Reuters: London began spraying its roads with a dust suppressant on Friday to tackle its high air pollution levels. The capital is close to breaching European Union legal limits for particulate matter (PM10), a pollutant produced mainly by engine emissions along with tire and brake wear. London Mayor Boris Johnson hopes a six-month trial of the dust suppressant, designed to stop vehicle emissions re-circulating and choking residents, will cut PM10 levels by 10 to 20 percent. “We expect this new measure…