Stoffströme von Benzol unter besonderer Berücksichtung der Bundesrepublik Deutschland

In the Federal Republic of Germany, benzene is one of the most important basic materials for the chemical industry. Only a relatively small proportion of the pure benzene processed in the chemical industry is emitted into the environment (ca. 40t in 1991). But the substance is also a natural component of the crude oil in gasoline and is released during incomplete combustion or is formed out of other aromatic substances. The primary source of emissions, with more than 10,000 t/yr (approximately 85% of this from motor vehicles with Otto engines), is commercial motor vehicle transportation. Benzene concentrations in the environment are approximately <1 μg/m³ in rural areas, 20–30 μg/m³ near main roads (peak levels in highly urbanized regions with much traffic as high as approximately 100 μg/m³) and 7–15 μg/m³ in the vicinity of industrial polluters. It has not been possible to detect a specific trend over time during the last ten years. An increased exposure (approx. 350–27,000 μg/m³) is likely while filling the tank and within the motor vehicle (approx. 10–200 μg/m³) due to gasoline volatilization from pipes, etc. Compared to outdoor air, higher concentrations of benzene (approx, 2–11 μg/m³) are measured in the indoor air which contains additionally benzene from tobacco smoke, equipment, renovating work and heating. The primary exposure pathway of benzene in humans is inhalation. Apart from individuals with occupational exposure, smokers have the highest internal benzene burden. Measures undertaken during recent years to reduce the amount of emissions have been counteracted at least in part by the increase in motor vehicle traffic. Further measures to reduce the emissions or to change the transporttation policies must still be or have already been initiated.     

Lactatdehydrogenase

Lactate dehydrogenase is the prototype of an oligomeric, intracellular enzyme. Its primary, secondary tertiary, and quaternary structures are now well known. This fact, especially with regard to the occurrence of isoenzymes, has effected a great progress in the understanding of the structure-function relationship of enzymes. The historical development of modern enzymology is described, together with discussions of the various methods and problems of enzymology.     

Evidences for inductive properties of the micromere-RNA in sea-urchin embryos

The Science of Nature -