[Objective evaluation of visual strain in computer screen and office work by recording visually evoked cortical potentials (VECP) and determining changes in contrast sensitivity and refraction]. / Untersuchungen zum objektiven Nachweis der Beanspruchung des visuellen Systems bei Bildschirm- und Büroarbeit durch Ableitung visuell evozierter kortikaler Potentiale (VECP) und Erfassung der Anderungen von Kontrastsensitivität und Refraktion.

Visual evoked cortical potentials (VECP) elicited with checkerboard pattern reversal stimuli of high spatial frequency and low contrast were recorded. The changes in the VECP depending on the duration of task-oriented activity at video display units (VDU) and in the office were determined. The testing procedure can be used to decide on adequate recovery periods (breaks) for any visual workload and requires only a short time. We investigated 30 probands: 10 subjects tested before and after 4 h of VDU work under controlled standard conditions had statistically significant increases of latency (P < 0.001) and decreases of amplitude in VECP recordings (P < 0.05). Another 10 subjects tested at the same intervals but exposed to standard office working conditions also showed statistically significant increases of latency (P < 0.0001) and decrease of amplitude in VECP recordings (P < 0.01). The 10 control subjects tested at the same intervals spent the time between recording sessions on leisure activity (walking) and showed no significant VECP changes. Statistical evaluation was performed with Student's t-test for paired samples. Contrast sensitivity (Ginsburg test) decreased in both VDU and office groups after completion of their workload, but remained within normal limits. The maximal changes in refraction amounted to +/- 0.25 D after 4 h and +/- 0.5 D after 6 h and showed no bias. Extended periods of working at VDUs and conventional office work increase the latency and decrease the amplitude of the pattern-evoked VECP. This method can be used to determine optimal scheduling of breaks in for people working at VDUs and doing conventional office work.

Investigations concerning the standardisation of control-investigations of supply-air in air-conditioning systems in hospitals.

In the following investigation, air-germ measurements were conducted--using the Reuter-Centrifugal-Sampler (RCS) and the Sartorius-Sampler MD 3 (SAR), and using standardized nutrient-substratum and breeding conditions--in order to detect differences in the measuring process itself. The aim of the study was to find a standard for routine-measurements in hospitals. A special "Supply-Air-Box" was developed because of the known turbulences during the emission of air from the channel; in order to cut off the interference-factor during the measurements caused by the blending with the room-air. The results of the air-germ measurements showed a sufficient reproducability and a good representation of the results in differing measuring positions with both devices during repeated measurements. A marked difference between the two measuring-devices are the markedly higher CFU-numbers in the measurements using the RCS-device and the resulting higher variability of the single-values. The measurements using the supply-air-box show that--with the usual measuring position immediately in front of the supply-air grille screen or without grille screen at the channel end--a considerable part of room-air is also registered during the determination of the CFU-number because of the existing turbulences. Because of the markedly lower CFU-numbers with this procedure, new recommendations were suggested for the maximal mean CFU-number in the supply-air. Accordingly, not more than 5 CFU/m3 of air should be found with three-step-filtered supply-air in well-maintained installations for the inrestricted utilization of the rooms, and not more than a mean value of 30 CFU/m3 of air with two-step-filtered supply-air.

[Emission of microorganisms from sewage treatment plants depending upon construction differences of single structural parts]. / Die Mikroorganismen-Emissionen aus biologischen Abwasserreinigungsanlagen in Abhängigkeit von Konstruktionsunterschieden einzelner Bauteile.

In order to examine the influence exerted by the differing design of individual water treatment plant units on the emission rate of micro-organisms and the associated degree of exposure to which plant personnel is subjected, measurements were taken at three different types of treatment plants. Measurements were made using "Biotest" RCS Air Samplers. The total count of colonies was determined by means of Agar Strips GK-A (tryptic soy agar). Enterobacteriaceae were quantitatively ascertained using Agar Strips C (MacConkey agar), particular attention being paid to the determination of the coliform bacteria as faeces indicators. Agar Strips S (mannitol salt agar) were used to measure the count of staphylococci using Agar Strips HS (rosa Bengal streptomycin agar). Before taking measurements, the prevailing climatic conditions were recorded. It could be ascertained that the enclosure of the inflow area (screw conveyor pump station and aerated grit removal tank) lead to a considerable increase in the concentration of microorganisms in the air within the housing. The values dropped however, when adequate ventilation was provided. Differing oxygen in the activated sludge tanks - finebubble aeration at the tank bottom or the blowing in of air via centrifugal blowers - lead to large variations in the emission rates. However, the less the waste water is agitated, the lower the emission rates. In the case of fine-bubble aeration, rates which are also normally to be found in the "non-burdened" outside air were even recorded close to the aeration tank. In cases of centrifugal blower, the aeration tank should be covered with a shield. With this type of aeration the waste water is emitted radially towards the walls of the tank. The use of a sprinkler unit on an aeration tank equipped with centrifugal blower - to avoid foam formation on the surface of the water - does not lead to an increase in the already high emission rate. An increase in air pollution through mould fungi from waste water treatment plants could not be found. In conclusion, it can be said that different individual plant unit designs have a large influence on the concentration of micro-organisms in the ambient air of places of work of waste water treatment plant personnel. Emission rates can be limited to such a degree that, even in the immediate vicinity of the plant units, a decrease of micro-organism concentrations can be attained as comparable to the area outside the treatment plant.

[To the behaviour of cadmium and lead in children with a different cadmium or lead burden]. / Zum Verhalten von Cadmium und Blei bei Kindern mit unterschiedlicher Cadmium-oder Bleibelastung.

An epidemiological study of 413 randomly chosen children in age of 2--14 years living in an industrial town is presented. According to their place of residence they were either burdened with cadmium from a forge or with lead from the traffic. The different burden was refelcted not only in the blood lead level but also in blood cadmium level respectively. Both contaminants showed in their separate effects the same behaviour. The intensity of the absorption of lead or cadmium respectively influences not only the relationship between blood lead level or blood cadmium level and the other parameters (Pb-H, Pb-U, Cd-H, Cd-U, d-ALA-U) but also the distribution of these parameters.

[The relationships between blood lead, erythrocyte count, blood hemoglobin concentration and age in children (author's transl)]. / Uber Beziehungen zwischen Blut-Blei, Erythrocyten, Hämoglobin und dem Alter von Kinder aus einer gering mit Blei belasteten Industriekleinstadt

With increasing age of the children and increasing hemoglobin, hematocrit and serum protein levels, the lead concentrations of the blood in the children dropped. By contrast, high lead concentrations in blood correlate with low MCV and high erythrocyte values. The possible causes are discussed.

[The measurement of fibre concentrations in lung dusts (author's transl)]. / Die Messung der Faserkonzentration in Lungenstäuben

Measurements in ambient air have indicated, that air pollution contains fibrous dusts in various concentration. Moreover it seems to be necessary to get informations of the fiber content in the lungs of men. In this investigation 22 dusts, which were isolated by formamide-methode from lungs, were analysed. Methods of preparation and evaluation of the lung dust of people, which were occupational non-asbestos-exposed, are described. Fiber concentration per mg lung dust lies between 10 X 10(3) and 535 X 10(3). Most of the fibers were shorter than 10 mum. Because of the limitation of the evaluation-technique it was not possible to analyse the fibers with regard to their chemical composition.

[Blood pressure and pulse frequency during oral intake of cadmium sulfide in animal experiment (author's transl)]. / Blutdruck und Pulsfrequenz bei oraler Belastung mit Cadmiumsulfid im Tierversuch

Female wistar rats were given cadmium sulfide in various concentrations in their chow (26 mg CdS/kg feed and 52 mg tcdS/kg feed). After a three month trial no significant changes in blood pressure could be seen. The pulse frequencies showed the falling tendency with increasing weight, as already seen in healthy rats.

[External quality control measures for blood lead analysis of persons living in a high lead exposure area (author's transl)]. / Eine externe Qualitätssicherung von Blutuntersuchungen bei Personen aus einem bleibelasteten Gebiet

Analytical laboratories engaged in studies regarding the exposure of larger population groups to lead should--for the sake of better intercomparability of data--subject themselves to internal and external quality control. In this paper an example of external quality control for blood lead, ALA-D and FEP analysis by 3 institutes is given. Evaluation by correlation analysis showed satisfactory results for all 3 parameters studied. Apart from discussing the results, suggestions are made regarding conduction of realistic quality control measures for the 3 lead-dependent biological exposure parameters.

[Blood pressure and pulse frequency during oral intake of cadmium sulfide in animal experiment]. / Blutdruck und Pulsfrequenz bei oraler Belastung mit Cadmiumsulfid im Tierversuch

Female wistar rats were given cadmium sulfide in various concentrations in their chow (26 mg CdS/kg feed and 52 mg CdS/kg feed). After a three month trial no significant changes in blood pressure could be seen. The pulse frequencies showed the falling tendency with increasing weight, as already seen in healthy rats.