HEALTH CONSULTATION
Active Soil Gas Data Review
CHILLUM PERC SITE
(a/k/a CHILLUM PERCHLOROETHYLENE)
CHILLUM, PRINCE GEORGES COUNTY, MARYLAND
Table 7. Summary of MTBE active soil vapor data, Chillum perc site, Chillum, Maryland
Sample ID | Laboratory | MTBE Value (µg/m3) | Lab Qualifier | Date |
001 | QES | 275.5 | J | 5/9/2002 |
002 | QES | 3787.6 | J | 5/9/2002 |
003 | QES | 2.4 | NJ | 4/12/2002 |
004 | QES | 4/12/2002 | ||
005 | QES | 173.7 | J | 5/9/2002 |
006 | QES | 84.8 | J | 5/9/2002 |
007 | QES | 219.9 | NJ | 5/8/2002 |
008 | QES | 98.1 | NJ | 5/8/2002 |
010 | QES | 2.1 | NJ | 4/12/2002 |
012 | QES | 101.7 | NJ | 5/8/2002 |
013 | QES | 234.9 | NJ | 5/8/2002 |
014 | QES | 224.3 | NJ | 5/8/2002 |
015 | QES | 275 | NJ | 5/8/2002 |
016 | QES | 4/12/2002 | ||
017 | QES | 4/12/2002 | ||
018 | QES | 297 | NJ | 5/8/2002 |
019 | QES | 5/3/2002 | ||
020 | QES | 44.5 | NJ | 4/11/2002 |
021 | QES | 4/11/2002 | ||
022 | QES | 3.3 | NJ | 4/11/2002 |
023 | QES | 184.9 | NJ | 4/11/2002 |
024 | QES | 4/11/2002 | ||
025 | QES | 144.4 | NJ | 4/11/2002 |
026 | QES | 93 | NJ | 4/11/2002 |
027 | QES | 4/11/2002 | ||
030 | QES | 3.8 | 1/31/2002 | |
031 | QES | 2.2 | NJ | 4/12/2002 |
032 | QES | 4/12/2002 | ||
033 | QES | 4/12/2002 | ||
034 | QES | 60.1 | NJ | 4/10/2002 |
035 | QES | 127.2 | NJ | 4/10/2002 |
036 | QES | 5/3/2002 | ||
037 | QES | 5/3/2002 | ||
038 | QES | 4/10/2002 | ||
039 | QES | 66.9 | NJ | 4/10/2002 |
040 | QES | 44.2 | NJ | 4/10/2002 |
041 | QES | 4/10/2002 | ||
043 | QES | 310.3 | NJ | 4/10/2002 |
044 | QES | 12.4 | 1/31/2002 | |
046 | QES | 7.8 | 2/8/2002 | |
047 | QES | 9 | 2/8/2002 | |
048 | QES | 5/3/2002 | ||
049 | QES | 5/3/2002 | ||
050 | QES | 10.2 | 2/7/2002 | |
052 | QES | 13.7 | 2/6/2002 | |
054 | QES | 7.6 | 2/7/2002 | |
057 | QES | 8.6 | 1/30/2002 | |
059 | QES | 23.2 | 1/28/2002 | |
061 | QES | 29.8 | 1/31/2002 | |
063 | QES | 421.7 | NJ | 5/8/2002 |
064 | QES | 198.3 | NJ | 5/8/2002 |
067 | QES | 10.6 | 1/29/2002 | |
072 | QES | 37.3 | 1/28/2002 | |
073 | QES | 3.1 | 1/29/2002 | |
078 | QES | 35.8 | 1/28/2002 | |
074 | QES | 23 | 1/28/2002 | |
081 | QES | 6.66 | NJ | 2/11/2002 |
083 | QES | 5.18 | NJ | 2/11/2002 |
084 | QES | 3.33 | NJ | 2/11/2002 |
085 | QES | 45.2 | 2/6/2002 | |
086 | QES | 11.9 | 2/6/2002 | |
001 | GF-CHEVRON | U | 5/9/2002 | |
002 | GF-CHEVRON | 110 | 5/9/2002 | |
003 | GF-CHEVRON | U | 4/12/2002 | |
004 | GF-CHEVRON | U | 4/12/2002 | |
005 | GF-CHEVRON | U | 5/9/2002 | |
006 | GF-CHEVRON | U | 5/9/2002 | |
007 | GF-CHEVRON | U | 5/8/2002 | |
008 | GF-CHEVRON | U | 5/8/2002 | |
010 | GF-CHEVRON | U | 4/12/2002 | |
012 | GF-CHEVRON | U | 5/8/2002 | |
013 | GF-CHEVRON | 38 | 5/8/2002 | |
014 | GF-CHEVRON | 52 | 5/8/2002 | |
015 | GF-CHEVRON | 52 | 5/8/2002 | |
016 | GF-CHEVRON | U | 4/12/2002 | |
017 | GF-CHEVRON | U | 4/12/2002 | |
018 | GF-CHEVRON | U | 5/8/2002 | |
019 | GF-CHEVRON | U | 5/3/2002 | |
020 | GF-CHEVRON | U | 4/11/2002 | |
021 | GF-CHEVRON | U | 4/11/2002 | |
022 | GF-CHEVRON | U | 4/11/2002 | |
023 | GF-CHEVRON | U | 4/11/2002 | |
024 | GF-CHEVRON | U | 4/11/2002 | |
025 | GF-CHEVRON | U | 4/11/2002 | |
026 | GF-CHEVRON | U | 4/11/2002 | |
027 | GF-CHEVRON | 29 | 4/11/2002 | |
028 | GF-CHEVRON | U | 1/31/2002 | |
031 | GF-CHEVRON | U | 4/12/2002 | |
033 | GF-CHEVRON | U | 4/12/2002 | |
034 | GF-CHEVRON | U | 4/10/2002 | |
035 | GF-CHEVRON | U | 4/10/2002 | |
036 | GF-CHEVRON | U | 5/3/2002 | |
037 | GF-CHEVRON | 37 | 5/3/2002 | |
038 | GF-CHEVRON | U | 4/10/2002 | |
039 | GF-CHEVRON | U | 4/10/2002 | |
040 | GF-CHEVRON | U | 4/10/2002 | |
042 | GF-CHEVRON | U | 4/10/2002 | |
043 | GF-CHEVRON | U | 4/10/2002 | |
044 | GF-CHEVRON | U | 1/31/2002 | |
046 | GF-CHEVRON | U | 2/8/2002 | |
047 | GF-CHEVRON | U | 2/8/2002 | |
048 | GF-CHEVRON | 11 | 5/3/2002 | |
049 | GF-CHEVRON | U | 5/3/2002 | |
050 | GF-CHEVRON | U | 2/7/2002 | |
052 | GF-CHEVRON | U | 2/6/2002 | |
054 | GF-CHEVRON | U | 2/7/2002 | |
057 | GF-CHEVRON | 39 | 1/30/2002 | |
056 | GF-CHEVRON | 26 | 1/30/2002 | |
059 | GF-CHEVRON | U | 1/28/2002 | |
061 | GF-CHEVRON | U | 1/31/2002 | |
063 | GF-CHEVRON | 53 | 5/8/2002 | |
064 | GF-CHEVRON | U | 5/8/2002 | |
067 | GF-CHEVRON | 42 | 1/29/2002 | |
068 | GF-CHEVRON | U | 1/28/2002 | |
071 | GF-CHEVRON | 67 | 1/29/2002 | |
078 | GF-CHEVRON | 37 | 1/28/2002 | |
074 | GF-CHEVRON | 33 | 1/28/2002 | |
081 | GF-CHEVRON | U | 2/11/2002 | |
082 | GF-CHEVRON | U | 2/11/2002 | |
084 | GF-CHEVRON | U | 2/11/2002 | |
085 | GF-CHEVRON | U | 2/6/2002 | |
086 | GF-CHEVRON | U | 2/6/2002 | |
101 | USACE | 32 | ||
106 | USACE | 29 | ||
112 | USACE | 18 | ||
115 | USACE | 14 | ||
118 | USACE | 33 | ||
126 | USACE | 558 | ||
133 | USACE | 2.4 | ||
140 | USACE | 27 | ||
141 | USACE | 17 | ||
144 | USACE | 1210 | ||
151 | USACE | 149 | ||
011 | QES | 3.7 | NJ | 4/12/2002 |
029 | QES | 8.1 | 1/31/2002 | |
045 | QES | 47.1 | 1/31/2002 | |
051 | QES | 21.9 | 2/7/2002 | |
053 | QES | 7.2 | 2/6/2002 | |
058 | QES | 241.7 | 1/30/2002 | |
055 | QES | 21 | 1/30/2002 | |
060 | QES | 18.4 | 1/28/2002 | |
062 | QES | 16.3 | 1/31/2002 | |
065 | QES | 78.8 | 1/29/2002 | |
066 | QES | 10 | 1/29/2002 | |
069 | QES | 41.4 | 1/28/2002 | |
070 | QES | 69.7 | 1/29/2002 | |
079 | QES | 58.7 | 1/28/2002 | |
075 | QES | 31.5 | 1/28/2002 | |
087 | QES | 6.8 | 2/6/2002 | |
153 | EPA REMOVAL | |||
154 | EPA REMOVAL | |||
011 | GF-CHEVRON | U | 4/12/2002 | |
029 | GF-CHEVRON | U | 1/31/2002 | |
045 | GF-CHEVRON | U | 1/31/2002 | |
051 | GF-CHEVRON | U | 2/7/2002 | |
053 | GF-CHEVRON | U | 2/6/2002 | |
058 | GF-CHEVRON | 46 | 1/30/2002 | |
060 | GF-CHEVRON | U | 1/28/2002 | |
062 | GF-CHEVRON | 11 | NJ | 1/31/2002 |
065 | GF-CHEVRON | 67 | 1/29/2002 | |
066 | GF-CHEVRON | 35 | 1/29/2002 | |
069 | GF-CHEVRON | 57 | 1/28/2002 | |
070 | GF-CHEVRON | 70 | 1/29/2002 | |
079 | GF-CHEVRON | 36 | 1/28/2002 | |
075 | GF-CHEVRON | 31 | 1/28/2002 | |
088 | GF-CHEVRON | U | 2/6/2002 | |
091 | USACE | 19 | ||
096 | USACE | 13 | ||
100 | USACE | 30 | ||
111 | USACE | 15 | ||
119 | USACE | 16 | ||
127 | USACE | 39.6 | ||
131 | USACE | 1.5 | ||
130 | USACE | 1.5 | ||
145 | USACE | 26 | ||
152 | USACE | 71.6 |
Notes:
QES: Quality Environmental Solutions
USACE: U.S. Army Corp of Engineers
GF-Chevron: Gannett Fleming, Inc. (contractor of Chevron)
J: Compound was detected; quantification is approximate because of limitations
identified during the quality control review.
NJ: Compound was analyzed for, but not detected; quantification is approximate
because of limitations identified during the quality control review.
U: Compound was analyzed for, but not detected.
Blank cell: not detected
Table 8. Summary of indoor air data, Chillum
perc site, Chillum, Maryland (µg/m3)
Chemical | Concentration | Comparison Value |
acetone | 2 | 31,000 (CEMEG) |
benzene | 1 | 32 (DHAC Guideline) |
hexane | 3 | 200 (RMEG) |
2-propanol | 2, 130 | 491,534 (TLV-TWA for n-propanol) |
propene | 1 | 344,213 (TLV-TWA) |
toluene | 1 | 3,830 (CEMEG) |
Notes:
CEMEG: Chronic Environmental Media Evaluation Guide
DHAC: Division of Health Assessment and Consultation
RMEG: Reference Dose Media Evaluation Guide
TLV-TWA: Threshold Limit Value for a Time-Weighted Average
APPENDIX A: ATSDR'S COMPARISON VALUES AND DEFINITIONS
ATSDR comparison values (CVs) are media-specific concentrations considered safe under default exposure scenario. ATSDR uses them as screening values to identify contaminants (site-specific substances) that require further evaluation to determine the potential for adverse health effects.
Generally, a chemical at a site requires further evaluation when its maximum concentration in air, water, or soil exceeds one of ATSDR's comparison values. Comparison values are not, however, 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 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 individual lifestyle and genetic factors and site-specific conditions that affect the route, magnitude, and duration of actual exposure-not on environmental concentrations alone.
ATSDR derives screening values based on non-cancer effects by dividing NOAELs (no-observed-adverse-effect levels) or LOAELs (lowest-observed-adverse-effect levels). These levels stem from animal or human studies and include 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 come from 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 below are the comparison values that ATSDR uses to select chemicals for further evaluation, along with the abbreviations for the most common units of measure.
EMEG = Environmental Media Evaluation Guides RMEG = Reference Dose Media Evaluation Guide MRLs = Minimal Risk Levels ppm = Parts Per Million, e.g., mg/L or mg/kg ppb = Parts Per Billion, e.g., µg/L or µg/kg kg = Kilogram (1,000 grams) mg = Milligram (0.001 grams) µg = Microgram (0.000001 grams) µg/m3 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.
American Conference of Governmental Industrial Hygienists (ACGIH): A professional organization that establishes and publishes standards for occupational settings for five, 8-hour days per week.
ACGIH Threshold Limit Value for a Time Weighted Average (TLV-TWA): Airborne concentrations of substances and represents conditions, under which nearly all workers may be repeatedly exposed for a normal 8-hour workday and a 40-hour work week, week after week, without adverse effect.
Cancer Risk Evaluation Guides (CREG): 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: Exposure to a chemical for 365 days or more.
Environmental Media Evaluation Guides (EMEGs): Concentrations of a contaminant in water, soil, or air unlikely to produce any appreciable risk of adverse, 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. ATSDR computes separate EMEGs for acute (<14 days), intermediate (15364 days), and chronic (>365 days) exposures.
Intermediate Exposure: Exposure to a chemical for a duration of 15-364 days.
Lowest Observed Adverse Effect Level (LOAELs): The lowest exposure level of a chemical in a study, or group of studies, that produces statistically or biologically significant increase(s) in frequency or severity of adverse health effects between the exposed and control populations.
Maximum Contaminant Level (MCL): 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 two liters of water per day.
Minimal Risk Levels (MRL): Estimate 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.
No Observed Adverse Effect Level (NOAEL): 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): A factor used in deriving the MRL or reference dose or reference concentration from exposure data.
The following comparison values were used for this health consultation:
APPENDIX B: GLOSSARY OF TERMS FOR VAPOR INTRUSION
Soil vapor: Air within the pore spaces of soil.
Active Soil Vapor Sampling: The withdrawal of the soil vapor from the subsurface and subsequent analysis of the vapor over a short time period (a few minutes) by pumping air from a void created at designed depth.
Advection: The process by which soil gas moves according to differences in pressure, temperature, or other factors.
Diffusion: The process whereby soil gas moves from an area of higher concentration to an area of lower concentration.
Fick's Law: This law states that diffusive transport of VOCs is governed by a concentration gradient and an effective coefficient of diffusity.
Passive Soil Vapor Sampling: The process of the burial of an adsorbent in the ground with subsequent retrieval and measurement of the adsorbent.
Preferential Pathways: Naturally occurring and/or anthropogenic subsurface pathways expected to have a high intrinsic gas permeability (vadose zone) or high conductivity (saturated zone) and thus influence the flow or migration of contaminated vapor or groundwater. (EPA VI guide)
Barometric Influences: Fluctuations in barometric pressure that can affect the steady state soil vapor profile (particularly in the shallow vadose zone); such fluctuations can influence measurements taken to characterize indoor air risk.
Dual-phase Extraction (DPE): The system used to extract both soil gas and ground water from the same extraction well to remediate soil and ground water contaminated with VOCs.
Shallow Soil Vapor Samples: Samples with sampling depth <5 feet below the bottom of the basement slab.
Deep Soil Vapor Samples: Samples from depths >5 feet below the bottom of the basement slab.
Dual-Phase Vacuum Extraction (DVE) System: A high vacuum system to extract both soil gas and ground water from the same extraction well to remediate soil and ground water contaminated with VOCs.
Attenuation Factor: The ratio of the indoor air concentration of some chemical divided by the equilibrium soil gas concentration of that chemical immediately above the source.
Volatile Organic Compounds (VOCs): Organic compounds that evaporate readily into the air.
Volatility: The capacity of a liquid to form vapors. Volatility can be measured through a liquid's vapor pressure.
APPENDIX C: ATSDR'S LEVELS OF PUBLIC HEALTH HAZARD
CATEGORY A: URGENT PUBLIC HEALTH HAZARD
This category is used for sites where short-term exposures (<1 year) 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 that ATSDR has judged sufficient to support a decision. Such a designation does not necessarily mean 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 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, if ruptured, could release radioactive materials.
CATEGORY B: PUBLIC HEALTH HAZARD
This category is used for sites that pose a public health hazard because of 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 that ATSDR has judged sufficient to support a decision. Such a designation does not necessarily mean 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 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, if ruptured, could release radioactive materials.
CATEGORY C: INDETERMINATE PUBLIC HEALTH HAZARD
This category indicates that 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 for which available critical data are insufficient with regard to the extent of exposure and/or toxicological properties at estimated exposure levels. The health assessor must determine, using professional judgment, the "criticality" of such data and the likelihood that the data can and will be obtained in a timely manner. Where some dataeven limited dataare available, health assessors should to the extent possible select other hazard categories and support their decision 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 that ATSDR has judged sufficient to support a decision. Such a designation does not necessarily mean that the available data are complete; in some cases, additional data may be required to confirm or further support the decision made.
Criteria:
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 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 occurring, and none are likely to occur in the future.
* Examples include environmental, demographic, health outcome, exposure, toxicological, medical, or epidemiologic data, as well as community health concerns information.