Toxicity assessment of carbon black waste: A by-product from oil refineries.
In Singapore, approximately 30t/day of carbon-based solid waste are produced from petrochemical processes. This carbon black waste has been shown to possess physical properties that are characteristic of a good adsorbent such as high external surface area. Therefore, there is a growing interest to reutilize and process this carbon black waste into secondary materials such as adsorbents. However, the carbon black waste obtained from petrochemical industries may contain heavy metals that are hazardous to human health and the environment, hence restricting its full potential for re-utilization. Therefore, it is important to examine the possible toxicity effects and toxicity mechanism of carbon black waste on human health. In this study, inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis showed that the heavy metals, vanadium (V), molybdenum (Mo) and nickel (Ni), were present in the carbon black waste in high concentrations. Three human cell lines (HepG2 cells, MRC-5 cells and MDA-MB-231 cells) were used to investigate the toxicity of carbon black waste extract in a variety of in vitro assays. Results from MTS assays indicated that carbon black waste extract decreased the viability of all three cell lines in a dose and time-dependent manner. Observations from confocal microscopy further confirmed this phenomenon. Flow cytometry assay also showed that carbon black waste extract induced apoptosis of human cell lines, and the level of apoptosis increased with increasing waste concentration. Results from reactive oxygen species (ROS) assay indicated that carbon black waste extract induced oxidative stress by increasing intracellular ROS generation in these three human cell lines. Moreover, induction of oxidative damage in these cells was also observed through the alteration of glutathione (GSH) and superoxide dismutase (SOD) activities. Last but not least, by treating the cells with V-spiked solution of concentration equivalent to that found in the carbon black waste extract, V was identified as the main culprit for the high toxicity of carbon black waste extract. These findings could potentially provide insight into the hazards of carbon black waste extract and its toxicity mechanism on human cell lines.
NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, 138602, Singapore.
Xu
X
Zhen
NUS Environmental Research Institute, National University of Singapore, 1 Create Way, Create Tower #15-02, 138602, Singapore.
Wei Cheng
WC
Ng
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore.
Fendy
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore.
Yen Wah
YW
Tong
School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, 200240, China.
Yanjun
Y
Dai
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore. Electronic address: chenkg@nus.edu.sg.
Koon Gee
KG
Neoh
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore. Electronic address: chewch@nus.edu.sg.
Chi-Hwa
CH
Wang
D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D005978:Glutathione / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D007220:Industrial Waste / Q000009:adverse effects* / Q000032:analysis; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D019216:Metals, Heavy / Q000009:adverse effects / Q000032:analysis; D018613:Microscopy, Confocal; D010316:Particle Size; D059392:Petroleum Pollution / Q000009:adverse effects* / Q000032:analysis; D017382:Reactive Oxygen Species; D012846:Singapore; D053260:Soot / Q000032:analysis / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000378:metabolism
D007220:Industrial Waste; D019216:Metals, Heavy; D017382:Reactive Oxygen Species; D053260:Soot; D013482:Superoxide Dismutase; D005978:Glutathione
Apoptosis; Carbon black waste; Oxidative stress; Reactive oxygen species; Toxicity evaluation