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Community Health & Epidemiology
FACULTY CANDIDATE PRESENTATION
Assessing Toxic Organic Contaminants of
Emerging Concerns Using Cost-Effective
Monitoring and Modeling Approaches
2:30 PM Thursday May 14th
Theatre C, Tupper Link
5850 College Street
Xianming Zhang PhD
Development within the chemical industry over the past half century has lead to rapid increases in the
quantity of chemical substances on the market. Of ~100 million substances registered in the Chemical
Abstract Services (CAS), over 30 000 substances are commercially produced in quantities of over 1 t/y
globally. Environmental monitoring, human exposure and adverse health impact assessments via
biomonitoring are expensive and currently limited to only a few hundred of these chemicals. In order
to address potential human exposure and adverse health effects for such a large number of chemicals
in commerce, in silico approaches are needed to rapidly screen and prioritize these chemical
substances for further in-depth toxicity testing and exposure assessments. Previous models for
exposure and hazard screening primarily focus on chemicals released to the outdoor environment and
human exposure from outdoor environmental media (food, water, air). However, increasing evidence
has indicated significant human exposure to chemicals could occur indoors and thus near-field
exposure pathways (e.g. inhalation, non-dietary ingestion, dermal permeation) need to be considered
when estimating total exposure.
In this presentation, I will introduce a quantitative model that links indoor chemical fate processes and
human exposure. I will highlight how chemical properties determine the relative importance of indoor
exposure via dermal permeation, inhalation, and non-dietary ingestion and how interactions between
occupants and the indoor environment affect chemical fate and human exposure indoors. With a case
study on 40 organic chemicals commonly present indoors, I will demonstrate how the modeled indoor
intake fractions and steady-state concentrations in humans can be used to identify chemicals with
assessment and regulatory priorities. with emerging concerns and regulatory priority.
Xianming Zhang PhD
Con’t.
Dr. Xianming Zhang obtained his PhD (2012) in environmental chemistry and M.Sc. (2008) in
environmental studies from the University of Toronto. During his master’s study, Dr. Zhang’s research
focused on flame-retardants and polychlorinated biphenyls (PCBs) in indoor environments. Through a
sampling campaign, he identified predominant sources of flame-retardants in the studied indoor
locations and developed a mass balance model to quantify indoor emissions and fate of the chemicals.
During his PhD, Dr. Zhang conducted an in-depth investigation on passive air sampling techniques for
monitoring semi-volatile organic chemicals. Using laboratory controlled experiments, mathematical
modelling and field sampling campaigns, Dr. Zhang elucidated and quantified factors (chemical
properties and environmental conditions) that govern chemical uptake and passive sampling rates and
established a passive sampling and instrumental analysis method for monitoring oganosiloxanes, a
group of contaminants with emerging concerns.
After his PhD, Dr. Zhang worked as a sessional lecturer (2012) at the University of Toronto Scarborough
and taught a course on modelling organic contaminants. Meanwhile, he received funding to develop a
human exposure module in the indoor chemical fate model he previously developed and applied the
model to screen human exposures and risks for a large number of indoor toxic organic chemicals. Since
September 2013, Dr. Zhang received an NSERC fellowship and has been working as a postdoc at the
Harvard School of Public Health and the School of Engineering and Applied Sciences at Harvard
University. Currently, Dr. Zhang uses integrated monitoring and modelling approaches and aims to
establish a quantitative link between environmental releases of perfluorooctane sulfanate (PFOS) and
immunotoxic effects on human populations. In addition to the primary research projects, Dr. Zhang
also worked on a few collaborative projects with researchers at Canadian government labs and other
international institutes to address broader questions on environmental contaminants and human
exposure.
Details on our website
dal.ca/community-health