Exposure Assessment of Vehicular Emitted Ultrafine Particles-Towards a Mechanistic Understanding

Dr. Yifang Zhu
Environmental Health Sciences Department
University of California at Los Angeles

Although increasing evidence has demonstrated toxic effects of vehicular emitted ultrafine particles (UFP, diameter < 0.1 mm), related epidemiological studies are limited mainly due to the complexity of UFP exposure assessment.  Unlike fine particulate  matter  of  diameter  2.5  mm  and  smaller  (PM2.5)  which  has  a  relatively homogeneous distribution within an urban air shed, UFP concentration changes rapidly as the distance from the emission source increases.  The highest human exposure to UFPs  occurs  on  and  near  roadways.    Their  unique  semi-volatile  properties  and fractal-like  morphology  make  existing  aerosol  dynamic  models  derived  from  non volatile spherical particles of limited use in assessing UFP’s environmental and public health impacts.  It is very important and necessary to fill the knowledge gap in UFP quantitative  exposure  assessments  by  systematically  study  their  transport  and  transform from emission sources, vehicle tailpipes, into microenvironments where high levels of human exposure occurs.  

Dr. Yifang Zhu is an Assistant Professor of Environmental Health Sciences in UCLA  School  of  Public  Health.    She  received  her  Ph.D.  in Environmental  Health Sciences from UCLA in 2003 and worked as an Assistant Professor in Environmental Engineering Department at Texas A&M University-Kingsville before she was recruited back  by  UCLA  in  2010.  Dr.  Zhu’s  research  interest  is  primarily  in  the  field  of environmental exposure assessment and aerosol science and technology. Specifically, she  is  interested  in  determining  the  data  necessary  to  fill  the  knowledge  gap  in quantitative  exposure/risk  assessments  on  vehicular  emitted  ultrafine  particles  that have shown higher toxicity than larger particles on a unit mass basis. Her current research focuses on identifying key factors that affect human exposure to ultrafine particles on and near roadways by measuring and modeling their emissions, transport, and  transformation  in  the  atmosphere  as  well  as  into  the  in-cabin  and  indoor  environments.  These  research  efforts  are  supported  by  two  prestigious  national awards, the National Science      Foundation (NSF)’s Faculty Early Career Development (CAREER) Award and the    Walter Rosenblith New Investigator Award from the Health Effects Institute.