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Hamilton Air Quality - Trends and Comparisons


Total Suspended Particulate

Total suspended particulate (TSP) includes all particulate material with diameters less than about 45 micrometers (µm). A substantial portion of TSP is composed of road dust, soil particles and emissions from industrial activities and transportation sources. TSP levels have been decreasing steadily since the mid-1970s.  Although monitored TSP emissions at industry sites show a recent increase as opposed to the declining trend at city-sited monitors, this is likely caused by increased transportation emissions in the area of the monitors rather than industrial emissions.  Total TSP emissions by Hamilton industrial facilities are essentially flat in recent year, down significantly from 2010.

Included within the TSP category are inhalable particulates (PM10) and respirable particulates (PM2.5). It is possible to determine the net amount of particulate material in the air with sizes between about 45 µm and either 10 µm or 2.5 µm, by subtracting the PM10 or the PM2.5 value respectively, from the TSP value. The material in the air with diameters between 10 and 45 µm is due almost exclusively to fugitive industrial emissions and road dust re-entrained by car and truck traffic.




Inhalable Particulate Matter (PM10)

Inhalable particulate matter (PM10), the airborne particles that have diameters of 10 µm or less, is a portion of total suspended particulate (TSP). PM10, which makes up about 40-50% of TSP in Hamilton, has been linked to respiratory, cardiovascular and other health impacts in humans.  Ambient levels of PM10 at the City sites have decreased about 21% over the past decade

 PM10 is derived primarily from vehicle exhaust emissions, industrial fugitive dusts, and the finer fraction of re-entrained road dust. While car and truck traffic counts have remained roughly constant over the past decade the deceasing trend of PM10 is likely the result of a combination of better performance of the vehicle fleet, better management of dust track-out by industries, and the use of better street sweepers and street sweeping practices by the City. The vehicle fleet performance will have improved primarily due to lower particulate emissions from modern engines and the removal of some of the worst polluting vehicles under the provincial Drive Clean program. While the impact of the Drive Clean program is difficult to assess from a local emissions perspective, the removal of “smoking vehicles” from the road is one of the expressed goals of the program, in addition to ensuring that the Ontario vehicle fleet is performing efficiently.



Respirable Particulate Matter (PM2.5)

The Province of Ontario monitors respirable particulate matter (PM2.5), airborne particles with a diameter of 2.5 µm or less. PM2.5, which makes up about 60% of the PM10 in the air, has been more strongly linked to health impacts than PM10.  Most of the PM2.5 in cities is derived primarily from vehicular emissions.

Most scientists now agree that exposure to the small particles and the organic substances is the likely cause of the observed respiratory and cardiovascular health impacts attributed to particulate material exposures.

The trend in PM2.5 showed a 3.5% per year decrease from 1999 until 2009 at the downtown and mountain AQI sites (consistent with decreasing trends in TSP and PM10 levels.) Over the past three to four years, however, these levels have remained relatively unchanged in cities across Ontario. The apparent increase in 2013 is not reflective of a change in air quality but is the result of the change in PM2.5 monitoring technology.

The Ontario government started measuring levels of PM2.5 across Ontario in 1999; prior to this date there was little data on PM2.5. In Hamilton PM2.5 data is collected at the three Air Quality Index (AQI) monitoring stations. In 2013 these stations were upgraded as part of an Environment Canada funded national initiative to standardize PM2.5 monitoring methods across Canada and ensure data comparability. The objective is to have all jurisdictions operating federally approved PM2.5 monitors by 2013.  The Ministry reported real-time PM2.5 with the Thermo Scientific TEOM 1400AB/SES until December 31, 2012. Continuous PM2.5 monitoring technologies have evolved dramatically over the last decade. The Ministry is now reporting real-time PM2.5 concentrations using Thermo Scientific SHARP 5030, an approved Class III Federal Equivalent Method designated by the United States Environmental Protection Agency in 2009.  The new SHARP monitor is able to detect additional components of PM2.5, especially during cold weather. As a result of this improvement in monitoring technology, there is potential of reporting higher PM2.5 concentrations during the winter months. This is a reflection of more accurate measurements and does not necessarily mean that the air quality is changing.  




The graph below shows a comparison of twelve-year trends in respirable particulate matter (PM2.5) levels in four Ontario cities. The trends in PM2.5 in Hamilton is mirrored at other locations across southern Ontario.





Ground Level Ozone

Ground level ozone (O3 or tropospheric ozone) is formed in the atmosphere when air pollutants such as nitrogen oxides (NOX) and volatile organic compounds (VOC) react in the presence of sunlight. Air levels of O3 are higher in warmer seasons than in cooler seasons because the sunlight is more intense in the summer and the temperatures are higher. The trend in O3 shows that the concentration have been highly variable over the past 10 years. Overall, the trend line for ozone is flat or increasing slightly.   


Unlike all other pollutants almost none of the O3 measured in Hamilton was generated from Hamilton-based pollution sources. The formation of O3 takes several hours once the pollutants have been released to the atmosphere. Thus, the O3 measured in Hamilton was produced from emissions released from sources upwind of Hamilton. Conversely, emissions from sources within Hamilton will result in the formation of O3 in areas downwind of Hamilton. A substantial portion of the O3 that affects southern Ontario during smog episodes in the summer months is known to originate from sources in the United States, primarily from coal-fired power plants, vehicles and urban activities in the Midwest Ohio Valley region.


Ground level ozone should not be confused with “stratospheric ozone” or “ozone layer”. The ozone called “stratospheric ozone” is produced and destroyed in the stratosphere at an altitude of 30-60 km above the Earth. The stratospheric ozone is commonly known as the ozone layer because over 91% of the ozone in Earth’s atmosphere is present here. The term “ozone depletion” refers to a decrease in the levels of stratospheric ozone due to man-made emissions, particularly halogenated refrigerants that have now been banned. Stratospheric ozone and changes in the ozone layer have not yet been linked to impacts of combustion emissions


The trend in O3 in Hamilton is mirrored at other locations across southern Ontario. Over the past 25 years, the concentrations of O3 across southern Ontario have increased between 10 and 30%, depending on the city. The levels of O3 observed across southern Ontario in recent years are consistently higher and more similar than what was observed one and two decades ago. This trend is somewhat worrisome given the detrimental health effects impacts associated with increased O3 exposures.








Sulphur Dioxide

Over 90% of the sulphur dioxide (SO2) in the air in Hamilton is the product of industrial activities within the City. 


Sulphur dioxide is not only a respiratory irritant but is converted in the atmosphere over several hours to sulphuric acid (H2SO4), which is then converted into sulphate particles. These particles average about 2 µm in diameter and constitute part of the respirable particulate fraction (PM2.5) in the air. These particles tend to be acidic in nature and cause lung irritation when inhaled. Thus, the health concerns associated with SO2 exposures are linked to the gas itself as well as to the sulphate particulate derived from it. During summer months, about 25% of the mass of PM2.5 in the air in southern Ontario is sulphate particulate.  Another 25% of the PM2.5 mass are nitrate salt particulates.










Nitrogen Dioxide

Nitrogen dioxide (NO2) is responsible for a significant share of the air pollution-related health impacts in Hamilton. NO2 is formed in the atmosphere from nitric oxide (NO) that is produced during the combustion of fuels such as gasoline, diesel, coal, wood, oil and natural gas. The leading sources of NO2 in Hamilton are the transportation sector followed by the industrial sector. The level of vehicle use across Hamilton has increased slightly during the past decade, while the overall emissions of NO (and hence NO2) from new vehicles continue to decrease due to improved engine technologies.  Since NO is the precursor of NO2, both NO and NO2 are routinely measured and their sum is reported as NOx to reflect the presence of both species in urban areas.  All of the NO is ultimately converted into NO2. The NO2 ultimately reacts with water in the atmosphere to produce nitric and nitrous acids (HNO3 and HNO2, respectively); these acids are converted into nitrate salts that constitute about 25% of the mass of fine particulate material or PM2.5.  The fact that 25% of the PM2.5 mass in urban centres is due to nitrate salts is a clear testament to the impacts of auto and diesel exhaust emissions on the atmosphere.


There has been a steady decline in the annual average levels of NO2 in Hamilton over the past decade, both at the downtown site and at a site downwind of the industries. Overall, improvements in vehicle emissions performance coupled with better industrial practices have resulted in an overall improvement in NO2 levels of about 40% over the past ten years.



When we compare the 25-year trends in air levels of NOx in Hamilton to NOx levels in other Ontario cities, we note that all cities have seen a steadily decreasing trend over the past decade. Toronto, which has no significant industrial NOx contributors but significant vehicular NOx emissions, has shown the largest decrease. Since the 1990’s both Toronto and London have seen reductions in NOx levels of approximately 60%. Hamilton’s NOx levels have decreased by approximately 46% since 1990. The NOx levels in Hamilton have decreased more slowly than in cities such as London and Toronto during this period, due presumably to contributions from sources other than vehicles. The NOx level is the sum of the levels of NO and NO2. The decrease in the average NOx levels is a reflection of improvements in emissions performance of the vehicle fleet in Ontario over the past decade.


When viewing the figure below, please note that some data points contain values based on a partial year. This data may not be as representative of annual NOx levels. Please view this figure as an approximate representation of NOx data from these cities.





Total Reduced Sulphur

Total Reduced Sulphur (TRS) is a measure of the volatile, sulphur-containing compounds that are the basis of many of the odour complaints related to steel mill operations, particularly coke oven emissions, blast furnace emissions and slag quenching operations. An odour threshold has been set at 10 parts per billion (ppb) TRS because at this level about one-half of any group of people can detect an odour similar to the smell of rotten eggs. There is a wide range of sensitivities to odours within the population. A common measure of odour impact on the population is the number of hours per year that TRS levels exceed the 10 ppb (parts per billion) threshold level.


The number of hours per year during which there were exceedences of the 10 ppb odour threshold have been reduced by over 90% since the mid-1990s due to significant changes in the management and operation of the coke ovens, blast furnaces and slag quenching operations. In particular, changes to slag procedures from quenching (using water) to pelletizing (using air cooling) have had a dramatic effect on reducing odour-causing emissions from slag handling operations. 




Benzene is a carcinogenic volatile organic pollutant emitted from some operations within the steel industry, specifically coke ovens and coke oven by-product plant operations.  Air levels of benzene have been reduced dramatically since the late 1990s, due to significant upgrading of the coking plant operations, improved operating procedures at the coke plants, and improved control of release of benzene vapours from the coke by-products plants.


Benzene is also a significant component of gasoline; benzene concentrations in gasoline can be up to 5%.  In other words, since benzene is volatile, benzene vapours can be detected in the air in areas where gasoline is pumped and distributed. Thus, all cities in Canada have low but measurable levels of benzene in the air primarily due to the pumping of gasoline; whenever a person fills a gasoline tank, the gasoline vapours in the tank (which contain benzene) are displaced out of the tank into the atmosphere, potentially exposing anyone near the filled tank.  The State of California has had a system for many years on all gasoline and diesel pumps at filling stations whereby the displaced vapours from the gas tank during filling are transferred back to the in-ground tank from which the gas or diesel fuel has been pumped.  The reductions in volatile organics emissions (including benzene) to the air in California due to this practice are enormous.  

Significant reductions in benzene concentrations have been realized.  More work remains to be done to improve ambient air quality and reduce industrial emissions to move towards meeting the new provincial standard under O. Reg. 419/05 – Local Air Quality for benzene.  The MOECC has set out a new annual average air concentration for benzene of 0.45 μg/m3 to come into force on July 1, 2016.  Current ambient air levels in Hamilton and in other urban areas are above this new standard. 



Benzo[a]pyrene (BaP) is a pollutant capable of causing cancer in animals and humans. BaP is one member of a large class of chemical compounds called polycyclic aromatic hydrocarbons (PAH). PAH are emitted when carbon-based fuels such as coke, oil, wood, coal and diesel fuel are burned. The principal sources of BaP in Hamilton are releases from coke oven operations within the steel industry. The significant decreases in ambient BaP levels since the late 1990s are the result of improvements to the infrastructure of coke ovens themselves and increased attention to the operation and maintenance procedures for proper operation of the coke ovens.

While BaP is only one of many PAH released from coking operations, BaP is the most potent single PAH in the air and the most thoroughly studied of all PAH carcinogens (cancer-causing agents) in the scientific literature. As a result of the extensive amount of chemical analysis, toxicological research and occupational exposure research done with this compound, BaP has become the primary PAH carcinogen by which exposures to many PAH-containing mixtures, such as vehicular emissions, coke oven emissions, barbecued foods, coal tar exposures, etc. are measured.


More work remains to be done to continue to improve ambient air quality and reduce industrial emissions.   The new provincial standard established by the MOE- under O. Reg. 419/05 – Local Air Quality for benzo(a)pyrene of 0.01 ng/m3 comes into force on July 1, 2016.   Reducing benzo (a) pyrene concentrations is a priority for the Ministry.  The MOECC continues to work closely with industries across the province and locally to reduce benzo(a)pyrene concentrations in ambient air.



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