You might think that with cars having catalytic converters, lead on the ground would not be much of a risk. However, cars had been belting out leaded petrol for years.
Lead does not biodegrage, decay or dissipate. Furthermore it gets absorbed by soil. It is not just cars that have introduced lead into our environment, lead paint, debris from demolished buildings and various industrial activities have deposited lead onto the ground in urban locations.
Lead can be introduced into homes on peoples' shoes through soil and dust. This creates a serious risk of exposure, particularly for children. Potential risks of lead exposure include brain damage, behaviour changes, slowed growth, poor mental and educational development and hearing problems and seizures.
Having a shoe-free home can considerably reduce the risk of lead exposure.