Biosynthesis of Silver Nanoparticles Using Azadirachta indica and Their Antioxidant and Anticancer Effects in Cell Lines

In the present study, silver nanoparticles (Ag-NPs) were synthesized using Azadirachta indica extract and evaluated for their in vitro antioxidant activity and cytotoxicity efficacy against MCF-7 and HeLa cells. The silver nanoparticles (Ag-NPs) were formed within 40 min and after preliminary confirmation by UV-visible spectroscopy (peak observed at 375 nm), they were characterized using a transmission electron microscope (TEM) and dynamic light scattering (DLS). The TEM images showed the spherical shape of the biosynthesized Ag-NPs with particle sizes in the range of 10 to 60 nm, and compositional analysis was carried out. The cytotoxicity and antioxidant activity of various concentrations of biosynthesized silver nanoparticles, Azadirachta indica extract, and a standard ranging from 0.2 to 1.0 mg/mL were evaluated. The 2,2-Diphenyl-1-picrylhydrazyl (DPPH) activity of the biosynthesized Ag-NPs and aqueous leaf extract increased in a dose-dependent manner, with average IC₅₀ values of the biosynthesized Ag-NPs, aqueous leaf extract, and ascorbic acid (standard) of 0.70 ± 0.07, 1.63 ± 0.09, and 0.25 ± 0.09 mg/mL, respectively. Furthermore, higher cytotoxicity was exhibited in both the MCF-7 and HeLa cell lines in a dose-dependent manner. The average IC₅₀ values of the biosynthesized Ag-NPs, aqueous leaf extract, and cisplatin (standard) were 0.90 ± 0.07, 1.85 ± 0.01, and 0.56 ± 0.08 mg/mL, respectively, with MCF-7 cell lines and 0.85 ± 0.01, 1.76 ± 0.08, 0.45 ± 0.10 mg/mL, respectively, with HeLa cell lines. Hence, this study resulted in an efficient green reductant for producing silver nanoparticles that possess cytotoxicity and antioxidant activity against MCF-7 and HeLa cells.

Indirect Impacts of COVID-19 on the Environment: A Global Review

Coronavirus (COVID-19) is an infectious disease caused by the SARS-CoV-2 virus, which has plagued the Earth for the past two years and brought much controversy along with it. This report aims to analyze how the Covid-19 pandemic has had indirect effects on the environment. The onset of the pandemic has not only caused havoc disrupting routine average and businesses, but also claimed at least five million lives worldwide. This prompted the governments and the World Health Organization (WHO) to formulate measures to contain the transmission and the impact of the disease on the populations. Quarantine measures, movement restrictions, lockdowns and curfews, and travel bans are some of the most effective response methods that have helped the world contain the pandemic's spread. The adopted measures have had an indirect impact on the environment, opening the global community to numerous opportunities and threats. This report provides a critical analysis of how the Covid-19 pandemic has had indirect effects on the environment, examining how the response and containment measures have affected the environment. It focuses on air quality, water demand and quality, climate change, afforestation and deforestation, wildlife resurgence, littering, traffic congestion, noise reduction and changed human activities. It explores how the Covid-19 containment measures have had an environmental impact with a keen interest in the earlier areas.

Physico-Chemical Characterization and Assessment of Cytotoxic and Genotoxic Effects of Poly-Ethylene-Glycol Coated and Uncoated Gold Nanoparticles on Human Kidney (HK-2) Cells

Although gold nanoparticles (Au-NPs) have been widely used in medicine for the diagnosis and treatment of patients due to their unique physicochemical properties, chemical stability and biocompatibility, recent reports have also highlighted their potential to induce toxicity to humans. In the present study, we investigated the toxic effects of uncoated and polyethylene glycol (PEG)-coated AuNPs on human kidney (HK-2) cells. Both forms of AuNP were synthesized and characterized using standard protocols. Dynamic Light Scattering (DLS), Zeta Sizer Nano ZS analyzer, Transmission Electron Microscopy (TEM), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) were used to measure their distribution, zeta potential/surface charge, morphological size, and Au concentrations, respectively. Cytotoxicity was measured by Cyto-Tox assay and trypan blue exclusion test. Oxidative stress (OS) was assessed by quantifying the levels of Glutathione (GSH), and Mitochondria Membrane Potential (MMP). Genotoxicity was assessed by single cell gel electrophoresis (Comet assay) and Chromosomal Aberration (CA) assay. Uncoated AuNPs significantly reduced cell viability, increased ROS, decreased GSH, depolarized the MMP, and induced significant DNA damage and chromosomal alterations including chromosome gaps, centric rings, breaks, deletions, and intra and inter-chromosome exchanges, in a concentration-dependent manner. PEG-coated AuNPs displayed lower cytotoxic and genotoxic effects, and did not produce any significant increase in ROS or significant decrease in GSH along with negligible polarization of the MMP. Hence, PEG-coated AuNPs are relatively less toxic than uncoated AuNPs and therefore, may have potential applications in nanomedicine.

Kolaviron ameliorates hepatic and renal dysfunction associated with multiwalled carbon nanotubes in rats

The increase in the exposure to carbon nanotubes (CNTs) and their incorporation into industrial, electronic, and biomedical products have required several scientific investigations into the toxicity associated with CNTs. Studies have shown that the metabolism and clearance of multiwalled CNTs (MWCNTs) from the body involve biotransformation in the liver and its excretion via the kidney. Since oxidative stress and inflammation underlines the toxicity of MWCNT, we investigated the ameliorative effect of kolaviron (KV), a natural antioxidant and anti-inflammatory agent, on hepatorenal damage in rats. Exposure to MWCNTs for 15 days significantly increased serum activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and lactate dehydrogenase thereby suggesting hepatic dysfunction. Kidney function, which was monitored by urea and creatinine levels, was also impaired by MWCNTs. Additionally, MWCNTs markedly increased myeloperoxidase activity, nitric oxide level, reactive oxygen and nitrogen species, and tumor necrosis factor level in both tissues. However, KV in a dose-dependent manner markedly attenuated MWCNT-induced markers of hepatorenal function in the serum and MWCNT-associated inflammation in the liver and kidney. Also, MWCNTs elicited significant inhibition of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase activities. There was a significant diminution in glutathione level (GSH) and enhanced production of malondialdehyde (MDA) in MWCNTs-exposed rats. KV treatment was able to significantly increase the antioxidant enzymes and enhance the GSH level with a subsequent reduction in the MDA level. Taken together, KV elicited ameliorative effects against hepatorenal damage via its anti-inflammatory and antioxidant properties. Thus, KV could be an important intervention strategy for the hepatorenal damage associated with MWCNTs exposure.

Correction to: Kolaviron via anti-inflammatory and redox regulatory mechanisms abates multi-walled carbon nanotubes-induced neurobehavioral deficits in rats

After publication of this paper, the authors discovered that the name of the first author, Isaac Adegboyega Adedara, was missing in the proof. Dr. Adedara's intellectual contributions to the present article include conception and design of the study, manuscript writing and approval of the final version of the manuscript.

Kolaviron via anti-inflammatory and redox regulatory mechanisms abates multi-walled carbon nanotubes-induced neurobehavioral deficits in rats

Exposure to multi-walled carbon nanotubes (MWCNTs) reportedly elicits neurotoxic effects. Kolaviron is a phytochemical with several pharmacological effects namely anti-oxidant, anti-inflammatory, and anti-genotoxic activities. The present study evaluated the neuroprotective mechanism of kolaviron in rats intraperitoneally injected with MWCNTs alone at 1 mg/kg body weight or orally co-administered with kolaviron at 50 and 100 mg/kg body weight for 15 consecutive days. Following exposure, neurobehavioral analysis using video-tracking software during trial in a novel environment indicated that co-administration of both doses of kolaviron significantly (p < 0.05) enhanced the locomotor, motor, and exploratory activities namely total distance traveled, maximum speed, total time mobile, mobile episode, path efficiency, body rotation, absolute turn angle, and negative geotaxis when compared with rats exposed to MWCNTs alone. Further, kolaviron markedly abated the decrease in the acetylcholinesterase activity and antioxidant defense system as well as the increase in oxidative stress and inflammatory biomarkers induced by MWCNT exposure in the cerebrum, cerebellum, and mid-brain of rats. The amelioration of MWCNT-induced neuronal degeneration in the brain structures by kolaviron was verified by histological and morphometrical analyses. Taken together, kolaviron abated MWCNT-induced neurotoxicity via anti-inflammatory and redox regulatory mechanisms.

State of the science review of the health effects of inorganic arsenic: Perspectives for future research

Human exposure to inorganic arsenic (iAs) is a global health issue. Although there is strong evidence for iAs-induced toxicity at higher levels of exposure, many epidemiological studies evaluating its effects at low exposure levels have reported mixed results. We comprehensively reviewed the literature and evaluated the scientific knowledge on human exposure to arsenic, mechanisms of action, systemic and carcinogenic effects, risk characterization, and regulatory guidelines. We identified areas where additional research is needed. These priority areas include: (1) further development of animal models of iAs carcinogenicity to identify molecular events involved in iAs carcinogenicity; (2) characterization of underlying mechanisms of iAs toxicity; (3) assessment of gender-specific susceptibilities and other factors that modulate arsenic metabolism; (4) sufficiently powered epidemiological studies to ascertain relationship between iAs exposure and reproductive/developmental effects; (5) evaluation of genetic/epigenetic determinants of iAs effects in children; and (6) epidemiological studies of people chronically exposed to low iAs concentrations.

A comparison of poly-ethylene-glycol-coated and uncoated gold nanoparticle-mediated hepatotoxicity and oxidative stress in Sprague Dawley rats

Background

Gold nanoparticles (GNPs) and their functional derivatives are of great interest because of their many biomedical applications. GNPs are increasingly being incorporated into new diagnostic and therapeutic approaches in medicine. Consequently, there has been a strong push to fully understand their interactions with blood components. The agglomeration of cells reflects the interaction of nanoparticles with blood components.

Methods

The main aim of this study was to compare the effects of poly-ethylene-glycol (PEG)-oated and uncoated GNPs on the generation of reactive oxygen species (ROS); on the actions of distinct hepatotoxicity biomarkers such as alanine (ALT) and aspartate (AST) aminotransferases, and alkaline phosphatase (ALP); and on the histology of liver tissues in the rat model. Four distinct doses of PEG-coated and uncoated GNPs (12.5, 25, 50, and 100 µg/kg body weight) were used. Each group consisted of three rats receiving an oral administration of PEG-coated and uncoated GNPs for 5 days with one dose per 24 hours. The control group consisted of three rats that received deionized water. Twenty-four hours after the last treatment, samples were collected following standard procedures.

Results

PEG-coated and uncoated GNPs enhanced the generation of ROS and the activity of serum aminotransferases (ALT/AST) and ALPs relative to the negative control. A liver histology assessment of GNP-exposed rats revealed statistically significant responses in the variation of the morphologies of tissues relative to those of the negative control. Nonetheless, uncoated GNPs demonstrated enhanced hepatotoxic outcomes relative to those of PEG-coated GNPs. The results demonstrated that both GNPs may be able to promote hepatotoxicity in Sprague Dawley rats through mechanisms of oxidative stress. However, uncoated GNPs have more harmful effects than PEG-coated GNPs relative to the negative control.

Conclusion

Taken together, the results of this study indicate that PEG-coated GNPs may be safer to use in nanomedicinal applications than uncoated GNPs. However, more studies must be performed to confirm the outcomes of PEGylation.

Low doses of multi-walled carbon nanotubes elicit hepatotoxicity in rats with markers of oxidative stress and induction of pro-inflammatory cytokines

The investigation into the potential health risks associated with the use of engineered nanoparticles is a major scientific interest in recent years. The present study elucidated the involvement of pro-inflammatory cytokines, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in carboxylated multi-walled carbon nanotubes (MWCNTs)-induced hepatotoxicity. Pubertal rats were exposed to purified MWCNTs at 0, 0.25, 0.50, 0.75 and 1.0 mg/kg for 5 consecutive days. Results indicated that exposure to MWCNTs caused liver damage evidenced by significant elevation in serum activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT) when compared with control. Moreover, MWCNTs significantly decreased superoxide dismutase (SOD) and glutathione S-transferase (GST) activities as well as glutathione level whereas it significantly increased catalase (CAT) and glutathione peroxidase (GPx) activities in liver of the treated rats. Moreover, the dose-dependent increase in hepatic hydrogen peroxide (H₂O₂) and lipid peroxidation levels were accompanied by marked increase in micronucleated polychromatic erythrocytes (MNPCE) in the MWCNTs-treated rats. Administration of MWCNTs significantly increased serum concentrations of pro-inflammatory cytokines namely interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in the treated rats. Immunohistochemical analysis showed significantly increased COX-2 and iNOS protein expressions in the liver of MWCNTs-treated rats. In conclusion, carboxylated MWCNTs induces hepatic damage via disruption of antioxidant defense systems, promotion of pro-inflammatory cytokines generation and expression of COX-2 and i-NOS in rats.

Biochemical and histopathological evaluation of Al2O3 nanomaterials in kidney of Wistar rats

The present study was conducted to evaluate the response of kidneys in Wistar rats following long-term exposure to Al2O3 nanomaterials (NMs). To achieve this objective, Al2O3 of three different sizes (30 nm, 40 nm and bulk) was orally administered for 28 days to 9 groups of 10 Wistar rats each at the dose of 500, 1000 and 2000 mg/kg/rat. A tenth group of 10 rats received distilled water and served as control. After 28 days of exposure the animals were sacrificed and the serum was collected and tested for the activity levels of creatinine and urea following standard methods. Induction of oxidative stress was also investigated by assessing thiobarbituric acid reactive substances (TBARS) (MDA), protein carbonyl, reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) activities. A histopathological evaluation was also performed to determine the extent of kidney damage. The results showed that both serum creatinine and serum urea levels increased significantly in the treated rats compared to control animals. The increase was found to be more in Al2O3-30 nm treated rats followed by Al2O3-40 nm and Al2O3-bulk treated rats in a dose-dependent manner. Further administration of Al2O3 significantly increased the activities of TBARS, protein carbonyl, catalase and decreased the activities of GSH and SOD in a dose-dependent manner in the kidney of rats compared with the control group. Histopathological evaluation showed significant morphological alterations in kidney tissues of treated rats in accordance with biochemical parameters. Taken together, the results of this study demonstrate that Al2O3 is nephrotoxic and its toxicity may be mediated through oxidative stress. Further, the results suggest that prolonged oral exposure to Al2O3 NMs has the potential to cause biochemical and histological alterations in kidney of rats at high concentration.

Biochemical and Histopathological Evaluation of Graphene Oxide in Sprague-Dawley Rats

Graphene and its derivatives are promising material for important biomedical applications due to their versatility. A detailed comprehensive study of the toxicity of these materials is required in context with the prospective use in biological setting. We investigated toxicity of Graphene Oxide (GO) in rats following exposure with respect to hepatotoxicity and oxidative stress biomarkers. Four groups of five male rats were orally administered GOs, once a day for five days, with doses of 10, 20 and 40mg/Kg GO. A control group consisted of five rats. Blood and liver were collected 24h after the last treatment following standard protocols. GO's exposure increased induction of Reactive Oxygen Species (ROS), activities of liver enzymes (Alanine ALT, Aspartate AST, Alkaline Phosphates ALP), concentration of Lipid Hydro Peroxide (LHP) and morphological alterations of liver tissue in exposed groups compared to control. The highest two doses, 20 and 40mg/kg, showed statistically significant (p<0.05) increases in the induction of ROS, activities of ALT, ALP, LHP concentration, and morphological alterations of liver tissue compared to control. However, AST activity showed no effect. The results of this study demonstrate that GO may be hepatotoxic, and its toxicity might be mediated through oxidative stress.

Abstract 172: Oxidative stress and hepatotoxicity induced by graphene oxide in Sprague-Dawley Rats

Graphene oxide (GO) has been extensively explored as a promising nanomaterial for applications in biology because of its unique properties. Therefore, systematic investigation of GO toxicity is essential to determine its fate in the environment and potential adverse health effect. The aim of this study was to investigate the effect of graphene oxide on the induction of reactive oxygen species (ROS), the activity of certain liver enzymes (Alanine ALT, Aspartate AST, alkaline phosphatases ALP), and concentration of lipid hydroperoxide (LHP) in serum and histopathological evaluation of liver tissue in Sprague-Dawley rats. Four groups of five male rats were orally administered GOs, once a day for five days, with doses of 0, 10, 20 and 40 mg/Kg GO. A control group was also made of five rats. Blood and liver were collected 24 h after the last treatment following standard protocols. GO’s exposure increased the induction of ROS, the activities of the liver enzymes (ALT, AST, ALP), concentration of lipid hydroperoxide (LHP) and morphological alterations of the liver tissue in exposed groups compared to control. The highest two doses, 20 and 40 mg/kg, showed statistically significant (p &lt; 0.05) increases in the induction of ROS, activities of ALT, ALP , LHP concentration, and morphological alterations of liver tissue compared to control. However, AST activity showed no effect. Taken together, the results of this study demonstrate that GO is hepatotoxic, and its toxicity may be mediated through oxidative stress.

Citation Format: Anita K. Patlolla, Paul B. Tchounwou. Oxidative stress and hepatotoxicity induced by graphene oxide in Sprague-Dawley Rats [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 172. doi:10.1158/1538-7445.AM2017-172

Cytogenetic evaluation of functionalized single-walled carbon nanotube in mice bone marrow cells

With their unique structure and physicochemical properties, single\-walled carbon nanotubes (SWCNTs) have many potential new applications in medicine and industry. However, there is lack of detailed information concerning their impact on human health and the environment. The aim of this study was to assess the effects, after intraperitoneal injection of functionalized SWCNTs (f-SWCNT) on the induction of reactive oxygen species (ROS), frequency of structural chromosomal aberrations (SCA), frequency of micronuclei induction, mitotic index, and DNA damage in Swiss-Webster mice. Three doses of f-SWCNTs (0.25, 0.5, and 0.75 mg/kg) and two controls (negative and positive) were administered to mice, once a day for 5 days. Bone marrow and peripheral blood samples were collected 24 h after the last treatment following standard protocols. F-SWCNT exposure significantly enhanced ROS, increased (p < 0.05) the number of SCA and the frequency of micronucleated cells, increased DNA damage, and decreased the mitotic index in exposed groups compared to negative control. The scientific findings reported here suggest that purified f-SWCNT have the potential to induce oxidative stress mediated genotoxicity in Swiss-Webster mice at higher level of exposure. Further characterization of their systemic toxicity, genotoxicity, and carcinogenicity is also essential. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1091-1102, 2016.

Responses of testis, epididymis, and sperm of pubertal rats exposed to functionalized multiwalled carbon nanotubes

The present study investigated the response of testes, epididymides and sperm in pubertal Wistar rats following exposure to 0, 0.25, 0.5, 0.75, and 1.0 mg kg(-1) functionalized multi-walled carbon nanotubes (f-MWCNTs) for 5 days. The results showed that administration of (f-MWCNTs) significantly increased the activities of superoxide dismutase, catalase, and glutathione peroxidase in a dose-dependent manner in both testes and sperm compared with control group. Moreover, the significant decrease in the activity of glutathione-S-transferase and glutathione level was accompanied with significant elevation in the levels of hydrogen peroxide and malondialdehyde in both testes and sperm of (f-MWCNTs)-treated rats. The spermiogram of (f-MWCNTs)-treated rats indicated significant decrease in epididymal sperm number, sperm progressive motility, testicular sperm number and daily sperm production with elevated sperm abnormalities when compared with the control. Exposure to (f-MWCNTs) decreased plasma testosterone level and produced marked morphological changes including decreased geminal epithelium, edema, congestion, reduced spermatogenic cells and focal areas of tubular degeneration in the testes. The lumen of the epididymides contained reduced sperm cells and there was mild to severe hyperplasia epithelial cells lining the duct of the epididymis. Collectively, pubertal exposure of male rats to (f-MWCNTs) elicited oxidative stress response resulting in marked testicular and epididymides dysfunction.

Toxicity Evaluation of Graphene Oxide in Kidneys of Sprague-Dawley Rats

Recently, graphene and graphene-related materials have attracted a great deal of attention due their unique physical, chemical, and biocompatibility properties and to their applications in biotechnology and medicine. However, the reports on the potential toxicity of graphene oxide (GO) in biological systems are very few. The present study investigated the response of kidneys in male Sprague-Dawley rats following exposure to 0, 10, 20 and 40 mg/Kg GO for five days. The results showed that administration of GOs significantly increased the activities of superoxide dismutase, catalase and glutathione peroxidase in a dose-dependent manner in the kidneys compared with control group. Serum creatinine and blood urea nitrogen levels were also significantly increased in rats intoxicated with GO compared with the control group. There was a significant elevation in the levels of hydrogen peroxide and lipid hydro peroxide in GOs-treated rats compared to control animals. Histopathological evaluation showed significant morphological alterations of kidneys in GO-treated rats compared to controls. Taken together, the results of this study demonstrate that GO is nephrotoxic and its toxicity may be mediated through oxidative stress. In the present work, however, we only provided preliminary information on toxicity of GO in rats; further experimental verification and mechanistic elucidation are required before GO widely used for biomedical applications.

Hepatotoxicity and Ultra Structural Changes in Wistar Rats treated with Al2O3 Nanomaterials

The present study was designed to evaluate the hepatotoxicity of aluminium oxide (Al2O3). To achieve this objective, Al2O3 of three different sizes (30nm, 40nm and bulk) was orally administered for 28 days to 9 groups of 10 Wistar rats each, at the dose of 500, 1000 and 2000 mg/Kg/rat. A tenth group of 10 rats received distilled water and served as control. After 28 days of exposure, the animals were sacrificed and the serum was collected and tested for the activity levels of aminotransferases (AST or GOT and ALT or GPT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) enzymes following standard testing methods. Reduced glutathione (GSH) content was also measured in the liver tissue to study the oxidative stress. A histopathological evaluation was also performed to determine the extent of liver injury. Study results indicated that the activity of both the aminotransferases (AST and ALT), ALP and LDH increased significantly in Al2O3 treated rats compared to control animals. The increase was found to be more pronounced with Al2O3 - 30nm followed by Al2O3 - 40nm and Al2O3 - bulk treated rats in a dose dependent manner. However reduced glutathione content showed a decline in the activity. Ultra structural assessment showed significant morphological changes in the liver tissue in accordance with biochemical parameters. Taken together, the results of this study demonstrated that Al2O3 is hepatotoxic and the smaller size of this nanomaterial appeared to be the most toxic while the compound in the bulk form seemed to be the least toxic.

Genotoxicity study of silver nanoparticles in bone marrow cells of Sprague-Dawley rats

The antimicrobial properties of silver nanoparticles (Ag-NPs) have resulted in their extensive application in consumer and health care products. Although Ag-NPs have great potential benefits, their side effects are unknown and seem inevitable due to their ability to reach the nucleus and damage genetic material. This study aimed to determine genotoxic potential of Ag-NPs using mitotic index (MI), DNA damage (comet assay), structural chromosome aberrations (SCA), micronuclei (MN) formation as genetic endpoints and induction of reactive oxygen species (ROS) as oxidative stress endpoint in bone marrow of Sprague-Dawley rats. Four groups of five male rats were orally administered Ag-NPs, once a day for five days with doses of 5, 25, 50, 100, mg/Kg. A control group was also made of five rats. Bone marrow samples were collected 24 h after the last treatment following standard protocols. Ag-NPs exposure significantly increased (p < 0.05) the induction of ROS, number of SCA, the frequency of micro-nucleated cells, damaged the DNA and decreased the mitotic index compared to negative control. The results suggest that Ag-NPs may have the potential to induce oxidative stress mediated genotoxicity in rats. Further characterization of their genotoxicity and also their potential health implications should be monitored regularly.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Silver nanoparticle-induced oxidative stress-dependent toxicity in Sprague-Dawley rats

Due to the intensive commercial application of silver nanoparticles (Ag-NPs), their health risk assessment is of great importance. For acute toxicity evaluation of orally administered Ag-NPs, induction of reactive oxygen species (ROS), activity of liver function enzymes [(alanine (ALT/GPT), aspartate (AST/GOT), alkaline phosphatase (ALP)], concentration of lipid hydroperoxide (LHP), comet assay, and histopathology of liver in the rat model were performed. Four groups of five male rats were orally administered Ag-NPs, once a day for five days with doses of 5, 25, 50, 100 mg/kg, body weight. A control group was also made of five rats. Blood and liver were collected 24 h after the last treatment following standard protocols. Ag-NPs exposure increased the induction of ROS, activities of the liver enzymes (ALT, AST, ALP), concentration of lipid hydroperoxide (LHP), tail migration, and morphological alterations of the liver tissue in exposed groups compared to control. The highest two doses, 50 and 100 mg/kg showed statistically significant (p < 0.05) increases in ROS induction, ALT, AST, ALP activity, LHP concentration, DNA damage, and morphological alterations of liver compared to control. Based on these results, it is suggested that short-term administration of high doses of Ag-NP may cause organ toxicity and oxidative stress.

Arsenic-induced biochemical and genotoxic effects and distribution in tissues of Sprague-Dawley rats

Arsenic (As) is a well documented human carcinogen. However, its mechanisms of toxic action and carcinogenic potential in animals have not been conclusive. In this research, we investigated the biochemical and genotoxic effects of As and studied its distribution in selected tissues of Sprague-Dawley rats. Four groups of six male rats, each weighing approximately 60 ± 2 g, were injected intraperitoneally, once a day for 5 days with doses of 5, 10, 15, 20 mg/kg bw of arsenic trioxide. A control group was also made of 6 animals injected with distilled water. Following anaesthetization, blood was collected and enzyme analysis was performed by spectrophotometry following standard protocols. At the end of experimentation, the animals were sacrificed, and the lung, liver, brain and kidney were collected 24 h after the fifth day treatment. Chromosome and micronuclei preparation was obtained from bone marrow cells. Arsenic exposure significantly increased (p<0.05) the activities of plasma alanine aminotransferase-glutamate pyruvate transaminase (ALT/GPT), and aspartate aminotransferase-glutamate oxaloacetate transaminase (AST/GOT), as well as the number of structural chromosomal aberrations (SCA) and frequency of micronuclei (MN) in the bone marrow cells. In contrast, the mitotic index in these cells was significantly reduced (p<0.05). These findings indicate that aminotransferases are candidate biomarkers for arsenic-induced hepatotoxicity. Our results also demonstrate that As has a strong genotoxic potential, as measured by the bone marrow SCA and MN tests in Sprague-Dawley rats. Total arsenic concentrations in tissues were measured by inductively coupled plasma mass spectrometry (ICP-MS). A dynamic reaction cell (DRC) with hydrogen gas was used to eliminate the ArCl interference at mass 75, in the measurement of total As. Total As doses in tissues tended to correlate with specific exposure levels.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Genotoxicity of silver nanoparticles in Vicia faba: a pilot study on the environmental monitoring of nanoparticles

The use of silver nanoparticles (AgNPs) in commercial products has increased significantly in recent years. Although there have been some attempts to determine the toxic effects of AgNPs in mammalian and human cell-lines, there is little information on plants which play a vital role in ecosystems. The study reports the use of Vicia faba root-tip meristem to investigate the genotoxicity of AgNPs under modified GENE-TOX test conditions. The root tip cells of V. faba were treated with four different concentrations of engineered AgNPs dispersion to study toxicological endpoints such as mitotic index (MI), chromosomal aberrations (CA) and micronucleus induction (MN). For each concentration, five sets of microscopy observations were carried out. The results demonstrated that AgNPs exposure significantly increased (p < 0.05) the number of chromosomal aberrations, micronuclei, and decreased the MI in exposed groups compared to control. From this study we infer that AgNPs might have penetrated the plant system and may have impaired mitosis causing CA and MN. The results of this study demonstrate that AgNPs are genotoxic to plant cells. Since plant assays have been integrated as a genotoxicity component in risk assessment for detection of environmental mutagens, they should be given full consideration when evaluating the overall toxicological impact of the nanoparticles in the environment.

Abstract 5463: Serum aminotransferases and alkaline phosphatases as biomarkers of hepatotoxicity in sprague-dawley rats exposed to silver nanoparticles

Nanoparticles are small scale substances (&lt;100 nm) used in biomedical applications, electronics, and energy production. Increased exposure to nanoparticles being produced in large scale industry facilities elicits concerns for the toxicity of certain classes of nanoparticles. In particular, the oral toxicity of silver nanoparticles is of concern to ensure public and consumer health. Due to the intensive commercial application of silver nanoparticles (Ag-NPs), health risk assessment of this nanoparticle is of great importance. The previous in vitro studies demonstrated that Ag-NPs caused toxicity in various cell-lines. However, toxicity of Ag NPs in vivo is largely lacking. This study evaluated the effect of Ag-NPs on the activities of specific liver enzymes such as aminotransferases (GOT/GPT), and alkaline phosphatases (ALP) which may be useful as biomarkers of hepatotoxicity. Four groups of five male rats each weighing approximately 80 + 2 g were orally administered once a day for five days with doses of 5, 25, 50 and 100 mg/kg BW of silver nanoparticles. A control group was also made of 5 rats. At the end of the experiment, serum samples were collected following standard protocols. The data obtained from the hepatotoxicity study clearly show that highest two dose 50 and 100 mg/kg of silver nanoparticles has statistically significantly increased the activity of serum aminotransferases (GOT and GPT) and alkaline phosphatases (ALP) when compared to control. The results demonstrate that Ag-NPs have the potential to induce hepatotoxicity in Sprague-Dawley rats. Our result does not imply that silver nanoparticles should be banned from use but more in vivo studies with histopathological characterization should be designed to confirm the results of this study.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5463. doi:1538-7445.AM2012-5463

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Study of hepatotoxicity and oxidative stress in male Swiss-Webster mice exposed to functionalized multi-walled carbon nanotubes

Carbon nanotubes (CNTs), the most promising material with unique characteristics, find its application in different fields ranging from composite materials to medicine and from electronics to energy storage. However, little is known about the mechanisms behind the interaction of these particles with cells and their toxicity. The aim of this study was to assess the effects, after intraperitoneal (ip) injection, of functionalized multi-walled carbon nanotubes (MWCNT) (carboxyl groups) on various hepatotoxicity and oxidative stress biomarkers (ROS, LHP, ALT, AST, ALP, and morphology of liver) in the mouse model. The mice were dosed ip at 0.25, 0.5, and 0.75 mg/kg/day for 5 days of purified/functionalized MWCNTs and two controls (negative; saline and positive; carbon black 0.75 mg/kg) as appropriate. Samples were collected 24 h after the fifth day treatment following standard protocols. Exposure to carboxylated functionalized MWCNT; the body-weight gain of the mice decreased, induced reactive oxygen species (ROS), and enhanced the activities of serum amino-transferases (ALT/AST), alkaline phosphatases (ALP), and concentration of lipid hydro peroxide compared to control. Histopathology of exposed liver showed a statistically significant effect in the morphological alterations of the tissue compared to controls. The cellular findings reported here do suggest that purified carboxylated functionalized MWCNT has the potential to induce hepatotoxicity in Swiss-Webster mice through activation of the mechanisms of oxidative stress, which warrant in vivo animal exposure studies. However, more studies of functionalization in the in vivo toxicity of MWCNTs are required and parallel comparison is preferred.

Cytogenetic evaluation of malathion-induced toxicity in Sprague-Dawley rats

Malathion is a well known pesticide and is commonly used in many agricultural and non-agricultural settings. Its toxicity has been attributed primarily to the accumulation of acetylcholine (Ach) at nerve junctions, due to the inhibition of acetylcholinesterase (AChE), and consequently overstimulation of the nicotinic and muscarinic receptors. However, the genotoxicity of malathion has not been adequately studied; published studies suggest a weak interaction with the genetic material. In the present study, we investigated the genotoxic potential of malathion in bone marrow cells and peripheral blood obtained from Sprague-Dawley rats using chromosomal aberrations (CAs), mitotic index (MI), and DNA damage as toxicological endpoints. Four groups of four male rats, each weighing approximately 60 ± 2g, were injected intraperitoneally (i.p.) once a day for five days with doses of 2.5, 5, 10, and 20mg/kg body weight (BW) of malathion dissolved in 1% DMSO. The control group was made up of four animals injected with 1% DMSO. All the animals were sacrificed 24h after the fifth day treatment. Chromosome preparations were obtained from bone marrow cells following standard protocols. DNA damage in peripheral blood leukocytes was determined using alkaline single-cell gel electrophoresis (comet assay). Malathion exposure significantly increased the number of structural chromosomal aberrations (CAs) and the percentages of DNA damage, and decreased the mitotic index (MI) in treated groups when compared with the control group. Our results demonstrate that malathion has a clastogenic/genotoxic potential as measured by the bone marrow CA and comet assay in Sprague-Dawley rats.

Comparative study of the clastogenicity of functionalized and nonfunctionalized multiwalled carbon nanotubes in bone marrow cells of Swiss-Webster mice

The development of nanotechnologies may lead to environmental release of nanomaterials that are potentially harmful to human health. Among the nanomaterials, multiwalled carbon nanotubes (MWCNTs) are already commercialized in various products which can be in direct contact with populations. However, few studies address their potential toxicity. Although a few reports on the cytotoxicity of carbon nanotubes (CNTs) have been published, very little is known about their toxicity or genotoxicity in mammalian cells. We have for the first time compared the clastogenic/genotoxic potential of functionalized and nonfunctionalized MWCNTs in bone marrow cells of Swiss-Webster mice; using mitotic index (MI), chromosome aberrations (CA), micronuclei (MN) formation, and DNA damage in leukocytes as toxicologic endpoints. Six groups of five male mice, each weighing ∼30 ± 2 g, were administered intraperitoneally, once a day for five days with doses of 0.25, 0.5, 0.75, mg/kg body weight (BW) of functionalized and nonfunctionalized MWCNTs. Four vehicle control groups (negative) and a positive control group (carbon black) were also made of 5 mice each. Chromosome and micronuclei from bone marrow cells and comet slides from leukocytes were examined following standard protocols. The results demonstrated that MWCNTs exposure significantly increased (P < 0.05) the number of structural chromosomal aberrations, the frequency of micronucleated cells and the level of DNA damage, and decreased the mitotic index in treated groups compared to control groups. MWCNTs were shown to be toxic at sufficiently high concentrations, however purified functionalized MWCNTs had a higher clastogenic/genotoxic potential compared to nonfunctionalized form of MWCNT. The results of our study suggest that exposure to MWCNT has the potential to cause genetic damage. Hence, careful monitoring should be done with respect to designing/synthesizing biocompatible carbon nanomaterials. Further characterization of their systemic toxicity, genotoxicity and carcinogenicity is also essential.

Abstract 4381: Biochemical and histopathological evaluation of mice exposed to functionalized single-walled carbon nanotube

Single walled carbon nanotubes (SWCNTs) with their unique physicochemical properties, have many potential new applications in medicine and industry such as sensors, implants or delivery systems. The biomedical application of single-walled carbon nanotubes requires a fundamental understanding of their fate and toxicological profile after administration. However, the toxicity of SWCNT is barely known when they are introduced into the blood circulation, which is especially vital for their biomedical applications. The aim of this study was to conduct biochemical analysis to determine the effect of purified/functionalized single-walled carbon nanotube (SWCNT) on the induction of reactive oxygen species (ROS), activities of specific liver enzymes such as aminotransferases (GOT/GPT), alkaline phosphatases (ALP), concentration of lipid hydro peroxide (LPO) and histopathology of liver, which may be useful as biomarkers of hepatotoxicity and oxidative stress. Three groups of five male mice each weighing approximately 30 + 2 g were injected intraperitoneally once a day for five days with doses of 0.25, 0.5, 0.75 mg/kg BW of functionalized SWCNT. A control group was also made of 5 mice. At the end of the experiment, samples were collected following standard protocols. Exposure to functionalized SWCNT was found to show an increase in the induction of ROS, activities of serum amino-transferases (GOT/GPT), alkaline phosphatases (ALP) and concentration of lipid hydro peroxide compared to control. Histopathological evaluation of liver showed a statistically significant effect in the liver tissue (hepatic fibrosis) compared to controls. The results demonstrate that purified functionalized SWCNT was able to induce hepatotoxicity and oxidative stress. Our result does not imply that CNTs should be banned from use but more in vivo studies with histopathological characterization should be designed in biological application.

Keywords: Single walled carbon nanotube, reactive oxygen species, lipid hydroperoxide, serum aminotransferases, alkaline phosphatases, Swiss-Webster mice, histopathology, hepatotoxicity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4381.

Oxidative stress, DNA damage, and antioxidant enzyme activity induced by hexavalent chromium in Sprague-Dawley rats

Chromium is a widespread industrial compound. The soluble hexavalent chromium Cr (VI) is an environmental contaminant widely recognized as carcinogen, mutagen, and teratogen toward humans and animals. The fate of chromium in the environment is dependent on its oxidation state. The reduction of Cr (VI) to Cr (III) results in the formation of reactive intermediates leading to oxidative tissue damage and cellular injury. In the present investigation, Potassium dichromate was given intraperitoneally to Sprague-Dawley rats for 5 days with the doses of 2.5, 5.0, 7.5, and 10 mg/kg body weight per day. Oxidative stress including the level of reactive oxygen species (ROS), the extent of lipid peroxidation and the activity of antioxidant enzymes in both liver and kidney was determined. DNA damage in peripheral blood lymphocytes was determined by single-cell gel electrophoresis (comet assay). The results indicated that administration of Cr (VI) had caused a significant increase of ROS level in both liver and kidney after 5 days of exposure, accompanied with a dose-dependent increase in superoxide dismutase and catalase activities. The malondialdehyde content in liver and kidney was elevated as compared with the control animals. Dose- and time-dependent effects were observed on DNA damage after 24, 48, 72, and 96 h posttreatment. The results obtained from the present study showed that Cr (VI) could induce dose- and time-dependent effects on DNA damage, both liver and kidney show defense against chromium-induced oxidative stress by enhancing their antioxidant enzyme activity. However, liver was found to exhibit more antioxidant defense than the kidney.

Cytogenetic effects of 1,1-dichloroethane in mice bone marrow cells

The major concern for the halogenated compounds is their widespread distribution, in addition to occupational exposures. Several chlorinated alkanes and alkenes were found to induce toxic effects. In this study, we investigated the genotoxic potential of 1,1-dichloroethane in the bone marrow cells obtained from Swiss-Webster mice, using chromosomal aberrations (CA), mitotic index (MI), and micronuclei (MN) formation as toxicological endpoints. Five groups of three male mice each, weighing an average of 24 +/- 2 g, were injected intraperitoneally, once with doses of 100, 200, 300, 400, 500 mg/kg body weight (BW) of 1,1-dichloroethane dissolved in ethanol. A control group was also made of three animals injected with ethanol (1%) without the chemical. All animals were sacrificed 24 hours after the treatment. Chromosome and micronuclei preparations were obtained from bone marrow cells following standard protocols. Chromatid and chromosome aberrations were investigated in 100 metaphase cells per animal and percent micronuclei frequencies were investigated in 1,000 metaphase cells per animal. 1,1-dichloroethane exposures significantly increased the number of chromosomal aberrations and the frequency of micronucleated cells in the bone marrow cells of Swiss-Webster mice. Percent chromosomal aberrations of 2.67 +/- 0.577, 7.66 +/- 2.89, 8.33 +/- 2.08, 14.67 +/- 2.51, 20.3 +/- 3.21, 28 +/- 3.61; mitotic index of 9.4%, 7.9%, 6.2%, 4.3%, 3.0%, 2.6% and micronuclei frequencies of 3.33 +/- 0.7, 7.33 +/- 0.9, 8.00 +/- 1.0, 11.67 +/- 1.2, 15.33 +/- 0.7, 18.00 +/- 1.7 were recorded for the control, 100, 200, 300, 400, and 500 mg/kg BW respectively; indicating a gradual increase in number of chromosomal aberrations and micronuclei formation, with increasing dose of 1,1,-dichloroethane. Our results indicate that 1,1-dichloroethane has a genotoxic potential as measured by the bone marrow CA and MN tests in Swiss-Webster mice.

Serum acetyl cholinesterase as a biomarker of arsenic induced neurotoxicity in sprague-dawley rats

Arsenic is an environmental toxicant, and one of the major mechanisms by which it exerts its toxic effect is through an impairment of cellular respiration by inhibition of various mitochondrial enzymes, and the uncoupling of oxidative phosphorylation. Most toxicity of arsenic results from its ability to interact with sulfhydryl groups of proteins and enzymes, and to substitute phosphorus in a variety of biochemical reactions. Most toxicity of arsenic results from its ability to interact with sulfhydryl groups of proteins and enzymes, and to substitute phosphorus in a variety of biochemical reactions. Recent studies have pointed out that arsenic toxicity is associated with the formation of reactive oxygen species, which may cause severe injury/damage to the nervous system. The main objective of this study was to conduct biochemical analysis to determine the effect of arsenic trioxide on the activity of acetyl cholinesterase; a critical important nervous system enzyme that hydrolyzes the neurotransmitter acetylcholine. Four groups of six male rats each weighing an average 60 +/- 2 g were used in this study. Arsenic trioxide was intraperitoneally administered to the rats at the doses of 5, 10, 15, 20mg/kg body weight (BW), one dose per 24 hour given for five days. A control group was also made of 6 animals injected with distilled water without chemical. Following anaesthesia, blood specimens were immediately collected using heparinized syringes, and acetyl cholinesterase detection and quantification were performed in serum samples by spectrophotometry. Arsenic trioxide exposure significantly decreased the activity of cholinesterase in the Sprague-Dawley rats. Acetyl cholinesterase activities of 6895 +/- 822, 5697 +/- 468, 5069 +/- 624, 4054 +/- 980, and 3158 +/- 648 U/L were recorded for 0, 5, 10, 15, and 20 mg/kg, respectively; indicating a gradual decrease in acetyl cholinesterase activity with increasing doses of arsenic. These findings indicate that acetyl cholinesterase is a candidate biomarker for arsenic-induced neurotoxicity in Sprague-Dawley rats.

Cytogenetic evaluation of arsenic trioxide toxicity in Sprague-Dawley rats

Acute exposure to arsenic trioxide has been reported to induce death and/or multiple organ damage with symptoms including nausea, vomiting, diarrhea, gastrointestinal hemorrhage, cerebral edema, tachycardia, dysrhythmias and hypovolemic shock. Its toxic effects are due to its ability to bind to sulfhydryl groups of proteins and to inhibit energy production. Although the chronic exposure to arsenic trioxide has been linked to various types of cancer, such as skin, liver, lung, bladder and kidney neoplasms, studies of its carcinogenic potential in animals have not been conclusive. In this study, we investigated the genotoxic potential of arsenic trioxide in bone-marrow cells obtained from Sprague-Dawley rats; using chromosomal aberrations (CA), mitotic index (MI) and micronuclei (MN) formation as the toxicological endpoints. Four groups of six male rats each, weighing approximately 60+/-2 g per rat, were injected intraperitoneally, once a day for 5 days with doses of 5, 10, 15 and 20 mg/kg body weight (BW) of arsenic trioxide dissolved in distilled water. A control group was also made of six animals injected with distilled water without chemical. All the animals were sacrificed at the end of the treatment period. Chromosome and micronuclei preparation was obtained from bone-marrow cells following standard protocols. Arsenic trioxide exposure significantly increased the number of structural chromosomal aberrations, the frequency of micronucleated cells and decreased the mitotic index in treated groups when compared with the control group. Our results demonstrate that arsenic trioxide has a clastogenic/genotoxic potential as measured by the bone-marrow CA and MN tests in Sprague-Dawley rats.

Arsenic toxicity, mutagenesis, and carcinogenesis--a health risk assessment and management approach

A comprehensive analysis of published data indicates that arsenic exposure induces cardiovascular diseases, developmental abnormalities, neurologic and neurobehavioral disorders, diabetes, hearing loss, hematologic disorders, and various types of cancer. Although exposure may occur via the dermal, and parenteral routes, the main pathways of exposure include ingestion, and inhalation. The severity of adverse health effects is related to the chemical form of arsenic, and is also time- and dose-dependent. Recent reports have pointed out that arsenic poisoning appears to be one of the major public health problems of pandemic nature. Acute and chronic exposure to arsenic has been reported in several countries of the world where a large proportion of drinking water (groundwater) is contaminated with high concentrations of arsenic. Research has also pointed significantly higher standardized mortality rates for cancers of the bladder, kidney, skin, liver, and colon in many areas of arsenic pollution. There is therefore a great need for developing a comprehensive health risk assessment (RA) concept that should be used by public health officials and environmental managers for an effective management of the health effects associated with arsenic exposure. With a special emphasis on arsenic toxicity, mutagenesis, and carcinogenesis, this paper is aimed at using the National Academy of Science's RA framework as a guide, for developing a RA paradigm for arsenic based on a comprehensive analysis of the currently available scientific information on its physical and chemical properties, production and use, fate and transport, toxicokinetics, systemic and carcinogenic health effects, regulatory and health guidelines, analytical guidelines and treatment technologies.

Carcinogenic and systemic health effects associated with arsenic exposure--a critical review

Arsenic and arsenic containing compounds are human carcinogens. Exposure to arsenic occurs occupationally in several industries, including mining, pesticide, pharmaceutical, glass and microelectronics, as well as environmentally from both industrial and natural sources. Inhalation is the principal route of arsenic exposure in occupational settings, while ingestion of contaminated drinking water is the predominant source of significant environmental exposure globally. Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world, where a large proportion of drinking water is contaminated with high concentrations of arsenic. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioural disorders, diabetes, hearing loss, portal fibrosis, hematologic disorders (anemia, leukopenia and eosinophilia) and multiple cancers: significantly higher standardized mortality rates and cumulative mortality rates for cancers of the skin, lung, liver, urinary bladder, kidney, and colon in many areas of arsenic pollution. Although several epidemiological studies have documented the sources of exposure and the global impact of arsenic contamination, the mechanisms by which arsenic induces health effects, including cancer, are not well characterized. Further research is needed to provide a better understanding of the pathobiology of arsenic-induced diseases and to better define the toxicologic pathology of arsenic in various organ systems. In this review, we provide and discuss the underlying pathology and nature of arsenic-induced lesions. Such information is critical for understanding the magnitude of health effects associated with arsenic exposure throughout the world.

Carcinogenic and systemic health effects associated with arsenic exposure--a critical review

Arsenic and arsenic containing compounds are human carcinogens. Exposure to arsenic occurs occupationally in several industries, including mining, pesticide, pharmaceutical, glass and microelectronics, as well as environmentally from both industrial and natural sources. Inhalation is the principal route of arsenic exposure in occupational settings, while ingestion of contaminated drinking water is the predominant source of significant environmental exposure globally. Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world, where a large proportion of drinking water is contaminated with high concentrations of arsenic. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioural disorders, diabetes, hearing loss, portal fibrosis, hematologic disorders (anemia, leukopenia and eosinophilia) and multiple cancers: significantly higher standardized mortality rates and cumulative mortality rates for cancers of the skin, lung, liver, urinary bladder, kidney, and colon in many areas of arsenic pollution. Although several epidemiological studies have documented the sources of exposure and the global impact of arsenic contamination, the mechanisms by which arsenic induces health effects, including cancer, are not well characterized. Further research is needed to provide a better understanding of the pathobiology of arsenic-induced diseases and to better define the toxicologic pathology of arsenic in various organ systems. In this review, we provide and discuss the underlying pathology and nature of arsenic-induced lesions. Such information is critical for understanding the magnitude of health effects associated with arsenic exposure throughout the world.