Non-ProZ.com Jun 23, 2004:

voici plus de contexte ;) Comments Specific to n-Hexane (from the two proposal postings): Comment: A POI limit of 5000 ug/^m3 was suggested during the first ER proposal posting to be an acceptable revised level for n-hexane and could be considered either as a final standard or as an interim standard. During the second ER proposal posting, concerns were raised that were related to the reviewed dispersion models proposed by the Ministry. It was pointed out that the use of the US EPA dispersion models may result in a 3-fold increase in estimated POI concentrations as compared with those predicted with the use of the current O. Reg 346 dispersion models. Additional time may be required for process optimization if the proposed models were used. Response: The proposed new air dispersion models allow for the effects of a contaminant to be assessed using modelled exposure concentrations over the most appropriate averaging time for that contaminant (e.g. 24-hour average standard for chronic effects) rather than being limited to using the maximum 2 hour emission scenario required by the existing O. Reg. 346 models. This type of approach may assist in determining the significance of short-term impacts from start-up and shut-down operations. The proposed introduction of effects-based standards with appropriate averaging times to assess environmental impacts is currently out for consultation in the an �Air Dispersion Modelling Guideline for Ontario� (ADMGO) and a position paper entitled: �Updating Ontario's Regulatory Framework for Local Air Quality�, which outlines proposed regulatory amendments. Comment: Concerns have been raised in respect to the scientific basis of the proposed standard, risk management issues and the averaging times. The scientific basis and the revised chronic inhalation Reference Level (REL) of 7000 ug/m3 from the State of California should be incorporated into the supporting Rationale document and considered for air standards development for n-hexane. Selection of safety factors for the air standards development for n-hexane should be included in the risk management process for the implementation of the revised standard. The Ministry should consider the RfC-derived air standard for n-hexane with an annual averaging time, instead of the proposed 24-hour averaging time. Response: The California's chronic inhalation REL has been incorporated into the supporting rationale document for n-hexane. The basis of the REL supports the Ministry's analysis that the specific neurotoxic effects are unique to n-hexane. The key animal study for the REL and the increasing evidence of the neurotoxic effects may occur at low concentrations, as mentioned in the supporting rationale document, further support the Ministry's decision on the proposed air standards for n-hexane. The rationale for the application of uncertainty factors has been provided in the supporting rationale document. Uncertainty factors related to implementation issues may be dealt under the proposed new risk-based decision making process. Averaging time issues are responded under the General Comments of this posting notice. Comments: Concerns have been raised with the revised air standards on the oilseed processing industry in Ontario as well as on a national scale. The following items have been suggested: the potential economic impacts should be studied in the decision making process; there was no appropriate substitute solvent, on a commercial scale can be used; there is a need for sector-specific risk management process to respond to implementation issues for this sector; the 24-hour averaging time for the revised air standard was not appropriate and the proposal to develop a short-term criterion for n-hexane was suggested for the Ministry. Response: The Ministry has will continue to work with stakeholders in the oilseed processing sector on implementation issues through proposed risk-based decision making process outlined in the �Guideline for the Implementation of Air Standards in Ontario� (see ER posting). The feasibility of the development of short-term criteria for n-hexane may be studied through the Ministry's air standards setting process. Averaging time issues are responded under the General Comments of this posting notice. The Ministry appreciates the efforts of the oilseed process industry in the contribution of valuable scientific input in the air standards development for n-hexane. Comment: Two comments from oilseed processing facilities raised economic and technology issues associated with the proposed air standard, such as plant modifications and solvent uses. Response: Technology limitations, timing and economic issues are all discussed in the proposed �Guideline for the Implementation of Air Standards in Ontario� (see ER posting) and associated regulatory amendments. Comments of a General Nature: Four submissions included general comments applicable to any of the proposed air standards. The comments are summarized below with the Ministry's response. Comment: The proposed standards are not based on the latest scientific information. Response: The Ministry considers the most credible science when revising existing air standards or developing new air standards. During the Information Draft stage of the air standard setting process, stakeholders are encouraged to provide any additional scientific information that they feel the Ministry should consider when developing or revising air standards. In some instances, new and credible scientific information is published following the posting to the EBR of the Rationale Document. In these instances, the Ministry is careful to review the new information before making a decision on the proposed air standard. The Ministry did alter the original proposal based on input we received from stakeholders.