The presence of hazardous contamination levels on the site is not necessarily indicative that actual exposure to site-related contaminants is ongoing. Levels of on-site contamination are presented in this section. In subsequent sections, possible means of exposure to site-related contaminants and resulting health risks to the community are evaluated.
Discrete areas are delineated in a schematic (Figure 4) for clarity in describing contamination patterns at the site. Contamination data summarized from the Feasibility Studies released in 1989 and 1990 are presented in Tables 1-6 and relate to those areas. The majority of the PCB contamination data presented in these studies did not differentiate between PCB congeners, therefore the data presented in these tables reflect the total PCB contamination detected.
Maximum surface sediment (0-12 inches) PCB levels on the site were detected in hot spot area "A" (102,099 ppm). The "hot-spot" areas contain cumulatively 45% by weight of the total PCB contamination detected within New Bedford Harbor. Two samples were recovered outside of the hot-spot areas which contained PCB contamination levels of greater than 4,000 ppm. One sample recovered on the shoreline between hot-spot areas "A" and "B" contained 5,762 ppm of PCBs. Another area of surface sediment between these two hot-spots, approximately 300 feet offshore contained 4,388 ppm of PCBs.
The majority of the harbor PCB contamination was detected in sediment sampled from the hot-spot areas and points southward. Some PCB contamination was, however, detected near the Wood Street Bridge, to the north, with PCB contamination levels reaching 1,587 ppm in surface sediment.
The Feasibility Studies for both the hot-spot areas and the remainder of the harbor contained contamination contour maps which were developed from pooled monitoring data (EBASCO, July, 1989). These data were generated from sampling conducted between 1982 and 1988. These maps indicate a general diminution in sediment PCB contamination levels with increasing distance south of the hot-spot areas. Pockets of elevated PCB contamination data were detected near sewer outfalls. Maximum PCB contamination levels in areas 4 through 8 were detected in proximity to these outfalls as was the highest subsurface sediment (12-24 inches) PCB contamination (1,440 ppm) detected in Area 2. In addition, maximum surface sediment PCB levels (101 ppm) in area 4 were detected immediately offshore from a railroad yard which historically received shipments of PCB oils.
Maximum copper levels (21,901 ppm) were detected in the harbor surface sediment immediately south of the Revere Copper Products plant near the Route 195 overpass. Metal contamination contour maps presented in both Feasibility Studies also indicate elevated levels of metal contamination in surface sediment near sewer outfalls draining into the harbor. Copper (2,731 ppm) and lead (1,592 ppm) were also detected on the Acushnet shore in the area surrounding the hot-spot region.
Surface sediments of the New Bedford shoreline, which are accessible to pedestrian traffic contained significant metal levels in surface sediment. Sediment sampled from the shoreline of hot-spot area "A" contained 1,680 ppm lead. Lead (1,420 ppm), copper (1,990 ppm) and cadmium (54 ppm) were detected in shoreline sediment sampled further south in area 2. Cadmium (70 ppm) was also detected in accessible sediment near the cove in area 3. Lead (434 ppm) was detected in the sediment (0-12 inches) near the playground in area 3. (EBASCO, 1989).
In 1983 it was reported that zinc, mercury and arsenic were also detected in sediments sampled from within the harbor (upper and lower) confines. Mean dry weight surface sediment levels for zinc, mercury and arsenic detected in the harbor were 770 ppm, .9 ppm and 12 ppm respectively. Median levels for these metals were zinc, 290 ppm, mercury, .3 ppm and arsenic 6.4 ppm (Metcalf and Eddy, 1983).
Estuary waters sampled at the hot-spots contained the highest levels (7.6 ppb [parts per billion]) of those monitored for PCB contamination levels. PCB contamination values presented reflect contamination that was either dissolved or suspended in harbor waters. These levels diminished sharply in those waters monitored south of the hot-spot region. Waters monitored in the cove one mile south of this region contained 1.0 ppb PCBs. Surface water monitored at the Coggeshall Street Bridge and the hurricane barrier contained PCB levels of .3 ppb and .1 ppb respectively. Bay waters, where only lobster harvesting is prohibited, contained PCB contamination levels of less than 0.1 ppb (NUS, 1984).
PCB contamination was monitored in aquatic wildlife harvested within the harbor confines as well as from landlocked regions of Buzzards Bay immediately south of the harbor. The results of these studies were presented in the 1983 data compilation. PCB (Aroclor 1254) contamination detected in eels harvested in harbor waters ranged from 11-730 ppm (mean level = 260 ppm; median level = 240 ppm). Eels harvested outside the harbor contained PCB contamination levels ranging from 12-38 ppm (mean level = 21 ppm; median level = 14 ppm) (Metcalf and Eddy, 1983). In 1987, Battelle Ocean Science (BOS) released more recent seafood contamination data. The results of this monitoring are presented in Table 7 and sampling locations pertaining to those areas are delineated in the fishing ban (figure 3) (EBASCO, August, 1989).
PCB levels in harbor biota were highest in that harvested from estuary waters whereas lead contamination was generally elevated in edible aquatic life, especially winter flounder (Pseudopleuronectes americanus) harvested from bay waters. Cadmium contamination levels in clams (Mercenaria mercenaria) were highest in those harvested from outside of restricted waters (EBASCO, August, 1989).
No lobsters (Homarus americanus) were monitored for contamination levels within harbor waters. In addition, reported PCB levels detected in lobster reflect only those concentrations found in edible muscle. The majority of PCB contamination is stored in the hepatopancreas (tomalley) which is sometimes consumed. PCB levels in the tomalley were not reported in the BOS biota PCB monitoring. The Division of Marine Fisheries (DMF) within the Massachusetts Department of Fisheries, Wildlife and Environmental Law Enforcement conducted annual monitoring of PCB contamination levels in lobster harvested from Area 3 of restricted waters between 1980 and 1986. The results of this monitoring include PCBs detected in both the muscle and the tomalley. The maximum values reported for each year ranged from 4.0 to 9.0 ppm which are considerably higher than those reported in the BOS monitoring. Copper levels, which are naturally high in clams and lobster were also not reported (EBASCO, 1989).
Air monitoring was conducted during the summer months in 1982 at the Aerovox Plant and PCB levels detected during this monitoring ranged from 1 to 100 nanograms per cubic meter (ng/M3) Aroclor 1242. These levels appear to have decreased from 1978 when PCB levels in air near the Aerovox Plant ranged from ND to 800 ng/M3 (Metcalf and Eddy, 1983). Ambient air monitoring conducted in 1985 detected total PCB levels of 471 ng/M3 in an area immediately east of the "hot-spot" area during low tide periods when the mud flats containing the "hot-spots" were exposed to direct sun. Background PCB levels of 7 ng/M3 were recorded at this time (EBASCO, 1990).
Unfiltered groundwater samples recovered from wells drilled at the Aerovox Plant site contained 200 ppb PCBs (non-specified) in the shallow overburden, while no ppb PCBs were detected in ground waters recovered from deeper levels (NUS, 1984).
Off-site air monitoring was conducted during the summer 1982 and monitors were placed northeast of the "hot-spot" area at the Acushnet Nursing Home as well as at a welding firm north of the site. In order to establish background PCB levels, monitors were also situated at Brooklawn Park, west of the "hot-spot" area and at the Burt School in Acushnet due east of the area. Mean total PCB levels of 69.4 ng/M3 and 88 ng/M3 were recorded in ambient air at the nursing home and welding company respectively. Background levels ranged from 3.7 to 16.0 ng/M3. In late 1988 and early 1989, extensive air monitoring was conducted where the pilot sediment dredging and disposal occurred at Sawyer's Cove approximately one mile south of the "hot-spot" area. This monitoring was conducted in order to determine the impact of such activities on air quality in the surrounding area. The results of this monitoring are presented in Table 8 (EBASCO, 1990).
To identify possible facilities that could contribute to the air, surface water and soil contamination near the hot-spot areas, the Toxic Release Inventory (TRI) database was searched for 1987 and 1988. It is possible, however, that this data base only represents a small percentage of the total potential emitters in the area. No releases of PCBs, lead, cadmium or copper were reported. A summary of air releases of VOCs and heavy metals is presented in Table 9.
Data presented in the PCB and heavy metal contamination contours were in some instances inconsistent with the raw data released in the 1989 feasibility study. When this disagreement was encountered, the raw data was considered for summary in this public health assessment.
Little groundwater contamination data was available for review during the preparation of this public health assessment. This presents a significant data gap since volatile organic compound (VOC) contamination is relatively soluble in water and enhances the environmental mobility of PCB contamination.
The conclusions in this public health assessment are based on the data reviewed. The validity of these conclusions is dependent on the quality of the data provided.
Access to the "hot-spot" region can be attained through the Aerovox grounds. The grounds are, however, fenced and secured by a patrolled gate. If access to the plant is attained, the risk of falling down the steep embankment that leads to the river shoreline is minimal given that there is a fence separating the factory grounds from the embankment. It has been reported by USEPA officials that security at the site could be improved.
In this section, various transport means of environmental hazards from the contamination source to human receptor populations are presented. If such migration and uptake by some members of the population is known to occur, the environmental pathway is considered to be complete. Complete exposure pathways are summarized in Table 10. The presence of a complete environmental pathway, however, does not necessarily mean that hazardous exposure has occurred or is ongoing. The extent of public health risk depends not only on the presence of 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.
Horizontal migration of PCB-contaminated sediments is occurring in the harbor as evidenced by the PCB contamination data presented in Table 1. The levels of PCB contamination detected in the surface sediment diminish with increasing distance from the "hot-spot" area. Transport of resuspended sediments with bound PCB contamination by tidal currents from this area is largely responsible for the observed southward contamination migration. Flow of the Acushnet River into harbor waters accounts for only 1% of water displacement during the tidal cycle. As a result, river flow does not factor heavily in sediment movement (NUS, 1984).
Deviations from the general trend of decreasing sediment PCB contamination with increasing distance from the hot-spot area may be attributable to the past industrial practices. It has been reported by the USEPA that Aerovox and CDE released PCB-contaminated waste water into the municipal sewer system which was subsequently discharged into harbor waters (EBASCO, 1990). Flow constrictions at various man-made and geographic barriers may also be attributable to the irregular pattern of PCB contamination distribution observed in lower harbor sediments.
Other irregularities in PCB distribution are evident in the area surrounding the hot-spot regions. PCB contamination detected in sediment at the Wood Street Bridge north of the hot-spot area is attributed to tidal influences. The areas of elevated PCB contaminated sediments detected in the wetlands on the eastern shore of the estuary are near tidal creeks and drainage ditches.
PCB contamination in subsurface sediment is limited to those areas near sewer outfalls. Given the tendency of these compounds to strongly adhere to sediment, natural downward migration over time, in the absence of other organic compounds, is unlikely. Measurements of currents and tidal fluctuations in the harbor indicate that the estuary accumulates relatively clean sediment from the outer harbor and bay areas. This, however, is not occurring to any significant extent.
Transfer of PCBs from contaminated sediment to the overlying surface water is also occurring since these compounds are slightly water soluble with solubilities in the absence of VOC contamination ranging from 2.7 to 590 ppb (ATSDR, 1991). The solubility of PCBs in surface water decreases as its salt content increases. The degree of PCB solubility also decreases with increasing amounts of chloride in the compound. The water solubility of these compounds increases in the presence of other organic compounds. The solution of PCBs into surface water subsequently facilitates their volatilization into ambient air (EBASCO, 1990).
Due to their chemical stability, PCBs tend to persist in the environment and few conditions are conducive to their degradation. PCBs can absorb light and as a result, hydroxy groups are substituted for chlorine atoms on the carbon rings. Under anaerobic conditions, this photolytic process can result in the production of toxic polychlorinated dibenzofurans (PCDFs)(Metcalf & Eddy, 1983). It is not expected, however, that this process is ongoing at a rate that would have a significant impact on contamination levels in the harbor (EBASCO, 1990).
Quantitative models estimating future PCB contamination migration have been based on measurements of wind velocity and water movement in the harbor area. Physicochemical parameters such as solubility coefficients and sediment resuspension rates were also considered in the development of these models. These models indicate that tidal movement of resuspended contaminated sediment and subsequent PCB volatilization primarily account for the removal of PCBs from the harbor area. Sediment transport modelling has, however, indicated that the capping of PCB-contaminated sediment in the estuary by the northward migration of clean sediment is not occurring to any significant extent.
Based on model projections, it is anticipated that with the removal of the PCB contamination in the hot-spot areas, tidal transport and volatilization will remove a finite amount of the remaining PCBs in the harbor and upper bay. Given the uncertainty inherent in such modelling, however, it cannot be accurately assessed as to what extent natural attenuation will occur.
Dermal contact with PCB-contaminated sediments is ongoing within the harbor confines. This is evidenced by swimming and wading activities observed by local health officials and fish wardens. Accidental ingestion of contaminated surface waters may also occur while swimming.
Monitoring of harbor biota have also indicated that PCBs are undergoing migration through the food chain. Significant levels of PCBs have been detected in bottom feeding fish, lobster and shellfish harvested inside and outside of harbor confines. Due to their lipophilic properties and chemical stability, these compounds tend to accumulate in fatty deposits within an organism. The extent of this bioaccumulation is dependent on the degree of the organism's exposure to contaminated media, rate of excretion of these compounds and fat content. Uptake of PCBs by aquatic animals can occur either by ingestion of contaminated sediment or other organic matter such as plankton. Also, ingestion of PCB contaminated water can occur via absorption through the digestive tract, respiratory organs or other permeable body surfaces.
Of the aquatic species monitored in the harbor area for PCB contamination, eels were observed to have the highest amounts of PCBs per wet weight tissue (Metcalf and Eddy, 1983). This is attributable to their habitat in sediment as well as their permeable outer surface which has a high lipid content. As evidenced by the data released in 1983 and 1987, the extent of PCB bioaccumulation in seafood decreases with increasing distance between the harbor waters and the area from where it was harvested. Once PCBs are ingested by the organism, biodegradation does not readily occur and accumulation in fatty tissue is prevalent. This metabolic pathway is especially preferred with those compounds that have higher amounts of chlorine per molecule.
Based on pooled monitoring data for PCB contamination of lobsters harvested in area 3 of the closure area, these levels have remained relatively constant from 1977 through 1987. These levels, however, have been in excess of those allowed by the United States Food and Drug Administration (USFDA), who have established a food tolerance of 2.0 ppm in edible tissue including the tomalley (EBASCO, Aug. 1989). Model projections indicate that with the removal of the PCB contamination from the "hot-spot" area, PCB levels may decrease in lobster over a ten-year course. These projections indicate, however, that in the absence of additional contaminated sediment removal from the upper estuary, PCB levels will remain relatively constant in the water column for an extended time period. As a result, PCB levels in the flounder harvested from the estuary area are expected to remain at or above the USFDA tolerance level (EBASCO, 1990).
Lead and cadmium have also been detected in edible aquatic life. The mean levels of these metals in seafood remain either constant or increase with increasing distance from the hot-spot area. These results may be attributable to statistical anomalies (Battelle, 1990). These metals are detected in pore water among sediments or in the water column proper.
The uptake of heavy metals is generally dependent on the dissolved metal levels. Lead in its elemental form is insoluble, however the acetate, chloride and nitrate of lead are appreciably water soluble. Organolead compound formation in marine environments is possible through numerous chemical and biological transformations. These compounds have a finite but low water solubility. Cadmium exists in marine environments in the hydrated form which is relatively mobile. The chemical composition of the sediment, however, can affect the mobility and subsequently impact the cadmium availability to the aquatic organism (DiToro, 1990).
Lead, which can be directly ingested by fish, shellfish and lobster, is usually stored in their digestive organs. Lead, however, is not significantly magnified through the food chain. Marine organisms bioaccumulate cadmium and as a result cadmium levels can be detected at elevated levels most notably in shellfish.
Although enforcement of the fishing ban promulgated by MDPH in 1979 has been assured by patrolling of harbor waters by local officials, consumption of PCB-contaminated seafood is still ongoing. Recreational fishing within restricted waters has been reported by local officials. In addition, 15.4% of the participants in the GNBHES have reported eating fish or lobster that has been locally caught (i.e., in the closure area) by themselves, friends or relatives. Conversely, 61.5% of the participants in this study reported eating no seafood that was locally caught (MDPH, 1987). Specific subpopulations of the Greater New Bedford area are suspected to be at higher risk of exposure to PCB contamination via the ingestion of tainted seafood. During the GNBHES, a subsample was drawn from those Greater New Bedford residents that were issued a recreational fishing license. A higher percentage of these individuals reported consuming seafood caught from the contaminated areas compared to those participants in this study who were randomly selected. Since PCB contamination is not evenly distributed throughout the body tissue in some species, those portions of the population who eat the organs that store these contaminants are also at higher risk of PCB exposure via ingestion of contaminated seafood. For example, those people who consume the tomalley of the lobster are more prone to such exposure. The GNBHES reported that 46% of the participants who reported consumption of lobster caught from contaminated waters also reported regular consumption of the tomalley.
Exposure to metal contamination via ingestion of contaminated seafood harvested from bay waters is also likely. Cadmium and lead were detected in clams and lobsters harvested from these waters. Lead was also detected in flounder harvested from outside of restricted waters. These metals usually accumulate in the digestive organs. Since clam consumption includes the ingestion of these organs, those individuals who consume clams are exposed to cadmium and lead levels contained in the organism. Metals accumulate in the lobster tomalley, therefore the degree of metal exposure associated with lobster consumption is dependent on whether or not the tomalley is eaten. Lead in flounder also accumulates in the digestive organs which are generally not eaten. The extent of lead exposure via consumption of flounder is therefore expected to be low. Fish and shellfish harvested from these open waters are caught for commercial purposes and are widely distributed. As a result, exposure to metal contamination in this seafood is not only limited to residents of the Greater New Bedford area.
Remedial alternatives are currently under consideration to further reduce the sediment PCB levels in the remainder of the harbor which will result in lower seafood contamination levels. The sediment contamination levels after remediation will effect the time necessary to achieve allowable contamination limits in seafood.
PCBs generally do not readily evaporate into air, however, finite amounts of PCBs have been detected in ambient air during the monitoring rounds that have been conducted in and around the harbor area. The levels appear to diminish with increasing distance from the "hot-spot" area. In addition, the monitoring conducted in 1985 demonstrated that PCB migration into air from this region was greater at low tide when the "hot-spots" were exposed to the sun. Direct exposure to higher temperatures during low tides especially during the summer months would account for the increased volatility of these compounds and their subsequent migration through air.
The monitoring conducted between 1988 and 1989 demonstrated that ambient air PCB levels were higher during the warmer months and on days when wind speeds were low. High wind velocities will quickly dilute airborne contaminants and as a result, low concentration levels will be registered during these times. Low velocity winds will carry airborne contaminants in the direction that the wind is blowing (EBASCO, 1990). While these directions will can change instantaneously, seasonal trends in wind direction have been determined over time. During fair weather in the fall and winter months, winds tend to blow from the northwest. Storm winds during the winter months come from the northeast. Summer winds blow from the southwest when the weather is fair and from the southeast during stormy weather (personal communication with FAA official).
B. Potential Exposure Pathways (See Table 11)
In April of 1990, a remedial plan was selected that entails dredging the "hot-spot" areas. The plan also includes the construction of a pipeline for the specific purpose of transporting 10,000 cubic yards (yds3) of contaminated sediments to a storage and incineration site in the cove one mile south of the hot-spot areas. It is estimated that dredging of sediments with PCB contamination levels greater than 4,000 ppm under negative pressure will remove 45% (by weight) of the PCB contamination that has been detected at the site (EBASCO, 1989). This will reduce, somewhat, the potential for lateral sediment migration and solubilization into harbor waters.
It is possible that dredging the area in itself would disturb contaminated sediment so as to enhance its movement. To determine if this would actually occur, a pilot dredging study was conducted in Sawyer's Cove approximately one mile south of the "hot-spot" area. Using a cutterhead dredge, 7500 yds3 of sediment containing on average 100 ppm PCB contamination was dredged and stored in a confined disposal facility (CDF) immediately south of the cove. Prior to and during the dredging process, harbor waters adjacent to the operating dredge were monitored for PCB contamination. PCB levels in waters monitored at the Coggeshall Street Bridge were 0.60 ppb prior to the pilot dredging operations and 0.57 after the dredging process. The pilot study succeeded in demonstrating that using the proposed dredging materials and preparations for operation, no appreciable changes in surface water PCB contamination levels will occur (EBASCO, 1990).
The amount of sediment resuspension was also measured during the pilot study. Applying the results of this monitoring to conditions that would be experienced in the "hot-spot" area, it was estimated that 29 percent of the resuspended material (0.3% of total sediment dredged) would migrate beyond a 100 yd radius of the dredging site. Sediment monitoring will also occur during the full scale dredging to determine the extent of PCB migration during the process.
It is possible that during the dredging process raw industrial oils may be uncovered. These oils may contain volatile organic contamination which would solubilize existing PCB contamination and enhance their environmental mobility. Since the dredging is being conducted under negative pressure, however, it is unlikely that the disturbance of such oils would result in a significant environmental release.
The dredged slurry containing 2.5% sediment would be hydraulically pumped via a pipeline to a dewatering tank where the sediment will settle out. The floating pipeline will be continually monitored for contaminant leakage. Effluent water from the holding tank will be treated with flocculating agents that will precipitate sediments and metals. Precipitated matter will be removed from the waste stream via filtration. The water will then be passed through an oxidation/photolysis unit to assure the destruction of detectible levels of PCBs (EBASCO, 1989).
The sediment that settles in the holding tank along with the associated waters will then be pressed. Water generated from the pressing process will be recycled back to the holding (settling) tank for subsequent chemical treatment, filtration and dissolved PCB destruction. The pressed sediment will be fed into the incinerator to be burned via a two-step process. The first step will involve the heating of the sediment to 1,000oF to 1,600oF for thirty to forty-five minutes in the primary combustion chamber (PCC). During this time, PCBs bound to sediment will volatilize. These compounds, then in the gaseous state, will flow to a secondary combustion chamber (SCC) where temperatures will reach 2,200oF. Destruction of PCBs and other organic compounds once bound to sediment will occur at this point. The resultant gases, ideally carbon dioxide, water and hydrochloric acid, are then cooled (or quenched) to approximately 400oF, neutralized, filtered and released through the incinerator stack (Weston, 1992). The ashes settling in the PCC (bottom ash) and those entrapped in the Air Pollution Control Device (APCD) will be tested to determine the extent to which metals that remained bound to them leach upon introduction of water. If metal leaching is determined to be excessive, the ashes are planned to be bound to concrete before being deposited in an on-site landfill, where the dewatering tank is situated. This on-shore landfill is termed a combined disposal facility (CDF). It is planned that the CDF will be capped with a cover impermeable to water. The bottom and sides of the CDF will be lined as well, in order to prevent the migration of leached contaminants (EBASCO, 1989).
The specific instrumentation to be used to carry out this phase of the remedial plan has been completely selected. It has been established that a cutter head dredge will be used since pilot dredging has indicated that the use of this specific dredge under negative pressure will achieve the least dispersion of contaminated sediments during the process. Rotary kiln incineration has been selected for the destruction of PCBs. This mode of incineration employs a rotating PCC which enables the sediments to be mixed and achieve necessary heat and oxygen accessibility. It has been demonstrated in other trial burns that rotary kiln incineration conducted under proper operating conditions is able to destroy 99.9999% of the PCBs in the waste feed (Sedman, 1991). If for some reason, however, the incinerator operates under inadequate conditions, PCBs will not be completely destroyed and hazardous compounds including polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs) could be formed (EBASCO, 1989). The selected incinerator will have systems designed into it such that these systems will automatically shut the incinerator down if inadequate operating conditions should arise.
A baghouse was selected as the APCD to be used with the selected incinerator. This devise captures particulates from the air stream while allowing gases to pass. Proper selection and testing of these devices is crucial since the chief health concerns associated with incineration of hazardous wastes involve the potential exposure to airborne incinerator emissions. Combustion of sediment contaminated with PCBs and heavy metals will have three waste streams. Bottom ash is the heavy ash that settles in the primary combustion chamber. These ashes which will contain heavy metals which can be successfully sequestered. Gases, water vapors and light ash (or fly ash) will flow through the secondary chamber where PCB destruction will take place. The resultant gases are cooled, neutralized and then filtered. These processes involve the passing of the gases through circulating water and alkaline solutions. These liquids will remove some metals and fly ash as well as neutralize the hydrogen chloride gases. As a result, these liquids become part of the waste stream and are recycled to the holding tank where they are processed with dredged water and the water generated from the pressing of settled sediment.
After neutralization, the remaining waste stream flows into the APCD. Fly ash and metals that are not captured here are released into ambient air through the incinerator emissions stack. It is the escape of metals, specifically lead, through this waste stream that poses the greatest health concern. Lead and cadmium contamination are prevalent in the hot-spot sediments to be dredged (EBASCO, 1989). The monitoring for these metals was scant but by using the results obtained from such monitoring it is possible to estimate the amounts of these raw metals that are expected to be processed during dredging and incineration. The amount of sediment-bound lead that is expected to be processed ranges from 5.7 to 8.8 tons and that for cadmium ranges from 254 to 508 pounds. (See Table 12 for derivation of these estimates.) Compared to other heavy metals, both lead and cadmium are more likely to be released during the incineration process given their low melting and boiling points. The melting and boiling points for elemental lead are 615.2oF and 3164.0oF respectively. The melting and boiling points for cadmium are 609.8oF and 1392.8oF respectively (Merck, 1976). The temperature of the PCC will exceed the point at which all cadmium volatilizes. In addition, a significant amount of lead in the PCC will vaporize although the boiling point of lead will not be reached. It is thought that during this process, lead is volatilized and as it cools in the quenching system, it condenses on fly ash also generated in the incineration process (Lee, 1988, Denison, 1990).
Studies have been conducted in order to characterize the partitioning of lead in the incinerator waste stream while varying the incineration temperature and the amount of chlorine in the waste feed (Carroll, 1989). These tests demonstrated that at the projected incinerator temperatures, 1600 - 1800oF in the PCC and 2400oF in the SCC, 14% of the lead on average in the waste feed remained with the bottom ash, 36% partitioned into the cooling and neutralizing (scrubber) water and approximately 50% was detected in the exhaust gas to be processed by other pollution control devices. These partitioning proportions were determined while keeping the chlorine content of the waste feed constant at 4%. The percentage of lead passing through the neutralizing system uncaptured increases with the amount of chlorine in the waste feed. At high chlorine levels (8% in the waste feed) approximately 75% of the lead in the feed escapes capture by the scrubber system. Considering the average PCB levels in the sediments to be processed, it is anticipated that the waste feed will contain approximately 1% chlorine. From the results of the lead partitioning studies, it can be estimated that the gas and particulates escaping scrubber capture will contain approximately 20% of the lead in the initial waste feed to be filtered through secondary air pollution control devices. The studies investigating lead partitioning in the waste stream demonstrated that 96% of the lead escaping scrubber capture is bound to fly ash and the remaining 4% escapes as fumes.
The base-line lead removal efficiency (i.e. under optimal conditions and containing no chlorine) of 50% exiting the scrubber is not consistent with other values reported (Lee, 1988, Denison, 1990). Monitoring of stack emissions from several hazardous waste incineration sites with various air pollution control devices has demonstrated lead removal efficiencies ranging from 77 to 99.9%. Past trial burn results of the actual incinerator planned to be used at the site have demonstrated lead removal efficiencies as high as 99.96% (Weston, 1992).
The temperature of the gases entering the air pollution control device is an essential determinant of emissions control efficiency (Denison, 1990). Formation of toxic dioxins and furans can occur on fly ash at temperatures ranging from 392 - 752oF in the APCD. Also, as the temperature of the material entering the APCD increases, the tendency for metal condensation on fly ash decreases and emission of metal fumes into ambient air is likely. Conversely, adequate cooling of gases (275oF) increases the likelihood that metals will condense on fly ash and subsequently be captured by the APCD (Denison, 1990). Elevated flue temperatures also increase the tendency for smaller fly ash particles to form which are more difficult to capture in the APCD. As a result, if temperatures are not cooled sufficiently prior to entering the APCD, metal condensation that does occur will do so on smaller particles which can be emitted to ambient air and are more susceptible to be entrapped in the lung.
Summarizing the potential for metal release from the incinerator waste stream, containment of the bottom ash should be achieved if proper dust control measures are implemented and stabilization of metals bound to these ashes can be assured. Some reports have stated that concrete stabilization may be ineffective (Superfund Reports, 1990). This shortfall may be overcome by the placement of a water impermeable cap and bottom liner which would prevent leachate formation and migration respectively. Waterborne lead generated by the operation of incinerator scrubbers will be transferred to the holding tank and undergo filtration during the clarification process. Adequate containment of pumped waters, careful handling of the filtered metals, and monitoring of the processed waters prior to discharge back into the harbor will assure that lead migration is not occurring via discharge of waste waters.
Some lead bound to fly ash, in all likelihood will be released through the incinerator stack. The uncertainty that currently exists is how much, and to where will it migrate. The former concern is primarily controlled by the removal efficiency of the baghouse to be used on the incinerator. The migration pattern of the contamination and consequent human exposure to stack emissions is determined by incinerator design and operating conditions. Such factors include emissions stack height and width as well as the temperature and speed at which the gas exits from the incinerator (Travis, 1989).
USEPA will also conduct a trial burn of the incinerator to ascertain that all criteria which have been developed for the protection of human health are met. Review of the trial burn data is essential for the accurate evaluation of exposure to incineration emissions to ambient air. Among the parameters that will be monitored are PCB destruction and removal efficiency (99.9999% of the PCBs in the gases exiting the PCC must be destroyed), dioxin and furan emissions, particulate (TSP) emissions and heavy metal emissions. Emissions standards for TSPs are set at .08 grains per cubic foot (ft3) of dry air released standardized to 7% oxygen. The qualifying standard of dry air at 7% oxygen is added to prevent diluting of TSP by the addition of air to the waste stream.
Allowable ambient air levels (AALS) for lead have been set at an annual average of .07 micrograms(ug) per cubic meter(M3) of air. The maximum allowable ambient air level for lead at any one time is .14 ug/M3. These standards will be enforced at the estimated point of maximum emission exposure. Emission dispersion models will be developed by USEPA upon completion of the incinerator design in order to determine where this point is. The development of dispersion models are expected to enable environmental officials to determine those lead levels emanating from the incinerator stack that would result in ambient air lead levels that are in compliance with state standards at the estimated point of emissions exposure.
Meteorologic conditions heavily influence the plume migration patterns through air. These conditions include, but are not limited to, wind speed and direction, ambient temperature and precipitation amounts (Travis, 1989). The distance that the emissions plume travels is dependent on wind speed as well as on precipitation. The plume will travel farther on windy days as opposed to those when it is calm. In addition, emissions will travel a significantly shorter distance on those days when precipitation is prevalent.
These meteorologic conditions are subject to variation over a short period of time. Such change is evidenced by the wind measurements which were determined near the proposed incineration site in late 1988 and the spring of 1989 (EBASCO, 1990). Although the wind blew predominately from the west and northwest during the late fall and early winter months, daily wind bearings form the north, northeast, south and southwest were also recorded. Winds from the north, east, southeast, south and southwest were recorded in the spring months. Winds blowing from the northwest and west were, however, predominant during this season as well as in the late fall and winter. The model needs to consider the transient nature of these conditions in order to adequately estimate emissions exposure.
The land surface in the area near the incinerator must also be considered during the model development. The behavior of the emissions plume is dependent upon the topography of the land over which it passes (Travis, 1989). If the plume travels over land which is relatively flat, there is little perturbation of the air stream and the emissions will generally travel with the prevailing winds. The presence of hills and valleys, however, will create undercurrents which will modify the flow of the emissions plume. The plume may also migrate in a different manner when traveling over water then it would when travelling over land.
The chemical and physical properties of the plume are also subject to variation. The degree of heavy metal condensation on fly ash, which occurs during the incineration process could affect the aerodynamic properties of emitted particles. If the metal content associated with fly ash is not known or is inaccurately assessed, the modeling results could also be compromised. The lead content of the fly ash will be determined during the stack tests and should be considered when developing models of emissions plume behavior. It may be possible to ascertain the accuracy of model estimations by conducting actual lead monitoring during the incineration process subsequent to the model development. Such monitoring would allow for the assessment of model estimations. If the model is deficient, lead monitoring will lend to a more accurate assessment of the actual exposure that the surrounding populous is experiencing.
Human exposure to lead emitting from the incinerator may occur via inhalation or ingestion. In addition, lead entrapped fly ash may settle in regional waters contaminating the food chain. The extent of these three routes of exposure is greatly dependant on the amount of lead-contaminated particles emanating from the incinerator. The impact of lead emissions on aquatic organisms will be minimal if lead removal is done at peak efficiency.
The populations in the vicinity of the proposed incinerator site are currently at increased potential for lead exposure. According to 1970 census data, 86% of the housing in New Bedford was constructed prior to 1950, which have increased possibility of containing lead-based paint. This poses a concern for children consuming lead paint which may flake in these housing units (MDPH, 1989, 1991).
According to the 1990 census, the housing in New Bedford encompassed by the census tracts in proximity to the incineration site (approximately 1.5 square miles) consists predominately of multifamily dwellings. Eighty-six percent of the residential buildings in this area house between two and nine families. The percentage of this type of dwelling for the entire city of New Bedford is 58.2%. Also according to the 1990 census, this area also has a predominance of children under 5 years of age, who frequently exhibit hand to mouth activity. The percentage of children less than 5 years of age in this area is 9.4% compared to 7.2% for the remainder of the city. This area contains 15.4% of the total population of New Bedford.
The prevalence of lead poisoning in children of New Bedford ages 6 months to 6 years was the third highest among those municipalities that had greater than 5 cases of lead poisoning (MDPH 1989, 1991). The prevalence of lead poisoning (serum blood lead levels greater than 25 ug per 100 milliliters of blood) was 8.7 cases per 1,000 children screened. These are the results of monitoring conducted between October 1, 1988 and September 30, 1989. The lead poisoning prevalence for the entire state during this period was 3.5 cases per 1,000 children screened. When lead poisoning rates were monitored throughout the state from July 1, 1990 through June 30, 1991, the rate for New Bedford subsided to 6.3 per 1,000 children screened. This rate is still higher, however, than that of the state at 3.0 cases per 1,000 children screened. A finer analysis of lead poisoning prevalence will be conducted in the near future by MDPH. It is anticipated that the actual localities of the lead poisoning cases will be determined in order to determine those areas where the greatest risk of lead exposure is currently occurring.
In summary, exposure to lead emissions from the incineration of PCB (and lead) contaminated sediment poses the largest health concern with respect to the incineration process. The efficient destruction and removal of PCBs has been previously demonstrated if incineration is conducted under proper operating conditions, which include adequate temperature and burning time as well as oxygen availability to the materials being burned. Maintenance of proper incinerator temperatures and adequate cooling of incinerator exhaust prior to entrance to the air pollution control device will prevent the hazardous formation of dioxins and furans. Heavy metals such as lead and cadmium are not destroyed in the incineration process but instead volatilize at the incinerator temperatures and condense on fly ash as it cools. Efficiencies of metal contaminated fly ash capture ranging between 77 and 99.9% have been reported (Lee, 1988, Denison, 1990). In addition, lead removal efficiencies using results of trial burns conducted on the incinerator that is actually planned to be used at the site (Weston, 1992) are estimated to be as high as 99.96%. The efficiency of capture is largely dependent upon the adequate cooling of incinerator exhaust prior to entry into the selected air pollution control device.
USEPA is planning to conduct modelling of the incinerator emissions plume in order to estimate human exposure to these emissions. Uncertainty may be, however, inherent in this modelling since it is based on parameters that change on a daily basis. Ambient air lead monitoring near ground level before and during the incineration process will provide an indication of the extent to which human populations are exposed to airborne contaminants which may or may not be associated with incineration emissions. Such monitoring will enable environmental officials to consider possible sources of lead contamination in air and possibly take corrective actions. This is especially important when it is considered that the incineration will be conducted in a densely populated area where other routes of environmental lead exposure may currently exist.
Exposure to PCBs released to ambient air during the dredging process may also occur. The Engineering Feasibility Study conducted by the U.S. Army Corps of Engineers indicated that PCB levels increased in ambient air when dredging was ongoing compared with those PCB levels that were detected in the same area before dredging activities began. It is expected that PCB levels will increase most dramatically at the point where dredging is ongoing. These levels should also subside after dredging activities cease.
Hydrogeologic testing near the Aerovox plant, which sits on a bluff, has indicated that ground water flow at the plant is towards the harbor to the east and the bay in the south. The water table at the plant is 10 feet below land surface but can vary according to season with increased water elevations occurring in the spring. This is attributable to the increased precipitation and ground thawing that takes place during this period. During periods of low ground water flow when the water table is depressed, it is possible that harbor waters can recharge ground water in the area. Exchanges between ground and surface water also occur as a result of tidal fluctuations with harbor waters charging the ground water during periods of high tide. It is not expected that this exchange would occur at a point significantly inward since no tidal fluctuations were observed during the limited ground water topography studies that were conducted at a well drilled 300 feet inward on the Aerovox site (NUS, 1984).
The ground water system in the area is comprised of three zones. A ground water system flows through the underlying bedrock. A consolidated system in glacially deposited soils is separated from a shallow perched system by an impermeable peat layer of varying thickness. This shallow system flows through basal till consisting of boulders, silts and sand. In the absence of volatile organic contamination, migration of PCB contamination via bedrock ground water is not likely due to the strong tendency for these compounds to adhere to the intervening soil layers that overlie the bedrock zones.
Municipal drinking water wells that serve the Greater New Bedford area are situated at least four miles upgradient to harbor waters and a plausible route of contamination of these wells by harbor waters can not be identified. Residents are therefore not at risk of exposure to contaminated harbor waters via ingestion of these water supplies.
At least one private groundwater well situated in Fairhaven 1,800 feet inland of harbor waters has been identified. It is remotely possible that a hydraulic connection exists between waters that charge this well and contaminated harbor waters. This connection, however, has not been established. It is also not known how waters drawn from this well are used. It is therefore uncertain whether usage of water drawn from this well constitutes an exposure pathway.
Access to the "hot-spot" areas could possibly be attained by encroaching on the secured Aerovox Plant grounds and climbing down the steep embankment to the shoreline. These areas can also be approached either from the north or south by wading or walking from the freely accessible shoreline. The shoreline can be approached from either the cove one mile south of the "hot-spot" area or the Wood Street Bridge, 1,200 feet north of the "hot-spot" area. Access to these areas from the wetlands in the east would entail wading or swimming a distance of at least 500 feet. Individuals accessing these areas can be exposed to sediment contaminants via dermal contact. Children between the ages of one and five years are generally most prone to contaminant exposure via ingestion of soils or sediment. It would be, however, extremely difficult for children in this age group to access shoreline sediment without first sustaining physical injury from falling or drowning. Older individuals who would be more likely to gain access to the "hot-spot" areas would also be less likely to deliberately ingest soil or sediment.
The fence between the playground and the shoreline at Sawyer's Cove is in disrepair and the shore at this point is freely accessible by older children and young adults. It is uncertain whether children between the ages of one and six years can and actually do access the area near the playground where lead contaminated sediment was detected.
The extent of migration of contaminated soils via re-suspension or aerosolization also can not be assessed since the grounds that could plausibly contain these soils were not accessible for inspection. Contaminated sediment from the shoreline could migrate inland in the event of a flood. Harbor waters attained a height of 12 feet during a hurricane in 1938 and caused considerable damage. A hurricane barrier has since been constructed along the New Bedford and Fairhaven shores of the lower harbor. It is possible, however, that flood waters could inundate the factory grounds and conceivably some of the residential areas further inland. Contaminated sediment could then be deposited in these areas by receding flood waters. This occurrence is, however, unlikely since the factory is above the 100-year flood plain.
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.
Based on studies of PCBs fed to laboratory animals, continued ingestion of PCBs is associated with increased cancer risk (ATSDR, 1991). Rats and mice who were fed PCBs for intermediate (14 to 365 days) and chronic (greater than 365 days) periods of time had increased incidence of liver tumor development over the course of their lifetime. The PCB doses to which these animals were exposed were significantly higher than those that would result from ingestion of harbor biota. The results of these studies indicate, however, that a finite risk of cancer is associated with regular ingestion of PCB contaminated biota. This risk increases as higher amounts of PCBs are ingested such as those detected in seafood harvested from restricted waters. Since PCBs accumulate in the tomalley of the lobster, ingestion of this organ from lobsters harvested from restricted waters would result in an increased cancer risk. There are, however, no human health data yet available that associates ingestion of these levels with increased cancer risk (ATSDR, 1991).
Non-cancer risks are also associated with ingestion of PCB levels detected in biota within harbor confines. Chronic exposure (greater than 365 days) to maximum PCB levels detected in clams, lobsters and flounder within the harbor walls has been associated with diminished immune function. Production of certain antibodies was observed in monkeys who were chronically (greater than one year) exposed to PCB levels such as those that would be expected if harbor seafood were continuously ingested. Increased prevalence of low birth weight was observed among infant monkeys who incurred in utero exposure to PCB levels similar to those that would be expected upon chronic consumption by pregnant women of lobsters (muscle and tomalley) caught from restricted waters. No human studies have yet conclusively observed these effects (ATSDR, 1991).
Daily ingestion of maximum cadmium contamination levels detected in clams harvested from waters immediately outside of New Bedford Harbor might pose a public health concern. Human studies have demonstrated an association between exposure to similar levels especially in children for an extended period of time with an increased risk of kidney dysfunction (ATSDR, 1991). This exposure scenario of ingesting the maximum cadmium levels on a daily basis for an extended period of time is, however, extremely unlikely.
Maximum lead contamination levels detected in clams harvested in the harbor region approach those necessary to significantly elevate serum lead levels if regularly ingested. Elevated blood lead levels in children have been shown to elicit adverse neurobehavioral effects. Increased serum lead levels in adult males have also been associated with elevated blood pressure. Due to the variability in both the reported fish intake from the GNBHES participants and the lead contamination levels detected in seafood harvested in and around New Bedford Harbor, the extent of the health concern posed by ingestion of lead contaminated seafood can not be accurately assessed. It is possible, given the maximum lead levels detected in seafood harvested from the area, that children and adult males could ingest sufficient amounts of lead that would result in the aforementioned adverse health outcomes.
Acute copper toxicity can result in stomach pain, nausea, vomiting and diarrhea. Copper levels detected in fish approach those necessary to induce these effects in extremely sensitive individuals if ingested. These amounts, however, do not significantly exceed normal dietary copper intake for the American population. Ingestion of copper detected in flounder harvested from the surrounding waters of the New Bedford Harbor poses a more significant health concern in those individuals afflicted with Wilson's Disease. Individuals with this genetic disorder accumulate copper in the liver and central nervous system due to an inability to excrete excess serum copper. If copper exposure remains unchecked in these patients, brain damage, psychiatric disturbances or liver cirrhosis will follow (Scheinberg, 1983). Long term exposure to copper levels detected in seafood harvested from area waters is not associated with chronic adverse health effects in humans with normal copper metabolism.
PCB contamination levels detected in the "hot-spot" regions approach or exceed those necessary to inflict acute liver damage if sufficient amounts of sediment are ingested. It is plausible that children between the ages of one and five years who are prone to soil ingestion could ingest such amounts. Ingestion of contamination levels detected in sediments from the cove area could also elevate serum lead levels in children. If this activity were to occur on a regular basis, neurobehavioral function may be negatively impacted. As previously discussed, however, it is unlikely that children between those ages could access the "hot-spot" areas regions without first sustaining other physical injury. Since the fence at the playground is in disrepair, however, children may be able to access shoreline sediments where lead contamination was detected.
No known hazards are associated with acute exposure (0 to 14 days) via dermal contact to PCB levels detected in estuary, harbor or bay waters. Intermediate dermal exposure (14 to 365 days) to PCB levels similar to those detected in shoreline sediments near the "hot-spot" area has been associated with suppression of immune system functions. Immune system response to injection of foreign matter (sheep red blood cells) into monkeys was depressed after daily exposure for eleven months to those dosages that would be expected if shoreline surfaces near the "hot-spot" areas were contacted frequently. Diminished production of certain antibodies was observed in monkeys when they were chronically (greater than 365 days) exposed to PCB levels similar to those detected in shoreline sediments near the "hot-spot" region. There have been no human studies to date that observed immune system suppression upon exposure to PCB levels similar as those detected in this area (ATSDR, 1991).
Formation of gastrointestinal cysts, fat accumulation in liver, and acne development were effects also observed in monkeys exposed to PCB levels similar to those expected in those humans repeatedly accessing surface along the shoreline of the "hot-spot" areas. Decreased thyroid hormone secretion and increased bone density were observed in rats exposed to these levels. No studies have been identified that have observed gastroenterologic or hormonal effects in humans following exposure to these levels of PCBs. Human dermal contact with PCB contaminated sediments may result in the development of skin irritations. The levels at which this occurs, however, is not known (ATSDR, 1991). No animal studies have been located where adverse non-cancer health effects have occurred following dermal exposure to PCB levels such as those detected in regions of the harbor south of the "hot-spot" area.
Repeated long-term exposure to PCB levels such as those detected in surface sediments in all areas has been associated with an increased cancer risk in animal studies. Exposure to extremely high PCB levels in rats has shown to increase risk of liver cancer development (ATSDR, 1991). Human risk estimates are projected from these studies. No conclusive human evidence currently exists demonstrating cancer risk associated with dermal contact with PCB levels such as those detected in surface sediments at the site. It is important to note that based on animal studies, the risk of cancer development increases with exposure to increasing PCB levels. The cancer risk associated with repeated long term surface sediment contact near the "hot-spot" is therefore significantly greater than that risk associated with surface sediment contact at the southern end of the harbor.
No acute adverse health effects are associated with exposure to PCB levels detected in ambient air monitored at or near the Hot-Spot area. Based on animal studies, chronic exposure to PCB levels in ambient air at the Hot-Spots and surrounding areas may be associated with elevated risk of cancer development.
No adverse health effects have been associated with PCB exposure that would occur if harbor waters were accidently ingested.
This study was originally intended to quantify the prevalence of PCB exposure among residents of the Greater New Bedford area as determined by serum PCB levels. Those individuals with serum PCB levels greater than 30 ppb were considered to have significant PCB exposure since it has been estimated that 99% of unexposed persons in the United States have serum PCB levels lower than this value (Stehr-Green, 1986). Blood pressure (systolic/diastolic) measurements were also obtained from the 840 randomly selected participants in this study to determine whether or not an association between serum PCB levels and blood pressure exists. A second phase of this study was also planned where the results of more detailed clinical investigations conducted on a cohort of 150 individuals with serum PCB levels greater than 30 ppb would be compared with those of a cohort of the same number of individuals with serum PCB levels less than 10 ppb. These monitorings would include measurements of liver and immune function, lipid metabolism and evidence of neurotoxicity.
Preliminary analysis of serum PCB levels conducted on 35% of the randomly sampled participants revealed that an insufficient number of individuals with elevated serum PCB levels could be identified via this method of selection. In order that the second phase of the study could be completed, it was necessary to recruit a second cohort of individuals at high risk of PCB exposure. This group was identified using listings from city/town halls and the Massachusetts Division of Marine Fisheries, of those individuals issued recreational fishing or lobstering licenses in the area. Individuals occupationally exposed to PCBs were identified from pilot studies. The "enriched" sample consisted of 110 individuals selected in this manner.
Only 1.3% (n=11) of the 840 randomly selected GNBHES participants demonstrated serum PCB (Aroclor 1254) levels greater than or equal to 30 ppb. In addition the majority (64%) of the participants in the prevalence study reported that they consume no locally caught contaminated seafood. Only 15.4% of these study participants reported that they currently consume seafood that has been locally caught by themselves, their relatives or friends. Diastolic and systolic blood pressure levels in this study group did not appear to be elevated. After selecting individuals with a presumed high risk of PCB exposure, a sufficient number of individuals with serum PCB levels greater than 30 ppb still could not be identified and as a result the second phase of the project could not carried out.
Although the prevalence study was not designed to associate serum PCB levels with consumption of locally caught fish, trends were observed in comparisons of serum PCB levels between those individuals with increased consumption of locally caught fish among the enrichment sample. The enriched sample, which consisted of individuals who are more prone to consumption of fish that is locally caught had an increased mean serum PCB level (13.3 ppb, n=110) compared to the randomly selected prevalence sample (5.8 ppb, n=840). In both samples, mean serum PCB levels increased with the frequency of locally caught fish consumption. The relationship between local fish consumption and serum PCB levels achieved statistical significance in the prevalence sample but was not maintained after controlling for age. This was due to the insufficient number of subjects that would be necessary to observe the separate effects of age and fish consumption on PCB accumulation (MDPH, 1987).
A registry has been established within the MDPH of all individuals in whom elevated serum PCB levels were detected during state sponsored monitoring programs. Serum PCB levels as well as overall health of these individuals is monitored by this exposure registry.
Blood and urine samples were collected from ten percent of the participants in both the GNBHES prevalence and enrichment samples (n=106). This monitoring was conducted in order to assess participants' exposure to lead, mercury and arsenic. Blood lead levels and urinary mercury levels were within the ranges of values normally exhibited by adult urban residents who are not occupationally exposed. Ten subjects did have urinary arsenic outputs at levels considered to approach the upper limit of what is considered to be normal. These levels did not, however, indicate excessive exposure to arsenic via ingestion of contaminated seafood (Miller, 1991b).
The prevalence of lead poisoning in children of New Bedford ages 6 months to 6 years was the third highest among those municipalities that had greater than 5 cases of lead poisoning. (The exclusion of rates observed in those municipalities with fewer than 1,000 children within this age group was made in order to avoid the consideration of those spuriously inflated prevalence rates that would result from small numbers of cases within these townships.) The prevalence of lead poisoning (serum blood lead levels greater than 25 ug per 100 milliliters of blood) was 8.7 cases per 1,000 children screened. These are the results of monitoring conducted between October 1, 1988 and September 30, 1989. The lead poisoning prevalence for the entire state during this period was 3.5 cases per 1,000 children screened. When lead poisoning rates were monitored throughout the state from July 1, 1990 through June 30, 1991, the rate for New Bedford subsided to 6.3 per 1,000 children screened. This rate is still higher, however, than that of the state at 3.0 cases per 1,000 children screened.
The City of New Bedford has a predominance of housing units (86% of total) that were constructed prior to 1950. Children living in these units are at increased risk of lead exposure via ingestion of flaking paint that contains elevated lead concentrations.
This program was established to determine serum PCB levels of those subjects who were not selected into the GNBHES but were concerned about possible exposure to PCBs. Of the twenty-eight program participants whose serum PCB levels were monitored, four had serum PCB levels greater than 30 ppb. All four of these individuals reported working in the electronics industry. One of these four individuals also reported consuming locally caught seafood more than five times in her life. Seven program participants reported consumption of locally caught seafood (greater than five times in their life span) and only this one individual demonstrated an elevated serum PCB level.
As a result of citizen concern over possible elevated cancer risk resulting from exposure to PCBs and for purposes of this public health assessment, the Community Assessment Unit within the MDPH evaluated liver and bladder cancer incidence as well as incidence of leukemia among New Bedford residents. Utilizing data from the Massachusetts Cancer Registry, Standardized Incidence Ratios (SIRs) were generated. These ratios serve to compare the number of cancer cases in the community of concern with that which would be expected based on the statewide age-specific cancer experience. SIRs greater than 100 indicate that the number of cancer cases in the community under investigation is greater than that which would be expected based on the statewide experience. Those SIRs less than 100 are indicative of a cancer incidence experience less than that which would be expected based on the statewide rates. The SIRs for all New Bedford citizens were 91, 95 and 102 for liver cancer, bladder cancer and leukemia respectively. Liver cancer, bladder cancer and leukemia SIRs for female residents of New Bedford were 136, 102 and 114 respectively. The male cancer SIRs in New Bedford were as follows: liver cancer-65; bladder cancer-92; leukemia-91. None of the increases or decreases in cancer incidence indicated by the SIRs achieved statistical significance at the .05 level meaning that the probability that observed increases or decreases are due to chance is greater than 5%.
We have addressed the community concerns about health as follows:
- When will harbor waters reopen for fishing?
It is not possible to determine when fishing can safely resume within harbor and upper bay waters. Seafood must continue to be monitored until it can be demonstrated that PCB levels have subsided to those below the tolerance limits established by the FDA. The proposed removal of PCB-contaminated sediments detected in the harbor will shorten the time necessary to attain FDA approved PCB levels. The exact extent to which the remedial plan will accelerate the depuration process can not be determined in the absence of actual monitoring of harbor seafood.
- Is the fish served at local restaurants safe to eat?
The fish served at local restaurants is subject to the same regulations as that sold in any market. Fish caught in open bay and ocean waters, which is the source of most commercial catches in New England, are not impacted by the PCB contamination detected in New Bedford Harbor. In addition, no fishing of any kind is currently permitted within harbor waters. Local and state health and environmental officials enforce these regulations to assure that any exposure to PCBs via ingestion of contaminated seafood is not ongoing.
- What adverse health effects can result from the consumption of local fish?
Based on animal studies, regular consumption of seafood with elevated PCB levels is associated with an increased risk of cancer development. Human studies have not associated any adverse health effects with ingestion of PCB levels detected in harbor seafood. Based on the results of the GNBHES, PCB levels in blood may become elevated as a result of ingestion of contaminated harbor seafood.
- Are cancer rates elevated in the New Bedford Area as a result of PCB contamination of New
The Community Assessment Unit within the MDPH has investigated cancer rates for the City of New Bedford. There were no significant elevations among New Bedford citizens of those cancers which the scientific community has associated with PCB exposure.
- Is the proposed incineration of PCB-contaminated sediments safe?
Exposure to possible lead emissions from the incineration of PCB (and lead) contaminated sediment poses the largest health concern with respect to the incineration process. The efficient destruction and removal of PCBs has been previously demonstrated if incineration is conducted under proper operating conditions, which include adequate temperature and burning time as well as oxygen availability of the materials being burned. Maintenance of proper incinerator temperatures and adequate cooling of incinerator exhaust prior to entrance to the air pollution control device will prevent the hazardous formation of dioxins and furans. Heavy metals such as lead and cadmium are also filtered more efficiently when the incinerator is operating under proper conditions.
USEPA is planning to conduct modelling of the incinerator emissions plume in order to estimate possible human exposure to these emissions. Uncertainty is, however, inherent in this modelling since it is based on parameters that change on a daily basis. Ambient air lead monitoring near ground level before and during the incineration process will provide an indication of the extent to which human populations are exposed to airborne contaminants which may or may not be associated with incineration emissions. Such monitoring will enable environmental officials to consider possible sources of lead contamination in air and possibly take corrective actions. This is especially important when it is considered that the incineration will be conducted in a densely populated area where other environmental lead exposure may be currently ongoing.