M14 - Oral
Inhalation ExposureScotland B 1:30-3:00 pm
|
| Chair(s): P. Williams
|
M14.1 Results of a Muliti-Phase Indoor Air Investigation of a Large Complex Building. Brenner D, Olliges S, Anderson T, Lee A; Neptune and Company, Inc.; NASA Ames; ISSI; U.S. EPA dbrenner@neptuneinc.org
Abstract: Building N-210 on the NASA Ames Research Center campus was originally constructed as an aircraft hanger in the late 1930’s. Since it’s construction numerous modifications and renovations have taken place, most recently in the late 1990’s. The building is located over the leading edge of a shallow regional VOC groundwater plume. Recent groundwater data (2003) indicates the TCE concentrations beneath the building are approximately 100ug/L.
As part of a larger NASA indoor air investigation SUMA canister samples were collected in June 2004 from two locations within the building. One of the locations had average TCE concentrations of approximately 100 ug/m3. Based upon these results, additional SUMA canister sampling was conducted in September and October 2004 to define the extent of the indoor air contamination. This additional sampling confirmed the original results and also indicates elevated TCE concentrations existed in other portions of the building.
The U.S. EPA mobile TAGA laboratory was employed in May 2005 to further investigate the extent of indoor concentrations and to assist in the identification of preferential vapor intrusion pathways. The TAGA results were used to plan additional sampling, both to confirm the TAGA results and discern if the observed results were due to SUMA canister samples located near preferential pathways or were a result of inadequate ventilation in some areas. Based upon the additional SUMA canister samples collected during July 2005, remedial measures were implemented and additional confirmation samples collected.
Data on all phases of the indoor air investigation, along with outdoor ambient and outdoor background sample data will be presented. In addition, the results will be discussed relative to the complexity of the building construction and the effectiveness of the implemented remedial measures on indoor air concentrations will be presented.
|
M14.2 Viscose: A Previously Unidentified Source of Residential Exposure to Elemental Mercury. MacIntosh DL, Chang MP, Myatt TA; EH&E dmacintosh@eheinc.com
Abstract: Elemental mercury is a component of many common products including electrical switches, batteries and thermometers that take advantage of its conductive and thermal properties. An investigation motivated by a mercury spill in a residence lead to the discovery of elemental mercury in another consumer product - viscose rugs. Bulk samples from 15 rugs obtained from retail outlets were assayed for mercury. The viscose rugs (n=9) contained mercury levels in the range of 18 to 150 micrograms per kg (mg/kg). In contrast, mercury was not detected in bulk samples from the olefin, wool, nylon, and polypropylene rugs that were assayed. Based on air sampling in flow-through stainless steel exposure chambers with six of the viscose rugs, the flux of elemental mercury to air was determined to be 15 to 50 nanograms (ng) per square meter per hour. An indoor air quality model run with a set of reasonable inputs for home ventilation characteristics and the maximum observed flux produced elemental mercury concentrations in indoor air of 7 to 110 ng/m3. These levels are below the reference concentration (RfC) for mercury vapor of 300 ng/m3 established by the U.S. Environmental Protection Agency (EPA), yet greater than typical concentrations reported for outdoor air (less than 10 ng/m3). Mercury in viscose rugs appears to result from the viscose production process where intermediates are steeped and washed with caustic soda, a reagent that can contain mercury levels of approximately 0.5 ppm when produced by conventional chlor-alkali plants. Although mercury in viscose rugs was found not to present an imminent health risk, collection of additional information on emissions and aggregate exposure to mercury from contemporaneous use of numerous viscose products appears to be warranted.
|
M14.3 Estimating Benzene Exposures from Contaminated Soils at MGP Sites. Williams PRD, Unice K, Scott P; ChemRisk pwilliams@chemrisk.com
Abstract: During the early 1900s, manufactured gas production (MGP) facilities supplied energy in the U.S. Because waste streams and equipment were often buried during the use or dismantling of these facilities, surface and/or subsurface soils at some former MGP sites have remained contaminated for many years. However, few published data sets exist on measured airborne concentrations of volatile compounds, such as benzene, during contact with or the disturbance of soils at these sites. We therefore provide an approach for estimating benzene in ambient air at former MGP sites based on emission (vapor and particulate) and air dispersion modeling techniques. Specifically, we characterize benzene air concentrations under several scenarios, including during the outdoor excavation of soil and in indoor environments. For these hypothetical scenarios, a soil column from 0 to 15 feet with maximum soil concentrations of benzene that ranged from 10 to 1,000 mg/kg for the 12 to 15 feet depth interval are used. Vapor emissions from subsurface soil are calculated using the USEPA’s EMSOFT model and the ASTM RBCA model for outdoor and indoor scenarios, respectively. Particulate emissions from the handling or disturbance of surface soils are calculated using the USEPA AP-42 model. Additional near field and air dispersion models are then used to calculate airborne concentrations of benzene in the breathing zone. We find that predicted benzene air concentrations for most scenarios range from approximately 0.001 ppm to 1 ppm, which is consistent with the limited published air sampling data collected at various MGP sites during excavation and other activities. Benzene exposures from incidental soil ingestion or dermal contact during these activities are estimated to be negligible. The modeling approach presented here should be useful for predicting benzene air concentrations at a number of sites where surface or subsurface soils may contain benzene.
|
M14.4 Predicting Indoor Vapor Concentrations for Buildings with Crawl Spaces. Rigby M.C., Liu S., Johnson K.M.*, Olliges S, Anderson T.H.; Tetra Tech, Inc.; Neptune and Company; NASA/Ames Research Center kay.johnson@tetratech.com
Abstract: To predict the migration of volatiles from subsurface sources into indoor air, California EPA and U.S. EPA both recommend the Johnson and Ettinger model. However, the Johnson and Ettinger model incorporates explicit assumptions about building construction. The Johnson and Ettinger model was explicitly designed for slab-on-grade buildings with a footer that goes under the slab. A model based on this assumption may not accurately predict the migration of volatiles into buildings with crawl spaces. These types of buildings have a raised floor (usually wooden) over a small compartment (i.e., the crawlspace) with a bare earth floor. Here, we will present a case study with measured VOC data from indoor air for a building with a crawl space, from the crawl space, and from groundwater. Then, we will compare the measured data to indoor vapor predictions from two different models - the Johnson and Ettinger model and a vapor intrusion model developed specifically for buildings with crawl spaces with an earth floor.
|
