Lead was widely used  to improve the performance of paint. It was used as a pigment, and also was known to improve the durability and appearance of painted surfaces. It is still used around the world for the same reasons.
The performance benefits of lead pale by comparison to the harmful effects it has on humans.
Growing children under the age of six can experience the most severe of side effects. Lead can hinder growth and development and is harmful to the nervous system and every organ of the body. While it is documented to be harmful to young children, adults can experience effects like reproductive problems.
Eating paint chips is not the only way it can hurt children. Dust from old paint during repainting and other renovations, if ingested can also be harmful.
Paint manufacturers for years now have improved paint performance without using lead.
While the debate south of the border is mostly based on the regulatory part of the lead issue, talk goes further than compliance and what someone can get away with.
Responsible Painting Contractors need to look at the well being of their customers and their own safety during renovations and painting of older homes.
The Paul, a remodeler in Minnesota, brings up some real points in an article in the Construction Remodel Forum.