific studies of reproductive occupational health in the plastics industry.

Occupational causes of male infertility.

PURPOSE OF REVIEW: To highlight and discuss the new evidence on occupational and environmental risk to male reproductive function. RECENT FINDINGS: Semen quality following occupational exposure to boron (an acknowledged experimental reproductive toxicant) and benzene, and new evidence on low-level environmental exposure to widespread xenobiotics with endocrine actions. SUMMARY: The naturally occurring semimetal boron is an experimental reproductive toxicant, but now a Turkish semen study corroborates earlier evidence that high-level occupational exposure is not toxic to human spermatogenesis. It seems that human exposure levels are below the levels that cause reproductive toxicity in rodents. On the contrary, there is now ample evidence that the carcinogenic substance benzene may cause chromosomal aberrations in sperm at very low exposure levels. This includes chromosomal deletions that are known to cause infertility, mental retardation and congenital malformations. This research highlights the need to scrutinize the chemicals for possible male-mediated developmental toxicity. Several occupational studies are addressing adult testicular function in men exposed to chemicals that may interfere with endocrine signalling such as bisphenol A and phthalates, but findings are rather inconsistent and it remains to be established whether these widespread chemicals have any impact on male fertility.

A comparison of conventional and computer-assisted semen analysis (CRISMAS software) using samples from 166 young Danish men.

The aim of the present study was to compare assessments of sperm concentration and sperm motility analysed by conventional semen analysis with those obtained by computer-assisted semen analysis (CASA) (Copenhagen Rigshospitalet Image House Sperm Motility Analysis System (CRISMAS) 4.6 software) using semen samples from 166 young Danish men. The CRISMAS software identifies sperm concentration and classifies spermatozoa into three motility categories. To enable comparison of the two methods, the four motility stages obtained by conventional semen analysis were, based on their velocity classifications, divided into three stages, comparable to the three CRISMAS motility categories: rapidly progressive (A), slowly progressive (B) and non-progressive (C+D). Differences between the two methods were large for all investigated parameters (P < 0.001). CRISMAS overestimated sperm concentration and the proportion of rapidly progressive spermatozoa and, consequently, underestimated the percentages of slowly progressive and non-progressive spermatozoa, compared to the conventional method. To investigate whether results drifted according to time of semen analysis, results were pooled into quarters according to date of semen analysis. CRISMAS motility results appeared more stable over time compared to the conventional analysis; however, neither method showed any trends. Apparently, CRISMAS CASA results and results from the conventional method were not comparable with respect to sperm concentration and motility analysis. This needs to be accounted for in clinics using this software and in studies of determinants of these semen characteristics.