Figure 3 Box plot representing the timeline of lead
concentrations in soil of sites shown in Figure 1 in Torreon
Coahuila, except sites 1, 8, and 9. The first bar represents lead in
soil concentration in 1999 as a basal time before environmental
interventions began. The following bars represent lead in soil
concentrations during the time the study was held, from 2002 to
2006. Superfund cleanup goal for lead is of 400 ppm [1].