Sleepiness, sleep, and use of sleepiness countermeasures in shift-working long-haul truck drivers.

Driver sleepiness is a prevalent phenomenon among professional drivers working unconventional and irregular hours. For compromising occupational and traffic safety, sleepiness has become one of the major conundrums of road transportation. To further elucidate the phenomenon, an on-road study canvassing the under-explored relationship between working hours and sleepiness, sleep, and use of sleepiness countermeasures during and outside statutory rest breaks was conducted. Testing the association between the outcomes and working hours, generalized estimating equations models were fitted on a data collected from 54 long-haul truck drivers (mean 38.1 ± 10.5 years, one female) volunteering in the 2-week study. Unobtrusive data-collection methods applied under naturalistic working and shift conditions included the Karolinska Sleepiness Scale (KSS) measuring sleepiness, a combination of actigraphy and sleep-log measuring sleep, and self-report questionnaire items incorporated into the sleep-log measuring the use of sleepiness countermeasures during and outside statutory rest breaks. Drivers' working hours were categorized into first and consecutive night, morning and day/evening shifts based on shift timing. The results reveal severe sleepiness (KSS≥7) was most prevalent on the first night (37.8%) and least on the morning (10.0%) shifts. Drivers slept reasonably well prior to duty hours, with main sleep being longest prior to the first night (total sleep time 7:21) and shortest prior to the morning (total sleep time 5:43) shifts. The proportion of shifts whereby drivers reported using at least one sleepiness countermeasure outside statutory rest breaks was approximately 22% units greater for the night than the non-night shifts. Compared to the day/evening shifts, the odds of severe sleepiness were greater only on the first night shifts (OR 6.4-9.1 with 95% confidence intervals, depending on the statistical model), the odds of insufficient daily sleep were higher especially prior to the consecutive night shifts (OR 3.5 with 95% confidence intervals), and the odds of using efficient sleepiness countermeasures outside statutory rest breaks were greater on the first as well as consecutive night shifts (OR 4.0-4.6 with 95% confidence intervals). No statistically significant association was found between shift type and use of efficient sleepiness countermeasures during statutory rest breaks. In all, the findings demonstrate marked differences in the occurrence of severe sleepiness at the wheel, sleep preceding duty hours, and the use of sleepiness countermeasures between different shift types. In addition, although drivers slept reasonably well in connection with different shift types, the findings imply there is still room for improvement in alertness management among this group of employees.

Quantitative EEG in occupational chronic solvent encephalopathy.

The aim of this study was to characterize the quantitative analyzed EEG (electroencephalogram) findings (qEEG) in chronic solvent encephalopathy (CSE) patients and study whether the qEEG findings associate with the duration and intensity of the solvent exposure. Also, the diagnostic value of qEEG in CSE is discussed. The EEG of 47 male CSE patients was analyzed. The laboratory's own reference EEG values of 24 healthy male subjects formed the laboratory control group. We also used an age-matched control group of 100 male blue-collar workers without occupational solvent exposure. The main finding of our study was that the power of the frontal theta band is increased in the CSE patient group compared with the laboratory control group. This suggests that the frontal cortex may be susceptible to the noxious effects of solvents. However, this difference was not seen in comparison with the matched control group, and thus, the connection with solvent effects remains uncertain. The variables indicating the level of solvent exposure did not associate with the power of the theta activity in the frontal area. Because of the small amount and unspecificity of the observed abnormalities, qEEG cannot be recommended to be used in the clinical diagnostics of solvent encephalopathy.

Kinetics of the metal components of intratracheally instilled stainless steel welding fume suspensions in rats.

The kinetics of iron, chromium, nickel, and cobalt from manual metal arc and metal inert gas stainless steel welding fumes were studied. Neutron activated welding fumes, in aqueous suspensions, were instilled intratracheally into rats. The follow up continued for up to 106 days. From both fumes, approximately 10% of the injection bolus was immediately lost into the gastrointestinal tract, to be recovered in the faeces within three days. Thereafter, a pronounced difference was seen in the kinetics of the two types of fumes. After the first day, chromium, nickel, and iron were lost from the lungs with half times of about 53, 49, and 73 days after exposure to MMA/SS fumes, whereas practically no loss could be seen in the metal components of the metal inert gas welding fumes within two months. The disposition of chromium from MMA/SS fumes closely resembled that of intratracheally instilled water soluble chromates. On the other hand, the disappearance of trivalent chromium from MIS/SS fumes was considerably slower than that of the practically water insoluble chromates, or even of trivalent chromium salts. Thus the physical characteristics of the fume appreciably affect the kinetics of the clearance of chromium compounds from the lungs.

Kinetics of nickel and chromium in rats exposed to different stainless-steel welding fumes.

The kinetics of nickel and chromium from welding fumes were studied in the rat. To study the retention, the duration of exposure was one hour per working day for one, two, three, and four weeks. For the clearance study the follow-up period after four weeks' exposure was 106 days. Multi-element chemical analysis of the fumes and dried lungs was done using instrumental neutron activation analysis, and the concentrations in the body fluids were determined by atomic absorption spectroscopy. The maximum lung retention of metal inert-gas (MIG) welding fumes was somewhat higher than that of manual metal arc (MMA) welding fumes. The estimated maximum concentrations in the lungs were 9.5 micrograms/g and 150 micrograms/g for nickel after four weeks' exposure to MMA and MIG welding fumes. The corresponding concentrations of chromium were 78 micrograms/g and 310 micrograms/g. The measured concentrations were lower, however. The amounts of nickel cleared from the lungs during the MMA and MIG exposures were 0.9 microgram and 8 micrograms. The corresponding amounts of chromium were 9.6 micrograms and 2 micrograms. Practically all of the lost metals were found in the urine, in which the excretion rates were 0.07 microgram/d (MMA) and 0.39 microgram/d (MIG) for nickel and 0.23 microgram/d (MMA) and 0.11 microgram/d (MIG) for chromium.