Occupational risk factors for nasopharyngeal cancer among female textile workers in Shanghai, China

Aims

To investigate whether occupational exposure to dusts and chemicals in the Chinese textile industry are associated with risk of nasopharyngeal cancer.

Methods

Sixty seven nasopharyngeal carcinoma (NPC) cases identified during 1989–98 and a random sample (n = 3188) of women were included in a case cohort study nested in a cohort of 267 400 women textile workers in Shanghai, China. A complete occupational history of work in the textile industry was obtained for each woman. A job exposure matrix developed by experienced industrial hygienists was used to assess exposures to specific dusts and chemicals.

Results

Risk of NPC is associated with cumulative exposure to cotton dust. The hazard ratio for women cumulatively exposed to >143.4 mg/m³ × years of cotton dust was 3.6 (95% CI 1.8 to 7.2) compared with unexposed women. Trends of increasing risk were also found with increasing duration of exposure to acids and caustics (p = 0.05), and with years worked in dyeing processes (p = 0.06). Women who worked at least 10 years in dyeing processes had a 3.6‐fold excess risk of NPC (95% CI 1.0 to 12.1).

Conclusions

Occupational exposure to cotton dust, acids, and caustics, and work in dyeing and printing jobs in the textile industry may have increased risk of NPC in this cohort.     

Subjective symptoms, sleeping problems, and cognitive performance in subjects living near mobile phone base stations

Background

The erection of mobile telephone base stations in inhabited areas has raised concerns about possible health effects caused by emitted microwaves.

Methods

In a cross‐sectional study of randomly selected inhabitants living in urban and rural areas for more than one year near to 10 selected base stations, 365 subjects were investigated. Several cognitive tests were performed, and wellbeing and sleep quality were assessed. Field strength of high‐frequency electromagnetic fields (HF‐EMF) was measured in the bedrooms of 336 households.

Results

Total HF‐EMF and exposure related to mobile telecommunication were far below recommended levels (max. 4.1 mW/m²). Distance from antennae was 24–600 m in the rural area and 20–250 m in the urban area. Average power density was slightly higher in the rural area (0.05 mW/m²) than in the urban area (0.02 mW/m²). Despite the influence of confounding variables, including fear of adverse effects from exposure to HF‐EMF from the base station, there was a significant relation of some symptoms to measured power density; this was highest for headaches. Perceptual speed increased, while accuracy decreased insignificantly with increasing exposure levels. There was no significant effect on sleep quality.

Conclusion

Despite very low exposure to HF‐EMF, effects on wellbeing and performance cannot be ruled out, as shown by recently obtained experimental results; however, mechanisms of action at these low levels are unknown.     

Cross shift changes in lung function among bar and restaurant workers before and after implementation of a smoking ban

Objective

To study possible cross shift effects of environmental tobacco smoke (ETS) on pulmonary function among bar and restaurant employees before and after the implementation of a smoking ban in Norway.

Methods

The study included 93 subjects employed in 13 different establishments in Oslo. They were examined at the beginning and end of a workshift both while ETS exposure was present and when smoking was banned. The mean exposure level of nicotine and total dust before the ban was 28 μg/m³ (range 3–65) and 275 μg/m³ (range 81–506), respectively. Following the smoking ban, the mean level of nicotine and total dust was 0.6 μg/m³ and 77 μg/m³, respectively. Assessment of lung function included dynamic lung volumes and flows.

Results

The cross shift reduction in forced vital capacity (FVC) among 69 subjects participating in both examinations changed from 81 ml (SD 136) during exposure to ETS to 52 ml (SD 156) (p = 0.24) following the smoking ban. The reduction in forced expired volume in one second (FEV1) during a workshift, was borderline significantly reduced when comparing the situation before and after the intervention, by 89 ml (SD = 132) compared to 46 ml (SD = 152) (p = 0.09), respectively. The reduction in forced mid‐expiratory flow rate (FEF_25–75%) changed significantly from 199 ml/s (SD = 372) to 64 ml/s (SD = 307) (p = 0.01). Among 26 non‐smokers and 11 asthmatics, the reduction in FEV1 and FEF_25–75% was significantly larger during ETS exposure compared to after the smoking ban. There was an association between the dust concentration and decrease in FEF_25–75% before the ban among non‐smokers (p = 0.048).

Conclusions

This first study of cross shift changes before and after the implementation of a smoking ban in restaurants and bars shows a larger cross shift decrease in lung function before compared with after the implementation of the ban.     

Agricultural seed dust as a potential cause of organic dust toxic syndrome

Aims

Episodes of serious work related health problems resembling organic dust toxic syndrome (ODTS) in workers of a grass seed quality inspection laboratory prompted the authors to study personal endotoxin exposure levels in this facility and in the agricultural seed processing industry. In addition, microbial and inflammatory characteristics of agricultural seeds were studied.

Methods

The authors assessed inhalable dust and endotoxin levels in 101 samples from 57 workers in grass, cereal, and vegetable seed plants who were handling mainly grass seeds as bulk product, and horticulture seeds in smaller quantities. Additionally, real‐time dust exposure was measured using a DataRAM monitor in 12 grass seed workers to obtain more information on exposure patterns during specific tasks. Endotoxin concentrations in seed extracts were determined by LAL assay and seed samples were analysed by scanning electron microscopy. Release of inflammatory cytokines was measured in supernatants of whole blood samples stimulated with lipopolysaccharide (LPS) or agricultural seed extracts in a human whole blood assay (WBA).

Results

Endotoxin concentrations in personal samples were high (geometric mean 1800 EU/m³), particularly in the grass seed quality inspection lab where endotoxin levels up to 274 000 EU/m³ were measured. The recommended health based endotoxin exposure limit of 50 EU/m³ was amply exceeded in almost all personal samples. Job tasks dumping and mixing were associated with highest dust and endotoxin exposures, which was confirmed by real‐time measurements. Microbial infestation was found in almost all seed samples. WBA results showed that most seed extracts were capable of inducing a pronounced dose dependent cytokine release.

Conclusions

Workers handling grass, cereal, or vegetable seeds are at risk of exposure to high levels of endotoxin containing seed dust. Occupational exposure to inhalable agricultural seed dust can induce inflammatory responses, and is a potential cause of ODTS.     

The Implications of Using a Physiologically Based Pharmacokinetic (PBPK) Model for Pesticide Risk Assessment

Background

A physiologically based pharmacokinetic (PBPK) model would make it possible to simulate the dynamics of chemical absorption, distribution, metabolism, and elimination (ADME) from different routes of exposures and, in theory, could be used to evaluate associations between exposures and biomarker measurements in blood or urine.

Objective

We used a PBPK model to predict urinary excretion of 3,5,6-trichloro-2-pyridinol (TCPY), the specific metabolite of chlorpyrifos (CPF), in young children.

Methods

We developed a child-specific PBPK model for CPF using PBPK models previously developed for rats and adult humans. Data used in the model simulation were collected from 13 children 3–6 years of age who participated in a cross-sectional pesticide exposure assessment study with repeated environmental and biological sampling.

Results

The model-predicted urinary TCPY excretion estimates were consistent with measured levels for 2 children with two 24-hr duplicate food samples that contained 350 and 12 ng/g of CPF, respectively. However, we found that the majority of model outputs underpredicted the measured urinary TCPY excretion.

Conclusions

We concluded that the potential measurement errors associated with the aggregate exposure measurements will probably limit the applicability of PBPK model estimates for interpreting urinary TCPY excretion and absorbed CPF dose from multiple sources of exposure. However, recent changes in organophosphorus (OP) use have shifted exposures from multipathways to dietary ingestion only. Thus, we concluded that the PBPK model is still a valuable tool for converting dietary pesticide exposures to absorbed dose estimates when the model input data are accurate estimates of dietary pesticide exposures.     

Occupational exposure to power frequency magnetic fields and risk of non-Hodgkin lymphoma

Objectives

To investigate the risk of non‐Hodgkin lymphoma (NHL) using a job‐exposure matrix (JEM) to assess exposure to occupational magnetic fields at the power frequencies of 50/60 Hz.

Methods

The study population consisted of 694 cases of NHL, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls from two regions in Australia, matched by age, sex and region of residence. A detailed occupational history was given by each subject. Exposure to power frequency magnetic fields was estimated using a population‐based JEM which was specifically developed in the United States to assess occupational magnetic field exposure. The cumulative exposure distribution was divided into quartiles and adjusted odds ratios were calculated using the lowest quartile as the referent group.

Results

For the total work history, the odds ratio (OR) for workers in the upper quartile of exposure was 1.48 (95% CI 1.02 to 2.16) compared to the referent (p value for trend was 0.006). When the exposure was lagged by 5 years the OR was 1.59 (95% CI 1.07 to 2.36) (p value for trend was 0.003). Adjusting for other occupational exposures did not significantly alter the results.

Conclusions

These findings provide weak support for the hypothesis that occupational exposure to 50/60 Hz magnetic fields increases the risk of NHL.     

Predictive validity of a retrospective measure of noise exposure

Aims

To investigate the validity of measures of noise exposure derived retrospectively for a cohort of nuclear energy workers for the period 1950–98, by investigating their ability to predict hearing loss.

Methods

Subjects were men aged 45–65 chosen from a larger group of employees—assembled for a nested case‐control study of noise and death from ischaemic heart disease—who had had at least one audiogram after at least five years'' work. Average hearing loss, across both ears and the frequencies 0.5, 1, 2, and 4 kHz, was calculated from the last audiogram for each man. Previous noise exposure at work was assessed retrospectively by three hygienists using work histories, noise survey records from 1965–98, and judgement about use of hearing protection devices. Smoking and age at the time of the audiogram were extracted from records. Differences in hearing loss between men categorised by cumulative noise exposure were assessed after controlling for age, smoking, year of test, and previous test experience.

Results

There were 186 and 150 eligible subjects at sites A and B of the company respectively who were employed for an average of 20 years. Compared to men with less than one year''s exposure to levels of 85dB(A) or greater, hearing loss was greater by 3.7 dB (90% CI −2.6 to 10.1), 3.8 dB (90% CI −2.6 to 10.3), 7.0 dB (90% CI 1.1 to 12.9) and 10.1 dB (90% CI 4.2 to 16.0) in the lowest to highest categories of cumulative noise exposure at site B. In contrast, at site A, the corresponding figures were −2.2 dB, −2.4 dB, −1.8 dB, and −4.4 dB, with no confidence interval excluding zero.

Conclusions

Noise estimation at one site was shown to have predictive validity in terms of hearing loss, but not at the other site. Reasons for the differences between sites are discussed.Retrospective estimation of exposure is common in occupational epidemiology but often there is little opportunity to validate the resulting measure. However, if the exposure is already accepted to cause a particular adverse outcome, it may be possible to assess the predictive validity of the measure—that is, its ability to predict the adverse event. We developed a method¹ for retrospective estimation of noise exposure within an occupational cohort for use in a study of noise and cardiovascular mortality.² Since excessive noise can cause hearing loss,^3,4,5 and audiograms had been carried out on a sample of the cohort, an opportunity arose to investigate the predictive validity of the noise measure. We report here the results of that investigation.     

Do ambient noise exposure levels predict hearing loss in a modern industrial cohort?

Background

Much of what is known about the exposure–response relationship between occupational noise exposures and hearing loss comes from cross‐sectional studies conducted before the widespread implementation of workplace hearing conservation programmes. Little is known about the current relationship of ambient noise exposure measurements to hearing loss risk.

Aim

To examine the relationship between rates of high frequency hearing loss and measured levels of noise exposure in a modern industrial workforce.

Methods

Ten‐year hearing loss rates were determined for 6217 employees of an aluminium manufacturing company. Industrial hygiene and human resources records allowed for reconstruction of individual noise exposures. Hearing loss rates were compared to ANSI 3.44 predictions based on age and noise exposure. Associations between hearing loss, noise exposure, and covariate risk factors were assessed using multivariate regression.

Results

Workers in higher ambient noise jobs tended to experience less high frequency hearing loss than co‐workers exposed at lower noise levels. This trend was also seen in stratified analyses of white males and non‐hunters. At higher noise exposure levels, the magnitude of hearing loss was less than predicted by ANSI 3.44 formulae. There was no indication that a healthy worker effect could explain these findings. The majority of 10 dB standard threshold shifts (STS) occurred in workers whose calculated ambient noise exposures were less than or equal to 85 dBA.

Conclusions

In this modern industrial cohort, hearing conservation efforts appear to be reducing hearing loss rates, especially at higher ambient noise levels. This could be related to differential use of hearing protection. The greatest burden of preventable occupational hearing loss was found in workers whose noise exposure averaged 85 dBA or less. To further reduce rates of occupational hearing loss, hearing conservation programmes may require innovative approaches targeting workers with noise exposures close to 85 dBA.     

Renal function, bisphenol A, and alkylphenols: results from the National Health and Nutrition Examination Survey (NHANES 2003-2006)

Background

Urinary excretion of bisphenol A (BPA) and alkylphenols (APs) was used as a biomarker in most previous studies, but no study has investigated whether urinary excretion of these environmental phenols differed by renal function.

Objective

We estimated the association between renal function and urinary excretion of BPA and APs.

Methods

Analyses were conducted using data from the National Health and Nutrition Examination Survey (NHANES) 2003–2006. Renal function was measured as estimated glomerular filtration rate (eGFR) calculated by the Modification of Diet in Renal Disease (MDRD) Study equation and by the newly developed Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Regression models were used to calculate geometric means of urinary BPA and APs excretion by eGFR category (≥ 90, 60–90, < 60 mL/min/m²) after adjusting for potential confounding factors.

Results

When we used the MDRD Study equation, participants without known renal disease (n = 2,573), 58.2% (n = 1,499) had mildly decreased renal function or undiagnosed chronic kidney disease. The adjusted geometric means for urinary BPA excretion decreased with decreasing levels of eGFR (p for trend = 0.04). The associations appeared primarily in females (p for trend = 0.03). Urinary triclosan excretion decreased with decreasing levels of eGFR (p for trend < 0.01) for both males and females, and the association primarily appeared in participants < 65 years of age. The association between BPA and eGFR was nonsignificant when we used the CKD-EPI equation.

Conclusions

Urinary excretion of triclosan, and possibly BPA, decreased with decreasing renal function. The associations might differ by age or sex. Further studies are necessary to replicate our results and understand the mechanism.     

Occupational and other risk factors for hand-grip strength: the Honolulu-Asia Aging Study

Background

In certain occupations, including farm work, workers are exposed to hazardous substances, some of which are known to be toxic to the nervous system and may adversely affect muscle strength. Measurement of hand‐grip strength may be useful for detecting neurotoxic exposure.

Methods

The authors studied 3522 participants of the Honolulu Heart Program and the Honolulu‐Asia Aging Study to determine whether occupational exposures to pesticides, solvents, and metals assessed at exam I (1965–68) are associated with hand‐grip strength at exam IV (1991–93) and change in hand‐grip strength over 25 years. Correlation, analysis of variance and covariance, and linear regression were used to evaluate the associations.

Results

At exam IV, participants ranged in age from 71–93 years; mean hand‐grip strength was 39.6 kg at exam I and 30.3 kg at exam IV. Over 25 years, the decline in hand‐grip strength was an average of 8–9 kg for all exposures. Hand‐grip strength was inversely associated with age and glucose but directly associated with cognitive function, BMI, and haemoglobin level. No other exposures were associated with hand‐grip strength.

Conclusion

This study did not provide evidence that occupational exposure to pesticides, solvents, and metals adversely affected hand‐grip strength in this population, but confirmed other important associations with hand‐grip strength.     

Dust related risks of clinically relevant lung functional deficits

Aim

To quantify the risks of clinically important deficits of FEV1 in coal miners in relation to cumulative and average concentrations of respirable dust.

Methods

Data were studied from over 7000 men who had been surveyed in the late 1970s. Linear regression equations for the association between FEV1 and self‐reported breathlessness on mild exertion were used to define clinically important levels of FEV1 deficit, and the probabilities that individuals with different dust exposures would experience these deficits were calculated.

Results

Levels of FEV1 were lower among breathless men than among others, with a large overlap of the distributions. The relations between standardised FEV1 and breathlessness were constant over all age and smoking groups. A decrease of 100 ml in FEV1 was associated with an increase of 1.12 in the odds of reporting breathlessness. FEV1 deficits of −0.367, −0.627, and −0.993 l (designated as “small”, “medium”, and “large” deficits) were, on average, associated with proportional increases of risks of breathlessness by factors of 1.5, 2.0, and 3.0 respectively. Cumulative respirable dust exposure ranged up to 726 gh/m³, mean 136 gh/m³ (British Medical Research Council measurement convention). An increase of 50 gh/m³ was associated with an increase of about 2% in the proportion of men with small deficits in FEV1. For medium deficits the increases ranged from 1.5% to 2%, depending on age. A similar pattern was seen for large deficits, but with smaller increases.

Conclusions

In the unlikely event of continuous exposure at the proposed new maximum respirable dust limit for British mines of 3 mg/m³ (ISO‐CEN measurement convention) for a working lifetime, the risk of a medium deficit of FEV1 for a non‐smoker at age 60 would be estimated to be 34%, compared with 25% for zero dust exposure; for smokers, about 54% compared with 44%.     

Can strenuous leisure time physical activity prevent psychological complaints in a working population?

Aims

To investigate the longitudinal relation between strenuous leisure time physical activity and psychological complaints (depression and emotional exhaustion) in a Dutch working population in order to find evidence for the preventive role of physical activity in the development of psychological complaints.

Methods

All data came from the Study on Musculoskeletal disorders, Absenteeism, Stress, and Health (SMASH), a three year follow up study that started between 1994 and 1995. The study population consisted of 1747 workers from 34 companies. Generalised estimating equation (GEE) analyses were performed to investigate the longitudinal relation between strenuous leisure time physical activity and psychological complaints using models with and without a time lag. Logistic regression analyses were performed to study the relation between physical activity and sickness absence due to psychological complaints during the three year follow up study.

Results

Only in workers with a sedentary job was strenuous leisure time physical activity (1–2 times per week) significantly associated with a reduced risk of future depression and emotional exhaustion. This was not the case for physical activity at higher frequencies (⩾3 times per week). There was a dose‐response relation between strenuous leisure time physical activity and poor general health which was strongest in workers with a sedentary job. Strenuous leisure time physical activity (1–2 times per week) was associated with a lower risk of long term absenteeism (>21 days), whereas physical activity at a higher frequency was not.

Conclusions

Results suggest that strenuous leisure time physical activity might play a role in the prevention of future psychological complaints, poor general health, and long term absenteeism in a working population. Workers with a sedentary job seem to benefit more from strenuous leisure time physical activity than workers without a sedentary job.     

Incidence of dimethylacetamide induced hepatic injury among new employees in a cohort of elastane fibre workers

Objective

To investigate the incidence of N,N‐dimethylacetamide (DMA) induced hepatic injury among new elastane fibre workers and to explore factors relating to DMA induced hepatic injury.

Methods

Elastane fibre workers exposed to DMA were monitored for hepatic injury. Four hundred and forty new workers employed from 1 January 2002 to 31 July 2004 were included as study subjects. DMA exposure estimates were based on urinary N‐methylacetamide (NMA) concentrations.

Results

There were 28 cases of DMA induced hepatic injury. The overall incidence of DMA induced hepatic injury among new elastane fibre workers was 0.089/person‐year. Incidence rates were 7–10 times higher in high exposure groups than in low exposure groups. Fewer DMA induced hepatic injuries occurred among workers employed for a longer period. Workers whose exposure duration was more than seven months showed no hepatic injury in either the high or low exposure groups. Exposure category and duration of employment were significant variables in the multiple logistic regression analysis.

Conclusions

Results suggest the existence of dose dependent DMA induced hepatic injury. The inverse relation between the incidence of DMA induced hepatic injury and duration of employment may reflect a type of healthy survivor effect or tolerance to DMA induced hepatic injury.     

DNA damage in outdoor workers occupationally exposed to environmental air pollutants

Background

Health concerns about the exposure to genotoxic and carcinogenic agents in the air are particularly significant for outdoor workers in less developed countries.

Aims

To investigate the association between personal exposure to a group of air pollutants and severity of DNA damage in outdoor workers from two Mexican cities.

Methods

DNA damage (Comet assay) and personal exposure to volatile organic compounds, PM_2.5, and ozone were investigated in 55 outdoor and indoor workers from México City and Puebla.

Results

In México City, outdoor workers had greater DNA damage, reflected by a longer tail length, than indoor workers (median 46.8 v 30.1 μm), and a greater percentage of highly damaged cells (cells with tail length ⩾41 μm); in Puebla, outdoor and indoor workers had similar DNA damage. There were more alkali labile sites in outdoor than indoor workers. The DNA damage magnitude was positively correlated with PM_2.5 and ozone exposure. Outdoor and indoor workers with ⩾60% of highly damaged cells (highly damaged workers) had significantly higher exposures to PM_2.5, ozone, and some volatile organic compounds. The main factors associated with the highly damaged workers were ozone, PM_2.5, and 1‐ethyl‐2‐methyl benzene exposure.

Conclusions

With this approach, the effects of some air pollutants could be correlated with biological endpoints from the Comet assay. It is suggested that the use of personal exposure assessment and biological endpoints evaluation could be an important tool to generate a more precise assessment of the associated potential health risks.     

Workplace Secondhand Smoke Exposure in the U.S. Trucking Industry

Background

Although the smoking rate in the United States is declining because of an increase of smoke-free laws, among blue-collar workers it remains higher than that among many other occupational groups.

Objectives

We evaluated the factors influencing workplace secondhand smoke (SHS) exposures in the U.S. unionized trucking industry.

Methods

From 2003 through 2005, we measured workplace SHS exposure among 203 nonsmoking and 61 smoking workers in 25 trucking terminals. Workers in several job groups wore personal vapor-phase nicotine samplers on their lapels for two consecutive work shifts and completed a workplace SHS exposure questionnaire at the end of the personal sampling.

Results

Median nicotine level was 0.87 μg/m³ for nonsmokers and 5.96 μg/m³ for smokers. As expected, smokers experienced higher SHS exposure duration and intensity than did nonsmokers. For nonsmokers, multiple regression analyses indicated that self-reported exposure duration combined with intensity, lack of a smoking policy as reported by workers, having a nondriver job, and lower educational level were independently associated with elevated personal nicotine levels (model R² = 0.52). Nondriver job and amount of active smoking were associated with elevated personal nicotine level in smokers, but self-reported exposure, lack of a smoking policy, and lower educational level were not.

Conclusions

Despite movements toward smoke-free laws, this population of blue-collar workers was still exposed to workplace SHS as recently as 2005. The perceived (reported by the workers), rather than the official (reported by the terminal managers), smoking policy was associated with measured SHS exposure levels among the nonsmokers. Job duties and educational level might also be important predictors of workplace SHS exposure.     

Associations of traffic related air pollutants with hospitalisation for first acute myocardial infarction: the HEAPSS study

Background

Acute myocardial infarction (AMI) is the leading cause of death attributed to cardiovascular diseases. An association between traffic related air pollution and AMI has been suggested, but the evidence is still limited.

Objectives

To evaluate in a multicentre study association between hospitalisation for first AMI and daily levels of traffic related air pollution.

Methods

The authors collected data on first AMI hospitalisations in five European cities. AMI registers were available in Augsburg and Barcelona; hospital discharge registers (HDRs) were used in Helsinki, Rome and Stockholm. NO₂, CO, PM₁₀ (particles <10 μm), and O₃ were measured at central monitoring sites. Particle number concentration (PNC), a proxy for ultrafine particles (<0.1 μm), was measured for a year in each centre, and then modelled retrospectively for the whole study period. Generalised additive models were used for statistical analyses. Age and 28 day fatality and season were considered as potential effect modifiers in the three HDR centres.

Results

Nearly 27 000 cases of first AMI were recorded. There was a suggestion of an association of the same day CO and PNC levels with AMI: RR = 1.005 (95% CI 1.000 to 1.010) per 0.2 mg/m³ and RR = 1.005 (95% CI 0.996 to 1.015) per 10000 particles/cm³, respectively. However, associations were only observed in the three cities with HDR, where power for city‐specific analyses was higher. The authors observed in these cities the most consistent associations among fatal cases aged <75 years: RR at 1 day lag for CO = 1.021 (95% CI 1.000 to 1.048) per 0.2 mg/m³, for PNC = 1.058 (95% CI 1.012 to 1.107) per 10000 particles/cm³, and for NO₂ = 1.032 (95% CI 0.998 to 1.066) per 8 μg/m³. Effects of air pollution were more pronounced during the warm than the cold season.

Conclusions

The authors found support for the hypothesis that exposure to traffic related air pollution increases the risk of AMI. Most consistent associations were observed among fatal cases aged <75 years and in the warm season.     

Leukaemia, brain tumours and exposure to extremely low frequency magnetic fields: cohort study of Swiss railway employees

Aims

To investigate the relationship between extremely low frequency magnetic field (ELF‐MF) exposure and mortality from leukaemia and brain tumour in a cohort of Swiss railway workers.

Methods

20 141 Swiss railway employees with 464 129 person‐years of follow‐up between 1972 and 2002 were studied. Mortality rates for leukaemia and brain tumour of highly exposed train drivers (21 μT average annual exposure) were compared with medium and low exposed occupational groups (i.e. station masters with an average exposure of 1 μT). In addition, individual cumulative exposure was calculated from on‐site measurements and modelling of past exposures.

Results

The hazard ratio (HR) for leukaemia mortality of train drivers was 1.43 (95% CI 0.74 to 2.77) compared with station masters. For myeloid leukaemia the HR of train drivers was 4.74 (95% CI 1.04 to 21.60) and for Hodgkin''s disease 3.29 (95% CI 0.69 to 15.63). Lymphoid leukaemia, non‐Hodgkin''s disease and brain tumour mortality were not associated with magnetic field exposure. Concordant results were obtained from analyses based on individual cumulative exposure.

Conclusions

Some evidence of an exposure–response association was found for myeloid leukaemia and Hodgkin''s disease, but not for other haematopoietic and lymphatic malignancies and brain tumours.     

Long-term use of cellular phones and brain tumours: increased risk associated with use for > or =10 years

Aim

To evaluate brain tumour risk among long‐term users of cellular telephones.

Methods

Two cohort studies and 16 case–control studies on this topic were identified. Data were scrutinised for use of mobile phone for ⩾10 years and ipsilateral exposure if presented.

Results

The cohort study was of limited value due to methodological shortcomings in the study. Of the 16 case–control studies, 11 gave results for ⩾10 years'' use or latency period. Most of these results were based on low numbers. An association with acoustic neuroma was found in four studies in the group with at least 10 years'' use of a mobile phone. No risk was found in one study, but the tumour size was significantly larger among users. Six studies gave results for malignant brain tumours in that latency group. All gave increased odd ratios (OR), especially for ipsilateral exposure. In a meta‐analysis, ipsilateral cell phone use for acoustic neuroma was OR = 2.4 (95% CI 1.1 to 5.3) and OR = 2.0, (1.2 to 3.4) for glioma using a tumour latency period of ⩾10 years.

Conclusions

Results from present studies on use of mobile phones for ⩾10 years give a consistent pattern of increased risk for acoustic neuroma and glioma. The risk is highest for ipsilateral exposure.     

Predictors of early leaving from the cotton spinning mill environment in newly hired workers

Objective

This longitudinal study aimed to identify the predictors of leaving during the first year of employment from the cotton spinning mill environment in newly hired workers.

Methods

One hundred and ninety eight consecutively appointed new employees were investigated by questionnaire, lung function test, and skin test. They were examined before employment and at the end of the 1st week, and the 1st, 3rd, 6th, and 12th month after starting work and when possible before leaving their job. 572 personal dust sampling and 191 endotoxin measurements were performed to assess the environmental exposure. For the univariate analysis χ², Student t tests, ANOVA, and Kruskall Wallis tests were used. Cox proportional hazards analysis was used to identify factors associated with leaving the job.

Results

Fifty three per cent of workers left the mill environment during their first working year. Work related lower respiratory tract symptoms reported at the third month were associated with an increase rate of leaving the industry compared to those remaining in the industry (25% v 4.8%; p<0.005). Having respiratory symptoms at the first month of work predicted those leaving the industry at some point in the next 11 months. According to the Cox model, increasing age and having work related lower respiratory tract symptoms were found to be predictors for leaving job at the first working year. Atopic status, dust and endotoxin levels, and lung function changes were not consistently predictive of workers who left the industry in the follow up period.

Conclusion

This study demonstrated that work related respiratory symptoms can predict workers likely to leave the cotton mill environment during the first year of employment, but atopy or acute lung function changes do not.     

The prognostic value of depressive symptoms, fear-avoidance, and self-efficacy for duration of lost-time benefits in workers with musculoskeletal disorders

Background

The psychological factors of depressive symptoms, fear‐avoidance, and self‐efficacy are deemed to be important in the work disability process. However, the prognostic value of these factors for time on benefit is not well understood.

Aims

To analyse the prognostic value of psychological factors for the number of days on total compensation benefit over a 12 month period.

Methods

In a longitudinal study of 187 workers receiving total compensation benefits due to musculoskeletal disorders, the prognostic value of psychological factors measured 4–5 weeks post‐injury for duration on total compensation benefit over 12 months was analysed. Cox proportional hazard regression analyses were conducted. Special emphasis was given to variable selection and to the analysis of confounding effects of potential prognostic variables.

Results

The final model indicated that increased depressive symptoms and poorer physical health significantly increase the number of days on total benefit. Confounders included in the final model were pain and fear of income loss. In the final model the impact of fear‐avoidance ceased to be significant when work related variables were included in the fully adjusted model. This illustrates that interrelationships between variables must be taken into account when building multivariate prognostic models. The addition of work related variables to the model did not result in any major changes in the adjusted model, which suggests that when measured 4–5 weeks post‐injury, psychological and physical health factors are strong predictors of time on benefits, while work conditions are less important.

Conclusion

Results suggest that the presence of depressive symptoms and poor physical health in workers on benefit due to musculoskeletal disorders increases the number of days on total compensation benefits significantly, when controlling for confounding variables.