858 research outputs found
Toxicological comments to the discussion about REACH
No full textIt is the ultimate goal of the intended REACH process (Registration, Evaluation and Authorization of Chemicals) of the European Union to identify substances of hazardous properties and to evaluate the risks of human and environmental exposure. During the last few months there has been a controversial discussion as to what extent in vitro studies and consideration of structure activity relationship provide sufficient information to waive repeated exposure studies. Industry as well as certain regulatory agencies or NGOs support this approach and propose that repeated dose studies may only be required beyond 100 t/a. From a toxicological point of view it has to be stressed that this discussion primarily considers the cost reduction and protection of animals, whereas protection of human health and the environment are secondary. In vitro studies only allow identification of specific hazardous properties which can be detected by the specific test system. Moreover, appropriate information on the dose response of adverse effects, identification of thresholds and NOELs that are essential for risk characterization cannot be obtained from these studies. Consequently, identification of all relevant hazardous properties and endpoints of adverse effects can only be determined in the intact animal by repeated dose studies such as 28-day or 90-day studies. In the absence of such information the hazard identification is incomplete and there is no basis for appropriate risk assessment of human exposure. Thus, any waiving of repeated dose studies in animals bears the probability of unforeseen effects in case of acute or continuous human exposure. From this the undersigning European Toxicologists conclude: 1. The intention of REACH is to identify hazardous properties in order that a reliable risk assessment can be made and measures taken to deal with chemicals posing a significant risk. 2. The recent debate has centered on ways in which the well established in vivo methods for risk assessment can be bypassed. 3. The evidence that the available alternatives would support such replacement is weak. Progress to improve their value for risk assessment purposes is bound to be slow because the issues are very complex. As a group of European Toxicologists we strongly support the need for more research support in these areas, but we believe that over claims for progress is damaging their development. 4. Under the circumstances only two options are available: to reduce very substantially the estimation of hazard and risk with inevitable adverse consequences for human health and environmental protection, or to continue the existing methods until properly validated new methods are available
Scientific Committee on Health and Environmental Risks opinion on: The revised chapter for Human Health Risk Characterisation of the Technical Guidance Document on Risk Assessment in support of Directive 93/67/EEC on new notified substances and Regulation 1488/94 on existing substances of new and existing substances (Draft of November 2005) Members ot the Working Group of SCHER by alph
No full textAdopted by the SCHER during the 13th plenary of 19 September 2006Members ot the Working Group of SCHER by alphabetical order:W. Dekant, C. Fruijtier-Pölloth (External expert;) H. Greim (chair), O. Ladefoged, A. Steenhout, M.Viluksela ;16 p.http://ec.europa.eu/health/scientific_committees/environmental_risks/scher_04-09/index_en.htmhttp://ec.europa.eu/health/scientific_committees/environmental_risks/opinions/scher_opinions_en.htmhttp://ec.europa.eu/health/archive/ph_risk/committees/04_scher/docs/scher_o_040.pdfChemicals under Reg.793/93info:eu-repo/semantics/publishe
A biokinetic model for molybdenum radionuclides : new experimental results
No full textThe ability to describe in a realistic way the biokinetics of radionuclides in the human body is an important requirement in order to get a reliable dose estimation after incorporation of radioactive substances. Recent experimental data have shown the need to introduce relevant modifications to the current model of the biokinetics of molybdenum adopted by ICRP. A new series of investigations, conducted on healthy human volunteers using stable isotopes of Mo as tracers, has been undertaken in order to improve the knowledge of some of the new features outlined in the preliminary investigations. In particular, the results presented here deal with the dependence of the biokinetic parameters on the mass of Mo administered and on its content in the body. The clearance of Mo from blood plasma is not influenced by the administration of different amounts of Mo; the opposite is true for urinary excretion, which is the process adopted by the organism to regulate the body content of Mo rapidly. This fact can be of some importance in deciding a proper intervention after an accidental incorporation of Mo radionuclides
Analytische Methoden zur Prüfung gesundheitsschädlicher Arbeitsstoffe: Analysen in biologischem Material.
No full textInternal biokinetic behaviour of molybdenum in humans studied with stable isotopes as tracers
No full textAlthough molybdenum is considered to be an essential trace metal for humans, the knowledge about its metabolism is rather limited. The present study was aimed at the assessment of biokinetics following intravenous injection of trace amounts of 95Mo or 96Mo into five healthy volunteers. In a total of 11 investigations, the plasma clearance up to eight hours and the urinary excretion for at least three days after the injection were evaluated. The tracer concentrations were determined by proton nuclear activation analysis in blood plasma and by thermal ionization mass spectrometry in urine samples respectively. In all subjects, the plasma clearance is much faster than expected from the literature. The data obtained for the plasma clearance of the tracer can reasonably be fitted by a two exponential equation. The half times of the fast component range between 4 and 70 minutes and for the slow component between 3 and 30 hours. The urinary excretion of the injected tracer seems also to be faster than expected and the fractions lost are higher for larger doses administered. For the smallest dose given, 34% of the injected tracer were excreted within one day whereas for the four times larger dose about 60% were lost. These findings on urinary excretion are in agreement with recently published results
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