Browsing by Author "Porto, B."
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- Cytogenetic and immunological effects of formaldehyde in a group of exposed workersPublication . Costa, S.; García-Lestón, J.; Coelho, M.; Coelho, P.; Costa, C.; Silva, S.; Porto, B.; Laffon, B.; Teixeira, João PauloFormaldehyde (FA) is a widely used industrial chemical for which exposure is associated with nasopharyngeal and sinonasal cancer. Based on sufficient evidence of carcinogenicity from human investigations, supporting studies on mechanisms underlying carcinogenesis, and experimental evidence in animals, FA status was recently revised and reclassified as a human carcinogen. The highest level of exposure to FA occurs in occupational settings. Although several studies reported FA ability to induce genotoxic responses in exposed workers, not all findings were conclusive. In addition, published studies on the immunological effects of FA indicate that this compound may be able to modulate immune responses, although data in exposed subjects are still preliminary. In this study a group of pathology anatomy workers exposed to FA was evaluated for cytogenetic and immunological parameters. A control group with similar sociodemographic characteristics and without known occupational exposure to FA was also included. Genotoxicity was evaluated by means of micronucleus (MN) test, sister chromatid exchanges (SCE), and T-cell receptor (TCR) mutation assay. Percentages of different lymphocyte subpopulations were selected as immunotoxic biomarkers. The mean level of FA environmental exposure was 0.36 ± 0.03 ppm. MN and SCE frequencies were significantly increased in the exposed group. A significant decrease of the percentage of B cells in the exposed group was also found. Data obtained in this study indicate that genotoxic and immunotoxic increased risk due to FA occupational exposure cannot be excluded. Implementation of effective control measures along with hazard prevention campaigns may be crucial to decrease the risk.
- Micronucleus frequencies in lymphocytes and buccal cells in formaldehyde exposed workersPublication . Costa, S.; Brandão, F.; Coelho, M.; Costa, C.; Coelho, P.; Silva, S.; Porto, B.; Teixeira, João PauloFormaldehyde (FA) is a high-volume production chemical produced worldwide with a large range of industrial and medical uses. Listed, since 2004, by IARC as a human carcinogen, FA status was recently revised by the US government who reclassified this compound as known to be a human carcinogen. Both reclassifications are based on sufficient evidence of carcinogenicity from epidemiologic studies, supporting data on mechanisms of carcinogenesis and experimental evidence in animals. The highest level of human exposure to FA occurs in occupational settings. Consistent findings of increased risks of certain types of rare cancers were found among workers with higher measures of exposure to FA (exposure level or duration). The aim of the present study was to assess the genotoxic effects of occupational exposure to FA. A group of pathology and anatomy workers was evaluated for micronuclei in lymphocytes and in exfoliated buccal cells. Genotoxic endpoints are of great interest in the risk assessment of occupational carcinogens because they precede by a long time the potential health effects, thus offering a greater potential for preventive measures. Micronuclei in lymphocytes and in exfoliated buccal cells were significantly higher in the exposed subjects when compared with controls. Air sampling was performed in the workers’ breathing zone for representative working periods and an 8h-time weighted average was assessed.
- Multiple genotoxic activities of ptaquiloside in human lymphocytes: aneugenesis, clastogenesis and induction of sister chromatid exchangePublication . Gil da Costa, R.M.; Coelho, P.; Sousa, R.; Bastos, M.M.S.M.; Porto, B.; Teixeira, João Paulo; Malheiro, I; Lopes, C.Ptaquiloside, a norsesquiterpene glycoside from bracken (Pteridium aquilinum), is a known carcinogen towards animals. Its genotoxicity is mainly attributed to its DNA-alkylating and clastogenic properties. This study analyses various modes of genotoxic action of ptaquiloside in human mononuclear blood cells. The alkaline comet assay was performed on cells exposed to 5μg/ml ptaquiloside for 5, 10, 20, 30, 40 or 50min. Tail length was used as a DNA-damage parameter. Assays to determine structural and numerical chromosomal aberrations and sister-chromatid exchange were conducted on cells exposed to 5, 10 or 20μg/ml ptaquiloside for 48h. The tail length showed maximum DNA damage at 20-30min, diminishing onwards. Highly significant (p<0.001) dose-dependent increases in structural and numerical chromosomal aberrations and SCE were observed in response to ptaquiloside. These results indicate that ptaquiloside is not only a DNA-alkylating agent, but expresses its genotoxicity through multiple mechanisms including clastogenesis, aneugenesis and the mechanism underlying SCE induction, which is not entirely understood. Recent studies support the role played by aneuploidy in oncogenesis, highlighting the importance of this endpoint for mutagenicity screening. SCE are thought to represent the long-term effects of mutagens and are an important genotoxicity biomarker. The present results also agree with data from epidemiological studies and from animal in vivo studies, further supporting the hypothesis that ptaquiloside may represent a significant threat to human health.
- Occupational Exposure to Formaldehyde: Genotoxic Risk Evaluation By Comet Assay And Micronucleus Test Using Human Peripheral LymphocytesPublication . Costa, S.; Pina, C.; Coelho, P.; Costa, C.; Silva, S.; Porto, B.; Laffon, B.; Teixeira, João PauloFormaldehyde (FA) is a world high-production compound with numerous applications ranging from production of resins to medicines. Due to its sensitizing properties, irritating effects and potential cancer hazard FA is of great environmental health concern. Numerous studies in humans and experimental animals demonstrated that inhaled FA produced toxicity, genotoxicity, and cancer at distal sites. IARC, based on sufficient data, reclassified FA as a human carcinogen. The highest level of human exposure to this aldehyde occurs in occupational settings, namely, in pathology and anatomy laboratories, where FA is commonly used as a fixative and tissue preservative. Several studies consistently showed that the levels of airborne FA in anatomy laboratories exceeded recommended exposure criteria. In order to assess the genotoxic effects of chronic occupational exposure to FA, a group of pathology/anatomy workers was assessed using a micronucleus (MN) test and comet assay. The level of exposure to FA was also determined and the time-weighted average (TWA) of exposure was calculated for each subject. The TWA mean value for FA exposed workers was 0.43 ± 0.06 ppm, exceeding national and international recommended limit levels of 0.3 ppm. Both MN frequency and comet assay parameters were significantly higher in exposed subjects. Data obtained confirm a correlation between genetic damage and occupational exposure to FA. These data, along with recent implications of human carcinogenicity, point out the need for close monitoring of occupational exposure to FA. Implementation of security and hygiene measures as well as good practices campaigns may be crucial to decrease risk.