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Abstract
The lung is constantly exposed to a large volume of inhaled air that may contain toxicant xenobiotics. With the possibility of exposure to a variety of respiratory toxicants from airborne pollutants in our environment during the course of daily activities, in occupational settings, the use of aerosol sprays for household products, and the development of inhalant bronchial therapies, pulmonary toxicology has become an important subspecialty of toxicology. The lung is susceptible to injury following hematogenous exposure to toxicants. Susceptibility to injury and the type of response following exposure to air- or blood-borne toxicants is largely dependent on the physiochemical characteristics and concentration of the toxicant, duration of exposure, site/tissue specific sensitivity, and the integrity of the defense mechanisms of the lung. In this chapter, nonneoplastic and neoplastic spontaneous lesions and those that develop in the lungs of rats following exposure to toxicants by various routes, but primarily by inhalation, are discussed in detail which provides insight into our understanding of how human lungs respond to toxic chemicals. In addition, the gross and microscopic anatomy of the rat lung is also discussed some detail. Although inhalation is the primary route of exposure in experimental studies, in the past, many studies used intratracheal instillation or direct injection of known carcinogens into the lung. These experiments often resulted in the development of squamous cell carcinomas even though they are very rare as a naturally occurring neoplasm. Instillation of chemicals or particles into the trachea or pleura or direct injection into the lung results in lesions or responses that may not be as relevant to understanding the mechanism of pulmonary carcinogenesis as inhalation of materials under more normal conditions. There remain, however, many areas where our understanding of the response of the lung to toxic chemicals is incomplete.
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Shi H, Magaye R, Castranova V, Zhao J. Titanium dioxide nanoparticles: a review of current toxicological data. Part Fibre Toxicol 2013. [PMID: 23587290 DOI: 10.1186/17438977-10-15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023] Open
Abstract
Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.
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Affiliation(s)
- Hongbo Shi
- Public Health Department of Medical School, Zhejiang Provincial Key Laboratory of Pathological and Physiological Technology, Ningbo University, Ningbo, Zhejiang Province, 315211, PR China
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Shi H, Magaye R, Castranova V, Zhao J. Titanium dioxide nanoparticles: a review of current toxicological data. Part Fibre Toxicol 2013; 10:15. [PMID: 23587290 PMCID: PMC3637140 DOI: 10.1186/1743-8977-10-15] [Citation(s) in RCA: 789] [Impact Index Per Article: 71.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 04/02/2013] [Indexed: 01/19/2023] Open
Abstract
Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications. TiO2 NPs possess different physicochemical properties compared to their fine particle (FP) analogs, which might alter their bioactivity. Most of the literature cited here has focused on the respiratory system, showing the importance of inhalation as the primary route for TiO2 NP exposure in the workplace. TiO2 NPs may translocate to systemic organs from the lung and gastrointestinal tract (GIT) although the rate of translocation appears low. There have also been studies focusing on other potential routes of human exposure. Oral exposure mainly occurs through food products containing TiO2 NP-additives. Most dermal exposure studies, whether in vivo or in vitro, report that TiO2 NPs do not penetrate the stratum corneum (SC). In the field of nanomedicine, intravenous injection can deliver TiO2 nanoparticulate carriers directly into the human body. Upon intravenous exposure, TiO2 NPs can induce pathological lesions of the liver, spleen, kidneys, and brain. We have also shown here that most of these effects may be due to the use of very high doses of TiO2 NPs. There is also an enormous lack of epidemiological data regarding TiO2 NPs in spite of its increased production and use. However, long-term inhalation studies in rats have reported lung tumors. This review summarizes the current knowledge on the toxicology of TiO2 NPs and points out areas where further information is needed.
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Affiliation(s)
- Hongbo Shi
- Public Health Department of Medical School, Zhejiang Provincial Key Laboratory of Pathological and Physiological Technology, Ningbo University, Ningbo, Zhejiang Province, 315211, P. R. China
| | - Ruth Magaye
- Public Health Department of Medical School, Zhejiang Provincial Key Laboratory of Pathological and Physiological Technology, Ningbo University, Ningbo, Zhejiang Province, 315211, P. R. China
| | - Vincent Castranova
- Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV, 26505, USA
| | - Jinshun Zhao
- Public Health Department of Medical School, Zhejiang Provincial Key Laboratory of Pathological and Physiological Technology, Ningbo University, Ningbo, Zhejiang Province, 315211, P. R. China
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Zhao J, Castranova V. Toxicology of nanomaterials used in nanomedicine. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2011; 14:593-632. [PMID: 22008094 DOI: 10.1080/10937404.2011.615113] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
With the development of nanotechnology, nanomaterials are being widely used in many industries as well as in medicine and pharmacology. Despite the many proposed advantages of nanomaterials, increasing concerns have been expressed on their potential adverse human health effects. In recent years, application of nanotechnology in medicine has been defined as nanomedicine. Techniques in nanomedicine make it possible to deliver therapeutic agents into targeted specific cells, cellular compartments, tissues, and organs by using nanoparticulate carriers. Because nanoparticles possess different physicochemical properties than their fine-sized analogues due to their extremely small size and large surface area, they need to be evaluated separately for toxicity and adverse health effects. In addition, in the field of nanomedicine, intravenous and subcutaneous injections of nanoparticulate carriers deliver exogenous nanoparticles directly into the human body without passing through the normal absorption process. These nanoparticulate carriers themselves may be responsible for toxicity and interaction with biological macromolecules within the human body. Second, insoluble nanoparticulate carriers may accumulate in human tissues or organs. Therefore, it is necessary to address the potential health and safety implications of nanomaterials used in nanomedicine. Toxicological studies for biosafety evaluation of these nanomaterials will be important for the continuous development of nanomedical science. This review summarizes the current knowledge on toxicology of nanomaterials, particularly on those used in nanomedicine.
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Affiliation(s)
- Jinshun Zhao
- Public Health Department of Medical School, Ningbo University, Ningbo, Zhejiang, P. R. China
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Gu Q, Hu C, Chen Q, Xia Y, Feng J, Yang H. Development of a rat model by 3,4-benzopyrene intra-pulmonary injection and evaluation of the effect of green tea drinking on p53 and bcl-2 expression in lung carcinoma. ACTA ACUST UNITED AC 2009; 32:444-51. [DOI: 10.1016/j.canep.2009.04.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Dixon D, Herbert RA, Kissling GE, Brix AE, Miller RA, Maronpot RR. Summary of chemically induced pulmonary lesions in the National Toxicology Program (NTP) toxicology and carcinogenesis studies. Toxicol Pathol 2008; 36:428-39. [PMID: 18441259 DOI: 10.1177/0192623308315360] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The lung is the second most common target site of neoplasia of chemicals tested by the National Toxicology Program (NTP). Of all peer-reviewed NTP studies to date (N = 545), a total of sixty-four chemicals in sixty-six reports produced significant site-specific neoplasia in the lungs of rats and/or mice. Of the studies associated with lung tumor induction, approximately 35% were inhalation and 35% were gavage studies, with dosed-feed, dosed-water, topical, intraperitoneal, or in utero routes of chemical administration accounting for 18%, 6%, 3%, 1%, and 1% of the studies, respectively. The most commonly induced lung tumors were alveolar/bronchiolar (A/B) adenoma and/or carcinoma for both species. The most frequently observed nonneoplastic lesions included hyperplasia and inflammation in both species. The liver was the most common primary site of origin of metastatic lesions to the lungs of mice; however, skin was most often the primary site of origin of metastatic lesions to the lungs of rats. In summary, A/B adenoma and carcinoma were the most frequently diagnosed chemically induced tumors in the lungs of both rats and mice in the NTP toxicology and carcinogenesis bioassays, and hyperplasia and inflammation were the most common nonneoplastic changes observed.
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Affiliation(s)
- Darlene Dixon
- Cellular and Molecular Pathology Branch, National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
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Blake DM, Maness PC, Huang Z, Wolfrum EJ, Huang J, Jacoby WA. Application of the Photocatalytic Chemistry of Titanium Dioxide to Disinfection and the Killing of Cancer Cells. ACTA ACUST UNITED AC 2008. [DOI: 10.1080/03602549909351643] [Citation(s) in RCA: 336] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Walker NJ, Yoshizawa K, Miller RA, Brix AE, Sells DM, Jokinen MP, Wyde ME, Easterling M, Nyska A. Pulmonary lesions in female Harlan Sprague-Dawley rats following two-year oral treatment with dioxin-like compounds. Toxicol Pathol 2007; 35:880-9. [PMID: 18098034 PMCID: PMC2633090 DOI: 10.1080/01926230701748396] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Dioxin and dioxin-related compounds have been associated with high incidences of pulmonary dysfunctions and/or cancers in humans. To evaluate the relative potencies of effects of these compounds, the National Toxicology Program completed a series of two-year bioassays which were conducted using female Harlan Sprague-Dawley rats. The rats were treated orally for up to 2 years with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 3,3',4,4',5-pentachlorobiphenyl (PCB126), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and a ternary mixture of TCDD, PCB126 and PeCDF. In addition to treatment-related effects reported in other organs, a variety of pulmonary lesions were observed that were related to exposure. Pulmonary CYP1A1-associated 7-ethoxyresorufin-O-deethylase (EROD) activity was increased in all dosed groups. The most common non-neoplastic lesions, which occurred in all studies, were bronchiolar metaplasia and squamous metaplasia of the alveolar epithelium. Cystic keratinizing epithelioma was the most commonly observed neoplasm which occurred in all studies. A low incidence of squamous cell carcinoma was associated only with PCB126 treatment. Potential mechanisms leading to altered differentiation and/or proliferation of bronchiolar and alveolar epithelia may be through CYP1A1 induction or disruption of retinoid metabolism.
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Affiliation(s)
- Nigel J Walker
- National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
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Oka Y, Mitsui M, Kitahashi T, Sakamoto A, Kusuoka O, Tsunoda T, Mori T, Tsutsumi M. A Reliable Method for Intratracheal Instillation of Materials to the Entire Lung in Rats. J Toxicol Pathol 2006. [DOI: 10.1293/tox.19.107] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Yasuo Oka
- Department of Surgery, Division of Gastroenterology, Kawasaki Medical University
| | | | | | | | - Osamu Kusuoka
- Department of Molecular Pathology, Nara Medical University
| | - Tsukasa Tsunoda
- Department of Surgery, Division of Gastroenterology, Kawasaki Medical University
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Rausch LJ, Bisinger EC, Sharma A. Carbon black should not be classified as a human carcinogen based on rodent bioassay data. Regul Toxicol Pharmacol 2004; 40:28-41. [PMID: 15265604 DOI: 10.1016/j.yrtph.2004.04.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Indexed: 10/26/2022]
Abstract
Numerous epidemiology studies have failed to adequately demonstrate an increased risk of lung cancer due to occupational exposure to carbon black (CB). CB is not carcinogenic to mice (oral, skin or inhalation), hamsters (inhalation or intratracheal), guinea pigs (inhalation), rabbits (skin or inhalation), primates (skin or inhalation) or rats (oral). Only studies conducted by inhalation and intratracheal administration in rats have shown significant increases in benign and malignant lung tumors and lesions described as benign cystic keratinizing squamous-cell (KSC) tumors. CB-induced lung tumor formation, including KSC lesions, occurs only in rats. An expert panel reviewing KSC lesions (induced in rats by TiO2 or p-aramid) concluded that KSC lesions are not seen in humans. Lung tumors in humans are primarily located in the bronchial airways, whereas in the rat they occur in the parenchyma and are alveolar in origin. This species-specific response (tumor formation and KSC lesions) by the rat to CB, not seen in any other laboratory species and which has not been reported in humans, strongly suggests that the results of the rat inhalation bioassay should not be considered directly relevant when assessing human risk. Therefore, CB should not be classified as carcinogenic to humans based on the rodent bioassay data.
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Affiliation(s)
- L J Rausch
- Akzo Nobel Chemicals Inc., 525 W. Van Buren Street, Chicago, IL, USA
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Valberg PA, Crouch EA. Meta-analysis of rat lung tumors from lifetime inhalation of diesel exhaust. ENVIRONMENTAL HEALTH PERSPECTIVES 1999; 107:693-9. [PMID: 10464067 PMCID: PMC1566471 DOI: 10.1289/ehp.99107693] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Estimating the carcinogenic potential of exposure to diesel-engine exhaust particulates (DEPs) is problematic. In rats, high concentrations of DEPs (> 1,000 microg/m(3)) inhaled over a lifetime result in excess lung tumors. However, data for rats exposed to DEP at concentrations not associated with lung overload are consistent with no tumorigenic effect. Individual rat studies have only a limited number of exposure groups; therefore, we combined the tumor data from eight chronic inhalation studies in a meta-analysis. Statistical analysis identified a threshold of response between 200 and 600 microg/m(3) average continuous lifetime exposure, consistent with biological-effect thresholds reported by other investigators. Our exposure-response analysis of all rats with < 600 microg/m(3) average continuous lifetime exposure found no tumorigenic effect of DEP in these rats. When we evaluated all rat studies, accounted for a threshold and for inhomogeneity between experiments, and expressed the results in terms of human unit risk (UR), we found a negative maximum-likelihood human UR of -32 (times) 10(-6) per microgram per cubic meter (microg/m(3)), but this was not statistically significantly different from zero. Extrapolating the rat upper 95th percentile confidence limit to humans gave an upper-bound human UR of 9.3 (times) 10(-6) per microg/m(3)]. This upper-bound human UR, derived from all of the data points (including 1,087 animals below the estimated threshold and 1,433 in the control groups), falls entirely below the range of estimates derived from lung-overloaded rats or from epidemiology of railroad workers. Our meta-analysis of the low-exposure data in rats does not support a lung cancer risk for DEP exposure at nonoverload conditions. Average ambient concentrations of DEP (0-3 microg/m(3)) are < 1% of the concentration associated here with a threshold of tumor response in the rat bioassay.
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Affiliation(s)
- P A Valberg
- Cambridge Environmental Inc., Cambridge, Massachusetts 02141, USA.
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Valberg PA, Crouch EA. Meta-analysis of rat lung tumors from lifetime inhalation of diesel exhaust. ENVIRONMENTAL HEALTH PERSPECTIVES 1999; 107:693-699. [PMID: 10464067 DOI: 10.2307/3434652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Estimating the carcinogenic potential of exposure to diesel-engine exhaust particulates (DEPs) is problematic. In rats, high concentrations of DEPs (> 1,000 microg/m(3)) inhaled over a lifetime result in excess lung tumors. However, data for rats exposed to DEP at concentrations not associated with lung overload are consistent with no tumorigenic effect. Individual rat studies have only a limited number of exposure groups; therefore, we combined the tumor data from eight chronic inhalation studies in a meta-analysis. Statistical analysis identified a threshold of response between 200 and 600 microg/m(3) average continuous lifetime exposure, consistent with biological-effect thresholds reported by other investigators. Our exposure-response analysis of all rats with < 600 microg/m(3) average continuous lifetime exposure found no tumorigenic effect of DEP in these rats. When we evaluated all rat studies, accounted for a threshold and for inhomogeneity between experiments, and expressed the results in terms of human unit risk (UR), we found a negative maximum-likelihood human UR of -32 (times) 10(-6) per microgram per cubic meter (microg/m(3)), but this was not statistically significantly different from zero. Extrapolating the rat upper 95th percentile confidence limit to humans gave an upper-bound human UR of 9.3 (times) 10(-6) per microg/m(3)]. This upper-bound human UR, derived from all of the data points (including 1,087 animals below the estimated threshold and 1,433 in the control groups), falls entirely below the range of estimates derived from lung-overloaded rats or from epidemiology of railroad workers. Our meta-analysis of the low-exposure data in rats does not support a lung cancer risk for DEP exposure at nonoverload conditions. Average ambient concentrations of DEP (0-3 microg/m(3)) are < 1% of the concentration associated here with a threshold of tumor response in the rat bioassay.
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Affiliation(s)
- P A Valberg
- Cambridge Environmental Inc., Cambridge, Massachusetts 02141, USA.
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