Lead, Manganese, and Methylmercury as Risk Factors for Neurobehavioral Impairment in Advanced Age

Figure 5

Substantia nigra cell populations diminish with age, as shown by McGeer et al. [31]. At about age 72, about 40% of the cells have been lost. If the decline is accelerated by 0.1% per year, such a loss would occur at about age 64.