Lead is a heavy metal used in many materials and products. As a result of the extensive use of lead over several centuries, lead can be found in paint, dust, soil, water, air, and food.

However, the French authorities have tried to improve the situation of children regarding lead paint poisoning. National health experts agree that exposure to lead-contaminated dust from lead-based paint in older homes is the primary pathway of lead poisoning in young children. Lead dust settles quickly, is difficult to clean up, and can be invisible to the naked eye. Young children usually are poisoned through normal hand-to-mouth activity. .

Housing age is an important predictor of risk, because the lead content of paint varied substantially over the past century. During the first half of the twentieth century, the lead content of paint was marketed as a measure of its quality - the more lead the better. Prior to about 1940, leaded paints typically contained high amounts of lead

Consequently It is compulsory for a seller whose property was built before 1948 to control the quantity of lead in his paint, even under wallpaper.
Only Xray measurement allows the expert to be precise enough. This control is long because of the number of measures required. It should also be done very carefully.

The notaire needs a comprehensive report concerning not only the quantity of lead in painting but also its state in housing: cracks, moisture etc. which increase the risk of contamination.