HEALTH CONSULTATION

Review of Environmental Sampling Data

PORTSMOUTH MANUFACTURED GAS PLANT SITE
(a/k/a COMMONWEALTH GAS SERVICES)
PORTSMOUTH, PORTSMOUTH COUNTY, VIRGINIA

TABLES

BTEX: benzene, toluene, ethylbenzene, and xylenes
DRO: diesel range organics
GRO: gasoline range organics
NA: not available
PAHs: polycylic aromatic hydrocarbons
SVOCs: semivolatile organic compounds
TRPH: total petroleum hydrocarbons
VOCs: volatile organic compounds

* Data used in this table came from a database provided by RETEC on 8/29/2002 of the results of analysis of samples taken from 8/2001 to 7/2002. Results indicating no detected chemicals were not used in the statistics. Values in parentheses denote average concentrations for locations in the Patio Plaza area. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in micrograms per cubic meter.
CEMEG: chronic environmental media evaluation guide
CREG: cancer risk evaluation guide for 1×10^-6 excess cancer risk
CRMEG: chronic reference dose media evaluation guide
EMEG: environmental media evaluation guide
MRL: minimal risk level
N: no, not detected. Associated values are detection limits or surrogate spikes.
NA: not available
RBC: risk based concentration
REL-TWA: recommended exposure level – time-weighted average
RfC: reference concentration
SSL: soil screen level
TLV-TWA: threshold limit value – time-weighted average
Y: yes, detected

* Data used in this table came from a database provided by RETEC on 10/24/2002 of the results of analysis of samples taken from 08/2001 to 07/2002. Results indicating no detected chemicals were not used in the statistics. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in micrograms per liter (µg/L).

AL: action level
CEMEG: chronic environmental media evaluation guide
CREG: cancer risk evaluation guide for 1×10^-6 excess cancer risk
CRMEG: chronic reference dose media evaluation guide
MCL: maximum contaminant level
N: no, not detected. Associated values are detection limits or surrogate spikes.
NA: not available
RBC: risk-based concentration
TRPH: total petroleum hydrocarbons
Y: yes, detected

* Data used in this table came from a database provided by RETEC on 10/24/2002 of the results of analysis of samples taken from 08/2001 to 07/2002. Results indicating no detected chemicals were not used in the statistics. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in milligrams per kilogram (mg/kg).

N: no, not detected. Associated values are detection limits or surrogate spikes.
NA: not available
J: analyte present. Reported value was estimated.
Y: yes, detected

* Data used in this table came from a database provided by RETEC on 10/24/2002 of the results of analysis of samples taken from 08/2001 to 07/2002. Results indicating no detected chemicals were not used in the statistics. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in milligrams per kilogram (mg/kg).
N: no, not detected. Associated values are detection limits or surrogate spikes.
NA: not available
J: analyte present. Reported value was estimated.
Y: yes, detected

* Data used in this table came from a database provided by RETEC on 10/24/2002 of the results of analysis of samples taken from 08/2001 to 07/2002. Results indicating no detected chemicals were not used in the statistics. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in milligrams per kilogram (mg/kg).

CEMEG: chronic environmental media evaluation guide
CREG: cancer risk evaluation guide for 1×10^-6 excess cancer risk
EMEG: environmental media evaluation guide
IEMEG: intermediate environmental media evaluation guide
N: no, not detected. Associated values are detection limits or surrogate spikes.
NA: not available
ND: not detected
NT: not tested
RBC: risk-based concentration
RMEG: reference dose media evaluation guide
SSL: soil screen level
TRPH: total petroleum hydrocarbons
Y: yes, detected

* Data used in this table came from a database provided by RETEC on 10/24/2002 of the results of analysis of samples taken from 08/2001 to 07/2002. Results indicating no detected chemicals were not used in the statistics. Bold text denotes chemicals with average concentrations exceeding their respective comparison values. All concentrations are in milligrams per kilogram (mg/kg).

CREG: cancer risk evaluation guide for 1×10^-6 excess cancer risk
NA: not available
ND: not detected
RBC: risk-based concentration
RMEG: reference dose media evaluation guide
SSL: soil screen level

APPENDIX A: ATSDR COMPARISON VALUES AND DEFINITIONS

ATSDR comparison values (CVs) are media-specific concentrations considered safe under default exposure scenario. They are used as screening values for the identification of contaminants (site-specific substances) that require further evaluation to determine the potential for adverse health effects.

Generally, a chemical is selected for further evaluation because its maximum concentration in air, water, or soil at the site exceeds one of ATSDR's comparison values. However, it cannot be emphasized strongly enough that comparison values are not thresholds of toxicity. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. Indeed, the whole purpose behind highly conservative, health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health problems before they become actual health hazards. The probability that adverse health outcomes will actually occur as a result of exposure to environmental contaminants depends on site-specific conditions and individual lifestyle and genetic factors that affect the route, magnitude, and duration of actual exposure, and not on environmental concentrations alone.

Screening values based on noncancer effects are obtained by dividing NOAELs( no-observed-adverse-effect levels) or LOAELs (lowest-observed-adverse-effect levels) determined in animal or (less often) human studies by cumulative safety margins (variously called safety factors, uncertainty factors, and modifying factors) that typically range from 10 to 1,000 or more. By contrast, cancer-based screening values are usually derived by linear extrapolation from animal data obtained at high doses, because human cancer incidence data for very low levels of exposure simply do not exist, and probably never will.

Listed and described below are the comparison values that ATSDR has used to select chemicals for further evaluation for this health consultation, along with the abbreviations for the most common units of measure.

EMEG	environmental media evaluation guide
RMEG	reference dose media evaluation guide
MRL	minimal risk level
MCL	maximum contaminant level
ppm	parts per million, for example, mg/L or mg/kg
ppb	parts per billion, for example, µg/L or µg/kg
kg	kilogram (1,000 grams)
mg	milligram (0.001 grams)
µg	microgram (0.000001 grams)
L	liter
m3	cubic meter ( used in reference to a volume of air equal to 1,000 liters)

Acute exposure is defined as exposure to a chemical for a duration of 14 days or less.

Cancer risk evaluation guides (CREGs) are estimated contaminant concentrations in water, soil, or air that would be expected to cause no more than one excess cancer in a million persons exposed over a lifetime. CREGs are calculated from EPA's cancer slope factors.

Chronic exposure is defined as exposure to a chemical for 365 days or more.

Environmental media evaluation guides (EMEGs) are concentrations of a contaminant in water, soil, or air that are unlikely to be associated with any appreciable risk of deleterious non-cancer effects over a specified duration of exposure. EMEGs are derived from ATSDR minimal risk levels by factoring in default body weights and ingestion rates. Separate EMEGs are computed for acute (<14 days), intermediate (15–364 days), and chronic (>365 days) exposures.

Intermediate exposure is defined as exposure to a chemical for a duration of 15-364 days.

Lowest-observed-adverse-effect levels are the lowest exposure level of a chemical in a study, or group of studies, that produces statistically or biologically significant increase in frequency or severity of adverse health effects between the exposed population and its appropriate control.

Maximum contaminant levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day.

Minimal risk levels (MRLs) are estimates of daily human exposure to a hazardous substance that is likely to be without an appreciable risk of adverse noncancer health effects over a specified route and duration of exposure.

National Primary Drinking Water Regulations (NPDWR or primary standards) are legally-enforceable standards that apply to public water systems. Primary standards protect drinking water quality by limiting the levels of specific contaminants that can adversely affect public health and known or anticipated to occur in water. They take the form of MCLs or Treatment Techniques.

National Secondary Drinking Water Regulations (NSDWR or secondary standards) are nonenforceable guidelines regarding contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water.

No-observed-adverse-effect level is the dose of a chemical at which there were no statistically or biologically significant increases in frequency or severity of adverse health effects seen between the exposed population and its appropriate control. Effects may be produced at this dose, but they are not considered to be adverse.

Uncertainty factor (UF) is a factor used in operationally deriving the MRL or reference dose or reference concentration from exposure data.

The following comparison values were used for this health consultation: Environmental media evaluation guidelines (EMEGs); reference dose media evaluation guides (RMEGs); cancer risk evaluation guides (CREGS); minimal risk levels (MRLS); and U.S. Environmental Protection Agency Region 3 Risk-Based Concentrations (RBCs).

APPENDIX B: DOSE CALCULATIONS

Air pathway for indoor and outdoor samples, November 2000 and January 2001

The following formula was used to estimate inhalation exposure doses for benzene and methylene chloride:

ID = (C x IR x EF)/BW

Where,
ID = inhalation exposure dose (mg/kg/day)
C = contaminant concentration (mg/ m³)
IR = inhalation rate (20 m³/day for adults)
EF = exposure factor (unitless, conservatively assumed to be 1.0)
BW = body weight (70 kg for adults)

Benzene and methylene chloride were detected at average levels of 0.89 and 10.97 µg/ m³, respectively. Therefore,

ID for benzene = (0.00089 mg/ m³x20 m³ /day x 1)/70 kg = 0.00025 mg/kg/day
ID for methylene chloride = (0.01097 mg/ m³ x 20 m³ /day x 1)/70 kg = 0.003 mg/kg/day

ATSDR established acute and intermediate EMEG/MRLs for benzene as 160 and 13 µg/ m³, respectively [4]. The ATSDR acute EMEG/MRL for methylene chloride is 2,084µg/ m³, and the intermediate and chronic EMEG/MRL is 1042 µg/m³. The levels of benzene and methyl chloride in the Patio Plaza and Gates apartments were not present at levels likely to cause adverse health effects (noncarcinogenic) during short-term, intermediate term, and long-term exposures.

To evaluate the cancer risk, ATSDR used the EPA region 3 cancer slope factors (CSF) for inhalation exposures. CSFs are based on conservative assumptions such as fixed level of risk (i.e., a 1-in-1 million cancer risk) and a life time exposure (i.e., 365 days per year for 70 years). Together, with the very conservative assumptions used for the above dose calculation, ATSDR overestimates rather than underestimate risk by factors ranging from 10 to 1000.

Cancer risk is calculated as follows:

Cancer risk = average daily intake x CSF x exposure factor (conservatively assumed to be 1.0)

Cancer risk evaluation results are presented in the following table.

Dose: average inhalation dose in mg/kg/day
CSF: EPA region 3 cancer slope factors in mg/ kg/day^-1
CV: comparison values
CREG: cancer risk evaluation guide (ATSDR)

Based on the average levels of benzene and methylene chloride detected, residents who have a continuous lifetime exposure to those two chemicals via inhalation have no increased risk of developing cancer.

Cancer Risk Evaluations for Air sampling data during the site investigation

Concentrations of five VOCs (1,3-butadiane, benzene, chloroform, methylene chloride, and tetrahydrofuran) exceeded their respective CREGs. The same formula was used to estimate inhalation exposure dose for these chemicals (average concentrations for Patio Plaza area locations were used):

ID for 1,3-butadiene = (0.011 mg/m³ x 20 m³ /day x 1)/70 kg = 0.003 mg/kg/day
ID for benzene = (0.0055 mg/m³ x20m³ /day x 1)/70 kg = 0.0016 mg/kg/day
ID for chloroform = (0.0059 mg/m³ x 20m³ /day x 1)/70 kg = 0.0017 mg/kg/day
ID for methylene chloride = (0.5 mg/m³ x 20m³ /day x 1)/70 kg = 0.14 mg/kg/day
ID for tetrahydrofuran = (0.27 mg/m³ x 20m³ /day x 1)/70 kg = 0.077 mg/kg/day

Cancer risk evaluation results are presented in the following table.

Dose: average inhalation dose in mg/kg/day
CSF: EPA region 3 cancer slope factors in mg/ kg/day^-1
CV: comparison values
CREG: cancer risk evaluation guide (ATSDR)
RBC: EPA Region 3 risk based concentration

Dermal absorption pathway for benzene exposure

The following assumptions were made to estimate the dermal exposure dose for benzene:

(1) A resident would spend 2 hours per event, 40 events per year, for outdoor gardening (approximately 0.22 hour per day),
(2) Flow rate for irrigation is 8 liters per minute (L/min), and
(3) Average exposed body surface area is 3,300 square centimeter (cm²)

The following mathematical formula was used to estimate daily dermal absorption intake:

DDw = C x P x SA x ET

Where:

DDw = dermal absorption intake from dermal contact with water during gardening activities (mg)
C = benzene concentration in irrigation water in mg/L. The concentration in irrigation water is conservatively assumed as the fraction remaining after 50% of the benzene has volatilized (i.e., 50% of the drinking water concentration.)
P = permeability constant (conservatively assumed to be 0.001 liter /cm² per hour)
SA = exposed body surface area (cm²)
ET = exposure time (hour)

If the concentration of benzene in the drinking water is 0.235 mg/L, the estimated exposure during gardening is as follows:

dermal intake
= (0.235 mg/L) x 50% x (0.001 liter /cm² x hr) x (3,300 cm²) x (0.22 hr)
= 0.0085 mg

A 70 kg-adult from water contact during gardening activities dermal intake of 0.0085 mg benzene would be exposed to 0.12 µg/kg/day. A 10 kg-child from water contact during gardening activities dermal intake of 0.0085 mg benzene would receive a 0.85 µg/kg/day dose (This is an overestimate for children because the average exposed body surface area for children is much less than that used for adults in this dose calculation).

There are very limited data on the dermal exposure health effects for benzene. On the based of the mechanisms of toxicity, ATSDR assumes that dermal absorption is more toxicologically equivalent to inhalation than ingestion. Therefore, inhalation MRLs are used as respective CVs for the following noncancer effects evaluation. For noncancer effects, the ATSDR acute and intermediate MRLs for benzene are 0.05 and 0.004 ppm respectively. An estimated air concentration was calculated by using dermal intake:

Estimated air concentration = dermal intake / hourly inhalation rate x exposure duration = 0.00055 mg/m³ = 0.00017 ppm

The estimated concentration for residents in the location is much less than the MRLs. Therefore, no adverse health effects (noncarcinogenic) would result from infrequent dermal contact during gardening.

Soil ingestion pathway for mercury exposures

The following mathematical formula was used to estimate the soil ingestion exposure dose of mercury:

IDs = C x IR x EF x10^-6/BW

where:
IDs = soil ingestion exposure dose (mg/kg/day)
C = contaminant concentration in soil (mg/kg)
IR = soil ingestion rate (100 mg/day for adults)
EF = exposure factor (unitless-conservatively assumed to be 1.0)
BW= body weight (70 kg)

A 70 kg-adult ingesting 100 mg of soil per day containing 360 mg/kg (maximum concentration) or 42.8mg/kg (average concentration) of mercury would be exposed to 0.005 mg/kg/day or 0.00006 mg/kg/day. A 10-kg child ingesting 200 mg of soil containing 360 mg/kg (maximum concentration) or 42.8 mg/kg (average concentration) of mercury would receive doses of 0.076 mg/kg/day or 0.00856 mg/kg/day.

For noncancer effects, the ATSDR acute and intermediate oral MRLs for inorganic mercury are 0.007 and 0.002 mg/kg/day respectively. These MRLs are based on no-observed-adverse-effect levels (NOAELs) for renal effects in rats, with an uncertainty (safety) factor of 100 for extrapolation from animals to humans and human variability. The estimated mercury dose for children ingesting mercury-contaminated soil exceeds the acute and intermediate MRLs. Organic and inorganic mercury is not known to be carcinogenic by the oral ingestion route [7].

Cancer risk evaluations for surface soil sampling data before removal at Patio plaza apartments

IDs for arsenic = C x IR x EF x10^-6/BW = 13.61 x 100 x 10^-6/70 = 0.000019 mg/kg/day
IDs for benzo(a)pryene = 5.69 x 100 x 10^-6/70 = 0.0000081 mg/kg/day
IDs for benzo(b) fluoranthene = 4.08x100 x10^-6/70=0.0000058 mg/kg/day
IDs for benzo(a)anthracene = 6.56 x 100 x 10^-6/70 = 0.0000093 mg/kg/day
IDs for indeno (1,2,3_CD)pyrene = 1.23 x 100 x 10^-6/70 = 0.0000093 mg/kg/day

Ave.: average concentrations in mg/kg
Dose: soil ingestion exposure dose (mg/kg/day)
CSF: EPA region 3 cancer slope factors in mg/ kg/day^-1
CV: comparison values
CREG: cancer risk evaluation guide (ATSDR)

Cancer risk evaluations for surface soil sampling data after soil removal at the Patio plaza apartments

IDs for arsenic = C x IR x EF x 10^-6/BW = 8.59 x 100 x 10^-6/70 = 0.000012 mg/kg/day
IDs for benzo (a) pryene = 11.61 x 100 x 10^-6/70 = 0.0000081 mg/kg/day
IDs for benzo(b) fluoranthene = 10.13 x 100 x 10^-6/70 = 0.000014 mg/kg/day
IDs for benzo(a) anthracene = 9.16x100 x 10^-6/70 = 0.000013 mg/kg/day
IDs for indeno (1,2,3-cd) pyrene = 7.44x100 x10^-6/70=0.0000093 mg/kg/day

APPENDIX C: ATSDR LEVELS OF PUBLIC HEALTH HAZARD

CATEGORY A: URGENT PUBLIC HEALTH HAZARD

This category is used for sites where short-term exposures (< 1 yr) to hazardous substances or conditions could result in adverse health effects that require rapid intervention.

This determination represents a professional judgment based on critical data which ATSDR has judged sufficient to support a decision. This does not necessarily imply that the available data are complete; in some cases additional data may be required to confirm or further support the decision made.

Criteria

Evaluation of available relevant information* indicates that site-specific conditions or likely exposures have had, are having, or are likely to have in the future, an adverse impact on human health that requires immediate action or intervention. Such site-specific conditions or exposures may include the presence of serious physical or safety hazards, such as open mine shafts, poorly stored or maintained flammable/explosive substances, or medical devices which, upon rupture, could release radioactive materials.

CATEGORY B: PUBLIC HEALTH HAZARD

This category is used for sites that pose a public health hazard due to the existence of long-term exposures (> 1 yr) to hazardous substances or conditions that could result in adverse health effects.

This determination represents a professional judgment based on critical data which ATSDR has judged sufficient to support a decision. This does not necessarily imply that the available data are complete; in some cases additional data may be required to confirm or further support the decision made.

Criteria

Evaluation of available relevant information* suggests that, under site-specific conditions of exposure, long-term exposures to site-specific contaminants (including radionuclides) have had, are having, or are likely to have in the future, an adverse impact on human health that requires one or more public health interventions. Such site-specific exposures may include the presence of serious physical hazards, such as open mine shafts, poorly stored or maintained flammable/explosive substances, or medical devices which, upon rupture, could release radioactive materials.

CATEGORY C: INDETERMINATE PUBLIC HEALTH HAZARD

This category is used for sites when a professional judgment on the level of health hazard cannot be made because information critical to such a decision is lacking.

Criteria

This category is used for sites in which "critical" data are insufficient with regard to extent of exposure and/or toxicologic properties at estimated exposure levels. The health assessor must determine, using professional judgment, the importance of such data and the likelihood that the data can be obtained and will be obtained in a timely manner. Where some data are available, even limited data, the health assessor is encouraged to the extent possible to select other hazard categories and to support decisions with a clear narrative that explains the limits of the data and the rationale for the decision.

CATEGORY D: NO APPARENT PUBLIC HEALTH HAZARD

This category is used for sites where human exposure to contaminated media may be occurring, may have occurred in the past, and/or may occur in the future, but the exposure is not expected to cause any adverse health effects.

This determination represents a professional judgment based on critical data which ATSDR considers sufficient to support a decision. This does not necessarily imply that the available data are complete, in some cases additional data may be required to confirm or further support the decision made.

Criteria

Evaluation of available relevant information* indicates that, under site-specific conditions of exposure, exposures to site-specific contaminants in the past, present, or future are not likely to result in any adverse impact on human health.

CATEGORY E: NO PUBLIC HEALTH HAZARD

This category is used for sites that, because of the absence of exposure, do NOT pose a public health hazard.

Criteria

Sufficient evidence indicates that no human exposures to contaminated media have occurred, none are now occurring, and none are likely to occur in the future.
* Such as environmental and demographic data; health outcome data; community health concerns information; toxicological, medical, and epidemiologic data.

FIGURES

Figure 1. Portsmouth Manufactured Gas Plant Vicinity Map

Figure 2. Arsenic Concentrations in Soils and Other Surficial Materials of the Conterminous United States

Figure 3. Lead Concentrations in Soil and Other Surficial Materials of the Conterminous United States

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