With autumn weather here and midterms around the corner, it’s hard to think that summer was in full force last month: the flip-flops and sunscreen, the trips to the beach, and the smog days that made breathing difficult. But smog is not a thing of the past: a new study in the July issue of Atmospheric Environment confirms that come May, it will all be back.
Professor Jennifer Murphy, Canada Research chair in atmospheric and environmental chemistry, and graduate student Jeff Geddes have found that the last decade has seen no overall smog reduction in the GTA, despite programs enacted by municipal and federal governments.
Their study analyzed atmospheric nitrogen dioxide (NO2), ozone (O3), and volatile organic compound levels, finding that while both NO2 and VOC have decreased between 30 and 40 per cent across Toronto since 2000, the amount of tropospheric ozone, a major component of photochemical smog, has remained relatively unchanged. The lack of tropospheric ozone change is somewhat unexpected in light of Toronto’s clean-air efforts.
“Local clean-air efforts have focused mainly on reducing traffic and vehicle exhaust, which has led to dramatic reductions in nitrogen oxides and hydrocarbons—two key precursors to smog,” says Murphy.
The study reviewed NOx, O3, and VOC data available from the federal and provincial cooperative National Air Pollution Surveillance network. NAPS researchers measure NOx and O3 using automated continuous chemiluminescent and UV absorption analyzers respectively, and update the data annually.
Data collected by NAPS, however, is completed with the “mandate to answer ‘are we above or below a threshold?’” says Murphy. “They don’t have the research mandate to interpret the data.” After analyzing the data themselves, Murphy and Geddes concluded that smog-reduction efforts simply are not as effective as anticipated.
Murphy is an assistant professor of chemistry whose research focuses on ground-level air pollution. Her interest in photochemical ozone began during her PhD work at the University of California, where she studied the difference in nitrogen oxide levels on weekdays versus weekends, a difference predominately due to changes in diesel car traffic.
The Ontario government and City Hall have implemented several efforts—including improving vehicle technology, regulatory initiatives, and incentive programs—to control emissions of ozone-precursor compounds such as NO2 and VOC.
In 2000, the Canadian Council of Ministers of the Environment adopted a Canada-wide standard for particulate matter and ground level ozone. By 2010, ground-level ozone measurements in all Canadian jurisdictions should not exceed 65 ppb (parts per billion) over an eight-hour period. The formal recognition of the impact of smog on human health began in the early 1990s, when the CCME responded with a plan for the management of nitrogen oxides and volatile organic compounds. The initial plan featured over 16 codes of practice for reductions from various sources.
In 2007, Toronto put together a Climate Change and Clear Air Action Plan committed to cutting back by 20 per cent locally-generated smog-causing pollutants from 2004 levels with a deadline of 2012. The city is also peppered by a slew of additional air quality initiatives, including an idling control by-law, cycling promotion initiatives, and participation in the Greater Toronto Area Clean Air Council.
The Ontario environment and health ministries estimate that ground-level ozone costs the province several billion dollars in human health impacts and an additional $200 million in agricultural crop damages each year.
The continued presence of tropospheric ozone is largely due to it being a secondary pollutant, making its atmospheric levels difficult to predict and control.
“Ozone doesn’t come out of a tailpipe, it gets formed in the atmosphere from other pollutants that we emit. It’s not as easy to control as other things because it’s not a one-to-one relationship. So you can’t just stop driving and everything goes away,” says Murphy.
The study also reaffirmed a previously established correlation between smog days and high temperatures. “The number of days where the temperature is above 30 degrees Celsius is strongly correlated to smog days,” says Murphy.
Toronto is not alone in the battle with smog. The study points to long-term monitoring data in Japan and Taiwan that report steadily increasing ozone levels despite the implementation of clean-air efforts.
Does this mean the battle with smog is in vain? “Absolutely not,” says Murphy, “It is good to reduce the precursors of smog, but you can’t expect it to drop down immediately.”
