The study assessed the risk to the health of the inhabitants of the metropolitan zone of the City of Mexico posed by the chemical elemental contamination present in PM(2.5) particles. PIXE (particle induced X-ray emission) analysis of particles identified 18 elements, thereby achieving an elemental characterization. In order to calculate the risk posed by each element, the dose of elemental exposure was considered in relation to the corresponding reference dose. This gave an elemental risk of less than 1 for the three age groups; however, when the additive risk is considered for each age group a value exceeding 1 is obtained. Hence, although no individual element represents a public health risk, a consideration of the total risk for each of the age groups shows that members of the population are at high risk of contracting any one of the diseases that can be caused by the elements present in PM(2.5).