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Regulation Decision Notice:   EBR Registry Number:   010-7190
Proposal to Amend Ontario Regulation 419/05: Air Pollution - Local Air Quality, made under the Environmental Protection Act, to include Ontario Air Standards for Nine (9) Contaminants.
Ministry of the Environment
Date Decision loaded to the Registry:
June 22, 2011
Date Proposal loaded to the Registry:
July 31, 2009
Keyword(s):   Air  |  Compliance  |  Standard  |  Legislation
Related Act(s):   Environmental Protection Act, R.S.O. 1990
Decision on Regulation:

On July 31, 2009, the Ministry of the Environment (MOE) posted a “Proposal to Amend Ontario Regulation 419/05: Air Pollution - Local Air Quality, made under the Environmental Protection Act, to include Ontario Air Standards for Nine (9) Contaminants” to the Environmental Registry (EBR #010-7190). That posting included proposed Upper Risk Thresholds (URTs) for the contaminants for inclusion in Schedule 6 (Upper Risk Thresholds) of O. Reg. 419/05. The MOE issued a decision on one of the nine contaminants (acrolein, EBR # 010-6241) on December 22, 2009. This decision notice is regarding provincial air standards for the remaining eight contaminants.

The MOE has amended Ontario Regulation 419/05: Air Pollution – Local Air Quality (O. Reg. 419/05) to introduce new or updated air standards for eight contaminants. These decisions have been based on an extensive evaluation of the toxicological properties of these contaminants, a review of rationales for developing air criteria in other regulatory agencies and comments received from stakeholders in Ontario through the public consultation process. 

The regulatory amendments include incorporation of the new or updated air standards into the appropriate schedules in O. Reg. 419/05 including updates to Schedule 3 ( Standards with Variable Averaging Times), Schedule 6 (Upper Risk Thresholds) and Schedule 7 (Contaminants with Updated Standards). Standards with variable averaging times (e.g. annual and 24-hour standards) have been incorporated into Schedule 3. All of the new or updated standards will take effect on July 1, 2016. 

The decisions on the new or updated standards are available by following the links provided in this notice. Decisions on the standards in the Schedule for the eight contaminants have been made as follows:

  • Benzene (010-7186):  0.45 µg/m3, annual average [Schedule 3]
  • Benzo-a-pyrene (as a surogate of total PAHs) (010-6213):  0.00001 µg/m3, annual average [Schedule 3]
  • 1,3-Butadiene (010-6214):  2 µg/m3, annual average [Schedule 3]
  • Chromium and Chromium Compounds (Metallic, Divalent and Trivalent) (010-6353):  0.5 µg/m3, 24-hour average [Schedule 3]
  • Chromium Compounds (Hexavalent) (010-6353):  0.00014 µg/m3, annual average [Schedule 3]
  • Dioxins, Furans and Dioxin-like PCBs (010-7193):  0.0000001 µg/m3, 24-hour average [Schedule 3]
  • Manganese and Manganese Compounds (010-6253):  0.4 µg/m3, 24-hour average [Schedule 3]
  • Nickel and Nickel Compounds (010-7188):  0.04 µg/m3, annual average [Schedule 3]
  • Uranium and Uranium Compound (in the PM10 fraction) (010-7192):  0.03 µg/m3, annual average [Schedule 3]

NOTE: For those companies who are not yet using new models, we have also expressed the new standards in 30 minute intervals.

O. Reg. 419/05 sets out, among other things, requirements for using an approved dispersion model, Emission Summary Dispersion Modelling (ESDM) report requirements, notification requirements, phase-in timelines and general prohibitions against exceeding the standards listed in the Schedules to the regulation. There are three (3) guidelines that support O. Reg. 419/05. These guidelines are: 

  • "Guideline for the Implementation of Air Standards in Ontario" (GIASO); 
  • "Air Dispersion Modelling Guideline for Ontario" (ADMGO); and
  • "Procedure for Preparing an Emission Summary and Dispersion Modelling Report" (ESDM Procedure).

NOTE: The MOE is planning to update the current guidelines (ESDM Procedure, GIASO, and ADMGO and other documents as needed) to reflect the amendments to the regulation.  GIASO outlines the site-specific standard setting process (formerly known as the altered standards process). 

An Upper Risk Threshold (URT) is determined for each contaminant. URTs are set out in Schedule 6 of O. Reg. 419/05. Exceedence of a URT requires a facility to notify the MOE immediately and submit an ESDM within 90 days (see section 30 of the regulation for details). The URT provides an upper boundary for risk to be managed while facilities work towards emissions reductions either within the phase-in period of the air standard (i.e., before the standard takes effect) or after phase in of the standard (i.e., when a facility is using best available technology under the site-specific standards process). URTs do not replace air standards but allow industry time to implement necessary emissions reduction controls that will reduce risks to local communities. There is no phase-in period associated with URTs.

The general method used to determine a URT is described in the GIASO. The framework for establishing, implementing and assessing URTs was established through consultation with stakeholders including public health associations. Generally, a URT is set as a multiple of a given standard. For substances with non-carcinogenic effects [manganese, dioxins, chromium and chromium compounds (metallic, divalent and trivalent)], the URT has been set as 10-fold higher than the standard (based on a 24-hour averaging period). For substances with carcinogenic effects [chromium compounds (hexavalent), benzo-a-pyrene], the URT has been set as 100-fold higher than the standard (based on a 24-hour averaging period). The setting of a URT may include consideration of other effects that may be of concern at higher exposure levels and this information may be used to adjust the URT from the default levels. Such information was considered in setting the URTs for benzene, and 1,3-butadiene. For example, the MOE reviewed the critical carcinogenic endpoint for 1,3-Butadiene and then considered both occupational limits and a chronic reference concentration based on reproductive effects, set the by state of Texas in its recent rationale document. Since the air standard for nickel is set to protect against both cancer and non-cancer effects, the URT is set based on the 10-fold non-cancer effect multiplier. Additional information on the toxicology of the eight contaminants is provided within the decision documents in this posting.

Upper Risk Thresholds, Schedule 6

  • Benzene:  100 µg/m3, 24-hour average
  • Benzo-a-pyrene (as a surogate of total PAHs):  0.005 µg/m3, 24-hour average
  • 1,3-Butadiene:  300 µg/m3, 24-hour average
  • Chromium and Chromium Compounds (Metallic, Divalent and Trivalent):  5 µg/m3, 24-hour average
  • Chromium Compounds (Hexavalent):  0.07 µg/m3, 24-hour average
  • Dioxins, Furans and Dioxin-like PCBs:  0.000001 µg/m3, 24-hour average
  • Manganese and Manganese Compounds:  4 µg/m3, 24-hour average
  • Nickel and Nickel Compounds:  2 µg/m3, 24-hour average
  • Uranium and Uranium Compound (in the PM10 fraction):  1.5 µg/m3, 24-hour average

NOTE: For those companies who are not yet using new models, we have also expressed the new Upper Risk Thresholds in 30 minute intervals.

Further information on these guidelines and O. Reg. 419/05 is available by following the links included in this notice. 

Other amendments to O. Reg. 419/05 include the addition of a definition for toxicity equivalents and how they are calculated for a specific set of dioxin-like compounds in the new Schedule 8 (Dioxins, Furans and Dioxin-like PCBs) and a description of how a metal in a metal compound is calculated for the purpose of assessing compliance with a standard for a metal compound.

Comment(s) Received on the Proposal:   21

Public Consultation on the proposal for this decision was provided for 60 Days, from July 31, 2009 to September 29, 2009.

As a result of public consultation on the proposal, the Ministry received a total of 21 comments: 14 comments were received in writing and 7 were received online.

Additionally, a copy of all comments are available for public viewing by contacting the Contact person listed in this notice.

A selection of these comments are available:

Effect(s) of Consultation on this Decision:

The MOE received a total of 21 submissions from stakeholders on this proposal. Of these submissions, seven were submitted directly to the EBR posting 010-7190 and the remaining comments were submitted to the MOE through other means.

The comments received by the MOE during the 2009 consultation period outlined a number of concerns related to the science and implementation of the air standards. To address these concerns, the MOE set up a multi-stakeholder group, co-chaired by a representative of industry and a representative of an environmental non-government organization (ENGO), with the aim to broaden understanding of air standards and O. Reg. 419/05 and to develop recommendations for the government. The multi-stakeholder group met between January 2010 and March 2011. Through this process, a number of consensus points were identified, which influenced the MOE’s decisions on the air standards. The multi-stakeholder group continues to operate as a forum to address other related Reg. 419/05 issues. 

The MOE also engaged the Canadian Manufacturers and Exporters (CME) through the Government of Ontario’s Open for Business initiative and worked with the CME to address their main concerns related to the air standards and Reg. 419/05. The discussions with CME provided an additional forum to address issues raised by other stakeholders as well.

Changes to Air Standards

Key elements of the decisions that have changed compared to the original July 2009 proposal as a result of the consultations are the following:

  1. Air standards for 1,3-butadiene, benzene, hexavalent chromium, nickel, benzo-a-pyrene (as a surrogate for PAHs) and uranium, have been set directly as annual averages, rather than converting to 24-hour standards as proposed in July 2009. This decision is based on the consensus of the multi-stakeholder group that standards for contaminants causing effects after long-term exposure (e.g., cancer) should be set directly as annual averages rather than converting to a 24-hour standard. All of the above contaminants except uranium were proposed as annual Ambient Air Quality Criteria (AAQCs). The annual AAQC will be used directly as the annual air standard. Uranium was originally proposed as a 24-hour AAQC. However, since the basis of the uranium air standard is kidney effects modelled over a 50 year period, the MOE agreed with stakeholder comments that this more appropriately reflected an effect after a long-term exposure and, therefore, the standard should be set as an annual average.

  2. Air standards for chromium, manganese and nickel have been set as total suspended particulate (TSP) instead of inhalable (PM10) particulate and TSP, as proposed in July 2009. The MOE has agreed with stakeholders that challenges in measuring different metal particulate size fractions in the emissions or the lack of availability of size-specific emission factors warrant a single regulatory limit based on TSP alone. The MOE AAQCs based on PM10 particulate and TSP and these remain unchanged.

  3. Air standards for uranium have been set as inhalable particulate (less than 10 micrometres in diameter) instead of inhalable particulate and TSP, as proposed in July 2009. The MOE AAQCs are based on both inhalable particulate and TSP.

These annual standards take effect July 1, 2016, and the MOE is proposing to introduce screening values in order to support implementation. Screening values will be used to trigger assessment of short-term periods of elevated exposure that may occur within the annual averaging period. Guidance materials on the implementation of annual standards and screening values are under development, along with other implementation guidance materials, based on recommendations made through the course of consultations with industry and the multi-stakeholder group (includes representatives of some First Nations, industry, Public Health units, and ENGOs).

The following is a summary describing the predominant general issues/comments and MOE responses dealing with the new and/or updated air standards for the eight contaminants listed above that were raised by stakeholders during the 2009 comment period.

Comment: Averaging Time

The MOE’s practice of the use of averaging time is toxicologically inappropriate and inconsistent. That is, chronic toxicological effects – both cancer and non-cancer – should have assigned chronic (annual) averaging times. If short-term standards are necessary, they should be based on acute and not chronic toxicological effects.


The new/updated air standards being implemented are intended to protect from development of chronic effects. Some of these effects are observed after a short-term exposure and others are only observed after a long-term or lifetime exposure. By convention, the MOE has set air standards for all contaminants based on a 24-hour timeframe, regardless of the averaging time established for the ambient air quality criterion (AAQC) on which the standard is based. Based on discussions and consensus of the multi-stakeholder group, the MOE has decided that air standards for 1,3-butadiene, benzene, hexavalent chromium, nickel, benzo-a-pyrene (as a marker for PAHs) and uranium, will be set directly as annual averages, rather than converting to 24-hour standards as proposed in July 2009. These contaminants cause effects after long-term exposure (e.g., cancer). All of the above contaminants except uranium were proposed as annual AAQCs. The annual AAQC value will be used directly as the annual air standard. Uranium was proposed as a 24-hour AAQC. However, since the basis of the uranium air standard is kidney effects modelled over a 50 year period, stakeholders agreed that this more appropriately reflected an effect after a long-term exposure and, therefore, should be set as an annual average.

The MOE has decided to set air standards for chromium (0,II,III), dioxins, furans and dioxin-like PCBs, and manganese based on a 24-hour averaging period according to its current practices and implementation requirements for non-carcinogens. This averaging time was proposed in 2009 and is intended to protect against chronic effects caused after a short-term exposure.

Comment: Background Levels

Some new or updated standards are being set at or below ambient background levels. Establishing such standards may leave emitters potentially open to legal action by third parties if the standards cannot be met, especially given that background monitoring may be difficult. Thus, there needs to be accountability of ambient background from both natural and anthropogenic sources.


Ontario’s air standards are derived based on effects data and apply to the whole province. Therefore, they are not adjusted for “background” levels, which may vary depending on location. However, when facilities model the dispersion of their emissions in order to demonstrate compliance with the air standard, they assess only their contribution to the air, rather than their contribution in addition to the background concentration. Where possible, measurements of a contaminant in air around a facility are also adjusted for background before assessment against the air standard.

Comment: Cumulative Effects and Approvals

O. Reg. 419/05 and the Certificate of Approval (C of A) process should consider multiple sources of the same pollutant as well as multiple pollutants being emitted into the same airshed. This should include consideration of cumulative effects (eg. additive, synergistic, antagonistic, persistent and bioaccumulative) on the potential health outcome, as well as multi-media exposure assessments.


O. Reg 419/05 is one of several tools the MOE uses to address air releases of contaminants into the environment. The focus of the regulation is on protecting the air quality around a single industrial facility and complements other tools under the Environmental Protection Act and the Toxics Reduction Act that address releases to other media as well as the use and creation of toxics. The federal government is working with the provinces and territories to develop a new national approach to managing air quality called the Air Quality Management System (AQMS). Air Zone Management (AZM) is a place-based approach that would provide a framework for communities to be involved in actions to help manage air quality issues of concern at the local level. AZM may provide a means to address cumulative effects of emissions on air quality over the long-term, and the MOE is exploring this possibility. 

Comments: Phase-in Timelines for Standards and URTs

The MOE is urged to consider a timeframe shorter than 5 years for implementation of the new or updated air standards, to hasten the decrease in public exposure to the contaminants afforded by the new or updated standards.

In situations when a new/updated URT for a new or updated standard is more stringent than the existing standard, the existing standard should remain until the phase-in period has passed.

Longer phase-in periods for new or updated standards and a five-year phase-in period for the associated URTs is being urged, to allow a facility time to achieve compliance with the air standards under O. Reg. 419/05.


MOE originally consulted on phase-in periods in 2004/05. MOE typically phases in new or updated air standards over a five year period, unless there are concerns that warrant consideration of different phase-in periods (e.g. in the case of the lead standard, the phase in period was three years). A five-year phase-in period is considered a reasonable time to allow facilities affected by a new or updated air standard to assess whether or not further actions would be required to meet the new or updated air standard, or to submit a request for a site-specific standard. If the issue is sector-wide, the technical standard compliance option is also now available to address issues common to one sector or to more than one sector.

During the phase-in period, risks are managed through the use of an Upper Risk Threshold (URT). URTs are not standards but trigger notification and further assessment. This approach ensures that facilities are taking action when required to reduce risks while recognizing that some measures will take time to implement. The URT is not a standard. It comes into effect as soon as the regulation is promulgated, and under O. Reg. 419/05, an exceedence of a URT requires immediate notification of the MOE, which triggers a further assessment of concentrations at specific receptors.

Comment: Basis for URT

There appears to be no scientific rationale behind the MOE’s seemingly arbitrary derivation of Upper Risk Thresholds (URTs). It is suggested that, where possible, URTs should be chemical-specific, based on toxicological evidence and a detailed justification. Formal numerical URT limits should be prescribed under O.Reg. 419/05 for all new / updated standards. Additionally, the MOE has not followed its own process in the setting of a URT for benzene and 1,3-butadiene.


The URT is a risk management value based on consideration of scientific information. It provides an upper boundary for risk to be managed while facilities work towards emissions reductions either within the phase-in period of the air standard (i.e., before the standard takes effect) or after phase-in of the standard (i.e., when a facility is using best available technology under the site-specific standards process). URTs do not replace air standards but allow industry time to implement necessary action to reduce risks in local communities. Exceedences of the URTs trigger notification and further assessment.

The framework for establishing, implementing and assessing URTs was established through consultation with stakeholders including public health associations and industry. Generally, a URT is set as a multiple of a given standard.

In a few situations where there was deviation from the general GIASO-described method of developing a URT, the approach was described in the proposed regulatory amendments posted for public consultations, posted in parallel with the proposed standards. The MOE will consider outlining these alternative methods, when used, in greater scientific detail in future regulatory amendment postings.

Comment: Impacts on Existing Approvals

Introduction of the proposed new or updated standards creates uncertainty and potential delay in the approval of Certificate of Approval (CofA) applications already in the review process. Thus, a phase-in period is recommended for facilities that have a 5-year comprehensive CofA, with the requirement for compliance not taking effect until expiration of existing permits.


Where there is no existing guideline or standard for a contaminant, or where the URT is more stringent than the current guideline or standards for a contaminant, then the URTs can also be used as assessment criteria in the review of ESDM reports during the phase-in period. URTs are not standards. They trigger notification and/or further assessment if exceeded. Some CofA may require a person to assess against the URT value during the phase-in period. If a standard is phased in during the period of a Basic Comprehensive CofA, the holder of the CofA is still required to meet the standard on the phase-in date of the standard.

Comments: Achievability of Air Standards

A number of the new air standards are thought to be unattainable, and will drive emitters to either the Site-specific Standards Process or sector-based Technical Standard (see Technical Standards Publication) to achieve compliance. This in effect creates a two-tier air standard compliance system. There is the concern over the potential public impression of non-compliance and unacceptable health risks resulting from the need to proceed with a site-specific Standard or sector-based Technical Standards application process.

Compliance with the new or updated air standards should be consistent across the province, and industry should not be permitted to apply for a site-specific standard.


Introduction of new or updated air standards can affect facilities or sectors differently. To promote effective implementation, O. Reg. 419/05 gives industry flexibility and solutions for continuous improvement with three ways to comply with the regulation: 1) meet the air standard by the July 1, 2016 phase in date; 2) request a site-specific standard; 3) register under a sector-based Technical Standard (if available). Both site-specific standards and technical standards can also consider economic impacts or cost-effectiveness. All are equally valid compliance options in the regulation and MOE recognizes the need to improve stakeholder communication on this issue.

Air standards allow us to identify facilities or sectors that need to update their technologies and catch up with advances in other jurisdictions.

Recent amendments to the site-specific standards process (see EBR 011-3088) will improve business certainty and provide clarity on this process. In December 2009, the new compliance option of sector-based technical standard was introduced where the emphasis shifts from assessing compliance with POI to assessing compliance against a set of technical and operational requirements designed to better manage and reduce emissions. Technical standards can also reduce regulatory burden while improving environmental protection. Technology standards are similar to Maximum Achievable Control Technology (MACT) Standards which are the primary tool used to regulate air toxics under the US Environmental Protection Agency – Clean Air Act. Site-specific and sector-based technical standards are set based on best available technology. Technical-based standards are designed to reduce risks to people who live near a facility through planning and implementation of measures to reduce emissions and overall exposure over time.

Comments: Risk Basis of Air Standards

The MOE needs to revisit the policy implication associated with the use of 1 in 1,000,000 (10-6) acceptable additional cancer risk level in the derivation of air standards for carcinogens. This practice introduces an unnecessary level of conservatism in the air quality standard, in light of other regulatory agencies’ use of 1 in 100,000 (10-5) or 1 in 10,000 (10-4) risk level.


Each jurisdiction makes policy decisions around risk levels to be used in standards development. In Ontario, provincial standards are set at a goal of one-in-a-million risk for carcinogens. However, facilities may operate above this level during the phase-in of the air standards as well as through the site-specific or technical standards compliance options.

The risk management framework in Ontario is similar to other jurisdictions. For example, Ontario and the US frameworks for controlling air toxics have the same elements, such as health-based limits and technology requirements, but they implement these requirements in different ways. In the US, facilities implement technologies first then assess risks to human health. In Ontario, we use our air standards to assess risks first and then focus only on those facilities that need to update their technologies to reduce those risks as much as possible. Technology reviews are part of the site-specific or technical standards compliance options. By introducing new or updated air standards, we identify those Ontario industries that need to catch up with technology advances in the US and other jurisdictions. Both the US states and Ontario allow risk management and compliance within their regulatory frameworks to meet risk levels above one in a million cancer risk.

Comment: Conversion Factors

There is no basis for converting a standard based on effects observed after a lifetime exposure to a 24-hour standard, as the impact of a single day’s exposure to the mathematical equivalent of an annual exposure cannot be supported based on scientific evidence. The more advanced US EPA air dispersion models (such as AERMOD) is capable of predicting air concentrations over any averaging period – including annual. Thus, a rationale for the necessity for the conversion of an annual standard to set 24-hour exposure standard is requested, as it seems unnecessary.


The MOE agrees that the use of more advanced models allows prediction of air concentrations over any averaging periods and is now moving forward with annual standards for substances causing effects after long-term exposures, rather than converting to 24-hour standards.

Conversion factors are based on empirical monitoring data of a common pollutant, ratios of concentrations observed for short-term and long-term averaging times and, also on meteorological considerations. These factors ensure that if a short-term limit is met at a higher concentration, then longer-term exposures would be maintained at levels protective against the original key health effect (e.g., at levels not exceeding an annual AAQC).

Comments: Particle Size Determination

While there may be science-based reasons for establishing standards for metals in specific size fractions, the MOE had not considered the technical limitations of determining metal emissions in the PM2.5, PM10 and TSP fractions. Specifically, there are no documented source testing methods to measure metals in size fractions at the concentrations necessary to demonstrate compliance with some of the proposed standards. An emitting facility should meet the air standard limits for all particle fractions – that is, both for the PM2.5 size fraction (for manganese), PM10 size fraction AND the TSP size fractions, as outlined in the 2009 Rationale Documents of the metals chromium, manganese, nickel, and uranium.

The emission and deposition of persistent metals into the environment, especially metals found in larger particulates of industrial emissions continues to be of concern.


The MOE has re-considered the particle size approach in setting metal standards. With most metals in the recent group of standards being developed, the critical toxicological endpoints are such that the PM10 fraction (PM2.5 for manganese) represents the most appropriate health-based AAQC. Thus AAQCs will be set based on the PM10 fraction. In the case of manganese where the AAQC is based on the PM2.5 fraction, an additional health protective AAQC in PM10 fraction was also derived because of concerns that adverse neurological effects are also associated with human exposure to manganese (Mn) in particulates ≥ PM2.5.

The MOE agrees that emission and deposition of persistent metals into the environment, especially metals found in larger particulates of industrial emissions continues to be of concern, especially if such emissions are considerable and outweigh PM10-based emissions for certain sources. In addition, while monitoring of metals within various particulate sizes in ambient air is feasible, stakeholders pointed out serious implementation difficulties regarding the availability of PM10 (and PM2.5) size fraction emission factors for various sectors, which would be needed for model-based compliance assessments. For these reasons, it was decided to recommend air standards that are TSP-based. The air standards based on TSP will be used in ESDM reports for the assessment of compliance with O. Reg. 419/05. However, AAQCs are not used in ESDM reports. AAQCs are published in a separate document and are used for special studies, air quality assessments, etc.

Comment: Particle Size Composition

The assumption used by the MOE that the composition of all particulate matter is equal, can introduce unacceptable margin of conservatism (i.e., extrapolation from TSP to PM10 and PM2.5). Considerable ambient monitoring data in the vicinity of various industrial operations would allow the use of appropriate conversion factors for metal fractionation based on size. Such site-specific factors should be used for the purpose of determining compliance.


The translation of AAQCs based on fine particulate size fractions to total suspended particulate (TSP)-based standards is based on measured ratios of PM10 to TSP or PM2.5 to TSP levels in ambient air as reported by Health Canada and referenced in several of the Decision Documents. Accordingly, approximately 50% of ambient PM10 consists of fine particles (PM2.5), and similarly on average 50% of ambient TSP consists of the PM10 fraction. This broadly observed trend has been based on several years of PM2.5, PM10 and TSP data acquired under the National Air Pollution Surveillance (NAPS) network. Hence, the PM10 values were multiplied by a factor of two to set the air standard. Since the MOE sets province-wide standards facility-specific monitoring considerations would not be appropriate.

Comment: Layers of Conservatism

The MOE needs to revisit the layers of conservatism in the standard development process. The new air standards are in general set significantly lower than justified for health protection. Uncertainties at several steps in the air standard setting process (e.g., utilizing studies with imprecise occupational exposure data) suggest that a health-protective standard could span a range of values, and it should be recognized that higher values are also health-protective.


The AAQCs and subsequent derived air standards are set to at levels protective of environment and health. This process entails significant deliberation and scientific discussions to ensure the limits in place also protect the more vulnerable members of the population. Consequently, uncertainty factors are often applied. From this perspective, a more conservative approach is taken to protect the more vulnerable population, given that in a large number of cases, thresholds are derived from studies using healthy, adult populations. Hence it cannot be said that this represents an over-conservative approach, as normal human population consists of individuals with an array of predispositions and susceptibilities. Furthermore, it can be argued that members of a human population are not exposed to a single chemical entity, but rather to a very complex mixture of air-borne contaminants. Standards and guidelines developed by the MOE are contaminant-specific and hence do not explicitly address potential interactions among contaminants.

Comment: Compliance Assessment - Modelling

Compliance with O. Reg. 419/05 relies completely on a modelling-based system that is not accurate in its ability to measure or predict an individual’s exposure to a given contaminant, and was not designed for compliance and enforcement. Use of maximum emission modelling to measure compliance is a conservative approach against already conservatively-established standards and arbitrary URTs.


The MOE uses both modelling and combination of modelling/monitoring to determine compliance with air standards under O. Reg. 419/05. Additionally, through discussions with the multi-stakeholder group, the MOE is developing enhanced guidance for compliance assessment and has introduced annual standards, which reduce the conservatism.

Comment: Competitiveness and Investment

Compliance with the air standards represents a roadblock to investment in Ontario and the MOE is asked to consider the effects of its decisions consistent with sustainable development principles.


To alleviate economic and technical challenges, O. Reg. 419/05 provides three options for compliance including: meeting the air standard by the specified phase-in date (July 1, 2016 for these new/updated standards); requesting a site-specific standard; registering under a technical standard, if available. These compliance options in O. Reg. 419/05 allows industry to manage the timing and costs of compliance in-line with their planning cycles while ensuring continuous improvements to reduce risks. In response to these concerns, the MOE has amended the regulation regarding the site-specific standards process to improve business certainty and facilitate long term investment decisions. For more information, please see EBR #010-3088.

Comment: Documentation of Air Standards Process

There is a need for an air standard-setting guidance document, which would clearly outline MOE’s policy with regard to use of the following:

  • how the issue of cumulative effects is being considered
  • how background ambient air concentrations are being considered
  • the rationale for the use of the “precautionary principle” in the standard-setting process
  • science-based detailed rationale for establishing URTs for carcinogenic and non-carcinogenic contaminants
  • process for derivation of air standards for carcinogenic and non-carcinogenic contaminants
  • the rationale for the choice of an appropriate risk level for carcinogenic contaminants
  • a rationale for the extrapolation of effects associated with chronic exposure in the development of a 24-hour standard


The MOE agrees that a document describing the development of our air standards would enhance understanding by our stakeholders and assist them in responding to MOE proposals for new/updated air standards. To that end, the MOE has initiated a review of its communication and guidance material with the aim to better describe the overall process and to document key considerations in a publicly available reference document.


Gail Brown
Stakeholder Relations Officer
Ministry of the Environment
Environmental Sciences and Standards Division
Standards Development Branch
Issues Management and Project Coordination
40 St.Clair Avenue West
Toronto Ontario
M4V 1M2
Phone: (416) 327-5772

Additional Information:

The following government offices have additional information regarding this Decision. To arrange a viewing of these documents please call the Ministry Contact or the Office listed below.

Standards Development Branch
40 St. Clair Avenue West
Floor 7
Toronto Ontario
M4V 1M2
Phone: (416) 327-5519

The documents linked below are provided for information purposes only
All links will open in a new window

1. Regulation Decision Notice for Benzene
2. Regulation Decision Notice for
3. Regulation Decision Notice for Hexavale
nt Chromium Compounds, and Chromium and
Chromium Compounds (Metaliic, Divalent a
nd Trivalent)
4. Regulation Decision Notice for Dioxins,
Furans and Dioxin-like PCBs
5. Regulation Decision Notice for Manganese
and Manganese Compounds
6. Regulation Decision Notice for Nickel
and Nickel
7. Regulation Decision Notice for Benzo[a]
pyrene (B[a]P) (as a surrogate of tot
al PAHs)
8. Regulation Decision Notice for Uranium
and Uranium
9. MOE web page for Air Pollution – Local A
ir Quality
10. MOE web page for AAQCs, standards and gu
11. Regulation Decision Notice for Amendment
s to the Altered Standards process for a
ir standards set out in Ontario Regulati
on 419/05
12. Amended O.Reg. 419/05 (will be
available shortly)