Zentralblatt fur Bakteriologie. 1. Abt. Originale B, Hygiene, Krankenhaushygiene, Betriebshygiene, praventive Medizin最新文献

Differences of individual reactivity and, therefore, in the strength of effect air pollution exerts in different subjects of a population under study, are well known. Several experimental and epidemiologic results point to the possibility that this phenomenon is due to variations in the defence mechanisms of the human body. Some important findings relating to this problem are: Deterioration of lung clearance by inhalation of NO2 or lead chloride; damage to alveolar macrophages by air borne particulates in vitro and in vivo; enhanced activation or synthesis of the C'3 complement fraction under the influence of air pollutants; higher frequency of enlarged tonsils and lymph nodes, of pathogenic bacteria on tonsillar surfaces, and of relatively lower lysozyme concentrations in children living in urban or industrialized areas; decreased resistance to infections, elicited by inhalation of O3 or a lead aerosol; immuno-suppressive effect of heavy metals and organic compounds; allergic reactions against quite a number of chemicals; detoxification and toxification, e.g. formation of ultimate carcinogens, of organic molecules; induction or inhibition of the metabolism of benzo(a)pyrene by particulate extracts or by CO, NO2, and lead, resp.; deficiency of DNA--repair in disease conditions predisposing to the development of cancer; tendency, in allergics, to a relatively lower incidence of cancer; adaptation to the effects of CO or SO2. These facts, and knowledge not cited here, are in favour of the existence of close connections between various defence mechanisms, air pollution, and its effects on the human organism.

Physical, chemical and bacterial qualities of total wastewaters from slaughterhouse and meat processing plants and individual departments has been followed. Obtained results are indicating the significance of wastewaters in contamination of living environment and stressing the importance of their treatment.

The large variety of qualities and quantities of raw material in numerous plants demands specific methods of processing. Each process has to guarantee full sterilization of the raw material and produce profitable products as well as to prevent as far as possible the recontamination of the products. In principle the processes are devided in the dry-rendering technology and the wet-rendering technology. The distinctive mark is the time of degreasing of the material during the process. The device that is nowadays used for the steps of sterilizing, drying and degreasing is described and the most important advantages and disadvantages are pointed out. Each technology results from a suitable combination of particular apparatusses and equipment. The eleven processes that are used in the rendering industry at present time are described with their positive and negative aspects.

Four rendering plants are responsible for the whole of the rendering processes in Belgium. The animal population is not equally spread over the country, there is a marked preponderance of the pig and poultry population in the northern part (fig 1 and 2), while cattle and horses are more equally spread. Per inhabitant about 6,5 kg cadaver and offal are rendered yearly. The offal remained relatively constant since 1970, on the contrary the weight of cadavers increased with about 50%, the pigs take the largest part of the increase (table 2). It is obvious that efforts are necessary to reduce drastically the mortality in pigs and poultry. Lowering of infection pressure in the environment could be one of the most effective measures to reduce the mortality in farm animals. On the other hand rendering plants have a specific hygienic role when only the destruction of animals infected with infectious agents submitted to legal regulations are taken in account (table 5).

In the Waste Management Program 1975 of the German Federal Government the problems of disposal of animal carcasses and rendering were specially emphasized in the working group "Animal Residues". Besides a description of the entire situation, the reasons and the problems, measures for solving the problems are concurrently listed. For the practical supervision of rendering plants by the state veterinary officer and the operational self-control in such plants a questionnaire was prepared on the basis of the law in force, which can be used as a checklist.

Although a regulation has been in force in Israel since 1930 which committed the communities to provide for knackers' yards, until some years ago packs of jackals took care of the carcass disposal. Owing to the increase of large slaughter houses for fowl some rendering plants were also erected, which however, eliminated only the waste from these plants. For this reason the government decided to build rendering plants on the European pattern and to legislate pertinent veterinary acts. In Israel 20,000 tons fish-meal is imported annually, worth millions of dollars for feeding purposes, while no attention is as yet being paid to the processing of the national raw materials.

A survey is given on the development of rendering of animal carcasses, of confiscated slaughter house material, of slaughter offall, blood and other wastes of the production of food of animal origin. The legal regulations concerning animals rendering are discussed.

Procedures for the hygienic inspection of animal rendering plants should include the bacteriological investigation of the meat meal, the bacteriological control of the used methods of disinfection of the contaminated rooms, of the transport vehicles and of the sewage of the contaminated side. Meat meal has to be free of Clostridium perfringens and Salmonellae. Clostridium perfringens is an indicator of the sterilizing effect of the rendering procedures. After an effective disinfection of rooms no gramnegative and only a small numbers of grampositive bacteria like aerobic bacilli should be demonstrable. Sewage of the contaminated side has to be free of Clostridium perfringens spores.

In Austria five carcass rendering plants are at present in operation, having the following geographical distribution: Unterfrauenhaid-Raiding (Burgenland), Tulln (Lower Austria), Regau (Upper Austria), Lantscha (Styria) and Vienna. Moreover, there are two carcass incincerators in operation, one at Zell am See (Salzburg) and another in St. Johann in Tyrol. In addition, so-called carcass burying lots still exist to some extent. Implementation of carcass disposal and pertinent regulation fall within the responsibility of the federal states (Bundesländer). For the collection and disposal of the carcasses and waste, subject to compulsory handing over, the federal state or the respective carcass-processing institution levies duties or receives some form of recompense. So far, these payments have been primarily made by the communities, or also partly by the private person or body claiming this service. According to the new regulation, the Prime Minster of a Land establishes a cost-covering tariff to disburse the costs of collection, transport and disposal, as well as to provide for the formation of reserves and the amortization. These duties now have to be paid by the owners of the material subject to compulsory delivery (principle of causation).