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Public Health Evaluation of Indoor Air Data


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.


The Connecticut Department of Public Health (CTDPH) was asked by the Stratford HealthDepartment to review volatile organic chemical (VOC) levels in indoor air data from theStratford Army Engine Plant (SAEP) for the purpose of determining the suitability, from a publichealth perspective, of leasing portions of the plant to the Town of Stratford.

The SAEP is a complex of 49 buildings that was formerly used for heavy industry and supportingadministrative, research and development activities by the US Department of Defense. TheSAEP is being remediated by the Army with oversight of the Connecticut Department ofEnvironmental Protection (CTDEP) and the US Environmental Protection Agency (EPA).

The Town of Stratford is interested in leasing buildings or portions of buildings at the SAEP forlight industrial/commercial activities and asked the CTDPH for advice regarding which buildingsor portions of buildings were suitable for leasing, given the levels of VOCs in indoor air andlikely exposures that would occur.

The Army has stated that air standards established by the Occupational Health and SafetyAdministration (OSHA) are suitable occupancy standards for buildings at the SAEP (FOSL2002). In other words, if levels of VOCs in indoor air are below OSHA standards, the Armyconsiders the buildings suitable for any worker without the need for further remediation orcontrols. CT DPH disagrees with this approach as OSHA standards were designed primarily forindustries which use VOCs in industrial production and thus involve workers who areunavoidably exposed. To protect those workers, OSHA requires that employers provideappropriate training and information regarding exposure, exposure control and potential healtheffects from the hazardous chemicals they are exposed to in their workplace. It would not bereasonable to expect employers to provide such information and protections to their non-industrial workers (for example, a pregnant female office worker). Given these factors, theOSHA standards are not appropriate for the non-industrial workplace. Moreover, OSHAstandards are not strictly health-based. For most chemicals, OSHA standards are a compromisebetween health-based values and levels that are technically feasible for industry to achieve.

Since there are no federal standards for indoor air quality in non-industrial environments, statessuch as Connecticut have derived Target Indoor Air Concentrations (TACs) to guide remediationstemming from subsurface contamination in both occupational and residential settings. TheseTACs are health-based and so are appropriate levels for basing decisions about the suitability ofleasing buildings at the SAEP. CTDPH has evaluated VOC data from indoor air in buildings atthe SAEP using the TACs as screening levels. CTDPHs evaluation is summarized in thesections that follow.

Environmental Data

There is significant groundwater contamination with VOCs that underlies much of the SAEP site. Data collected by the Army indicate exceedances of the Connecticut volatilization criteria for soiland groundwater beneath several buildings at the SAEP site (FOSL 2002). Vapors from theVOCs in groundwater have migrated into indoor air of several buildings.

Indoor air data were provided to CTDPH for review by the Town. The indoor air samplingoccurred during the period September 1999 to May 2002 by the Army and focused on buildingsthat are above the highest groundwater and soil gas concentrations and buildings the Townidentified as likely candidates for leasing. Indoor air samples were collected in the breathingzone over an eight-hour time period using passivated SUMMA canisters and were analyzed forVOCs using EPA Method TO-15. This is a standard procedure for sampling ambient air. Insome buildings, only a single location was sampled. In other buildings, data are available formultiple locations within that building. The indoor air sampling data was collected by the Armyas part of its ongoing monthly indoor air monitoring program. Not every location is sampledeach month. Some locations have as few as one or two rounds (months) of data while otherlocations have as many as 26 rounds (months) of data. There are no readily apparent seasonaltrends in indoor air concentrations or trends toward decreasing or increasing concentrations overtime.


Exposure Pathways and Public Health Implications

This health consultation focuses on public health implications of exposures to future tenants ofthe SAEP. If the Town of Stratford leases buildings at the SAEP, future workers could beexposed to contaminants by breathing indoor air. There are no other exposure pathways forfuture tenants. Potential current exposures were not evaluated in this health consultationbecause: (1) the majority of the buildings at the plant are unoccupied; (2) the Army evaluatesindoor air data for locations where their security workers are stationed; and (3) CTDPH wasasked by the town of Stratford to focus on potential exposures to future tenants.

As a first step in evaluating the indoor air data, CTDPH compared maximum VOCconcentrations in each location with CTDEP industrial/commercial Target Air Concentrations(TACs). TACs are levels in indoor air that are not expected to pose a health threat, assuminglong-term exposure. They are guidelines used to trigger the need for remediation at hazardouswaste sites. The TACs for two chemicals (1,1-DCE and TCE) have been updated recently byCTDPH to reflect toxicology reevaluations at both the federal and state level. These revisedTACs have been used by CTDPH in recent evaluations of indoor air VOC data at anotherhazardous waste site in Stratford, the former Raymark facility site (ATSDR 2000, ATSDR2003).

Table 1 below provides the TACs used in this first step of the evaluation. There are three VOCs detected at SAEP at levels exceeding TACs in at least one sampled location (tetrachloroethylene [PCE], TCE and vinyl chloride). The Table also includes the maximum concentration of each VOC that was detected in any sampled location.

Table 1.

Maximum indoor air concentrations detected at the Stratford Army Engine Plant and Comparison Values (CTDEP Industrial/Commercial Target Air Concentrations) used to screen indoor air data.
Chemical Target Air Concentration (ppb) Maximum Concentration (ppb)
1,1,1-Trichloroethane 191 2.5
Trichloroethylene 0.19^ 11
Tetrachloroethylene 1.62 9.6@
Vinyl Chloride 0.36 0.62
1,1-Dichloroethylene 2.5* 1.1

^ This value is background-based.
* This value was developed for residential settings. A commercial/industrial value based on updated toxicity information has not yet been developed.
@ A level of 20 ppb was detected in one building but it is likely not related to vapor intrusion but rather, new carpeting that had just been installed in the location where sampling occurred.

The next step in CTDPH's evaluation involved calculating theoretical cancer risks for eachlocation which had an exceedance of a TAC. CTDPH calculated cancer risks associated with five years of exposure to the maximum VOC concentration detected at those locations. Exposurewas assumed to occur 8 hours per day, 5 days per week, 50 weeks per year. CTDPH selectedfive years as the exposure period because it reflects the maximum anticipated term of a lease forthe buildings. In addition, final remedial decisions on the site should be reached within a fiveyear period. For the reasons detailed below, CTDPH considers this exposure scenario torepresent a conservative but not necessarily worst case estimate of potential exposure.

  • Assumptions about exposure duration (8 hours per day, 5 days per week, 50 weeks per year)are realistic for a typical worker.
  • For TCE risk calculations, CTDPH used the midpoint (rather than the upper end) of EPA'snew range for cancer potency. Use of the midpoint provides a less conservative estimate oftheoretical cancer risks than use of the upper end.
  • While CTDPH's use of maximum concentrations is a conservative assumption, it is notnecessarily worst case because in most locations, there are not enough rounds of data toadequately represent the large variability inherent in indoor air VOC concentrations.

Cancer potency values and other inputs to the risk calculations are provided in Attachment 1. Attachment 1 also contains the results of the risk calculations.

Attachment 1 shows that theoretical cancer risks from exposure to maximum concentrationsrange from a low of 7 x 10-9 to a high of 4 x 10-5 (1). For the purposes of this assessment, CTDPHhas assumed that five years is the maximum amount of time prospective tenants will be exposed. For locations with five-year cancer risks less than 1 x 10-6, CTDPH considered them to beinsignificant and no further risk calculations were conducted for that location. In most cases,such locations are considered suitable to lease as long as periodic indoor air sampling occurs toensure that conditions do not worsen in the future.

For those locations with five-year cancer risks (based upon the maximum detected concentration)greater than 1 x 10-5, CTDPH considered those risks to be significantly elevated with suchlocations designated as "Do Not Lease."

For locations with five-year cancer risks between 1 x 10-6 and 1 x 10-5, CTDPH calculated anaverage indoor air concentration to provide a central tendency estimate to compare with themaximum exposure. All 5-year cancer risks based on the average concentration were near orbelow 1 x 10-6. CTDPH considered these locations suitable to lease, with more sampling.

Table 2 below summarizes CTDPH's conclusions regarding the suitability to lease for eachlocation at the SAEP for which indoor air data was provided. Attachment 1 contains the fulldetails of the evaluation. In making its decisions, CTDPH considered the magnitude of the risksas discussed above. CTDPH also considered whether there was sufficient data on which to basea decision and also the frequency of detections of VOCs above TACs. CTDPH notes that its recommendations are based on an assumed maximum occupancy period of five years. Ifbuildings are occupied for a longer period, exposures and risks should be reassessed. In addition,CTDPH's evaluation did not include a thorough review of all of the quality control/qualityassurance aspects of the Army's indoor air data. As stated previously, the Army did use standardsample collection and analysis protocols for ambient air. For purposes of this evaluation,CTDPH assumes that the Army's indoor air data are of good quality.

Table 2.

Summary of CTDPH Recommendations on Suitability to Lease Buildings at the SAEP.
Building/Location CTDPH Recommendation
Building 1, Main Entrance Do Not Lease
Building 1, 2nd Floor OK to lease with more sampling
Building 1, 3rd Floor OK to lease, no further sampling needed
Building 2, Boiler Room Unlikely location for extensive exposure
Building 2, ground floor south end OK to lease with more sampling
Building 2, ground floor, north end and center Do Not Lease
Building 2, 2nd floor, north end OK to lease with more sampling
Building 3, all locations OK to lease with more sampling
Building 4 OK to lease with more sampling
Building 6, all locations OK to lease with more sampling
Building 9, center OK to lease with more sampling
Building 10, center Do Not Lease
Building 12, Shop Area and Office Area OK to lease with more sampling
Building 48, paint shop OK to lease with more sampling
Building 65 OK to lease with more sampling
ML-01 OK to lease with more sampling
ML-02 OK to lease with more sampling


In this Health Consultation, CTDPH has evaluated indoor air data at SAEP using realistic, yethealth protective exposure assumptions and has made the above recommendations to the Townof Stratford regarding whether specific buildings and portions of buildings should be leased inthe future. It should be stressed that these recommendations are based on data reflecting currentindoor air conditions. Because we do not have data for future conditions, we cannot reachconclusions about exposures or potential health impacts to future occupants from VOCs inindoor air at the SAEP. As stated previously, current exposures were not evaluated as part of thisHealth Consultation.

CTDPH recommends additional sampling in the locations specified in the above table becausethere is uncertainty in the concentrations of VOCs to which future tenants may be exposed. Inmost locations, there are not enough rounds of data to adequately represent the large variabilityinherent in indoor air VOC concentrations. Additionally, the locations in the buildings thatpreviously were sampled may not accurately represent the specific areas that will be occupied. Also, if modifications are made to interior spaces to accommodate future tenants, indoor airsampling will need to be done in the reconfigured spaces.

Future indoor air monitoring should commence once the spaces are reconfigured but prior to building occupancy and should continue periodically thereafter. CTDPH will assist the Town ofStratford, as needed, regarding development of a suitable sampling plan and evaluating futureindoor air monitoring data.

Public Health Action Plan

Actions Taken:

  1. CTDPH has provided technical assistance regarding the indoor air data from SAEP to theTown of Stratford by participating in conference calls and attending meetings with the Armyand its consultants, CTDEP and EPA.

  2. CTDPH has provided its evaluation and recommendations on the suitability to lease buildingsat the SAEP to the Town of Stratford.

Actions Planned:

  1. CTDPH will assist the Town of Stratford, as needed, regarding development of a suitableindoor air sampling plan for SAEP.

  2. CTDPH will review future data and plans for building occupancy for the SAEP, as requested.

  3. CTDPH will assist the Town of Stratford in preparing a fact sheet or other riskcommunication materials informing prospective tenants about indoor air quality.


ATSDR 2000. Health Consultation: Residential Indoor Air Evaluation, Raymark IndustriesIncorporated, prepared by CT Department of Public Health, October 17, 2000.

ATSDR 2003. DRAFT Health Consultation: Residential Indoor Air and Soil Gas Evaluation,Phases 2 and 3, prepared by CT Department of Public Health, January, 2003.

Finding of Suitability to Lease (FOSL), Stratford Army Engine Plant, US Department ofDefense, November 21, 2002.


The Health Consultation for the Stratford Army Engine Plant was prepared by the ConnecticutDepartment of Public Health under a cooperative agreement with the Agency for ToxicSubstances and Disease Registry (ATSDR). It is in accordance with approved methodology andprocedures 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 thisHealth Consultation and concurs with its findings.

Roberta Erlwein


Margaret L. Harvey, MPH
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


Click here to view Attachment 1 in PDF format (PDF, 18KB)

1 A cancer risk of 7 x 10-9 means 7 excess cancers in 1,000,000,000 (one billion) exposed people. A cancer risk of 4 x 10-5 means 4 excess cancers in 100,000 (one hundred thousand) exposed people.

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