Decades have passed since bans by the federal government have put an end to using lead in gasoline and paint. However, some parts of the urban soil continue to exceed safety levels of lead, a study made by the Duke University reports.
The researchers had mapped and analyzed the lead concentration in soil along 25 miles of streets besides Durham. Approximately 270,000 people reside in the city. The finding revealed that since 1970, lead levels in the soil have decreased generally. But the decrease is far more along streets than near foundations for residences.
Soil samples were collected near house foundations that dated earlier than 1978. The average lead level measured was 649mg/kg of urban soil whereas near streets it was 150mg/kg. Guidelines by the EPA state that levels over 400mg/kg can potentially cause health risks over the long term to children. This includes possible nervous system and brain damage, as well as issues while growing up.
The Alarming Presence In Urban Soil
Anna Wade, the lead author, said that the alarming factor was that lead levels of poorer, older neighborhoods were still over safe levels. Similar studies of mapping are going to be conducted in 5 or 6 different cities across the nation.
Wade added to mitigate the risks it is important to know where the risks of lead contamination persist. It is also important to know why different locations have different rates of decrease. But many cities do not have the resources to carry out the regular sampling across the city that is required for the data. The Duke team had to look at records from the 70s to find data that could be compared.
Daniel D. Richter, a Duke Professor specializing in soils, added that mitigating the exposure to lead has been mostly focused on reducing risks inside the home. This study is a reminder that the risk of exposure in the outdoors also exists. Lead levels in curbside urban soil have decreased gradually due to natural and human causes. These include stormwater runoff and accelerated erosion.
However, soil near the foundation does not get affected as much by such processes. Moreover, older homes also receive dust and chips from old paint that has lead. As such urban soil in such areas still poses a great risk.