Review of Environmental Sampling Data
PORTSMOUTH MANUFACTURED GAS PLANT SITE
(a/k/a COMMONWEALTH GAS SERVICES)
PORTSMOUTH, PORTSMOUTH COUNTY, VIRGINIA
The Virginia Department of Environmental Quality (DEQ) requested that the Agency for Toxic Substances and Disease Registry (ATSDR) review environmental sampling data collected on and near the site of the former Portsmouth Manufactured Gas Plant, Portsmouth, Virginia, and identify potential health hazards to past and current residents .
The site is located northwest of the intersection of Effingham Street and Crawford Parkway, with Washington Street to the east and the U.S. Naval hospital to the north (Figure 1). A manufactured gas plant was operated on the site from 1856 through 1956. In the early 1960s, residential apartments and single -family houses were built on and near the decommissioned site. Environmental activities including investigations, assessments, and remediations have been conducted at the site since 1992 [2-3]. Following are descriptions of some of these activities.
- Phase I and II investigationsIn 1992, MARCOR Delmarva, Inc., conducted limited investigation and surface soil sampling for one of the apartment complexes on the site.
- Initial site investigation and health risk assessmentIn 1993, Geraghty & Miller, Inc., (G&M) collected soil vapor samples, surface soil samples, and groundwater samples to evaluate human health risks for current residents.
- Remedial investigation and corrective measures studyIn 1993 and 1994, G&M collected additional samples of groundwater, subsurface soil, and storm sewer water to complete the human health risk evaluation, and to identify and select appropriate remedial actions for the site.
- Supplemental groundwater sampling and monitoringIn 1995 and 1999, Environmental Resources Management (ERM) collected additional groundwater samples from both monitoring and nonpotable wells to confirm findings observed previously.
- Surface and residential soil samplingIn 1998 and 1999, ERM collected more surface soil samples (0-6 inches) to better define the concentrations of contaminants at exposure points.
- Indoor and outdoor air samplingIn 2000 and 2001, indoor and outdoor samples were collected from different locations at the site to evaluate risks associated with inhalation exposures from soil gas migration.
- Site investigation and confirmation samplingFrom fall 2001 to summer 2002, the RETEC Group, Inc. (RETEC), conducted a comprehensive site investigation that included more than 500 samples for soil, groundwater, and air.
- Remediation activitiesRemediation activities conducted at the site include free product (mainly diesel fuel) recovery from monitoring wells, storm sewer pipe lining to reduce odors and sheens observed at the storm sewer outfall in the Elizabeth River, irrigation well replacement with deeper wells or connections to the public water system, and surface soil removal in the Patio Plaza courtyard area and in the backyards of some residential houses on Washington Street.
Table 1 is a summary of sampling activities and chemical analysis for all media samples at the site. The purpose of this health consultation is to review environmental sampling data and identify potential health hazards associated with air, groundwater, and surface soil exposure pathways for specific locations on the site.
The potential health effects from environmental exposures depend on many factors such as type and amount of contaminants, route and duration of exposure, amount of contaminants absorbed by the body, site-specific conditions, genetic factors, and individual lifestyles. ATSDR provides public health advice on the basis of a review of the toxicologic literature, a comparison of levels of environmental contaminants to published health standards, an evaluation of exposure routes and duration, and the populations exposed.
Contaminants may be contacted through activities that involve touching them (dermal contact), breathing them in (inhalation), or accidentally drinking or eating them (ingestion). A completed exposure pathway is said to exist when information shows that people have come into contact with a contaminant in soil, air, or water. Completed exposure pathways can be either in the past or the present.
ATSDR uses different comparison values (chemical-specific, health-based standards and guidelines) derived by various government agencies to screen contaminants and identify those that could require further evaluation of their potential to cause adverse health effects. While concentrations at or below the relevant comparison values might reasonably be considered safe, concentrations above these values will not necessarily cause harm. ATSDR uses site-specific exposure scenarios and performs a more in-depth evaluation for substances with detected concentration levels above the screening values.
Information on ATSDR comparison values and definitions is provided in Appendix A.
Environmental sampling results were grouped into three categories: air, groundwater, and surface soil. The results are discussed in the following paragraphs.
Air Sampling Results
Since 1993, ninety-five samples have been taken of soil vapor and indoor and outdoor air at the site. Air samples were analyzed for volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), total petroleum hydrocarbons, and mercury vapor. Air sampling included soil vapor sampling and indoor and outdoor air sampling for the Patio Plaza Apartments and Gates Apartments, air sampling during the site investigation, and mercury vapor sampling for one residence.
Soil vapor sampling
During the initial site investigation and health risk assessment in 1993, there were 34 soil vapor samples (also known as soil gas samples) collected to characterize the concentrations of site-related chemicals volatilized from soil. Additional soil vapor samples (6) were collected in early 2001 at the Patio Plaza Apartments and the Gates Apartments to verify the potential for gas migration. Site-related chemicals identified include BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), polycyclic aromatic hydrocarbons (PAHs), and other VOCs and SVOCs. Soil vapors can enter residences and other buildings through foundation cracks and gaps, mechanical ventilation systems, and leakage areas (for example, utility entry points, construction joints, and drainage systems). They can also enter though mechanical ventilation systems and are affected by pressure differences between the inside and outside of buildings. Soil vapor monitoring results do not provide actual measurements of concentrations of contaminants that people may inhale. Therefore, the results of the soil vapor monitoring were used in setting up both indoor and outdoor air monitoring to evaluate air contamination at points of exposure.
Indoor and outdoor air sampling for the Patio Plaza and Gates apartments
In November 2000 and January 2001, indoor and outdoor samples were collected from different site locations to evaluate hazards associated with inhalation exposures from soil gas migration. Three background samples were taken outdoors. Six indoor air samples were collected at the Patio Plaza and Gates apartment complexes. Samples were analyzed for VOCs following EPA method TO-14A guidelines. BTEX and 13 other VOCs were detected. With the exception of benzene and methylene chloride, all of the chemicals detected were below their applicable health-based guidelines. Benzene and methylene chloride were detected at average levels of 0.89 µg/m3 and 10.97 µg/m3, respectively. ATSDR established acute and intermediate environmental media evaluation guides (EMEGs)/minimal risk levels (MRLs) for benzene as 160 µg/m3 and 13 µg/m3, respectively . The ATSDR acute EMEG/ MRL for methylene chloride is 2,084 µg/m3, and the intermediate and chronic EMEG/MRL is 1,042 µg/m3. Therefore, the levels of benzene and methylene chloride detected in samples from the Patio Plaza and Gates apartments were not at levels likely to cause adverse noncarcinogenic health effects for short-term, intermediate term, or long-term exposures.
ATSDR has developed cancer risk evaluation guides (CREGs) to aid in evaluating carcinogenic effects. The CREG for benzene is 0.1 µg/m3, and the CREG for methylene chloride is 3 µg/m3 . CREGs are estimated contaminant concentrations in air that would be expected to cause no more than one excess case of cancer in a million persons exposed over a lifetime. ATSDR used the EPA region 3 cancer slope factors (CSFs) for a cancer risk evaluation. CSFs are based on conservative models and assume continuous, lifetime exposure. A conservative risk evaluation concluded that residents exposed through inhalation to these two chemicals at these levels throughout their lifetimes would have no apparent increased risk of developing cancer. This conservative risk evaluation is discussed in more detail in Appendix B.
Air sampling during the site investigation
The most recent air sampling data was collected by RETEC during the site investigation and confirmation sampling conducted from fall 2001 to the summer of 2002. Forty-two samples were collected for VOC analysis following EPA method TO-14A guidelines. The air samples were analyzed for 64 compounds. Thirty-seven of these 64 compounds (57%) were detected. Table 2 provides a summary of all air data for the site investigation and confirmation sampling.
All VOCs were detected at levels below those likely to cause adverse noncarcinogenic health effects for short-term, intermediate term, and long-term exposures. However, concentrations of five VOCs (1,3-butadiane, benzene, chloroform, methylene chloride, and tetrahydrofuran) exceeded their respective CREGs. The Virginia Department of Environmental Quality specified as an area of special concern the indoor air quality at the Patio Plaza apartments. Table 3 provides a list of the locations of the indoor air sampling at the Patio Plaza apartments. On the basis of the following site-specific exposure scenarios and the conservative risk evaluation, it is unlikely that an increase in cancer incidence would occur in the community.
- The average concentrations of benzene and chloroform are 5.46 µg/m3 and 5.86 µg/m3, respectively, for the Patio Plaza area.
- 1,3-butadiene (11 µg/m3) and tetrahydrofuran (27 µg/m3) were detected only once at one sampling location (IAPP31) in the Patio Plaza area. Continuous lifetime exposure to 1,3-butadiene is highly unlikely as this chemical was detected in only one sample. Short-term, intermittent exposures to the reported concentration of 1,3-butadiene would not be expected to pose a health hazard.
- The highest concentrations (9,900 µg/m3, 590 µg/m3, and 520 µg/m3) of methylene chloride were found in one sampling location (IAPPD). The average concentration of methylene chloride for all other sampling locations was below the level of health concern.
- Previous air samples taken from the same building in which the IAPPD sample was taken detected concentrations of methylene chloride below the level of health concern.
- Methylene chloride is a colorless liquid used widely as an industrial solvent and as a paint stripper. The chemical may be found in some spray paints, automotive cleaners, pesticides, and in other household products . Methylene chloride is the most common laboratory analysis artifact introduced in laboratory sample preparation . Therefore, multiple sources may contribute to the high concentrations of methylene chloride in the IAPPD sample.
- There were other VOCs (for example, 2-proponol, acetone, ethanol, and toluene) detected at relatively high concentrations from sampling locations IAPP31 and IAPPD. Although it is possible that high VOC concentrations were caused by recent building maintenance activities (for example, applying pesticides, painting, or installing new carpets) during the time of sampling, additional samples should be taken to ensure that the levels of VOCs are safe for future residents.
Mercury vapor sampling
Mercury occurs naturally in several forms and is typically found in the environment at very low levels. The average ambient air concentration of mercury reported values in the United States. range from approximately 0.010 µg/m3 to 0.020 µg/m3 . In December 2001, four vapor samples were collected from one residence and analyzed for total mercury following NIOSH (National Institute for Occupational Safety and Health) method 6009. The average mercury concentration was 0.9 µg/m3. ATSDR's inhalation MRL for chronic mercury exposure is 0.2 µg/m3 . This chronic MRL is an estimate of daily human exposure to mercury that is likely to be without an appreciable risk of adverse noncarcinogenic health effects for the entire life of a person (estimated as 70 years). It is based on a lowest-observed-adverse-effect level (LOAEL) for hand tremor induced by industrial exposure in humans, with a safety factor of 30 for human variability and use of a minimal LOAEL . Although the average mercury concentration is above the respective MRL, actual exposure to mercury in this home would likely be less than the measured level for the following reasons.
- Indoor air samples were taken when indoor-outdoor air exchange was low (the house was not occupied and the doors and windows were kept closed during the sampling); the results therefore represent a worst-case scenario. The actual average daily mercury exposure for residents would be less than that indicated by the sample results.
- Mercury vapor concentration is likely to be higher near the floor. Adults with higher breathing zones may be exposed to lower concentrations of mercury. When the house was occupied, there were no children living there.
- It is unlikely that residents would be exposed throughout their entire lifetimes. Their risk of adverse health effects from exposure to mercury at the location would therefore be reduced.
- Recent remediation activities in the backyard (surface soil removal and replacement) could reduce the level of mercury concentration in the house. However, the level of mercury concentration in the house should be verified for the safety of future residents, especially for young children and pregnant women. Additional information on exposure and children is given in the Child Health Consideration section.
Epidemiologic studies found no evidence that linked inhaling metallic mercury to cancer in humans .
Groundwater Sampling Results
One hundred and twenty-four groundwater samples have been taken on the site since 1993. The samples were collected from 26 monitoring wells and 13 residential irrigation wells. Water samples were analyzed for 182 substances including metals, VOCs, SVOCs, total petroleum hydrocarbons, diesel range organics, gasoline range organics, and cyanide. Of the 182 substances, 49 (27%) were detected in the irrigation wells. Shallow groundwater (4 feet below ground surface) was heavily impacted by past operations and is not the source of drinking water for the community. Area groundwater in the area is used for limited residential irrigation.
ATSDR was asked specifically to evaluate past exposure for an abandoned irrigation well. The well was sampled in June 1993 and November 1999 (sample location NPW214WAS). Of the 34 substances analyzed for, 16 different substances (47%) were detected. Among the detected chemicals, nine were VOCs. With the exception of benzene, concentrations of all detected chemicals were below their applicable health-based guidelines. Benzene was detected at concentrations of 200 µg/m3 and 270 micrograms per liter (µg/L). The ATSDR drinking water CREG for benzene is 0.6 µg/L. The CREG represents an estimated benzene concentration in water that would be expected to cause no more than one excess case of cancer in a million persons exposed using default exposure assumptions (such as an ingestion rate of two liters of water per day over a lifetime for adults). However, the most likely exposures to contaminated groundwater at the location in the past were through infrequent dermal contact and through inhalation of vaporized VOCs by residents working in their yards. Following are site-specific exposure scenarios. Infrequent exposures occurring in these situations were not likely to cause any adverse health effects.
- People who use groundwater from shallow wells for watering plants or gardens or in doing other yard work might have occasional dermal contact. Using conservative exposure risk assumptions, the levels to which persons would be exposed were found to be far below the applicable health-based guidelines. (Appendix B provides information on exposure dose calculations.)
- Water might be sprayed into the air during gardening or other watering activities. This could result in the transfer of benzene from water to air and subsequent inhalation exposure. This exposure pathway is not considered to be significant, however, because the small amount of benzene in the water would be dissipated into a large volume of outdoor air.
Table 4 provides a summary of all water data for sample location NPW214WAS.
Surface Soil Sampling Results
A potential exposure pathway for residents at the site is the accidental ingestion (swallowing) of contaminated soil. This exposure can occur when people have direct contact with soil in their environment. For instance, children playing outside or crawling on floors and adults working in yards and gardens may get contaminated soil or dust on their hands. These individuals can then accidentally swallow contaminants when they put their hands on or into their mouths. Because both people and pets can track contaminated soil into their homes, exposure can occur while people are in their homes as well as when they are outside. Factors that affect whether or not people have contact with contaminated soil include the amount of grass cover, weather conditions, the amount of time spent outside, and personal habits. While dermal and inhalation exposure can sometimes be a concern for soil and dust, the primary pathway of concern in a nonoccupational setting is ingestion.
Approximately 600 soil samples, both surface and subsurface, were taken at this site, starting in 1992. Soil samples were analyzed for VOCs, SVOCs, total petroleum hydrocarbons, metals, and total and free cyanide. ATSDR evaluated surface soil (0-12" deep) sample results for locations of concern at the site. Surface soil sample data are grouped into three categories (arsenic; lead and mercury; and all chemicals in the Patio Plaza area) and discussed in the following sections.
Arsenic is a naturally occurring element, present at low levels in soil, water, food, and air throughout the world. The U.S. Geological Survey reports the background range of arsenic in soil and other surficial materials in the United States as less than 0.1 mg/kg to 97 mg/kg, with a mean value of 7.2 mg/kg . The background level for arsenic in soil in Virginia ranges from 3 mg/kg to 7 mg/kg (Figure 2) .
Twenty-four surface soil samples were taken from July 1998 to August 2001 from a private residence that was a location of concern . Arsenic concentrations ranged from 6.6 mg/kg to 110 mg/kg, with an average of 37.5 mg/kg (Table 5).
The ATSDR chronic EMEGs for adults and children are 200 mg/kg and 20 mg/kg, respectively . There were 10 surface soil samples (42%) that contained arsenic at levels above 20 mg/kg, exceeding the chronic EMEG for children. ATSDR used information from a Taiwanese drinking water study to develop this EMEG and determine the lowest intake amount likely to result in an adverse noncancerous health effect (lowest-observed-adverse-effect level or LOAEL). In this case, the LOAEL is a daily intake of about 800 micrograms of arsenic a day. Because arsenic is more bioavailable in drinking water than in soil, the soil EMEGs for arsenic, which do not take bioavailability into account, are more conservative than the drinking water EMEGs. In addition, most of the residential yard was well covered by vegetation. Therefore, ATSDR does not expect adverse health effects to occur in either children or adults who were exposed in the past to the levels of arsenic found in the soil at the residence.
To prevent current and future exposure, the surface soil in this location was recently removed and replaced with clean fill material as part of the site remediation activities. Four confirmation samples and two backfill material samples taken after the removal indicated that the arsenic concentrations (estimated highest value is 2.6 mg/kg) were well below levels of health concern.
Lead and Mercury
Lead is another naturally occurring element found in small amounts in the earth's crust. The general population in the United States is exposed to lead in air, food, drinking water, soil, and dust. Multimedia contamination of lead in residential areas results from many different sources such as lead-based paint, old plumbing fixtures, and from soil and dust contaminated by combustion of leaded gasoline and other industrial sources . The background level for lead in soil in Virginia ranges from approximately 13 mg/kg to 23 mg/kg (Figure 3) .
Health effects of lead exposure depend on the concentration of the lead, the amount of lead absorbed by the body, the duration of the exposure, and on the age and nutritional status of the exposed individual. The main target for lead toxicity is the nervous system . For adults, long-term exposure to high levels of lead, mainly through occupational exposure, has resulted in brain and kidney damage; weakness in fingers, wrists, or ankles; decreased performance on nervous system function tests; and a lower than normal number of blood cells . Some human studies have suggested that lead exposure may increase blood pressure, but the evidence is inconclusive. However, the connection between all of these health effects and exposure to low levels of lead is not certain . There is no evidence that lead causes cancer in humans . Children are more vulnerable to lead poisoning than adults are. Additional information on the unique vulnerability of children is provided in the Child Health Consideration section of this document.
Since 1998, 29 samples of surface soil have been collected from the residence of concern  and analyzed for lead contamination . Lead concentrations ranged from 12.2 mg/kg to 1,500 mg/kg, with an average of 385 mg/kg (Table 6).
ATSDR considers levels of lead above 400 mg/kg in residential soil to need further evaluation because of children's unique susceptibility (discussed in the Child Health Initiative section) . EPA defines health hazard levels for lead as follows: (1) more than 400 mg/kg of lead in play areas of bare, residential surface soil; (2) 1,200 mg/kg of lead (average) in bare soil in the remainder of the yard .
Of the 36 surface soil samples, 8 (22%,) were found to have lead levels above 400 mg/kg. Representatives of ATSDR, the Virginia Department of Environmental Quality, NiSource (previous owner of MTG), and the RETEC Group (NiSource's consulting firm) conducted a site visit to the residence. They observed that the backyard was not well covered with grass and that some sampling locations that had been detected as having lead levels above 400 mg/kg were relatively close to the back porch of the house, providing children with relatively easy access to the "hot spots." Therefore, for past exposures, lead-contamination in surface soil at the location presented a potential health hazard for children, particularly those younger than 2 years of age. Surface soil in this location was removed and replaced with clean fill material as part of the site remediation activities conducted in the spring of 2002. Two confirmation samples and two backfill material samples taken after the removal indicated that the lead concentrations were well below levels of health concern (Table 6).
Mercury also occurs naturally in the environment and exists in several forms (metallic, inorganic, and organic mercury). The U.S. Geological Survey reports that the background range of mercury in soil and other surficial materials in the United States is less than 0.01 mg/kg to 4.6 mg/kg, with a mean value of 0.09 mg/kg . Because most of the mercury found in soil is in the form of metallic mercury (that is, elemental mercury) and inorganic mercury (elemental mercury combined with elements such as chlorine, sulfur, or oxygen), health-related comparison values used in this document are for inorganic mercury. Thirty-six surface soil samples were taken from the residence from July 1998 to August 2001 . Mercury concentrations ranged from 0.29 mg/kg to 360 mg/kg, with an average of 42.8 mg/kg (Table 6).
Children who ingested this soil could have exceeded the acute and intermediate MRLs for mercury. (Appendix B provides information on the dose calculations on which this determination was based.) Mercury contamination in soil at the residence, however, was reportedly in the form of elemental mercury. Elemental mercury is poorly absorbed from the gastrointestinal tract, so the actual absorbed dose of mercury would be much less than the calculated amount. In addition, the oral MRLs for mercury were derived on the basis of studies in which laboratory animals were given mercuric chloride dissolved in water. Use of these MRLs would overestimate the risk of ingesting elemental mercury, which, as mentioned previously, is poorly absorbed through the gastrointestinal tract. For adults, the estimated doses are less than the oral MRLs. This would indicate that no adverse health effects would result from past exposure to surface soil through ingestion. Furthermore, the soil at the residence has been remediated and current and future exposure to the soil does not pose a health hazard.
Chemicals in the Patio Plaza Apartments
The Patio Plaza Apartments are multifamily apartment buildings that were built on the former MGP property. Overlay maps of the apartments and former MGP operations indicate that some MGP structures had been underground in the apartment area (for example, gas holders, relief holders, purifiers, and oil storage tanks). Approximately 81 surface soil samples have been taken in the Patio Plaza apartment area since 1992. Those surface soil samples were analyzed for metals, VOCs, SVOCs, and total petroleum hydrocarbons.
In 2000, surface soil in the Patio Plaza courtyard area was removed to a depth of one foot and replaced with clean fill material. Small areas of surface soil between the sidewalk and building were not replaced.
ATSDR reviewed available data for the years 1993 to 2001 to evaluate exposure prior to the remediation and exposure to soil at locations that were not remediated. Table 7 provides a summary of surface soil data for samples taken at the Patio Plaza apartment area before the removal. Table 8 provides a summary of surface soil data for samples taken at locations that were not remediated.
Before the surface soil removal, 38 surface soil samples were taken during the time period of 1993 to 1999 at the Patio Plaza apartment area. Of the 92 substances analyzed for, 52 different substances (57%) were detected in the surface soil samples. All chemicals were detected at levels below those likely to cause adverse health effects (noncarcinogenic) for short-term, intermediate term, and long-term exposure. However, concentrations of five chemicals exceeded their respective CREGs or risk-based concentrations (RBCs) . These chemicals are arsenic, benzo(a)anthracene, benzo(a)pryene, benzo(b)fluoranthene, and indeno(1,2,3-cd)pyrene. Conservative risk evaluation indicates that residents who have a continuous lifetime exposure to those chemicals via ingestion have no apparent increased risk of developing cancer; therefore, it is unlikely that an increase in cancer incidence would be observed in the community.
After the surface soil removal in August 2001, 15 soil samples were taken at locations that were not included in the remediation. Of the 46 substances analyzed for, 26 different substances (57%) were detected in the surface soil samples. Except for lead, all chemicals were detected at levels below those likely to cause adverse health effects (noncarcinogenic) for short-term, intermediate term, and long-term exposure.
Lead concentrations ranged from 20 mg/kg to 1300 mg/kg, with an average of 216 mg/kg. Only one sample indicated a lead level higher than 400 mg/kg (1300 mg/kg at location GPPP01). Lead contamination of the surface soil at that sample location could pose a potential health hazard to young children if the surface soil was uncovered and the children had access to it.
In regard to cancer effects, the surface soil samples indicated that concentrations of the same five chemicals (arsenic, benzo(a)anthracene, benzo(a)pryene, benzo(b)fluoranthene, and indeno(1,2,3-cd)pyrene) were higher than their respective CREGs or RBCs. However, conservative risk evaluation (described in Appendix B) indicates that residents who have a continuous lifetime exposure to those chemicals via ingestion have no apparent increased risk of developing cancer; therefore, it is unlikely that an increase in cancer incidence would occur in the community.
ATSDR considers children in the evaluation of all exposures, and the agency uses health guidelines that are protective for children. In general, ATSDR assumes that children are more susceptible than adults to chemical exposures. In evaluating health effects from the site-specific environmental exposures, children were considered as a special population because of their size, body weight, frequent hand-to-mouth activity, and unique susceptibility to lead and mercury exposures.
In the case of mercury exposure, children are at greater risk because mercury vapor is dense and settles near the floor in children's playing and breathing zones, and more mercury can easily pass into the developing brain of young children [13-17].
For lead and arsenic exposures, ATSDR has taken into account that children are at a greater risk for arsenic and lead poisoning than adolescents or adults on the basis of the following factors: (1) the normal behavior of children might result in higher rates of ingestion of arsenic and lead-contaminated soil and dust; (2) children might receive a higher dose of lead because they absorb more lead into their blood after ingestion and they have lower body weights than adults; (3) some children might eat soil excessively (pica behavior); and (4) the Centers for Disease Control and Prevention (CDC) and ATSDR report that blood levels in young children have been raised, on average, 5 micrograms per deciliter of blood for every 1,000 mg/kg of lead in residential soil or dust [18-19]. ATSDR has taken these factors into account in developing the conclusions and recommendations for this site.
Because of the lead contamination of the surface soil on the site, ATSDR has categorized this site as a potential Public Health Hazard. (See definition in Appendix C)
Lead contamination of the surface soil at location GPPP01 of the Patio Plaza apartment area poses a potential health hazard to young children if they have access to the area.
Past exposure to lead at the residence of concern presented a health hazard for children, particularly for children less than 2 years old. However, for adults, past exposure to lead in surface soil was unlikely to result in any adverse health effects. The soil contamination has been remediated, so current and future exposure to the soil does not pose a health hazard.
VOC concentrations (for example, 1, 3-butadiane, tetrahydrofuran, and methylene chloride) were relatively high at some Patio Plaza apartment locations. However, no adverse health effects (noncarcinogenic and carcinogenic) would be expected to result from indoor air exposures for residents who live in the Patio Plaza apartments. Additional samples should be taken to ensure that VOC concentrations are at safe levels for all residents, especially for residents at sampling locations IAPPD and IAPP31.
The average mercury vapor concentration at the residence of concern was 0.9 µg/m3. On the basis of site-specific exposure scenarios, past exposure to mercury vapor at this residence was unlikely to cause adverse health effects. However, the level of mercury concentration in the house should be verified for the safety of future residents, especially for young children and for pregnant women.
Benzene was detected at levels that exceeded the ATSDR drinking water CREG of 0.6 µg/L at sample location NPW214WAS. However, this was not a drinking water well. Water from this well used for irrigation purposes would not pose a health hazard.
The average arsenic concentration was 37.5 mg/kg at the residence of concern. Arsenic found in the surface soil did not pose a health hazard for residents. The soil contamination has been remediated, so current and future exposure to the soil does not pose a health hazard.
Collect additional indoor air samples at the Patio Plaza Apartments to verify that VOC concentrations are at safe levels for all residents.
Ensure that concentrations of mercury vapor at the residence of concern are at safe levels for future residents, especially for young children and pregnant women.
Minimize any possible exposure to lead from surface soil through a comprehensive approach such as health education, community involvement, surveillance programs, and covering of contaminated areas.
Jane Zhu, MPH
Health Consultation Section
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Jenny Wu, MS
Exposure and Disease Registries Branch
Division of Health Studies
John E. Abraham, PhD
Chief, Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Chief, Consultation Section
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Kenneth G. Orloff, PhD
Exposure Investigation and Consultation Branch
Division of Health Assessment and Consultation
Office of Regional Operations, Region 3
Agency for Toxic Substances and Disease Registry
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