PRELIMINARY PUBLIC HEALTH ASSESSMENT
BLACKBURN AND UNION PRIVILEGES
WALPOLE, NORFOLK COUNTY, MASSACHUSETTS
The tables in this section list the environmental contaminants of concern. This concern is basedon comparison of contaminant levels detected on or near the site with those levels to whichexposure has been associated with no adverse health effects. These comparison values includecalculations from Reference Doses (RMEGs) and EPA's Drinking Water Life Time HealthAdvisories (LTHA), which are values derived from animal and human studies for whichnon-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 animalor human studies. CREG levels are those for which exposure is associated with an excess cancerrisk of one in a million. It is important to note that the presence of hazardous contaminationlevels is not indicative that actual exposure to site-related contaminants is occurring. Thelikelihood of hazardous exposure and the subsequent public health implications are addressedlater 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.
Asbestos levels detected in soil in 1989 are presented as a percentage of the total weight of thesample. Of the 204 soil (0 to 6 inches BLS) samples taken, 81 (40%) had no asbestos fibersdetected by Polarized Light Microscopy (PLM). Ninety-four (46%) of the 204 samples takenwere less than 1% asbestos, 20 samples (10%) contained asbestos levels of 1% or greater and 9samples (4%) had visible asbestos contamination. The asbestos content of these last samples wasnot quantified. The highest levels of soil asbestos (0 - 6 inches BLS) were detected along theNeponset River across from the west wing of the vacated facility building. Soil samples (0 - 6inches BLS) with asbestos levels greater than 1% were most prevalent in the area along theNeponset River and that surrounding the west wing of the facility building. ATSDR comparisonvalues (e.g., environmental media evaluation guide, or EMEG) for asbestos levels in soil havenot yet been established.
Soil sampling for asbestos contamination was conducted in October and November of 1992during excavation activities. This sampling was conducted at the sides and bottom of those areasexcavated. The presence of asbestos at levels greater than 1% were indicative that furtherexcavation and consequent sampling were necessary. All soils containing greater than one percent asbestos were removed.
The remainder of contaminants detected in on-site soils during the site assessment conducted in1989 are summarized in (Table 1). High levels of soil PAH contamination were detected along thesouth side of vacant factory's western wing, near the Neponset River. Significant PAHcontamination was also detected in an accessible area near Clark Avenue. Elevated lead levelswere detected in soils 18-48 inches BLS along the south bank of the Neponset.
Groundwater monitoring was conducted in March and April of 1989. The highest levels ofgroundwater contamination were detected in the area where deep soil contamination levels werealso highest. Elevated contamination levels were also detected west of this area in the lateraldirection of groundwater flow. Elevated metal levels were also detected in waters sampled froma 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 resultsof on-site groundwater monitoring are presented in (Table 2). All contamination levels presentedin 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 amonitoring well, which is situated on site at the residence immediately north of the vacant factorygrounds, contained 134.1 Million asbestos Structures per Liter (MSL). Asbestos was alsodetected (596.0 MSL) in waters sampled from the monitoring well at the site's southwesterncorner on the south bank of the Neponset River. Elevated levels of organic or metalcontaminants were not detected in these wells.
No asbestos was detected in sediment (0 - 6 inches BLS) sampled from the Neponset Riverupstream of South Street when monitored in March of 1989. One sample which was recoveredat the South Street juncture contained 1% (by weight) asbestos. Of the 43 samples that wererecovered from the Neponset downstream of South Street, 24 samples contained detectableamounts of asbestos. The highest asbestos levels, 5% by weight, were detected immediatelydownstream of South Street. The remainder of the sediments recovered from the Neponsetwhere it flows through the site contained asbestos levels less than 1%. The Neponset Riversediments were not analyzed for organic contaminants. Five sediment samples were recoveredfrom the former mill tail race. One sample contained elevated levels of carcinogenic PAHs (30ppm) and lead (779 ppm). Asbestos levels in these sediments ranged from 2% to 5%.
None of the surface water samples recovered from the Neponset River upstream of South Streetduring the sampling conducted in March of 1989 contained any detectable asbestos. One surfacewater sample was recovered from the Neponset immediately upstream of its confluence with thetail race. The asbestos levels in this sample were 47 MSL. No monitoring for organic or metalcontamination was conducted on samples recovered from the Neponset River. Standing waterfrom the former mill tail race was monitored for volatile organic compound (VOC) and heavymetal contamination. No significant levels of these contaminants were detected in any of thesamples recovered from this area. It is not certain as to whether PAH contamination wasmonitored in surface water from this area. Asbestos (346 MSL) was also detected in a sample ofstanding water taken from the former mill tail race.
On-site air monitoring was conducted while soil and groundwater samples were recovered duringthe 1989 site assessment. No quantifiable asbestos fibers were detected on filters removed fromperimeter monitors. Asbestos levels for the 28 positive samples recovered from the personnelmonitors ranged from 0 to 0.07 fibers per cubic centimeter. Upwind and downwind monitoringwas also conducted during the site assessment. Two of these samples contained detectable fibersat levels of less than .02 fibers per cubic centimeter. It is important to note that this monitoringused phase contrast microscopy as an analytic technique which is not sensitive enough to detectshort and thin asbestos particles. Asbestos also cannot be distinguished from other fibers usingthis technique (ATSDR, 1993). All fibers detected were assumed to be asbestos.
One hundred and sixty three soil samples (0 - 6 inches BLS) were recovered from areas externalto the site grounds. Thirty five of these samples contained detectable asbestos levels. Thesamples with the highest asbestos levels were recovered from a residential lot at the end ofGleason Court immediately exterior to the southeastern corner of the site. Four of six samplesrecovered from the area contained asbestos levels of 1% or greater. Asbestos levels were alsodetected in soil samples (0 to 6 inches BLS) recovered from a lot near the Neponset at the pointwhere 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 thesesamples contained 1% asbestos. No monitoring for organic or metal contamination wasconducted on soils recovered from grounds off the site.
All municipal wells in the Commonwealth are routinely monitored by MDEP for VOC and heavymetal contamination. Municipal wells situated one to two miles northwest of the site showed noorganic or metal contamination since 1988. Trichloroethylene (TCE) was consistently detectedin one of the municipal wells southeast (and presumably hydraulically upgradient) of the siteduring 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 8.3ppb. The MCL for TCE is 5 ppb. A Granulated Activated Charcoal (GAC) filtration system wasinstalled at this well in July of 1990. Since that time, no TCE has been detected in filtered watersdrawn from the well.
Asbestos was detected in all five of the samples surface water drawn from the Neponset River atlevels as high as 2,324 MSL. This maximum level was detected approximately 4,200 feetdownstream of the South Street culvert. No monitoring for organic or metal contamination wasconducted on surface water samples drawn from the Neponset river.
Asbestos was also detected in off-site sediments sampled from the Neponset River. The majorityof these positive asbestos samples were downstream of the confluence of the Neponset Riverwith the mill tail race. Neponset River sediment samples containing 1% asbestos were detectedas far down as 4,200 feet downstream of the South Street culvert. No monitoring for organic andmetal contamination was conducted on off-site Neponset River sediment.
Data validation for monitoring conducted during the 1989 site assessment was independentlyperformed for the environmental consultants who conducted the site assessment and for EPA. The firm validating results for Dames and Moore, the environmental consultants who conductedthe site assessment, validated forty-five per cent of the data generated. This firm, EnvironmentalScientists Inc., concluded that the quality of the laboratory analyses was fair to good with sometechnical difficulties including poor surrogate and matrix spike recovery. The organiccontamination data were believed to be appropriate for use as long as the documented qualifierswere considered. Some data for inorganic contamination were considered to be estimated valuesand were considered to indicate the presence of specific inorganic compounds. The analysis ofthese samples was, however, not sensitive enough to indicate that it was free of these inorganiccontaminants. 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 contaminationdata validated did not reveal any major technical problems, however, matrix spike recoveries insome instances did not meet specifications. It was concluded that the organic contamination datawere 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 poorreproducibility 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'sexperience. In addition, because the method only identifies fibers greater than 250 µm, themethod may also under- or overestimate percent asbestos in the entire sample if the distributionof fibers in the smaller-sized fraction (i.e., less than 250 µm) is different than in the larger-sizedfraction (i.e., greater than 250 µm). Thus, the estimated percent values are uncertain, but thedegree or direction (e.g., overestimated) of uncertainty is not known.
Soil asbestos content determinations were conducted on soil samples taken at zero to six inchesBLS. This analysis is inadequate for health assessment purposes since ATSDR considers soilsbetween zero to three inches BLS to be those most prone to human contact and susceptible tobecoming airborne when disturbed. The conclusions in this preliminary public health assessmentare based on the data reviewed. The validity of the conclusions is dependent on the quality of thedata reviewed.
Broken glass was observed on the window panes of the vacated factory. Lacerations resultingfrom contact with these surfaces may be possible. It is not known whether this building iscurrently kept locked. No other physical hazard was apparent during the site visit conducted inDecember of 1992.
In this section, various transport means of environmental hazards from the contamination sourceto human receptor populations and means of human exposure are presented. This pathwaysanalysis consists of five elements: a source of contamination, transport through an environmentalmedium, a point of exposure, a route of human exposure (inhalation, ingestion, or dermalabsorption) and an exposed population. Completed pathways require that the five elements existand indicate that exposure to a contaminant has occurred in the past, is currently occurring, orwill 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 ofsuch exposure. Potential exposure pathways are those that do not contain all of the aboveelements necessary to complete a pathway but at some time in the past, present or future all ofthose elements may have been in existence. Exposure indicated by potential pathways is notcertain to have occurred or currently be ongoing.
The extent of public health risk depends not only on the opportunity for exposure but also on thetoxicity of the contaminants and the dosages to which the receptor population is exposed. Thesetwo factors are discussed in the Public Health Implications section.
According to the 1988 asbestos exposure survey, some residents of Walpole experiencedexposure to airborne asbestos in the past. This conclusion is based on the scored subjectiveresponses to survey questions. The heaviest environmental asbestos exposure was limited tothose individuals either living in the same residence as those occupationally exposed to asbestosor those living within a half-mile radius of the site. Fifteen of the 187 respondents living in thesame household or near the site were at moderate to high risk of asbestos exposure according tothe results of the questionnaire administered. Living near the site, however, did not necessarilyentail high exposure to asbestos. Of the same 187 respondents, 107 were at low risk of asbestosexposure according to the survey results.
Generation of airborne asbestos particles may have been possible as a result of disturbance ofremnants containing asbestos that have been observed at the site for the past. Older children arereported 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 asbestosparticles. Such migration, however, may have not been significant since perimeter air monitoringat 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 significantamounts of asbestos, including a mound of remnants situated at the site's southern border, wereburied and capped on the site in 1992. Soil monitoring for asbestos was conducted during thisremoval action. All soils containing greater than 1 percent asbestos were excavated. Soils needto be monitored in uncapped areas at depths of 0 to 3 inches BLS since ATSDR considers soils atthese depths to be those most prone to human contact or dispersion when disturbed. Asbestoslevels detected in soil samples taken at 0 - 6 inches may not necessarily reflect those levels in thetop half (0 - 3 inches BLS) of the sample. Monitoring surface soil (0 - 3 inches in depth) forasbestos after the removal action would enable health officials to determine the current potentialfor exposure to uncapped asbestos at the site.
Organic odors were detected during the site visit conducted in December of 1992. Fuel oil spillshave been reported in the past (Dames and Moore 1989; CHI, 1987). Carcinogenic PAHs andbenzene may have been released as a result of these spills. This constitutes a potential exposurepathway since there is only a possibility that these compounds are transported through air and theelement of contaminant transport in the exposure pathway may be missing. The extent ofexposure via inhalation cannot be determined since no ambient air monitoring for PAHs orVOCs has been conducted on the site to date. Benzene, which is readily volatile and relativelysoluble in water, has been detected in on-site groundwater which is reported to discharge to theNeponset River (Dames and Moore, 1989). Ambient air near this point of discharge maypotentially contain detectable benzene levels. The element of contaminant transport through airmay or may not be present. As a result, this pathway can not be considered complete. The extentof exposure to surface water contaminants via inhalation cannot be estimated until surface watermonitoring for VOCs has been conducted.
Asbestos contaminated soil has been detected off-site as far as 2,000 feet west of the site. It isreported 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 maybe possible since they have been detected in areas south of the Neponset River and near ClarkAvenue that can be accessed by pedestrian traffic. These compounds were detected in soils 18 to42 inches BLS. It is not known if a point of exposure exists in this potential pathway since thecontaminant levels in surface soils (0 to 3 inches BLS), which are readily available for humancontact, are not known. It is not certain if the contaminated soils near Clark Avenue detected in1989 have been capped. Those soils south of the Neponset where elevated lead levels weredetected were capped during the removal action and future contact with the contaminants in thiscapped area is not likely.
Polynuclear aromatic hydrocarbons are generally not soluble in water and tend to adhere stronglyto soil. They can therefore migrate when erosion occurs. River flooding will accelerate thisprocess. The site at some points is 10 feet above the surface of the Neponset River. Thesecompounds in the past may have migrated toward the river. In addition, regular monitoring ofthe integrity of the cap placed along the west wing of the factory will be necessary in order toascertain that this type of migration does not occur in the future.
The cap placement conducted during the emergency removal action covered asbestos and othersoil contaminants. Contaminants such as PAHs were not well characterized. As previouslystated, PAHs were detected in shallow (18-48 inches BLS) and deep (6-23 feet BLS) soils whichhave since been capped. Although these contaminants are generally not mobile in soils, VOCssuch as benzene, which was detected in groundwater in this area will migrate laterally throughsoils. Future monitoring efforts aimed at determining the extent of such migration and thepossibility for exposure to these compounds may entail disturbance of the cap and asbestoscontaminated soils. Exposure to asbestos via dermal contact and inhalation may occur as a resultof such activities if proper protective and containment procedures are not strictly followed.
Asbestos has been detected intermittently in sediments recovered from the Neponset River. Thehighest levels were detected at the South Street culvert while little or no asbestos contaminationwas detected in sediments recovered from the Neponset River near the west wing of the vacatedfactory. Asbestos contaminated sediment was again detected where the mill tail race and theNeponset River converge. Asbestos-contaminated sediment from the Mill tail race wasexcavated during the 1992 asbestos removal action. Asbestos was also detected upstream of thearea 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 lessprone to airborne migration than are those contained in dry environmental media. Asbestosdetected in river sediment may be more prone to become airborne if the river should run dry. Itis 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, notknown whether this route of exposure exists in this exposure pathway since it is not knownwhether wading actually occurs in contaminated sections of the river. In addition, it is notpossible to determine if dermal exposure to carcinogenic PAHs is occurring during potentialwading activities in the river since sediments have not yet been monitored for PAHcontamination.
Polynuclear aromatic hydrocarbons tend to accumulate in fat tissue of wildlife and aquaticorganisms. Exposure to these compounds may be possible by individuals who consume game orfish that have taken up PAHs. These compounds, which could plausibly contaminate riversediments, could migrate through aquatic organisms and accumulate in fish indigenous to riverwaters which could subsequently be consumed by humans. This pathway can not be consideredcomplete since it is not known whether contamination is migrating to game or fish or whetherfishing is actually occurring in the area.
Groundwater flow has been observed in limited hydrogeologic investigations at the site to flowfrom east to west and to discharge to the Neponset River. The points of discharge have not yetbeen established. In addition, only the hydraulic properties and extent of groundwater flow havebeen characterized in that which flows through soils (the overburden). Bedrock groundwatermonitoring has not yet been conducted at the site therefore the extent of downward contaminantmigration cannot be assessed. Benzene, which was detected at high levels near the south wall ofthe factory's west wing, is relatively water soluble. Reduced benzene levels were detected ingroundwater hydraulically downgradient of this area. The extent of contaminant discharge to theNeponset 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 downwardin their undissolved state. Asbestos, which does not dissolve in water, could only migrate in thesuspended state in groundwater. This could only occur if the pore space between soil particleswere large enough to allow fiber passage. Asbestos has, however, been detected in allgroundwater sampled on and off the site. Private groundwater wells have been identifiedhydraulically downgradient of the site, however, it is not known whether these waters arecontaminated with site-related contaminants. Further hydrogeologic investigations may benecessary in order to determine if private groundwater monitoring is warranted.
From March of 1988 through October of 1990, TCE had been detected consistently in onemunicipal well southeast and presumably upgradient to the site. Water samples drawn throughthe GAC filtration system, which was installed at this well in July of 1990, did not containdetectible TCE levels. The extent and duration of TCE exposure via ingestion of unfilteredwaters from the contaminated well can not be determined since routine monitoring forcontaminants 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 priorto the start of routine monitoring. It was also reported that waters drawn from this well wereroutinely combined with those drawn from two other wells in the immediate area that containedno TCE contamination. Since TCE has not yet been detected in significant levels in on-sitegroundwater, it is extremely unlikely that the site could have been a source for the contaminationdetected in the municipal well.
Asbestos may be transported via surface water flow since it has been detected downstream of thesite. Dermal exposure to these fibers may be possible during wading activities. This pathwaycannot 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 tobenzene is occurring during wading activities since no VOC monitoring has been conducted inwaters from the Neponset River.
In this section, the potential health risks posed to the public as a result of possible exposure tosite contaminants are evaluated. In addition, available health data pertinent to the site arepresented. The possible impact of environmental exposure on disease rates is discussed in thissection. Finally, citizen concerns specifically voiced to public health officials are addressed. Inthe following section ATSDR Toxicological Profiles for asbestos, polycyclic aromatichydrocarbons, arsenic, benzene, lead, and TCE were used.
Exposure to on-site asbestos probably occurred in the past. Children have been observed playingwith 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 asbestosexposure. Numerous human studies have demonstrated an association between asbestosinhalation in an occupational setting and lung cancer development. The risk of lung cancerdevelopment among cigarette smokers who are exposed to asbestos via inhalation is especiallyenhanced.
It is not known if individuals trespassing on the site were exposed to hazardous asbestos levelsvia inhalation since these levels were not known when frequent trespassing was believed to haveoccurred. It is possible that residents in the surrounding area who stayed off the site did not incursignificant asbestos exposure since fiber levels monitored at the boundaries of the site were nothigh enough to measure with any degree of certainty. The few positive levels detected onpersonal 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 inone million among individuals who also smoke cigarettes. Detected levels also exceeded .00006fibers per cubic centimeter the level that is estimated to confer a lifetime excess cancer risk ofone 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 associatedwith 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 dueto exposure to asbestos that adheres to the workers's clothing. Human studies have notdemonstrated an association between cigarette smoking and mesothelioma development.
Some studies have observed an association between asbestos inhalation and cancers of theesophagus and kidney. These findings have not been consistently replicated by otheroccupational studies. Ingestion of asbestos has also been suspected to be associated with thedevelopment of gastrointestinal cancers in humans. There have been inconsistent findings inboth human and animal studies investigating this relationship.
Few studies have identified a relationship between environmental asbestos exposure and cancerdevelopment. The majority of the studies demonstrating an elevated risk of cancer developmentand asbestos exposure were conducted in an occupational setting where levels of asbestosexposure are much higher than those that would be expected in a community setting. It is notcurrently 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 pastexposure (Sprince, 1991).
High level asbestos exposure is associated with non-cancerous lung disease such as asbestosis. Itis extremely unlikely that Walpole residents were exposed to those levels associated with thisdisease. Occupational studies have observed the development of corn-like benign skin lesions onthose workers consistently exposed to asbestos via dermal contact. It is not certain whether orhow frequently Walpole residents may have experienced such exposure.
Carcinogenic PAHs were detected in on-site soils at depths below 18 inches. Since nomonitoring of soils above this depth have been conducted, the extent or likelihood of exposure tothese compounds that was sustained by individuals frequenting the site can not be currentlyestimated.
Carcinogenic PAH's are compounds to which exposure is suspected by the scientific communityto be associated with an increased risk of cancer development. These compounds includebenzo(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 characterizedas to their carcinogenicity to varying degrees. Since an individual is rarely exposed to one typeof PAH, no conclusive human evidence currently exists associating exposure to specific PAHswith increased risk of cancer development. Animal studies conducted under controlledconditions have provided the majority of the evidence for characterizing these compounds'scarcinogenic properties. Benzo(a)pyrene is best understood with respect to cancer risk. As aresult, until further evidence is presented to the contrary, the remaining carcinogenic PAH's areassumed to be as potent carcinogens as benzo(a)pyrene.
The majority of the animal studies conducted have demonstrated an increased risk of stomachcancer development upon ingestion of these compounds. Mice who were administered highPAH levels through the skin demonstrated an elevated risk of skin cancer development. It is notpossible to determine the cancer risk associated with exposure to site-related PAHs in theabsence of current information on soil and sediment PAH contamination on the site.
It is not known if arsenic exposure occurred to individuals at the site since soils above eighteeninches were not monitored. Arsenic was detected in on-site soils at depths below eighteeninches. Human studies have indicated that individuals exposed to arsenic via ingestion are atincreased risk of skin lesion development. If untreated, skin tumors may result.
If benzene-contaminated ground water detected on-site were available in the future, individualsingesting these waters on a regular basis would be at risk of leukemia development. It isimportant to note, however, that there are currently no known plans for future use of these watersand that these waters are not currently being used.
It is not known if lead exposure occurred to individuals at the site since soils above eighteeninches 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 neurotoxiceffects of exposure to lead via ingestion. Ingestion of lead levels detected in accessible soil couldprecipitate such adverse health effects.
There have been no non-cancerous health effects associated with ingestion of the TCE levelsdetected in the municipal well southeast of the site. A low risk of liver cancer has been identifiedin 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 ofmunicipal waters.
In 1988, the MCR conducted an investigation of kidney cancer in Walpole and concluded that theproportion of kidney cancer cases to the total number of cancer cases in the area near the site washigher than that expected based on the statewide experience. In 1992, the CommunityAssessment Unit within the Bureau of Environmental Health Assessment at the MDPH followedup this report with of an investigation of kidney cancer incidence in Walpole from 1982 through1988. In this study, an elevation of the kidney cancer incidence rate was detected among femalesin 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 concerndivided by the number of cases expected in that area based on the statewide experience. The SIRis reported as a percentage and is thus multiplied by 100. The kidney cancer SIR for womenresiding in the census tract encompassing the site was 266.7 indicating that the number of casesin 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 thatthere 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 usingMCR 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 casesobserved/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 orbelow those that would be expected based on the statewide experience.
Lung cancer rates between 1982 and 1989 were also evaluated among Walpole citizens. Thelung 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 achievestatistical significance. The rates of lung cancer in men residing in the census tract encompassingthe 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 asbestosexposure. In addition to occupational exposure, an elevation has been observed in human studiesamong those individuals living with asbestos workers. The most recent MCR data werereviewed for incident mesothelioma cases in the area. None of the three mesothelioma casesdiagnosed in Walpole (two females, one male) between 1982 and 1989 lived near the site. Theextent of asbestos exposure incurred by these individuals is not currently known. The numbersof stomach and colo-rectal cancers in Walpole were at or below those expected based on age andsex specific rates for the Commonwealth.
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 atmoderate to high risk of asbestos exposure. Seven of these 22 individuals reported that theyworked on the site, and the remaining 15 respondents reported that they either lived with asbestosworkers or within a one-half mile radius of the site. Of the 187 respondents who lived within ahalf 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 whoparticipated 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 withasbestos exposure. Lung cancer rates are elevated among females in Walpole, however, theseelevations are not statistically significant. None of the three mesothelioma cases diagnosed inWalpole between 1982 and 1989 lived near the site. The rates of cancers that are potentiallyattributable to asbestos exposure are discussed in further detail in the Health Outcome DataEvaluation section. MDPH will continue to monitor rates of lung cancer and mesothelioma nearthe site through the Massachusetts Cancer Registry.