Owens Corning Composite Materials Canada GP Inc. - Environmental Compliance Approval (air)

The following is an overview of 2 common themes that were raised and the ministry’s response to each.

Comment #1: Concern with the site-specific standard process, granting Owens Corning Guelph another site-specific standard when they have already been granted a site-specific standard in 2016 (that expired on June 30, 2026). They were already given a decade to implement procedures to reduce emissions to an acceptable level.

Response: Ontario’s regulatory approach to improving local air quality starts with setting science-based standards. Under the Local Air Quality Regulation, we use air standards to assess the environmental performance of a regulated facility. Facilities that meet the air standards do not need to take any further action.

Since Ontario’s air standards are science-based and set without regard to the technical and economic feasibility of Ontario industries being able to comply with these standards, some facilities cannot meet an air standard due to unique technical or economic limitations. Under the Local Air Quality Regulation, facilities that do not meet the general air standard for a contaminant may request an alternative compliance approach, such as requesting and complying with a site-specific standard. Where a site-specific standard is set, it replaces the general air standard for the facility under the regulation; a facility that meets its site-specific standard is generally in compliance with the regulation. Site-specific standards are developed with full public transparency through public meetings and public comment periods.

Site-specific standards drive emissions reductions by requiring the implementation of best available control technology or methods to prevent, minimize or reduce emissions. The site-specific standard setting process includes technology benchmarking to determine what is feasible for a facility to achieve in terms of controlling emissions of a contaminant over a period of time (i.e., at least five years but not more than 10 years), and the site-specific standard is set at the minimum difference necessary from the general air standard. The ministry’s objectives for approving site-specific standards is to reduce air pollution levels as much as feasible with the goal of having the facility meet the general air standards over time.

The Owens Corning Guelph glass facility received a site-specific standard approval for chromium compounds (hexavalent) of 0.0024 micrograms per cubic metre in 2016, which expired on June 30, 2026. In 2025, Owens Corning Guelph submitted a request to the ministry for another annual site-specific standard but at a reduced level of 0.00133 micrograms per cubic metre for a duration of 10 years, as the facility has taken efforts to reduce its emissions for the past years but is still not able to comply with the general air standard for this contaminant. The current annual air standard for chromium compounds (hexavalent) is 0.00014 micrograms per cubic metre.

The ministry has reviewed this request and posted decisions for site-specific air standards for chromium compounds (hexavalent) for a total duration of 5.5 years (with expiry date of December 31, 2031). See ERO # 026-0478 for details of the decision notice. By phasing in increasingly stringent limits on concentrations of chromium compounds (hexavalent), the ministry is requiring Owens Corning Guelph to implement and expedite actions to progressively reduce annual off-site concentrations from current levels over the duration of the approval. Owens Corning Guelph’s action plan to reduce off-site levels of chromium compounds (hexavalent) includes modifications to the exhaust stacks serving the glass melting furnace and the forehearth to improve contaminant dispersion and continuing to review the technical feasibility and potential effectiveness of add-on control technologies. The ministry continues to oversee Owens Corning Guelph’s progress to improve air pollution levels in the community through continuous improvement to ensure they are achieving the desired results towards meeting the general air standard for chromium compounds (hexavalent).

In association with the site-specific standard approval, a number of new terms and conditions are included in the facility’s environmental compliance approval to reduce the off-site concentrations of chromium compounds (hexavalent) and manage potential risks to the community. The environmental compliance approval can be found in the supporting materials section below.

Comment #2: Concern with the health impact and cancer effects of chromium compounds (hexavalent). What is the ministry’s role?

Response: 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 current annual air standard for chromium compounds (hexavalent) is 0.00014 micrograms per cubic metre. 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.

Owens Corning Guelph’s requested annual site-specific standard value of 0.00133 micrograms per cubic metre 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. Based on the ministry’s technical review of the Owens Corning Guelph’s site-specific standard request, combined with the health risk interpretation of the requested site-specific standard value (that exceeds the annual air standard by 9.5-fold), it was concluded that the associated cancer risk is approximately 9.5 per million, which is elevated above the air standard, but within the ministry’s negligible‑risk range where levels require further reductions to manage potential elevated risks in the local community.

For this reason, the ministry is issuing site-specific standards for chromium compounds (hexavalent) to Owens Corning Guelph that are time limited and become more stringent over time to ensure that Owens Corning Guelph is implementing its proposed action plan as quickly as feasible to reduce air contaminant levels and exposure in the local community. The ministry continues to work with Owens Corning Guelph to drive strategies to reduce their emissions and work towards achieving compliance with the health‑protective air standard.