HEALTH CONSULTATION ADDENDUM
BURNING GROUND AREAS AT
WOMPATUCK STATE PARK
In the November 1997 sampling episode, EPA collected four sediment samples, three surfacewater samples, one drinking water sample, and seven surface soil samples. These samples wereanalyzed for semivolatile organics and explosives. Table 1 summarizes this data. The compoundsand concentrations detected in the analysis are summarized in Tables 2 through 4. From theanalysis, PAHs, phthalates, and few other semivolatile organic compounds were found in soil andwater samples at low concentrations.
To decide if a public health hazard exists, ATSDR compared the results with U.S. EPA Region 3's health-based screening values as shown in Tables 2 through 4 and considered the likelyscenarios for public exposure. ATSDR also considered the derivation of the screening values thatare based on 30 years of exposure for at least 250 days per year (an industrial scenario becausethe area is not a residential neighborhood).
The reported concentrations were below the screening values in all samples except the following:
- Sample WP108 had a benzo[a]pyrene soil concentration of 1.2 milligrams per kilogram (mg/kg) (estimated value below calibration range) and the screening value was 0.78 mg/kg. Because the screening value is based on 30 years of exposure, 250 days/year and the sample location is in a fenced area restricting public access, this soil concentration does not present an apparent public health hazard.
- In nine of the 16 samples collected in November 1997, the lab detected a variety of tentativelyidentified compounds (TICs). The lab also identified TICs in the blank sample. While the labreported most the TICs as unknown, four TICs were identified by the laboratory in theenvironmental samples: 9-10-anthracenedione; benzeneacetic acid; 1,1'sulfonylbis-4-chlorobenzene; and carbethoxyethylidine triphenylphosphorane. U.S. EPA's Risk AssessmentGuidance for Superfund (U.S. EPA 1989) recommends not evaluating TICs if the estimatedconcentrations are low, are present in small numbers compared with other chemicals detected,and if no historical or other site information indicate that the TIC is present at the site. If TICsare evaluated, it presents a challenge because (1) there is a large amount of uncertainty in theidentity and concentration of the compounds as they are based on a mass spectral library searchwithout internal standards and (2) toxicity data for these compounds are often limited. Withthis uncertainty in mind, ATSDR evaluated the identified TIC compounds and determined theydo not present an apparent public health hazard. Our evaluation follows:
- Sample WP108 had a 9,10-anthracenedione soil concentration of 1.6J mg/kg (J=estimatedquantity). A screening value for this compound is not available. 9,10-Anthracenedione isin a class of semivolatile organic compounds called polycyclic aromatic hydrocarbons(PAHs). Although a screening value is not available for this compound, ATSDR assumedits toxicity to be as great as the most toxic PAH, benzo[a]pyrene with a screening value of0.78 mg/kg. Because the screening value is based on 30 years of exposure, 250 days/yearand the sample location is in a fenced area restricting public access, this soil sample withthis concentration does not present an apparent public health hazard. - Benzeneacetic acid (or more commonly know as phenylacetic acid) was found in samplesWP101 (water) and WP113 (soil) at 5J µg/L and 12J mg/kg, respectively. A screeningvalue for this compound is also not available. Phenylacetic acid occurs naturally inJapanese peppermint oils and rose oils and is used in the production of perfumes andpenicillin. Toxicologic data on this compound is limited to several LD50s (1500 mg/kg to2300 mg/kg) and one nonlethal oral exposure study (450 mg/kg). The concentrations inthese studies were 1000 to 20,000 times greater than expected human doses. Comparedwith other compounds, the LD50s are considered "slightly toxic" (University of Nebraska-Lincoln 1997 and University of Florida 1996) but these LD50s do not necessarily representother health effects that are unknown. Regardless, ATSDR concludes that this compounddoes not present an apparent public health hazard because of the low concentrations,relative low toxicity, low expected doses, and improbable exposures expected from themedia and the locations sampled. - 1,1'-sulfonylbis-4-chlorobenzene (SCB) was found in the water sample WP100 at 24Jmg/kg. EPA collected sample WP100 from Mount Blue Spring. The local public usesthis spring for a drinking water source by filling containers for use elsewhere. SCB is apolymer approved by the FDA for use in reusable food containers. Limited toxicity datawere available to ATSDR on this compound. The National Institute of Health (1991)reports an LD50 on mice (oral) at 24 grams per kilogram (gm/kg) and a QuantitativeStructure-Toxicity Relationship (QSTR) model predicts a rat LD50 of 2.3 gm/kg (HealthDesigns 1998). On a relative scale, these LD50s are considered "moderately toxic"(University of Nebraska-Lincoln 1997) or "slightly toxic" (University of Florida 1996)similar in LD50s to common table salt, morphine, and silvex. One can only use theserelative LD50s as a general guide and they do not necessarily represent other nonlethalhealth effects that are unknown.
The QSTR model also predicts potential developmental toxicity at a Lowest-Observed-Adverse-Effect Level (LOAEL) dose of 104 mg/kg. This concentration is approximately100,000 times greater than expected human doses.
ATSDR concludes that this compound does not present an apparent public health hazardbecause of (1) FDA's determination, (2) the relative LD50s, (3) the high LOAEL, and (4)the assumed lower frequency of ingestion from this water compared to tap water deliveredinstantaneously at one's home.
- Carbethoxyethylidine triphenylphosphorane (CT) was found in water samples WP100 andWP102 at 12J and 6J µg/L. WP100 is located at Mount Blue Spring and WP102 islocated at a pond upgradient of the site. CT is used as a chemical intermediary (Stewart,1997). Toxicologic data for CT is not available (Fisher-Scientific 1991). ATSDRattempted to evaluate CT's toxicity through the QSTR model but the evaluation was notpossible because part of the molecule was not represented in the QSTR database.
As a result, we are unable to evaluate the exposure hazard to this chemical. However, thiscompound probably does not present a health hazard at 12 J µg/L because thisconcentration falls within typical ranges used by EPA as maximum contaminant levels(MCLs) for organics in drinking water. Additionally, these MCLs assume regularconsumption of the water. Because the spring water is not used as frequently as tap waterdelivered instantaneously to one's home, the lower frequency of using the spring watermeans that a lower health risk occurs. Therefore, this chemical probably does not presenta health hazard.
Lastly, because CT was found in a hydraulic, upgradient, sample location and in MountBlue Spring, but not onsite (during the April and September 1997 sampling), thiscompound probably did not originate from the site. Instead, CT may be naturallyoccurring, a result of contamination from the sampling and analysis procedures, or fromanother source.
When comparing the April 1997 data with the September 1997 data, ATSDR identified manymore TICs in the April 1997 data because the detection limits were 100 times lower. Theconcentrations of TICs in the April 1997 data were below 7 mg/kg in soils and below 20 µg/L forwater. ATSDR did not evaluate the TICs from the April 1997 data because of the challenges inevaluating TICs, as discussed previously. Additionally, because of the sample locations, exposurewould be infrequent, if it all. We did, however, evaluate the TICs in the water samples fromMount Blue Spring because of its use as a drinking water supply.