Silica is the second most common element after oxygen, and therefore, exposures to crystalline silica dust occur in a large variety of occupations such as metal foundries, constructions, and ceramic, quarry, and pottery industries. Since crystalline silica exposure has been linked with silicosis, lung cancer, and other pulmonary diseases, adverse effect attributed to this element has be a cause for concern worldwide. Silica dust exposure in workers is still considered to be important health problem especially in developing countries. The aim of the study was to investigate the effects of occupational silica exposure on oxidative stress parameters including the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), and levels of total glutathione (GSH) and thiobarbituric acid reactive substance (TBARS) as well as immune system parameters such as interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, and IL-10 and tumor necrosis factor (TNF)-α in Turkish ceramic workers. In this study, nearly 50% of Turkish ceramic workers were diagnosed with silicosis. Eighty-four percent of these silicotic workers were found to present with profusion category 1 silicosis, whereas controls (n = 81) all displayed normal chest radiographs. Data demonstrated a significant decrease in levels of GSH and activities of CAT, SOD, and GPx, but a significant increase in MDA levels and activity of GR in all workers. Further, workers possessed significantly higher levels of IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, and TNF-α. These observations suggest that ceramic workers may have impaired antioxidant/oxidant status and activated immune system indicative of inflammatory responses.

ÖzAnahtar Kelimeler GirişEğitimden ve okullardan beklentilerin her geçen gün artması eğitimcileri bu taleplere karşılık verebilmek gibi zorlu bir görevle karşı karşıya bırakmaktadır. Eğitim sistemleri ve okullar hem artan taleplere karşılık vermek hem de misyonlarını daha başarılı bir şekilde gerçekleştirebilmek için çeşitli reform çabaları içine girmişlerdir. Reform çabalarının yöneldiği önemli odak noktalarından birinin öğretmenler olduğu söylenebilir.

PurposeFailure to identify any significant relationships between principal leadership and student achievement has proved concerns about the assumed value and legitimacy of principal leadership. The purpose of this paper is to contribute to the current literature by empirically testing the relationships between the principal leadership and the teacher self‐efficacy, a construct which has a proven impact on student achievement. The role of collective efficacy on the relationship between transformational leadership of principals and self‐efficacy of teachers was a special focus for the study.Design/methodology/approachA causal comparative research design was employed to study the direct, indirect, and mediating relationships among principal leadership, teacher self‐efficacy, and collective efficacy in schools. The participants included a cluster‐random sample of 813 primary school teachers. Data gathering instruments composed of a combination of the Multifactor Leadership Questionnaire, the Collective Teacher Efficacy Scale and the Teacher's Sense of Efficacy Scale. A structural equation modelling with path analysis was employed to test the research models and hypotheses.FindingsFindings of the study demonstrated that collective efficacy and transformation leadership jointly shape teachers' self‐efficacy. There was a significant relationship between principals' transformational leadership and teachers' self‐efficacy beliefs. This relationship was mediated and magnified by collective efficacy in schools.Research limitations/implicationsThe study has the common limitations of the self‐reported perceptions of participants.Originality/valueThe study enlightened the little‐known causal relationship mechanisms through which transformational leadership practices of principals and collective efficacy of schools affect the self‐efficacy beliefs of teachers. The findings are in line with the socio‐cognitive theory which assumes the presence of reciprocal relationships among leadership, organization, and person domains in shaping organizational behaviors of teachers. The study also parallels with the emerging literature about the mediating effects of collective efficacy on the relationship between principal transformational leadership and teacher self‐efficacy.

It is known that ceramic workers are potentially exposed to complex mixture of chemicals such as silica, inorganic lead, lime, beryllium and aluminum that can be associated with an increased risk of several diseases. All operations in the ceramic industries such as mixing, moulding, casting, shaking out and finishing jobs, have been associated with the higher exposure levels and in most of the silica-related industries, average overall exposure exceeded permissible exposure levels for respirable crystalline silica. The aim of this study was to evaluate the possible genotoxic damage in ceramic workers exposed to complex mixture of chemicals mainly crystalline silica. For this purpose, the blood and buccal epithelial cell samples were taken from the ceramic workers (n = 99) and their controls (n = 81). The genotoxicity was assessed by the alkaline comet assay in isolated lymphocytes and whole blood. Micronucleus (MN), binucleated (BN), pyknotic (PYC), condensed chromatin (CC), karyolytic (KYL), karyorrhectic (KHC) and nuclear bud (NBUD) frequencies in buccal epithelial cells and plasma 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) levels were also evaluated. In the study, 38 workers were diagnosed with silicosis, 9 workers were suspected to have silicosis, whereas 52 workers were found to be healthy. DNA damage in blood and lymphocytes; MN, CC + KHC, PYC frequencies in buccal epithelial cells and 8-oxodG levels in plasma were increased in workers compared to their controls. These results showed that occupational chemical mixture exposure in ceramic industry may cause genotoxic damage that can lead to important health problems in the workers.