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Nancy J. Thompson PhD MPH, Department of Behavioral Sciences & Health Education, Rollins School of Public Health, Emory University. 1518 Clifton Road NE, Atlanta, GA 30322. E-mail: nthomps@emory.edu
The authors declare that they have no conflict of interest with respect to this article. The views expressed in this paper are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.
© 2012 the authors.