J Weuve, K T Kelsey, J Schwartz, et al. Delta-aminolevulinic acid dehydratase polymorphism and the relation between low level lead exposure and the Mini-Mental Status Examination in older men: the Normative Aging Study. (Occup Environ Med 2006;63:746–53). Reference 4 is incorrect and should read Bleeker ML, Lindgren KN, Ford DP. Differential contribution of current and cumulative indices of lead dose to neuropsychological performance by age. Neurology 1997:48:639–45.