First smog advisory issued in Ontario for 2008

TORONTO - It's a sure but unwanted sign of spring.

Ontario's Environment Ministry has issued a smog advisory for a large swath of southern, central and eastern Ontario for Friday and Saturday.

The advisory extends from Cornwall in the east, south to Niagara, west to London-Middlesex and north to Parry Sound.

Parry Sound showed the worst air quality Friday afternoon, with a reading of 51.

That's a level at which sensitive people may experience irritation when breathing and possible lung damage when physically active.

This is Ontario's first smog advisory of the year, but it's not a record -- the earliest advisory was issued in February 2005.