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Evaluation of Indoor Air Sampling 4625 Rockwood Parkway



The U.S. Environmental Protection Agency (EPA) asked the Agency for Toxic Substances and Disease Registry (ATSDR) to review indoor air and soil gas sampling data to determine if exposure to chemical substances detected in indoor air posed an immediate or long-term health hazard to residents occupying a home at 4625 Rockwood Parkway, Spring Valley. EPA asked ATSDR to recommend actions necessary to protect the health of building occupants. The house was occupied at the time of sampling, but vacated at the time ATSDR received the data. The building occupants lived in the house for less than one year. The property remains vacant with the potential for American University to lease it to another tenant.

The property at 4625 Rockwood Parkway is located in the Spring Valley Formerly Used Defense Site (FUDS) in an area adjacent to a debris field on lot 18. The area was formerly occupied by the American University Experiment Station (AUES) between 1917-1920. During World War I, the AUES was established to investigate testing, production and effects of chemical warfare agents, antidotes and protective equipment. The AUES is located on the grounds of the present American University, which owns and leases the property. A former tenant living in the house found laboratory glassware and other debris on the property and believed that it came from former AUES activities.

The former occupants experienced a number of symptoms including rashes, headaches, dry skin and itchy eyes, respiratory problems, fatigue, joint pain, sore throat and depression. The occupants were concerned that the symptoms they were experiencing were related to exposure to hazardous materials originating from AUES disposal areas (Hansen, 2003). ATSDR was not able to obtain information from the former occupant regarding the number of individuals reporting symptoms and the onset and duration of the reported symptoms since the former occupant has vacated the property and left the United States.

In June 2003, W.L. Gore and Associates, Inc. performed soil gas and indoor air sampling at the property. Copies of the sampling data were provided to the EPA Region 3 office in Philadelphia and the Washington, DC Health Department.

Environmental sampling history

During the period June 10-24, 2003, 31 sampling modules were placed in various locations in the home and in soil on the property (W.L. Gore and Associates, Inc., 2003). The sampling plan was designed to collect a broad range of volatile and semivolatile chemicals including petroleum hydrocarbons, chlorinated hydrocarbons, potential explosive degradation products and potential chemical warfare agent degradation products. The samples were intended to identify chemical contaminants that a building occupant might be exposed to from breathing indoor air and identify if further focused indoor air sampling was warranted.

The sampling modules passively collected organic chemical compounds on an adsorbent sampling medium, which was later analyzed by a gas chromatograph using a modified EPA Method 8260/8270. Maximum detected concentrations in indoor air are presented in Table 1. For additional details on sampling and analytical methodologies, refer to the referenced environmental sampling report (W.L. Gore and Associates, Inc., 2003).

Detected substances in soil gas included low levels of some polyaromatic hydrocarbons and several common volatile organic chemicals including petroleum hydrocarbons, BTEX (benzene, toluene, ethylbenzene and xylene), trimethylbenzenes, napthalene and chloroform. The low concentrations of chemicals detected in the soil gas would not be high enough to significantly impact indoor air.

When evaluating indoor air quality, ATSDR considers the widespread nature of many commonly found chemicals in building indoor air. In addition to an identified source of contamination (such as a underground waste disposal site), many chemicals routinely detected in indoor air originate from common sources including cleaning chemicals, gasoline, cosmetics, perfumes, paints, air fresheners, dry cleaning, cigarette smoke, and cooking byproducts.

In 1982, EPA conducted random air sampling in 15 homes without a known subsurface source of contamination. Sampling detected the following concentrations: benzene (up to 5.6 ppb), toluene (up to 1010 ppb), ethylbenzene (up to 7.6 ppb), and xylenes (up to 18 ppb) (EPA 1991). These concentrations are typical of many indoor air samples taken in urban dwellings and are considered to be in the range of background. Comparing the maximum detected concentrations at 4625 Rockwood Parkway (benzene, 0.31 ppb; toluene, 0.52 ppb; ethylbenzene, 0.09 ppb; and xylenes, 0.41 ppb) to the background values reported by EPA, there does not appear to be an unusual source of indoor air contamination in the house. No chemical warfare agents, explosives or their environmental degradation products were detected in the home.

Data sources and quality assurance

In preparing this document, ATSDR reviewed and evaluated information provided in the referenced documents. In its evaluation ATSDR assumes that adequate measures to preserve data quality were followed with regard to sampling, laboratory analysis and data reporting, and that the data provided to ATSDR were representative of the chemical concentrations reported in indoor air and soil gas at the time of sampling.

Table 1. Chemical compounds sampled in indoor air at 4625 Rockwood Parkway.

Chemical Maximum detected concentration (ppb) Chemical Maximum detected concentration (ppb)
Total petroleum hydrocarbons 81.00 Phenanthrene 0.26
BTEX 1.30 Anthracene 0.04
Benzene 0.31 Fluoranthene 0.02
Toluene 0.52 Pyrene 0.02
Ethylbenzene 0.09 Vinyl chloride ND
m,p-Xylene 0.41 1,1-DCE ND
o-Xylene 0.22 Chloroform 0.18
C11, C13, C15 hydrocarbons 1.80 Carbon tetrachloride ND
Undecane 1.60 Dimethyldisulfide ND
Tridecane 0.18 1,1,2-TCA ND
Pentadecane 0.48 Chlorobenzene ND
Trimethylbenzenes 1.10 1,1,1,2-Tetrachloroethane ND
1,2,4-Trimethylbenzene 1.00 DMMP ND
1,3,5-Trimethylbenzene 0.09 1,4-Thioxane ND
ct1,2-DCE ND 1,1,2,2-Tetrachloroethane 0.04
t1,2-DCE ND 1,3-DCB ND
c1,2DCE ND 1,2-DCB ND
Polyaromatic hydrocarbons 1.10 DIMP ND
NAPH, 2MN 0.01 1,4-Dithiane ND
Napthalene 0.72 Nitrobenzene ND
2-methyl napthalene 0.14 2-Nitrotoluene ND
MTBE ND Thiodiglycol ND
1,1-DCA ND 3-Nitrotoluene ND
1,1,1-TCA ND 4-Nitrotoluene ND
1,2-DCA ND Benzothiazole 0.20
Trichloroethylene ND 4Chloroacetophenone ND
Octane 0.61 pChlorophenylmethylsulfide ND
Tetrachloroethylene 0.43 2Chloroacetophenone ND
1,4-Dichlorobenzene 0.07 1,3-DNB ND
Acenaphthene 0.04 2,6-DNT ND
Acenaphthylene 0.11 pChlorophenylmethylsulfoxide 0.03
Fluorene 0.10 2,4-DNT ND
2,4,6-TNT ND pChlorophenylmethylsulfone 0.04
1,3,5-TNB ND    

ND: Not detected


This section details the ATSDR evaluation of the health impact of exposure to substances detected in indoor air and determination of the degree of public health hazard. From a review and evaluation of the indoor air sampling data, ATSDR determines that the detected concentrations of chemical substances appear too low to create a health hazard to adult or child occupants breathing indoor air at 4625 Rockwood Parkway.

How was sampling data evaluated?

ATSDR scientists evaluate site conditions to determine if people could have been, are, or could be exposed (i.e., exposed in a past scenario, a current scenario, or a future scenario) to site-related contaminants. When evaluating exposure pathways, ATSDR identifies whether exposure to contaminated media (soil, sediment, water, air, or biota) has occurred, is occurring, or will occur through ingestion, dermal (skin) contact, or inhalation.

If exposure was, is, or could be possible, ATSDR scientists consider whether contamination is present at levels that might affect public health. ATSDR scientists select contaminants for further evaluation by comparing them against health-based comparison values. Comparison values (CV) are developed by ATSDR from available scientific literature related to exposure and health effects. CVs reflect an estimated contaminant concentration that is not likely to cause adverse health effects, assuming a standard daily contact rate (e.g., an amount of water or soil consumed or an amount of air breathed) and body weight.

The comparison values do not represent thresholds for adverse health effects. The values establish contaminant concentrations many times lower than levels at which no effects were observed in experimental animals or human epidemiologic studies. If contaminant concentrations are above CVs, ATSDR further analyzes exposure variables (for example, duration and frequency of exposure), and further considers the range of biomedical literature in evaluating the health impact of exposure.

ATSDR compared the maximum detected concentrations of chemicals in indoor air to health protective CVs to identify if further site-specific evaluation of exposure was needed (Table 2). For the substances that exceeded comparison values, the low concentrations in building indoor air would result in exposure doses orders of magnitude below doses where toxicity was observed in studies of exposed animals and people. ATSDR believes these substances are not present at concentrations posing a health hazard to building residents.

In addition to those compounds that exceeded CVs, several detected compounds lacked health guideline values and in-depth information regarding inhalation toxicity and were included for further evaluation (Table 2). In most instances, these chemicals were evaluated by: 1) assessing them as individual substances rather than generic chemical class, 2) comparing them to similar compounds with health guidance values, or 3) basing toxicity considerations upon chemical structure or alternate exposure routes. Three chemicals did not fall into any of these categories: benzothiazole, p-chlorophenylmethylsulfoxide, and p-chlorophenylmethylsulfone. Available information from the biomedical literature was identified and evaluated for these compounds. Although comprehensive toxicity information is lacking, trace concentrations in building indoor air would result in exposure doses orders of magnitude below doses where toxicity was observed in animal studies. Based upon the scientific literature, ATSDR believes these substances would not present a health hazard to building residents at the detected concentrations. Benzothiazole is discussed in more detail later in this document.

Table 2. Chemical substances considered for further evaluation.


Maximum detected concentration (ppb)

Comparison value (ppb)


Benzene 0.31 0.07 No public health hazard. Concentration below concern for increased cancer or non cancer health effects.
Napthalene 0.72 0.44 No public health hazard. Concentration below concern for non cancer health effects
Tetrachloroethylene 0.43 0.05 No public health hazard. Concentration below concern for increased cancer or non cancer health effects.
1,4-Dichlorobenzene 0.07 0.05 No public health hazard. Concentration below concern for increased cancer or non cancer health effects.
Chloroform 0.18 0.02 No public health hazard. Concentration below concern for increased cancer or non cancer health effects.
1,1,2,2-Tetrachloroethane 0.04 0.004 No public health hazard. Concentration below concern for increased cancer or non cancer health effects.
Total petroleum hydrocarbons 81.00 NA Evaluated as individual compounds, no public health hazard.
BTEX 1.30 NA Evaluated as individual compounds, no public health hazard.
C11, C13, C15 hydrocarbons 1.80 NA No public health hazard. Concentration of straight chain hydrocarbons below level of concern for adverse health effects.
Undecane 1.60 NA No public health hazard. Concentration of straight chain hydrocarbons below level of concern for adverse health effects.
Tridecane 0.18 NA No public health hazard. Concentration of straight chain hydrocarbons below level of concern for adverse health effects.
Pentadecane 0.48 NA No public health hazard. Concentration of straight chain hydrocarbons below level of concern for adverse health effects.
Trimethylbenzenes 1.10 NA Evaluated as individual compounds, no public health hazard
Polyaromatic hydrocarbons 1.10 NA Evaluated as individual compounds, no public health hazard
2-Methylnapthalene 0.01 NA Evaluated as individual compounds, no public health hazard
Octane 0.61 NA No public health hazard. Concentration of straight chain hydrocarbons below level of concern for adverse health effects.
Acenaphthylene 0.11 NA Toxicity was assumed to be similar to acenapthene. Concentration below concern for increased cancer or non cancer health effects.
Phenanthrene 0.26 NA Toxicity was assumed to be similar to anthracene. Concentration below concern for increased cancer or non cancer health effects.
Benzothiazole 0.20 NA Concentration below concern for increased cancer or non cancer health effects.
pChlorophenylmethylsulfoxide 0.03 NA Concentration below concern for increased cancer or non cancer health effects.
pChlorophenylmethylsulfone 0.04 NA Concentration below concern for increased cancer or non cancer health effects.

NA: Not available or applicable to inhalation exposure route.

Short-term health effects

Acute health impacts are generally observed following short-term exposure to very high concentrations. No chemical substances were detected at concentrations high enough to create an acute or immediate health hazard. Except for petroleum hydrocarbons detected at a maximum of 81 ppb in the basement along the garage wall, all chemical substances were below 1 part per billion (ppb). Generally, such low concentrations would not be expected to pose an immediate or short-term threat.

Longer-term health effects

An evaluation of the indoor air sampling data indicates no appreciable cancer or non-cancer health impacts from breathing substances detected in indoor air. Chemical concentrations were too low to result in health harm, even from breathing maximum levels on a daily basis for months to years. The previous tenants occupied the home for a short period (approximately one year), further limiting the extent and duration of their exposure.

Relationship of indoor air at 4625 Rockwood Parkway to specific health concerns

Benzothiazole and detection of sulfur mustard (mustard gas) breakdown products

Prior to the recent indoor air and soil gas sampling, the U.S. Army Corps of Engineers (USACE) performed soil sampling at this property in 2002 and documented the sampling in a report by Parsons Engineering Science. The report indicates surface soil contamination with arsenic, polyaromatic hydrocarbons and environmental degradation products of sulfur mustard (Parsons, 2002). In 2004, USACE plans to remediate the soil contamination. ATSDR will discuss and evaluate public health impacts of soil contamination in a separate document currently under development.

A letter to the EPA Region 3 Administrator by legal counsel retained by a previous resident of 4625 Rockwood Parkway expresses concern that benzothiazole is "a by-product of mustard gas" (Barer, 2003). ATSDR was unable to find any information in the scientific literature to support that assertion. Although present in surface soil, sulfur mustard degradation products, including 1,4-thioxane, 1,4-dithiane and thiodiglycol were not detected in indoor air.

Information in the National Libraries of Medicine's Hazardous Substances Databank (HSDB) reveals that benzothiazole is a volatile organic chemical common to several manufacturing processes, is listed as a flavor additive in food, an accelerator in the rubber vulcanization process, as an antimicrobial and antifungal agent commonly found in shoe insoles, and as a component of cyanine dyes. Benzothiazole has been studied in animal toxicity experiments and occupational health surveys in the rubber industry, though toxicity information is limited. An acute inhalation lethality study in rats demonstrated a median lethal dose of 253,199 ppb (RTECS, 2003). Trace levels reported in indoor air in the Rockwood property (up to 0.2 ppb) would be unlikely to cause health harm.

ATSDR did locate one article discussing benzothiazole and its use as a chemical intermediate in producing organosulfur compounds for use as pre-exposure therapies for sulfur-containing agents such as sulfur mustard (Ternay et al., 2000). A question arose regarding the possibility that the benzothiazole detected in indoor air might have resulted from wastes generated by past research or production when the AUES was in operation. Upon further evaluation, it appears that the benzothiazole compound identified in the Ternay study has a different chemical structure than the benzothiazole detected in the home and appears unrelated to AUES activity.

Benzothiazole was not detected in soil gas, which would indicate that the source of this substance was not in the subsurface. Additionally, indoor air sampling did not find it in the basement, which would have been expected if the source were under the home. The maximum concentration was detected in the bedroom. Benzothiazole is used as an antifungal agent in shoe insoles, and a common compound used in producing in rubber products. Given its use in common household products there may be a local source in the room that resulted in the detection in indoor air.

The US Army Center for Health Promotion and Preventive Medicine, (USACHPPM) was unable to locate any information in the scientific literature to suggest that two other detected compounds, pChlorophenylmethylsulfoxide and pChlorophenylmethylsulfone are chemical warfare agent breakdown products (Baron, 2003).

Odors in the home

The former occupant expressed concern regarding odors reminiscent of cut hay and its possible relation to the presence of war gases like phosgene (Barer, 2003). Phosgene has a characteristic odor that can only be detected briefly at the time of initial exposure. Around 0.5 parts per million in air (500 parts per billion), the odor has been described as pleasant and similar to that of new-mown hay or cut green corn. At high concentrations in the range of human toxicity, the odor may be strong, stifling, and unpleasant. Human symptoms at concentrations around 4-10 ppm (parts per million, equivalent to 4000-10,000 ppb) include eye and throat irritation, tightness in the chest, shortness of breath, wheezing, and coughing (IPCS, 1997). Phosgene or agent-specific degradation products were not detected in indoor air.

Presence of mold or mildew might explain some of the odors detected in the home. Exposure to molds can cause symptoms in sensitive individuals such as nasal stuffiness, eye irritation and respiratory problems, which were all reported as health symptoms in the residents. Molds are found in virtually every environment and can be detected year round both indoors and outdoors. Mold growth is encouraged by warm and humid conditions. Indoors they are commonly found in basements or showers where humidity levels are high.

Inside homes, mold growth can be slowed by keeping humidity levels below 50% and ventilating showers and cooking areas. Mold growth can be removed with commercial products or a weak bleach solution (1 cup of bleach in 1 gallon of water). For more information on molds and indoor air quality, go to the Centers for Disease Control and Prevention website at or the USEPA website at .

Carbon monoxide

While the former tenants occupied the home, elevated concentrations of carbon monoxide were reportedly detected. This was apparently due to a faulty heating system, which was subsequently corrected by the building owner (Hirsch, 2003). ATSDR has no information on the past levels of carbon monoxide measured in the home or when the levels were detected. The signs and symptoms of non-lethal carbon monoxide poisoning, especially from intermittent, low-level exposures can be mistaken for other illnesses common seen in the primary care setting including headaches, chronic fatigue, depression, and viral illness (Abelsohn et al., 2002). These symptoms are similar to health concerns expressed by the former resident.

Child Health Considerations

ATSDR is committed to protecting children's health. ATSDR recognizes that infants and children may be more sensitive than adults to environmental exposure in communities faced with water, soil, air or food contamination. This concern for possible increased sensitivity is the result of several factors, including: (1) children are smaller than adults, resulting in higher doses of chemical exposure per unit body weight; (2) children's bodies may be more sensitive to the effects of chemical exposures. Children have developing body systems which can sustain permanent damage if toxic exposures occur during critical growth stages. At 4625 Rockwood Parkway, ATSDR used health guidelines protective for children in its evaluation of public health impact from exposure to chemical substances in indoor air. At the low levels detected no adverse health impacts in children would be expected.


From a review and evaluation of the indoor air sampling data and available toxicological and medical information relevant to the substances of interest, ATSDR concludes that the presence of low levels of volatile and semivolatile substances in indoor air at 4625 Rockwood Parkway poses no apparent public health hazard to adult or child occupants.

The presence of laboratory glassware and debris from AUES in soil at the property indicates the possibility of a subsurface disposal area in the vicinity of the residence. The soil gas sampling was conducted during heavy precipitation, which might have affected the accuracy and validity of the soil gas data. As a result, ATSDR does not have confidence that the soil gas data is adequate to rule out the presence of a subsurface source. Further sampling of shallow and deep soil gas would serve to confirm the previous sample results obtained from the passive sampling modules and eliminate the uncertainty about the presence of subsurface contamination.

Past detection of elevated carbon monoxide concentrations in the home indicate that carbon monoxide levels were elevated and may have contributed to reported health symptoms. Although the furnace system was previously serviced, it is unknown what current carbon monoxide levels are in the home and if the combustion sources that have the potential to generate carbon monoxide (i.e. furnace) are operating as designed.


ATSDR makes the following recommendations:

  1. Conduct further confirmatory sampling at the property. The first phase should focus on deep and shallow soil gas. Soil gas sampling should be performed using an EPA-approved methodology capable of detecting chemical warfare agent degradation products.

    • If sampling reveals volatile constituents in the soil vapor that could potentially impact indoor air, then further indoor air sampling should be conducted utilizing an EPA-approved sampling method ideally designed to sample indoor air over a 24-hour period under a worst-case situation (i.e. windows closed, mechanical ventilation running, etc.).

  2. Ensure carbon monoxide levels are within a safe range prior to leasing to future tenants.

    • Sample for carbon monoxide with windows closed and the heating system operating under normal conditions.
    • Install a UL/CPSC approved CO monitor.
    • Service the HVAC system and other combustion sources in the home as necessary to ensure proper operation.


Scott Sudweeks
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Technical advisors

Gary Campbell
Chief, Defense section
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Laura Frazier
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation


You may contact Scott Sudweeks at ATSDR in Atlanta, GA by calling the toll-free number (888) 42-ATSDR (888-422-8737). You may also contact Tom Stukas, ATSDR's Regional Representative in Philadelphia, PA at (215) 814-3142.

Written correspondence should be directed to:
1600 Clifton Road, MS E-32
Atlanta, GA 30333

Additional information about ATSDR services and the public health impacts of exposure to hazardous substances is available on the ATSDR web site at


Abelsohn, A; Sanborn, M; Jessiman, B; Weir, E. 2002. Identifying and managing adverse environmental health effects: 6. Carbon monoxide poisoning. CMAJ. 166(13). June 25, 2002.

Barer, GS. 2003. Letter to Donald Welsh, EPA Region 3. July 15, 2003.

Baron, J. 2003. U.S. Army Center for Health Promotion and Preventive Medicine. Written communication commenting on draft evaluation of indoor air sampling, 4625 Rockwood Parkway. September 2, 2003.

Hansen, F. 2003. Testimony before the DC Council, Committee of Public Works and the Environment and Committee on Human Services. July 14, 2003.

Hirsch, S. 2003. EPA Region 3, Philadelphia, PA. Personal communication, July 24, 2003.

International Programme on Chemical Safety (IPCS).1997. Environmental Health Criteria 193: Phosgene. United Nations Environment Program, International Labor Organization and the World Health Organization.

Parsons Engineering Science, Inc. 2002. Report of Analytical Results - American University Experiment Station (AUES) List of Chemicals for Four Spring Valley Operable Unit 4 Properties. Washington, D.C. Prepared for U.S. Army Corps of Engineers, Baltimore District. May 8, 2002.

Registry of Toxic Effects of Chemical Substances (RTECS). Benzothiazole. U.S. Department of Health and Human Services. 2003.

Ternay, A.L; Brzezinska, V; Sorokin C; Cook, C; Lyaschenko Yu. 2000. Organosulfur compounds as pre-exposure therapy for threat agents. J Appl. Toxicol. 20, S31-34.

W.L. Gore & Associates, Inc. 2003. GORETM survey for site assessment final report, 4625 Rockwood Parkway, Washington, DC. Addendum. July 18, 2003.

U.S. Environmental Protection Agency (EPA). 1991. Introduction to Indoor Air Quality: A Reference Manual. July, 1991.

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