Proposed Revisions to Odour-based Ambient Air Quality Criteria and Development of an Odour Policy Framework

Transcription

1 Proposed Revisions to Odour-based Ambient Air Quality Criteria and Development of an Odour Policy Framework Position Paper This proposal is to consider revisions to odour based Ambient Air Quality Criteria (AAQC) limits and the development of an Odour Policy Framework in the future. Ontario Ministry of the Environment

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3 Proposed Odour Policy Framework Proposal 1.0 INTRODUCTION In June 2004, the Ministry of the Environment posted on the Environmental Bill of Rights a number of postings, for a 120 day comment period, which dealt with improving Ontario s Air Quality. These documents included: a Position Paper, titled Updating Ontario's Regulatory Framework for Local Air Quality ; Air Dispersion Modelling Guideline for Ontario ; Guideline for the Implementation of Air Standards in Ontario (GIASO) ; and Proposals for new/updated Air Standards. The ministry proposed amendments to Ontario Regulation 346, made under the Environmental Protection Act, to introduce new air standards; update air dispersion models; provide a risk-based decision making process to address implementation issues and improve upon its clarity and enforceability. Stakeholder comments on the proposal package highlighted the need for ministry to engage in a broader discussion regarding the assessment and resolution of odour impacts. In response to this feedback the ministry plans to develop in the future an Odour Policy Framework based on the latest scientific knowledge and approaches available. Input from industry, consultants, academia and other stakeholders will be requested by the ministry as it proceeds with this initiative. In addition, the development of odour-based guidelines/standards evolved over the last three decades and is still open to improvement. The Ministry therefore considers it timely to outline an improved basis for setting odour-based guidelines/ standards, with the intent of upgrading the current odour-based standards in the future. This position paper, being posted for consultation, outlines the proposed path to revising odour-based limits in Ontario. It also forms a part of a new odour policy framework, which is also considered to be undertaken in the future in response to the recent consultation. Ministry of the Environment Page 1

4 Proposed Odour Policy Framework Proposal 2.0 DEVELOPMENT OF A FUTURE ODOUR POLICY FRAMEWORK FOR ONTARIO The Ministry proposes to develop a framework which will reconcile the existing and proposed Ambient Air Quality Criteria (AAQC) for odour, allow for the use of predictive odour impacts and direct measurements and be able to deal with the existing situation when odour become an issue in order to: help industry plan under the Section 9 Application process; evaluate control options under an abatement plan to deal with adverse effect; and assist the ministry in dealing with odour complaints. It is anticipated that the ministry will continue to set odour based AAQCs for substances with low odour thresholds such as sulphur based compounds. However, for other less odorous substances, or mixtures of substances the framework must set limits for indications of possible odour impacts and provide new tools to assess these impacts. The framework will be developed using the state-of-art-knowledge on odour and link with other Canadian and international jurisdictions that have or are currently updating their approach to regulating odour. The framework will consist of the components outlined in the following Table 1. Ministry of the Environment Page 2

5 Table 1: Components of Proposed Odour Policy Framework Component Applicability and Implementation Receptor Objective Limits for Odour Expected Framework Develop guidance on applicability and implementation of the framework at facilities with known odour related issues, or are likely sources of odour based on equipment, process or products produced at the facility i.e. rendering operations. Specifically exclude sources from the framework that are not expected to be a significant source of odour i.e. welding operations in an industrial area. Develop the concept of an odour sensitive receptor that links to adverse effect and is distinct from the predicted maximum concentration outside the fence line. Establish limits for the intensity or offensiveness of the odour, based on a combination of: Odour-Based AAQCs predictive odour impacts using emission rates of specific contaminants applied to dispersion modelling and comparing the modelled results to contaminant specific Odour-Based AAQCs; Methods Considerations for Meeting Objective Limits for Odour Reporting Compliance with Objective Limits Olfactometric Based Criteria (Odour Units analyzed by an odour panel) predictive odour impacts using emission rates of specific contaminants applied to dispersion modelling and comparing the modelled results to an appropriate olfactometric based criteria based on odour units; directly measured impacts through field monitoring using olfactometric techniques with the measured results compared to an appropriate olfactometric criteria based on odour units; Document methods for odour dispersion modelling, stack and field olfactometric techniques to assess odour impacts, field sampling techniques and laboratory analysis of sampled odorous emissions. Develop a method to determine compliance with the Objective Odour Limits based on the averaging time for the limit, frequency of exceedance and the duration of exposure. Explain how the AAQCs, predicted olfactometric impacts and field measurements are related and how compliance with the framework can be demonstrated based on the selected approach. This Table consists of two columns. The first column contains each of the proposed components of the framework, and the second column contains the corresponding details of the proposed framework. Ministry of the Environment Page 3

6 3.0 BACKGROUND ON ODOUR-BASED LIMITS Part of the proposed odour policy framework includes a review of odour based limits. MOE is proposing to update Regulation 346 to reflect the consultation on air standards and/or guidelines conducted as part of the MOE Standards Plan. MOE also proposes to promote the implementation of effects-based air standards. For most people the impact of odour usually falls into one of three broad categories: no-detect/no-complaint, offensive/nuisance/complaint, and definite health effects. Nearly all of the odour-based standards and guidelines were established in the period , when there was a lack of peer-reviewed Odour Detection Threshold (ODT) studies available. Industrial growth often created odour problems that were handled by relying on poorly determined (yet still the best available) odour detection thresholds for various chemicals. During this period and up to the early 1990s, the averaging period for setting odourbased Ambient Air Quality Criteria also evolved from 24 hour, through 1 hour and eventually to 10 minutes. This was in response to the Ministry gaining a better understanding of the odour complaint characteristics of people in odour-affected communities. Thirty years later, consistent with the effort on other effects-based standards, there is a need to review and update the odour-based limits in Regulation 346. Although well conducted odour threshold studies are few in number, there is at least one good quality experimental study (ORTECH) and one well regarded review paper (AIHA) in the last 12 to 15 years that can be used to improve the MOE s odour-based limits in the revised Regulation 346. The averaging period (duration) to which the odour-based limit should apply is also in need of review and possible adjustment. One of the main concerns is the issue of how long a reasonable person would endure an offensive odour before complaining. In the Ministry s collective experience, odour complaint characteristics from odour-affected communities pointed to short times, approximately 10 minutes, after which people would complain. Such short times are also reflected in the short averaging times used by Connecticut (15-minutes, nuisance), some of the Australian States (Victoria, 3-min.; New South Wales, second) and Denmark (1-minute), with various limits on the frequency and intensity (or strength) of the odour episodes. Ministry of the Environment Page 4

7 4.0 PROPOSED APPROACH TO ODOUR BASED AAQCs 4.1 Identify High Quality Odour Studies The MOE is collecting the best available odour detection thresholds from the review document produced by the American Industrial Hygiene Association (AIHA, 1989). There are several forms of the odour threshold for a substance. The odour threshold most commonly determined and reported on is the odour detection threshold, which is usually taken as the concentration (in air, micrograms per cubic metre) at which 50% of the odour panel can say they perceive (detect) the odour. Recognition thresholds and complaint thresholds are typically 3 to 5 times the detection threshold for any specific substance. The AIHA review reported the detection and recognition thresholds from studies involving 182 odorous chemicals which also had Threshold Limit Values (TLVs). They evaluated the results according to several criteria relating to study quality and acceptability, and then categorized the odour threshold values as accepted or rejected. The MOE is also reviewing the data provided by the ORTECH International study (1991) in which odour concentration percentage response curves were determined for detection, complaint and annoyance levels for 87 chemicals. The ORTECH study met the AIHA acceptability criteria. In addition to the 50% ODT values, where the data is available it may also be possible to determine a complaint level (i.e. 5 to 25 %) or the degree of annoyance, for example. 4.2 OPTIONS FOR DEVELOPING ODOUR-BASED AAQCs The Ministry is seeking input on the following two options for developing odour-based limits in the future Option 1 Use the combined data from both the AIHA and ORTECH studies to determine the best ODT (50%) for each chemical. The preferred approach is to determine the geometric mean of all of the accepted values. The new geometric mean ODT would then be considered for use as the short term odour-based Ambient Air Quality Criterion. Ministry of the Environment Page 5

8 4.2.2 Option 2 Use the detailed information from the ORTECH odour-response curves to determine an alternative benchmark level for each chemical, such as the 10% complaint level. An odour limit based on a percentage of complaints from the general population may be a more acceptable basis for some of the odourous chemicals, especially those for which health effects may not be a concern at the ODT levels. In particular, the exact steps, briefly, would be: determine the odour ratio (10% complaint level / 50% detection level) for each chemical from the ORTECH curves; multiply the odour ratio by the ODT (50%) for each chemical determined as per Option 1, thereby relying on acceptable ODT (50%) from both the ORTECH and the AIHA datasets; use the result as a weighted 10% complaint benchmark which could serve as the short term odour-based Ambient Air Quality Criterion. If this option were chosen, what is the most effective complaint level to use (i.e. in the range of 5% - 25%)? 4.3 Advantages/Disadvantages Option 1 is the simplest to do and uses the best available odour detection thresholds to set the limit where typically 50% of the general population would detect the odour, but there is no consideration to the quality or character of the odour. Although some people consider odour to be a nuisance issue and not a health issue, health scientists generally agree that odours can cause real health effects such as headaches and nausea. To achieve more general acceptance the odour limits should be developed to protect against offensive odours which are more likely to be seen as causing adverse effects. The use of Option 2 would favour a lowering of the limits (vs. Option 1) for the more offensive odours (complaints more probable) and a raising of the limits for the less offensive odours. Other jurisdictions are basing their odour policies on several factors but offensiveness is a common concern. For the 23 substances having odour-based criteria in Regulation 346, the odour ratio (10% / 50%) ranges from 0.33 for the most offensive odour to 1.50 for the least offensive. Note that the 50% ODT is equal to one odour unit (1 OU). Ministry of the Environment Page 6

9 5.0 NEED FOR NEW HEALTH-BASED AAQCs Any substance can have multiple effects which occur at different concentrations. As noted in section 3.0, many of the odour-based standards and guidelines are based on the limited odour studies available in the 1970s. In each case the odour-based limit was considered to be protective against adverse health effects as well. One of the possible outcomes when reviewing these odour-based standards may be the raising of some of these limits. The implication of this is that a new odour-based limit may be above the level where a health-based limit would be appropriate. If a protective health-based limit is not immediately available there would need to be a phase-in period for the new odour-based limit until an appropriate limit based on health is established. 6.0 CONTINUING NEED FOR ODOUR-BASED LIMITS Odour-based limits can be used either in the design phase of an industrial process/facility when potential odour problems are most easily prevented, or they can be used in the operational phase when odour complaints are being registered from the surrounding community and the issues of non-compliance and appropriate action are being considered. 6.1 Mixtures Olfactometric Based Criteria (Odour Units analyzed by an odour panel) The majority of odour problems will result from the presence of more than one substance in the air, i.e. the odour is due to a mixture of chemicals. The presence of one chemical may mask (hide) the odour from another chemical, or the odourous effects from two or more chemicals may be additive. For this reason the most effective way to assess odour impacts when mixtures are likely responsible and individual chemicals can not be recognized is through the use olfactometric analysis. This technique involves using odour panels to assess the odour intensity of a sample measured in odour units (OU) in an odour sample collected from a source of odour. Briefly, the number of OUs for each sample is the number of equal volumes of odourfree air needed to dilute the sample down to a level of 1 OU (as determined by an odour panel). The odour panel analysis can be used to determine an emission rate that is applied to dispersion modelling to predict an impact at a receptor. That impact can then be compared to an objective criteria based on odour units. Ministry of the Environment Page 7

10 6.1.2 Hazard Index Formula An alternative approach to mixtures that may work in those cases where the component chemical concentrations C1, C2, C3, etc., can be specified (either by measurement or estimation) is to use a Hazard Index (HI) formula. The use of this approach (in the design phase or the assessment phase) would be essentially the following: C 1 /Odour Limit 1 + C 2 /Odour Limit 2 + C 3 /Odour Limit 3 +.= HI OU where the ratio of each component s concentration to its (respective) odour limit is summed up to give a Hazard Index for the mixture of chemicals. The HI is then compared to the appropriate OU limit for that location/facility. The result is not a confirmation of compliance or non-compliance, but it can help the facility owners/designers to avoid potentially odourous mixtures. 6.2 Single Chemical For some existing facilities the odour problems may be primarily due to a single chemical. In those cases an ambient air sample in the impacted area can be analyzed to determine the concentration in air of that chemical in terms of micrograms per cubic metre. That concentration would be compared to the short term odour-based AAQC to help assess the severity of the problem. For an existing source or for the design phase of a new source, the predicted odour impact at the facility boundary may be modelled from the estimated emissions either in terms of micrograms per cubic metre or in terms of odour units per cubic metre. If the odour impact was due to only a single chemical then the predicted impact is likely to be reasonably accurate due to the absence of masking or additive effects. 7.0 CONSIDERATIONS FOR MEETING OBJECTIVE LIMITS For any objective odour limit some consideration should be given to the various factors that can influence odour impact. As discussed above the averaging period (duration) to which the odour-based limit should apply is also in need of review and possible adjustment. One of the main concerns is the issue of how long a reasonable person should be willing to endure an offensive odour before complaining. Whether an odour has an objectionable or offensive effect will depend on the frequency (F), intensity (I), duration (D), offensiveness, or character (O), and location (L) of the odour event. Different combinations of these factors can result in adverse effects being reported in the community. Some discussion on two of the factors may be helpful. Ministry of the Environment Page 8

11 7.1 Offensiveness (Character) Each of the five FIDOL factors noted above can be the determining factor in whether an odour has an adverse effect, but only four of the factors can be measured and (perhaps) compared with guidelines or limits on their presence. As the Ministry consults on and develops an effective approach for handling potential and existing odour issues in Ontario, it is likely that limits for those four FIDOL factors (F,I,D,L) will be established. The last factor, offensiveness (or character, or intrinsic nature) of the odour, is also referred to as the hedonic tone and can only be assessed in descriptive terms (such as oily, sewage, garlic, rotten eggs, bakery, etc.). An odour that is very offensive to some people may be of no real concern to others. Some odours will be offensive to the large majority of people because of the nature of the odourous activity (sewage treatment, crematorium, abattoir, etc.). Those odours may cause a large number of complaints even at the barely detectable (or even non-detect) level. A condition that is adopted in some other jurisdictions is that the odour must be objectionable or offensive in the opinion of an ordinary reasonable person. 7.2 Duration (Averaging Time) The duration of each odour episode may be very brief (seconds) or may extend up to many minutes, or even several hours if weather conditions and emission conditions (from the odour source) combine in the right way. One of the key questions to consider is how long a reasonable person should be willing to tolerate an offensive odour. As expected the tolerable duration will be strongly influenced by the other FIDOL factors such as the frequency of occurrence, or the intensity (strength) or character of the odour. The number of complaints will also depend on the location of the odour source and the number of potential impacted recipients who are living or working nearby. Several years ago an informal survey of public opinion carried out by Ministry environmental officers indicated that an odour episode duration of 10 minutes would be long enough to cause someone to register a complaint. When investigating an odour complaint situation it is also accepted procedure in some jurisdictions to collect an ambient air sample in the impacted area for a period of 5 to 10 minutes. Peak values can occur within an odourous plume for a few seconds on each occasion, but an environmental investigator will get a more reliable assessment of the odour problem by walking through the plume every 10 minutes or so. Investigators in other jurisdictions are also instructed that when an odour is intense, 30-minute observations may not be required to determine that an adverse effect is occurring. Ministry of the Environment Page 9

12 8.0 PROPOSED PATH FORWARD FOR ODOUR-BASED LIMITS 8.1 Proposed Revisions to Odour-based AAQC Limits in Ontario After comments are received on the Proposed Approach to Odour-Based AAQCs in this position paper, including the two options for developing odour-based limits, the new approach would be applied to both the current and the new odour-based Ambient Air Quality Criteria as they are revised. These would be updated and, if necessary for some substances, health based limits (as needed) would also be developed (i.e., as noted in section 5) as part of the plan to update standards. 8.2 Development of an Odour Policy Framework As discussed, it is anticipated that the ministry will continue to set Odour-Based AAQCs for substances with low odour thresholds such as sulphur based compounds. However, for other less odorous substances, or mixtures of substances the framework could set limits for indications of possible odour impacts and provide new tools to assess these impacts. Odour-Based AAQCs alone may not therefore be sufficient to deal with these issues. As discussed above an odour policy needs to be developed to incorporate Odour-Based AAQCs along with other techniques for assessing odour impacts such as Olfactometric Based Criteria (Odour Units) employed with predictive odour impacts using modelling or even directly measured impacts. These techniques together with Odour-Based AAQCs would be able to deal with the situations when odour become an issue such as: Application under the Section 9 process for odourous facilities; The evaluate control options under an abatement plan to deal with existing adverse effects; and Situations where the ministry is dealing with odour complaints. 9.0 REFERENCES 1. [ORTECH]. G.Z. Nagy. Journal of Air & Waste Management Association, (1991). Vol. 41, No.10, p [AIHA]. American Industrial Hygiene Association (1989). Odour Thresholds for Chemicals with Established Occupational Health Standards. Ministry of the Environment Page 1