MAY 1 h ISO*

Sheila McVeigh Ocean County C i t i z e n s f o r Clean Water P.O. Box 4724 Toms River, New Jersey 087 54-4724

Re: Response t o Comments Dated September 22, 1993 and October 28, 1993 on EPA's D r a f t Baseline Public Health Risk Assessment, Dated J u l y 2, 1993 f o r the CIBA-GEIGY Superfund S i t e

Dear Ms. McVeigh:

This l e t t e r i s i n response t o the comment l e t t e r from the Hampshire Research I n s t i t u t e , dated September 22, 1993 and comments dated October 28, 1993, regarding EPA's D r a f t Baseline Public Health Risk Assessment f o r the CIBA-GEIGY (Ciba) Superfund S i t e , which i s dated J u l y 2, 1993.

The responses t h a t f o l l o w on the attachment have been s e q u e n t i a l l y numbered and cross referenced t o match your o r i g i n a l comments. Please note t h a t your o r i g i n a l comments have been summarized f o r b r e v i t y and EPA's responses are intended t o address a l l the issues r a i s e d i n the o r i g i n a l comment. Moreover, except as noted i n EPA's response t o the f i r s t comment l i s t e d below, i t i s assumed t h a t your comment l e t t e r dated September 22, 1993 has been superceeded by your comment l e t t e r dated October 28, 1993.

Please c a l l me a t (212) 264-3774 should you have any questions or comments on any of the i n f o r m a t i o n contained h e r e i n .

Yours t r u l y ,

Stephen Cipot P r o j e c t Manager

Southern New Jersey Superfund Section I I

Attachments

cc: Ian C u r t i s , NJDEPE bcc: Stephen Cipot, SNJSII

Pat Hastings, CDM

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1. Comment t Commentary stated that EPA's Draft Baseline Public Health Risk Assessment (RA) does not make use of the data obtained during CDM's remedial investigation. OCCCW's comment was further outlined in a conference telephone c a l l on October 6 and 7, 1993 between Hampshire Research Institute and EPA's Project Manager. During the conversation, Hampshire Institute (HRI) cited three sections of the RA report where a reader could be misled into believing that the current RI had not been evaluated.

1. Response: EPA's Draft RA Report utilized the current EPA remedial investigation (RI) data, and this i s clearly noted on page 2 of the Executive Summary. Furthermore, these data were included as Appendix D of the draft report: Site Surface Soil Data, as indicated under Section 10.O/References in the report's Table of Contents. However, EPA agrees that a reader may consult one of the sections of the RA without having f i r s t reviewed the Executive Summary or referred to the Table of Comments, the language in these sections w i l l be cla r i f i e d to ensure that the reader i s not misled.

Comments From The Hampshire Research Institute (for the Ocean County Citizens for Clean Water) (HRI/QCCfJW)

2. Comment: Summary, Bullet 1? Page 2 A key consideration to bear in mind in evaluating the RA i s that i t only considers a narrow view of risks represented by source areas. The assessment considers s o i l exposure per se, but does not address any of the soi l contamination I n these areas to other exposure pathways (e.g. as a source of continued discharge to groundwater).

2. Response: Please note that the report clearly states that i t i s a surface s o i l risk assessment and was not intended to evaluate subsurface s o i l contamination discharge to groundwater.

As stated in Section 1.1 of the Work Plan for this RA, EPA acknowledges that site matrices including surface s o i l , subsurface s o i l , and groundwater have been found to contain chemical contamination. The objective of this RA was solely to characterize the potential health risks posed by the chemicals present in the surface s o i l matrix to a potentially exposed human receptor population (the marshlands was excluded as EPA has previously assessed these risks and found the risks to be below EPA's point of departure. The risk posed by exposure through the groundwater matrix was previously addressed in 1988 by the NUS Risk Assessment and therefore, such was not intended to be quantitatively addressed in the present study. Moreover, the Record of Decision (ROD), and subsequent Explanation of Significant Differences (ESD) for groundwater contamination from the Ciba Site, Operable Unit One (OUI) provided a remedy that was protective of human health and the environment, and w i l l prevent against potential risk resulting from exposure to contaminated groundwater. The risk posed by the subsurface s o i l matrix w i l l be separately evaluated and the method

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of evaluation of ri s k s posed by the subsurface s o i l matrix i s currently under EPA consideration. Presently, EPA anticipates evaluating these through batch/column leaching studies; OCCCW w i l l be forwarded a copy of the d r a f t work plan f o r your review and comment when i t i s available.

3. Comment; Summary. Bullets 2 and 3; Page 2 The RA inappropriately excludes chemicals from the r i s k assessment on the basis of a crude screening methodology, despite a clear injunction against doing so i n EPA guidance. This adds t o the problem caused by l i m i t e d sampling i n the source areas, noted i n the attached memorandum.

For those chemicals that were eliminated from quantitative assessment using t h i s crude screen, no meaningful q u a l i t a t i v e r i s k assessment i s presented.

3. Response; We are unaware of an inj u n c t i o n i n EPA guidance against the screening of chemicals. I n f a c t , EPA RAGS (page 5-23) specifies the use of the chemical concentration-toxicity screen. This RA followed the EPA Region I I standard practice of u t i l i z i n g RAGS guidance i n reducing the number of chemicals carried through the RA. Section 2.1 of the d r a f t RA (pages 42-46) c l e a r l y discusses a l l the c r i t e r i a used i n the screening process as derived from pages 5-20 through 5-24 of the RAGS guidance document. This issue i s further discussed i n response t o HRI/OCCCW comment # 7 specific t o the selection of chemicals of concern. This method i s used and accepted i n many r i s k assessments f o r EPA Region I I .

Further, chemicals which contributed greater than 1% to the ove r a l l r i s k were selected as chemicals of concern. The chemicals screened from further evaluation i n d i v i d u a l l y contributed less than one percent t o the overall r i s k . Thus, the selected chemicals are considered the most representative of s i t e conditions and the greatest contributors t o human health impacts. For completeness, those chemicals which could not be evaluated q u a n t i t a t i v e l y i n the concentration-toxicity screen due to the lack of established t o x i c i t y values were q u a l i t a t i v e l y addressed i n Section 4.3 of the Risk Assessment, Appendix B Toxicological P r o f i l e s , and Section 6.0 Uncertainties i n Risk Assessment. Accordingly, both q u a l i t a t i v e and quantitative evaluations are presented i n the RA to allow EPA to then assess impacts from p o t e n t i a l source surface s o i l contamination at the Site.

4. Comment: Summary Bullet 4; Page 2 The exposure assessment does not consider a l l relevant s o i l contamination exposure pathways f o r future r e s i d e n t i a l exposures, and uses non-conservative exposure parameters i n several cases. I n some cases, i t f a i l s to note multiple exposures tha t w i l l a f f e c t a given population.

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4. Response: In response to this comment, the exposure assessment was performed in accordance with EPA RAGS and most recent EPA Region I I guidance using reasonable maximum exposure (RME) assumptions. The intent i s to estimate a conservative exposure case that i s s t i l l within the range of possible exposures.

Regarding consideration of s o i l contamination exposure pathways for future residential exposures, the comment does not specify the particular issues which the pathways excluded. I t i s assumed that the comment focus was the exclusion of the trespasser scenario for future use. Regardless, the RA did consider a l l relevant pathways.

Specifically, Table 3-1 of the RA presents future-use scenarios for residents, s i t e workers, construction workers, and trespassers considered for ingestion, dermal contact, and inhalation exposures to surface s o i l . Trespassers were not quantitatively evaluated under the future-use scenario since their exposure would be the same as that of the present-use scenario. In addition, trespasser exposure i s much less than exposure to other receptors ( i . e . , residents, s i t e workers, and construction workers).

Regarding exposure to multiple areas, although the comment i s noteworthy, i t would be highly subjective to attempt to identify different potential source areas that each receptor group may routinely come into contact with, how often they may v i s i t each area (exposure frequency), and for how long they might be exposed (i.e. , exposure time and duration). For this reason, the RA was complete assuming that the receptor would spend the entire exposure duration at each individual source area. Exposure routes were combined to show total carcinogenic risks and total noncarcinogenic hazard index values for each individual source area. This method serves to identify the source areas which might present potential health problems (i.e . , exceeded target level s ) .

5. Comment: Summary. Bullet 5; Page 2 The calculation of Preliminary Remediation Goals (PRGs) f a i l s to appropriately address the presence of multiple contaminants or the existence of multiple exposure pathways.

5. Response: The PRGs presented in the RA were developed in accordance with EPA RAGS Part B guidance, which specifies the derivation of PRGs for individual compounds. Although the PRGs are calculated for individual contaminants, exposure to multiple contaminants can be simply assessed as follows. Since PRGs were calculated for five carcinogens at a target risk level of lxlO"6, exposure to these five contaminants at the PRG concentration would result in a cumulative risk of SxlO"6.

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As indicated in both the text and Table 7-2, worker PRGs for Ciba surface soils were calculated based on multiple exposure pathways, including ingestion of s o i l s and inhalation of particulates. In accordance with RAGS Part B, the residential surface s o i l PRGs for this Risk Assessment included the ingestion route of exposure only.

6. Comment; "Problem Definition?" Page 3 This assessment deals with direct s o i l exposure pathways only,... Remedial design for these source areas must also consider the contribution of sources to groundwater - mediated pathways, and not assume that the f i r s t operable unit adequately addresses that exposure pathway.

A clear statement of context i s needed for this risk assessment, noting that the risks that are evaluated are not the only risks posed by these contaminated areas, or even by the surface soils in these areas.

6. Response: Please see the response #2 to HRI/OCCCW above, regarding the scope of this report solely as a surface s o i l risk assessment. Although the contribution of surface soils to groundwater may affect the choice of an Operable Unit Two (OUII) remedy for source control, EPA maintains that the remedy mandated in the ROD for OUI i s fullv protective of human health and the environment as related to the Site groundwater contamination.

The Final RA w i l l be c l a r i f i e d to state that surface s o i l s are not the only potential risks associated with the Site.

7. Comment: "Selection of Source Areas for Evaluation:" Page 3 The discussion on p. 34 i s cause for some concern, ... Four areas that are likely to be contaminated are excluded from evaluation, because they are asphalt covered or under water...

While this criticism i s less pressing for those areas that have been paved or covered with a substantial amount of clean f i l l , (assuming such covers remain intact), i t i s c r i t i c a l to remember that the only exposure pathways that involve s o i l contact are eliminated. These areas may contribute to chemical exposure by other mechanisms, including continued contamination of the aquifer.

7. Response: This surface soils RA considered risk to each potentially exposed receptor group (residents, s i t e workers, construction workers, and trespassers) for each appropriate source area by exposure routes (ingestion, inhalation, and dermal contact). As summarized on page 34 of the report:

"In conclusion, of the fourteen source areas described above, only ten have been evaluated in this surface s o i l baseline public health risk assessment^as surface s o i l samples could not be collected from the Old Wastewater Treatment Plant, the Overflow Basin, and the Ocean Outfall Basin as these were

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either asphalt-covered or under water, making i t impossible to collect any surface s o i l s and thus eliminating these covered areas as a possible source of pathway of exposure. For the Suspected East Overflow Area, subsurface s o i l sample analyses did not reveal the presence of chemical contamination; therefore, surface s o i l samples were not collected."

Since the source would need to be exposed for ingestion, dermal contact, or inhalation to occur, the four source areas cited were not considered further. For clarity, the following text per source area w i l l be integrated into the report:

Old Wastewater Treatment Plant: The current wastewater treatment plant was constructed over the Old Wastewater Treatment Plant, and was completely covered by buildings, tanks, and asphalt. Although surface s o i l exposure would not be an issue, EPA's contractor made borings and took subsurface samples which w i l l be appropriately addressed in the forthcoming evaluation of the subsurface matrix.

Overflow Basin: At the time of the RI, this basin was decommissioned with the removal of the standing liquid and bottom liner. However, the remaining sludge underneath was sampled during the investigation and w i l l be appropriately addressed in the forthcoming evaluation of the subsurface matrix.

Ocean Outfall Basin: The sludge layer was covered with layers of sand, soda ash, plastic and more sand, thus eliminating surface s o i l contamination. However, borings to characterize subsurface soi l s (including the remaining sludges) were made during EPA's RI and w i l l be further addressed in the forthcoming evaluation.

Suspected East Overflow Area: Other than suspect aerial interpretation, there i s no evidence that an actual impoundment ever existed in this area. This, coupled with inconclusive evidence from previous results from s o i l analyses plus the lack of subsurface contamination (where contamination levels have been characteristically higher than surface soil) found during the CDM Federal RI, indicate an improbable surface s o i l risk.

As previously stated, assessment of the "other mechanisms" of exposure, including continued migration of contaminants to the aquifer, were not the objective of this RA. However, as noted in the response to HRI/OCCCW comment #5, the Final RA w i l l be clarified to state that the surface so i l s are not the only potential risks at the Site.

8. Comment: Selection of Chemicals of Concern; Pages 3-6 As a matter of general principal, i t i s not good practice to eliminate any chemical from consideration in the risk assessment. . . . The Revised Draft does not adequately ju s t i f y the exclusion of chemicals from analysis, but merely asserts that i t was necessary (p. 42). EPA should re-examine this decision.

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Specific c r i t e r i a used to select chemicals ̂ for analysis are troubling, as i s the apparent practice of eliminating a chemical on the basis of any single such c r i t e r i a . I t would be better to follow the preferred procedure from RAGS evaluating a l l chemicals.

The discussion of the selection of the chemicals of concern for the Calcium Sulfate Disposal Area i s i l l u s t r a t i v e of the problems involved in using a screening method to prematurely eliminate chemicals from detailed analysis...

Because the concentration/toxicity scheme i s crude, and ignores v i t a l information on concentration (other than the maximum detected concentration) and real exposure potential, i t may give misleading results. Both mean and maximum concentrations should be used in screening, and a chemical analyzed that qualifies on either basis.

Because toxicity/concentration screens do not consider information that may drastically affect the exposure potential of a chemical, relative to i t s concentration, these should not be used to exclude any chemicals with known potential for bioconcentration or bioaccumulation... Aldrin and chlordane, for example, have significant bioconcentration factors (of 3,900 and 38,000) while chrysene, heptachlor epoxide, and dieldrin a l l have octanol water partition coefficients greater than 100,000...

OCCCW disagrees with the elimination of aluminum as an essential nutrient.

The description of the concentration/toxicity screen on p. 46 notes that chromium was classified as 85% trivalent and 15% hexavalent, in accordance with IRIS. This i s an extremely dangerous use of default values... and site-specific efforts at determining the form of chromium present at the site would be much better...

Footnote 1; p. 4, I t should be noted that the c r i t e r i a listed on page 43 differs significantly from those on p. 37...

8. Response; I t i s not true that i t i s not good practice to eliminate chemicals from consideration in a risk assessment or that i t i s preferred procedure to evaluate a l l chemicals in the RA. EPA RAGS guidance was followed in the production of this RA in accordance with EPA Region I I policy. RAGS judiciously allows reduction of the number of chemicals for several reasons. RAGS cites the fact that a large number of chemicals "may distract from the dominant risks presented by the s i t e . " Pages 42-46 Section 2.1 of the RA indicate that chemicals were reduced to the most significant contributors to overall risk and further discusses a l l selection c r i t e r i a utilized. These c r i t e r i a were applied as a whole in the elimination of chemicals from consideration in the RA; chemicals were not eliminated on the basis of any single c r i t e r i a , as implied in the comment.

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Specific to the comment regarding the selection of the chemicals of concern for the Calcium Sulfate Disposal Area, 33 chemicals i s indisputedly a large number of chemicals to carry through the RA process. As previously noted, RAGS states that a large number of chemicals may distract from the dominant site risks, in addition, they may make tables and text d i f f i c u l t to read and understand; EPA believes that such i s clearly exemplified in the case of the Ciba source areas. For the Calcium Sulfate Disposal Area, 9 chemicals of potential concern (which contribute greater than 98% to the total risk for the source area) were selected for quantitative assessment in the RA. The remaining 24 chemicals not retained obviously contribute minimally to overall risk.

For other comments specific to the application of a concentration toxicity screen (including mean and maximum concentrations, exposure potential, and bioconcentration or bioaccumulation), EPA reasserts that the selection of chemicals was performed per RAGS. (It i s further noted that the impact of water partition coefficients should be of l i t t l e consideration as this i s a surface soils assessment).

The c r i t e r i a for elimination of aluminum w i l l be further discussed in the Final report. Although the current quantitative discussion of aluminum in Section 4.3 of the RA accurately characterizes aluminum, i t i s accepted that the discussion of minerals as outlined on page 43 of the draft report currently erroneously includes aluminum as an essential nutrient rather than specify that i t i s ubiquitous in s o i l , air, and water (Casarett and Doull, 1986) and not Site-related.

Regarding the RA's use of default values for chromium speciation rather than Site-specific chromium speciation, i t was not justifiable to specifically analyze for the hexavalent form of chromium. Hexavalent chromium in s o i l i s very unstable such that lab analysis must be completed within 24 to 48 hours after collection. Specifically, hexavalent chromium, which i s in a higher oxidized state, reduces rapidly to trivalent chromium when removed from the ground. Additionally, chromium i s not a fingerprint chemical of the Site. Therefore, only total chromium was analyzed and speciated for evaluation into the trivalent and hexavalent forms at a 6:1 ratio per the IRIS database (i.e . , a standard accepted default value).

In response to the page 4 footnote comment, the c r i t e r i a on pages 37 and 43, although not contradictory, w i l l be c l a r i f i e d .

9. Commenti "Exposure Assessment?" Pages 6-8 The inappropriate elimination of chemicals from the risk assessment by crude screening techniques i s followed by an inadequate examination of the exposure potential of those chemicals that were retained for analysis.

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Exposure Concentrations This entire discussion, which i s c r i t i c a l for risk assessment, needs to be considerably strengthened, and the calculations need to be re-examined.

The discussion of the means used to calculate the 95th percentile Upper Confidence Limit on the arithmetic mean contaminant concentration (UCL) i s far too sketchy... Because the use of a UCL on concentrations i s an area of considerable s c i e n t i f i c debate, the presentation needs to be c l a r i f i e d whenever calculation of UCLs i s mentioned, and considerably strengthened at pp. 121-122. The authors must jus t i f y the assumption of log normal distributions...

9. Response; The comment in i t s suggests that adequate reference or methodology was not presented to allow duplication of the exposure point concentration. This i s not the case, as both the Gilbert paper and the UCL calculation are referenced in the report. Furthermore, the 95% UCL formula i s provided as are the actual calculations in Appendix A. The use of the UCL formula i s EPA Region I I policy. Regarding distributions, frequency distributions were performed for a number of chemicals and source areas to observe the distribution. A lognormal distribution was observed, rather than assumed, as implied by the OCCCW comment.

10. Exposure Pathways The narrative description of the scenarios provided on pp. 118-121 i s not adequate. Neither do Sections 3.5 and 3.6 provide an explication of the assumed exposure conditions.

I t must also be noted that the residential ingestion exposures consider only incidental ingestion of s o i l per se and not the potential for more significant exposure to contaminated garden vegetation.

10. Response; Regarding assumed conditions of surface s o i l exposure, exposure pathways were developed based on Site v i s i t s and EPA guidance. Both present and potential future-use exposure scenarios for the appropriate receptor populations have been addressed in Section 3.3 and summarized in Table 3-1. The justifications for retention or elimination of receptors and/or exposure routes from quantitative analysis have been presented based on Site observations and historical information. Section 3.5 clearly discusses the intake calculations for exposure scenarios and presents the formulae for each route of exposure (i.e., ingestion, dermal contact, and inhalation). Section 3.6 presents the exposure variables selected for use in the intake equations and the reasoning and sources behind the values. These input values were based on Site-specific conditions, as appropriate.

All formulae and input variables are based on EPA Region I I guidance documents and policy, and'best professional judgement.

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Regarding residential exposure to garden vegetation, EPA guidance directs that this pathway i s only evaluated when Site-specific information i s available to support i t s selection as a pathway of concern. There i s no present-use ingestion scenario, as the Site i s presently not used for residential purposes. I t would be highly speculative to evaluate this as a potential future-use scenario with the lack of site-specific information such as types of fruits and vegetables grown, ingestion rate, fraction ingested from contaminated source, and exposure frequency. In addition, due to limited seasonal gardening in this type of climate, i t i s not expected that the amount of chemical accumulating in garden material would exceed the amount detected in surface s o i l .

11. Exposure Parameters The discussion on pp. 127-133 contains a number of omissions and deviations from EPA guidance ... reliance on the Exposure Factors Handbook (1989) for an estimate of a child's body weight ...to a major error in exposure periods, and an exposure of 30 years should be assumed for residential exposure.

No justification i s provided in the document for the selection of various exposure parameters, and in several cases the particular values selected are inappropriate.

...the parameters employed for estimating residential inhalation exposures are not defensible. Similar deficiencies in selecting and justifying exposure assumptions influence the assessment of exposure to si t e workers, construction workers, and trespassers...

11. Response; Exposure parameters used in this Risk Assessment (including the estimate for a child's body weight and exposure periods) are based on EPA guidance documents which were referenced in the text, or are based on Site-specific information and best professional judgement. For clarity, the text associated with a 30-year exposure w i l l be c l a r i f i e d to note that the exposure i s a combined adult (24-year) and child (6-year) exposure. Discussion of other specific concerns related to selection and justification of exposure assumptions follow.

In order to address the commentor's stated concerns and test these related assumptions, EPA's contractor recalculated risk using more conservative assumptions for those scenarios with the highest previously-calculated risk. For residential inhalation exposure, risk was recalculated for children in the Filtercake Disposal Area (the highest inhalation risk previously calculated) using a more conservative exposure time of 18 hours/day (instead of the 1 hour/day), an inhalation rate of 20 m3/day (i. e . , 0.83 m3/hour), and assuming that the indoor and outdoor dust concentrations are the same. For this scenario, the total risk increased from 2.0E-05 to 9.9E-05 (the actual increase would presumably be even less than calculated since the indoor exposure concentration using the commentor's assumption that the indoor exposure concentration i s

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only 75% of the outdoor exposure concentration). Therefore, the increase i s less than an order of magnitude and the recalculated risk s t i l l f a l l s well within the 10A to 10 s target risk range.

For construction workers, the highest inhalation exposure risk was calculated in the Filtercake Disposal Area (3.3E-06). I f the suspended s o i l concentration was increased as posed in the comment by three times (i . e . , 0.21 ug/m3) and the inhalation rate of 20 m3/workday (i.e. , 3.0 m3/hour) i s utilized, the total risk i s increased within the same order of magnitude from 3.3E-06 to 8.4E-06. Both the originally calculated and recalculated risks f a l l well within the 10A to 10* target risk range.

Trespasser exposure, as discussed in Table 3-1, was determined based on both direct observations made by a Ciba employee and observations made by EPA's contractor during the Site v i s i t . Trespasser exposure as originally calculated was not limited in the risk assessment to 2 hours/week as mistakenly assumed in the comment. The RA used a more conservative assumption of 2 days/week for 6 months of the year (or 52 days/year).

12. Comment: Toxicity Assessment? Page 9 The most serious deficiency of this section of the report i s the failure to adequately address the toxicity of those chemicals for which Slope Factors, Unit Risks, Reference Doses and Reference Concentrations are not available (pp. 149-153).

I t appears that once the authors determined that an Oral Reference Dose (RFD) or Slope Factor was not available for a chemical, neither exposure to, toxicity of, nor risk from that chemical was ever seriously considered... This failure i s particularly notable for lead contamination. Well-defined methods for evaluating risks from lead in so i l have been developed by EPA (such as the Uptake Biokinetic Model) neither was the acceptable blood level for lead established by the Center for Disease Control discussed...

Even for the very limited set of chemicals for which toxicity data are present, the presentation needs improvement. For example, there i s no acknowledgment that EPA employs Unit Risks, rather than Slope Factors, to evaluate carcinogenic risks from inhaled contaminants. "Uncertainty Factors" for RFDs, which are of limited value in assessing these hazard estimates are presented, but the EPA's confidence ratings, which are far more useful, are not, nor are the "Modifying Factors" that are important in the derivation of some RfDs. Lastly, Table 4-3 i s extremely misleading. A l l of the chemicals in the table can affect multiple organ systems. However, with a single exception, the table only presents target organs for the chemical's " c r i t i c a l effect." Reliance on this table would lead to severe misinterpretation of Hazard Indices.

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12. Response: The qualitative discussion of those chemicals not quantitatively evaluated in the RA as presented as Section 4.3 presents brief toxicological profiles as i s standardly accepted. The absence of an Oral Reference Dose or Slope Factor i s an indication that inadequate data currently exist to reasonably evaluate a chemical; in these cases, a qualitative rather than quantitative assessment was performed. In the case of lead, at the time of this RA the Biokinetic Uptake Model for quantitative assessment for lead was under development and the OSWER Lead Directive was used as the guidance for acceptable values of lead in s o i l . Further, despite a wealth of toxicity data, there are no acceptable toxicity values, thus, lead i s qualitatively addressed and a toxicological profile i s provided in Appendix B.

The comment also requested acknowledgement that EPA employs unit risks, rather than slope factors, to evaluate carcinogenic risks from inhaled contaminants. Please note that for inhalation exposures, unit risks are converted to slope factors, and these slope factors are then utilized in risk calculations. The text w i l l be modified to c l a r i f y unit risk discussion.

13. Comment: Risk Characterization; Page 10 ...Risks from chemicals that were eliminated during the i n i t i a l screening are not meaningfully addressed; only those for which a quantitative assessment of risk was made are covered.

...For residents, the calculation of risk i s erroneous...the authors f a i l to examine this combined risk from childhood and adult exposures, but treat them independently...

.. .Risks to residents, construction workers, and trespassers may be seriously underestimated...the assessment of trespasser risks i s limited to the Borrow/Compactor Area. While some areas (e.g. the Production Area) are unlikely to have trespassers, the present assessment i s far too limited, based on site conditions. At a minimum, the authors need to justify the failure to consider such risks for other areas.

Because hexavalent chromium i s a notable contributor to site risks, but no attempt to determine the actual form of on-site chromium was performed, risks may be underestimated...

For that part of the risk characterization that i s included in the draft document, the presentation should be considerably revised ... Table 5-1 — should precede the detailed discussion of Appendix C. ... the equation for calculating carcinogenic risks i s in error. The form shown in the draft can produce risk estimates that are greater than certainty. Instead, the exponential form of the equation should be used. I t i s also misleading to characterize risk estimates as "upper bound" (p. 154). Because the exposure estimates are not upper-bound, but RME, the corresponding risk

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estimates are not upper-bound. Nor i s the Agency li k e l y to agree that an Hazard Quotient or Hazard Index exceeding 1.0 i s the same as an exposure exceeding the threshold for toxicity. Finally, the use of two significant digits in a risk estimate (e.g. 9.7E-07) give a misleading impression of accuracy...

13. Response; Please see the responses to HRI/OCCCW comments 2 and 7 regarding the address of risks from chemicals eliminated during the i n i t i a l screening. Chemicals not having established toxicity values were not eliminated from the report but instead are qualitatively addressed in Section 4.3 of the report, as stated in the report and in EPA's previous response.

Please see the responses to HRI/OCCCW comment 8 regarding the assumptions and calculation of risk for the residential scenario.

Regarding the comment on the use of trespassers only in the Borrow Compactor Area, this was established as the only area of probable entry based on Site's configuration as revealed during Site v i s i t s and confirmed in discussions with Ciba personnel. This Site-specific information i s referenced on page 119 of the draft report as follows:

"Per an October 5, 1992 conversation with a Ciba-Geigy employee [company representative], trespassers are a problem at the north end of the sit e . Guards are stationed at the entrance to the site 7 days/week, 365 days/year. The Borrow/Compactor Area i s the source area closest to the northern border of the s i t e . "

Regarding the repeated comment on hexavalent chromium, please see the response to HRI/OCCCW comment 7.

The commentor's preference for a different organization of the document i s noted and excepted.

For the basis of this response, EPA assumed that the equation questioned i s the linear low-dose cancer risk equation [RISK = CDI x SF], located on page 155 of the Draft RA. This equation used for calculating carcinogenic risks was derived from RAGS (pages 8-6) and i s not in error as noted in the comment. The equation referenced in the comment i s the one-hit equation for high carcinogenic risk levels [RISK = 1 - exp (-CDI x SF) ] . As presented in RAGS, this equation i s to be used when chemical intakes might be high (i.e . , risk above 1E-02). As risks for the Site were not above 1E-02, the appropriate equation was used.

The HRI comment erroneously states that this Risk Assessment characterized calculated risk estimates as "upper bound". An analysis of the components of the equation used to calculate risk [RISK = CDI x SF] reveals that both RME and upper bound values are utilized, where "CDI" equals chronic daily intake values (which are

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RME values), and where "SF" equals slope factor (which are 95th percentile upper bound estimates).

Regarding the commentor's issue with a hazard quotient or hazard index exceeding 1.0 being the same as an exposure exceeding the threshold for toxicity, the reader i s referred to RAGS p. 8-11, which clearly states this to be the case.

Regarding the number of significant figures used in this RA, two figures were consistently used throughout i t s production as i s standardly accepted for EPA Region I I risk assessments.

14. Comment: Uncertainties? Page 11 Sample Data: The discussion of uncertainties in environmental data does not address the fact that very few samples were taken at several source areas.

Alternative Estimates: Table 6-1 on central tendency calculations i s inadequately referenced. The source of each value needs to be specified. In addition, the comparisons that are made are stated erroneously. I t i s not true that adult cancer risks are an order of magnitude lower when average parameter values are used, rather than RME values.

14. Response: Although the sampling frequency in some potential source areas i s relatively low, sampling i s believed to represent surface s o i l chemical contamination in these areas.

Regarding the comment that Table 6-1 on central tendency calculations i s inadequately referenced, the reference for the values in Table 6-1 i s provided on page 181 of the Draft Report.

The text related to comparisons and uncertainties w i l l be modified as appropriate so that statements relating to orders of magnitude are not based on values that have been rounded or on generalizations (e.g., values w i l l be compared in terms of the number of times greater or less than).

15. Comment: Preliminary Remediation Goals? Page 12 This section not only embodies a l l of the errors of the preceding RA, but also introduces additional simplifications that increase the likelihood that the selected PRGs w i l l be inadequate to protect human health. The use of s o i l ingestion as the sole exposure route for calculating PRG for residential use makes no sense, given the contribution of other routes and scenarios to risks, even in this very limited risk assessment. I t should be noted that the approach used in this document stands in direct contradiction to methods proposed by the State of NJ for determining s o i l cleanup levels (e.g. NJ Register, 2/3/1992).

CBA 008 1413

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The equations presented in this section only allow the calculation of s o i l concentration corresponding to individual chemical risks, while the authors note that total risk (for a l l contaminants) should be set at 10*... Using a per-chemical risk level of 10* may lead to PRGs that are not protective of health, when multiple s o i l contaminants are present, as they are at this s i t e . A parallel argument, naturally, applies to PRGs based on hazard indices; the total resultant hazard index should not exceed 1.0, even i f H.Q.s for individual chemicals are less than 1.0.

15. Response; Please note as documented in the responses to a l l previous comments above, that this RA has been performed per EPA guidance and Site-specific determinations made by EPA Region I I . The PRG section of the report was prepared in accordance with current EPA Region I I guidance and EPA RAGS Part B. Although there are differences in Federal and State approach, please note that the New Jersey methods were proposed at the time of report preparation and have yet to be finalized. There i s no statutory requirement to follow proposed regulations; therefore, currently accepted Federal guidance was used.

I t i s true that the equations presented in the PRG Section of the report allow the calculation of s o i l concentration corresponding to individual chemical risks (as derived based on multiple exposure pathways). As exemplified in the response to HRI/OCCCW comment 4, the individual PRGS for five carcinogens were individually calculated to be 1 x 10 s. However, i t follows that the exposure to these five chemicals at the PRG concentration would result in a cumulative risk of 5 x 10"6. The additive equation i s correct since a l l carcinogenic chemicals produce the same effect ( i . e . , cancer). When PRGs are derived for noncarcinogens, the hazard indices may or may not be additive depending on the c r i t i c a l effect. In this RA, only three non-carcinogenic chemicals for residential exposure and two noncarcinogenic chemicals for worker exposure required the derivation of PRGs. Since the target organ for each of these chemicals happens to differ, exposure to these chemicals at the PRG concentration (1.0) would not lik e l y result in an additive effect (i.e . , 3.0 for residents and 2.0 for workers).

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CBA 008 1414