Rate of occupational accidents in the mining industry since 1950--a successful approach to prevention policy

This paper deals with the decrease in the rate of accident insurance claims in the German mining industry over the last five decades. It intends to show that this process is above all the result of a prevention policy where companies and the body responsible for the legal accident insurance in the mining industry, the Bergbau-Berufsgenossenschaft (BBG), work hand in hand. A system like the German accident insurance scheme, combining prevention, rehabilitation, and compensation, enables successful and modern safety and health measures.     

Biodegradation behavior and material properties of aliphatic/aromatic polyesters of commercial importance

Copolyesters of aliphatic monomers with a defined amount of terephthalic acid recently have been shown to be biodegradable. This group of plastic materials exhibits very interesting material properties with regard to their technical application potential. A tensile strength of 25 N/mm² combined with elongations at break up to 1500% was achieved for BTA materials. Melting points varied from 80 to 140‡C. Biodegradation rate under compositing conditions were determined, showing typical erosion rates of films, in the range of 5 to 10 Μm/week. The material properties and the degradation rate as well can be adjusted by the copolymer composition. Stretching of the polymer in the cold state leads to 10-fold higher mechanical strength of the material. The polyester chain can be extended to high molar masses, resulting in melt viscosities suitable, e.g., for melt below extrusion.     

Pigeon homing: new airbag experiments to assess the role of olfactory information for pigeon navigation

Summary In three series of experiments we assessed the effects of olfactory and non-olfactory information collected en route or at the release site on the initial orientation of homing pigeons. In the first experiment, pigeons were transported in open crates to two sites located in opposite directions from the home loft. They were left at the site for 1 h, then put into airtight containers filled with air from that site and brought back to the loft. From there, controls were transported back to the original site. Experimentals were transported to the opposite site. Upon arrival at the site, the olfactory mucosae of both groups were anesthetized with Gingicain. Thus in this experiment, control and experimental pigeons were exposed to different olfactory as well as to different non-olfactory information during displacement and at the site. In the second series, controls and experimentals were treated as in the first experiment, except that they were enclosed in the airtight containers at the very beginning of the experiment and were ventilated with synthetic air until arrival at the final release site. This treatment excluded the possibility to perceive olfactory information en route or at the site. In this series, the two groups differed only with respect to non-olfactory information perceived during displacement and/or at the release site. In the third series, we exposed pigeons at the loft to air collected either at the later release site (controls) or to air collected at a site located in opposite direction of the home loft (experimentals). Here the two groups differed only with respect to their exposure to air of different origin. In all three series, the pooled controls showed a directional preference that was statistically indistinguishable from the home direction. All three experimental groups were disoriented. In the first two series, the differences in the initial orientation of control and experimental pigeons were highly significant. In the third experiment, there was only very weak statistical evidence for a difference between controls and experimentals. These results suggest that more than one factor is involved in the pigeons' navigation system. According to the present experiment with synthetic air, pigeons probably gather and process non-olfactory information during the first part of their transport from the home loft to the release site. Thus, some kind of, in this case non-olfactory, route reversal seems to be involved in the homing process. In addition, the experiment involving only manipulations of airborne information indicated some olfactory component. Previous experiments at our loft did not result in disorientation of the pigeons if either only the access to airborne information had been removed or when otherwise unmanipulated pigeons had been transported in detours to the final release site. Therefore, we assume that our pigeons' navigation system relies on several cues. Deletion of one cue can be compensated by other information. Often the initial orientation of our pigeons is disturbed only when at least one cue is removed and another one provides false information.     

The territoriality threshold: a model for mutual avoidance in dragonfly mating systems

Summary In anisopteran dragonflies a variety of mating systems occurs. Male strategies range from patrolling without site attachment to territorial behaviour with pronounced residentiality. Conceiving site attachment as a strategy of mutual avoidance that reduces the energy spent in intermale fights, we develop a model for the cost and benefit of territoriality. This model suggests that high male density, high inter-male aggressiveness, and short duration of female visits at the mating place will strongly favour localization of males at the mating place and may thus trigger the evolution of territoriality. The predictions of our model are supported by field observations of several dragonfly species.died July 27, 1986     

Relationship between different size classes of particulate matter and meteorology in three European cities

Evidence on the correlation between particle mass and (ultrafine) particle number concentrations is limited. Winter- and spring-time measurements of urban background air pollution were performed in Amsterdam (The Netherlands), Erfurt (Germany) and Helsinki (Finland), within the framework of the EU funded ULTRA study. Daily average concentrations of ambient particulate matter with a 50% cut off of 2.5 microm (PM2.5), total particle number concentrations and particle number concentrations in different size classes were collected at fixed monitoring sites. The aim of this paper is to assess differences in particle concentrations in several size classes across cities, the correlation between different particle fractions and to assess the differential impact of meteorological factors on their concentrations. The medians of ultrafine particle number concentrations were similar across the three cities (range 15.1 x 10(3)-18.3 x 10(3) counts cm(-3)). Within the ultrafine particle fraction, the sub fraction (10-30 nm) made a higher contribution to particle number concentrations in Erfurt than in Helsinki and Amsterdam. Larger differences across the cities were found for PM2.5(range 11-17 microg m(-3)). PM2.5 and ultrafine particle concentrations were weakly (Amsterdam, Helsinki) to moderately (Erfurt) correlated. The inconsistent correlation for PM2.5 and ultrafine particle concentrations between the three cities was partly explained by the larger impact of more local sources from the city on ultrafine particle concentrations than on PM2.5, suggesting that the upwind or downwind location of the measuring site in regard to potential particle sources has to be considered. Also, relationship with wind direction and meteorological data differed, suggesting that particle number and particle mass are two separate indicators of airborne particulate matter. Both decreased with increasing wind speed, but ultrafine particle number counts consistently decreased with increasing relative humidity, whereas PM2.5 increased with increasing barometric pressure. Within the ultrafine particle mode, nucleation mode (10-30 nm) and Aitken mode (30-100 nm) had distinctly different relationships with accumulation mode particles and weather conditions. Since the composition of these particle fractions also differs, it is of interest to test in future epidemiological studies whether they have different health effects.     

Seasonal variability of endotoxin in ambient fine particulate matter

Endotoxin is a toxic, pro-inflammatory compound that has been detected in indoor air and dust in homes and occupational settings, and also in outdoor air. Data on the outdoor sampling of endotoxin are limited. Currently, little is known about the seasonal variation and influence of temperature on outdoor endotoxin levels. In the present study, we report endotoxin levels in fine fraction particulate matter with a 50% aerodynamic cutoff diameter of 2.5 microm (PM2.5) and describe the seasonal variation of endotoxin in Munich, Germany. In 1999-2000, PM2.5 was collected at forty outdoor monitoring sites across Munich. Approximately four samples were collected at each site for a total of 158 samples. Endotoxin concentrations in the PM2.5 samples were determined using the kinetic chromogenic Limulus Amebocyte Lysate (LAL) assay. The geometric mean endotoxin concentration was 1.07 EU mg PM2.5(-1) (95% C.I.: 0.915-1.251) or 0.015 EU m(-3) of sampled air (95% C.I.: 0.013-0.018). Munich endotoxin levels were significantly related to ambient temperature (p < 0.0001) and percent relative humidity (p < 0.0001). Sampling periods with higher average temperatures yielded higher levels of endotoxin in PM2.5 (r = 0.641), whereas decreases in percent relative humidity were associated with increased endotoxin levels in PM2.5 (r = -0.388). Endotoxin levels were significantly higher during the warmer seasons of spring [means ratio (MR): 2.5-2.7] and summer (MR: 2.1-3.0) than during winter. Although temperature and relative humidity do not explain all of the variability in endotoxin levels, their effects were significant in our data set. Temperature effects and seasonal variation of endotoxin should be considered in future studies of outdoor endotoxin.     

Indoor and outdoor air concentrations of BTEX and NO2: correlation of repeated measurements

Studies on health effects of air pollutants ideally define exposure through the collection of air samples in the participants' homes. Concentrations derived from these samples are then considered as an estimate for the average concentration of air pollutants in the homes. Conclusions drawn from such studies therefore depend very much on the validity of the measured air pollution concentrations. In this paper we analysed repeated BTEX and NO(2) measurements with a time period of several months lying between the two conducted home visits. We investigated the variability of their concentrations over time by determining correlation coefficients and calculating within- and between-home variances. Our population consisted of 631 homes of participants from two cohort studies within the framework of the German study on Indoor Factors and Genetics in Asthma. Air pollutants were measured using passive samplers both indoors and outdoors. The measured BTEX concentrations were poorly correlated, with Pearson's correlation coefficient r ranging from -0.19 to 0.27. Additionally, a considerable seasonal effect could be observed. A higher correlation was found for the NO(2) concentrations with r ranging between 0.24 and 0.55. For the BTEX, the between-home variance was bigger than the within-home variance, for NO(2) both variances were of about the same order. Our results indicate that in a setting of moderate climate like in Germany, the variability of BTEX and NO(2) concentrations over time is high and a single measurement is a poor surrogate for the long-term concentrations of these air pollutants.