title: A tiered approach.
authors: Maxine J
authors: MJ
authors: McCall
authors: Victoria A
authors: VA
authors: Coleman
authors: Jan
authors: J
authors: Herrmann
authors: Jason K
authors: JK
authors: Kirby
authors: Ian R
authors: IR
authors: Gardner
authors: Paul J
authors: PJ
authors: Brent
authors: Craig M
authors: CM
authors: Johnson
references: Proc Natl Acad Sci U S A. 2007 Feb 13;104(7):2050-5
references: 17267609
references: Environ Sci Technol. 2007 Dec 15;41(24):8484-90
references: 18200883
references: Environ Sci Technol. 2010 Oct 1;44(19):7509-14
references: 20839838
references: Chem Res Toxicol. 2012 Oct 15;25(10):2057-66
references: 22978249