AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Microbial Activity and Phthalate Degradation in Carpet
KAREN C. DANNEMILLER, Charles Weschler, Jordan Peccia, Ohio State University
Abstract Number: 662 Working Group: Indoor Aerosols
Abstract Floor dust is a major source of human exposure due to resuspension, especially from carpet. This dust contains a complex mixture of chemicals and a diverse microbial community. Chemicals may include phthalate esters, which can be present at elevated concentrations and are endocrine-disrupting compounds with public health significance. While aerobic microbial degradation of phthalate esters is well documented in aquatic systems and soils, biological transformation has not been demonstrated in house dust. The goal of this study was to quantify microbial degradation of phthalate esters. Worn carpet was sectioned into 10 cm x 10 cm coupons, embedded with dust from the same home, and incubated at constant elevated relative humidity. In the first experiment, carpets were incubated for 1-6 weeks at equilibrium relative humidity (ERH) between 50-100% and existing concentrations of nine phthalate esters were measured in the dust before and after. Di(2-ethylhexyl) phthalate (DEHP), benzyl butyl phthalate (BBzP), diisononyl phthalate (DiNP), and to a lesser extent di-n-octyl phthalate (DOP) demonstrated potential removal by chemical and/or microbial mechanisms. In the second experiment, 250 mg of dust was spiked with 10 µg deuterated di(2-ethylhexyl) phthalate (D-DEHP), embedded in carpet, and incubated at 100% ERH. As measured by sterilized controls, abiotic losses contributed 10.1% (±1.1%, standard error) of total D-DEHP after 1 week and 27.2% (±1.4%) of total D-DEHP after 3 weeks. Microbial degradation removed 8.5% (±1.7%) of the D-DEHP after one week, and at three weeks there was no additional loss with the total microbial loss at 8.2% (±2.7%). These losses were concomitant with fungal growth (above 80% ERH) and bacterial growth (at 100% ERH). Overall, this study supports the hypothesis that, in addition to abiotic chemical degradation and/or volatilization, microbes are also capable of degrading phthalates in house dust under elevated relative humidity conditions.