Day 1 :
Professor of Environmental Analytical Chemistry at the University of the Witwatersrand, South Africa.
Keynote: Risk assessment and bioavailability of mercury from dust in gold mining areas in Johannesburg, South Africa
Time : 10:30-11:30
Ewa Cukrowska is a Professor of Environmental Analytical Chemistry at the University of the Witwatersrand, South Africa. She has received her MSc and PhD degrees from the Maria Curie-Skodowska University in Poland in 1982. Her research interests is in speciation of heavy metals in industrial, environmental and biomedical samples with development and application of different analytical techniques and remediation methods; metals transport, fate, seasonal changes, biological uptake with chemometric evaluation and modeling of solution equilibria. She has over 200 publications to her credit.
Risk assessment and bioavailability of mercury from dust in gold mining areas in Johannesburg, South Africa
Ingestion and inhalation have been identified as major pathways for exposure to many dust contaminants. Particle size affects dust deposition efficiency in the human respiratory system upon inhalation. The natural mechanisms are simulated by the use of different reagents having an increasing extractability power. The results obtained are operationally defined. Mercury bioavailability/bio-accessibility was assessed by determining the metal fraction leached out using simulated gastric and lung fluids together with chemical sequential extraction. Total mercury (HgTOT) concentration was determined in road dust. The results showed that HgTOT ranged from 323 to 1349 µg kg-1 for PM25 particle size fraction. The finer fraction (PM25) had the highest Hg concentration and distribution in the samples was as follows: HgINDUSTRIAL>HgCBD>HgRESIDENTIAL. In order to assess the mobility and bioavailability of mercury, Artificial Lung Fluid (ALF) representing the upper parts of the lung and Artificial Gastric Juice (AGJ) representing the stomach juice were used. ALF extracted 1.7% HgTOT while the AGJ leached out 0.5% Hg. Sequential extraction procedure demonstrated the predominance of non-soluble Hg species (90-98%) in studied dust samples. The most bioavailable Hg fraction (water, acid soluble fraction) averaged 2.0% of HgTOT. The results showed that gold mining and its related activities around Johannesburg are the major sources of mercury in the area.
Professor and Leader of the Sara and James Allen Comprehensive Lung Cancer Program at West Virginia University Cancer Institute, USA.
Time : 9:15-10:15
Yon Rojanasakul is a Professor and Leader of the Sara and James Allen Comprehensive Lung Cancer Program at West Virginia University Cancer Institute, USA. He is also a Guest Scientist at the National Institute for Occupational Safety and Health. He has received his PhD in Pharmaceutical Sciences from the University of Wisconsin-Madison in 1989 and has since worked as a full-time Faculty Member at West Virginia University. His research is in the areas of environmental toxicology, nanotechnology and molecular carcinogenesis. His research focus is on cellular and molecular mechanisms of lung carcinogenesis induced by environmental agents including nanomaterials and heavy metals and on nanomedicine and anticancer drug discovery. He has published over 250 peer-reviewed original research articles in reputable journals and has served as a Grant Reviewer for the NIH and NSF and as an Editorial Board Member for many scientific journals.
Nanomaterial carcinogenicity: Role of cancer stem cells and tumor microenvironment
Tumor Microenvironment (TME) has been recognized as a key determinant of tumorigenesis and metastasis, but how TME is affected by nanomaterials is largely unknown. We demonstrated that certain nanomaterials including Carbon Nanotubes (CNTs) can affect TME by activating Cancer-Associated Fibroblasts (CAFs) to promote tumor growth and metastasis of human lung cancer cells. This effect of CNTs is dependent on the physicochemical characteristics of CNTs such as tube wall number and surface reactivity and functionalization. Single-walled CNTs and to a lesser extent multi-walled CNTs and their COOH-functionalized forms strongly induce CAFs, which was shown to promote tumor formation of preexisting human lung cancer cells and CNT-transformed lung epithelial cells. The mechanism by which CNT-induced CAFs promote tumor growth involves acquisition of Cancer Stem Cells (CSCs) in the TME, which drives tumor growth and metastasis. Gene knockdown experiments showed that an expression of podoplanin on CAFs is essential for the tumor-promoting and CSC-inducing effects of CNTs. Together our findings indicate a novel role of TME in promoting CNT-induced carcinogenesis through the activation of podoplanin-associated CAFs that support CSC expansion and tumor growth. Our results also suggest the potential utility of podoplanin as a mechanism-based biomarker for CNT-induced malignancies.