Lead Pollution in Chicago

"What is the most common cause of lead exposure to people in Michigan?  Being transferred to Chicago."  Although said in jest, this statement may not be far from wrong.  Dangerous levels of lead pollute a large portion of the city of Chicago.  Lead levels in soil throughout the city are elevated.  In 1998 the Chicago Department of Public Heath conducted a large scale test to determine the blood lead levels in Children in different areas of the city.  The map below (property of and provided by the Chicago Department of Public Health) shows the areas where blood lead levels were found to be elevated.  The red zones indicate an area where over 25% of children tested had elevated blood lead levels.

The lead pollution in soils in and around Chicago is mainly from two sources.  Lead based paint is a major contributor to the elevated lead levels in Chicago, as is leaded gasoline.  Although lead-based paint is no longer used, many older homes have layers and layers of lead-based paint both inside and outside.  When these homes become dilapidated, the paint may peel off in small pieces and be deposited in the soil.  Also, in the early 1980's many old homes were being refurbished.  When the paint was stripped off of these homes, it was left on the ground and in this way a great deal of lead-based paint became deposited in soil.  A good portion of the lead contained in lead-based paint was in the form of lead carbonate PbCO3.  Most of the soil, and therefore the soil water in the Chicago areas has a pH of about 6.  Although lead is a solid and does not usually dissolve in water, when the water is slightly acidic the lead compound will dissolve to Pb2+ and CO32-.

Leaded gasoline has also contributed greatly to the elevated lead levels in soils that can be seen today.  The majority of lead from leaded gasoline is deposited on and around busy streets.  The lead is usually in the form of tetra ethyl lead which may dissolve to Pb2+ in the soil.  In the United States, between the 1930s and 1980s, the lead from leaded gasoline caused 5,000 deaths per year.  Children are affected the most by lead pollution because they are more likely to ingest lead.  For every 1 ug/m3 of Pb2+ in the air that is ingested by a child, that child will lose 1 IQ point.  Even if lead exposure is treated, the average child exposed to lead will not develop the IQ of the average child who has not been exposed to elevated lead levels.  Because Pb2+ is positively charged and the soil is negatively charged, Pb2+ will sorb to soil and will not wash out easily.  Therefore, Pb2+ deposited in the soil can still be a problem years later.  However, because it is sorbed tightly to soil, lead possesses less of a groundwater contamination problem.

The most important thing is for residents is to be aware of the problem so that lead ingestion can be prevented.  In most cases this simply means making sure that children do not eat paint chips, chew on painted surfaces like window sills, and do not eat soil from the yard or park.  No documents related to any lead clean-up efforts in the Chicago area could be located.