Transportation disasters--a review.
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Accidents↗
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Artifact due to B(0) fluctuations in fMRI: correction using the k-space central line.
Magnetic resonance experiments require the main magnetic field, B(0), to remain very stable. Several external sources, such as moving ferromagnetic objects and/or changing electromagnetic fields, can significantly change the value of B(0) over time. This work describes an apparent displacement along the phase-encoding axis caused by a variation in B(0). This artifact was observed in fMRI images acquired with EPI. The effect was characterized and tested using an immobile phantom. The image displacement motion along the phase-encoding axis closely followed the changes in B(0). The phase of the central line in the Fourier space was successfully used to correct this artifact. Fluctuations in B(0) may result in artifacts that mimic subject head motion, and must be appropriately corrected. Magn Reson Med 46:198-201, 2001.
Algorithms↗
Modelling the leaching of imazapyr in a railway embankment.
The use of herbicides on railway tracks is known to present a risk to groundwater, but little is known of the mechanisms influencing leaching through the coarse material used to construct railway embankments. Therefore, in the present study, four different models based on the convection-dispersion equation (CDE) were compared with previously reported field data on the leaching of imazapyr. In particular, the significance of non-equilibrium processes was investigated by comparing different CDE formulations accounting for preferential finger flow, particle-facilitated transport and kinetic sorption. The traditional CDE assuming 'local equilibrium' based on 24 h batch sorption data gave poor results (model efficiency - 1.1). It strongly underestimated leaching of imazapyr in the first 4 months following application, thus confirming the importance of non-equilibrium transport processes. Accounting for short-term sorption kinetics made little difference, giving similar results to the 'local equilibrium' CDE simulation. A simulation accounting for particle-facilitated transport could accurately match this accelerated transport, and also gave the best overall fit to the data (model efficiency 0.76). However, not even this model could match the long-term retention of imazapyr residues observed close to the soil surface more than 1 year after application, and it also underestimated the time of breakthrough to groundwater. This strongly suggests that a long-term retention/sorption process not included in any of the models tested (i.e. sorption hysteresis or bound residues) acted to retard leaching. The formation of 'protected' residues was also indicated by a much slower degradation of imazapyr more than 1 year after application. Industry.
Convection↗
Herbicide loss following application to a railway.
Railways have been identified as a potential source of herbicides detected in surface and groundwaters, but there are few data to support this theory. Two studies were undertaken to investigate the fate of herbicides applied to railway trackbeds: a pilot study in a section of a disused, but intact, cutting where runoff and throughflow were sampled from trenches adjacent to the treated area, and a larger scale study on 0.75 km of embankment where surface water from the drainage ditch at the base of the embankment and groundwater were sampled. In the pilot study, peak concentrations of atrazine, diuron and glyphosate (1280, 210 and 15 microg litre(-1) respectively) were detected 6days after treatment (DAT). Oxadiazon, oryzalin and isoxaben were not detected above their limits of quantification. Lower concentrations were detected 81 DAT (10 and 0.8 microg litre(-1) of atrazine and glyphosate respectively). In the larger scale study, herbicides were not detected, in either the surface water or groundwater, at concentrations above the limit of detection that could be attributed to application to the railway. Rainfall volume and depth to sampling point may partly explain the different results obtained from the two studies. The findings are compared with herbicide losses from other 'hard surfaces'.
Environmental Monitoring↗
Use of imazapyr against Equisetum arvense on Swedish railway tracks.
Since glyphosate has been used extensively for weed control in Swedish railway tracks, common horsetail (Equisetum arvense L), previously relatively rare, has become very common. Glyphosate, although effective against most other weeds found on railway tracks, gives poor control of E. arvense, so that heavy infestation with this weed is now common. Imazapyr (applied as a 250g AE litre(-1) SL, Arsenal) has controlled E. arvense, but is known to be very mobile. Adequate control of the weed requires application of > or = 4 litres ha(-1) of imazapyr SL but environmental factors preclude the use of > 2 litres ha(-1). A suitable strategy was found to be one application of imazapyr SL at 2 litres ha(-1) in each of two successive years but best weed control was obtained by supplementing imazapyr in the first year with glyphosate 360 g AE litre(-1) SL (RoundUp Bio) at 3 litres ha(-1).
Adsorption↗
The fate of imazapyr in a Swedish railway embankment.
The long-term fate of the herbicide imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid] applied to a Swedish railway embankment was studied. Imazapyr was applied at 750 and 1500 g ha(-1) by a spraying train used for full-scale herbicide treatment operations. Soil and groundwater were sampled twice a year for 8 years after application of the herbicide, and the dissipation of imazapyr was studied by HPLC analysis of the residues in soil and groundwater. A clean-up procedure including solid-phase extraction was performed prior to detection by HPLC. Recoveries of imazapyr from soil and water samples were 76-98% and 61-90%, respectively, and detection levels were 0.003 mg kg(-1) and 0.05 microg litre(-1), respectively. Sorption, desorption and microbial amount and activity were also measured at the two locations. The organic matter content correlated positively and the pH negatively to the adsorption of imazapyr on soil, and increasing organic matter contents decreased desorption. Apart from the 0-10-cm top layers of both sites, the microbial amount and activity were small. The main proportion of imazapyr was found in the upper 30 cm of the soil, and degraded with a half-life in the range 67-144 days. Small amounts were transported to lower soil layers and to the groundwater in proportion to the amounts applied. Traces of imazapyr were detected in the groundwater even 8years after application. It was concluded that environmental risks from the use of herbicides on railway embankments could be reduced by including adsorption layers in the embankment during their construction and by reducing the dose of the herbicide used.
Adsorption↗
Microbial biomass and activity on railway track and embankments.
The spatial distribution of microbial biomass and microbial activity was studied in two Swedish railway embankments (located close to Mora and Nässjö). Basal respiration and substrate-induced respiration (SIR) as well as the active (r) and dormant (K) fractions of the microbial biomass were determined in samples taken from the surface layer of the ballast. The SIR, r, K and basal respiration values were all of an overall low magnitude, but were highly variable over short distances on the track. Both the biomass and basal respiration were higher on the sides of the embankment than in the middle of the tracks. SIR, K and basal respiration were correlated to the organic matter content as measured by loss on ignition, whereas r was not. None of the parameters correlated with pH. It is proposed that organic matter content could be used as a predictor for microbial biomass in railway embankments.
Bacteria↗
The Pleistocene site of Gran Dolina, Sierra de Atapuerca, Spain: a history of the archaeological investigations.
Gran Dolina is part of an archaeological and paleontological complex located in the Sierra de Atapuerca karstic system (Burgos, Spain). The Trinchera del Ferrocarril sites were discovered as a consequence of the construction of a railway for the transport of minerals at the end of the nineteenth century. The systematic excavation of the upper Gran Dolina levels was initiated in 1981. In 1993, a 6 m(2)biostratigraphic survey pit was started, reaching level TD6 in 1994. This level was excavated during four consecutive years, yielding human fossils, identified as Homo antecessor, in association with lithic and faunal remains, dating to more than 0.78 m.y.a.
Animals↗
Cancer incidence among male railway engine-drivers and conductors in Sweden, 1976-90.
During recent years, the relationship between exposure to magnetic fields and cancer has attracted increasing interest. In Sweden, train personnel are exposed to comparatively strong magnetic fields in their work. The aim of the present study was to investigate cancer incidence, particularly leukemia and brain tumors, among male railway engine drivers and conductors, respectively, and to compare their cancer incidence with that of the general male population. The study population comprised all male railway engine drivers (n = 7,466) and conductors (n = 2,272) who were ever employed at the Swedish State Railways during the period 1976-90. The study population was observed with regard to cancer incidence by means of the National Cancer Register for the period 1976-90. The total cancer incidence (all tumors included) among railway engine drivers was lower than in the general Swedish population. An increased incidence of lymphocytic leukemia was observed among railway engine drivers and conductors combined (relative risk = 2.3; 95 percent confidence interval = 1.3-3.2), with the same point estimate for both occupational groups. For brain tumor (astrocytoma), the observed relative risk was close to one. The study provides evidence of an excess risk of lymphocytic leukemia in railway engine drivers and conductors, workers with known occupational exposure to magnetic fields.
Adult↗
Serosurvey of Leptospira agglutinins among railway employees in the National Railway Compartments of Bologna and Venice.
An epidemiological investigation was performed to evaluate the prevalence of anti-leptospiral agglutinins within a selected population: the railway workers of the Italian Railway Compartments of Bologna and Venice. Leptospira infection prevalence was found to be 10.38%, which represents the highest frequency ever reported in Italy. There was a significantly higher prevalence of agglutinins among the staff of the Railway Compartment of Venice. A clear prevalence of the bratislava serovar was registered, followed by the australis serovar and the icterohaemorrhagiae serovar. The influence of different kinds of railway work and that of supposed risk factors, such as hobbies and housing conditions, together with the influence of the ABO blood groups on the distribution of Leptospira agglutinins, are discussed.
ABO Blood-Group System↗
Occupational performance of a paced secondary task under conditions of sensory deprivation. I. Heart rate changes in train drivers as a result of monotony.
Twelve experienced train drivers were asked to operate the train function safety circuit (SIFA)--a paced secondary motor task which is expected to guarantee the driver's fitness for service on engines of the German Federal Railway--under laboratory conditions of extreme monotony. In spite of massive decreases in vigilance as shown by theta-activity in the EEG, all subjects were able to operate the device without major errors. A prerequisite for adequate performance is an EEG-defined arousal reaction, which is synchronized with the SIFA cycles. For 7 subjects the time-related cross-correlation coefficients between SIFA operation, alpha-activity (indicative of alertness), theta-activity (indicative of reduced vigilance), and heart rate were calculated. The central-nervous arousal found in the EEG corresponded to distinct increases in heart rate. The moments of SIFA operation after phases of light sleep correlated significantly and positively with increases in heart rate. These increases constituted a physiological overcompensation as far as the physical readiness was concerned which reached its peak after the task had been performed satisfactorily, constituting additional and superfluous occupational stress. The results of this study indicate clearly that monotony stress is not a result of occupational monotony itself, but the result of the physiological effort which is required in order to regain a level of alterness which allows adequate performance under monotonous conditions.
Electroencephalography↗
Irregularity of working hours in railway workers and types of complaints.
Seventy-three permanent morning workers, 33 three-shift workers and 43 workers with irregular working schedules (roster) filled out a questionnaire on sleep, well-being and health complaints. The frequency of sick leave tended to be smaller in workers in the roster group. However, in this group health was rated "poor" more often; digestive, respiratory, osteoarticular and nervous symptoms as well as sleep difficulties were more frequently reported. In the day work and shift group, ratings of sleep quality were higher on days of rest than on working days but not in the roster group. This suggests that a worker does not at present get enough non-work days for a complete short-term recovery. In contrast, the length of sleep reported did not differ among groups. The gap between the subjective assessment of health and the actual frequency of sick leave corresponded with the irregularity of the working schedule.
Absenteeism↗
Less than 24 hour pseudo-periodicity in work schedules of train drivers, in relation to their sleep.
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Adult↗
[Lead in the ecological system along the express highway].
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Biological Transport↗
Incidence of selected cancers in Swedish railway workers, 1961-79.
Among all Swedish men, 20 to 64 years of age and employed in 1960, railway workers were selected and compared with the population at large, concerning the incidence of leukemia, lymphoma, tumors of the brain, breast, and the pituitary gland. The study was a re-analysis of the 1961-79 incidence data previously showing no increase in risk for leukemia and brain tumors for railway workers. In the present study, follow-up was divided into two 10-year periods, and elevated relative risks (RR) were found for the first decade. For the first decade, engine drivers and conductors combined had an RR of chronic lymphocytic leukemia, acute myeloid leukemia, and lymphoma of 1.9 (95 percent confidence interval [CI] = 0.9-4.0), 1.4 (CI = 0.4-4.3), and 1.0 (CI = 0.5-1.9), respectively. For all brain tumors, the RR was 1.2 (CI = 0.8-1.9), with a higher risk estimate for those below age 30 (RR = 12.2, CI = 2.8-52.5). Three cases of breast cancer and nine cases of tumors of the pituitary gland occurred among engine drivers and conductors, corresponding to RRs of 4.9 (CI = 1.6-11.8) and 3.2 (CI = 1.6-6.2), respectively. Work on trains entails extremely high exposure to low frequency magnetic fields (EMF). The results give some support to the hypothesis of an association between EMF and certain types of cancers. The outcome for the pituitary gland, being a focal point of hormonal regulation, suggests a hormonal link.
Acute Disease↗
Cancer in Swedish railway workers.
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Electromagnetic Fields↗
[Sleep disturbance caused by noise].
This contribution is a state-of-the-art of recent knowledge regarding effects from environmental noise on sleep and proposes acoustic thresholds likely to help public authorities in setting up regulations. It recalls physiological sleep aspects and the cyclic organization of the various stages; then it examines noise effects, principally those arising from road traffic, planes and trains. Such effects are firstly considered as changes in sleep organization during night. It is noted that laboratory and home experiments lead to the same conclusions: duration of deep sleep is appreciably reduced for younger people, while the dream phase is disturbed for older people. These disturbances are associated with an average energetic level Leq. Then partial effects are investigated, either electro-encephalographic or cardiac; these effects are more especially associated with isolated acoustic phenomena and determined from the noise peak level. Other variables, e.g. back noise, phenomena number per period, interval between two noises, have an effect on probability of a local phenomenon which can be connected to a given peak level. The conclusion is that two acoustic values must be retained for considering sleep disturbances: the first one is the energetic level inside the room, with a comfort threshold of 35 dB(A) by night, and the second one is the lowest peak level which should not exceed 50 dB(A).
Adult↗
[Occupational medicine studies of train conductors and switchmen of the Federal Swiss Railway].
Railway controllers and points men of the Swiss Railways retire more often prematurely because of medical reasons than civil servants. A pilot study on 120 controllers and 60 points men revealed adverse effects of the irregular working hours as well as of mental loads. Furthermore, the controllers disclose symptoms and signs caused by physical and environmental loads.
Alcohol Drinking↗