Heavy metal contamination of soil and dust in homes built on an active municipal solid waste landfill in Tijuana, Mexico

This project characterized the levels of heavy metals in house dust and soil of homes on an active landfill in Tijuana, Mexico. Environmental samples were taken indoors (house dust) and outdoors (soil) from randomly selected homes on the landfill and from a similar socioeconomic area not on the landfill. Samples were digested by modified NIOSH method 7105. Analysis for heavy metals (Arsenic, Lead, Copper, Chromium, Zinc, and Cadmium) was carried out by ICP-MS. A total of 78 samples were collected, from 29 homes on the landfill and 10 homes not on the landfill. For all metals analyzed, median loading levels were higher from home exterior soil than from interior house dust for all metals except Cd for both landfill and non-landfill samples (0.001< p < 0.05 for all). However, metal levels inside the homes were significantly correlated with outside levels, implying that track-in of exterior dust was the major source of exposure in the home. Median metal loading levels were higher for landfill versus non-landfill interior house dust samples for all metals except Zn and Cd, though this difference was significant only for lead (p = 0.028). This is the first study to characterize heavy metal levels for soil and house dust of homes of people living on an active landfill. Over 2000 people including young children live in this area of Tijuana with many working as refuse scavengers. The results of this study show that this population has a potential increased risk for heavy metal exposure.