Queen Elizabeth's fleet of Rolls-Royces will be converted to run on lead-free gasoline, Buckingham Palace said Tuesday.

"The Queen's five Rolls-Royces can be easily converted and her two Daimler limousines are returning to the factory for conversion," a spokeswoman for Buckingham Palace said.The spokeswoman said the Queen's three Ford Granadas would need "an extensive rebuild," and her Vauxhall station wagon will be replaced because "it really is quite old." There will also be conversions made on a minibus and "a number of Land Rovers and Range Rovers."

The decision followed the Queen's attendence at a charity event Monday held in the Royal Mews, near Buckingham Palace, in which 100 children released 10,000 balloons carrying the words "I love lead-free," reflecting public concern over the effects on health of lead in gas fumes.

"We have been exceptionally fortunate to have found a cause close to Her Majesty's heart," said Lord Arnold Goodman, chairman of the charity Motability, which provides cars for disabled people and organized the balloon launch.