Prioritizing Chemicals and Data Requirements for Screening-Level Exposure and Risk Assessment

Jon A. Arnot,^1* Trevor N. Brown,^1** Frank Wania,¹ Knut Breivik,^2,3 and Michael S. McLachlan⁴

¹Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada; ²Norwegian Institute for Air Research, Kjeller, Norway; ³Department of Chemistry, University of Oslo, Oslo, Norway; ⁴Department of Applied Environmental Science (ITM), Stockholm University, Stockholm, Sweden


Abstract

Background: Scientists and regulatory agencies strive to identify chemicals that may cause harmful effects to humans and the environment; however, prioriti­za­tion is challenging because of the large number of chemicals requiring evaluation and limited data and resources.


Objectives: We aimed to prioritize chemicals for exposure and exposure potential and obtain a quantitative perspective on research needs to better address uncertainty in screening assessments.


Methods: We used a multi­media mass balance model to prioritize > 12,000 organic chemicals using four far-field human exposure metrics. The propagation of variance (uncertainty) in Key chemical information used as model input for calculating exposure metrics was quantified.


Results: Modeled human concentrations and intake rates span approximately 17 and 15 orders of magnitude, respectively. Estimates of exposure potential using human concentrations and a unit emission rate span approximately 13 orders of magnitude, and intake fractions span 7 orders of magnitude. The actual chemical emission rate contributes the greatest variance (uncertainty) in exposure estimates. The human biotransformation half-life is the second greatest source of uncertainty in estimated concentrations. In general, biotransformation and biodegradation half-lives are greater sources of uncertainty in modeled exposure and exposure potential than chemical partition coefficients.


Conclusions: Mechanistic exposure modeling is suitable for screening and prioritizing large numbers of chemicals. By including uncertainty analysis and uncertainty in chemical information in the exposure estimates, these methods can help identify and address the important sources of uncertainty in human exposure and risk assessment in a systematic manner.


Key words: exposure, high throughput, organic chemicals, risk, uncertainty analysis. 


Environ Health Perspect 120:1565–1570 (2012). http://dx.doi.org/10.1289/ehp.1205355 [Online 20 September 2012]


Address correspondence to J.A. Arnot, Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON M1C 1A4, Canada. Telephone: 416 462 0482. Fax: 416 462 0482. E-mail: jon.arnot@utoronto.ca


*Current address: ARC Arnot Research and Consulting, Toronto, ON, Canada. **Current address: Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Leipzig, Germany.


Supplemental Material is available online (http://dx.doi.org/10.1289/ehp.1205355).


Partial funding for this research was provided by the Long-Range Research Initiative of the European Chemical Industry Association (CEFIC-LRI; LRI-ECO13-USTO-081212), the Natural Sciences and Engineering Research Council (NSERC) of Canada (postdoctoral fellowship to J.A.A.), and the Research Council of Norway (grant 196191 to K.B.). In addition, researchers at the University of Toronto receive funding from NSERC, Environment Canada, Health Canada, Canadian Foundation for Climate and Atmospheric Sciences, the United Nations Environmental Programme, the 7th Framework ­programme of the European Union, and the CEFIC.


The authors have consulted for government agencies such as Health Canada, Environment Canada, the U.K. Environment Agency, the U.S. Environmental Protection Agency, the Climate and Pollution Agency of Norway, and various chemical industry companies and organizations including ExxonMobil Biomedical Sciences, Dow Chemical, Unilever, and the European Oleochemicals and Allied Products Group. J.A.A. is currently employed by ARC Arnot Research & Consulting, a company that conducts scientific research and applied research to evaluate chemicals for their potential harmful effects to humans and the environment. J.A.A. has provided consultancy services to government agencies and the chemical industry and has received funding from government agencies and industry organizations on chemical exposure and risk assessment issues. K.B. is employed by the Norwegian Institute for Air Research, an independent, nonprofit institution offering integrated services and products within the analytical, monitoring, and consulting sectors. The authors certify that their freedom to design, conduct, interpret, and publish this analysis was not compromised by any of the sponsors of the included research.


Received 18 April 2012; Accepted 10 September 2012; Online 20 September 2012.