Most Popular Links
- All RELs
- Environmental Tobacco Smoke (ETS)
- East Bay Kids Web
- Hot Spots
- Criteria Air Pollutants
- Diesel Exhaust
- Criteria Air Pollutants
- Diesel Exhaust
- Environmental Tobacco Smoke
- Hot Spots Guidelines: Technical Support Documents
- Exposure Assessment and Stochastic
- Risk Assessment Methodology
- MTBE and Ethanol
- Toxic Air Contaminants
- Wildfire Smoke: A Guide for Public Health Officials
- Air Pollution and Children's Health
- Toxicity Criteria Database
- Outside Air Links
resources for kids and educators
- Disney's Planet Challenge
- Education Links
- Guidelines for Safe Use of Art and Craft Materials
- Green California Schools Summit
- Lawrence Hall of Science
- Sally Ride Science Festivals
Air Toxicology and Epidemiology
States Petroleum Association
Up | Down
The following comments address preliminary concerns with the draft guidelines, relative to the legislative intent of AB 2588 and SB 1731:
Comment: OEHHA should expedite development of the revised guidelines. SB 1731 took effect on January 1, 1993. It is still not clear when the revised guidelines will be available for industry application. In the interim, facilities remain subject to the overly conservative and scientifically outmoded CAPCOA Guidelines. Despite the urgent need for the guidelines, it is imperative that OEHHA acknowledge the legislative intent of SB 1731, apply the best available science and incorporate full public and peer review into the guideline development process.
Response: At the time the comment was made, OEHHA had been working on the Air Toxics Hot Spots Risk Assessment Guidelines for over 2 years. OEHHA acknowledges the legislative intent of SB 1731, to write risk assessment guidelines that allow for supplemental information and include a "likelihood of risks" approach, and continues to apply the best available science. There is extensive peer and public review of documents associated with the guidelines development and the ARBs Scientific Review Panel is also reviewing all documentation for the guidelines. OEHHA has been working simultaneously on the exposure assessment and stochastic analysis, chronic noncancer, and cancer potency portions of the document, all parts of the SB 1731-mandated risk assessment guidelines.
Comment: Each set of supplemental guidelines should be considered individually and collectively to assure compliance with the legislative intent of SB 1731 (e.g., reducing uncertainty and compounded conservatism and use of best available science).
OEHHA should assure that the opportunity is provided for public review of the final risk assessment process once all of the revised guidelines have been issued, and prior to approving any of the individual guidelines, or finalizing the integrated process for conducting health risk assessments under the revised AB 2588 program. In evaluating the cumulative impact of the guidelines, it will be essential for reviewers to consider the interaction between the various component guidelines (acute, chronic non-carcinogen, carcinogen, and exposure assessment). To achieve this review, OEHHA should incorporate an additional, extended public review period for the completed revised risk assessment process before any action is taken to finalize and/or approve any of the component guideline documents.
Response: Public and Scientific Review Panel (SRP) review of all the components of the guidelines is taking place. The final risk assessment guidelines will contain information from each of the Technical Support Documents, and will also undergo public and SRP review. In the end, the entire set of documents will have undergone public and peer review.
Comment: OEHHA should not direct limited resources toward developing new health values where USEPA values or other ARARs already exist.
OEHHA should focus their limited resources on developing appropriate supplemental risk assessment guidance for the areas explicitly addressed in SB 1731 (e.g., uncertainty analysis, exposure assessment). Development of exposure limits for assessing health risks for acute, chronic non-carcinogen, or carcinogen exposures should be deferred to U.S. EPA for application within specific state programs.
Response: The U.S.EPA has a limited number of cancer potency factors and chronic noncancer reference concentrations which we can use. To date, USEPA has not developed any acute reference concentrations for routine or planned releases. OEHHA has filled this void by developing acute Reference Exposure Levels for one-hour exposures.
As stated in the statute (Health and Safety Code Section 44306), "health risk assessment means a detailed comprehensive analysis prepared pursuant to Section 44361 to evaluate and predict the dispersion of hazardous substances in the environment and the potential for exposure of human populations and to assess and quantify both the individual and population-wide health risks associated with those levels of exposure." Health risk assessments require a number of inputs for risk characterization. Exposure assessment is only one of them and exposure information alone does not constitute a risk assessment. In order to characterize the risks from exposure one needs information on the toxicity of the chemicals emitted. The acute and chronic reference exposure levels for noncancer endpoints, and the cancer potency factors function as measures of the toxicity and are used quantitatively to assess health risks. Development and compilation of existing cancer potency factors and reference exposure levels is integral to the development of comprehensive risk assessment guidelines. Costs of developing the reference exposure levels and cancer potency factors were included in the cost estimations of SB 1731 legislation prepared for the legislature. It was therefore clear from the beginning that some effort was going into developing these toxicity criteria. U.S. EPA has neither the resources nor the mandate to address the chemicals subject to Californias Air Toxics Hot Spots Act.
Comment: The guidelines establish values and methodologies that will be used in the risk assessment process. They also introduce risk management elements that will bias regulatory decision making. For example, in addressing Risk Characterization (Presentation of Results, pg. 12), OEHHA uses a hazard index of 0.5 as a trigger for evaluation of, and inclusion of, the potential additive health risk from background concentrations of criteria air pollutants for respiratory irritants. This provision is not mandated by AB 2588 or SB 1731 and would limit CARB and local district discretion in making cost-effective risk management decisions. Such initiatives should be addressed independently of the revised risk assessment guidelines to allow for full consideration of potential risk management implications (e.g., increase in a facilitys risk above a district notification threshold due to the conservative default assumption of additive toxicity from background criteria air pollutants). It is critical that risk assessment and risk management activities be considered separately, so that informed regulatory decisions can be based on a full evaluation of all relevant factors. Therefore, we recommend that OEHHA remove all such risk management references from the draft. Of course, we recommend that subsequent draft guidelines also observe this critical separation between risk assessment and risk management.
Response: The proposal to consider background levels of criteria air pollutants has been dropped.
Comment: The Executive Summary of the Technical Support Document (pg. iv) states that "The RELs also have application in characterizing health risks in event of unplanned releases." This statement suggests an inappropriate broadening of the applicability of these guidelines, which are being developed under legislative mandate for the express purpose of addressing the conduct of health risk assessments for facilities under the AB 2588 program. Such expansion of the guidelines applicability beyond conducting AB 2588 risk assessments appears to exceed the legislative intent and authorization of SB 1731. In addition, given the questionable scientific basis of the animal data used to derive some of the REL values (see Appendix 1), it is clearly premature to contemplate broadening the regulatory applicability of the proposed RELs. Moreover, we are concerned that such statements may be cited inappropriately in tort litigation against facilities, as supporting exaggerated claims of adverse health effects simply because an REL may have been exceeded during an accidental release. Full consideration of the compounded conservatism in establishing RELs, particularly in the choice of "endpoints of toxicity" in the hazard identification phase, combined with the default application of ten-fold uncertainty factors, and the methodology proposed for addressing the relative contribution of concentration and time using a modification of Habers Law in the dose-response phase, clearly leads to the conclusion that the resultant acute RELs are uniformly set at levels that are likely one or more orders of magnitude below exposures that actually result in injurious effects. We recommend that OEHHA strike this statement from the draft document, and add a precautionary statement which clearly addresses such inappropriate applications of the guidelines.
Response: The proposed acute Reference Exposure Levels were already under development prior to the passage of SB 1731. The effort to develop acute RELs was started in 1989 (under a different program in conjunction with Californias Office of Emergency Services), and the guidance document thus produced was publicly reviewed in 1991. When SB 1731 was passed, we expanded our efforts to include evaluating exposures to routine emissions. OEHHA initially took the existing guidelines and modified them to fit the Air Toxics Hot Spots program risk assessment guidelines by developing RELs for one hour community exposures. OEHHA has since altered the document to emphasize its applicability in conducting risk assessments under AB 2588.
As part of our reevaluation of the acute RELs following public comment, OEHHA has analyzed the use of the benchmark concentration to reduce uncertainty and the magnitude of the uncertainty factors. Where data are adequate, we have used the benchmark concentration approach. The toxicological endpoint reflects the scientific literature and does not introduce "compounded conservatism". The application of default ten-fold uncertainty factors in a REL calculation accounts for the lack of scientific information (uncertainty) in extrapolating from animals to humans and the degree of interindividual variability in the human population. There are no data to suggest that the RELs are set at levels "one or more orders of magnitude below exposures that actually result in injurious effects". It is because inadequate data are available that uncertainty factors are used. OEHHA is currently studying the degree of protection which 10-fold uncertainty factors afford.
Comment: Health based ambient air quality standards have been established for criteria air pollutants under federal and state ambient air quality programs. Under these programs, facilities must meet stringent criteria pollutant emission standards for existing equipment and any new or modified equipment. Inclusion of criteria air pollutants in the AB 2588 program (Table 1) will overlap efforts of ambient air quality programs. Such action will increase AB 2588 compliance costs and complicate the program without a corresponding improvement in human health and environmental protection. Criteria pollutants are not listed as hazardous air pollutants (HAPS) under Section 112 (42 USC section 7412(b)) and are therefore not required to be defined as a toxic air contaminant under state law. Criteria pollutants are not among the substances required to be quantified in the AB 2588 program. In addition, SO2, NO2, and ozone are not included in any of the substance lists in H&SC section 44321. In view of these facts, criteria pollutants should not be listed as toxic air contaminants.
Response: There has been no attempt at listing criteria air pollutants as toxic air contaminants. Since exposure occurs simultaneously to criteria air pollutants as well as hot spots chemicals emitted from a facility, from a scientific standpoint, evaluation of the health impacts from exposure to criteria air pollutants and hot spots emissions makes sense. In spite of this, consideration of background concentrations of criteria pollutants will not be required in the Hot Spots Program.
Comment: The guidelines provide examples of facility emissions that must be evaluated in the risk assessment, including venting to flares and pressure relief valves (pp. 4). The facility risk assessment mandated by the Legislature for the AB 2588 program applies specifically to impacts due to air releases that result from routine operation of a facility, or release that are "predictable". The above-referenced examples should include language clarifying that the guidelines are only applicable to routine or predictable facility emissions.
Response: Health and Safety Code Section 44303 defines "air releases" as "any activity that may cause the issuance of air contaminants, including the actual or potential spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing of a substance into the ambient air and that results from the routine operation of a facility or that is predictable, including, but not limited to, continuous and intermittent releases and predictable process upsets or leaks." Venting to flares and pressure relief valves are predictable occurrences. Therefore, they should be included in evaluating health risks from facility emissions.
Comment: The AB 2588 program is intended to identify risks from individual facility emissions. In discussing the legislative intent of the AB 2588 program, H&SC section 44301 makes explicit reference to "specific sources". Subsection (h) states: "it is in the public interest to ascertain and measure the amounts and types of hazardous releases from specific sources that may be exposing people to those releases, and to assess the health risks to those who are exposed." There is no legislative mandate to address multiple-facility impacts. OEHHA guidance should not overreach clear legislative intent. All references to requirements or recommendations associated with multiple facility impacts should be removed from the draft.
Response: H&SC section 44301 (d) states that toxic air releases "may create localized concentrations or air toxics "hot spots" where emissions from specific sources may expose individuals and population groups to elevated risks of adverse health effects, including, but not limited to, cancer and contribute to the cumulative health risks of emissions from other sources in the area." It is clear that the legislature is concerned about cumulative exposures. Based on this statement, a District at its discretion may do an analysis of multiple facility impacts and ask for information from facilities in order to conduct such an analysis. OEHHA never intended to imply that a facility operator do an assessment of the risks from neighboring facilities.
The following comments specifically address the methodology used by OEHHA in developing the draft guidelines:
Comment: The use of uncertainty factors, and their magnitude, must take into account the severity of the effect against which the public is being protected. Particularly for Level I Acute Toxicity Exposure Limits (generally the REL), the endpoint on which the exposure limit is based is generally a mild effect of questionable toxicological significance (mild respiratory irritation, mild eye irritation, minimal signs of CNS depression). In many cases an uncertainty factor far less than 10 (e.g. 2-3) would provide adequate protection.
Response: OEHHA has modified its uncertainty factor methodology and now utilizes an uncertainty factor less than 10 under certain circumstances. For example, for benchmark concentration calculations, the interspecies uncertainty factor for animal studies and the intraspecies uncertainty factor for human studies has been changed to 3. Similarly, for sensory irritation, the uncertainty factor for LOAEL to NOAEL extrapolation has been reduced from 10 to 3.
Comment: An example of the inappropriate use of ten-fold uncertainty factors is provided in the calculation of the REL for methanol (REL = 2.1 ppm). Following exposure of 12 young, healthy men to 190 ppm for 75 minutes, two of 20 tests in a neurobehavioral/neurophysiological battery showed statistically significant effects. The two tests involved measured fatigue and concentration, and visual evoked potentials, both transient, questionable toxicological endpoints. In addition, while the effects were statistically significant, in both cases they were within the normal range of test values for subjects during sham exposures (Cook et al., 1991).
In determining the REL, OEHHA considered 190 ppm the LOAEL, and applied two ten-fold uncertainty factors; one to account for LOAEL-to-NOAEL conversion, and the second to account for "interspecies (intraspecies) variability." Following the application of Habers Law to adjust from a 75 minute experimental exposure to a one-hour exposure limit, the REL (Level 1 Exposure Level) was determined to be 2.1 ppm. Given the minimal "effect" and questionable significance of the effects observed, it appears appropriate to use uncertainty factors far lower than ten.
Furthermore, we believe that the effects observed in this study, which serve as the basis for calculating the REL, do not constitute a LOAEL, and should be considered a NOAEL, thus eliminating the ten-fold uncertainty factor for conversion from LOAEL to NOAEL. It is also unlikely that intraspecies differences in sensitivity to such a non-specific endpoint (minimal signs of CNS depression) would span an order of magnitude (ten-fold uncertainty factor).
Response: OEHHA has revised its interpretation of the Cook et al. (1991) study; the exposure level reported in that study is considered to represent a NOAEL. No data is presented to document the magnitude of intraspecies variability, so the default uncertainty factor of 10 is used. The REL has been appropriately revised in the Technical Support Document from 2.8 x 103 to 2.8 104 µg/m³.
Comment: Finally, given the minimal "effect" on which the REL is based, including its questionable significance and transitory nature, it is prudent to re-evaluate the default application of a ten-fold uncertainty factor. In such a case, the minimal
severity and ready reversibility of the "toxic endpoint" against which the public is being protected suggest that the application of a much smaller uncertainty factor (e.g., two- to three-fold) would provide an adequate margin of error.
Response: OEHHA has defined specific criteria for using reduced uncertainty factors. The data do not indicate that a reduced uncertainty factor is warranted for central nervous system endpoints or for intraspecies variability in general. In fact, for compounds for which such data are available, human variability may range from 7-fold to several orders of magnitude (Horstman D et al., 1986; Hattis D, 1996). Furthermore, it is precisely because the effect is subclinical and reversible that it is considered a mild, not a severe, adverse effect. The REL is intended to protect against adverse effects and the REL for methanol is consistent with this purpose.
Comment: Note also that the Level III l-Hour Acute Toxicity Exposure Limit for methanol is 40 ppm. The accompanying text states: "Exposure to methanol above this level may result in death due to respiratory or cardiac arrest." While this statement is technically accurate exposure to methanol at some level, significantly above 40 ppm, would result in death due to respiratory or cardiac arrest; establishing the Level III Acute Exposure value at 40 ppm is clearly a gross overstatement of the acute hazard posed by this chemical. Furthermore, this Level III exposure limit is completely inconsistent with the current 8-hour TLV of 200 ppm. While we understand OEHHAs concerns relative to establishing RELs based on TLVs, the 8-hour TLV for methanol of 200 ppm suggests that significant industry-sponsored exposure assessment data are available from routine industrial hygiene monitoring. This data suggests that significantly higher acute exposures are tolerated within the human population with no adverse effects.
Response: OEHHA agrees that the life-threatening level for methanol is overly conservative and has substituted the 1996 NIOSH IDLH value of 6,000 ppm (7860 mg/m3).
Comment: Beyond the example cited above for methanol, routine, default application of a tenfold uncertainty factor is inappropriate for many of the 54 chemicals for which acute RELs are established in the draft guidance. Some endpoints of toxicity (e.g., respiratory irritation resulting from direct tissue damage from exposure to caustics) would be expected to produce a dose-response relationship that is essentially the same in all mammalian systems, and such chemicals are therefore particularly good examples of where the default application of a ten-fold uncertainty factor is inappropriate.
Response: OEHHA has defined specific criteria for the use of uncertainty factors less than 10, as outlined above. OEHHA encourages the commentator to submit data supporting factors for extrapolation for specific toxicological endpoints other than the factor of 10.
Comment: As cited above for methanol, there are a number of chemicals for which the selection of a "toxicologically significant" endpoint on which to base the establishment of an acute exposure limit is questionable. As has long been debated in the evaluation of chronic non-cancer endpoints, there are many effects that are observed following exposure to chemicals that are measurable, but which are not toxicologically significant, and merely reflect an adaptive response in the organism. The draft acute exposure guidance should be carefully reviewed to assure that the endpoints used as the basis for calculating RELs and/or Level I, II, or III Exposure Levels are appropriate for use as the basis of the hazard identification phase of acute health risk assessment.
Response: No specific examples of this concern or recommendations are given in the comment. However, OEHHA agrees that toxicologically significant endpoints should be used as the bases for the RELs and every effort has been made to ensure that this is the case. The identification of the critical endpoint and study are vital to determining a useful REL.
Comment: Historically, AB 2588 risk assessments evaluated only those chemicals with state approved health effects values. According to the draft (Part 1, pp. 7), facilities preparing risk assessments pursuant to AB 2588 would be required to quantify emissions and estimate potential acute health effects for all listed AB 2588 chemicals emitted by their operation, even for those chemicals for which OEHHA RELs and exposure levels have not been developed. Once health effects values, including acute RELs, have been developed, these chemicals will need to be evaluated at each step in the AB 2588 process. We are concerned that OEHHA has not fully considered the potential ramifications of their proposed "interim" REL process on existing AB 2588 programs.
Response: OEHHA has withdrawn this proposal.
Comment: Current regulations (approved by OAL 1/31/94) require that low, medium, and high priority (non-significant risk) facilities submit a Summary Update Form every four years. Part C of this form requires that the operator certify what changes, if any, have occurred since the last inventory period that contribute to facility risk. Currently, only those substances with state-approved health effects values are considered in evaluating facility risk. However, OEHHAs proposal suggests that all listed substances would need to be evaluated. This proposal could have a significant effect on facility risk between inventory updates, thereby necessitating a full inventory plan and report for many facilities. Recent agency/industry inventory streamlining efforts would be nullified.
Facility prioritization scores would need to be recalculated to evaluate emissions of all substances with health effects values. For some facilities (e.g., petroleum exploration & production) the number of substances could more than double. This change could drive many facilities, currently classified as low and medium priority, into a high priority classification, triggering risk assessment requirements.
Response: As new reference exposure levels are adopted, some facilities may need to provide more information. This does not nullify streamlining efforts. Concern that a facility might have to provide more inventory information or may need to be reprioritized should not prevent the development of reference exposure levels for listed substances.
Comment: As noted above, the calculated facility risk is assumed to increase under OEHHAs proposal. As a result, certain facilities may trigger existing action thresholds (e.g., notification). However, these thresholds reflect our current understanding of cumulative facility risk based on a limited universe of substances. By substantially expanding the universe of substances, we are changing the meaning of calculated risk. In addition, for substances with limited health effects data, facilities would have to develop overly conservative values that may substantially overstate risk estimates. Risk assessments would be based on data of grossly unequal quality.
OEHHAs "interim" REL proposal will also result in different facilities developing different values for the same chemical. It is not clear if, when, or how OEHHA might supplant "interim" values with a single state standard -- the draft guideline does not suggest a protocol for this purpose. However, it is clear that the proposed process will generate new information for many chemicals on a continuous basis. We are concerned that OEHHA may use this information to adjust RELs on a continuous basis. Such action would place an inordinate administrative burden on facilities, districts and the state. For example, facilities would be compelled to continually update emissions inventories and HRAs to reflect the most current data. The cost and time associated with conducting risk assessments would increase dramatically. Moreover, the draft acute guidelines do not discuss the process by which OEHHA will approve interim RELs. This process will should be developed before facilities are required to calculate their own RELs.
Clearly, OEHHAs "interim" REL proposal must be subject to a thorough cost-benefit analysis before it is implemented.
The Proposed "Interim" REL Process Should be Compatible With OEHHAs Statutory Requirements for Evaluating Health Effects.
All New or Updated Health Effects Values Should be Subject to Standard Public and Peer Review Processes.
Response: OEHHA agrees with the comment. As stated above, the proposal for "Interim RELs" has been withdrawn. All updates of RELs are subject to public and peer review.
Comment: In determining the applicability of federal MACT standards, Section 112 General Provisions require that facilities evaluate only emissions of substances for which EPA has assigned appropriate and relevant health values. For example, in determining whether a facility is a "major source" of emissions, E&P facilities are required to evaluate emissions of 16 chemicals. The guidelines should reflect federal policy, or clearly justify the need for a more stringent approach based on human health and environmental benefit (AB 1144, AB 969, SB 1082).
Response: The Air Toxics Hot Spots program is designed to evaluate emissions of a specified list of substances. What the federal government does under separate statutes and for different purposes does not affect the implementation of the Hot Spots Act. Thus, we are evaluating health effects of many of the chemicals listed in the Air Toxics Hot Spots list of substances.
Comment: The requirement for consideration of "background concentrations" of criteria air pollutants is beyond the scope of AB 2588 and should be removed from the guidelines. Historically, AB 2588 focused on health risks associated with individual facility emissions. The draft requires that facilities also include background concentrations of criteria pollutant emissions in their risk assessments if the acute hazard index for their corresponding toxic endpoint is greater than 0.5 (pp. 13). This is not appropriate because source concentrations of criteria pollutant emissions have already been accounted for in the risk assessment. In addition, the toxic components of source criteria emissions are accounted for in the risk assessment. Evaluating background concentrations in addition to source concentrations will effectively double count facility emissions.
Given contributions from other stationary, area and mobile sources, consideration of background concentrations could subject a facility to more stringent regulatory requirements due to emissions that are beyond the control of that facility. For example, consideration of background concentrations could raise a facilities hazard index level above 1, triggering public notification requirements in most districts. Consideration of background concentrations will also substantially increase facility administrative burden associated with the risk assessment process. For example, facilities could be required to evaluate their impact to receptors located in areas where their 0.5 HI isopleths overlap those of surrounding facilities. The proposed requirement for consideration of "background concentrations" of criteria air pollutants must be subject to a thorough cost-benefit analysis before it is implemented.
Response: OEHHA has withdrawn the proposal to include background criteria air pollutants in the risk assessment. Historically, background criteria air pollutant concentrations have been included in some AB 2588 risk assessments in evaluating the hazard index for respiratory irritation. The facilitys emissions of criteria air pollutants have not been included in the risk assessment. Furthermore, no districts have used background criteria air pollutant contributions as a trigger for notification.
Comment: Any hazard identification information that has not been developed and provided by OEHHA should not be required. The draft guideline requires that risk assessors provide information, when HI exceeds 0.5, for emitted chemicals that can impact a particular health endpoint but which are not included in the HI calculation. To assure consistency among risk assessments, and to minimize costs, such information should not be required. Providing supplemental information should be an option exercised at the facilities discretion.
Response: OEHHA has withdrawn the proposal to provide information for hazard indices above 0.5.
Comment: Reference Exposure Levels for many chemicals are, understandably, based on toxicity studies conducted in laboratory animals, with NOAELs adjusted by ten-fold uncertainty factors to account for potential interspecies and intraspecies differences. In most cases, the resultant RELs are much more stringent than current occupational exposure limits supported by health effects data in exposed humans. In such cases, particularly where occupational exposure data have been collected, but not reviewed by OEHHA, RELs derived from occupational exposure data should be directly applicable to human health effects endpoints with only the potential application of an uncertainty factor (of appropriate magnitude) to account for potential intraspecies variability within the human population.
Response: It is inappropriate to directly compare or attempt to use occupational standards for the general populace. Where occupational exposure data represent the best available toxicological data, we would use these data. Very often, occupational standards are not based on rigorously examined epidemiological data, but appear to be anecdotal in nature.
Comment: Appendix 1 contains a review of the OEHHA methodology used to derive RELs. This review was prepared by a third party consultant on WSPAs behalf. Comments are provided on the general selection of data used to derive RELs, use of a modification of Habers Law in the process, and use of the Benchmark Dose approach. An alternative method for deriving acute RELs that may merit further discussion is also provided as an attachment to Appendix l.
Appendix 1 contains a review of the methodology applied by OEHHA to establish RELs for several specific chemicals. A critical review of the methodology used to establish RELs for five chemicals of clear significance to our industry are included as Appendix 1. However, the omission of additional chemicals should not be perceived as concurrence with the methodology applied by OEHHA. In addition to the chemicals addressed in Appendix 1, each of the remaining 49 chemicals should be peer reviewed in a similar fashion by an independent reviewer, outside of Cal EPA. The following five chemicals were reviewed by a third party consultant (ICF Kaiser Engineering, Inc., Ruston, LA) on WSPAs behalf:
Response: See responses to specific technical comments by ICF-Kaiser, below.
Comment: Revisions to the process of conducting health risk assessments under the AB 2588 Program should be focused on improving the process and reducing uncertainty. Therefore, for many of the chemicals for which acute RELs are either proposed or planned, it is critical that OEHHA identify data gaps for each specific chemical evaluated to identify where resources are best spent on strengthening the data upon which acute RELs are based. Before setting such strict exposure limits as proposed in the draft acute guidelines, OEHHA should clearly identify data gaps for each chemical that, once filled, will substantially reduce the identified uncertainty, thereby allowing for more accurate prediction of risk and more scientifically defensible exposure limits. Consistent with this reduction in the uncertainty surrounding health risk assessments, OEHHAs draft guidelines should clearly identify a process for incorporation of additional scientific data to reduce the uncertainty surrounding the development of acute exposure levels (including the REL) for use in the AB 2588 risk assessment process.
Response: The REL development process uses an iterative approach. Review by the regulated community provides opportunity for submission of further scientific data. If the commentator has data to submit regarding specific chemicals, OEHHA will review the data. Additionally, OEHHA plans to update the RELs on an on-going basis. All updates will undergo public comment and independent review by ARBs Scientific Review Panel.
Horstman D, Roger LJ, Kehrl H, Hazucha M. Airway sensitivity of asthmatics to sulfur dioxide. Toxicol Indus Health 1986; 2:289-298.
Hattis D. Variability in susceptibility-how big, how often, for what responses to what agents? Environ Toxicol Pharmacol 1996; 2:135-145.