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Objective

The Department of Public Health (DPH), Commonwealth of the Northern Mariana Islands, requested ATSDR to participate in their exposure investigation of residents of Tanapag Village, on the island of Saipan. Specifically, this consultation evaluates and interprets serum polychlorinated biphenyl (PCB) levels from the exposure investigation.

Background

Tanapag Village is located on the northern half of the island of Saipan in the Commonwealth of the Northern Mariana Islands. The village covers 1.2 square miles and has about 1800 residents. The vast majority of the residents are of Chamorro and Carolinian descent. Tanapag Village is on the western shoreline of Saipan, with the topography of the village moderately sloped from east to west toward the ocean. Elevation of the village ranges from sea level to about 12 feet above mean sea level (1).

In the 1960s, electric capacitors from surplus military equipment were brought to Saipan and stored at the Department of Pubic Works storage yard just south of the village. In 1972, the capacitors were reportedly moved into the village where they were used to form a perimeter around the ballpark and community hall area. Some of the capacitors subsequently leaked and contaminated the soil with PCBs. Levels were reported up to 23,000 mg/kg of soil (1) and there was no remediation at this time. In 1988-1989, the Department of Environmental Quality (DEQ) removed 53 capacitors from Tanapag Village. After the EPA determined that the capacitors had originated from the U.S. Army installation at Kwajalein in the Marshall Islands, the Army accepted responsibility for the remediation under the Formerly Used Defense Sites (2). 

In 1992-1993, additional site characterization was performed, and contaminated soil and capacitor debris was packaged and removed from selected sites in Tanapag Village, mainly Cemetery #2 and the Department of Public Works storage yard (1). Cemetery #2 is located midway between Tanapag Village and the Department of Public Works storage yard. The U.S. Army Corps of Engineers (USACOE) undertook remediation in the village at this time and Phase II of cleanup was completed in August 1999. In October 1999, in a public meeting held in Tanapag Village and attended by multiple federal and local agencies, the village residents and representatives of the CNMI expressed several concerns: the USACOE’s time line to complete the remediation, the adequacy of the cleanup levels established by USACOE, the likelihood of ongoing exposure, and the safety of foodstuffs. The residents also requested health evaluations to address possible adverse health effects and possible linkage to PCB exposure. EPA was also requested to put the site on the National Priority List (NPL) (2). 

In February 2000, ATSDR began a Public Health Assessment at Tanapag Village. In April 2000 the Exposure Investigation Section was invited to assist the CNMI Department of Public Health (DPH) in conducting an exposure investigation for PCB exposure. The CNMI Secretary of Health and his staff developed the exposure investigation protocol and included a comprehensive screening and health care plan to address the many health issues expressed at Tanapag. ATSDR staff assisted the DPH in conducting the exposure investigation (EI) in May and June of 2000.

Methods

 The CNMI Department of Public Health invited residents of Tanapag to participate in the EI. A clinic facility was opened in the Village to conduct this screening. The clinic was open five days each week for most of May and June of 2000. Over 1220 individuals were interviewed, examined, and offered blood testing. The screening consisted of an exposure questionnaire, a brief medical history and physical exam, a blood test for total serum PCBs, and a battery of health screening tests.

Target Population and Recruitment:

Any individual who currently resides in the village, or has lived in the village for greater than one year in the past, was invited to participate in the EI. Prior to conducting the EI, ATSDR staff conducted a public meeting to answer residents’ questions about the EI.

PCB Exposure Questionnaire: 

The exposure history questionnaire was designed to identify the residents who are most likely to have been exposed to PCBs. These individuals could include (1) residents who live in close proximity (1/4 mile or less) to a known PCB contaminated area, (2) people who engaged in activities that could lead to exposure, e.g., digging graves, gardening, or playing in contaminated areas, (3) people who had direct contact with leaking fluid from a capacitor or transformer, and (4) people who ate local animal foodstuffs, such as fish, crabs, chickens or eggs from chickens that had access to a known PCB-contaminated area. Specific questions addressed the person’s residential history, occupational history, and dietary habits. The questionnaire also included many questions about the general health status of individuals. ATSDR provided qualified staff to assist DPH staff in collecting the exposure histories. 

Consent and Confidentiality: 

Each adult and a parent or legal guardian of each minor participant was required to sign an informed consent/assent form, prior to testing. Confidentiality was protected in accordance with Federal and Commonwealth laws. 

PCB Analysis:

A 10 ml tube of blood was drawn from each individual participating. After clotting and spinning, 4 ml of serum was sent to National Medical Services laboratory for analysis of total PCBs by high resolution capillary gas chromatography. Serum lipids were measured and used to interpret results for individual patients; however, total PCB results as listed below are not lipid adjusted.

Results:

The arithmetic mean serum PCB level for this population was 2.0 mg/L (ppb) with a 95% upper confidence level of 5.7 mg/L (ppb). A value of one half the detection level was used for all reported non-detects. Attachment 1 illustrates the distribution of serum PCB concentrations found in this EI. Of the1059 individuals who had PCB results reported from the lab, 892 had non-detectable (< 3 ppb) levels. Another 152 individuals had levels between 3 and 9.9 ppb, 9 had levels between 10 and 19.9, and 6 had levels greater than 20 ppb. The highest level was 36 ppb. 

Discussion

 Based on the results of this exposure investigation, it does not appear that the population tested in Tanapag Village are being exposed to PCBs at levels of health concern (3). Although we do not have a reference population specific to Saipan, the Division of Laboratory Sciences at the National Center for Environmental Health, Centers for Disease Control and Prevention considers a level up to 5 ppb as a “non-exposed” level. (4) The Tanapag population tested tended to have slightly increasing serum PCB levels with increasing age. This is similar to findings at most sites, and reflects a gradually increasing body burden of PCB with age. No children or young adults (up to age 30) had detectable levels of PCB (< 3 ppb), so it appears that no unusual exposure has taken place during the past several years.

 It is not possible to predict whether there was completed exposure to PCBs in capacitor fluid or contaminated soil in past decades.

 The serum PCB level was chosen as the appropriate biomarker at this site. Sampling of serum is less invasive, less prone to complications (e.g. infection, scarring), and less expensive than adipose tissue sampling. Serum PCB levels correlate well with levels found in adipose tissue and are accepted as being very reflective of PCB exposure.(5) 

There has also been some concern expressed as to why Aroclor 1260 was used as the standard in the laboratory analysis of the serum, rather than Aroclor 1254. Aroclor 1260 is often used as the standard when congener-specific gas chromatography is not done because it has a congener profile similar to typical serum PCB congeners in the general population. It is our determination that the analysis that was performed using the Aroclor 1260 standard would provide an accurate and reliable analysis for total serum PCBs. 

Conclusions

1. The residents of Tanapag Village who were tested in this exposure investigation have levels of PCB in their serum which would not be expected to cause health effects, and do not indicate elevated exposures.
2. The methodology used in this exposure investigation is appropriate and reliable.

References

1. Baylor, KJ. Field Sampling and Analysis Plan. PCB Multi Matrix Survey. Draft. Tanapag, Saipan, CNMI. 2000, March 10. Resource Conservation and Recovery Act Corrective Action Office. San Francisco, California. U.S. Environmental Protection Agency, Region 9.
2. U. S. Army Corps of Engineers. Tanapag Action Plan. Draft. March 15, 2000.
3. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Polychlorinated Biphenyls (Draft). Atlanta: US Department of Health and Human Services; June 1995.
4. Active Methods List, Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, updated 2/12/2001.
5. Dekoning EP, Karmaus W, 2000. PCB exposure in utero and via breast milk. A review. J Expo Anal Environ Epidemiol 10:285-293. 

This page last updated on August 20, 2001

Contact Name: Maria Gosa/mjg4@cdc.gov

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