By comparing the cellular toxicity, researchers found that environmental nanoparticles are more toxic than manufactured nanoparticles due to bounded organic compounds, inorganic salts as well as trace metals on the particles. Therefore, it is important to measure the concentration of environmental nanoparticles and quantify its chemical compositions accurately for the study of nanoparticle exposure and nanotoxicology. However, there hasn’t been any research team who is able to sample and analyze all chemical species of nanoparticles accurately.
As the results of this study, we demonstrated that the samples of nanoparticle could be collected accurately and good chemical mass closure (CMC) could be obtained. The analyzed chemical species include OC (organic carbon), EC (elemental carbon), water-soluble ions and elements. Good CMC was not achieved by previous researches due to VOC adsorption by the sampling filter leading to positive artifact of particle OC. This study proposed a method based on QBQ (quartz behind quartz) + QBH (quartz behind HEPA) to correct for the positive particle OC artifact. The research results were published in two journal papers in Atmospheric Environment and Aerosol Science and Technology, respectively. This year, we continued to conduct the samplings at the locations where city residents, students, drivers, tourists as well as workers are likely to expose to nanoparticles. In addition, the nanoparticle study was conducted at the dilution tunnel of a dynamometer and at an inspection station of diesel vehicles.
In the aspect of developing world-class tools for measuring and characterizing nanomaterials, this study takes the lead in using the VOC denuder for nanoparticle sampling. The denuder was installed at the inlet of the MOUDI (micro-orifice uniform deposit impactor) to remove the gaseous VOCs. Test results showed that the denuder could reduce the adsorption of VOCs on the quartz filter effectively. It is foreseeable that the PAHs and trace organics could be quantified accurately in the future. We also made new micro-orifices for impactor nozzles which have smoother shapes than those of the MOUDI to reduce particle loss in the nozzles and prevent particles from clogging the nozzles. A patent application was filed for this invention. In addition, this study setup a humidify control system to reduce particle bounce in the MOUDI for increasing the accuracy of nanoparticle collection. These new researches are very competitive in the world.
In the past two years, this study has reviewed the latest literature and written reports to bridge the domestic knowledge gaps on exposure and risk assessments of nanomaterials. Workshops on these topics were also held, where research capacity and knowledge gaps in our country were pointed out and suggestions for government were made. Based on the reports and latest literature in the ICON website, Environmental Science and Technology and Nano Letter journals from 2008-2009, we further reviewed the following ten topics including “toxicity assessment of nanomaterials”, “Current control strategy of nanomaterials in USA and EU”, “Influence of nanomaterials on ecology and organisms in water”, “Risk assessment of nanomaterials”, “dermal penetration of nanomaterials”, “Life cycle assessment of nanomaterials”, “control banding of nanomaterial exposure”, “strategy of nanomaterial exposure control” and “nanomaterials measurement and exposure assessment in the environment”. The report of the domestic knowledge gaps in exposure and risk assessment were written, the domestic research capacity was analyzed and finally the recommendations in the aspects of administration, regulation and technology development were made.