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Despite a significant reduction in smog-producing toxins in past decade, GTA still violates Canada’s ozone standards

August 21, 2014

TORONTO, ON — A new study shows that while the Greater Toron­to Area (GTA) has sig­nif­i­cant­ly reduced some of the tox­ins that con­tribute to smog, the city con­tin­ues to vio­late the Cana­da-wide stan­dards for ozone air pol­lu­tion.

Smog, which can cause or aggra­vate health prob­lems such as asth­ma, emphy­se­ma and chron­ic bron­chi­tis, is pro­duced by a set of com­plex pho­to­chem­i­cal reac­tions involv­ing volatile organ­ic com­pounds (VOCs), nitro­gen oxides and sun­light, which form ground-lev­el ozone. Smog-form­ing pol­lu­tants come from many sources includ­ing auto­mo­bile exhaust, pow­er plants, fac­to­ries and many con­sumer prod­ucts, such as paint, hair­spray, char­coal starter flu­id and chem­i­cal sol­vents. In a typ­i­cal urban area, at least half of the smog pre­cur­sors come from cars, bus­es, trucks and boats.

Research led by Jen­nifer Mur­phy of the Depart­ment of Chem­istry at the Uni­ver­si­ty of Toron­to has found that in the GTA between 2004 and 2012, nitro­gen oxides and VOCs were reduced by at least 20 per cent between 2004 and 2012.

“These reduc­tions are in line with the city’s 2007 com­mit­ment to reduc­ing smog pre­cur­sors, and can be attrib­uted to the imple­men­ta­tion of pol­lu­tion con­trol mea­sures like the Dri­ve Clean pro­gram, and the clo­sure of coal-fired pow­er plants in the region,” said Mur­phy.

Despite this good news, ozone con­cen­tra­tions are not fol­low­ing the same encour­ag­ing pat­terns. Cana­da-wide stan­dards for ozone con­tin­ued to be exceed­ed at all mon­i­tor­ing sta­tions in the GTA. While the team not­ed low­er ozone lev­els between 2008 and 2011 than in pre­vi­ous years, 2012 marked one of the high­est record­ed sum­mer ozone con­cen­tra­tions as well as a large num­ber of smog episodes.

Major smog occur­rences often are linked to heavy motor vehi­cle traf­fic, high tem­per­a­tures, sun­shine and calm winds. Weath­er and geog­ra­phy affect the loca­tion and sever­i­ty of smog. Because tem­per­a­ture and sun­light reg­u­lates the length of time it takes for smog to form, smog can occur more quick­ly and be more severe on a hot, sun­ny day.

“We are able to show that high ozone in 2012 was due to the rel­a­tive­ly high num­ber of sun­ny days that allowed ozone to be pro­duced quick­ly, and low winds, that allowed the pol­lu­tion to accu­mu­late local­ly,” said Mur­phy.

The team obtained the data from fed­er­al and provin­cial gov­ern­ment mon­i­tor­ing sites through­out the GTA between 2000 and 2012.  Their study, enti­tled “The impacts of pre­cur­sor reduc­tion and mete­o­rol­o­gy on ground-lev­el ozone in the Greater Toron­to Area,” was pub­lished in Atmos­pher­ic Chem­istry and Physics on August 15, 2014. Oth­er mem­bers of the U of T research team are Stephanie C. Pugliese, Jef­frey A. Ged­des and Jonathan M. Wang.

Full arti­cle:–8197-2014.pdf



Jen­nifer Mur­phy
Depart­ment of Chem­istry
Uni­ver­si­ty of Toron­to
Tel: 416–946-0260

Kim Luke
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to
Tel: 416–978-4352