Heavy metals (lead, cadmium and zinc) from street dust in Monterrey, Mexico: ecological risk index

Street dust is widely recognized as one of the major non-point sources of heavy metal pollution and represents an important pathway for human exposure. Concentrations of heavy metals in 41 samples of street dust from six municipalities’ sampled zones on the Monterrey Metropolitan Area in Nuevo Leon, Mexico, were evaluated. The results of concentrations of metals from the downtown, eastern, southern and southeast zones follow the order of lead > zinc > cadmium with only at the downtown and east zones not detecting the presence of cadmium in the samples collected. For the other zones, the order was zinc > lead > cadmium. The downtown zone is characterized by its commercial activity and vehicular traffic, reaching values of 1590 mg kg −1 of lead per each 0.450 m 2 sampled on the averaged collected sample representative of an area of 25 m 2 . The non-impacted area showed concentrations of lead at 7.36 mg kg −1 , cadmium 0.25 mg kg −1 and zinc 70.5 mg kg −1 . Based on these values, the ecological risk indexes are within the moderate to the extremely high range of pollution in all zones except for the southwest. The potential ecological index shows that lead is present as a pollutant in all sampled points and contributes greatly to a very high ecological risk index observed in the downtown zone of the Monterrey Metropolitan Area.