Source: https://yosemite.epa.gov/sab/sabproduct.nsf/87CB490D61F5E5988525745D00726335/$File/CASAC%20PbRP%20TeleConf%2006-09-2008%20Proposed%20Rule%20Pb%20NAAQS%20Surkan%20et%20al%20NeuroTox%202008.pdf