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Home My WebLink About10047_Atherton Mills_ IAR Risk-based Goals 20150113 1075 Big Shanty Road NW Suite 100 Kennesaw, Georgia 30144 770-421-3400 amecfw.com January 20, 2015 Ms. Carolyn Minnich, Brownfields Project Manager North Carolina Department of Environment and Natural Resources Division of Waste Management Brownfields Program 1646 Mall Service Center Raleigh, North Carolina 27600-1646 Subject: Indoor Air Monitoring – Risk-based Goals Atherton Mill Property 2000 South Boulevard Charlotte, Mecklenburg County, North Carolina Brownfields Project Number: 10047-06-60 AMEC Project: 6228-12-0051 Dear Ms. Minnich: AMEC Foster Wheeler Environment & Infrastructure, Inc. (AMEC) evaluated the constituents detected in indoor air samples collected at the Atherton Mill Property, 2000 South Boulevard, Charlotte, North Carolina. Six indoor air samples were collected in April 2013, July 2013, and January 2014. One outdoor ambient air sample was collected during each of these three sampling events. Ten indoor air samples were collected in June 2014 and seven indoor air samples were collected in September 2014. During each of the June and September 2014 events, an upwind and downwind ambient air sample were also collected. As a first step, detected concentrations from the 2013 and 2014 indoor air sampling events were compared to the North Carolina Department of Environment and Natural Resources (NCDENR) Division of Waste Management (DWM) Non-Residential Vapor Intrusion Screening Levels published in June 2014 (NCDENR, 2014). Eleven volatile compounds were detected at maximum concentrations that exceeded the DWM non-residential indoor air screening levels. Exposure Assessment The Atherton Mill Property is a commercial development housed partly in the former Parks- Cramer Company manufacturing facility that was built in the 1919, and partly in a former Charlotte Trolley Car Barn. One historic feature of the site is wooden brick floors, which have been observed to off-gas naphthalene. Additional volatile compounds have been detected in air samples that may be associated with current retail and office activities, and other sources such as furnishings and building materials. To support air monitoring for the eleven volatile Indoor Air Monitoring – Risk-based Goals Atherton Mill AMEC Project: 6228-12-0051 Page 2 Page 2 of 4 constituents of potential concern (COPCs) that exceeded the DWM screening levels, target monitoring goals were developed to be protective of retail sales workers and office workers. The COPCs detected in the sampled tenant spaces differ with only one to three COPCs detected in the majority of the spaces sampled. The retail sales and office employment classifications are representative of current occupants at Atherton Mill. Office workers were assumed to be employed 8 hours per day for 250 days per year for 25 years (USEPA, 2014a). Retail sales workers were assumed to be employed 8 hours per day for 250 days per year for 4 years (USEPA, 2014a; Bureau of Labor Statistics, 2014). Toxicity Assessment Toxicity values [Inhalation Reference Concentrations (RfCs) and Inhalation Unit Risks (IURs)] used in this evaluation were obtained from the USEPA Integrated Risk Information System (IRIS) and other USEPA-approved sources as listed in the May 2014 Vapor Intrusion Screening Level calculator (USEPA, 2014b). The toxicity values used in this assessment are listed on Tables 1 and 2. The RfC is used to estimate non-carcinogenic inhalation hazards. The RfC is an estimate of the daily exposure to the human population (including sensitive subgroups such as children and the elderly) that is likely to be without an appreciable risk of deleterious effects. The IUR is characterized as an upper-bound estimate designed to be protective of the majority of the human population. Calculation of Risk-based Goals for Air Monitoring Risk-based air monitoring goals were calculated for office workers and retail sales workers using the equations presented in the Vapor Intrusion Screening Level calculator (USEPA, 2014b) and the exposure assumptions listed above for each employment group. For the purpose of calculating risk-based air monitoring goals, the target hazard index for non-carcinogens has been based on one because cumulative target organ-specific systemic or non-carcinogenic health risks are unlikely to exceed one. The target risk for carcinogens has been based on 10-5 for the indoor air pathways because cumulative risks would not exceed 10-4, an upper risk level that is considered to be in the acceptable range under CERCLA. These target hazard and risk goals are in agreement with current DWM guidance (NCDENR, 2014). Air monitoring goals protective of office workers potentially exposed to the COPCs are presented in Table 1. Air monitoring goals protective of retail sales workers potentially exposed to the COPCs are presented in Table 2. The values listed for chronic exposure to non-carcinogens are also protective of short-term exposures. USEPA has identified fetal cardiac defects in TCE-exposed animals as the basis for interim short-term action levels. The concerns focus on the presumption that the critical period for human fetal cardiac development occurs within a three-week period within the first trimester of pregnancy, although the specific timing and duration of TCE exposure associated with Indoor Air Monitoring – Risk-based Goals Atherton Mill AMEC Project: 6228-12-0051 Page 3 Page 3 of 4 potential developmental toxicity for humans is not known. A risk-based air monitoring level of 8.8 µg/m3 for TCE will be protective of both short-term and longer-term chronic exposure durations. AMEC appreciates this opportunity to provide our environmental consulting services. If you have questions concerning this letter or this project, please contact us at 770-499-6849. Sincerely, AMEC Environment & Infrastructure, Inc. Melissa Bystedt Laura M. Smith, RHSP Project Scientist Associate Scientist Enclosures: Table 1 Table 2 References Indoor Air Monitoring – Risk-based Goals Atherton Mill AMEC Project: 6228-12-0051 Page 4 Page 4 of 4 REFERENCES Bureau of Labor Statistics, 2014. Employee Tenure in 2014. News Release, September 18, 2014. NCDENR, 2014. Division of Waste Management (DWM) Vapor Intrusion Screening levels Guidance Document, North Carolina Department of Environment and Natural Resources, April 2014. Tables updated in June 2014. USEPA, 2014a. Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors, OSWER Directive 9200.1-120, February 2014. USEPA, 2014b. Vapor Intrusion Screening Level Calculator. U.S Environmental Protection Agency, May 2014. Parameter Inhalation InhalationRfC Unit Risk (IUR)(mg/m3) (µg/m3)-1 Benzene 3.0E-02 7.8E-06 IRIS 98 130Chloroform 9.8E-02 2.3E-05 ATSDR/IRIS 33 4301,4-Dichlorobenzene 8.0E-01 1.1E-05 IRIS/CalEPA 70 3,5001,2-Dichloroethane 7.0E-03 2.6E-05 PPRTV/IRIS 29 31Ethyl Acetate 7.0E-02 NA PPRTV NA 310Ethylbenzene 1.0E+00 2.5E-06 IRIS/CalEPA 310 4,400N-Hexane 7.0E-01 NA IRIS NA 3,100Naphthalene 3.0E-03 3.4E-05 IRIS/CalEPA 23 13Tetrachloroethene 4.0E-02 2.6E-07 IRIS 2900 180Trichloroethene 2.0E-03 4.1E-06 IRIS 190 8.81,2,4-Trimethylbenzene 7.0E-03 NA PPRTV NA 31m3 = cubic metersPrepared/Date: LMS 1/16/15mg = milligramChecked/Date: MKB 1/19/15RfC = Reference Concentrationµg = microgramsNA = Not AvailableCalEPA - California Environmental Protection AgencyIRIS - Integrated Risk Information SystemPPRTV - Provisional Peer-Reviewed Toxicity ValueATSDR - Agency for Toxic Substances and Disease Registry(a) Target Indoor Air Conc. (Carcinogens) = (TCR * ATc)/ (ET * EF * ED * IUR)(b) Target Indoor Air Conc. (Non-Carcinogens) = (RfC * THI * ATnc * 1000)/ (ET * EF * ED)CA = Constituent Concentration in Air (estimated) See above(µg/m3)ATnc = Averaging Time (Noncarcinogen, hours) 35,040ET = Exposure Time (hours per day) 8 (hours/day)ATc = Averaging Time (Carcinogenic, hours)613,200EF = Exposure Frequency (days per year) 250 (days/year) TCR = Target Cancer Risk1.00E-05ED = Exposure Duration (years)4 (years) THI = Target Hazard Index 1Note: Median tenure for retail workers ranges from 2.8 years to 3.3 years for January 2004 through January 2014 (Employee Tenure in 2014, Bureau for Labor Statistics, September 2014. . Exposure duration rounded upward to 4 years.Target Indoor Air Conc. for Carcinogens(ug/m3) (a)Target Indoor Air Conc for Non-Carcinogens(ug/m3) (b)Table 1: Calculation of Preliminary Risk Goals for Indoor Air Concentrations - Retail WorkerAtherton Mill PropertyCharlotte, North CarolinaAMEC Project: 6228-12-0051Toxicity ValuesSource Parameter Inhalation InhalationRfC Unit Risk(mg/m3) (µg/m3)-1 Benzene 3.0E-02 7.8E-06 IRIS 16 130Chloroform 9.8E-02 2.3E-05 ATSDR/IRIS 5.3 4301,4-Dichlorobenzene 8.0E-01 1.1E-05 IRIS/CalEPA 11 3,5001, 2-Dichloroethane 7.0E-03 2.6E-05 PPRTV/IRIS 4.7 31Ethyl Acetate 7.0E-02 NA PPRTV NA 310Ethylbenzene 1.0E+00 2.5E-06 IRIS/CalEPA 49 4,400N-Hexane 7.0E-01 NA IRIS NA 3,100Naphthalene 3.0E-03 3.4E-05 IRIS/CalEPA 3.6 13Tetrachloroethene 4.0E-02 2.6E-07 IRIS 470 180Trichloroethene 2.0E-03 4.1E-06 IRIS 30 8.81,2,4-Trimethylbenzene 7.0E-03 NA PPRTV NA 31m3 = cubic metersPrepared/Date: LMS 1/16/15mg = milligramChecked/Date: MKB 1/19/15RfC = Reference Concentrationµg = microgramsNA = Not AvailableCalEPA - California Environmental Protection AgencyIRIS - Integrated Risk Information SystemPPRTV - Provisional Peer-Reviewed Toxicity ValueATSDR - Agency for Toxic Substances and Disease Registry(a) Target Indoor Air Conc. (Carcinogens) = (TCR * ATc)/ (ET * EF * ED * IUR)(b) Target Indoor Air Conc. (Non-Carcinogens) = (RfC * THI * ATnc * 1000)/ (ET * EF * ED)CA = Constituent Concentration in Air (estimated) See above(µg/m3)ATnc = Averaging Time (Noncarcinogen, hours) 219,000ET = Exposure Time (hours per day) 8 (hours/day)ATc = Averaging Time (Carcinogenic, hours)613,200EF = Exposure Frequency (days per year) 250 (days/year) TCR = Target Cancer Risk1.00E-05ED = Exposure Duration (years)25 (years) THI = Target Hazard Index 1Toxicity ValuesSourceTarget Indoor Air Conc for CarcinogensTarget Indoor Air Conc for Non-CarcinogensTable 2: Calculation of Preliminary Risk Goals for Indoor Air Concentrations - Office WorkerAtherton Mill PropertyCharlotte, North CarolinaAMEC Project: 6228-12-0051