Addressing sulphur dioxide emissions from Ontario’s petroleum facilities

ERO number
Notice type
Environmental Protection Act, R.S.O. 1990
Posted by
Ministry of the Environment, Conservation and Parks
Notice stage
Proposal posted
Comment period
November 9, 2021 - December 24, 2021 (45 days) Open
Last updated

This consultation closes at 11:59 p.m. on:
December 24, 2021

Proposal summary

We are proposing a regulation to reduce sulphur dioxide air emissions from petroleum facilities in southern Ontario. These changes would help align the industry with other jurisdictions.

Proposal details


The Government of Ontario is taking more ambitious action to improve Ontario’s air quality and creating strong and effective standards for cleaner air that protects human health and the environment.

As part of this commitment, the ministry is working to regulate air contaminants released by certain industrial facilities. In particular, the Ministry is proposing to reduce sulphur dioxide (SO2) emissions from petroleum facilities.

Petroleum facilities in southern Ontario are a significant source of sulphur dioxide air emissions, particularly in Sarnia, where three of the province’s five major petroleum facilities are located.

Although the sector has made improvements to reduce emissions from their facilities, sulphur dioxide emission events and elevated ambient concentrations of the substance continue to be a concern in some communities where these facilities are located.

To help address these issues, the ministry is consulting on a new regulation that would reduce emissions of sulphur dioxide from petroleum facilities in Ontario. This proposed regulation would:

  • Over a defined time period, reduce SO2 emissions by approximately 90%;
  • Require implementation of certain management practices;
  • Maintain requirements for flaring events;
  • Provide facilities with regulatory certainty;
  • Require an immediate emissions reduction of up to 30% from heavy emitters; and,
  • Authorize the use of additional environmental penalties.

More details on the proposed regulation are provided in the Plain Language Overview that accompanies this notice, along with questions for public input.

The Government of Ontario invites feedback from the public, municipalities, First Nations, environmental groups, and industry on the proposed regulation in pursuit of cleaner air for all who live in Ontario.

Proposed regulation

The proposed regulation would apply to the existing five petroleum facilities in Ontario.

These facilities include:

  • Imperial Oil (Sarnia) (Nanticoke):
  • Shell (Sarnia);
  • Suncor (Sarnia); and,
  • Petro-Canada Lubricants (Mississauga)

These facilities would be required to address the discharge of sulphur dioxide by meeting emission limits for major sources, improving the management of key sources, enhancing onsite and offsite monitoring and increasing information sharing with First Nations and local communities. This approach would require facilities with higher sulphur dioxide emissions to do more to improve their performance.

The proposed regulation would limit sulphur dioxide emissions through the following requirements:

  • meet emission limits for key process units, including fluidized catalytic crackers, Houdry catalytic crackers and fluid cokers, and emission limits for sulphur recovery units by December 31, 2026
  • ending the combustion of solid fuel in combustion devices and restricting the use of fuel oil in combustion devices to emergency situations or supply constraints only

The proposal would require the facilities to implement the following management practices:

  • develop up-to-date sulphur dioxide emission minimization plans
  • conduct root cause analysis and develop and implement corrective and preventive actions for flares that release more than 225 kg of sulphur dioxide in a 24-hour period
  • conduct root cause analysis and develop and implement corrective and preventive actions for sulphur recovery units and non-flare combustion devices that emit more than 225 kg of sulphur dioxide above their allowable limits in a 24-hour period
  • develop continuous monitoring system plans for the design, installation, commissioning and operation of all required continuous monitoring systems
  • install and operate continuous monitoring systems for emissions from key process units, sulphur recovery units and flares and/or inputs to combustion devices and flares
  • operate and maintain at least one ambient air monitor for sulphur dioxide in the vicinity of each facility to track sulphur dioxide concentrations in the local community
  • mandate facility emissions data be shared with local First Nations and local municipalities
  • improve reporting to the ministry

The proposed regulation would maintain the requirements for flaring events that were established previously by Ontario Regulation 530/18: Air Pollution – Discharge of Sulphur Dioxide from Petroleum Facilities (O. Reg. 530/18).

The proposed regulation would provide facilities with regulatory certainty and allow time for investments in any equipment and improvements to processes that are needed to meet the new emission limits.

The proposed regulation would require an immediate emissions reductions of up to 30% from the heaviest emitting facilities. It would require the use of sulphur dioxide-reducing additives that are already effectively used in a number of facilities in other jurisdictions.

The Ministry is proposing to also authorize the use of additional environmental penalties to hold heavy emitters accountable for not meeting the proposed requirements.

If implemented, this regulation would significantly reduce emissions of sulphur dioxide from petroleum facilities and support improved health outcomes for the Sarnia, Nanticoke and Mississauga areas, and as well as local First Nations. As with other options available under the existing Local Air Quality Regulation (O. Reg. 419/05), the proposed compliance approach would provide an alternative to meeting the sulphur dioxide air standards.

Other actions

In addition to the proposed regulation, the Ministry is taking actions in the Sarnia area to address sulphur dioxide. Many of these activities fall under the Sarnia Air Action Plan, a ministry initiative to achieve better local air quality and improve communication and outreach.

The Ministry is undertaking the Sarnia Area Environmental Health Project to enhance our understanding of the links between environment and health and help address concerns that people have expressed about living close to industrial operations in this area.

Multi-source modelling is being conducted that will allow us to better assess local air quality and the relative contribution of different activities to sulphur dioxide concentrations in ambient air.

Real-time ambient air quality monitoring data for Sarnia is also available to the public on the Clean Air Sarnia and Area website.

Analysis of regulatory impact

Note: Analysis of regulatory impact is preliminary, and focuses on implementation of the proposed emission limits. It does not include the proposed interim requirement to use sulphur dioxide-reducing additives on Fluidized Catalytic Cracking Units.

The main impact of the proposal, if implemented, would be an improvement in health from the reduction of sulphur dioxide emissions from Ontario petroleum facilities. Additional benefits are improvements in fine particulate matter.

Health effects caused by exposure to high levels of sulphur dioxide include breathing problems, respiratory illness, and the exacerbation of respiratory and cardiovascular disease. People with asthma, chronic lung disease or heart disease are the most sensitive to sulphur dioxide. Sulphur dioxide damages trees and crops.

The proposal is expected to generate a net health benefit when the health benefits are compared to the costs of reducing emissions from the petroleum facilities.

Health Benefits

The proposal is expected to benefit all Ontarians. Levels of sulphur dioxide and fine particulate matter would be expected to improve across the province, particularly in Ontario’s southwest where the petroleum facilities are located.

Additional benefits are also expected from improved access to reporting about facility emissions and local air quality for local communities.


The main compliance costs incurred by facilities would consist of the costs of emission reductions to achieve the proposed emission limits. The facilities are assumed to generally require end-of-pipe technologies to control sulphur dioxide discharges.

The most important costs would be to install and operate wet gas scrubbers, if facilities choose to use them, to meet the emission limits for their catalytic cracking units and cokers. Facilities would also incur operating costs in the short-term to deploy sulphur dioxide reducing additives until the emission limits are met on their fluidized catalytic cracking units.


Our government takes sulphur dioxide emissions very seriously. We know that short-term exposure to sulphur dioxide can cause respiratory distress, especially in sensitive individuals such as those with asthma, and may cause difficulty breathing and increased asthma symptoms. In some cases, sulphur dioxide exposure can cause effects on the heart, which may result in hospital admissions or, in severe cases, premature death. We also know that long-term exposure to sulphur dioxide can damage crops, trees, and other vegetation. It is a precursor to acid rain and can contribute to the acidification of soils, lakes, and streams.

Sulphur dioxide emissions are a source of fine particulate matter, which is either emitted directly as primary particulate matter or forms as secondary particulate matter when sulphur dioxide reacts with other pollutants in the air. Some emission controls reduce both emissions of primary fine particulate matter and sulphur dioxide (e.g., wet gas scrubber). Fine particulate matter is associated with various negative health impacts, particularly on the respiratory and cardiovascular systems. Reduced fine particulate matter would be a co-benefit of addressing sulphur dioxide emissions under the proposed regulation.

The ministry recognizes that there are other important local sources of sulphur dioxide emissions besides the five petroleum facilities, particularly in the Sarnia Area. The ministry will continue to work with other Ontario-based industrial sectors to ensure that compliance options are in place when the new and updated sulphur dioxide air standards come into effect in 2023.

Supporting materials

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