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PUBLIC HEALTH ASSESSMENT

TUTU WELLFIELD
ST. THOMAS, ST. THOMAS COUNTY, VIRGIN ISLANDS



ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS

The tables in this section list the contaminants of concern. We evaluate these contaminants inthe subsequent sections of the public health assessment and determine whether exposure to themhas public health significance. ATSDR selects and discusses these contaminants based upon thefollowing factors:

  1. Concentrations of contaminants on and off the site.

  2. Field data quality, laboratory data quality, and sample design.

  3. Comparison of on-site and off-site concentrations with background concentrations, ifavailable.

In the data tables that follow, the listed contaminants do not necessarily cause adverse healtheffects from exposures. Instead, the list indicates which contaminants will be further evaluatedin the public health assessment. The contaminants represent those inorganic or organiccompounds that exceed an ATSDR comparison value and will be considered further for healthimplications.



    The data tables include the following acronyms:
    CREG= Cancer Risk Evaluation Guide
    CV= ATSDR Comparison Values
    EMEG= Environmental Media Evaluation Guide
    LTHA= Life-time Health Advisory
    ppm= parts per million
    ppb= parts per billion

Comparison values used during the preparation of a public health assessment are contaminantconcentrations in specific media used to select contaminants for further evaluation. Those valuesinclude EMEGs, CREGs, and other relevant guidelines. EMEGs are media-specific comparisonvalues that are used to select contaminants of concern at hazardous waste sites. EMEGs arederived from the Minimal Risk Levels (MRLs) presented in the ATSDR Toxicological Profilesand discussed in the Public Health Implications sub-section. CREGs are estimated contaminantconcentrations based on one excess cancer in a million persons exposed over a lifetime. CREGsare calculated from EPA's cancer slope factors.

In addition to comparing the detected concentration of metals found in soils to health-based CV,it is also prudent to compare the detected soil levels to background or normal soil levels. Thistype of comparison helps identify which of the metals detected are not normal and may besite-related.

We conducted a search of the EPA Toxic Chemical Release Inventory (TRI) for the site and localarea, but TRI did not list any facilities having chemical releases in the Tutu area. The TRIcontains information on the annual estimated releases of toxic chemicals to the environment andis based upon data collected by EPA.

A. On-site Contamination

1. Waste Material

In the past, there was not an acceptable method for disposal of waste oil on St. Thomas. WAPAaccepted waste oil for fuel until June 1986 when PCB's were found in a batch of waste oil. Waste oil generators now store their own oil on-site but are not inspected or issued permits (3). Due to past poor waste containment, the potential existed for contaminants in the waste oil(gasoline, kerosene, degreasing solvents, and perhaps PCB's) to be transported to surface waterand groundwater. Numerous improper waste containments and spills have been noted atproperties comprising Tutu Wellfield NPL site. Currently VIDPNR operates waste oil collectionrepositories where waste oil is collected and then disposed of appropriately.

During a 1989 NUS Corp. site reconnaissance, numerous spills of waste oil were observed atGassett Motors (23). Waste oil was discharging from a drainage ditch on Gassett Motors ontothe adjacent Ramsey Motors Property and into a storm sewer as well. A drum disposal areacontaining 22 drums, some of which contained solvents, was found behind the CurriculumCenter (13), a previous textile manufacturing facility. Of the drums containing solvent, only onewas unsealed. Although no documentation on the contents of the drums could be found in thereports reviewed, the facility formerly (when it was the LAGA Building) used PCE extensively(13).

2. Soil Gas

Soil gas surveys of several service stations in the Anna's Retreat estate were initiated because ofthe 1987 discovery of petroleum contamination in the Tillet commercial supply well. SeveralUST's were found to be leaking. A gas chromatograph was used to define soil gas in the Tutuarea. The gas chromatograph identified total, aromatic, and chlorinated hydrocarbons (11). Thesoil gas readings were taken at depths from 2 to 9.5 feet in the subsurface. Approximately 65soil gas samples have been analyzed for total petroleum hydrocarbons in the Tutu area.

A soil gas survey was conducted at the Tutu Texaco service station (owned by Texaco CaribbeanInc.) in November 1987. Texaco's contractor, Geoscience Consultants, LTD., found significantlyelevated levels of total hydrocarbons in soil gas in the southwestern portion of the facility as wellas beneath adjacent roadways to the west and south (11). A gasoline tank containing holes wasexcavated from the property. Tanks and contaminated soil were excavated from the property inSeptember 1988. Contaminated soil was treated with a soil venting system (25).

A soil gas survey was conducted at the Esso Tutu service station in April 1988. The surveyshowed that aromatic (BTEX or benzene, toluene, ethyl benzene, and xylene) and chlorinatedhydrocarbon (DCE, PCE, and TCE) vapors are present in the subsurface soil. Total BTEX soilgas values were reported in excess of 1,000 ppm adjacent to the petroleum underground storagetanks in the southern portion of the property . BTEX soil gas readings extended to the FourWinds Plaza Parking lot (24). The Four Winds Shopping Center is located just west of Esso. DCE, PCE, and TCE were detected in soil gas in the west and southwest areas of the property(24). Hydrocarbon-contaminated soil was removed and disposed of from these locations.

In March 1994, a soil-gas survey was conducted at VIHA (18). Soil-gas samples were takenthroughout the VIHA facility (outside the building). The gas chromatograph was calibrated tomeasure trans- and cis-1,2-DCE; TCE; PCE; benzene; toluene; m-xylene; and 0-xylene. None ofthese VOCs were detected.

During the Phase II Remedial Investigation, soil gas samples were taken at the CurriculumCenter (former LAGA Building) (18). This survey helped identify and delineate the potentialsources of soil contamination at this facility. The highest VOC readings were found at the northside of the building near the location where the suspected former discharge pipe from the formerdry cleaning operation came through the building wall. Surface and subsurface soil samples were taken at the potential sources identified by the soil gas survey.

3. Soil

Soil contamination has occurred at various locations throughout the Tutu Wellfield NPL site,particularly with respect to aromatic and chlorinated hydrocarbons. Pesticides and PCB's werenot detected in soil of the Tutu Wellfield NPL site. Soil contamination is summarized in Table 1 only for surface contamination, zero to two feet in the subsurface (2,26). Soil contamination deeper than two feet was deemed inaccessible for human contact.

During the Phase I of the RI/FS process, background surface soil samples were taken todetermine what the natural occurring soil metal content is in the Tutu Wellfield NPL site (2).According to the analytical results of the background soil samples, the normal range for metals inthe Tutu Wellfield area is: antimony, 4-14 ppm; arsenic, 0.4-1 ppm; lead, <2-2.5 ppm;manganese, 535-888 ppm; mercury, <0.05-0.08 ppm; and vanadium, 40-51 ppm. According tothe U.S. Geological Survey (USGS), the normal range for metals in the eastern United States is:antimony <1-8.8 ppm, arsenic <1.1-73 ppm, lead <10-300 ppm, manganese <2-7,000 ppm,mercury 0.01-3.4 ppm, and vanadium <7-300 ppm (27). By comparing the RI/FS results (Table1) with the Tutu background levels and the range reported by USGS, it appears that none of themetals detected at Tutu are above normal background levels.

Some soil was excavated from UST areas. BTEX compounds were frequent soil contaminants. Soil contamination (beneath pavement) was found at Western Auto in the area where UST'scontaining waste oil and diesel were located. A mound of hydrocarbon-contaminated soil wasremoved at the Esso Tutu and Texaco Tutu service stations (9). Soil sampling on RamseyMotors indicated the presence of toluene, ethyl benzene, xylene, and 2-hexane (28). Theseorganic compounds were detected in samples taken at depths greater than two feet..

Surface soil was sampled at the Curriculum Center and O'Henry Cleaners. Soil contaminationwas discovered in November/December of 1992 in a pit north of the Curriculum Center. Anumber of abandoned drums were found near the Curriculum Center (9), where PCE and TCEare believed to have been dumped during past textile manufacturing. Three soil samples of thedrum area were taken at zero to two feet in the subsurface on August 14, 1992. No organiccompounds exceeding ATSDR CV's were detected. Metals such as arsenic and mercury weredetected (Table 1). Additional surface soil samples were taken during the Phase II remedialinvestigation. No organic compounds exceeding ATSDR CV's were detected. In September1988, a surface (uppermost several inches) composite soil sample taken at O'Henry Cleanersshowed 440 ppm PCE (24).

Table 1.

Maximum Contaminant Concentration in On-site Surface Soil (0-2 Feet) at the Curriculum Center at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
August 1992
CONTAMINANTMAXIMUM
CONCENTRATION
COMPARISON
VALUE (CV) FOR
INGESTION - PICA
CHILD

ppmppmSource
Tetrachloroethene
(PCE)
440*10CREG
Antimony7.3 BN 0.8RMEG
Arsenic11.60.4 CREG
Lead12.2N/AN/A
Manganese80910RMEG
Mercury0.57None---
Vanadium98.8 NNone---
NPL = National Priorities List
ppm = Parts per Million.
B = Value near detection limits.
NA = No information is available.
ND = chemical analyzed for but not detected above the instrumentdetection limit.
N = Spiked sample recovery not within control limits (i.e. error may behigh due to poor quality control).

* A composite soil sample at O'Henry Cleaners contained 440 ppm PCE. No other organic compounds in surface soil exceeded ATSDRcomparison values.

4. Sediment

Since most streams in the Tutu area are intermittent and there are no nearby lakes, sediment nearthe site is limited. Contaminants could enter sediment in Turpentine Run Creek since it is thesurface water drainage pathway for the area. Given the lack of any major surface soilcontamination within the Tutu Wellfield site (see previous discussion), it is doubtful that there would be any significant site-related sediment contamination.

5. Groundwater

Contaminated wells are located in the aquifer of the Turpentine Run Basin, Tutu Section ofAnna's Retreat (29). From July through September of 1987, EPA's Technical Assistance Team(TAT), Roy F. Weston, Inc. sampled approximately 24 drinking water wells and 123 cisternsserviced by water haulers using the Turpentine Run Basin (24). From September 1990 throughJune 1994, the Tutu Environmental Investigation Committee continued the drinking water wellsampling program started by EPA. In addition, the Tutu Environmental Investigation Committeehas installed 31 groundwater monitoring wells. Many wells were found to be contaminated withDCE, PCE, TCE, some BTEX compounds and tertbutyl methyl ether (TBME). The chlorinatedsolvents are commonly used for dry cleaning, metal degreasing, or extraction of fats and oils (9). BTEX compounds and TBME are common constituents of gasoline or other petroleum products.

There are approximately 41 drinking water wells in the Turpentine Run Basin (24). Of the 24drinking water wells sampled, 13 commercial wells and 5 private wells were ordered closed in1987 by VIDPNR. One of these drinking water wells, Tillet, was a major supplier of water to the eastern end of the island. Three out of 123 cisterns were found to be contaminated with VOCs in excess of 1,000 ppb (24).

Through August 1994, the Tutu Environmental Investigation Committee continued to conductquarterly sampling of 14 to 24 wells in the Tutu Wellfield NPL site. Groundwater has beenanalyzed for VOCs, SVOCs, pesticides, metals and cyanide (2). In March 1990, EPA issued anAdministrative Order to Esso, Texaco, and O'Henry Cleaners. The Order required them tocontinue the quarterly monitoring of the 24 drinking water wells and to truck potable water to theSteele, Harvey, and Smith residences until water connections are completed. However, otheralternatives are still being considered and the residents continue to receive trucked water.

Appendix 1, Figure 3 depicts the location of the commercial, public, institutional, and privatewells in and near the Tutu Wellfield NPL site (18). In addition, the figure also lists the latest analytical results for each of the wells.

Contaminants found in monitoring wells, commercial wells, public wells, institutional wells, andprivate wells are presented in Tables 2 through 7c. Organic contaminants are discussed firstaccording to well use. Possible inorganic (metal) contaminants are discussed separately under "f. Heavy Metals in Groundwater."

The data tables include the following qualifiers:

B = Value near detection limits.
D = Chemical identified at a secondary dilution.
E = Concentration exceeds calibration range.
J = Estimated concentration.
ND= Constituent analyzed for but not detected above the instrument detection limit.

The tables represent data collected from July 1987 through June 1994. The maximum valuesdetected are listed.

Methylene chloride was not listed in the tables because of its presence in most quality assuranceand quality control (QA/QC) blanks, indicating possible laboratory contamination. However, itwas detected at 120,000 ppb in the Harvey well and is therefore a likely contaminant in this well.

a. Groundwater Monitoring Wells

As a part of the RI/FS, the Tutu Environmental Investigation Committee has installed 31groundwater monitoring wells (21 shallow monitoring wells and 10 deep monitoring wells)during Phase I and II of the RI/FS process (2,18).

Table 2 lists the maximum concentration of organic compounds exceeding the CV's (exceptMBTE, for which no CV is available), detected in the Phase I and II groundwater monitoringwells. As will be seen in the other tables, similar organic compounds were detected in thecommercial, institutional, public, and private wells. The spacial distribution of organiccompounds indicates that there is more than one source of the groundwater contamination.

The high concentrations of BTEX and chlorinated VOCs detected at several properties indicatethat there is a moderate to high potential that light nonaqueous phase liquids (LNAPLs) andDNAPLs may exist in the groundwater aquifers at the Tutu Wellfield NPL site (18). Floatingproduct and sheens were observed in monitoring wells at the Esso Tutu and Texaco Tutu ServiceStations. This would tend to confirm that LNAPLs are present in the groundwater. In addition,several VOC compounds were detected in monitoring and drinking wells near the CurriculumCenter and O'Henry Dry Cleaners at levels that exceed 1% of the water solubility for thosecompounds. This observation would tend to indicate that VOC DNAPLs may have migrated intothe groundwater aquifer.

Table 2.

Maximum Organic Contaminant Concentrations in On-Site Groundwater Monitoring Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
October 1992 through June 1994
CONTAMINANTMAXIMUM
CONCENTRATION (ppb)
COMPARISON
VALUE FOR
INGESTION
(ppb)
COMPARISON
VALUE
SOURCE
Benzene1,0001CREG
Bromodichloromethane300.6CREG
Total1,2-Dichloroethene 2,10070LTHA
Tertbutyl Methyl Ether(TBME)6,20020LTHA
Tetrachloroethene(PCE)5900.7CREG
Trichloroethene (TCE)1903CREG
Vinyl Chloride1,3000.2EMEG
NPL = National Priorities List. ppb = Parts per Billion.


Table 3.

Maximum Organic Contaminant Concentrations in On-Site Commercial Wells in the Area of the MainPlume(s) at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
JULY 1987 - June 1994
CONTAMINANTMAXIMUM CONCENTRATION (ppb)


WELLS:

COMPARISON
VALUE (CV) FOR
INGESTION

CF1F2F3GHI1I2SppbSource
BenzeneND23.10.05J0.852.7NDND6,9501CREG
Bromodichloromethane
NDNDND
NDNDNDND0.6CREG
Total 1,2-DichloroetheneND68
J
130DJ69
DJ
213230
D
0.11
J
112,60070LTHA
Tertbutyl Methyl Ether(TBME)
3.6J
23J1709.4J
047020LTHA
Tetrachloroethene (PCE)432J71J44J7890D322,0400.7CREG
1,1,2-Trichloroethane
1JNDND
NDNDND40.6CREG
Trichloroethene (TCE)21022J1621251107113CREG
Vinyl Chloride
NDNDND
NDNDND17J0.2EMEG
NPL = National Priorities List. ppb = Parts per Billion. C = Demitri, open well. F1-F3 = Eglin 1- Eglin 2, closed wells,Eglin 3, open well. G = Four Winds No.1, closed well. H = Four Winds No.2, open well. I1 = Gassett (formerlyHarthman Bakery), closed well. I2 = Harthman Crusher, closed well. S = Tillett, closed well.


Table 4.

Maximum Organic Contaminant Concentrations in On-Site Public and Commercial Wells South or West of the Main Plume at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
JULY 1987 - June 1994
CONTAMINANTCONCENTRATION MAXIMUM (ppb)

WELLS:

COMPARISON
VALUE (CV) FOR
INGESTION

ABDE1E3ppbSource
BenzeneNDND153ND1CREG
Bromodichloro-
methane

NDNDNDND0.6CREG
Total 1,2-
Dichloroethene
ND1.41NDND70LTHA
Tertbutyl Methyl
Ether (TBME)*





20LTHA
Tetrachloroethene(PCE)NDNDND0ND0.7CREG
1,1,2-
Trichloroethane

NDNDNDND0.6CREG
Trichloroethene
(TCE)
NDNDND1.3ND3CREG
Vinyl chloride
NDNDNDND0.2EMEG
NPL = National Priorities List
ppb = Parts per Billion

West of main plume:
A = Bryan, open commercial well.
South of main plume:
B = Dede, public well, open for use by a bar.
D = Dench, commercial well, currently not operational.
E1 - E3 = Devcon 1- Devcon 3, commercial wells, open.
* No analyses were available for review.



Table 5.

Maximum Organic Contaminant Concentration in On-Site Institutional Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
JULY 1987 - June 1994
CONTAMINANTMAXIMUM
CONCENTRATION (ppb)
WELL:
COMPARISONVALUE (CV) FOR
INGESTION

T1T3ppbSource
Benzene15.3ND1CREG
Bromodichloromethane
ND0.6CREG
Total 1,2-Dichloroethene6770LTHA
Tertbutyl Methyl Ether
(TBME)*


20LTHA
Tetrachloroethene (PCE)5J20.7CREG
1,1,2-Trichloroethane
ND0.6CREG
Trichloroethene (TCE)8013CREG
Vinyl Chloride
ND0.2EMEG
NPL = National Priorities List
ppb = Parts per Billion
T1 = VIHA (Virgin Island Housing Authority) No. 1, closed well.
T3 = VIHA (Virgin Island Housing Authority) No. 3, closed well.
No data was found for T2 and T4, alternate VIHA wells.

* No analyses were available for review.



Table 6.

Maximum Organic Contaminant Concentrations in On-Site Private Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
JULY 1987 - June 1994
CONTAMINANTMAXIMUM CONCENTRATION (ppb)

WELLS:

COMPARISON
VALUE FOR
INGESTION

I3JKLNOPQRUppbSource
BenzeneNDND0.15 J0ND4.5010.08 JND1CREG
BromodichloromethaneNDNDNDND
0.5NDNDNDND0.6CREG
Total 1,2-Dichloroethene
(DCE)
2160250
DEJ
ND36 J17ND62 D180 DJ8.570LTHA
Tertbutyl Methyl Ether
2.6 J180
ND3.7 J
34377J20LTHA
Tetrachloroethene (PCE)1.22,000>10003>1000231>1000>1000160.7CREG
1,1,2-TrichloroethaneNDND5ND
NDND5NDND0.6CREG
Trichloroethene (TCE)ND350180ND123.7ND130484.33CREG
Vinyl ChlorideND3NDNDNDNDNDND4ND0.2EMEG
NPL = National Priorities List. ppb = Parts per Billion. I3 = Harthman Mango Garden, open well, secondary use. J = Harvey, closed well. K= LaPlace/Francois, open well, secondary use. L = Leonard, closed well. N = Matthias, open well, secondary use. O = Ramsey, closed well. P = Rodrigues, closed well. Q = Smith, open well, secondary use. R = Steele, open well, secondary use. U = Delegrade, closed.


Table 7a.

Maximum Inorganic Contaminant Concentrations in On-SiteGroundwater Monitoring Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
September and June 1994
CONTAMINANTMAXIMUM
CONCENTRATION (ppb)
COMPARISON
VALUE FOR
INGESTION
(ppb)
COMPARISON
VALUE
SOURCE
AntimonyND4RMEG
Arsenic9.20.02CREG
BerylliumND0.008CREG
CadmiumND7EMEG
Lead124None---
Manganese2,58050RMEG
Vanadium11030EMEG
NPL = National Priorities List. ppb = Parts per Billion.


Table 7b.

Maximum Inorganic Contaminant Concentrations in On-Site Public, Commercial, andInstitutional Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
OCTOBER 1987 - June 1994
CONTAMINANTMAXIMUM CONCENTRATION (ppb)


WELL:

COMPARISON
VALUE (CV)
FOR
INGESTION

BDF2HI1I2ST1ppbSource
AntimonyNDNDNDNDNDNDND54 BJ4RMEG
Arsenic*NDNDNDNDND15NDND0.02 CREG
Beryllium3 BJ4 BJ3 BJ3 BJ4 B3 BJ4 BJ3 B0.008CREG
Cadmium53 B115ND84 BJ4 BJ7EMEG
Lead3.7 J7.8 J2.1
BJ
8 J1.4
BJ
10.4 J2 BJ9 JNone---
Manganese53854528.528853ND1260 JND50RMEG
Vanadium**21 B28 B47 B7526BJ5254.16730EMEG
* 1987 maximum, Arsenic was ND for 1990 and 1993.
** All wells sampled, including those not listed, contained Vanadium possibly exceeding the LTHA. NPL =National Priorities List. ppb = Parts per Billion. B = Dede, public well, open for use by a bar. D = Dench,commercial well, currently not operational. F2 = Eglin 1, closed well. H = Four Winds No.2, open well. I1 =Gassett (formerly Harthman Bakery), closed well. I2 = Harthman Crusher, closed well. S= Tillett, closedwell. T1 + VIHA (Virgin Island Housing Authority) No. 1, closed well.


Table 7c.

Maximum Inorganic Contaminant Concentrations in On-Site Private Wells at the Tutu Wellfield NPL Site, St. Thomas, U.S. Virgin Islands
OCTOBER 1987- June 1994
CONTAMINANTMAXIMUM CONCENTRATION (ppb)


WELL:

COMPARISON
VALUE (CV)
FOR
INGESTION

KLNOPQRUppbSource
Antimony57 BNDNDNDNDNDNDND4RMEG
ArsenicNDNDNDNDNDNDNDND0.02 CREG
Beryllium4 B3 BJND3 B8 BNDNDND0.008CREG
Cadmium4 BJNDND3 BJNDNDNDND7EMEG
Lead2 BJ1.8 BJND3 BJ50 BNDNDNDNone---
Manganese2 BND1.4 BND12921.27 B163 B50RMEG
Vanadium*39 BJ13511.6 B45.2 B19 B4.9 b9.9 B234 B30LTHA
* All wells sampled, including those not listed, contained Vanadium possibly exceeding the LTHA. NPL = National PrioritiesList. ppb = Parts per Billion. L = Leonard, closed well. K = LaPlace/Francois, open well, secondary use. N = Matthias, openwell, secondary use. O = Ramsey, open well, secondary use. P = Rodrigues, closed well. Q = Smith, open well, secondary use. R = Steele, open well, secondary use. U = Delegrade, open well, secondary use.

b. Commercial Wells

Tutu commercial wells were used to yield water trucked to domestic users (private homes), pumped into cisterns to augment the rainwater collected from roofs, bottled and sold insupermarkets (3), and also used for industrial purposes.

Many of the commercial wells in the Tutu Wellfield NPL site area have been closed due tocontamination by organic compounds: Eglin 1 and 2, Gassett, Harthman, Crusher, and Tillett(16). The highest concentrations of organic contaminants were found in the Tillett well (Table3). Benzene, DCE, PCE, trichloroethane, TCE, and vinyl chloride concentrations exceedATSDR comparison values for ingestion of drinking water. The other commercial wells, whichwere closed, contained the same contaminants exceeding ATSDR comparison values (Table 3)and are located within the main plume(s) of contamination. The main plume(s) of contaminationis the area of contaminated groundwater within the aquifer of the Turpentine Run Basin. Basedon the concentrations of chemicals in groundwater, such as PCE, the plume extends from theVIHA to Mariendal (Figure 5). Tillett also contained tertbutyl methyl ether (TBME). The Denchwell, which is currently not operational, contained benzene exceeding the ATSDR comparisonvalue (Table 4). Some of the other contaminants were found in trace amounts. This well is located southeast of the main plume (s).

Between September 1987 and January 1988, the Tillett well was found to have PCEconcentrations that exceed the 1% water solubility of PCE in water (1,500 ppb). This would tendto indicate that DNAPLs maybe in the groundwater system that underlies the Tutu Wellfield NPLsite.

Four commercial wells within the area of groundwater contamination are still being used (18). The Ramsay, Four Winds 1 (not actively being used, but is open), and Four Winds 2 wells arebeing used by car wash companies. Water from the Four Winds 2 well is reportedly treated (anair stripper) prior to the waters use. However, no sampling data is available to indicate howeffective the treatment systems is at removing the site-related contaminants from the water. TheEglin 3 well is being used by a Laundromat and a pet store. It is reported that the water fromthese wells are not being used for drinking water or bath water. Current analytical results (Mayor June 1994) of samples taken from these wells indicate that they are contaminated withsite-related chemicals (Ramsay - 11 ppb of VOCs, Four Winds 2 - 89 ppb of VOCs, and Eglin 3 -74 ppb of VOCs).

There are other commercial wells in the Tutu Wellfield which remain open: Bryan, Demitri, andDevcon 1 & 3. These wells are located either northwest or southeast of the main plume(s) ofcontamination. Although the cistern receiving water from the Demitri well was closed byVIDPNR, it was reopened because of water rationing by WAPA during a pipe breakage. TheDemitri well, located northwest of the main plume, contains trace amounts of chlorinatedorganics: DCE, PCE, and TCE. The maximum concentration of PCE in the Demitri well, 4 ppb,exceeds the comparison value of 0.7 ppb for drinking water (Table 3). However, from September1987 through February 1991, PCE was not detected in the Demitri well (9). The Devcon wellsare commercial wells being used at Ready Mix Concrete Plant No. 1. These wells also containtrace amounts of chlorinated organics (Table 4). Devcon 1 contained a maximum benzeneconcentration of 3 ppb which exceeds the ATSDR comparison value of 1 ppb. However, itappears that the groundwater is being used for industrial rather than drinking water purposes. Analytical results of samples taken from the Dench well, also located south of the main plume,indicate that benzene is in the well above ATSDR comparison values (Table 4). This well is notcurrently in use.

c. Public Wells

A public well, Dede, is being used to serve the public in a bar. It contains trace amounts ofchlorinated organic compounds and benzene (Table 4). The contaminants in the Dede well arebelow ATSDR comparison values. The maximum concentration of less than 1 ppb PCE wasreported for August 1988 and was recorded as below detection limits for the other months fromAugust 1987 through March 1993 (9,16).

d. Institutional Wells

There are several institutional wells in Tutu Wellfield which are owned by the VIHA. VIHAwells No. 1 & 3 were closed in 1987. VIHA No. 1 contained a maximum concentration of 316ppb PCE, which exceeds the ATSDR comparison value of 0.7 ppb. Similarly, TCE and benzenemaximums also exceeded comparison values (Table 5) (16). The maximum concentration ofPCE in VIHA well No. 3 also exceeded ATSDR comparison values.

e. Private Wells

Most private homes in the Turpentine Run Basin use cisterns (mostly rooftop catchments) astheir primary drinking water source and groundwater wells for secondary purposes such aswashing, flushing, showering, and gardening. Groundwater is being used for secondary purposesfrom the Smith well, which was originally closed (18). Other wells using groundwater forsecondary purposes are Steele, Matthias, Delegrade, Harthman Mango Garden and LaPlace (18). Most of these wells have had PCE maximum concentrations exceeding 1,000 ppb (Table 6, >1,000) (16). Matthias had a maximum concentration of PCE at >1,000 ppb and TCE at 11 ppb,and subsequent sampling efforts (October 1990 through June 1994) found PCE at a maximumconcentration of 120 ppb and TCE at a maximum concentration of 12 ppb.

Because PCE has been detected in several of the private wells above the 1% water solubility forPCE (1,500 ppb), this indicates that it is possible that DNAPLs maybe in the area of thegroundwater from which these wells withdraw water.

Three private wells have been closed, Harthman Estate, Delgrade, and Harvey. PCE is theprimary organic contaminant in these wells (Table 6). The Harvey well contained consistentlyhigh concentrations of chlorinated solvents during the July 1987 through August 1988 sampling(9).

f. Heavy Metals in Groundwater

Groundwater in the Tutu Wellfield was analyzed for inorganic (heavy metal) compounds (Tables7a, 7b, and 7c) as well as the organic compounds previously discussed. This section summarizesinorganic content on a well-by-well basis (16,2,18). Most of the heavy metal appear to benaturally occurring (i.e., background levels) and not site-related.

Several metals exceeded ATSDR comparison values in groundwater: arsenic, vanadium,manganese, and cadmium. Vanadium exceeded the LTHA of 20 ppb in almost every well tested;concentrations ranged from 8 ppb to 234 ppb (Steele Well). The concentration of vanadium waslowest in the Smith well, 4.9 ppb. Both Smith and Steele are private wells which are currently inuse. Six wells contained manganese concentrations which exceeded the ATSDR comparisonvalue of 50 ppb: Dede, Dench, Gassett, Harvey, Rodriguez, and Tillett. Of these six wells, onlythe Dede well is in use. Dede is a public well, used by a local bar. Cadmium concentrationsexceeded the comparison value of 7 ppb in two wells, which had concentrations ranging from 3to 11 ppb. Both of these wells are closed.

Arsenic was detected in October 1987 in the Harthman Crusher well, now closed. TheSeptember 1990 analysis indicated that arsenic was not detectable in this well. Traceconcentrations of cyanide were detected in many wells in the Tutu Wellfield, however, they werefar below the ATSDR comparison value or any EPA drinking water standard.

6. Ambient Air

During on-site reconnaissance by the Region 2 Field Investigation Team, no areas registeredambient air quality above background readings. Volatile compounds were recorded in opendrums in a waste storage area in the garage at Ramsey Motors (28). No in-house or businessambient air concentrations were reported in the data reviewed.

B. Off-Site Contamination

Approximately 22 wells in the Turpentine Run Basin have been contaminated or have at leastone chemical which exceeds an ATSDR comparison value. The contaminant plume appears toextend to Mariendal, a town to the south of the plume source(s) or approximately a half-milefrom the contaminated wells to the north (Appendix 1, Figure 3). Since the site could consist ofmost of the Turpentine Run Basin with multiple sources and properties involved, the entire basinor Wellfield that is contaminated is considered the site. If a well is contaminated it is consideredon-site (within the plume of groundwater contamination). Therefore, no off-site contamination is presented at this NPL site.

C. Quality Assurance and Quality Control

QA/QC plans were required by VIDPNR and EPA for sampling of environmental media in theTutu Wellfield. Sampling followed EPA Guidance Publication SW-846. Sampling, removal,and cleanup plans were reviewed and approved by VIDPNR and EPA prior to implementation bythe Tutu Environmental Investigation Committee.

Standard EPA chain-of-custody procedures were required. An independent data validatory wasused (2). QA/QC samples such as equipment, field replicate, and trip blank samples were run.

Samples from the wells were also sent to EPA's Region 2 Environmental Services Laboratory fortesting. The results indicated contamination in both the wells and the sample blank for somesamples, as indicated in the tables. Those samples were not discussed in the Public HealthImplications subsection.

D. Physical and Other Hazards

A physical hazard exists on the property of the Virgin Island Housing Authority (VIHA). Thisarea contains a cistern and is accessible to both children and farm animals. The cistern has acover about the size of a manhole which was found to be open during the site visit. Children and small animals could fall into the hole and experience bodily injury.

PATHWAYS ANALYSES

To determine if residents, tourists, or other persons have been or are being exposed tocontaminants in the Tutu Wellfield NPL site, ATSDR evaluates the environmental and humancomponents that lead to human exposure. Explanations have been given in each section forclassifying the pathway as completed or potential. In general, a completed pathway includes fiveelements: a source of contamination, transport through an environmental medium, a point ofexposure, a route of human exposure, and an exposed population. A potential pathway ismissing at least one of the five elements.

A. Completed Exposure Pathways

The only completed exposure pathway is associated with groundwater. This completed exposurepathway is discussed in the following paragraphs and summarized in Tables 8 and 9. Thepresence of a completed pathway indicates that people have been exposed to contaminants in thepast, are now exposed, or will be exposed in the future.

Groundwater monitoring data clearly indicates that the groundwater within the Turpentine RunBasin is contaminated with volatile organic compounds (e.g., benzene, tetrachloroethene [PCE],trichloroethene [TCE], and vinyl chloride) and tertbutyl methyl ether (TBME). The monitoringdata also indicates that the groundwater contains heavy metals above comparison values (theselevels are probably naturally occurring). Analytical results of samples taken from the drinkingwater wells demonstrate that the contaminants and metals have migrated into many of these wells. People have used and in some cases continue to use thesecontaminated wells. Therefore, these people may have been, are currently, and/or may in thefuture be exposed to site-related contaminants.

Table 8.

Completed Exposure Pathways at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
Pathway Name/
Environmental
Media
Exposure Pathway ElementsTime (Estimated
Population)
SourcePoint(s) of
Exposure
Route of
Exposure
Exposed
Population
GroundwaterMultiplesources: servicestations, drycleaners, othersmall business.

Fromcommercial,public,institutional &private well use.

Residential homesincludingapartments in theTurpentine RunBasin, the easternportion of St.Thomas and otherisland residencesnot connected toWAPA. Aprivate bar,businesses in theTutu Wellfieldarea usingcontaminatedgroundwater, suchas car washes. Ingestion,
Inhalation,
Skin Contact
Many residentsliving inTurpentine RunBasin and othersserved by waterhaulers using thisgroundwater fromthis basin.Past (11,000)
Present (less than 15)
Future (less than 15)


Table 9.

Estimated Population - Completed and Potential ExposurePathways at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
Exposed Populations andPotentially Exposed
Populations
Affected by a Completed or Potential*
Exposure Pathway For:
LocationApproximate
Number of
Persons
Heavy Metals
(e.g., lead
and cadmium)
Chlorinated
Organic
Compounds
Aromatic
Hydrocarbons
TurpentineRun BasinResidents andBusinessWorkers inTurpentineRun Basinarea.Estimate:

11,000

GroundwaterGroundwaterGroundwater
Unknown Soil
Sediment
Food Chain
Ambient Air
Soil
Sediment
Food Chain
Ambient Air
Soil
Sediment
Food Chain
* potential exposed populations and exposure pathways areshown in italics

ATSDR has identified three separate groups of people that may have used, are currently using,and/or may, in the future, use the contaminated groundwater associated with the Tutu WellfieldNPL site. The three identified groups are: 1) people who reside in the Turpentine Run Basin anddo not obtain water from WAPA (past, present, and future exposures), 2) "Easterner's" who relyupon cisterns for their water supply and obtained water from the contaminated Tutu wells (pastexposures only), and 3) people who did not reside in the Turpentine Run Basin or the easternportion of the island and rely upon roof-top catchments and cisterns for their water supply andobtained water from the contaminated Tutu wells (past exposures only). Each of these exposuregroups are discussed below.

Anyone who obtained their drinking water from WAPA or from one of the other desalinationplants was not exposed to site-related contaminants. It is doubtful that any tourist to the islandwould have been exposed to any significant amount of site-related contaminants because thelevel of contamination at the Tutu Wellfield NPL site does not exceed any short term (acute)exposure screening levels. In addition, most of the hotels and resorts obtain their drinking waterfrom sources which were not impacted by site-related contaminants (e.g., their owndesalinization plants).

1. Turpentine Run Basin Residents and "Easterner's" - Past Exposures

In the past, Turpentine Run Basin residents and "Easterners" were exposed (ingestion, inhalation,and skin contact) to groundwater contaminants when they used water from contaminated wells inthe Tutu Wellfield for drinking. Residents were exposed to site-related contaminants not onlywhen they drank the groundwater but also when they used groundwater for the secondarypurposes (e.g., showering, bathing, cleaning, etc.). Use of water contaminated with VOC's(benzene, PCE, TCE, etc.) causes elevations in ambient air concentrations (the VOCcontaminants naturally volatilize out of the water into the air). Therefore, people inhaled thecontaminants while they used the contaminated water for showering, bathing, dish-washing, carwashing, and cloth laundering.

It is difficult to estimate how many people in the Turpentine Run Basin area and on the easternside of the island were served by contaminated-groundwater wells in the Upper Turpentine RunBasin because there are few records on its withdrawal, sale, and transport. ATSDR used thepopulation estimate derived by VIDPNR on those served by wells in the Tutu Wellfield NPL site(30,31) to obtain a rough estimate of the exposed population. Approximately 11,000 people arenot served by the WAPA desalinization plant in the Turpentine Run Basin or on the eastern endof the island and could have supplemented their cisterns part of the year with contaminatedgroundwater (32,33). Therefore, it is estimated that about 11,000 people (Table 8) were exposed in the past to site-related contaminants.

It is even more difficult to determine how long people were exposed to site-related contaminants. There are no sampling data available prior to 1987 to assist in making an estimate as to the lengthof exposure. Therefore, for the purpose of this public health assessment, ATSDR assumed thatpeople were exposed to site-related contaminants for approximately 20 years (1967-1987). Thisassumption is based upon the fact that several of the identified sources of the groundwatercontamination have been in operation for more than 20 years (e.g., LAGA Building and O'HenryCleaners, etc.). In addition, the surface soil is very thin at St. Thomas. Therefore, it would nottake very long for contaminants dumped on the ground or for material from leaking UST tomigrate into groundwater. The major premise of this assumption is that the people residedwithin the area for all of the 20 years and obtained most of their water from the contaminatedwells associated with the Tutu Wellfield NPL site. If people actually resided within theTurpentine Run Basin or the eastern portion of the island for less than 20 years or did not obtainmost of their potable water from the contaminated wells, this would significantly reduce theirexposure to site-related contaminants and, thereby, the possibility of adverse health affectsoccurring.

2. Turpentine Run Basin Residents - Current Exposures

Currently eight wells, which are known to be contaminated with site-related chemicals, are stillbeing used (18). The Ramsay, Four Winds 1, and Four Winds 2 wells are being used to washcars at two businesses. The Eglin 3 well is being used to wash clothes at a Laundromat (not fordrinking water or bathing) and at a pet store. The LaPlace, Matthias, Smith, and Steele wells arestill being used by individual homes for showering and cleaning (not for drinking water). Individuals using these wells could be exposed to significant amounts of site-relatedcontaminants which volatilize out of the water. This is particularly true for the people usingLaPlace, Matthias, Smith, and Steele wells. It is less likely the people using the Ramsay, FourWinds 1, Four Winds 2, and Eglin 3 wells would be exposed to significant amounts ofsite-related contaminants because of how and for what the water is being used for (i.e., car andclothes washing only) and because the Four Winds 1 well is reportedly being treated before thewater is used. ATSDR estimates that less than 15 people (3.5 individuals per household) arepresently being exposed to significant amounts of site-related contaminants which arevolatilizing out of the water during showering or cleaning (i.e., the four residential wells).

"Easterners" are not currently being exposed to site-related contaminants because thecontaminated commercial wells have been shut-down since 1987. Water hauling companies arenot using the contaminated wells. It is unlikely that "Easterners" will be exposed in the futurebecause the contaminated commercial wells can not be used by the water hauling companies untilthe contamination is cleaned-up

3. Turpentine Run Basin Residents - Future Exposures

In addition to the current exposure to VOCs (upwards of 173 ppb [June 1994 sample from theSteele well]), the continued use of the four residential wells (LaPlace, Matthias, Smith, andSteele) is a public health concern. The concentrations in these wells could possibly increase. The Phase II Remedial Investigation report indicates that there is a moderate to high probabilitythat DNAPLs have migrated into the groundwater aquifer from which these wells withdrawwater (18). If a DNAPL were to migrate into the residential wells, the contaminantconcentrations would increase dramatically (over 1,000 ppb). This in turn would increase theexposure people would receive when they shower or clean with the well water.

The proposed remedial plan identified by EPA would require all existing domestic andcommercial wells within the confines of the groundwater plume to be decommissioned. Theexisting unpermitted supply wells would be decommissioned by removing the pump and placinga locking cap on the well. The wells could be reestablished at some point in the future, when andif groundwater quality improves to allow extraction and use of untreated groundwater. Ifimplemented, the plan would likely require that the four contaminated residential wells bedecommissioned. This would eliminate the possibility of any future exposures to site-relatedcontaminants by Turpentine Run Basin residents.

4. Other Island Residents - Past Exposures

For people who did not reside in the Turpentine Run Basin area or the eastern portion of theisland and relied upon roof-top catchments and cisterns for their water supply it is unlikely thatthey were exposed to significant amounts or site-related contaminants. They would not haveobtained a significant amount of their water from the Tutu Wellfield NPL site. They may haveperiodically (one or twice a year) received a truck load of water from the Tutu Wellfield NPL sitewhen the water in their cistern became low due to the lack of rain. Even at the maximum levelsof contamination reported, it is doubtful that people would have been exposed to enough of thesite-related contaminants over a sufficient amount of time (i.e., continuously over many years)from one or two truck loads to exceed comparison levels. In addition, some of the contaminantswould have volatilized out of the water as the water was pumped into the cistern and while thewater sat in the cistern. Further reducing the possible exposure these people may have received.

None of the contaminated wells are currently being used by the water hauling companies. Therefore, people who reside outside the Turpentine Run Basin area are not currently exposed tosite-related contaminants nor is it likely they will be exposed in the future because the wells can not be used for commercial purposes until the contamination is cleaned-up.

B. Potential Exposure Pathways

Potential exposure pathways are indicated if exposure to a contaminant could have occurred,could be occurring now, or could occur in the future. Potential exposure pathways are discussed here and summarized in Tables 9 and 10.

Table 10.

Potential Exposure Pathways at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
Pathway Name/
Environmental
Media
Exposure Pathway ElementsTime
SourcePoint of
Exposure
Route of
Exposure
Exposed Population
Waste MaterialMultiple
sources
Drum storage or
disposal areas.
Skin Contact
Ingestion
Inhalation
Workers
Trespassers
Past
Present
Future
SoilUSTs,
spill/dump
areas
Spill areas,
Drum disposalareas
Ingestion
Skin contact
Workers
Trespassers
Past
Present
Future
SurfaceWater/sedimentGroundwater
Discharge,
spill/dump
areas
Turpentine RunSkin Contact
Ingestion
Inhalation
Turpentine Run usersPast
Present
Future
Ambient AirGroundwater,
Off-gassing
from soil
Showers,gardensInhalation
Skin Contact
Some Tutu Wellfieldgroundwater users.Past
Present
Future
Food ChainGroundwater
Soil
Private gardens,
pastures with
grazing animals
IngestionGardeners or those irrigating
with contaminated
groundwater
Past
Present
Future
GroundwaterMigrating
Groundwater
Plume
Residentialhomes, hotels,restaurantIngestion
Inhalation
Skin Contact
Some Tutu Wellfield
groundwater users
Future

1. Waste Material Pathway

Waste materials used by businesses in the Tutu area have been previously discussed in theBackground section of this assessment. Exposure to waste material could occur because of thelack of an acceptable method for disposal of waste oils on St. Thomas. Although small childrenand adults swallow small amounts of soil each day, elementary age and teen-age children whoplay at facilities storing hazardous wastes are most at risk. Dermal contact and ingestion ofwastes is possible due to inadequate drum storage of waste oil and lack of fencing at severalfacilities. Since the drum storage areas are on business properties to which the general public haslittle access, it is unlikely that children are exposed to chemicals in those waste areas. Themissing element for a completed pathway is a reasonable point of exposure.

A pool of liquid was observed behind a private residence during the site visit. It is not knownwhat the liquid contains or what the source of the liquid is. If contaminants are present, this is apotential pathway for exposure to children playing near the pool and to animals ingesting theliquid.

2. Soil Pathway

There are limited areas of surface soil contamination in the site area. The two areas of knowncontamination to-date occur on business properties to which the general public would not haveaccess: the LAGA building and O'Henry Cleaners. The missing element for a completedpathway is a reasonable point of exposure.

3. Surface Water/Sediment Pathway

There is no population using the surface water intakes or food crops irrigated within 3 milesdownstream of Tutu Wellfield. The streams in the area in general do not flow year round, andthere are no lakes. Contaminated surface water run-off and groundwater may discharge intoTurpentine Run. Given the lack of any major surface soil contamination within the TutuWellfield site (see previous discussion), it doubtful that there would be any significantsite-related sediment or surface water contamination.

4. Ambient Air Pathway

The Ambient Air Pathway is a potential exposure pathway since volatile compounds in soils (soilgas) may be released to ambient or indoor air. These contaminants could migrate to businessesand accumulate in basement or other accessible areas. Therefore, a missing element is theinformation on the levels of contaminants in ambient and indoor air. Car washes in the area arebelieved to be using air strippers to remove volatile organic chemicals from the groundwater towash cars.

5. Food Chain Pathway

The Food Chain Pathway is a potential exposure pathway since residents are using groundwaterfor the secondary purpose of gardening. However, volatile compounds are not likely tobioaccumulate in plants or animals. Heavy metals in groundwater could bioaccumulatedepending on the plant species, soil characteristics etc. There are animals such as cows and goatsin the area. However, it is unknown if pastures are irrigated with contaminated well water or if contaminated well water is used to water animals. Volatile organic compounds may accumulatein the milk of cows or goats if these animals drink water contaminated with these substances. The concentrations of metals in groundwater are so low that they are unlikely to bioaccumulateand cause excessive exposure to humans via the food chain.

6. Groundwater Pathway

Wells not affected by groundwater contaminants in the Tutu area of the Turpentine Run Basinaquifer (south/southwest of the known areas of contamination) have the potential forcontamination through migration of the plume(s).

PUBLIC HEALTH IMPLICATIONS

This section discusses the possible health effects in individuals exposed to particularcontaminants, health outcome data, and specific community health concerns. The ToxicologicalEvaluation portion of this section will discuss the possible health hazard from the past, current,and possible future exposures to the groundwater contaminants based upon studies conducted onanimals or scientific observations made from human studies.

A. Toxicological Evaluation

1. Introduction

Typically, the toxicological evaluation in a public health assessment is a comparison of theexposure dose (i.e., the amount of a substance individuals in an exposure pathway are exposed todaily) to an appropriate health guideline. Only the completed exposure pathways will bediscussed in this section.

The exposure doses for ingestion of drinking water were calculated in the following manner. The maximum concentration for a contaminant was multiplied by the water ingestion rate foradults, 2 liters per day, or children, 1 liter per day. This product was divided by the average weight for an adult, 70 kilograms (154 pounds) or for a child, 10 kilograms (22 pounds).

To evaluate non-carcinogenic health effects, the Agency for Toxic Substances and DiseaseRegistry (ATSDR) has developed Minimal Risk Levels (MRLs) for contaminants commonlyfound at hazardous waste sites. This health guideline is an estimate of a level of daily humanexposure to a contaminant below which noncancerous adverse health effects are unlikely. MRLsare developed for each route of exposure (e.g., ingestion and inhalation) and for the length ofexposure (e.g., acute, less than 14 days; intermediate, 15 - 364 days; and chronic, 365 days ormore). Because ATSDR has no methodology to determine amounts of chemicals absorbedthrough the skin, the Agency does not have MRLs for skin exposure. ATSDR presentsinformation on MRLs in its series of Toxicological Profiles on hazardous substances. Thesechemical-specific profiles provide information on health effects, environmental transport, humanexposure, and regulatory status. If ATSDR has not developed an MRL for a contaminant, theU.S. Environmental Protection Agency (EPA) Reference Dose (RfD) is used (if available). TheRfD is an estimate of the daily exposure of the human population to a potential hazard that islikely to be without risk of adverse health effects (non-carcinogenic) during a person's lifetime.

Carcinogenic risk from the ingestion of contaminated drinking water was calculated bymultiplying the exposure dose by the EPA Cancer Slope Factor (a health guideline). The resultof this calculation was then adjusted to reflect 20 years of exposure (ATSDR's worse caseestimate of exposure at this site) instead of 70 years of exposure (the normal default assumption). The actual risk of cancer is probably lower than the calculated number. The method used tocalculate EPA's Cancer Slope Factor assumes that high dose animal data can be used to estimatethe risk for low dose exposures in humans. The method also assumes that there is no safe levelfor exposure. These is little experimental evidence to confirm or refute these two assumptions. Lastly, the method computes the 95% upper bound for the risk, rather than the average risk,which results in there being a very good chance that the risk is actually lower, perhaps several orders of magnitude.

Tables 11, 12, 13, and 14 present the various health guidelines used to determine if adversehealth effects may occur and indicate whether the estimated exposure doses for the users of thevarious wells (i.e., commercial, institutional, and private) may have exceeded these guidelines. These comparisons indicate that primary contaminants of concern appear to be benzene,tetrachloroethene (PCE), trichloroethene (TCE), vinyl chloride, antimony, lead, and, vanadium.

The following information, obtained from the ATSDR Toxicological Profiles or other sources, isa general overview of these contaminants and a discussion of the scientific informationconcerning the possible health outcomes that maybe associated with the Tutu Wellfield NPL site. Only those possible health outcomes identified in Tables 11, 12, 13, and 14 will be discussed. For example: According to the information presented in Tables 11 and 12, exposure to benzenein the commercial and private well water exceeded the carcinogenic health guidelines for thiscompound. Therefore, only the scientific information concerning carcinogenic effects of benzenewill be discussed below. After the overview, the possible health effects for each of the exposuregroups identified in the Completed Exposure Pathway section of this Public Health Assessmentwill be discussed in more detail (i.e., residents of Turpentine Run Basin and the eastern portion of St. Thomas Island).

Table 11.

Comparison of Estimated Exposure Dose for Users ofCommercial Wells in the Area of the Main Plume(s) to Health Guidelines at the Tutu Wellfield National Priorities List Site, St.Thomas, U.S. Virgin Islands
ContaminantHealth Guideline (mg/kg/day)
ValueSourceExceeded by
Estimated
Exposure
Dose?
Benzene0.029*Cancer Slope
Factor
Yes
Bromodichloro-
methane
0.02Chronic MRLNo
Total 1,2-
Dichloroethene
0.3
0.02
Intermediate MRL
RfD
No
No
Tertbutyl Methyl
Ether (TBME)
0.3IntermediateMRLNo
Tetrachloroethene
(PCE)
0.1
0.01
0.052*
Intermediate MRL
Chronic RfD
Cancer Slope
Factor
No
Yes
Yes
1,1,2-
Trichloroethene
0.04IntermediateMRLNo
Trichloroethene
(TCE)
0.011*Cancer Slope
Factor
Yes
Vinyl Chloride0.00002
2.3*
Chronic MRL
Cancer Slope
Factor
Yes
Yes
* - The units for Cancer Slope Factors is (mg/kg/day)-1.


Table 12.

Comparison of Estimated Exposure Dose for Users of the Institutional Wells(Virgin Island Housing Authority) to Health Guidelines at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
ContaminantHealth Guideline (mg/kg/day)
ValueSourceExceeded by
Estimated Exposure
Dose?
Benzene0.029*Cancer Slope FactorNo
Tetrachloroethene (PCE)0.1
0.01
0.052*
Intermediate MRL
Chronic RfD
Cancer Slope Factor
No
No
No
Trichloroethene (TCE)0.011*Cancer Slope FactorNo
* - The units for Cancer Slope Factors is (mg/kg/day)-1.


Table 13.

Comparison of Estimated Exposure Dose for Users of PrivateWells to Health Guidelines at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
ContaminantHealth Guideline (mg/kg/day)
ValueSourceExceeded
by
Estimated
Exposure
Dose?
Benzene0.029*Cancer Slope
Factor
Yes
Bromodichloromethane0.02Chronic MRLNo
Total 1,2-Dichloroethene0.3
0.02
Intermediate MRL
Chronic RfD
No
No
Tertbutyl Methyl Ether
(TBME)
0.3IntermediateMRLNo
Tetrachloroethene (PCE)0.1
0.01
0.052*
Intermediate MRL
Chronic RfD
Cancer Slope
Factor
No
Yes
Yes
1,1,2-Trichloroethene0.04
0.004
Intermediate MRL
Chronic RfD
No
No
Trichloroethene (TCE)0.011*Cancer Slope
Factor
Yes
Vinyl Chloride0.00002
2.3*
Chronic MRL
Cancer Slope
Factor
Yes
Yes
- The units for Cancer Slope Factors is (mg/kg/day)-1.


Table 14.

Comparison of Estimated Exposure Dose for Inorganics in On-Site Groundwater to Health Guidelines at the Tutu Wellfield National Priorities List Site, St. Thomas, U.S. Virgin Islands
ContaminantHealth Guideline (mg/kg/day)
ValueSourceExceeded by
Estimated
Exposure Dose?
Antimony0.0004Chronic RfDYes
Arsenic0.0003Chronic RfDNo
Beryllium0.005Chronic RfDNo
Cadmium0.0007Chronic MRLNo
LeadN/AN/AN/A
Manganese0.1Chronic RfDNo
Vanadium0.003Intermediate
MRL
Yes

a. Benzene

Benzene, also known as benzol, is a colorless liquid with a sweet odor. Most people can begin totaste benzene in water at 500 to 4,500 ppb. The major sources of benzene exposure areautomobile service stations and exhaust, industrial emissions, and tobacco smoke (34). ATSDRhas not developed an oral MRL for benzene and EPA has not developed an oral RfD.

It has been established that exposure to very high concentrations (higher than the estimatedexposures that may have occurred at this site) of benzene in air can cause damage to thehematopoietic system (e.g., blood) including pancytopenia with subsequent manifestation ofleukemia (34). Numerous studies of workers exposed to benzene in the workplace haveestablished a cause and effect relationship between benzene exposure (inhalation) and acutemyeloid leukemia (34). Based upon the occupational studies and animal studies, the Departmentof Health and Human Services, International Agency for Research on Cancer, EPA, AmericanConference of Governmental and Industrial Hygienists, Occupational Safety and HealthAdministration, and the Word Health Organization consider benzene to be a human carcinogenwhen exposure occurs via inhalation at occupational levels (34).

Based on the known information about inhalation of benzene and the development of cancer, it isreasonable to assume that benzene could cause cancer in humans if ingested in sufficientquantities. However, it is not possible to accurately predict what cancers could develop as theresult of what level of exposure (dose). The risk of developing cancer after dermal exposure isprobably lower than after exposure by other routes since absorption through the skin is low (34).

b. Tetrachloroethene (PCE)

PCE is a man-made substance widely used for dry cleaning fabrics and for metal-degreasingoperations (35). Most of the studies conducted to date that evaluate whether PCE causesnon-carcinogenic effects in humans has been done at doses that exceed those that probablyoccurred as a result of the contamination from the Tutu Wellfield NPL site. The EPA chronicRfD and the ATSDR intermediate MRL are based upon animal studies that observed some formsof liver and kidney damage that may be associated with high ingestion doses (35). Both of thesehealth guidelines have a 1,000 fold safety factor incorporated into the guideline (the RfD andMRL are 1,000 times lower than levels at which the adverse health effects were observed tooccur in animals). In addition, it appears that the animals used in the studies (i.e., rodents) tendto modify PCE to a greater degree than humans do (35). It is this modification to PCE thatcauses the possible liver and kidney damage in rodents. Because the RfD and MRL have a 1,000fold safety factor and the animals used in the laboratory studies appear to be more sensitive toPCE, it is doubtful that any non-carcinogenic health effects have occurred or will occur as aresult of exposure to site-related PCE.

Some epidemiological studies of dry cleaning workers suggest a possible association betweenchronic high inhalation exposure to PCE and increased cancer risk (35). However, the results ofthese studies are inconclusive because of the likelihood that the study population was exposed topetroleum solvents at the same time, the effects of other confounding factors, such as smokingand other life-style variables, and methodological limitations in choosing control populations andmaintaining complete follow-up. A study conducted in Woburn, Massachusetts, whichattempted to correlate an increased risk of childhood leukemia with exposure tosolvent-contaminated water, has been refuted by many scientists (35). PCE has beendocumented to cause cancer (liver and kidney) in laboratory mice, but not rats, via inhalation andingestion exposures (35). However, many scientists believe that the mouse modifies PCE to agreater extent than humans or rats and it is this greater modification that contributes to the mousedeveloping cancer after being exposed to PCE. Even so, EPA, the Department of Health andHuman Services, and the International Agency for Research on Cancer have determined that PCEis possibly carcinogenic to humans (35).

c. Trichloroethene (TCE)

TCE is a nonflammable, colorless liquid mainly used as a solvent to remove grease from metalparts (36). ATSDR has not developed an oral MRL for TCE and EPA has not developed an oralRfD.

Recent information from the ATSDR TCE exposure registry indicates that participants in theregistry had elevated rates of several health outcomes (37). Approximately 4,300 people areparticipating in the ATSDR TCE exposure registry. The participants were exposed to 2 to19,380 ppb of TCE in drinking water for up to 18 years. The elevated outcomes (above thenational averages) reported to ATSDR include (for various age and sex groups) speechimpairments, hearing impairments, hypertension, stroke, liver problems, anemia and other blooddisorders, diabetes, kidney disease, urinary tract disorders, heart conditions, and skin rashes. Only the rates for strokes and impaired hearing were related to concentration of TCE. Theseresults are limited by the lack of confirmation of the health conditions and a less than completeidentification of exposure levels. These results do not establish a cause-and-effect relationshipbetween TCE and these adverse health outcomes. Additional research is needed so that it can bedetermined whether there is a relationship between TCE and the reported health outcomes.

It has been argued that occupational studies do not suggest that TCE is a potent carcinogen, giventhe enormous size of the workforce exposed to the chemical and the small number of personsexperiencing cancerous effects (36). These authors further maintain that, although TCE has beenshown to be a weak to moderate carcinogen in mice and rats, there are differences between low-and high-dose metabolism in animals and differences between species in susceptibility to cancer(similar to PCE). They suggest that humans may not change (metabolize) TCE into a carcinogen(36). In general, the associations drawn from the limited epidemiological data in humans, as wellas cancer studies in animals, are suggestive yet inconclusive. Only the EPA considers TCE to bea possible human carcinogen (36). For the purpose of this Public Health Assessment, ATSDRwill assume that TCE may possibly be associated with the develop of cancer via inhalation andingestion exposures.

d. Vinyl Chloride

As a pure product, vinyl chloride is a colorless gas at normal temperatures. Most people begin totaste vinyl chloride in water at 3,400 ppb (38). All vinyl chloride is manmade or results from thebreakdown of other manmade substances, such as PCE and TCE (both have been found at theTutu Wellfield NPL site).

Studies of workers and animals exposed to very high levels of vinyl chloride have indicateddamage to their liver, lungs, and kidneys (38). The chronic oral MRL is based upon two animalstudies that found that liver damage (increased incidence of basophilic foci of cellular alteration)occurred in rats when they were exposed to 0.018 milligrams of vinyl chloride per kilogram ofbody weight per day (mg/kg/day) (38). Although the estimated amount of vinyl chloride ingestedby people from drinking water slightly exceeded the chronic oral MRL, no adverse health effectsat that amount have been reported in the literature. It is important to remember that the chronicoral MRL has a 1,000 fold safety factor built into it (i.e., the observed liver damage occurred inthe rats at a level 1,000 times above the MRL level). Animal studies do not report adverse healtheffects after ingestion of vinyl chloride at the amount estimated to have occurred from this NPLsite. Therefore, it is not anticipated that any non-carcinogenic health effects would occur becauseof exposure to vinyl chloride.

Results from several studies suggest that breathing air or drinking water containing low levels ofvinyl chloride over many years may increase the risk of getting cancer (38). Studies of workerswho have breathed very high levels of vinyl chloride over many years developed more livercancers than would be expected (38). Long-term animal studies show that increases in livercancer occur when the animals are fed low levels of vinyl chloride. The Department of Healthand Human Services has determined that vinyl chloride is a known carcinogen (38). TheInternational Agency for Research on Cancer has determined that vinyl chloride is carcinogenicto humans, and EPA has determined that vinyl chloride is a human carcinogen (38).

e. Antimony

Antimony is a silvery white metal of medium hardness that breaks easily. To make it stronger, alittle antimony is usually mixed with other metals such as lead and zinc to form alloys (0, 0, 40). Antimony is found at very low levels in the environment, and food usually contains smallamounts of this metal. The average concentration of antimony in meats, vegetables and seafoodis 0.2 - 1.1 ppb.

Although the estimated exposure dose of antimony is greater than the RfD (0.0004 mg/kg/day)for this metal, the calculated dose is not high enough to cause any adverse health effects fromingestion. A safety factor of several orders of magnitude is incorporated into the RfD. Therefore, ATSDR does not believe that any adverse health effects will occur from the exposureto antimony in drinking water.

f. Lead

ATSDR has no MRLs and EPA has no RfDs for lead, but ingestion of lead can lead to adversehealth effects, especially for infants and young children. Lead ingestion is also harmful for unborn children as they can be harmed during fetal development, and for pregnant women andwomen of childbearing age (41). Lead can not be easily absorbed through the skin and does notvolatilize out of water.

Lead contamination in one private well was greater than EPA's Action Level (guideline for leadin drinking water ) of 15 ppb for public water supplies (i.e., the Rodrigues well, 50 ppb). However, this was a one time measurement. Lead was not detected in this well or any other wellused for drinking water above the EPA Action Level at any other time. Therefore, ATSDR doesnot believe that any adverse health effects will occur.

g. Vanadium

Vanadium is a natural element in the earth, and is present in the human body (42). Most of thedrinking water wells within the Tutu Wellfield contained vanadium and the estimated amount ofexposure ingestion is slightly greater than the intermediate MRL of 0.003 mg/kg/day. However,a safety factor of several orders of magnitude is incorporated into the MRL. Therefore, noillnesses are expected for people ingesting water containing vanadium at the levels reported inTable 7.

2. Residents of Turpentine Run Basin and the Eastern Portion of St. Thomas

ATSDR has determined that the commercial and residential wells in the area of the main plumeare contaminated with a number of VOC chemicals (see Table 3 through 6). The commercialwells were used to generate water for sale to the private and public sectors. Although most of thewells listed in Table 3 through 6 are now closed, past exposure has occurred, particularly forusers of water supplied from the Tillet well which had the highest concentration of contaminants. As discussed in the Completed Exposure Pathway section of this Public Health Assessment, thepeople that may have been exposed to site-related contaminants for a significant amount of time(e.g., greater than 10 years) were people who relied upon hauled water (i.e., residents ofTurpentine Run Basin and the eastern portion of St. Thomas island) or private residential wells as their primary drinking water supply.

The combined exposure to benzene, PCE, TCE and vinyl chloride at the estimated exposureamounts could result in a theoretical moderate increased risk of developing cancer. In addition tothe ingestion route of exposure, people were exposed to those carcinogens through inhalation. Exposure to contaminants through both ingestion and inhalation may increase the chances ofcancer in people who used water from the contaminated wells in the past. This determinationassumes that the primary water supply for a significant amount of time (e.g., greater than 10years) came from the contaminated wells. If people did not obtain most of their water from thecontaminated wells for a significant time or did not reside within the Turpentine Run Basin or theeastern portion of St. Thomas island for a significant amount of time, they would not have amoderate increased risk of developing cancer.

The LaPlace, Matthias, Smith, and Steele private wells are reportedly used for secondarypurposes, but the potential exists for use of those wells for potable purposes. The presence ofbenzene, PCE, TCE, and vinyl chloride in those wells may slightly increase the potential fordeveloping cancer. The recent information from the ATSDR TCE exposure registry alsoindicates that there may be the possibility of other adverse health effects (e.g., strokes andimpaired hearing) associated with TCE exposure (37).

Although the estimated exposure doses of the compounds listed in Table 12 are not expected tocause adverse health effects if ingested (aside from a slightly increased risk of cancer), some ofthe wells are presently used for secondary purposes including showering, bathing, washingclothes and washing cars. Reports in the literature have indicated that significant exposure toVOCs can occur from inhalation, particularly from showers (39). An individual may be exposedto VOCs through inhalation at levels comparable or greater than those estimated for ingestion. There is a concern that the levels of benzene, PCE, TCE, and vinyl chloride in the LaPlace,Matthias, Smith, and Steele wells (Table 6) could possibly lead to adverse health effects becauseof exposure from breathing benzene, PCE, TCE, and vinyl chloride that evaporated to indoor airduring showers. The concentration of these contaminants could possibly increase if a DNAPLmigrates into these active wells. However, our knowledge is limited when it comes to estimatingexposure from VOCs released during showers. The human toxicities from exposure to thesechemicals at the same time is also not known.

Although the maximum concentrations found in the VIHA wells of benzene, PCE, TCE, vinylchloride exceed their comparison value for ingestion, the estimated exposure doses for thosecontaminants, and the remaining contaminants listed in Table 5 are lower than the healthguidelines. As long as these wells remain closed, residents of the VIHA development exposureto contaminants at the estimated dose should not cause adverse health effects.

B. Health Outcome Data Evaluation

Health outcome data were not evaluated for this site because no previous health studies on thepopulation around the site were identified during the gathering of data and information for thisPublic Health Assessment. In addition, the Virgin Islands do not have a centralized cancerregistry which could have possibly been used to determine if the occurrence of cancer near theTutu Wellfield NPL site is more than would be expected.

C. Community Health Concerns Evaluation

The community health concerns identified earlier are addressed as follows:

1. Is leukemia the only type of cancer likely to be increased from exposure?

Response

Analytical results of samples taken from wells that provided drinking water to people indicatethat the water is contaminated with benzene, tetrachloroethene, trichloroethene, and vinylchloride. Scientific studies of workers and animals exposed to very high levels (higher than whathas been found at the Tutu Wellfield National Priorities List Site) of these contaminants overmany years had more liver and kidney cancer and leukemia (depending upon which of thecontaminants exposure occurred to) than would normally occur. Therefore, it is theoreticallypossible that people exposed to site-related contaminants may have an increased risk ofdeveloping these three cancers. Because the exposures that may have occurred to site-relatedcontaminants is lower than what was experienced in these studies, ATSDR used a theoreticalmethod to estimate the possible cancer risk associated with exposure to site-related contaminants. This method computes the 95% upper bound for the risk, rather than the average risk, whichresults in there being a good chance that the risk is actually lower. The actual risk of cancer isprobably much lower than predicted. Therefore, it is possible that no cancers may occur eventhough people were exposed to contaminants we believe have the capability to cause cancer inhumans.

2. Were health records/data examined to determine whether there is a higher incidence of cancer in the St. Thomas population than other areas?

Response

There are not any data bases or previous health studies available that could be used to determinewhether the incidence of cancer in the St. Thomas population is higher than would be expected. Therefore, ATSDR was not able to answer this question with this Public Health Assessment.

One way of trying to answer this question is to conduct an epidemiologic study. However,ATSDR does not believe that it is scientifically possible to conduct a epidemiologic study at thissite because no records are available to determine who received trucked water from thecontaminated wells. Therefore, a study done at this site would have a major bias (flaw) becausewe would not know whether the people identified in the study were really exposed. In addition,U.S. Census data indicates that the population at St. Thomas is some what transient. This wouldmake it very difficult to find the appropriate people to include in the study. In addition, if thepeople did not reside or consume contaminated water for more than 10 years, their risk ofdeveloping cancer would be less than predicted in this Public Health Assessment. (Note:ATSDR Public Health Assessments evaluate the information available concerning a NPL site ordischarges to the environment. Epidemiologic studies are not conducted during a Public HealthAssessment.)

3. How can I prevent exposure to site-related contaminants?

Response

Presently the only people who may be exposed to site-related contaminates are those individualswho are still using contaminated private wells for secondary uses (e.g., showering, bathing,cleaning, etc.). ATSDR recommends that these people stop using the well water inside theirhomes.

All of the contaminated commercial wells that were used to truck water to people have beenclosed. Therefore, no one is being exposed to site-related contaminants via trucked water.

4. Will a health study be conducted to determine if the incidence of cancer is higher than what would be expected?

Response

ATSDR is not recommending that a health study be conducted at this site because it would bevery difficult to identify a large enough exposed population. No records are available todetermine who received the contaminated water. In addition, the population within the UpperTurpentine Run Basin and the eastern portion of the island (the areas most likely to have receiveda significant amount of contaminated water) are fairly transient. This means that those peopleprobably did not receive contaminated water for a significant amount of time (greater than 10years) which is thought to be needed in order to increase the chance of getting cancer.

ATSDR is conducting various health studies (e.g., the ATSDR Trichloroethene ExposureRegistry and the ATSDR Benzene Exposure Registry) at other sites where it is known how longpeople were exposed to similar concentrations of contaminants. These studies do not have thedesign flaws that a study conducted at the Tutu Wellfield NPL site would have. Hopefully thesestudies will help ATSDR and the scientific community better understand what the true cancerrisks related to these contaminants are.



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