Sickness absence and flight type exposure in flight crew members.

BACKGROUND: Shift work research has shown that the relationship between exposure to irregular working times and sickness absence may differ between working populations. Not much is known about the prevalence of sickness absence in flight crews or about the relationship between exposure to different flight schedules and sickness absence in this population. AIMS: To examine the association between cumulative exposure to different flight types and sickness absence in flight crew members. METHODS: The study population consisted of flight crew members from a 5 year historic cohort. Flight schedule and sickness absence data were obtained from company records. The association between the cumulative exposure to different flight types and sickness absence episodes of >7 days was determined using univariate and multivariate logistic regression analyses. Adjusted models were obtained by adding potential confounders. Previous sickness absence was added to compose the fully adjusted models. RESULTS: The records of 8228 employees were analysed. The fully adjusted univariate analyses showed that the numbers of medium-haul flights and flights with time zone crossings were associated with an increase in the odds for sickness absence. The fully adjusted multivariate analyses showed no significant associations between flight types and sickness absence. CONCLUSIONS: Cumulative exposure to flight types was not independently associated with sickness absence in flight crew members when previous sickness absence was taken into account. Because sickness absence in the past can predict future absence, preventive strategies targeted at flight crew members with a history of high sickness absence may be effective.

Prevention of work-related airway allergies; summary of the advice from the Health Council of the Netherlands.

The Health Council of the Netherlands published a report in which the best procedure and method for recommending health-based occupational exposure limits (OELs) for inhaled allergens were identified by evaluating the scientific state of the art. Many respiratory disorders in the workplace arise from inhalation of substances which can cause allergy. To protect workers against respiratory allergy, various preventive measures are taken, one of them being reduction of exposure by setting legally binding standards. These are based on health-based OELs that specify a level of exposure to an airborne substance, a threshold level, below which it may reasonably be expected that there is no risk of adverse health effects. The Council is of the opinion that an OEL should prevent against allergic sensitization, as sensitization plays a crucial biological role and is a prerequisite for the development of allergy. Furthermore, the Council considers it most likely that the exposure level below which no allergic sensitization develops for most allergens is so low, that OELs are difficult to set with the current knowledge and technical feasibilities. An alternative approach is to accept exposure, which carries a small predefined risk in developing allergic sensitization. In addition, it is worth considering periodic screening of exposed workers on allergic sensitization, because timely intervention can prevent worse. The feasibility of periodic screening and what else is needed to comply with the most important criteria, should however be judged case-by-case.

Long term health complaints following the Amsterdam Air Disaster in police officers and fire-fighters.

BACKGROUND: On 4 October 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, the Netherlands. Fire-fighters and police officers assisted with the rescue work. OBJECTIVES: To examine the long term health complaints in rescue workers exposed to a disaster. METHODS: A historical cohort study was performed among police officers (n = 834) and fire-fighters (n = 334) who performed at least one disaster related task and reference groups of their non-exposed colleagues (n = 634 and n = 194, respectively). The main outcome measures included digestive, cardiovascular, musculoskeletal, nervous system, airway, skin, post-traumatic stress, fatigue, and general mental health complaints; haematological and biochemical laboratory values; and urinalysis outcomes. RESULTS: Police officers and fire-fighters who were professionally exposed to a disaster reported more physical and mental health complaints, compared to the reference groups. No clinically relevant statistically significant differences in laboratory outcomes were found. CONCLUSIONS: This study is the first to examine long term health complaints in a large sample of rescue workers exposed to a disaster in comparison to reference groups of non-exposed colleagues. Findings show that even in the long term, and in the absence of laboratory abnormalities, rescue workers report more health complaints.

Measuring sick leave: a comparison of self-reported data on sick leave and data from company records.

The objective of this study was to compare sick leave data obtained from questionnaires with data from company records. During a period of 12 months, questionnaires were completed monthly for 6 months and then at 9 and 12 months. The sensitivity and specificity of questionnaires for detecting an episode of sick leave were determined, using the company records as a reference standard. In addition, the duration of sick leave episodes reported in the two data sets was compared. In this analysis, company records were not assumed to be superior, and agreement was assessed with intraclass correlation coefficients (ICCs). The sensitivity of questionnaires for detecting an episode of sick leave was 55% (95% CI = 0.50-0.60) and the specificity 83% (95% CI = 0.72-0.94). The ICC for all episodes was 0.58 (95% CI = 0.47-0.67). The only satisfactory ICC (0.87; 95% CI = 0.74-0.93) was found for the questionnaires at 9 and 12 months. No large systematic differences were found between the duration of episodes reported in the two data sets. In conclusion, in our study, the sensitivity of questionnaires for detecting an episode of sick leave was very low. Furthermore, when episodes were recalled, there was little agreement on the duration of the episode between questionnaire data and data in the company records. Based on these results and considering the risk of missing questionnaires, data on sick leave gathered from company records are clearly preferable as an outcome measure in research.

Application of mixed-effects models for exposure assessment.

The benefits of using linear mixed-effects models for occupational exposure assessment were studied by re-analysing three data sets from two published surveys with repeated exposure measurements. The relative contributions of particular characteristics affecting exposure levels were assessed as in a multiple regression model, while controlling for the correlation between repeated measurements. While one-way ANOVA allows one only to estimate unconditioned variance components, a mixed model enables estimation of between- and within-worker variance components of exposure levels while accounting for the fixed effects of work characteristics. Consequently, we can identify the work characteristics affecting each variance component. Mixed models were applied to the data sets with repeated measurements and auxil iary information on work characteristics. The between-worker variance components were reduced by 35, 66 and 80%, respectively, in the three data sets when work characteristics were taken into account. The within-worker (day-to-day) variability was reduced only in the pig farmer data set, by 25%, when accounting for work activities. In addition, coefficients of work characteristics from the mixed model were compared with coefficients resulting from originally published multiple linear regression models. In the rubber manufacturing data, the coefficients of the mixed model showed similar relative importance, but were generally smaller than the coefficients from regression models. However, in the pig farm data, only the coefficients of work activities were somewhat reduced. The mixed model is a helpful tool for estimating factors affecting exposure and suitable variance components. Identifying the factors in the working environment that affect the between-worker variability facilitates a posteriori grouping of workers into more uniformly exposed groups. Identifying the factors that affect the within-worker variance is helpful for hazard control and in designing efficient sampling schemes with reference to time schedule.

Mechanisms of action of lumbar supports: a systematic review.

STUDY DESIGN: A systematic review and meta-analysis of studies on the putative mechanisms of action of lumbar supports in lifting activities. OBJECTIVE: To summarize the evidence bearing on the putative mechanisms of action of lumbar supports. SUMMARY OF BACKGROUND DATA: A restriction of trunk motion and a reduction in required back muscle forces in lifting are two proposed mechanisms of action of lumbar supports. Available studies on these putative mechanisms of action of lumbar supports have reported contradictory results. METHODS: A literature search for controlled studies on mechanisms of action of lumbar supports was conducted. The methodologic quality of the studies was assessed. The evidence for the two proposed mechanisms of action of lumbar supports was determined in meta-analyses. RESULTS: Thirty-three studies were selected for the review. There was evidence that lumbar supports reduce trunk motion for flexion-extension and lateral bending, with overall effect sizes of 0.70 (95% confidence interval [CI] 0.39-1. 01) and 1.13 (95% CI 0.17-2.08), respectively. The overall effect size for rotation was not statistically significant (0.69; 95% CI -0. 40-4.31). There was no evidence that lumbar supports reduce the electromyogram activity of erector spinae muscles (effect size of 0. 09; 95% CI -0.41-0.59) or increase the intra-abdominal pressure (effect size of 0.26; 95% CI -0.07-0.59). CONCLUSION: There is evidence that lumbar supports reduce trunk motion for flexion-extension and lateral bending. More research is needed on the separate outcome measures for trunk motion before definite conclusions can be drawn about the work conditions in which lumbar supports may be most effective. Studies of trunk motion at the workplace or during specified lifting tasks would be especially useful in this regard.

Oxidative DNA damage and cytogenetic effects in flight engineers exposed to cosmic radiation.

This study set out to analyze biomarkers for genotoxic events, e.g., oxidative DNA damage, chromosomal damage and hprt mutations, among flight personnel, who are known to be occupationally exposed to ionizing radiation of cosmic origin. Twenty-three flight engineers were recruited while ground personnel served as a matched control group. Cumulative radiation doses during flight were calculated on the basis of subjects' flight records assuming an exposure rate of 6 microSv per hour of flight. Oxidative DNA damage in peripheral lymphocytes from flight engineers appeared significantly increased in comparison with controls and was associated with cumulative exposure to cosmic radiation. Frequencies of peripheral lymphocyte chromosome aberrations, micronuclei and hprt mutations appeared also to be increased in flight engineers, but not significantly. It was also observed that DNA damage was higher in flight engineers with a relatively shorter flight history in comparison with flight engineers with higher cumulative exposures to radiation, suggesting adaptation to DNA damage caused by ionizing radiation. DNA repair activities measured as unscheduled DNA synthesis were clearly increased in the higher-exposed subgroup of flight engineers, and appeared significantly correlated with cumulative radiation dose, as well as inversely with oxidative DNA damage. The implications for cancer risk assessment in relation to exposure to cosmic radiation are discussed.

Risk factors for back pain incidence in industry: a prospective study.

The objective of this study was to examine the relationship between physical and psychological risk factors on the one hand, and the occurrence of new episodes of back pain on the other hand. A prospective study was conducted with 12 months follow-up by means of self-administered questionnaires. The study took place in the Cargo Department of a major Dutch airline company. The subjects for this study were 270 workers involved in heavy physical work. Only workers without back pain at baseline were included. Self-reported back pain and sick leave due to back pain during the follow-up period were measured. Of the 238 workers included in the analysis, 73 (31%) developed a new episode of back pain during the follow-up period, and 27 (11%) subjects reported sick leave due to back pain. Multiple logistic regression analysis showed that the history of back pain was the best predictor for the occurrence of a new episode of back pain during follow-up (OR 9.8; 95% CI 2.8-34.4 for subjects who had back pain more than twice in the past year). Low job satisfaction was also associated with an increased risk for the occurrence of back pain during follow-up (OR 1.2; 95% CI 1.01-1.4). Riding a forklift truck appeared to be a protective factor for the occurrence of back pain (OR 0.7; 95% CI 0.5-0.99). In this study the best predictors for the occurrence of back pain were the history of back complaints and low job satisfaction. Although it needs to be confirmed by future intervention studies, the results indicate that increasing job satisfaction may be a successful (co-)intervention for the prevention of back pain at the workplace.

Lumbar supports and education for the prevention of low back pain in industry: a randomized controlled trial.

CONTEXT: Low back pain is a frequent and costly health problem. Prevention of low back pain is important both for the individual patient and from an economic perspective. OBJECTIVE: To assess the efficacy of lumbar supports and education in the prevention of low back pain in industry. DESIGN: A randomized controlled trial with a factorial design. SETTING: The cargo department of an airline company in the Netherlands. PARTICIPANTS: A total of 312 workers were randomized, of whom 282 were available for the 6-month follow-up. INTERVENTIONS: Subjects were randomly assigned to 4 groups: (1) education (lifting instructions) and lumbar support, (2) education, (3) lumbar support, and (4) no intervention. Education consisted of 3 group sessions on lifting techniques with a total duration of 5 hours. Lumbar supports were recommended to be used during working hours for 6 months. MAIN OUTCOME MEASURES: Low back pain incidence and sick leave because of back pain during the 6-month intervention period. RESULTS: Compliance with wearing the lumbar support at least half the time was 43%. In the 282 subjects for whom data were available, no statistically significant differences in back pain incidence (48 [36%] of 134 with lumbar support vs 51 [34%] of 148 without, P=.81) or in sick leave because of low back pain (mean, 0.4 days per month with lumbar support vs 0.4 days without, P=.52) were found among the intervention groups. In a subgroup of subjects with low back pain at baseline, lumbar supports reduced the number of days with low back pain per month (median, 1.2 vs 6.5 days per month; P=.03). CONCLUSIONS: Overall, lumbar supports or education did not lead to a reduction in low back pain incidence or sick leave. The results of the subgroup analysis need to be confirmed by future research. Based on our results, the use of education or lumbar supports cannot be recommended in the prevention of low back pain in industry.

A systematic review of controlled clinical trials on the prevention of back pain in industry.

OBJECTIVE: To assess the effectiveness of lumbar supports, education, and exercise in the prevention of back pain in industry. METHODS: A computerised search for controlled clinical trials was conducted. A criteria list was used to assess the methodological quality of the studies. The available evidence for the effectiveness of the interventions was graded with a rating system for the level of evidence. Effect sizes of individual studies were combined if the studies were sufficiently similar. RESULTS: 11 studies were identified for the review. The methodological quality of all studies was low, with a maximum score of three out of seven for internal validity. There was no evidence for the effectiveness of lumbar supports due to contradictory outcomes of the studies. Five of the six studies on education reported no effect. Thus there is limited evidence that education does not help to prevent back pain. All three studies on exercise reported a positive result, indicating limited evidence for the effectiveness of exercise. The combined effect size for exercise was 0.53, which is a medium sized effect. CONCLUSIONS: Although widely used, there is little evaluative research on the preventive measures studied here. The review showed that there is limited evidence that exercise has some effect in the prevention of back pain and that education is not effective. No conclusive evidence was found for or against the effectiveness of lumbar supports. Research of higher methodological quality is needed before firm conclusions on the effectiveness of lumbar supports, education, and exercise in the prevention of back pain in industry can be drawn.

Dust- and endotoxin-related acute lung function changes and work-related symptoms in workers in the animal feed industry.

Reported respiratory and related symptoms during work were compared between 265 exposed animal feed workers and a control group consisting of 175 external controls and nonexposed workers in the animal feed industry. Symptoms indicating respiratory and nasal irritation were significantly increased in the animal feed workers. Prevalences ranged from 9% (cough) to 21% (sneezing). Reported cough after work was also significantly increased. In 119 workers, a total of 457 across-shift spirometric lung function changes were measured. Almost all lung function variables showed a decrease during the work shift, as could be expected since the circadian rhythm is in a downward phase during the measurement period (2 p.m.-10 p.m.). When the workers were grouped into dust and endotoxin exposure categories according to their job titles, and exposure-response trend was seen for maximum mid-expiratory flow (MMEF) and maximum expiratory flow rate at 50% of vital capacity (MEF50). The effect of endotoxin was stronger than that of dust, both in magnitude and significance. For the same lung function variables and for forced expiratory volume in 1 second (FEV1) and MEF25, a significant across-week change was also detected. The results of this study are in concordance with other studies that indicate acute effects on lung function and elevated prevalences of respiratory symptoms during work caused by exposure to grain dust.

Dust-related decline in lung function among animal feed workers.

The study describes results of the first part of a follow-up study among 50 animal feed and grain elevator workers. The initial results suggest that the change in lung function over a 5 year period is related to the dust exposure. Workers in the high exposure category showed a greater decline in lung function than workers in the low exposure category. The decline in lung function was strongest for workers who were low exposed at the beginning of the study and who became high exposed during the follow-up period.

Dust- and endotoxin-related respiratory effects in the animal feed industry.

A cross-sectional study of 315 animal feed workers was undertaken in 14 animal feed mills in the Netherlands. Primary aims were to explore relationships between exposure to organic dust and respiratory symptoms and chronic lung function changes. The study comprised monitoring dust and endotoxin exposure, spirometric lung function measurements (FVC, FEV1, mean midexpiratory flow, and flow-volume parameters) and a questionnaire for respiratory symptoms. The exposure was measured in two periods, during spring and autumn. The average 8-h personal inspirable dust exposure was 9 mg/m3 grain dust (range, 0.2 to 150 mg/m3) and 25 ng/m3 endotoxin (range, 0.2 to 470 ng/m3) based on 530 personal dust measurements. On the basis of these measurements and the occupational history of the workers, the number of years "worked in dust" and an estimate of the cumulative dust and endotoxin exposure were calculated. The prevalence of most chronic respiratory symptoms tended to decrease with increasing years of exposure. The "healthy worker effect" is probably responsible for this finding. In general, a strong negative association between most of the exposure variables and lung function was found. The endotoxin exposure was more strongly related to decreases in lung function than the dust exposure. The estimated effects of an average (cumulative) endotoxin exposure on lung function were greater, with a higher statistical significance, than for an exposure to dust. These results suggest that endotoxin exposure is an important factor in the development of respiratory impairment. The lung function changes occur at endotoxin levels ranging from 0.2 to 470 ng/m3.

Exposure to dust, endotoxins, and fungi in the animal feed industry.

In the Dutch animal feed industry, approximately 6000 workers are exposed to organic dust, originating mainly from raw materials such as grain, pulses (peas and beans), and waste products from the vegetable oil and starch industries. In this study, 79 stationary dust samples and 530 personal dust samples from eight animal feed production facilities were analyzed. The stationary total dust samples showed gravimetric concentrations ranging from 0.2 to 25 mg/m3 (geometric mean [GM] 1.3 mg/m3). Concentrations of smaller particle fractions (respirable, thoracic, and inspirable dust) were considerably lower. Personal inspirable dust concentrations were considerably higher than stationary concentrations and were strongly related to job titles. Pooled personal inspirable dust concentrations ranged from 0.2 to 450 mg/m3 (GM = 2.4 mg/m3). After adjusting for differences between inspirable and total dust, 25% of the measurements exceeded the Dutch maximum allowed concentration (MAC) for total nuisance dust (10 mg/m3) and 42% exceeded the American Conference of Governmental Industrial Hygienists' threshold limit value for grain dust (4 mg/m3). Endotoxin concentrations ranged from 0.2 to 1870 ng/m3 inspirable dust (GM = 5.1 ng/m3). Endotoxin appeared to be less prevalent in respirable dust than in larger dust fractions. Concentrations in dust appeared to be related to stages in the production process. Colony-forming units (cfu) of fungi ranged from 130 to 15,300 cfu/m3 (GM = 2300 cfu/m3) and were in parallel measurements more strongly related to endotoxin concentrations than to dust concentrations. Clearly, workers in the Dutch animal feed industry are frequently exposed to dust levels above recommended Dutch and American levels. Exposure levels to endotoxin and to fungi are quantified.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of airborne microorganisms with the lung function and leucocyte levels of workers with a history of humidifier fever.

An influenza-like illness appeared recently among workers in a plant processing synthetic yarn. A humidifier, a cold-water spraying system, was the suspected cause. Lung function changes over the day and week and changes in blood leucocytes were studied among the workers from the suspected department and two reference populations. Exposure to colony-forming units of bacteria and fungi and to endotoxins was also monitored. The workers from the suspected department had statistically significantly lower lung functions on the first workday of the week than the referents. Their blood leucocytes were also raised statistically significantly. The exposure to fungi, bacteria, and endotoxins differed significantly between the various departments, but the measured levels were low. It was concluded that the observed effects were suggestive of a "Monday morning fever" type of reaction and that adverse effects occurred at exposure levels lower than those found to date in the literature.

Enumeration of viable fungi in occupational environments: a comparison of samplers and media.

The performance of sampling for fungi using four widely used microbiological air sampling devices and three broad spectrum media was compared in seven occupational settings. Total colony forming units counts ranged from 10 to 3700 CFU/m3. The sampling efficiencies of the Andersen N-6 sampler, slit sampler, and Reuter centrifugal air sampler (RCS) were comparable, whereas the SAS sampler underestimated CFU counts by approximately 50%. The correlation between the RCS results and the other three samplers used was lower compared to their mutual correlations. There were no large differences in performance of the three media tested: malt extract agar, dichloran glycerol (18) agar, and dichloran rose bengal chloramphenicol agar. Coefficients of variation of duplicate samples were large compared to commonly used methods for sampling dust and chemicals. It is concluded that the N-6 and slit sampler perform best, although RCS is useful in probes because it is easy to handle. The three media tested yielded similar results. Further testing of DG-18 is recommended, as it inhibits fast growing genera and, thus, counting colonies is easier.

Lung function of welders of zinc-coated mild steel: cross-sectional analysis and changes over five consecutive work shifts.

Spirometric lung-function measurements were conducted 5 days before and after the work shift of 11 welders of zinc-coated steel, ten nonwelders who were indirectly exposed to welding fumes, and 17 controls. The exposure to dust and zinc of all participants was monitored personally using PAS-6 samplers. Geometric mean concentrations for welders were 0.91 mg/m3 (dust) and 34.0 micrograms/m3 (zinc). Cross-sectional analysis of Monday morning values showed no differences in lung-function parameters between groups. However, the number of years the participants were engaged in welding was of borderline statistical significance and correlated negatively with values of FEV1 and FEV1/FVC. Changes in lung function over a work shift or a working week were not related to the exposure level.