Documents tissue penetration 6 results

"Human exposure to solar ultraviolet radiation has important public health implications. Evidence of harm associated with overexposure to UV has been demonstrated in many studies. Skin cancer and malignant melanoma are among the most severe health effects, but a series of other health effects have been identified. The current report provides a quantification of the global disease burden associated with UV. The information presented forms a knowledge base for the prevention of adverse effects of UV exposure that is achievable with known and accessible interventions. UV prevention focuses on protecting the skin and other organs from UV radiation. On the other hand, a moderate degree of UV exposure is necessary for the production of Vitamin D which is essential for bone health. Additionally, evidence emerges that low Vitamin D levels are likely to be associated with other chronic diseases. Thus, public health policy on ultraviolet radiation needs to aim at preventing the disease burden associated both with excessive and with insufficient UV exposure."

"Asbestos inhaled into the lung is recognized as a potential causal agent for the development of diseases in man. The diseases induced by asbestos include lung cancer, fibrosis of the lung (asbestosis), and extrapulmonary tumors including mesothelioma (a tumor of the serosal membrane), as well as fibrosis and other changes in the pleura linings. The cause of these diseases can often be more specifically linked to asbestos exposure once tissue burden of asbestos is established. The asbestos burden in tissue can be defined as the number of asbestos bodies and/or the numbers and types of asbestos fibers found in the tissue. In either of these cases the quality of information is directly dependent on the preparative techniques and instrumentation used in the analysis. The present article will discuss the significance of findings of tissue burden based on both these variables."

"Background: The potential for asbestos exposure among members of the general population is appreciable, considering its widespread use in many products. This study examined tissue burden of asbestos in such a population. Methods: A group of 33 individuals who had no work history of occupational exposure to asbestos were included in the study. Tissue sections from areas adjacent to those sites sampled for digestion were found to be without ferruginous bodies (FB) or histopathology consistent with asbestos-induced changes. All individuals had 20 or less FBs per gram of digested wet lung, a number considered to reflect general population levels. Tissue analysis of uncoated fiber burden was carried out by analytical electron microscopy. There was a trend of a higher likelihood of FB and asbestos fiber content correlated with age. Results:The data are not consistent with the findings that chrysotile is readily found in lung tissue from the general population, in that none was found in 19 of the cases. It was almost as likely that one would find anthophyllite (12 of 33 cases) in this study. The commercial amphiboles (amosite and crocidolite) were occasionally found in the tissue from the general population and, when observed, were few in numbers. Twenty-six of the patients had no FBs and ten had no uncoated asbestos fibers within the limits of detectability in this study. Conclusions: The total tissue burden of asbestos in this study is much less than earlier reported observations from other general populations."

"Gold nanoparticles have been reported to cross the placenta after maternal intravenous injection in rats, but structural and physiologic differences across species preclude inferences about the ability of nanoparticles to cross human placentas based on animal studies. Wick et al. (p. 432) used an ex vivo human placental perfusion model to study the transfer of fluorescent polystyrene particles (nominal diameters of 50, 80, 240, and 500 nm) across the placenta. The authors report that polystyrene particles up to 240 nm in diameter were able to cross the placental barrier without affecting the viability of the placental explant. The authors conclude that findings are consistent with size-dependent transfer of nanomaterials across human placentas, but they acknowledge that the model involved high-dose exposures over a period of a few hours and that the perfusion rate was representative of placental perfusion late in pregnancy. In addition, they suggest that transfer may also be influenced by particle composition or surface coatings, thus preventing generalization across different types of nanoparticles."

"Evaluates carcinogenic risks associated with human exposure to solar radiation and to ultraviolet radiation from medical and cosmetic devices, general illumination, and industrial sources. The main objective of the evaluation was to determine whether enough evidence is available to decide which segments of the radiation spectrum are responsible for its adverse effects. To this end, particular attention is given to data that shed light on the distinctive carcinogenic activity of ultraviolet A, B, and C radiation. In evaluating carcinogenic potential, the report also considers the importance of human constitutional risk factors, such as skin type, hair and eye colour, and specific subtypes of exposure, such as occupational and recreational exposures. More than 1,000 studies were critically assessed. On the basis of a large body of evidence from human and experimental studies, the monograph concludes that solar radiation is carcino-genic to humans, causing cutaneous malignant melanoma and nonmelanocytic skin cancer. Evidence for the carcinogenicity of ultraviolet A, B, and C radiation was judged sufficient in experimental animals. All three segments of the radiation spectrum were classified as probably carcinogenic to humans. Use of sunlamps and sunbeds entails exposures that are probably carcinogenic to humans. The carcinogenicity of exposure to fluorescent lighting could not be determined. Studies of topical sunscreens are reviewed in an appendix, which concludes that, although effective in preventing sunburn, little is known about their protective value against harmful immuno-logical changes, photo-ageing, or skin cancer. "... conforms to the usual high standards of IARC monographs ... a valuable source of information about the neglected areas of radiation pathology and toxicology..." - Journal of Clinical Pathology"