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HEALTH CONSULTATION

Perchlorate Contamination in the Citizens Utilities'
Suburban and Security Park Water Service Areas

AEROJET-GENERAL CORPORATION
RANCHO CORDOVA, SACRAMENTO COUNTY, CALIFORNIA


Table 1.

Suburban System Wells and Perchlorate Sampling Results
Well ID Status of Well Perchlorate Analysis (ppb)
3/24/97 April 5/12/97 6/19/97 7/9/97 8/13/97
Well 23-Woodman   ns ns ns ns ns ns
Well 24-Winchester   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 26-Swansea   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 27-Rockingham   <4.0 ns <4.0 <4.0 <4.0a <4.0
Well 29-Explorer Off-line <4.0 ns ns ns ns ns
Well 30-Gould   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 31-Nut Plains   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 32-Malaga   <4.0a ns <4.0a <4.0a <4.0a <4.0a
Well 33-Mars Way   <4.0 ns ns ns <4.0 <4.0
Well 35-Point Reyes   ns ns ns ns ns ns
Well 37-Moonbeam   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 38-West Loma Linda   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 40-Chettenham   ns ns ns ns ns ns
Well 41-Rogue River   ns ns ns ns ns ns
Well 44-Salmon Falls   ns ns ns ns ns ns
Well 45-Folsom/Bradshaw   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 47-Folsom/Mayhew   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 86-Butterfield   <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 97-Oaken Bucket Threatened by VOC contamination <4.0 ns <4.0 <4.0 <4.0 <4.0
Well 114-Countryside New well on-line 1996 <4.0 ns <4.0 <4.0 <4.0 <4.0

ns= not sampled

<4.0a= perchlorate detected at a concentration <4.0 ppb, but not quantitated

Data taken from References (7, 13-15)



Table 2.

Perchlorate Contamination in the Suburban System- Completed Exposure Pathway for Different Receptor Populations
Receptor Group Pathway Name Source Environmental medium Point of Exposure Route of Exposure Exposed Population Time
Residential Exposure in the Suburban System Aerojet, McDonnell Douglas (?) Intertie with Mather Main Base House Tap Ingestion Adult Residents Past
Worker exposure in the Suburban System Aerojet, McDonnell Douglas (?) Intertie with Mather Main Base Business Tap Ingestion Workers Past
Frequent customer or visitor to a business in the Suburban System Aerojet, McDonnell Douglas (?) Intertie with Mather Main Base Business Tap Ingestion Frequent customer;
Frequent visitor
Past


Table 3. Exposure Factors for Each Receptor Population of the Completed Exposure Pathway in the Suburban System
Receptor Group Pathway Name Exposure Parameter Value
Resident exposure in the Suburban System Ingestion Rate Body Weight Exposure Frequency
Averaging factor
2 liters (8.6 cups)/day 70 kilograms (154 pounds) 7 days/week
52 weeks/year 365 days/year
Worker exposed at a business served by the Suburban System Ingestion Rate Body Weight Exposure Frequency

Averaging Factor
2.0 liters (8.6 cups)/day 70 kilograms (154 pounds) 8 hours/day
5 days/week
50 weeks/year 365 days/year
Frequent customer or visitor to a business in the Suburban System Ingestion Rate Body Weight Exposure Frequency
Averaging Factor
0.24 liter (1 cups)/visit 70 kilograms (154 pounds) 5 visits/week
50 weeks/year 365 days/year

Figure 1. Perchlorate Groundwater Plume in Relation to Aerojet and the Citizens Utilities Suburban System
Figure 1. Perchlorate Groundwater Plume in Relation to Aerojet and the Citizens Utilities Suburban System

Figure 2. Suburban and Security Park Well Locations
Figure 2. Suburban and Security Park Well Locations




ATTACHMENT A

Attachment A was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:

Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch, E-56
1600 Clifton Road NE, Atlanta, Georgia 30333


APPENDIX A. RESPONSE TO COMMENTS FROM SITE TEAM REVIEW

In 1995, EHIB formed a site team to assist us in identifying public health concerns and to oversee what we do during the health assessment process for the Aerojet General site. The site team is composed of community residents, state and federal environmental and health agency staff, Aerojet staff, as well as EHIB staff. Health consultations that are produced as apart of the health assessment process are released for comment to site team prior to them becoming final. We received comments on this health consultation from the Drinking Water Branch of CDHS, U.S. EPA, DTSC, Aerojet, and RWQCB. In this appendix, we will respond to the submitted comments. (Some of the commenters used the Cordova Water System Health Consult as the basis for their comments and asked them to be applied to other health consultations when applicable. Thus, some of the comments make reference to the Cordova Water System and not the Citizens Utilities System, but we included the comment in this health consultation if it seemed applicable.)

COMMENTS RECEIVED FROM THE DRINKING WATER BRANCH OF CDHS

The Drinking Water Branch of CDHS regulates water purveyors in the state, and their comments were minor technical corrections to the numbers we cited in the text. These corrections were made to the original document.

COMMENTS RECEIVED FROM THE U.S ENVIRONMENTAL PROTECTION AGENCY

The EPA offers the following comments for your consideration:

USEPA comment: Page 7 - fourth sentence - the statement that "ammonium perchlorate has relevant physical and chemical characteristics similar to cadmium chloride does not appear to be justified. Although both of these compounds are salts, on dissolution (a necessary step in absorption) perchlorate would become an anion (negative charge) and cadmium would become a cation (positive charge). Therefore, one could conclude on this basis alone that cadmium would not be an appropriate surrogate for perchlorate. Comment applies to all reports but Fair Oaks Water District Report.

CDHS response: According to a highly regarded dermal absorption reference source, the permeability of charged ions is extremely low and membranes appear to be more permeable to cations than anions (40) . Thus, the comparison of perchlorate should not be made between the cation, cadmium, but the anion, chloride, that is found when cadmium chloride is in solution.

USEPA comment: Page 8 - third paragraph - NOAEL term use - The NOAEL is an experimentally derived value that is often used as a basis for the RfD, however, the NOAEL is not regarded by EPA as a value that "would not be expected to be associated with any adverse effect". Rather, this definition better fits the RfD that is derived from a NOAEL after considering uncertainties in the database. Comment applies to all reports but Fair Oaks Water District Report.

CDHS response: We have corrected the use of NOAEL and RfD in the text.

COMMENTS RECEIVED FROM THE CALIFORNIA DEPARTMENT OF TOXIC SUBSTANCES CONTROL

Below are DTSC's comments which may be considered as the documents are finalized.

DTSC comment: In the third paragraph of the consultations, it is stated that the Regional Water Quality Control Board is the lead regulatory agency. While this is correct for some aspects of the project, the lead regulatory agency controlling water district activities is the Department of Health Services, Office of Drinking Water. For matters concerning the Aerojet Superfund Site, the United States Environmental Protection Agency is the lead federal regulatory agency. A co-lead situation exists for certain matters covered under the Aerojet Superfund Site Partial consent Decree (United States District Court, Eastern District of California, Civil Action Nos. CIVS-86-0063-EJG and CIVS-86-0064-EJG).

CDHS response: Being a part of the complex government oversight at this site, we appreciate the clarification to the agency responsibilities. We have tried to rectify this in the text.


COMMENTS RECEIVED FROM AEROJET GENERAL CORPORATION:

Aerojet's comment about the attribution of source of the perchlorate in public water supply wells: Each draft Health Consultation assumes that perchlorate being found in public water supply wells came from the Aerojet Operating Plant, specifically from the reinjection wells associated with the GET facilities. There are numerous locations where such references appear. (See, for example, Arden Cordova Health Consultation at:

Page 6, paragraph 2 and page 22, Table 2.) This assumption is used to project length of exposure and concentrations in the wells over time. The conclusion is made for each well, for every water purveyor, regardless of the well's location, chemical concentrations or differing hydrogeological conditions.

We are aware of no detailed evaluation of sources, groundwater conditions and groundwater and contaminant movement undertaken by DHS or any other agency that would support statements in the DHS Consultations that attempt to link perchlorate in a well to an upgradient source, and it does not appear necessary for DHS to ascribe a source to reach its conclusions. The Health Consultations should identify that potential sources of perchlorate include the Aerojet Operating Plant, Purity Oil site, and the McDonnell Douglas (MDC) Site. DHS should not assert that the only source of the perchlorate is the GET facility recharge wells on the Aerojet Operating Plant. Neither should the period of operation of the GET wells form the basis for assumptions of exposure of potential receptors. As the Health Consultations discuss potential sources, it should discuss the various uses of perchlorate, other than in rocket motor manufacturing, such as the use of perchlorate in pyrotechnics (fireworks), explosives and other industrial activities. It should also note that perchloric acid, which is used in various industrial activities, including metal-plating, in laboratories, and in other operations, when released can result in the formation of perchlorate and its movement into soils and groundwater.

Aerojet believes that there have been no health impacts associated with any exposure to perchlorate in the water supply. If the Health Consultations seek to discuss long term impact by assuming exposure for some period (e.g., 10 years), they can do so without assigning a source, but simply by positing the potential for such exposure (without reference to a source) and developing an exposure assessment.

CDHS response: These health consultations are written as a part of CDHS's public health review of the impact of the Aerojet General site. Thus, the documents are written in respect to Aerojet General and not to other sites or facilities. We do recognize that perchlorate may have also gotten into the groundwater from sources other than Aerojet and that is why in last sentence of the third paragraph on page 1, we refer to the RWQCB's investigation of "other sources of the perchlorate such as the McDonnell Douglas (now Boeing) and Purity Oil Sales sites."

Aerojet's comment about the toxicology: Aerojet recommends modifications to the discussion on toxicology. We are concerned that the draft consultations do not provide sufficient information about what is known about perchlorate toxicity (thyroid function) and end up, unintentionally, providing a less balanced presentation of the potential for impact and risk. For example, we believe there should be more discussion related to the past use of perchlorate in the treatment of Graves patients and its current use in Europe at very high doses without ill effects. Similarly, we recommend the inclusion of a statement that the mechanism of perchlorate on the thyroid as well as basic thyroid functions are well understood and we believe that the discussion as to exposure associated with children may lead to unnecessary concern and should be changed. Finally, we believe that there ought to be mention of the ongoing studies being conducted at the direction of the Air Force.

CDHS response: We did provide more information in the toxicology section. For instance, we have added more information about past and current uses of perchlorate and what is known and not known about toxicity to the developing fetus and young child. We did have a reference in the recommendations section about the on-going studies by the Air Force and the Perchlorate Study Group and we have added a sentence in the toxicology section referring the reader to the recommendations section for more information about these studies.

Aerojet's comment about the water system operations: The draft Health Consultations, especially in the background sections, contain statements of fact as to the manner of well and system operation of each water entity over time, including detail on well construction and operation in tables. Aerojet has not had an opportunity to complete an evaluation of the accuracy of such statements. We further note that the factual statements generally do not seem to impact the exposure assessment, as the exposure assessment is based upon an assumed concentration that is not generally associated with the specifics of well interties or well operation. We would recommend the Health Consultations state that the water system information is based on current understanding unless DHS has had the opportunity to perform a detailed evaluation of the information.

CDHS response: In each health consultation, we cite the CDHS reports or other reports from which we gained this information. We refer Aerojet to those documents if Aerojet would like to evaluate the accuracy of such statements. We do think it is important to describe for the reader the basic structure of a particular water system; on the other hand, we don't want to add more information then is necessary. We hope that the amount of information we have provided will allow a Citizen Utility System customer to more easily understand that the limited extent of perchlorate contamination that has occurred in the system. By describing the water system information in this document, it also helps us to decide where we might consider follow-up activities, like an exposure dose reconstruction.

Aerojet's comment about the Exposure Conclusions: The draft Health Consultations are based upon a set of assumptions, including assumed receptors, exposure rates, and concentrations. From these assumptions, an assumed dose is calculated and then compared to the provisional RfD. We believe that the Health Consultations should carefully describe each assumption upon which the Health Consultations were based, and clarify that these assumptions have not been fully evaluated. For example, a preliminary assessment of proximity to a well is used to determine the type of "receptor" (e.g., resident, worker), but the exposure does not assume any dilution of water from that well with water from any other well.

CDHS response: All of the exposure parameters are listed in the table and a Citizen Utility System user can look at these exposure parameters and apply them to their own situation. Thus it does not seem necessary to explain distributions of exposure parameters or in any other way describe each assumption.

With these general comments identified, we now progress to the specifics. We use the Arden Cordova Health Consultation as the template for our comments, and emphasize that typically the same issue exists in the other draft Health Consultations.

Aerojet comment: Page 1, Paragraph 2 and Throughout: The term "perchlorate contamination" is subject to misinterpretation and references should be to "water containing perchlorate" or like phrase.

CDHS's response: In Webster's New Collegiate Dictionary, it says "contaminate" means "to make impure or unclean". Perchlorate is not typically found in groundwater, as would be the case with certain chemicals like arsenic or sulfates which are naturally occurring in groundwater. Thus it does seem appropriate to describe the "contamination" of groundwater by a chemical such as perchlorate. Likewise, it may be appropriate to describe "water containing arsenic" if you are describing water which contains unusually high levels of arsenic due to natural reasons and arsenic-contaminated water if higher levels than normal may be due to non-natural reasons.

Aerojet comment: Page 1, Paragraph 3: The description of Aerojet operations and Cordova operations has been taken from earlier documents. Aerojet has historically pointed out the inaccuracies in the statements and rather than do so again we recommend, at a minimum, elimination of a reference to Cordova Chemical Company, because we do not believe it used perchlorate. We also recommend an elimination of the reference to the deep injection wells, because they are not relevant to the issue and can result in confusion when there is later discussion about recharge or reinjection wells associated with the GET facilities, which are different wells.

CDHS response: In the background paragraph, we are describing the lay of the land regarding the general site issues and thus we did not directly suggest that Cordova Chemical did use perchlorate, but rather this company was a part of the history of the site. Since perchlorate is reinjected at the site boundary as a part of the GET operations, we do not agree that reference to these should be eliminated.

Aerojet comment: Page 1, Paragraph 3: Delete "property" after "Aerojet's."

CDHS response: This incorrect grammar has been corrected in the text.

Aerojet comment: Page 1, Paragraph 3: Aerojet is not reinjecting treated water at the site's northern boundary.

CDHS response: This has been changed in the text.

Aerojet comment: Page 1, Paragraph 3: The Regional Water Quality Control Board (RB) is not the lead Agency; DTSC, USEPA and RB together provide oversight pursuant to the Partial Consent Decree.

CDHS response: The description of the lead agency/agencies was changed in the text.

Aerojet comment: Page 3, Paragraph 1: The discussion as to detection of perchlorate ought to be rewritten. Prior to the summer of 1996, Aerojet's laboratory used an ion specific electrode method. In 1997 Aerojet's laboratory did not use a different analytical method for perchlorate analysis to obtain the detection limit of 35 ppb but rather refined or improved the sensitivity of the existing ion chromatography method. In addition, it is accurate to say the "method" detection limit.

CDHS response: Based on this comment and a similar comment by other reviewers, the description of the analytical method was revised in the text.

Aerojet comment: Page 6, Paragraph 1: See the discussion above regarding the history of perchlorate sampling. It is not accurate to say that the analytical method Aerojet had been using was not sensitive to adequately assess the migration of perchlorate. It would be more accurate to state that Aerojet's historical analytical method's practical quantitation limit (PQL) for perchlorate was 400 ppb. As stated previously, there was no "alternative analytical method" used but the existing method was refined or improved and the PQL lowered.

CDHS response: According to the third sentence of the comment, the older method was indeed not sensitive enough to detect the perchlorate contamination. We did, however, revise the text to reflect the last two sentences of the comment.

Aerojet comment: Page 8, Second Full Paragraph and Page 9, Second Full Paragraph: The three well contribution scenarios identified in the paragraph on page 8 and the those identified on page 9 are not referenced the same. On page 8 scenario 1 is Well #1 delivering 100% of the water; on page 9 Well #1 is referenced as the second scenario. Page 8 references Well #2 in the lead as the worst case scenario but page 9, paragraph three states that noncancer health effects would not have occurred when Well #2 was the lead well. It is difficult to understand which exposure calculations relate to which well because of the inconsistent references.

CDHS response: The text on page 9 was incorrect and was corrected.

Aerojet comment: Page 10, Last Full Paragraph, First Line and Page 11, First Paragraph: As stated above, does the author mean Well #1 or #2?

CDHS response: The text should have read well #2, and this was corrected.

Aerojet comment: Page 8, Continuing Paragraph and following: We refer you to the general comments on toxicology above. The draft Health Consultations would be better balanced if there was more discussion related to the use of perchlorate in the treatment of Graves patients and its current use in Europe at very high doses without ill effects. A strong statement that stresses how unlikely it would be to suffer any of these side effects at the levels addressed in the health consultation would be appropriate. In particular, the draft Health Consultations ought to point out that perchlorate has been used successfully and without incident in a fairly large patient population and with a very small number of reports of aplastic anemia even at the very high therapeutic concentrations A statement that the mechanism of perchlorate on the thyroid as well as basic thyroid functions are well understood would help to clarify the presentation. While the provisional RfD is stated as a level in drinking water at 18 ppb, the remaining levels discussed in the document are stated in terms of mg/kg/day. A direct comparison of those doses with the LOAEL/NOAEL and the provisional RfD in the same unit of PPB's would be very useful to give perspective to the dose issue.

CDHS response: As noted on the response to a General Comment from Aerojet, we did provide more information in the toxicology section. For instance, we have added more information about past and current pharmacological uses of perchlorate and what is known and not known about toxicity to the developing fetus and child. We also added a statement in the toxicological section that equates the dose to the drinking water concentrations.

Aerojet comment: Page 8, Continuing and Paragraph 1: The discussion of animal studies should be modified. There are animal studies where toxicologists have interpreted a NOAEL [(e.g. Mannisto (1970) and Caldwell (1996)]. As to the reference to children, in two places there is a discussion that suggests that nothing can be said about children. Aerojet is concerned that the reference might leave the reader with the impression that toxicologists do not consider impact to the thyroid as the focus of the evaluation or it might cause the reader to think that toxicologists view the child's thyroid as not understood. It would be more accurate to state that the mechanism of perchlorate intake on the thyroid is understood and that in evaluating the dose, one must evaluate the possibility that the child may have less iodine reserve which must be considered in evaluating how the child's thyroid compensates in comparison to an adult thyroid. However, any reference should also include the fact that all new-borns are routinely tested for thyroid hormone. levels. Aerojet believes that it would be inappropriate for the Health Consultations to be construed as indicating that children are at risk at the provisional RFD or that exposure to the higher concentrations before well shut down would be associated with any health impact.

While it appears in the text, we believe there should be a clear reference both in the toxicology discussion and in the exposure section, that perchlorate is discharged from the body very quickly and that one would not expect to see any continuing impact on the thyroid once the exposure ends.

CDHS response: See response to previous comment.

Aerojet comment: Page 8, Paragraph 3: Regarding the discussion of safety factors, various toxicologists believe that the hypothyroid individual would not be a sensitive subpopulation. Also, the Health Consultations should recognize that the sensitive subpopulation factor is already being accounted for with respect to DHS comments on exposure of children.

CDHS response: Comment noted.

Aerojet comment: Page 9, Paragraph 3: See discussion above on children. We believe that the two locations of discussion on children should be combined in one location.

CDHS response: Comment noted.

Aerojet comment: Page 9, Paragraph 4: Exposure discussion includes the volume of tap water consumed per day in liters and perhaps the inclusion of a unit like the number of 8 oz. glasses per day would benefit the average reader, or public citizen. This could be included in the text and in the Table.

CDHS response: We have added this information to the text and table.

Aerojet comment: Page 9, Paragraph 4 and Following: There is the repeated statement that the estimated doses for [identified type of exposure] from well # [identified well number] exceeded the provisional RfD range and a conclusion stating "health effects may have occurred." The phrase "may have occurred" could be misinterpreted as it may suggest a higher level of risk than existed, given the low levels of perchlorate found in relation to the provisional NOAEL described. Given the uncertainty factors associated with the provisional RfD, Aerojet believes that it would be more appropriate for the Consultations simply to conclude that the level was over the RFD and then follow with a conclusion as to the unlikely nature of any health impact. If DHS does continue to want to use "may have occurred" language, then the "may have occurred" language should be clarified when presented by referring to the key assumptions, the exposure assessment, etc., (e.g., the number of 8 ounce glasses of tap water needed to be consumed). The health consultations should also stress that there is a significant range between the provisional RfD of 18 ppb and the NOAEL level translated to 4900 ppb (assuming a NOAEL of .1 4 mg/kg/day and a 70 kilogram male drinking 2 liters per day). It would also be useful either to change the reference of "uncertainty" factors to "safety" factors or use the term uncertainty (safety) factors" for the benefit of the reader.

CDHS response: Comment noted.

Aerojet comment: Page 12, Paragraph 2: See the above comments regarding speculation as to source.

CDHS response: See previous response to similar comments.

Aerojet comment: Page 12, Paragraph 4: There are a number of paragraphs that repeat statements made in the exposure section. See discussion above (page 9) relative to language about dose above the RfD. Aerojet does not believe that it is appropriate to conclude that there "may" have been a "health hazard." If language as to hazard is described, it should not be separated from the DHS assumptions about exposure nor should it be stated without the conclusion as to the unlikeliness of any impact. Aerojet further notes that the various Consultations do not always use the same language on "health hazard," and the differences in language do not appear justified (e.g., see Mather page 12 paragraph 3).

CDHS response: Comment noted.

Aerojet comment: Page 13, Bullets #1 and 2 (Actions Planned): Aerojet believes that any dose reconstruction investigation should await completion of further investigations and should not assume sources. See general discussion above.

CDHS response: Comment noted.

Aerojet comment: Aerojet believes that any health statistics review of newborn thyroid testing raises significant issues regarding appropriate protocols for such study, timing of such study in light of ongoing animal studies, appropriateness of such a study in Sacramento and presumes confidence in the "dose reconstruction" exposure assessments. Aerojet requests the opportunity to review draft DHS protocols for any such study.

CDHS response: We will try to include an outside review of the study protocol.

Aerojet comment: Page 13, Bullet #3 and Page 14, Bullet #4: The reference should be to the Perchlorate Study Group, not Perchlorate Work Group.

CDHS response: This has been corrected in the text.

Aerojet comment: Page 14, Bullet #2: The use of the word "safe" is inappropriate, Reference should be to the provisional RfD.

CDHS response: We have modified the text so as to remove the word "safe".

Aerojet comment: References, No. 17. The citation to the authors should be corrected.

CDHS response: This citation has been corrected.

Aerojet comment on Table 1: We have not had adequate opportunity to evaluate the descriptions of all of the wells and the well system. We note that the comments in the Table are based upon assumptions made as discussed in the text and our comments apply.

CDHS response: Comment noted.

Aerojet comment on Table 2: We believe a "source" category for this Table is inappropriate. Please see general comment above on sources.

CDHS response: Comment noted.

COMMENTS FROM THE CENTRAL VALLEY REGIONAL WATER QUALITY CONTROL BOARD

Regional Board staffs comments on the documents are supplied below.

RWQCB General Comment: We recommend that the use of the term "contaminated" be selectively used. Contaminated should be used when the water represents a hazard to the public health. In the case of perchlorate, "contaminated" should not be used when discussing concentrations less than 18 ppb. It is even unclear whether the term should be applied to those concentrations that are currently found in some of the groundwater supply wells (up to 300 ppb). Instead of saying "perchlorate-contaminated water", we would recommend saying "water containing perchlorate".

CDHS response: As was stated under a similar comment raised by Aerojet, in Webster's New Collegiate Dictionary, it says "contaminate" means "to make impure or unclean". Perchlorate is not typically found in groundwater, as would be the case with certain chemicals like arsenic or sulfates which are naturally occurring in groundwater. Thus it does seem appropriate to describe the "contamination" of groundwater by a chemical such as perchlorate. Likewise, it may be appropriate to describe "water containing arsenic" if you are describing water which contains unusually high levels of arsenic due to natural reasons and arsenic-contaminated water if higher levels than normal may be due to non-natural reasons.

RWQCB General Comment: There is a paragraph in each of the health consultations which discusses the "reporting level to the RWQCB" of 400 ppb and a change in method which allowed for a detection level of 35 ppb. In the early 1990's, up until around 1995/96, Aerojet was using a ionspecific electrode to measure perchlorate concentrations in water with a detection level of 400-500 ppb. Aerojet then developed an alternate method using a GC which provided a detection level of 35 ppb and a reporting level of 400 ppb. This method was then used by Aerojet in all work required under the Partial-Consent Decree. In early 1996 RWQCB staff requested Aerojet to report all concentrations between the detection level (35 ppb) and reporting level (400 ppb) as trace. Aerojet was then able to lower their PQL to 100 ppb, while maintaining their detection level at 35 ppb. No method changes were made to get to the lower reporting level. It was in February 1996 that the concentrations in the off-site water supply wells were first reported.

CDHS response: Based on this comment and comments by others, the text was revised.

RWQCB General Comment: When discussing the nitrate levels, make sure that the values reported are designated as milligrams per liter as nitrate, or milligrams per liter as nitrogen. The MCL for nitrate should be expressed in the same units. There are two values for the MCL used in the five health consultations, 20 and 45 mg/l. A single value for the MCL should be used.

CDHS response: We have corrected this in the text.

RWQCB General Comment: We will not supply comments on the toxicological issues presented in the documents. We will rely on the experts at the Department of Health Services to make those evaluations.

CDHS response: Comment noted.

RWQCB comment: Page 2, paragraph 5. The value for the MCL for nitrate should be supplied to allow the reader to determine the significance of the values presented.

CDHS response: We have added the MCL as a reference in the text.

RWQCB comment: Page 13, second paragraph. Insert a "the" after "actions" in the second line.

CDHS response: There was a grammatical problem in the sentence, which we have corrected.

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