Mitigation of building-related polychlorinated biphenyls in indoor air of a school

Table 1 Median concentration of polychlorinated biphenyls in indoor air before and after implementation of three mitigation measures, normalizing for temperature and ventilation rates.

Period	Number of Rooms	Median (ng/m³)¹	H₀: medians are equal (p-value)⁶
Ventilation ²
August 25-27, 2010	9	432	< 0.01
September 6, 2010	10	149
Encapsulation: Directly Accessible Caulk ³
September 6, 2010	10	282	0.08
September 19, 2010	7	220
Encapsulation: Behind Built-in Equipment and Furniture ⁴
September 19, 2010	7	220	0.02
September 29, 2010	5	133
False Wall ⁵
September 29, 2010	5	133	< 0.01
Nov. 4 - Dec. 2, 2010	19	76

¹ Median of temperature-normalized and ventilation-normalized concentrations
² Ventilation rates were improved by replacing filters and repairing fans in the unit ventilators. Median of temperature-normalized, but not ventilation-normalized concentrations.
³ PCB-containing caulk along the interior face of transite panels open to classrooms was covered with adhesive-backed polyethylene tape and sealed with silicone caulk.
⁴ PCB-containing caulk located behind unit ventilators and convective heaters was covered with adhesive-backed polyethylene tape and sealed with silicone caulk.
⁵ False walls constructed over encapsulated PCB caulk and adjoining transite panels and framing.
⁶ Wilcoxon rank sum test of the hypothesis that the median pre-intervention and post- intervention concentrations are equal.

ISSN: 1476-069X