Most dirt is not harmful, but there can be a quagmire of dangerous poisons mixed in with a patch. Many Americans are grateful the Consumer Product Safety Commission, in 1978, banned the sale of lead based paint to anyone who wanted to paint a house. But the long practice of using the lead ridden paint eventually caused the three feet of dirt surrounding many homes to become poisoned, making it unsafe for children to play.
Illnesses, and even deaths, made news in 1978, and still do. Over three decades later, lead still pollutes. If chips falling off the walls did not pollute a property, gasoline exhaust blew onto the property and seeped in or leaded cans were thrown on.