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Subchronic toxicity là khả năng gây hại của một chất hoá học được tiếp xúc kéo dài trong một khoảng thời gian ngắn, thường là từ một tháng đến một năm, và áp dụ...
Subchronic toxicity là khả năng gây hại của một chất hoá học được tiếp xúc kéo dài trong một khoảng thời gian ngắn, thường là từ một tháng đến một năm, và áp dụng cho các thí nghiệm trên động vật. Nghiên cứu về subchronic toxicity nhằm đánh giá tác động của chất đó lên cơ thể và các cơ quan nội tạng của động vật trong thời gian kéo dài.
Subchronic toxicity studies are conducted to evaluate the adverse effects of a substance when administered to animals over a period of several weeks to a few months. These studies are conducted to assess potential health hazards and determine the appropriate exposure limits for humans.
During subchronic toxicity studies, animals, typically rodents, are exposed to the substance of interest on a daily basis for a specified duration. The duration of the study can vary depending on the substance being tested and regulatory requirements. The animals are closely monitored for any signs of toxicity and changes in various parameters such as body weight, food and water consumption, clinical signs, organ weights, hematological and biochemical parameters, and histopathological examinations.
The primary objective of subchronic toxicity studies is to provide information on the effects of repeated exposures to the substance and identify target organs or systems that may be susceptible to toxicity. This data helps in determining safe levels of exposure for humans and establishing guidelines for occupational and environmental exposures.
The findings from subchronic toxicity studies can provide valuable insights into potential adverse health effects that may occur with prolonged or repeated exposures to a substance. This information is crucial for assessing the risk associated with the substance and aids in the development of safety guidelines, regulatory standards, and risk management strategies.
It is important to note that subchronic toxicity studies are just one component of the comprehensive toxicological evaluation of a substance. Other types of studies, such as acute toxicity, chronic toxicity, and carcinogenicity studies, may also be conducted to provide a complete profile of the toxicological effects of a substance.
Subchronic inhalation toxicity of iron oxide (magnetite, Fe<sub>3</sub>O<sub>4</sub>) in rats: pulmonary toxicity is determined by the particle kinetics typical of poorly soluble particles Journal of Applied Toxicology - Tập 32 Số 7 - Trang 488-504 - 2012
ABSTRACTWistar rats were nose‐only exposed to pigment‐sized iron oxide dust (Fe3O4, magnetite) in a subchronic 13‐week inhalation study according to the OECD testing guidelines TG#413 and GD#39. A 4 week pilot study with a 6 month post exposure period served as basis for validating the kinetic modeling approaches utilized to design the subchronic study. Kinetic analyses made during this post exposure period demonstrated that a diminution in particle clearance and lung inflammation occurred at cumulative exposure levels exceeding the lung overload threshold. Animals were exposed 6 h per day, five days per week for 13 consecutive weeks at actual concentrations of 0, 4.7, 16.6 and 52.1 mg m−3 (mass median aerodynamic diameter ≈1.3 μm, geometric standard deviation = 2). The exposure to iron oxide dust was tolerated without mortality, consistent changes in body weights, food and water consumption or systemic toxicity. While general clinical pathology and urinalysis were unobtrusive, hematology revealed changes of unclear toxicological significance (minimally increased differential neutrophil counts in peripheral blood). Elevations of neutrophils in bronchoalveolar lavage (BAL) appeared to be the most sensitive endpoint of study. Histopathology demonstrated responses to particle deposition in the upper respiratory tract (goblet cell hyper‐ and/or metaplasia, intraepithelial eosinophilic globules in the nasal passages) and the lower respiratory tract (inflammatory changes in the bronchiolo‐alveolar region). Consistent changes suggestive of pulmonary inflammation were evidenced by BAL, histopathology, increased lung and lung‐associated‐lymph node (LALN) weights at 16.6 and 52.1 mg m−3. Increased septal collagenous fibers were observed at 52.1 mg m−3. Particle translocation into LALN occurred at exposure levels causing pulmonary inflammation. In summary, the retention kinetics iron oxide reflected that of poorly soluble particles. The empirical no‐observed‐adverse‐effect level (NOAEL) and the lower bound 95% confidence limit on the benchmark concentration (BMCL) obtained by benchmark analysis was 4.7 and 4.4 mg m−3, respectively, and supports an OEL (time‐adjusted chronic occupational exposure level) of 2 mg m−3 (alveolar fraction). Copyright © 2011 John Wiley & Sons, Ltd.
Subchronic organismal toxicity, cytotoxicity, genotoxicity, and feeding response of pacific oyster (<i>Crassostrea gigas</i>) to lindane (γ‐HCH) exposure under experimental conditions Environmental Toxicology and Chemistry - Tập 26 Số 10 - Trang 2192-2197 - 2007
AbstractThis study evaluated organismal toxicity, cytotoxicity, and genotoxicity and the filtration rate in response to different concentrations of subchronic lindane (gamma‐hexachlorocyclohexane [γ‐HCH]), exposure (12 d) in adult Pacific oysters Crassostrea gigas. Oysters were exposed in vivo in laboratory aquaria to 10 different concentrations (0.0–10.0 mg/L) of γ‐HCH. The median lethal concentration (LC50) after 12 d was calculated as 2.22 mg/L. Cytotoxic effects were observed in hemocytes, where the mean cell viability was significantly decreased at 1.0 mg/L of γ‐HCH after 12 d. Genotoxicity of γ‐HCH measured by single cell gel electrophoresis assay, in hemocytes was evident at 0.7 mg/L of γ‐HCH after 12 d. After 4 h of exposure to γ‐HCH, filtration rates were reduced compared with controls to 65.8 and 38.2% at concentrations of 0.3 and 0.7 mg/L, respectively, and after 11 d of exposure, filtration rates were reduced to 60.4 and 30.9% at concentrations of 0.1 mg/L and higher. These results show the subchronic effects of γ‐HCH at different concentrations and effect sensitivities are categorized as filtration rate < genotoxicity < cytotoxicity < mortality. The relevance of integral toxicity evaluation, considering different endpoints from molecular, cellular, and individual levels is discussed.
