BLACKBURN AND UNION PRIVILEGES
WALPOLE, NORFOLK COUNTY, MASSACHUSETTS
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The tables in this section list the environmental contaminants of concern. This concern is based on comparison of contaminant levels detected on or near the site with those levels to which exposure has been associated with no adverse health effects. These comparison values include calculations from Reference Doses (RMEGs) and EPA's Drinking Water Life Time Health Advisories (LTHA), which are values derived from animal and human studies for which non-cancer adverse health effects were investigated. Cancer Risk Evaluation Guides (CREGs) are used for compounds which are known or suspected to be carcinogenic based on either animal or human studies. CREG levels are those for which exposure is associated with an excess cancer risk of one in a million. It is important to note that the presence of hazardous contamination levels is not indicative that actual exposure to site-related contaminants is occurring. The likelihood of hazardous exposure and the subsequent public health implications are addressed later in this preliminary public health assessment.
| PAHs | -Polynuclear Aromatic Hydrocarbons | |
| ND | -Contaminant not detected | |
| NA | -Comparison value for compound in specific environmental media is not available | |
| CREG | -Cancer Risk Evaluation Guide | |
| RMEG | -Media concentration calculated from EPAs reference dose (RfD) | |
| LTHA | -EPA's drinking water Lifetime Health Advisory | |
| MCL | -EPA's Maximum Contaminant Level | |
| MCLG | -EPA's Maximum Contaminant Level Goal | |
| ppm | -parts per million (milligrams per kilogram soil) | |
| ppb | -parts per billion (micrograms per liter of water) | |
| BLS | -Depth Below Land Surface |
The results of the site assessment investigation (Dames and Moore, 1989) are presented below.
Soil
Asbestos levels detected in soil in 1989 are presented as a percentage of the total weight of the sample. Of the 204 soil (0 to 6 inches BLS) samples taken, 81 (40%) had no asbestos fibers detected by Polarized Light Microscopy (PLM). Ninety-four (46%) of the 204 samples taken were less than 1% asbestos, 20 samples (10%) contained asbestos levels of 1% or greater and 9 samples (4%) had visible asbestos contamination. The asbestos content of these last samples was not quantified. The highest levels of soil asbestos (0 - 6 inches BLS) were detected along the Neponset River across from the west wing of the vacated facility building. Soil samples (0 - 6 inches BLS) with asbestos levels greater than 1% were most prevalent in the area along the Neponset River and that surrounding the west wing of the facility building. ATSDR comparison values (e.g., environmental media evaluation guide, or EMEG) for asbestos levels in soil have not yet been established.
Soil sampling for asbestos contamination was conducted in October and November of 1992 during excavation activities. This sampling was conducted at the sides and bottom of those areas excavated. The presence of asbestos at levels greater than 1% were indicative that further excavation and consequent sampling were necessary. All soils containing greater than one per cent asbestos were removed.
The remainder of contaminants detected in on-site soils during the site assessment conducted in 1989 are summarized in (Table 1). High levels of soil PAH contamination were detected along the south side of vacant factory's western wing, near the Neponset River. Significant PAH contamination was also detected in an accessible area near Clark Avenue. Elevated lead levels were detected in soils 18-48 inches BLS along the south bank of the Neponset.
Groundwater
Groundwater monitoring was conducted in March and April of 1989. The highest levels of groundwater contamination were detected in the area where deep soil contamination levels were also highest. Elevated contamination levels were also detected west of this area in the lateral direction of groundwater flow. Elevated metal levels were also detected in waters sampled from a well drilled near the northern wall of the vacant factory's west wing.
Asbestos was detected in water drawn from all but one monitoring well on the site. The results of on-site groundwater monitoring are presented in (Table 2). All contamination levels presented in this table were detected in waters sampled from monitoring wells drilled in the overburden. No bedrock groundwater monitoring has been conducted to date. Waters drawn from a monitoring well, which is situated on site at the residence immediately north of the vacant factory grounds, contained 134.1 Million asbestos Structures per Liter (MSL). Asbestos was also detected (596.0 MSL) in waters sampled from the monitoring well at the site's southwestern corner on the south bank of the Neponset River. Elevated levels of organic or metal contaminants were not detected in these wells.
Sediment
No asbestos was detected in sediment (0 - 6 inches BLS) sampled from the Neponset River upstream of South Street when monitored in March of 1989. One sample which was recovered at the South Street juncture contained 1% (by weight) asbestos. Of the 43 samples that were recovered from the Neponset downstream of South Street, 24 samples contained detectable amounts of asbestos. The highest asbestos levels, 5% by weight, were detected immediately downstream of South Street. The remainder of the sediments recovered from the Neponset where it flows through the site contained asbestos levels less than 1%. The Neponset River sediments were not analyzed for organic contaminants. Five sediment samples were recovered from the former mill tail race. One sample contained elevated levels of carcinogenic PAHs (30 ppm) and lead (779 ppm). Asbestos levels in these sediments ranged from 2% to 5%.
Surface Water
None of the surface water samples recovered from the Neponset River upstream of South Street during the sampling conducted in March of 1989 contained any detectable asbestos. One surface water sample was recovered from the Neponset immediately upstream of its confluence with the tail race. The asbestos levels in this sample were 47 MSL. No monitoring for organic or metal contamination was conducted on samples recovered from the Neponset River. Standing water from the former mill tail race was monitored for volatile organic compound (VOC) and heavy metal contamination. No significant levels of these contaminants were detected in any of the samples recovered from this area. It is not certain as to whether PAH contamination was monitored in surface water from this area. Asbestos (346 MSL) was also detected in a sample of standing water taken from the former mill tail race.
Air
On-site air monitoring was conducted while soil and groundwater samples were recovered during the 1989 site assessment. No quantifiable asbestos fibers were detected on filters removed from perimeter monitors. Asbestos levels for the 28 positive samples recovered from the personnel monitors ranged from 0 to 0.07 fibers per cubic centimeter. Upwind and downwind monitoring was also conducted during the site assessment. Two of these samples contained detectable fibers at levels of less than .02 fibers per cubic centimeter. It is important to note that this monitoring used phase contrast microscopy as an analytic technique which is not sensitive enough to detect short and thin asbestos particles. Asbestos also cannot be distinguished from other fibers using this technique (ATSDR, 1993). All fibers detected were assumed to be asbestos.
Soil
One hundred and sixty three soil samples (0 - 6 inches BLS) were recovered from areas external to the site grounds. Thirty five of these samples contained detectable asbestos levels. The samples with the highest asbestos levels were recovered from a residential lot at the end of Gleason Court immediately exterior to the southeastern corner of the site. Four of six samples recovered from the area contained asbestos levels of 1% or greater. Asbestos levels were also detected in soil samples (0 to 6 inches BLS) recovered from a lot near the Neponset at the point where it flows under Main Street, approximately 2,000 feet west of the South Street culvert. Seven of the 14 samples recovered from the area contained detectable asbestos. Four of these samples contained 1% asbestos. No monitoring for organic or metal contamination was conducted on soils recovered from grounds off the site.
Groundwater
All municipal wells in the Commonwealth are routinely monitored by MDEP for VOC and heavy metal contamination. Municipal wells situated one to two miles northwest of the site showed no organic or metal contamination since 1988. Trichloroethylene (TCE) was consistently detected in one of the municipal wells southeast (and presumably hydraulically upgradient) of the site during routine monitoring by MDEP conducted between March of 1988 and October of 1990. The TCE levels detected in unfiltered waters drawn from this well ranged from 1.7 ppb to 8.3 ppb. The MCL for TCE is 5 ppb. A Granulated Activated Charcoal (GAC) filtration system was installed at this well in July of 1990. Since that time, no TCE has been detected in filtered waters drawn from the well.
Surface Waters
Asbestos was detected in all five of the samples surface water drawn from the Neponset River at levels as high as 2,324 MSL. This maximum level was detected approximately 4,200 feet downstream of the South Street culvert. No monitoring for organic or metal contamination was conducted on surface water samples drawn from the Neponset river.
Sediments
Asbestos was also detected in off-site sediments sampled from the Neponset River. The majority of these positive asbestos samples were downstream of the confluence of the Neponset River with the mill tail race. Neponset River sediment samples containing 1% asbestos were detected as far down as 4,200 feet downstream of the South Street culvert. No monitoring for organic and metal contamination was conducted on off-site Neponset River sediment.
C. Quality Assurance and Quality Control
Data validation for monitoring conducted during the 1989 site assessment was independently performed for the environmental consultants who conducted the site assessment and for EPA. The firm validating results for Dames and Moore, the environmental consultants who conducted the site assessment, validated forty-five per cent of the data generated. This firm, Environmental Scientists Inc., concluded that the quality of the laboratory analyses was fair to good with some technical difficulties including poor surrogate and matrix spike recovery. The organic contamination data were believed to be appropriate for use as long as the documented qualifiers were considered. Some data for inorganic contamination were considered to be estimated values and were considered to indicate the presence of specific inorganic compounds. The analysis of these samples was, however, not sensitive enough to indicate that it was free of these inorganic contaminants. Overall, the data in the site assessment were considered acceptable for use (Dames and Moore, 1989).
The data validation conducted for EPA by Weston Inc. concluded that the organic contamination data validated did not reveal any major technical problems, however, matrix spike recoveries in some instances did not meet specifications. It was concluded that the organic contamination data were generally precise and accurate and could be accepted as valid. Validation of inorganic (metals) contamination analyses determined the data to be of fair quality with poor reproducibility for chromium, copper, lead, and silver (Weston, 1993).
EPA Region I developed a protocol for screening soil and sediment samples for asbestos content (U.S. EPA 1994); this protocol was required for analyses of site soils. Developing a protocol was necessitated because no standard method existed (and still does not exist today [Cooke 1995; Clifford 1995; Beard 1995]) for analyzing asbestos in soil or sediment. Reflecting the lack of any standard method for asbestos in soil, ATSDR (1993) provided no discussion of analytical methods for asbestos in soil. The protocol uses polarized light microscopy (PLM) to identify fibers found in the sample. EPA explicitly notes that the protocol is not meant to be used as a quantitative method; rather it is useful to determine whether or not soil or sediment contains significant amounts (e.g., greater than 1 percent) of asbestos. The protocol calls for sieving soil samples through a 250 µm sieve, and the material remaining on the sieve is analyzed. Hence the method initially detects fibers or bundles of fibers greater than 250 µm size. Identification of fibers as asbestos fibers is unequivocal with this analysis (U.S. EPA 1994; Cook 1995). The determination of the percent asbestos in the sample is based on a visual estimate made by the technician.
The reliability of the percent asbestos in soil estimates depends in part on the technician's experience. In addition, because the method only identifies fibers greater than 250 µm, the method may also under- or overestimate percent asbestos in the entire sample if the distribution of fibers in the smaller-sized fraction (i.e., less than 250 µm) is different than in the larger-sized fraction (i.e., greater than 250 µm). Thus, the estimated percent values are uncertain, but the degree or direction (e.g., overestimated) of uncertainty is not known.
Soil asbestos content determinations were conducted on soil samples taken at zero to six inches BLS. This analysis is inadequate for health assessment purposes since ATSDR considers soils between zero to three inches BLS to be those most prone to human contact and susceptible to becoming airborne when disturbed. The conclusions in this preliminary public health assessment are based on the data reviewed. The validity of the conclusions is dependent on the quality of the data reviewed.
D. Physical Hazards
Broken glass was observed on the window panes of the vacated factory. Lacerations resulting from contact with these surfaces may be possible. It is not known whether this building is currently kept locked. No other physical hazard was apparent during the site visit conducted in December of 1992.
In this section, various transport means of environmental hazards from the contamination source to human receptor populations and means of human exposure are presented. This pathways analysis consists of five elements: a source of contamination, transport through an environmental medium, a point of exposure, a route of human exposure (inhalation, ingestion, or dermal absorption) and an exposed population. Completed pathways require that the five elements exist and indicate that exposure to a contaminant has occurred in the past, is currently occurring, or will occur in the future. The presence of a complete environmental pathway does not, however, necessarily mean that adverse health effects will occur or have occurred in the past as a result of such exposure. Potential exposure pathways are those that do not contain all of the above elements necessary to complete a pathway but at some time in the past, present or future all of those elements may have been in existence. Exposure indicated by potential pathways is not certain to have occurred or currently be ongoing.
The extent of public health risk depends not only on the opportunity for exposure but also on the toxicity of the contaminants and the dosages to which the receptor population is exposed. These two factors are discussed in the Public Health Implications section.
A. Completed Exposure Pathways
Air-Past
According to the 1988 asbestos exposure survey, some residents of Walpole experienced exposure to airborne asbestos in the past. This conclusion is based on the scored subjective responses to survey questions. The heaviest environmental asbestos exposure was limited to those individuals either living in the same residence as those occupationally exposed to asbestos or those living within a half-mile radius of the site. Fifteen of the 187 respondents living in the same household or near the site were at moderate to high risk of asbestos exposure according to the results of the questionnaire administered. Living near the site, however, did not necessarily entail high exposure to asbestos. Of the same 187 respondents, 107 were at low risk of asbestos exposure according to the survey results.
Generation of airborne asbestos particles may have been possible as a result of disturbance of remnants containing asbestos that have been observed at the site for the past. Older children are reported to have played on the site and to have thrown clutch plates that were discarded at the site (MDPH, 1988). It is likely that inhalation of airborne asbestos particles occurred at this time. Work related activities at the site may also have resulted in the generation of airborne asbestos particles. Such migration, however, may have not been significant since perimeter air monitoring at the site failed to detect asbestos fibers during sampling activities conducted in 1989.
The potential for asbestos migration through air was probably reduced greatly when significant amounts of asbestos, including a mound of remnants situated at the site's southern border, were buried and capped on the site in 1992. Soil monitoring for asbestos was conducted during this removal action. All soils containing greater than 1 percent asbestos were excavated. Soils need to be monitored in uncapped areas at depths of 0 to 3 inches BLS since ATSDR considers soils at these depths to be those most prone to human contact or dispersion when disturbed. Asbestos levels detected in soil samples taken at 0 - 6 inches may not necessarily reflect those levels in the top half (0 - 3 inches BLS) of the sample. Monitoring surface soil (0 - 3 inches in depth) for asbestos after the removal action would enable health officials to determine the current potential for exposure to uncapped asbestos at the site.
B. Potential Exposure Pathways
Air - Past, Present and Future
Organic odors were detected during the site visit conducted in December of 1992. Fuel oil spills have been reported in the past (Dames and Moore 1989; CHI, 1987). Carcinogenic PAHs and benzene may have been released as a result of these spills. This constitutes a potential exposure pathway since there is only a possibility that these compounds are transported through air and the element of contaminant transport in the exposure pathway may be missing. The extent of exposure via inhalation cannot be determined since no ambient air monitoring for PAHs or VOCs has been conducted on the site to date. Benzene, which is readily volatile and relatively soluble in water, has been detected in on-site groundwater which is reported to discharge to the Neponset River (Dames and Moore, 1989). Ambient air near this point of discharge may potentially contain detectable benzene levels. The element of contaminant transport through air may or may not be present. As a result, this pathway can not be considered complete. The extent of exposure to surface water contaminants via inhalation cannot be estimated until surface water monitoring for VOCs has been conducted.
Soil - Past
Asbestos contaminated soil has been detected off-site as far as 2,000 feet west of the site. It is reported that a resident in this area used on-site soils for yard fill near the Neponset River (CHI, 1987). It is not certain how asbestos migrated to the lot on Gleason Court. The possibility of asbestos exposure to these contaminated soils was greatly reduced with their removal in 1992.
Exposure to elevated levels of lead and carcinogenic PAHs via dermal contact and ingestion may be possible since they have been detected in areas south of the Neponset River and near Clark Avenue that can be accessed by pedestrian traffic. These compounds were detected in soils 18 to 42 inches BLS. It is not known if a point of exposure exists in this potential pathway since the contaminant levels in surface soils (0 to 3 inches BLS), which are readily available for human contact, are not known. It is not certain if the contaminated soils near Clark Avenue detected in 1989 have been capped. Those soils south of the Neponset where elevated lead levels were detected were capped during the removal action and future contact with the contaminants in this capped area is not likely.
Soil - Future
Polynuclear aromatic hydrocarbons are generally not soluble in water and tend to adhere strongly to soil. They can therefore migrate when erosion occurs. River flooding will accelerate this process. The site at some points is 10 feet above the surface of the Neponset River. These compounds in the past may have migrated toward the river. In addition, regular monitoring of the integrity of the cap placed along the west wing of the factory will be necessary in order to ascertain that this type of migration does not occur in the future.
The cap placement conducted during the emergency removal action covered asbestos and other soil contaminants. Contaminants such as PAHs were not well characterized. As previously stated, PAHs were detected in shallow (18-48 inches BLS) and deep (6-23 feet BLS) soils which have since been capped. Although these contaminants are generally not mobile in soils, VOCs such as benzene, which was detected in groundwater in this area will migrate laterally through soils. Future monitoring efforts aimed at determining the extent of such migration and the possibility for exposure to these compounds may entail disturbance of the cap and asbestos contaminated soils. Exposure to asbestos via dermal contact and inhalation may occur as a result of such activities if proper protective and containment procedures are not strictly followed.
Sediment - Past, Present and Future
Asbestos has been detected intermittently in sediments recovered from the Neponset River. The highest levels were detected at the South Street culvert while little or no asbestos contamination was detected in sediments recovered from the Neponset River near the west wing of the vacated factory. Asbestos contaminated sediment was again detected where the mill tail race and the Neponset River converge. Asbestos-contaminated sediment from the Mill tail race was excavated during the 1992 asbestos removal action. Asbestos was also detected upstream of the area where on-site soils were reportedly used as yard fill.
Exposure to asbestos via inhalation in these areas is unlikely since wet asbestos fibers are less prone to airborne migration than are those contained in dry environmental media. Asbestos detected in river sediment may be more prone to become airborne if the river should run dry. It is uncertain, however, if this occurs in the area where the river flows through the site.
Dermal contact with these sediments is possible during wading activities. It is, however, not known whether this route of exposure exists in this exposure pathway since it is not known whether wading actually occurs in contaminated sections of the river. In addition, it is not possible to determine if dermal exposure to carcinogenic PAHs is occurring during potential wading activities in the river since sediments have not yet been monitored for PAH contamination.
Biota - Past, Present and Future
Polynuclear aromatic hydrocarbons tend to accumulate in fat tissue of wildlife and aquatic organisms. Exposure to these compounds may be possible by individuals who consume game or fish that have taken up PAHs. These compounds, which could plausibly contaminate river sediments, could migrate through aquatic organisms and accumulate in fish indigenous to river waters which could subsequently be consumed by humans. This pathway can not be considered complete since it is not known whether contamination is migrating to game or fish or whether fishing is actually occurring in the area.
Groundwater - Past, Present and Future
Groundwater flow has been observed in limited hydrogeologic investigations at the site to flow from east to west and to discharge to the Neponset River. The points of discharge have not yet been established. In addition, only the hydraulic properties and extent of groundwater flow have been characterized in that which flows through soils (the overburden). Bedrock groundwater monitoring has not yet been conducted at the site therefore the extent of downward contaminant migration cannot be assessed. Benzene, which was detected at high levels near the south wall of the factory's west wing, is relatively water soluble. Reduced benzene levels were detected in groundwater hydraulically downgradient of this area. The extent of contaminant discharge to the Neponset River cannot be determined in the absence of VOC monitoring of surface waters.
Benzene, which is lighter than water, would be prone towards lateral migration, whereas PAHs, which are generally insoluble in water, are also heavier than water and would migrate downward in their undissolved state. Asbestos, which does not dissolve in water, could only migrate in the suspended state in groundwater. This could only occur if the pore space between soil particles were large enough to allow fiber passage. Asbestos has, however, been detected in all groundwater sampled on and off the site. Private groundwater wells have been identified hydraulically downgradient of the site, however, it is not known whether these waters are contaminated with site-related contaminants. Further hydrogeologic investigations may be necessary in order to determine if private groundwater monitoring is warranted.
From March of 1988 through October of 1990, TCE had been detected consistently in one municipal well southeast and presumably upgradient to the site. Water samples drawn through the GAC filtration system, which was installed at this well in July of 1990, did not contain detectible TCE levels. The extent and duration of TCE exposure via ingestion of unfiltered waters from the contaminated well can not be determined since routine monitoring for contaminants such as TCE did not commence until 1988. It is reported (personal communication with MDEP official, 1993), however, that the well was active for approximately two years prior to the start of routine monitoring. It was also reported that waters drawn from this well were routinely combined with those drawn from two other wells in the immediate area that contained no TCE contamination. Since TCE has not yet been detected in significant levels in on-site groundwater, it is extremely unlikely that the site could have been a source for the contamination detected in the municipal well.
Surface Water - Past, Present and Future
Asbestos may be transported via surface water flow since it has been detected downstream of the site. Dermal exposure to these fibers may be possible during wading activities. This pathway cannot be considered complete since it is not known whether human exposure (dermal contact) with asbestos-contaminated waters is occurring. In addition, it is not known if exposure to benzene is occurring during wading activities since no VOC monitoring has been conducted in waters from the Neponset River.
In this section, the potential health risks posed to the public as a result of possible exposure to site contaminants are evaluated. In addition, available health data pertinent to the site are presented. The possible impact of environmental exposure on disease rates is discussed in this section. Finally, citizen concerns specifically voiced to public health officials are addressed. In the following section ATSDR Toxicological Profiles for asbestos, polycyclic aromatic hydrocarbons, arsenic, benzene, lead, and TCE were used.
Asbestos
Exposure to on-site asbestos probably occurred in the past. Children have been observed playing with asbestos remnants at the site (MDPH, 1988). In addition, the results of a questionnaire administered to Walpole residents indicate that some survey responders had incurred asbestos exposure. Numerous human studies have demonstrated an association between asbestos inhalation in an occupational setting and lung cancer development. The risk of lung cancer development among cigarette smokers who are exposed to asbestos via inhalation is especially enhanced.
It is not known if individuals trespassing on the site were exposed to hazardous asbestos levels via inhalation since these levels were not known when frequent trespassing was believed to have occurred. It is possible that residents in the surrounding area who stayed off the site did not incur significant asbestos exposure since fiber levels monitored at the boundaries of the site were not high enough to measure with any degree of certainty. The few positive levels detected on personal and upwind and downwind monitors did exceed .000004 fibers per cubic centimeter. This level has been estimated from human studies to incur a lifetime excess cancer risk of one in one million among individuals who also smoke cigarettes. Detected levels also exceeded .00006 fibers per cubic centimeter the level that is estimated to confer a lifetime excess cancer risk of one in one million among individuals who do not smoke cigarettes (ATSDR, 1993).
Mesothelioma is a rare cancer of the membranes that line internal organs and is highly associated with asbestos exposure. This disease has been observed largely in asbestos workers, however, individuals residing with asbestos workers are also at elevated risk of mesothelioma possibly due to exposure to asbestos that adheres to the workers's clothing. Human studies have not demonstrated an association between cigarette smoking and mesothelioma development.
Some studies have observed an association between asbestos inhalation and cancers of the esophagus and kidney. These findings have not been consistently replicated by other occupational studies. Ingestion of asbestos has also been suspected to be associated with the development of gastrointestinal cancers in humans. There have been inconsistent findings in both human and animal studies investigating this relationship.
Few studies have identified a relationship between environmental asbestos exposure and cancer development. The majority of the studies demonstrating an elevated risk of cancer development and asbestos exposure were conducted in an occupational setting where levels of asbestos exposure are much higher than those that would be expected in a community setting. It is not currently known to what levels of asbestos Walpole residents may have been exposed in the past. Clinical studies may have identified immunologic markers that may be indicative of such past exposure (Sprince, 1991).
High level asbestos exposure is associated with non-cancerous lung disease such as asbestosis. It is extremely unlikely that Walpole residents were exposed to those levels associated with this disease. Occupational studies have observed the development of corn-like benign skin lesions on those workers consistently exposed to asbestos via dermal contact. It is not certain whether or how frequently Walpole residents may have experienced such exposure.
Carcinogenic PAHs
Carcinogenic PAHs were detected in on-site soils at depths below 18 inches. Since no monitoring of soils above this depth have been conducted, the extent or likelihood of exposure to these compounds that was sustained by individuals frequenting the site can not be currently estimated.
Carcinogenic PAH's are compounds to which exposure is suspected by the scientific community to be associated with an increased risk of cancer development. These compounds include benzo(a)pyrene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, dibenzo(a,h)anthracene and indeno(1,2,3-cd) pyrene. These compounds have been characterized as to their carcinogenicity to varying degrees. Since an individual is rarely exposed to one type of PAH, no conclusive human evidence currently exists associating exposure to specific PAHs with increased risk of cancer development. Animal studies conducted under controlled conditions have provided the majority of the evidence for characterizing these compounds's carcinogenic properties. Benzo(a)pyrene is best understood with respect to cancer risk. As a result, until further evidence is presented to the contrary, the remaining carcinogenic PAH's are assumed to be as potent carcinogens as benzo(a)pyrene.
The majority of the animal studies conducted have demonstrated an increased risk of stomach cancer development upon ingestion of these compounds. Mice who were administered high PAH levels through the skin demonstrated an elevated risk of skin cancer development. It is not possible to determine the cancer risk associated with exposure to site-related PAHs in the absence of current information on soil and sediment PAH contamination on the site.
Arsenic
It is not known if arsenic exposure occurred to individuals at the site since soils above eighteen inches were not monitored. Arsenic was detected in on-site soils at depths below eighteen inches. Human studies have indicated that individuals exposed to arsenic via ingestion are at increased risk of skin lesion development. If untreated, skin tumors may result.
Benzene
If benzene-contaminated ground water detected on-site were available in the future, individuals ingesting these waters on a regular basis would be at risk of leukemia development. It is important to note, however, that there are currently no known plans for future use of these waters and that these waters are not currently being used.
Lead
It is not known if lead exposure occurred to individuals at the site since soils above eighteen inches were not monitored. Lead was detected in on-site soils at depths below eighteen inches. Children between the ages of zero to six years of age are especially sensitive to the neurotoxic effects of exposure to lead via ingestion. Ingestion of lead levels detected in accessible soil could precipitate such adverse health effects.
Trichloroethylene
There have been no non-cancerous health effects associated with ingestion of the TCE levels detected in the municipal well southeast of the site. A low risk of liver cancer has been identified in laboratory animals who experienced TCE exposure via ingestion over the course of a lifetime. It is not likely that Walpole residents incurred lifetime exposure to TCE via ingestion of municipal waters.
B. Health Outcome Data Evaluation
In 1988, the MCR conducted an investigation of kidney cancer in Walpole and concluded that the proportion of kidney cancer cases to the total number of cancer cases in the area near the site was higher than that expected based on the statewide experience. In 1992, the Community Assessment Unit within the Bureau of Environmental Health Assessment at the MDPH followed up this report with of an investigation of kidney cancer incidence in Walpole from 1982 through 1988. In this study, an elevation of the kidney cancer incidence rate was detected among females in the census tract where the site is located (4 cases observed/1.5 cases expected). See figure 5. The Standardized Incidence Ratio (SIR) is the number of cases observed in the area of concern divided by the number of cases expected in that area based on the statewide experience. The SIR is reported as a percentage and is thus multiplied by 100. The kidney cancer SIR for women residing in the census tract encompassing the site was 266.7 indicating that the number of cases in the census tract was more than twice than that expected based on the statewide experience. This elevation, however, did not achieve statistical significance at the .05 level meaning that there is greater than a five per cent chance that this increase could have occurred by chance alone.
For purposes of this preliminary public health assessment, this association was reevaluated using MCR data in Walpole from 1982 to 1989. The results of this evaluation are presented in Tables 3a and 3b. An elevation of the kidney cancer rate from 1982 to 1989 was detected among females in the census tract encompassing the site. The SIR during this period was 205.9 (5 cases observed/2.4 expected). This elevation did not achieve statistical significance at the .05 level. The rates of kidney cancer in men residing in the census tract encompassing the site were near or below those that would be expected based on the statewide experience.
Lung cancer rates between 1982 and 1989 were also evaluated among Walpole citizens. The lung cancer rate among females residing in the census tract encompassing the site was elevated (17 cases observed/12.3 expected). The SIR was 138. This elevation, however, did not achieve statistical significance. The rates of lung cancer in men residing in the census tract encompassing the site were near or below those that would be expected based on the statewide experience.
Mesothelioma is a rare cancer of internal organ linings which is highly associated with asbestos exposure. In addition to occupational exposure, an elevation has been observed in human studies among those individuals living with asbestos workers. The most recent MCR data were reviewed for incident mesothelioma cases in the area. None of the three mesothelioma cases diagnosed in Walpole (two females, one male) between 1982 and 1989 lived near the site. The extent of asbestos exposure incurred by these individuals is not currently known. The numbers of stomach and colo-rectal cancers in Walpole were at or below those expected based on age and sex specific rates for the Commonwealth.
C. Community Health Concerns Evaluation
1. Was the Walpole community extensively exposed to asbestos in the past?
Based on the results of a community wide survey, only 22 of 346 respondents (6.3%) were at moderate to high risk of asbestos exposure. Seven of these 22 individuals reported that they worked on the site, and the remaining 15 respondents reported that they either lived with asbestos workers or within a one-half mile radius of the site. Of the 187 respondents who lived within a half mile radius of the site or with an asbestos worker, 107 were at low risk of asbestos exposure. According to the survey administered in 1988, the majority of the Walpole citizenry who participated in the survey did not experience extensive asbestos exposure.
2. Are the cancer rates that are generally associated with asbestos exposure elevated in Walpole?
Lung cancer and mesothelioma are those cancers which have been consistently associated with
asbestos exposure. Lung cancer rates are elevated among females in Walpole, however, these
elevations are not statistically significant. None of the three mesothelioma cases diagnosed in
Walpole between 1982 and 1989 lived near the site. The rates of cancers that are potentially
attributable to asbestos exposure are discussed in further detail in the Health Outcome Data
Evaluation section. MDPH will continue to monitor rates of lung cancer and mesothelioma near
the site through the Massachusetts Cancer Registry.
