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PETITIONED PUBLIC HEALTH ASSESSMENT

ROCK AVENUE 21-E DUMP
WINCHESTER, MIDDLESEX COUNTY, MASSACHUSETTS


DISCUSSION

Methods

ATSDR reviewed the surface soil data provided by the Environmental Protection Agency (EPA), Region I, to evaluate the extent to which area residents might have been exposed to potentially contaminated surface soil [3,4] .

In this evaluation, ATSDR considers how people might come into contact with the contaminants. This process is described in greater detail in Appendix B. ATSDR uses a sequential process of reviewing the available environmental data. If the concentration of detected chemicals in a specific media is less than the comparison value, the exposure is not of public health concern and no further evaluation is conducted. If the concentration is greater than the comparison value, any exposure is selected for further public health evaluation to determine any adverse health effects. If a chemical does not have a comparison value, ATSDR reviews the scientific literature to determine if the exposures are of health concern. Six potential exposure pathways were identified at the Rock Avenue Dumpsite after evaluation of the existing environmental data. These potential pathways were evaluated as to whether they represent a public health concern. (A summary of these evaluations are presented in Appendix A, Table III).

Surface Soil, Sediment, and Dusts

Surface soil samples were collected at a depth of 0 to 3 inches at 9 sampling stations on-site and 2 sampling stations at a nearby residence. (See Figures 2A and 2B in Appendix A for sampling locations). All samples were analyzed for volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), pesticides, asbestos, and metals. (A list of the contaminants detected are presented in Tables I and II in Appendix A).

Most of the contaminants detected were PAHs and were at levels typical of those reported in urban environments or rural environments. ATSDR considered potential exposures by dermal contact, inhalation of volatiles, incidental ingestion, and plant uptake. ATSDR concluded that because the concentration of contaminants (including metals, PAH's, and petroleum hydrocarbons) in the soil did not exceed ATSDR comparison values, reported levels in surface soil, sediments, and dusts are not a health hazard to community members by the route of exposures addressed.

PAHs are ubiquitous in soils. Incomplete combustion is a major source of PAHs in soils in the United States and worldwide; concentrations have tended to increase over the last 100 to150 years, especially in urban areas [6] . ATSDR compared the levels reported in surface soil at the site with reported soil background levels in United States [7]. Generally, levels at the dump site (0.04 to 21.0 milligrams per kilogram [mg/kg]) were below or consistent with reported urban levels (0.22 to 166.0 mg/kg). Levels in residential soils (0.06 to 0.4 mg/kg) were consistent with reported rural levels (0.0003 to 1.3 mg/kg). Soils from the dump site contained some chemicals that were not detected in residential samples. Herbicides (DDT and DDE) were detected in residential soils, but not in the dump site soil.

Dermal exposure for PAHs was not expected to add significantly to the total exposure when absorption is not more than 10 percent [17]. Estimated permeation after 24 hours was only 3 percent of the total benzo(a)pyrene applied by direct contact to human skin, suggesting that substantial metabolism or binding, or both, takes place which limits the amount available to penetrate the skin into the systemic circulation [10]. The duration of exposure at the site would be expected to be much less.

Volatilization from soil was not considered as a significant health concern because of the low concentration of PAHs, the affinity for moderate to strong adsorption to organic material, and the limited number of low molecular weight PAHs reported (the most likely to volatilize). Generic fugitive dust soil screening levels for semivolatile organics are several orders of magnitude higher that the corresponding generic ingestion soil screening levels [16].

ATSDR screened the soil analytes for chemicals of concern by comparing the level of each contaminant with the level at which health effects would not be expected from incidental ingestion. Only one PAH, benzo(a)pyrene, exceeded comparison values for incidental ingestion for cancer, as did all pesticides (chlordane, DDD, and DDT). Contaminants of concern were further evaluated as described in the following text. Comparison values were not available for all contaminants and contaminants without comparison values were evaluated using a toxic equivalency factor (TEF) approach, which did not identify any contaminants of concern [8, 9].

While benzo(a)pyrene is classified as a probable human carcinogen, human data specifically linking benzo(a)pyrene to a carcinogenic effect do not exist. However, there are multiple animal studies in many species demonstrating carcinogenicity by numerous routes at high doses [11].

ATSDR concluded that there was no apparent increase in the risk for developing cancer from oral exposure to the maximum reported residential soil concentration of benzo(a)pyrene using an age-adjusted incidental ingestion exposure scenario. Likewise, exposure to chlordane, DDD, DDE, and DDT did not indicate an apparent increase in risk for developing cancer.

Biota

The extent of uptake of PAHs by garden plants would depend on many factors, including the molecular weight, concentration, and solubility of the specific PAH, and the plant species [12]. In general, the higher molecular weight PAHs tend to adsorb to the leafy surface of the plant or root and are not likely to be found internally in higher concentrations. Above-ground plants tend to have higher concentrations than below-ground plants and broad-leaf plants have higher concentrations than thin-leaf plants [8]. The lower molecular weight PAHs would be more likely to be bioconcentrated.

The uptake of PAHs from soil to plants and the subsequent biomagnification is generally quite low [14]. The ratio of the concentration of PAHs in vegetation to those in the soil have been reported to range from 0.001 to 0.18 for total PAHs and from 0.002 to 0.33 for benzo(a)pyrene [12]. Therefore, accumulation of PAHs by plant uptake from soil would not be expected and are not a health hazard.

Soil Gas - Indoor Ambient Air

As discussed in ATSDR's 1998 health consultation, past soil gas monitoring revealed the presence of elevated methane concentrations at the Rock Avenue property perimeter greater than 10 percent of the LEL [2]. The presence of methane on site at concentrations ranging from non-detect to 24,550 parts per million (ppm) (or approximately 50 percent of the LEL) did not present an imminent health hazard, but the uncertainty relative to the source and the extent of methane in soil gas was of concern. Only two air monitoring samples existed: one from the petitioner's basement and one from the basement of another nearby resident. Naphthalene or other PAHs were not found in the petitioner's basement, and methane was not detected at levels that presents a public health concern. To date, however, no controls or follow-up soil gas monitoring have been conducted at the Rock Avenue Dumpsite. Although no methane was detected on neighboring property at levels that posed a public health hazard, off-site methane data were limited to one soil gas sample, and two air monitoring samples. Soil gas, therefore, could not be eliminated as a potential source of contamination that might migrate to ambient indoor air and lead to an explosion.

Extent of Contamination and Public Health Implications

Adverse health effects are not expected from exposure to contaminant levels found in the surface soil at the dumpsite and residential sites. The potential for contacting contaminants at concentrations associated with adverse health effects is limited. It is, therefore, doubtful that exposure to surface soil either via ingestion of or dermal contact with surface soil would present a public health hazard. If soils were disturbed in the future (e.g., new construction), further evaluation of the nature and extent of disturbed soil contamination would be warranted.

Although no dangerous methane concentrations were observed in nearby residences, elevated methane concentrations were detected in soil gas at the perimeter of the site [2]. Methane remains a potential explosive hazard.

Community Health Concerns

Area residents expressed concern about contamination being blown off the site by the wind (fugitive dust), contaminating residential gardens, and causing adverse health effects from inhalation and dermal contact. It was unlikely that area residents would experience adverse health effects associated with fugitive dusts or dermal contact with the contamination because, (1) sampled surface soil had low levels of contamination, (2) the wastes were buried underground, and (3) the presence of surficial ground cover on the site limited the amount of dust emissions that could migrate off site. For these reasons, no public health hazards were likely associated with exposures from surface soil contaminants blowing off the site; however, these conditions represent conditions at the time of this health assessment, and might not represent conditions that occurred in the past. Because of the lack of sampling data for the past, ATSDR cannot evaluate and comment on past human exposure or the consequences of that exposure.

Child Health Initiative

ATSDR recognizes that infants and children might be more vulnerable to exposures than adults when faced with contamination of air, water, soil, or food [15]. This vulnerability is a result of the following factors.

  1. Children are more likely to play outdoors and bring food into contaminated areas.
  2. Children are shorter and their breathing zone is closer to the ground, resulting in a greater likelihood of breathing dust, soil, and heavy vapors.
  3. Children are smaller and receive higher doses of chemical exposure per body weight.
  4. Children's developing body systems are more vulnerable to toxic exposures, especially during critical growth stages in which permanent damage might be incurred.

The current concentrations of chemicals in the surface soil at the Rock Avenue Dumpsite are not at levels of health concern for children or for other residents of the area.



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