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HEALTH CONSULTATION

Vapor Intrusion Potential at Properties Adjacent to Former Risdon Corporation Facility

FORMER RISDON CORPORATION FACILITY
(a/k/a RISDON CORPORATION)
DANBURY, FAIRFIELD COUNTY, CONNECTICUT


The conclusions and recommendations in this health consultation are based on the data and information made available to the Connecticut Department of Public Health and the Agency for Toxic Substances and Disease Registry. The Connecticut Department of Public Health and the Agency for Toxic Substances and Disease Registry will review additional information when received. The review of additional data could change the conclusions and recommendationslisted in this document.


BACKGROUND AND STATEMENT OF ISSUE

The Connecticut Department of Public Health (CT DPH) was asked by the U.S. Environmental Protection Agency (EPA) to evaluate the public health implications of volatile organic compounds (VOCs) off gassing from contaminated groundwater near the Risdon Corporation and migrating into buildings in a residential/commercial neighborhood of Danbury, Connecticut. The data evaluated by CT DPH is from a groundwater and soil gas study conducted by Woodward & Curran, a contractor for the Risdon Company. The study involved five properties (2 with residences and 3 with commercial buildings) in a Danbury neighborhood. The five properties are located near the intersections of Old Newtown Road, Broad Street , and Augusta Drive, and immediately northwest of the former Risdon Corporation facility. One residence is on Broad Street, and the other is on Old Newtown Road, while the three commercial buildings are located on Old Newtown Road, and Augusta Drive. The residential properties are located between the Risdon facility and a small river. A map of the area, with sample locations shown, is included as Attachment A. There are no private drinking water wells on the Risdon site or at any of the nearby downgradient properties.

The five sites were chosen for study because they are hydraulically down-gradient from theRisdon facility. Soil gas and groundwater sampling were conducted on these properties inDecember of 2001. Groundwater data is also available from nearby monitoring wells on theRisdon property. Groundwater below the Risdon site has been monitored for organiccontaminants since the early 1980's. This "older groundwater data" is useful for constructing anupper-end (i.e., "worst case") scenario for exposure to solvents originating at the Risdon site. Nearby monitoring wells and representative sample dates were chosen with this purpose in mind.

Risdon began operations on Old Newtown Road in 1956. The company's manufacturing processincluded electroplating (nickel, brass, chrome, silver, cyanide); stripping (nitric acid, methylenechloride, formic acid); painting (lacquers, enamels); buffing and polishing. Wastes generated atthe site include 1,1,1-trichloroethane (TCA) and trichloroethylene (TCE), lacquers, thinners,enamels, petroleum distillates, methylene chloride, formic acid, degreasing filters, silver cyanidesolution, nitric acid, and metal hydroxide sludge. The chlorinated solvents, TCA and TCE havecontaminated groundwater at and near the Risdon facility. TCE and TCA breakdown products,1,2-dichloroethene (1,2-DCE), 1,1-dichlorethene (1,1-DCE) & vinyl chloride, have also beenfound in groundwater.

Description of adjacent properties

The residential properties both contain a house and a detached garage. On Broad Street , thesingle-family residence (built 1895) is one and one-half stories tall, and contains approximately1200 square feet of floor space. On Old Newtown Road, the two-family residence (built about1783) is two stories tall, and contains approximately 2100 square feet of floor space. Bothresidences are built on stone foundations and the basements are unfinished. Both garages aresingle-story. Although an exact count was not available, the two residences appear to be able tohouse between eight and twelve individuals.

The three commercial buildings are built on concrete slabs at grade. One building on OldNewtown Road contains a 20,000 square-foot two-story steel framed building built in 1989. Another, 95,000 square-foot, single-story, building was built in 1956. The property on AugustaDr. contains a single story building. Metal plating operations have been conducted at this sitesince the building was constructed in 1963. Because these commercial buildings were built on aconcrete slab, the potential for vapor intrusion is low. CT DPH is therefore less concerned aboutthe potential for vapor intrusion at these addresses. Therefore, this Consultation does not include estimates of indoor air concentrations for the adjacent commercial properties.


DISCUSSION

Assessment methodology and results

At each sampling location, a soil gas probe (1) was inserted into the ground to a maximum depth of six feet. Soil gas samples were collected outside the building, as close to the foundation aspossible. Initially, soil gas samples were analyzed onsite using a field gas chromatograph (GC). A soil gas sample was then collected using a SUMMA canister and was analyzed in thelaboratory using a gas chromatograph mass spectrometer (GC/MS). Groundwater was sampledat or near the adjacent properties from monitoring wells screened at or below the water table(MW prefix) or from Geoprobe samples (GW prefix).

The following target analytes with the greatest potential to volatilize from groundwater intoindoor air, were identified in groundwater or soil gas:

  1. 1,1-Dichloroethene
  2. Vinyl Chloride
  3. Trichloroethene
  4. Benzene
  5. 1,1,1-Trichloroethane
  6. Toluene
  7. Freon 12
  8. Freon 113
  9. Chloroform
  10. 1,1,1,1-Tetrachloroethane
  11. Xylene
  12. MTBE
  13. cis- 1,2-Dichloroethene
  14. 1,1-Dichloroethane
  15. Methylene Chloride
  16. Ethylbenzene
  17. 4-Ethyltoluene
  18. Trimethylbenzene

CT DPH uses comparison values to evaluate the public health implications of environmentalcontamination. The chronic comparison values are taken from the Connecticut Department ofEnvironmental Protection's (CT DEP) Remediation Standards for residential exposure (RSR). These standards are accepted as indicators of a level of exposure considered safe for thirty yearsof nearly continuous exposure (See Tables 1 & 2; Chronic Comparison Value). Intermediateduration comparison values are also included in Tables 1 & 2. These values are greater than thechronic comparison values because they are derived from ATSDR's intermediate duration (15-365 days) comparison values. If estimated indoor air concentrations are below the comparisonvalues, then there is little cause for concern. On the other hand, if indoor air concentrationsexceed the comparison values, then further analysis is needed.

Tables 1 & 2 show the comparison values and summarize the sampling results for soil gas andgroundwater taken at or near the residences. Maximum concentrations are included along withan estimate of the indoor air concentration. Maximum, rather than average, concentrations areoften used in Health Consultations because they delineate the upper-end or "worst case"exposure scenario. The maximum indoor air concentration was estimated from soil gas data bymultiplying the maximum soil gas concentration by 0.01 (the attenuation factor). An estimatedone in this manner is expected to error on the high-side, indicating that the actual concentrationis not likely to be greater than that shown (EPA, 2001). Estimates of maximum indoor airconcentration are compared to a health-based benchmark. In this instance, the benchmark is the"target air concentration" taken from CT DEP's RSRs. Groundwater data was compared to CTDEP's residential groundwater volatilization criteria (GWVC), listed in the RSRs. GWVCs areconservative estimates derived from the target air concentrations. The Health-protectivecomparison values and the number of samples above this concentration are also shown. Contaminants detected below comparison values are not included in Tables 1 & 2.

In some instances, the detection limit of the assay (i.e., the lowest detectable concentration) wasgreater than the comparison value. This is indicated in Tables 1 & 2 by a range (e.g., Table 1,Part A, for 1,1-DCE). A range indicates that, for some samples, the detection limit of the assaywas greater than the comparison value multiplied by the attenuation factor (for soil gas data). When this occurs, it is not possible to use the sample to determine if the estimate of indoor airconcentration is below the comparison value. For the example in Table 1, (a range of 1-6) therewas one sample in excess of, and five samples with detection limits greater than the equivalent ofthe comparison value. It is therefore possible that the comparison value-equivalent concentrationwas exceeded in six out of seven samples. The analogous is true for sample results fromgroundwater data.

The data summarized in this Health Consultation suggests that concentrations of trichloroetheneand 1,1-dichlorethene may be found in excess of health-protective comparison values at the twonearby residences with basements. It is also possible, based on limited evidence of groundwatercontamination, that vinyl chloride is intruding the indoor air space. Past data would indicate thatthe vapor intrusion pathway was significant for at least ten years, but the duration of exposurecould extend back 45 years, to when the Risdon facility was opened. The fact that both of thesehomes have stone foundations indicates that the rate of intrusion could be relatively high.

Broad Street, residential

Analysis of groundwater and soil gas data from sample sites in the vicinity of the Broad Streetresidence indicates that indoor air concentrations could exceed comparison values. Of theVOC's tested, TCE and 1,1-DCE were sometimes found at levels high enough to suggest that avapor intrusion exposure pathway may be significant. Though benzene was reported in two soilgas samples, there is no evidence from nearby wells to indicate that it is a groundwatercontaminant. Though vinyl chloride was below detection limits in the five soil gas samplestested, the detection limits for these were greater than the comparison value equivalentconcentration (data not shown). A comparison of recent and older groundwater data indicatesthat the vapor intrusion pathway may have been present for at least ten years. Quantitatively, theolder data suggests that air concentrations would have been higher in the past. A qualitativecomparison indicates that 1,1,1-trichloroethane exposures may have decreased to levels belowthe comparison value. Results for soil gas, recent groundwater, and older groundwater testingare shown in Table 1; parts A, B, and C, respectively.

Old Newtown Road, residential

Analysis of groundwater and soil gas data from sample sites in the vicinity of the Old NewtownRoad residence indicates that indoor air concentrations could exceed comparison values. OfVOC's tested, TCE and 1,1-DCE were sometimes found at levels high enough to suggest that avapor intrusion exposure pathway may be significant. Though vinyl chloride was belowdetection limits in four of five groundwater samples tested, the detection limits were greater thanthe comparison value equivalent concentration in these four samples. A comparison of recentand older groundwater data indicates that the vapor intrusion pathway may have been present forat least ten years. Quantitatively, the older data suggests that air concentrations would have been higher in the past. Results for soil gas, recent groundwater, and older groundwater testing are shown in Table 2; parts A, B, and C, respectively.

Part A: Soil gas data.

Table 1.

Data and comparison values in the vicinity of the Broad Street residence.
Contaminant Maximum Soil Gas (ppbv) Predicted Upper Bound Indoors (ppbv)1 Samples Above Chronic Comparison Value (#) 2 Samples Analyzed (#) Chronic Comparison Value
(ppbv in air)5
Intermediate Duration Comparison Value (ppbv in air)6
trichloroethene 140 1.40 1 8 0.915 100
1,1-dichloroethene 5.8 0.06 1-6 7 0.012 20

Part B: Recent groundwater data

Contaminant Groundwater Maximum on/near Residence (ppb)3 Samples Above Chronic Comparison Value (#) 2 Samples Analyzed (#) Chronic Comparison Value
(ppb in water)5
Intermediate Duration Comparison Value (ppb in water)6
trichloroethene 1900 2 6 219 24000
1,1-dichloroethene 370 4 6 1.1 2328

Part C: Older groundwater data..

Contaminant Groundwater Maximum on/near Residence (ppb)4 Samples Above Chronic Comparison Value (#) 2 Samples Analyzed (#) Chronic Comparison Value
(ppb in water)5
Intermediate Duration Comparison Value (ppb in water)6
1,1,1-trichloroethane 53000 3 4 20392 75920
trichloroethene 4500 3 4 219 24000
1,1-dichloroethene 4300 4 4 1.1 2328

1 An attenuation factor of .01 is considered a reasonable upper bound for indoor air/soil gas concentration ratio ( EPA, 2001)
2 A sample is counted in this column if the estimated concentration is greater than the comparison value. A range indicates that some samples had detection limits below the comparison value. The high number in the range is derived from including the detection limit in the analysis (see text).
3 Nearby wells include MW11, MW5, MW10, & MW11 (Risdon); 3/2001 & 9/2001 data
4 Near site wells include MW11, MW5, MW10, & MW11 (Risdon); 11/4/88 & 10/29/90 data
5 Chronic comparison values are the CT RSR's (residential Target Indoor Air Concentrations, or the residential Groundwater Volatilization Criteria).
6 Intermediate duration comparison values are from ATSDR's list of air comparison values. The water-equivalent concentration (Groundwater Volatilization Criteria) was calculated from the intermediate duration air comparison value by the method outlined in the CT RSRs.


Table 2: Data and comparison values in the vicinity of the Old Newtown Road residence.

Part A: Soil gas data

Contaminant Maximum soil gas (ppbv) Predicted Upper Bound Indoors (ppbv)1 Samples above Chronic Comparison value (#) 2 Samples Analyzed (#) Chronic Comparison Value
(ppbv in air)5
Intermediate Duration Comparison Value (ppbv in air)6
trichloroethene 280 2.8 2 5 0.915 100
1,1-dichloroethene 86 0.86 4-5 5 0.012 20

Part B: Recent groundwater data.

Contaminant Groundwater Maximum on/near Residence (ppb)3 Samples Above Chronic Comparison Value 2 Samples Analyzed (#) Chronic Comparison Value
(ppb in water)5
Intermediate Duration Comparison Value (ppb in water)6
trichloroethene 2700 6 8 219 24000
1,1-dichloroethene 98 6-7 8 1.1 2328
Vinyl Chloride 5 1-5 5 2 1287

Part C: Older groundwater data

Contaminant Groundwater Maximum on/near Residence (ppb)4 Samples Above Chronic Comparison Value (#) 2 Samples Analyzed (#) Chronic Comparison Value
(ppb in water)5
Intermediate Duration Comparison Value (ppb in water)6
trichloroethene 12000 2 4 219 24000
1,1-dichloroethene 248 2-3 4 1.1 2328
vinyl chloride 83 1-4 4 2 1287

1 An attenuation factor of .01 is considered a reasonable upper bound for indoor air/soil gas concentration ratio ( EPA, 2001)
2 A sample is counted in this column if the estimated concentration is greater than the comparison value. A range indicates that some samples had detection limits below the comparison value. The high number in the range is derived from including the detection limit in the analysis (see text).
3 Nearby wells include MW14,& MW15 (Risdon); 3/2001 & 9/2001 data
4 Near site wells include MW14,& MW15 (Risdon); 4/14/92, 8/31/92, & 7/13/92 data
5 Chronic comparison values are the CT RSR's (residential Target Air Concentrations, or residential Groundwater Volatilization Criteria).
6 Intermediate duration comparison values are from ATSDR's list of air comparison values. The water-equivalent concentration (Groundwater Volatilization Criteria) was calculated from the intermediate duration air comparison value by the method outlined in the CT RSRs.

Exposure pathways

As both residential addresses are served by public water, there is no potential for TCE or 1,1-DCE exposure from drinking or other domestic water uses. The primary exposure pathway therefore is soil gas. Though exposure via direct volatilization can not be ruled out, it is apparent that flooding of basements with groundwater is only a seasonal occurrence. Groundwater level measurements conducted in September 2001 indicate that groundwater was found about nine feet below grade in the vicinity of the Old Newtown Road residence, and about 13 feet below grade in the vicinity of the Broad Street residence. Estimating that the basements at these two sites are excavated to six feet below grade, groundwater intrusion potential seems low at the Broad Street residence, but flooding may occur seasonally at the Old Newtown Road residence. Even so, when averaged over the year, the soil gas pathway should be the primary exposure pathway.

Groundwater at the Risdon facility has been sampled at numerous times and locations in the past.(CT DPH has copies of groundwater data back to 1983.) In order to estimate exposure (durationand concentration), CT DPH examined the database for the groundwater monitoring wells nearthe adjacent properties (e.g., MW2, MW5, MW10, MW11, MW14, MW 15). From this data set,CT DPH selected sample dates that were older, and wells that were more contaminated, than theaverage (see Tables 1 & 2). This approach results in an upper-end estimate of exposure, which isneeded for constructing a "worst case" type of exposure scenario.

Public Health Implications of present and past exposures

Analysis of recent groundwater and soil gas data from sample sites in the vicinity of the tworesidences indicates that indoor air concentrations could exceed comparison values. Of VOC'stested, TCE, 1,1-DCE, and vinyl chloride were sometimes found at levels high enough to suggestthat a vapor intrusion exposure pathway may be significant. Though benzene was found above itscomparison value in one of three soil gas samples, there is no evidence from nearby wells toindicate that it is a groundwater contaminant. This suggests that benzene is from sources otherthan groundwater. Though vinyl chloride was below detection limits in most samples tested, thedetection limits were less than the comparison value.

A comparison of recent and older groundwater data indicates that the vapor intrusion pathwaymay have been present for at least ten years. An upper limit to exposure duration would be 45years (i.e., from the year operations began at the Risdon facility). As groundwater data was notavailable from beyond approximately ten years ago, it is not possible to determine exposureduration with greater precision. The older groundwater data suggests that indoor airconcentrations may have been greater in the past, and that 1,1,1-trichloroethane and vinyl chloridemay have been present in indoor air at concentrations above the comparison values.

From results in Tables 1 & 2, it is apparent that 1,1-DCE is the primary driver of risk. 1,1-DCEhas been shown to induce tumors in laboratory mice after long-term inhalation exposure. In 1998,the US Environmental Protection Agency (EPA) used the results of the mouse study as the basisto list 1,1-DCE as a possible human carcinogen. However, EPA is now re-reviewing thisclassification, and the status of 1,1-DCE's listing is likely to change in the near future. Draftreview documents from EPA indicate that, EPA's Integrated Risk Information System (IRIS) willno longer support the basis for quantifying cancer risk from 1,1-DCE exposure (2). CT DPH hasthus decided not to do a quantitative risk assessment of 1,1-DCE exposure at this time.

Site visit & community concerns

On February 21, 2002, representatives from CT DPH, ATSDR, EPA, Woodward & Curran(Risdon's Contractor), and the Danbury Health Department visited the area adjacent to the Risdonfacility. Purposes of this visit were to inform public health officials of the goals of this HealthConsultation, and to discuss any relevant community concerns. During the visit, one owner of anadjacent property approached the group to ask for an explanation of the group's purpose. Duringour exchange, this individual did not ask about the possible health effects of vapor intrusion. CTDPH and the local health department are not aware of any specific community concerns at thistime. In the future, CT DPH will contact the families living at the adjacent properties (See Public Health Action Plan).


CONCLUSIONS

Based on the limited data at or near the two residential properties, DPH has estimated that indoorair concentrations could exceed chronic comparison values for 1,1-DCE, TCE, and vinyl chloride. This conclusion does not mean that adverse health effects can be expected because theconcentration estimates are based on upper-bound estimates of exposure, and the chroniccomparison values incorporate conservative estimates of risk. Actual indoor air data, and betterestimates of exposure duration, would likely result in a lower estimate of present-day exposure.

ATSDR has a categorization scheme whereby the level of public health hazard at a site is assignedto one of five conclusion categories (Attachment C). Because actual indoor air data does notexist, DPH has concluded that the present public health hazard at the Broad Street and OldNewtown Road residences is indeterminate in nature. Because data for evaluating past exposuresat these two residences is also insufficient, the risk from past exposure is also indeterminate. Atpresent, there is no evidence suggesting that the vapor intrusion potential at the other (i.e.,commercial) addresses is significant. Further consideration will be given to sampling thecommercial addresses if subsequent sampling of residential indoor air indicates that a publichealth hazard is present.


RECOMMENDATIONS

CT DPH recommends testing the indoor air at the two residences because the potential for vaporintrusion is high. In contrast, the potential for vapor intrusion is much less at the other threeaddresses. Therefore, unless there is evidence of structural defects (i.e., significant cracking of theslab), indoor air testing is not recommended for the structures built on a concrete slab at thepresent time.


PUBLIC HEALTH ACTION PLAN

Actions Planned

  1. CT DPH will provide input to EPA on development of a sampling plan to furthercharacterize the nature and extent of indoor air impacts in the homes of interest.

  2. If EPA takes exposure reduction measures in any of the homes, CT DPH will work withEPA, CT DEP and the Danbury Health Department to evaluate alternatives and respond topublic health questions and concerns.

  3. CT DPH will continue to work with EPA, CT DEP and the Danbury Health Department toprepare a letter to the residents of 2 Broad Street and 2 Old Newtown Road which will:(1) summarize the results of the EPA Soil Gas and Indoor Air Study; (2) provide a publichealth interpretation of the results; and, (3) discuss next steps.

  4. CT DPH will work with the Danbury Health Department in responding to public healthconcerns and questions.

REFERENCES

ATSDR 1994. Toxicological Profile for 1,1-DCE, U.S. Department of Health and HumanServices, Public Health Service, Agency for Toxic Substances and Disease Registry, May 1994.

EPA (2001). Supplemental guidance for evaluating the vapor intrusion to indoor air pathwayEPA draft document p. 9: 10/23/2001

EPA 1998. Environmental Protection Agency Integrated Risk Information System, 1,1-DCECarcinogenicity Assessment, February 1, 1998.


CERTIFICATION

The Health Consultation for Indoor Air Evaluation in Danbury Connecticut was prepared by theConnecticut Department of Public Health under a cooperative agreement with the Agency forToxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodologyand procedures existing at the time the health consultation was initiated.

Gregory V. Ulirsch
Technical Project Officer, SPS,SSAB,DHAC


The Division of Health Assessment and Consultation (DHAC), ATSDR, has reviewed this HealthConsultation and concurs with its findings.

Roberta Erlwein
Chief, SPS, SSAB,DHAC,ATSDR


PREPARER OF HEALTH CONSULTATION

Stewart K. Chute, PhD
Toxicologist
Environmental Epidemiology and Occupational Health
Connecticut Department of Public Health


ATSDR Regional Representative:

William Sweet
EPA/New England


ATSDR Technical Project Officer:

Greg V. Ulirsch
Superfund Site Assessment Branch
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry


ATTACHMENT A: DIAGRAM OF THE RISDON FACILITY WITH ADJACENT PROPERTIES

MW: Location of monitoring well
SG:
Soil gas location

Diagram of the Risdon Facility with adjacent properties


ATTACHMENT B: ATSDR PUBLIC HEALTH HAZARD CATEGORIES

Category Definition Criteria
A. Urgent public health hazard This category is used for sites that pose an urgent public health hazard as the result of short-term exposures to hazardous substances. evidence exists that exposures have occurred, are occurring, or are likely to occur in the future AND

estimated exposures are to a substance(s) at concentrations in the environment that, upon short-term exposures, can cause adverse health effects to any segment of the receptor population AND/OR

community-specific health outcome data indicate that the site has had an adverse impact on human health that requires rapid intervention AND/OR

physical hazards at the site pose an imminent risk of physical injury

B. Public health hazard This category is used for sites that pose a public health hazard as the result of long-term exposures to hazardous substances. evidence exists that exposures have occurred, are occurring, or are likely to occur in the future AND

estimated exposures are to a substance(s) at concentrations in the environment that, upon long-term exposures, can cause adverse health effects to any segment of the receptor population AND/OR

community-specific health outcome data indicate that the site has had an adverse impact on human health that requires intervention

C. Indeterminate public health hazard This category is used for sites with incomplete information. limited available data do not indicate that humans are being or have been exposed to levels of contamination that would be expected to cause adverse health effects; data or information are not available for all environmental media to which humans may be exposed AND

there are insufficient or no community-specific health outcome data to indicate that the site has had an adverse impact on human health

D. No apparent public health hazard This category is used for sites where human exposure to contaminated media is occurring or has occurred in the past, but the exposure is below a level of health hazard. exposures do not exceed an ATSDR chronic MRL or other comparable value AND

data are available for all environmental media to which humans are being exposed AND

there are no community-specific health outcome data to indicate that the site has had an adverse impact on human health

E. No public health hazard This category is used for sites that do not pose a public health hazard. no evidence of current or past human exposure to contaminated media AND

future exposures to contaminated media are not likely to occur AND

there are no community-specific health outcome data to indicate that the site has had an adverse impact on human health





1. Soil gas is a term describing gas that fills the tiny voids between soil particles. Usually, the voids between soil particles are filled with water. However, when groundwater is contaminated with volatile organic chemicals, the chemicals can separate into the gas phase and move into the soil particle voids. High levels of contaminants in soil gas can enter confined building spaces such as basements through crawl spaces, plumbingholes, other floor holes such as sumps and foundation cracks and can contaminate indoor air.
2. The conventional basis for calculating cancer risk is the "slope factor". EPA derived this number from results of a single study in mice (See Maltoni et al. (1985) Arch Res Ind Carcinogenesis Vol 3), and supported it in a 1998 review currently available from IRIS. However, it is apparent that EPA intends to remove this benchmark from its IRIS database because they no longer believe that risk calculations based on the 1,1-DCE slope factor can be justified in light of negative results from other studies. EPA's new assessment is now in draft form and is available on the web at http://www.epa.gov/superfund/programs/risk/iris.pdf



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