Objective

This exposure investigation examined individuals in the Spring Valley neighborhood of Washington, D.C. The investigation focused on whether these individuals had been exposed to arsenic contamination in their yards. The investigation was conducted from July through November 2002 and is the follow-up to an earlier (March 2002) investigation. Urine arsenic levels were tested in 40 individuals: 34 adults and six children aged 21 months to 15 years. All of these individuals were residents of 19 homes where the yards showed elevated soil arsenic levels, or homes adjacent to properties under remediation for elevated soil arsenic levels.

Summary and Statement of Issues

Background

During World War I,at a site known as the American University Experimental Station in northwest Washington, D.C, the U.S. Army conducted chemical warfare research. During research and training operations, chemical weapons were detonated at several locations. Lewisite (which contains arsenic) and mustard gas were among the chemical warfare agents reportedly tested. Chemical agents—including hazardous substances, ordnance, and explosive waste—were buried in the area. Long after the Army vacated the former Experimental Station site, the entire area underwent extensive development. Today it is home to the American University campus and to residential homes that comprise the Spring Valley neighborhood [1].

In January 1993, a contractor digging a utility trench in Spring Valley uncovered buried ordnance. Once notified, the U.S. Army Corps of Engineers (Corps) launched Operation Safe Removal, extracting some 141 ordnance items including suspected chemical munitions containing mustard gas and fuming sulfuric acid. To identify other potentially impacted areas, the Corps reviewed historical records and conducted extensive geophysical surveys with electromagnetic instruments. In addition, to characterize the extent and nature of chemical contamination, the Corps collected soil samples in potentially affected areas. Discovery and remedial efforts continue in Spring Valley and related areas [2].

ATSDR Activities at Spring Valley

The Agency for Toxic Substances and Disease Registry (ATSDR) has been working with the following agencies and groups:

· The Department of the Army,

· the Army Corps of Engineers,

· the U.S. Environmental Protection Agency (EPA),

· the District of .Columbia. Department of Health (DC DOH),

· American University,

· the Spring Valley Science Advisory Panel,

· the Spring Valley Restoration Advisory Board, and

· area residents

to assess the public health impact of environmental contamination from hazardous substances. At the request of the DC DOH, the EPA, or the Corps, between June 1997 and the present ATSDR has prepared five health consultations and one technical assistance document assessing soil contamination at the site.

In December 2000, contaminated soil was identified at the Child Developmental Center at American University. Surface soil samples collected from the playground were contaminated with arsenic at an average concentration of 57 micrograms per gram of soil (µg/g) and a maximum concentration of 498 µg/g. During February 1–2, 2001, ATSDR conducted an exposure investigation at the Child Developmental Center. Hair samples were analyzed for arsenic several weeks after exposure had stopped. Hair samples from 28 children and four adults did not indicate elevated arsenic exposure in children or workers at this center. The property was subsequently remediated [3, 4].

In March 2002, a second exposure investigation examined individuals in the Spring Valley neighborhood for possible exposure to arsenic contamination in their yards. A total of 32 individuals were tested: 23 adults and nine children aged 16 months to 13 years.. These individuals lived in 13 homes at which elevated composite soil arsenic levels were found in the yards. These individuals’ urine and hair were tested and in each of their homes household dust was analyzed for arsenic. Urine and hair arsenic testing showed low levels of arsenic exposure not expected to cause health problems in this population [5].

Other Site-Related Activities

On February 10 and 15, 2001, Washington Occupational Health Associates, Inc. (WOHA), collected hair and urine samples from students and staff at American University. The target population for this exposure investigation included students and staff who attended the Center in the past 12 months, maintenance and grounds crew members, and athletes who use the intramural fields. Sixty-six persons (39 adults and 27 children) provided hair samples. Four adults provided urine samples. WOHA concluded that their exposure investigation indicated no elevated levels of arsenic in the population tested [6].

The Corps has continued to characterize soil contamination in residential properties in potentially affected Spring Valley areas. This testing documented arsenic levels in composite soil samples collected from residential areas. The samples ranged from background levels to a maximum of 202 parts per million (ppm). Residents of Spring Valley have expressed concern over possible health effects from exposure to this contamination. In response to these concerns, the D.C. DOH asked ATSDR to evaluate potential exposure to arsenic in residents of contaminated properties.

Rationale for an Exposure Investigation

The Spring Valley Science Advisory Panel recommended the second phase of this exposure investigation. The Panel was concerned that the first phase of the exposure investigation was conducted in early spring—a time of little outdoor activity and, consequently, little potential for soil contact. By performing the investigation at a time of presumed maximal exposure activities, ATSDR was able to exclude hair analysis (which is not considered a reliable indicator of arsenic exposure) and focus on arsenic levels in urine.

Within a few days following exposure, ingested arsenic is rapidly excreted from the body into the urine. Accordingly, ATSDR analyzed urine samples for arsenic as an indicator of exposure within the preceding few days [7]. The urine samples were analyzed for either total arsenic or speciated arsenic (inorganic arsenic, dimethyl arsenic acid, and methylarsonic acid). In this health consultation the term “inorganic arsenic” is used interchangeably with “speciated arsenic” and refers collectively to all inorganic forms of arsenic, including dimethyl arsenic acid and methylarsonic acid. By conducting speciated analysis, exposure to inorganic arsenic was differentiated from exposure to less toxic forms of arsenic found in food, such as fish and shellfish [8].

Methods

Target Populations

To assess exposure to arsenic, ATSDR tested urine in Spring Valley residents who were classified into one of three groups: (1) individuals who participated in the first exposure investigation, (2) individuals who were living on, or adjacent to, property under remediatation, and (3) individuals who had a single, elevated level of arsenic in their yard.

Consent/Confidentiality

Prior to testing, each participant— and a parent or legal guardian of each minor participant— was required to sign an informed consent/assent form. Sample copies of these forms are in Attachment A. In addition to completing a consent form, each family was asked a few questions about their exposure history.

Individual test results and an explanation of their meaning were provided to the participants in writing. An ATSDR physician was available to discuss individual results by phone and, during a community visit at the local hospital, in person. Recommendations for follow-up actions were made, if indicated. Individual test results were not made available to the public; confidentiality was protected according to federal and state laws.

Test Procedures

DC DOH staff distributed urine specimen cups and instructions to all participants in the exposure investigation. Participants were advised not to eat fish or shellfish for 3 days before donating a first-morning void urine sample. In an attempt to collect urine at the time of the highest likelihood of exposure—that is, during peak outside activities or during soil remediation—urine collection was spread over the late summer and fall.

The urine samples were sent to National Medical Services laboratories in Willow Grove, Pennsylvania. The samples were analyzed for total and speciated arsenic by graphite furnace atomic absorption spectroscopy and by atomic fluorescence spectroscopy. Urine creatinine was also analyzed. Test results were reported as micrograms of arsenic per liter of urine (µg/L) and as micrograms of arsenic per gram of creatinine (µg/g creatinine) [9].

Results

A “Brief Arsenic Exposure Questionnaire” (Attachment B) was administered at the time of urine sampling. This questionnaire revealed eight families who owned pets that spend time outdoors; thus the pets might be a source of soil being tracked into the house. Six individuals reported having recent contact with soil in their yard and one individual reported being a smoker. Three persons reported eating seafood within a short time of providing the sample.

All individuals tested had total urinary arsenic levels between non-detect and 76 g/L. The detection limit was 1.0 µg/L. Most (93%, 37/40) of the participants in this exposure investigation had inorganic urinary arsenic levels of less than 10 µg/L—interpreted by the National Medical Services as “non-detect” and by ATSDR as “not elevated.” A few (7%, 3/40) of the individualshad reportable levels of inorganic arsenic in their urine 10 µg/L, 14 µg/L, and 29 µg/L. When adjusted for dilution using creatinine correction methods, these three individuals’ inorganic arsenic levels were 7 µg/g creatinine, 24.5 µg/g creatinine, and 13.4 µg/g creatinine, respectively. Attachment C contains a table of individual results grouped by household.

During this investigation some inconsistencies appeared in the laboratory’s procedures for analyzing urine arsenic. As stated in the exposure investigation protocol (Attachment D), ATSDR requested total and speciated arsenic analysis for all urine specimens. National Medical Services’ policy, however, was only to speciate samples with a total arsenic level above 20 µg/L. Because the discrepancy between the policy and ATSDR’s request was discovered midway through the investigation, some samples were only tested for total arsenic. National Medical Services also erred in only reporting speciated results for some samples rather than reporting both total and speciated results. However, none of these procedural inconsistencies compromised the overall assessment of arsenic exposure in this population. All elevated total arsenic samples were speciated and no speciated results were high enough to indicate the potential for adverse health effects.

Discussion

To evaluate exposure, arsenic is measured in urine, hair, or blood. Measurement of arsenic in blood is not a reliable indicator of chronic exposure to low levels of arsenic—it is cleared from the blood within a few hours and reflects only very recent exposure. Blood arsenic levels also are difficult to interpret because the relationship between levels of exposure and blood concentrations has not been well established [10].

Urine arsenic is the most reliable method for measuring arsenic exposure, particularly exposures occurring within a few days of the specimen collection. Fluctuations in urine excretion rates make a 24-hour collection an optimal sample. Ease of collection, however, has resulted in most exposure studies using a first-morning void or a random sample In fact, the first-morning void urine results have correlated well with 24-hour results [7]. Speciated urinary arsenic is preferable to total urinary arsenic because the speciated forms can distinguish between exposure to inorganic arsenic and its metabolites and the relatively nontoxic forms of organic arsenic commonly found in seafood [7, 8].

Individuals in this exposure investigation had their urine tested for total arsenic (which could come from all sources—food, water, air, soil, and dust), for inorganic arsenic (which might be coming from contaminated soil and dust), or for both. The total urinary arsenic is mostly organic arsenic from food sources, which is much less toxic than inorganic arsenic. If the total urinary arsenic was not elevated, inorganic arsenic testing was not always performed.

This exposure investigation (EI) included individuals who (1) participated in the first phase of the exposure investigation, (2) who were living on, or adjacent to, property that was being remediated, or (3) who had a single elevated level of arsenic in their yard. Nine of the 13 households from the first EI chose to participate in this second EI. Three of these families were having their yards remediated when the urine testing was done. An additional six households fell into the second group of those who had their urine tested while an adjacent property was under remediation. Four more households were added to this EI because they had one elevated arsenic level in their yard.

The American Conference of Industrial Hygienists maintains guidance values for assessing the level of contaminants in workers who are potentially exposed in occupational settings. For the monitoring of worker’s urinary inorganic arsenic levels, concentrations up to 35 mg/L are considered acceptable. Although none of the Spring Valley residents were likely exposed to inorganic arsenic through an occupational environment, this level is relevant because it is below the point at which adverse health effects are expected in a worker population. None of the 40 exposure investigation participants had inorganic arsenic levels above 35 mg/L.

In summary, the urine arsenic levels in this exposure investigation show low levels of exposure, consistent with what might be found in the general population. These levels would not be expected to cause any health problems. Only three of the individuals tested had reportable inorganic arsenic levels (10 µg/L or higher). All three of the individuals with inorganic arsenic in their urine were adults. Two of the elevated inorganic arsenic levels were from the same household. When adjusting the results using creatinine correction methods, one of the individuals with a slightly elevated result (10 µg/L) had an adjusted inorganic arsenic level (7 µg/g creatinine) below the reportable limit.

All individuals tested had total urinary arsenic between non-detect and 76 µg/L. The detection level was 1.0 µg/L. It is not clear whether the detectable levels of inorganic arsenic in the three individuals are related to soil arsenic contamination. While dietary arsenic is comprised mostly of organic arsenic, it does contain a small percentage of inorganic arsenic [7]. Dietary arsenic from a seafood meal can contribute 10–-15% inorganic arsenic to the total arsenic content [8]. The individual with the inorganic arsenic level of 14 µg/L had consumed seafood in the 3 days before testing.

Conclusions

1. Overall, urine arsenic testing showed no significant arsenic exposure in the population.

2. Three individuals had slight elevations in their urine inorganic arsenic levels.

3. These levels are not expected to cause health problems.

Recommendations

1. Individuals with mild elevations of inorganic arsenic should have follow-up urinalysis for arsenic.

2. All of the tested individuals should discuss their results with their personal health care provider.

3. Individuals, or their health care providers, can discuss their results with an ATSDR physician if they choose to do so.

Authors, Technical Advisors

Prepared by

Robert H. Johnson, MD

Medical Officer

Exposure Investigations and Consultations Branch