Theme: 09. Vapor Intrusion

Topic Area: 9d. Vapor Intrusion Risk Assessment and Site Management

Formatted Title:

Holiday Decorations and Plastic Toys as a Source of 1,2-DCA to Indoor Air Contamination

Background/Objectives:

Ambient and indoor air monitoring was performed at a former aerospace manufacturing site in southern California, including in an historical building that currently is used as a daycare facility. The air monitoring program is being implemented to evaluate the presence of volatile organic compounds (VOCs) in indoor air. Indoor air samples collected from the daycare building in 2007 and 2021 indicated that VOCs were detected at low levels below previous and current conservative agency air screening levels. However, in December 2022, 1,2-dichloroethane (1,2-DCA) was detected in indoor air samples collected from the daycare building at levels above the air screening level for this compound. 1,2-DCA is a compound of potential concern (COPC) at the site. Previous researchers have demonstrated 1,2-DCA emissions from holiday decorations as a source of indoor air contamination (measured emission rates as high as 0.3 micrograms [µg] 1,2-DCA per minute), and many holiday decorations were brought from offsite and placed throughout the daycare building space in December 2022.

Approach/Activities:

Subslab soil vapor monitoring pins were installed through the slab of the daycare building to collect subslab soil vapor samples and to evaluate the source of the 1,2-DCA in indoor air detected in the daycare building. Paired sets of subslab soil vapor and indoor air samples were collected. 1,2-DCA was not detected in any subslab samples at concentrations ranging from <0.72 to <0.87 micrograms per cubic meter (μg/m³), whereas it was detected in all of the indoor air samples at concentrations ranging from 0.086 to 1.6 μg/m³.

Results/Lessons Learned:

The data indicate that the relatively high 1,2-DCA concentrations detected in indoor air at the daycare building have an indoor source and are not a result of subsurface vapor intrusion. While 1,2-DCA concentrations declined after the holiday decorations were removed from the daycare building, subsequent monthly sampling confirmed continued elevated levels of 1,2-DCA compared with those in nearby buildings at the same site, collected during the same sampling events. There also is a large volume of small molded plastic toys and toy/material containers that are stored in the open in the daycare building, which may represent a continuing source of 1,2-DCA to indoor air.

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Ken Puentes