Owens Corning Composite Materials Canada GP Inc. - Approval of a site-specific air standard

Background

Owens Corning Composite Materials Canada LP operates the Guelph Glass facility (“the facility”) in Guelph, Ontario. Chromium compounds (hexavalent) are released to the atmosphere from glass melting operations at the facility, resulting from molten glass flowing through vessels containing chromium-based refractory brick.

Owens Corning Guelph previously requested and received a site-specific standard approval for chromium compounds (hexavalent) in 2016 (https://ero.ontario.ca/archive/012-5061) which expires on June 30, 2026. In 2025, Owens Corning Guelph submitted a request to the ministry for another site-specific standard for chromium compounds (hexavalent) for a duration of 10 years as the facility is still not able to comply with the general air standard for this contaminant. The Owens Corning Guelph request included an action plan to re-engineer the exhaust stacks serving the glass melting furnace and the forehearth to improve contaminant dispersion and to continue to review the technical feasibility and potential effectiveness of add-on control technologies for a period of 10 years.

The ministry has reviewed this request and is proposing to approve a site-specific air standard for chromium compounds (hexavalent) for a 5.5-year period. The site-specific standard is proposed to become increasingly stringent over the 5.5-year period. The proposed site-specific standard approval is attached in the Supporting Materials section of this notice.

Request Overview

Owens Corning Guelph is requesting a site-specific standard for chromium compounds (hexavalent) of 0.00133 micrograms per cubic metres (annual average) for a duration of 10 years. The requested site-specific standard value was calculated using an air dispersion model (AERMOD) and represents the maximum predicted concentration that can occur in the vicinity of the facility when emissions are at maximum levels and coincide with meteorological conditions that result in the highest predicted ground level concentration. The maximum predicted concentration occurs along the Owens Corning Guelph facility property line with lower concentrations (still above the air standard) predicted in nearby residential areas. Exceedance of an air standard does not mean that adverse effects will occur, but rather that the risk of such effects increases with the concentration, frequency and duration of exposure.

The ministry's current annual air standard for chromium compounds (hexavalent) is 0.00014 micrograms per cubic metres. It is derived from lifetime cancer risks associated with continuous exposure and corresponds to an incremental risk of 1‑in‑a‑million (10⁻⁶), which is considered negligible. The air standard is aimed at minimizing long‑term inhalation exposure to reduce cancer risk while also providing protection against other potential health effects.

Chromium compounds (hexavalent), also known as hexavalent chromium, is a toxic form of chromium that poses health risks, particularly through inhalation. It can damage genetic material (DNA), which underlies its carcinogenicity. Exposures to hexavalent chromium at high concentrations, well above the ministry’s air standard, can also cause non‑cancer effects mainly affecting the respiratory tract and lung function. Impacts on the kidneys, liver, immune system, and skin can occur with prolonged exposure to significantly elevated concentrations.

The Owens Corning Guelph site-specific standard request included an action plan to modify the exhaust stacks serving the glass melting furnace and the forehearth to improve contaminant dispersion, continue to review the technical feasibility and potential effectiveness of add-on control technologies (milestone 1), and potentially make process modifications which could affect discharges of chromium compounds (hexavalent) afterwards (milestone 2). Owens Corning Guelph proposed to complete this action plan over a period of 10 years and noted that the most significant portion of the reduction in concentrations of chromium compounds (hexavalent) at points of impingement is expected with the implementation of milestone 1.

Review of request

The ministry has reviewed the Owens Corning Guelph request and is proposing to approve a site-specific air standard for chromium compounds (hexavalent) for a total duration of 5.5 years. The duration of the proposed site-specific standards reflects the ministry’s opinion that the elements of milestone 1 of the action plan can be completed in a 5.5-year period and that the elements outlined in milestone 2 of the action plan do not significantly reduce levels beyond what will be achieved from milestone 1. Further, the proposed technical feasibility review of add-on control technologies can also be appropriately conducted within the 5.5-year period. The proposed approval includes increasingly stringent site-specific standard levels over the duration of the 5.5-year approval to reflect the phased implementation of the facility’s action plan, resulting in reduced contaminant concentrations in the surrounding community over time.

The proposed site-specific standard approval is attached in the Supporting Materials section of this notice.

Proposed Chromium Compounds (hexavalent) Site-Specific Standard approval:

• 0.00133 micrograms per cubic metres - from July 1, 2026 to December 31, 2026
• 0.00084 micrograms per cubic metres - from January 1, 2027 to December 31, 2027
• 0.00069 micrograms per cubic metres - from January 1, 2028 to December 31, 2031

Chromium Compounds (hexavalent) Environmental Compliance Approval Amendments

In addition to the proposed site-specific standard approval, the ministry is also proposing to amend Owens Corning Guelph’s Environmental Compliance Approval (ECA) to add terms and conditions related to chromium compounds (hexavalent) emissions that include:

• source testing requirements for chromium compounds (hexavalent) to accurately estimate emissions from the facility and to demonstrate ongoing performance/ compliance
• source testing requirements for total chromium and particulate to aid the evaluation of the technical feasibility of add-on controls and technical benchmarking
• reporting requirements regarding glass melting operations
• requirements for public reporting on the status of the action plan implementation and emissions reductions over time, and
• a requirement to prepare an engineering report to evaluate the technical feasibility of installing add-on controls for reducing emissions of chromium compounds (hexavalent) from the facility

Regulating air contaminants in Ontario

In Ontario, we regulate air contaminants to protect communities that reside close to industrial sites. Our regulatory approach has resulted in improvements in air emissions.

Ontario's Local Air Quality Regulation (O. Reg. 419/05: Air Pollution - Local Air Quality) works within the province's air management framework to address contaminants released to air in communities by various sources, including industrial and commercial facilities.

Air standards

We are working to ensure cleaner air for the people of Ontario by regulating air contaminants released into communities by local industrial and commercial facilities, including Owens Corning Guelph.

Our approach to improving local air quality starts with setting science-based standards to protect human health and the environment. The air standards are used to:

• assess the performance of regulated facilities
• identify those that need to do more to reduce their emissions

Facilities that are not able to meet an air standard due to technological or economic limitations may request a site-specific standard or register to a technical standard.

Site-specific standards

Site-specific standards are developed with public transparency through public meetings and consultations. They include technology benchmarking to determine what is feasible for a company to achieve in terms of controlling emissions of a contaminant over the period of the approval.

Compliance with a site-specific standard, just like a general air standard, must be demonstrated by using air dispersion modelling.

The ministry closely oversees the companies' progress to ensure that the desired results are achieved.

Subsection 35(1) of the Local Air Quality Regulation (O. Reg. 419/05) includes provisions for the approval of requests for site-specific standards and associated rules for making such requests. A site-specific standard may be set for a period of five to 10 years. If a facility receives a site-specific standard and meets that standard, then the facility is operating in compliance with O. Reg. 419/05. The site-specific standard becomes the legally enforceable standard for that facility for the time period of the site-specific standard. A facility may also request a subsequent site-specific standard. Further information regarding O. Reg. 419/05 and the site-specific standard process can be accessed at the ministry website (https://www.ontario.ca/page/rules-air-quality-and-pollution).

Other public consultation opportunities

Owens Corning Guelph shared information regarding their site-specific standard request through their public liaison committee meeting in January 2025. A summary of the feedback received during that meeting was provided in the Public Consultation Report included with the request submitted by Owens Corning Guelph.