Lead poisoning, the No.1 environmental illness of children, is caused primarily by lead based paint in older homes /Illinois Department of Public Health/. About 75% of homes built before 1978 contain some lead-based paint. Lead paint was used both inside and outside of homes, especially on windows ,baseboards, trim and doors. The only way to know for sure if your home contains lead-based paint is to have it tested.

Eating paint chips is one way young children are exposed to lead. It is not the most common way that people are exposed to lead. Ingesting and inhaling lead dust that is created as lead paint "chalks", chips, or peels from deteriorated surfaces. Walking on small paint chips found on the floor, or opening and closing a painted frame window, can also create lead dust. Lead dust can settle on floors, walls, and furniture. Under these conditions, children can ingest lead dust from hand-to-mouth contact or in food. Settled lead dust can re-enter the air through cleaning, such as sweeping or vacuuming, or by movement of people throughout the house.

Lead poisoning can cause severe problems including coma and death. [ Illinois Department of Public Health].