Canada-United States Air Quality Agreement: Progress Report 2016: Section 1
On this page
The Acid Rain Annex to the 1991 Agreement established commitments by both countries to reduce emissions of SO2 and NOX, the primary precursors to acid rain, from stationary and mobile sources. The commitments also included provisions for prevention of air quality deterioration, protection of visibility, and continuous monitoring of emissions. Reductions in SO2 and NOX emissions in both Canada and the United States between 1990 and 2014 have led to major decreases in the wet deposition of sulfate and nitrate over the eastern half of the two countries. Implementation of various regulatory and non-regulatory actions for more than two decades in Canada has significantly reduced emissions of SO2 and NOX and ambient concentrations. Similar implementation, especially of regulatory programs in the electric power sector, has significantly reduced emissions of SO2 and NOX and ambient concentrations in the United States as well.
Acid deposition, more commonly known as acid rain, occurs when emissions of SO2 and NOX, from power plants, vehicles, and other sources, react in the atmosphere (with water, oxygen, and oxidants) to form various acidic compounds that exist in either a wet form (rain, snow, or fog) or a dry form (gases and particles). These acidic compounds can harm aquatic and terrestrial ecosystems (particularly forests); affect human health; impair visibility; and damage automotive finishes, buildings, bridges, and monuments.
Wet deposition of sulfate and nitrate is measured by precipitation chemistry monitoring networks in Canada and the United States. The measurement data, presented in kilograms per hectare per year (kg/ha/yr), are the basis for binational spatial wet deposition maps.
Figure 1. 1990 Annual Wet Sulfate Deposition
Figure 1 shows the U.S.-Canada spatial patterns of annual wet sulfate (sea salt corrected) deposition in kilograms/hectare/year for 1990. It also shows that the lower Great Lakes region consistently received the highest wet sulphate and nitrate deposition in the 25-year period from 1990 to 2014. Sulfate deposition in 1990 exceeded 28 kilograms/hectare/year over a large area of eastern North America, while in 2014, only a small region around Lake Erie received more than 12 kilograms/hectare/year of sulfate.
Figure 2. 2014 Annual Wet Sulfate Deposition
Figure 2 shows the U.S.-Canada spatial patterns of annual wet sulfate (sea salt corrected) deposition in kilograms/hectare/year for 2014. Sulfate deposition in 1990 exceeded 28 kilograms/hectare/year over a large area of eastern North America, while in 2014, only a small region around Lake Erie received more than 12 kilograms/hectare/year of sulfate. The pattern illustrates that significant reductions occurred in wet sulfate deposition in both the eastern U.S. and eastern Canada.
Figures 1 and 2 show the spatial patterns of annual wet sulfate deposition of non-sea-salt sulfate, which is measured sulfate with the contribution of sea salt sulfate removed, in 1990 and 2014, respectively, along with point values at sites in less densely measured regions. Figures 3 and 4 show the patterns of wet nitrate deposition for the same years. The lower Great Lakes region consistently received the highest wet deposition of both sulfate and nitrate in the 25-year period. Sulfate deposition in 1990 exceeded 28 kg/ha/yr over a large area of eastern North America, while in 2014, only a small region around Lake Erie received more than 12 kg/ha/yr of sulfate. Similarly, nitrate deposition exceeded 21 kg/ha/yr in many parts of the northeastern United States and southern Ontario and Quebec in 1990, and it only exceeded 16 kg/ha/yr at a single site in 2014.
Figure 3. 1990 Annual Wet Nitrate Deposition
Figure 3 shows the U.S.-Canada spatial patterns of wet nitrate deposition in kilograms/hectare/year in 1990. It also shows that the lower Great Lakes region consistently received the highest wet sulfate and nitrate deposition in the 25-year period from 1990 to 2014. Nitrate deposition exceeded 21 kilograms/hectare/year in many parts of Northeastern United States and southern Ontario and Quebec in 1990, and it only exceeded 16/kilograms/hectare/year at a single site in 2014.
Figure 4. 2014 Annual Wet Nitrate Deposition
Figure 9 shows the U.S.-Canada spatial patterns of wet nitrate deposition in kilograms/hectare/year in 2014. It also shows that the lower Great Lakes region consistently received the highest wet sulfate and nitrate deposition in the 25-year period from 1990 to 2014. Nitrate deposition exceeded 21 kilograms/hectare/year in many parts of Northeastern United States and southern Ontario and Quebec in 1990, and it only exceeded 16/kilograms/hectare/year at a single site in 2014.
Reductions in wet nitrate deposition have generally been more modest than for wet sulphate deposition.
Actions driving SO2 emission reductions include the implementation of the Canada-Wide Acid Rain Strategy for Post-2000, which serves as the framework for addressing the issues related to acid rain. The goal of the strategy is to ensure that the deposition of acidifying pollutants does not further deteriorate the environment in eastern Canada and that new acid rain problems do not occur elsewhere in Canada.
In 2014, Canada’s total SO2 emissions were 1.1 million metric tons (1.3 million short tonsFootnote 1 ), about 64 percent below the national cap of 3.2 million metric tons (3.5 million short tons). The 2014 emissions level also represents a 63 percent reduction from Canada’s total SO2 emissions of 3.1 million metric tons (3.4 million short tons) in 1990 (see Figure 5).
The largest contribution of SO2 emissions originates from three industrial sectors: the non-ferrous smelting and refining industry; the upstream petroleum industry, which includes the exploration and production of crude oil; and electric power generation. These three sectors accounted for 76 percent of national SO2 emissions in 2014. The majority of overall reductions in national SO2 emission levels can be attributed to the SO2 emission reduction actions undertaken by the province of Ontario, mainly from the permanent closure of coal-fired electric power generation facilities.
Although Canada has been successful in reducing these acidifying pollutants, many areas across Canada are still exposed to concentrations that exceed the capacity of the soils and surface waters to neutralize the acidic deposition, most notably in eastern Canada. A number of measures are being undertaken to reduce SO2 and NOX emissions from certain industrial sectors as part of Canada’s Air Quality Management System (AQMS), which will also reduce the impact of acidifying pollutants on soils and surface waters.
Figure 5. Total Canadian SO2 Emissions, 1980–2014
Figure 5 shows Canadian national SO2 emissions in millions of metric tons from 1980 to 2014. The trend is decreasing. In 2016, Canada’s total SO2 emissions were 1.1 million metric tons, or about 64 percent below the national cap of 3.2 million metric tons. This also represents a 63 percent reduction from Canada’s total SO2 emissions in 1990.
Source: ECCC, 2016
The United States has met its commitment to reduce SO2 emissions. The national Acid Rain Program (ARP) and the regional Clean Air Interstate Rule (CAIR) were designed to reduce emissions of SO2 and NOX from the electric power sector. Since 1995, SO2 emissions have fallen significantly under these programs. These reductions occurred while the demand for electricity remained relatively stable and were the result of continued increases in efficiency, installation of state-of-the-art pollution controls, and the switch to lower emitting fuels. Most of the power sector emission reductions since 2005 were from early reduction incentives and stricter emission cap levels under CAIR.
The CAIR SO2 program began on January 1, 2010, and was replaced by the Cross-State Air Pollution Rule (CSAPR) SO2 program on January 1, 2015Footnote 2 .
Electric generating units in the ARP emitted 3.1 million short tons (2.8 million metric tons) of SO2 in 2014, well below the ARP's statutory annual cap of 8.95 million short tons (8.1 million metric tons). ARP sources reduced emissions by 12.6 million short tons (11.4 million metric tons) or 80 percent from 1990 levels and 14.1 million short tons (12.8 million metric tons) or 82 percent from 1980 levels (see Figure 6).
In 2014, sources in the CAIR SO2 program and the ARP collectively reduced SO2 emissions by 8.1 million short tons (7.4 million metric tons) or 72 percent from 2000 levels and 7.1 million short tons (6.5 million metric tons) or 69 percent from 2005 levels (before implementation of CAIR). All ARP and CAIR sources emitted a total of 3.2 million short tons (2.9 million metric tons) of SO2 in 2014. Annual SO2 emissions from sources in the regional CAIR SO2 program alone fell from 9.1 million short tons (8.2 million metric tons) in 2005 to 2.7 million short tons (2.4 million metric tons) in 2014, a 71 percent reduction. Between 2013 and 2014, SO2 emissions fell 48,000 short tons (44,000 metric tons) or 2 percent and were about 970,000 short tons (880,000 metric tons) below the regional CAIR emission budget.
In addition to the electric power generation sector, emission reductions from other sources not affected by the ARP or CAIR, including industrial and commercial boilers and refining, have contributed to an overall reduction in annual SO 2 emissions. National SO2 emissions from all sources fell from 23.1 million short tons (20.9 million metric tons) in 1990 to 4.7 million tons (4.3 million metric tons) in 2014, a reduction of 79 percent.
Figure 6. SO2 Emissions from ARP and CAIR Sources, 1980–2014
Figure 6 depicts combined emission and compliance data for both the United States Acid Rain Program (ARP) and Clean Air Interstate Rule (CAIR). ARP and CAIR were designed to reduce emissions of SO2 and NOx from the electric power sector. In 2014, sources in the CAIR program and the ARP collectively reduced SO2 emissions by 8.1 million short tons (7.4 million metric tons) or 72 percent from 2000 levels and 7.1 million short tons (6.5 million metric tons or 69 percent from 2005 levels (before implementation of CAIR). All ARP and CAIR sources emitted a total of 3.2 million short tons (2.9 million metric tons) of SO2 in 2014.
Notes: For CAIR units not in the ARP, the 2009 SO2 emissions were applied retroactively for each pre-CAIR year following the year in which the unit began operating.
There are a small number of sources in CAIR but not in the ARP. Emissions from these sources compose about 1 percent of the total emissions and are not easily visible on the chart.
Source: EPA, 2016
Canada has met its commitment to reduce NOX emissions from power plants, major combustion sources, and metal smelting operations by 100,000 metric tons (110,000 short tons) below the forecasted level of 970,000 metric tons (1.1 million short tons). This commitment is based on a 1985 forecast of 2005 NOX emissions.
Emissions of NOX from all industrial sources, including emissions from electric power generation, totaled 782,529 metric tons (860,782 short tons) in 2014. Transportation sources contributed the majority of NOX emissions in 2014, accounting for almost 55 percent of total Canadian emissions, with the remainder produced by the upstream petroleum industry (22 percent), electric power generation facilities (9 percent), and other sources. Canada continues to develop programs to further reduce NOX emissions nationwide. On June 29, 2016, Canada published the Multi-sector Air Pollutants Regulations to limit NOX emissions from industrial boilers, heaters, and stationary engines and to limit NOX and SO2 emissions from cement manufacturing facilities. The regulations establish Canada’s first ever mandatory national air pollutant emissions standards for major industrial facilities. The regulations will significantly reduce emissions that contribute to acid rain and smog. ECCC analysis predicts that the regulations will result in a reduction of 2.0 million metric tons (2.2 million short tons) of NOX emissions in the first 19 years (equivalent to taking all passenger cars and trucks off the road for about 12 years). These industrial emission requirements are a key element of Canada’s AQMS.
The United States has met its commitment to reduce NOX emissions. To address NOX emissions, the ARP NOX program requires emission reductions through a rate-based approach on certain coal-fired power plants, while CAIRFootnote 3 achieves emission reductions through a market-based, emission trading program from fossil fuel-fired power plants. Overall, NOX emissions have declined dramatically under the ARP, the former NOX Budget Trading Program (NBP), and the CAIR NOX program, with the majority of reductions coming from coal-fired units. Other programs—such as regional and state NOX emission control programs —also contributed significantly to the annual NOX emission reductions achieved by sources in 2014.
In 2014, sources in both the CAIR NOX program and the ARP reduced NOX emissions by 4.7 million short tons (4.3 million metric tons) or 73 percent from 1990 levels, 3.5 million short tons (3.1 million metric tons) or 67 percent from 2000 levels, and 2 million short tons (1.8 million metric tons) or 54 percent from 2005 levels. Together, all ARP and CAIR sources emitted a total of 1.7 million short tons of NOX in 2014 (see Figure 7).
Annual NOX emissions from sources in the CAIR NOX program alone fell from 2.7 million short tons (2.4 million metric tons) in 2005 to 1.2 million short tons (1.1 million metric tons) in 2014, a 56 percent reduction. Between 2013 and 2014, NOX emissions fell 12,000 short tons (11 thousand metric tons) or 1 percent. Please see the United States NOX programs for more detailed information.
In addition to ARP and CAIR, other NOX ozone season and annual programs, as well as state NOX emission control programs, contributed significantly to the NOX reductions that sources achieved in 2014. Annual NOX emissions from the power sector as well as all other sources fell from 25.2 million short tons (22.8 million metric tons) in 1990 to 12.5 million short tons (11.3 million metric tons) in 2014, a reduction of 50 percent.
Figure 7. Annual NOX Emissions from ARP and CAIR Sources, 1990–2014
Figure 7 depicts U.S. NOx emissions in millions of short tons from coal-fired power plants under the ARP NOx program and from fossil fuel-fired power plants under the CAIR NOx program. In 2014, sources in both the CAIR NOx program and ARP reduced NOx emissions by 4.7 million short tons (4.3 million metric tons) or 73 percent from 1990 levels, 3.5 million short tons (3.1 million metric tons) or 67 percent from 2000 levels, and 2 million short tons (1.8 million metric tons) or 54 percent from 2005 levels. All ARP and CAIR sources emitted a total of 1.7 million short tons of NOx in 2014.
Notes: For CAIR units not in the ARP, the 2009 annual NOX emissions were applied retroactively for each pre-CAIR year following the year in which the unit began operating.
There are a small number of sources in CAIR but not in the ARP. Emissions from these sources compose about 1 percent of the total emissions and are not easily visible on the chart.
Source: EPA, 2016
Canada has continued addressing the commitment to prevent air quality deterioration and ensure visibility protection by implementing the Canadian Environmental Protection Act, 1999 (CEPA 1999) and the Canadian Environmental Assessment Act, 2012 and by following the continuous improvement and keeping clean areas clean principles. These principles are included in Canada’s AQMS and the associated Canadian Ambient Air Quality Standards (CAAQS).
The British Columbia Visibility Coordinating Committee (BCVCC) continues to work towards developing a visibility management framework for the Lower Fraser Valley (LFV) in southwest British Columbia. Modeling work by Environment and Climate Change Canada (ECCC) has further strengthened scientific understanding of visual air quality, including the development of a statistical model to estimate light extinction from routine air quality measurements and investigations of the visibility impact of emission reduction scenarios. This modeling work has guided policy decisions to improve visual air quality.
The Visual Air Quality Rating (VAQR) is a new tool to inform residents and visitors about how air pollution can degrade scenic views in the LFV. The VAQR uses air quality measurements to categorize and report visual air quality and was launched through the BCVCC website in August 2015. Other public outreach activities include the development of a brochure outlining the sources and effects of visual air quality degradation and the creation of outreach displays on signs in public parks highlighting the links between haze and the natural environment.
ECCC contributed to BCVCC science activities, including a recently completed comprehensive photochemical modeling effort to test the potential impacts of possible future emission changes on visibility in the LFV region.
Additional activities have been undertaken in other parts of Canada as part of ECCC’s National Visibility Monitoring Pilot Study. Visibility monitoring pilot sites that were established in 2011 at Barrier Lake, Alberta and Wolfville, Nova Scotia continue to operate, as does the Abbotsford, British Columbia visibility supersite, which collects the full suite of visibility monitoring measurements including aerosol speciation, optical point measurements, and digital camera imagery. Data collection for inter-comparison studies has recently been completed at the Barrier Lake site. A National Air Pollutant Surveillance (NAPS) speciation sampler that operated at the Barrier Lake site from 2013–2015 allowed comparison with the co-located U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) sampler. At Egbert, Ontario, IMPROVE speciation data are being compared with data obtained from the Canadian Air and Precipitation Monitoring Network (CAPMoN) from 2005–2015. Analysis of the data will be completed in the coming year. If the Canadian methodology is found to be sufficiently sound for visibility measurements, it would open up the potential for expansion of visibility monitoring at speciation sites across Canada. In addition, an updated assessment of visibility conditions across Canada, using data from the NAPS speciation network from 2003–2012, has been completed and more recent data will be added as it becomes available.
The United States continues to address its commitment to air quality and visibility protection through several ongoing programs, including New Source Review (NSR) and the Regional Haze Rule. NSR pre-construction permitting programs apply both to areas that meet the National Ambient Air Quality Standards (NAAQS), i.e., attainment areas, and to areas that exceed the NAAQS, i.e. nonattainment areas. Nonattainment area permits for new or modified sources require air pollution controls that represent the lowest achievable emission rate (LAER), plus emissions offsets. Emissions offsets are actual emission reductions, generally obtained from sources in the vicinity of a proposed source or modification that offset the emission increase and provide a net air quality benefit.
Permits for new or modified sources in attainment areas are known as prevention of significant deterioration (PSD) permits and require air pollution controls that represent the best available control technology (BACT), as well as a demonstration that the project’s emissions will not cause or contribute to a violation of the NAAQS or PSD increments. The PSD program also protects the air quality and visibility in Class I areas (i.e., national parks exceeding 6,000 acres and wilderness areas exceeding 5,000 acres).
The Clean Air Act established the goal of improving visibility in the nation’s 156 Class I areas and returning these areas to visibility conditions that existed before human-caused air pollution. The 1999 Regional Haze Rule requires that states reach that goal by 2064. In July 2005, the U.S. Environmental Protection Agency (EPA) finalized amendments to the Regional Haze Rule, which required the installation of emission controls known as best available retrofit technology (BART) to existing major stationary sources. In addition to BART, the rule also requires states to assess progress toward visibility improvement that could be made by controlling other non-BART emission sources, referred to as “reasonable progress.” Additional information can be found on EPA’s Regional Haze Program.
Figure 8 shows the annual average “standard visual range” (the farthest distance a large, dark object can be seen during daylight hours) within the United States for the period 2010–2014. This distance is calculated using fine and coarse particle data from the IMPROVE network. Increased particle pollution reduces the visual range. The visual range under naturally occurring conditions without human-caused pollution in the United States is typically 45–90 miles (75–140 kilometers [km]) in the east and 110–150 miles (180–240 km) in the west. Additional information can be found on the IMPROVE program and visibility in U.S. National Parks.
Figure 8. Annual Average Standard Visual Range (km) 2010–2014
Source: U.S. National Park Service, 2016 (data from IMPROVE website.)
Commitments in the Agreement require Canada and the United States to apply continuous emissions monitoring or methods of comparable effectiveness to certain electric utility units. Both countries meet these commitments by using continuous emissions monitoring systems (CEMS) and rigorous reporting programs. Canada and the United States each monitor more than 90 percent of eligible SO2 emissions with CEMS.
Canada continues to meet its commitment to monitor and estimate emissions of NOX and SO2 from new and existing electric utility units with a capacity rating greater than 25 megawatts. CEMS, or other comparable monitoring methods, have had widespread use in Canada’s electric utility sector since the late 1990s. Currently, most new and existing base-load fossil steam plants and natural gas turbines with high emission rates operate CEMS technology. Coal-fired facilities, which are the largest source of emissions from the sector, have SO2 and NOX CEMS installed at more than 92 percent of their total capacity. In addition, under Canada’s National Pollutant Release Inventory, a mandatory reporting program, electric power generating facilities are required to report their air pollutant emissions (including NOX and SO2) annually. CEMS also serves as a testing approach to demonstrate compliance with the Multi-Sector Air Pollutants Regulations.
EPA has developed detailed procedures to ensure that sources monitor and report emissions with a high degree of precision, accuracy, reliability, and consistency. Most emissions of SO2, carbon dioxide, and NOX are measured with CEMS, which monitor important information such as the amount of pollution emitted from a smokestack (pollutant concentration) and how fast the emissions occur. In 2014, CEMS monitored over 99 percent of SO2 emissions from CAIR sources, including 100 percent from coal-fired units.
Additionally, other large emission sources that are equipped with pollution control devices are regulated under the Compliance Assurance Monitoring (CAM) rule. The CAM rule includes criteria that define the monitoring, reporting, and record keeping that should be conducted by a source to provide a reasonable assurance of compliance with emission limitations and standards. EPA rigorously checks the completeness, quality, and integrity of monitoring data. In addition to electronic audits, EPA conducts targeted field audits on sources that report suspect data.
Report a problem or mistake on this page
- Date modified: