غلظت های PCB و PBDE حاصل از نمونه برداری غیر فعال از محیط های داخل در مناطق شهری

عنوان انگليسی

Implications of Passive Sampling Derived Concentrations of Airborne PCBs and PBDEs in Urban Indoor Microenvironments

خلاصه انگلیسی

Introduction Polychlorinated biphenyls (PCBs) and polybrominated diethyl ethers (PBDEs) are ubiquitous environmental contaminants that are a cause of major environmental concern because of their persistence, ability to bioaccumulate and their potential impact on human health. Although most studies consider that the vast majority of human exposure to PCBs and PBDEs occurs via the dietary pathway; application of these compounds in building materials and products employed in indoors (i.e. furniture, electronic and electrical equipment) along with elevated indoor air concentrations 1-4 and the high proportion of time spent in such environments (i.e. typically more than 90%), implies that inhalation exposures may be significant for some people. Given the relative lack of data on airborne concentrations of PCBs and PBDEs in a wide range of indoor microenvironments, this study monitors these compounds in a series of domestic and workplace indoor microenvironments frequented by the UK population using Polyurethane Foam (PUF) disks as passive samplers. Experimental Procedures Passive air samplers as described by other authors5 were located at 23 different indoor microenvironments within the Birmingham and West Midlands area of the UK, including 12 homes, 10 offices, and one private car for sampling periods of between 4 and 6 weeks. To examine both seasonal trends and within-building variations in concentrations, sampling was conducted in two separate rooms within the same home/office (two homes and one office building) for 12 months. Previously described extract purification procedures were used with slight modifications for both PCBs and PBDEs1,2. GC/MS analysis and instrument specifications for PCBs and PBDEs were set up as described elsewhere1,2. The analytical method was assessed based on recoveries of surrogate/internal standards. As part of our ongoing quality control measures, the repeatability of our passive sampling and analytical procedures combined was evaluated by simultaneously deploying 5 samplers in the same domestic microenvironment. The low relative standard deviations observed for ΣPCB (7%) & ΣPBDE (18%) concentrations in this exercise demonstrate good repeatability for our sampling and analytical method. Generally, concentrations of PCBs and PBDEs in the 2 field blanks and 8 method blanks analysed were less than 5% of concentrations in samples and therefore sample data are uncorrected for blank levels. PUF disk sampling rates (R) for our target compounds were derived from our own calibration experiments (not reported here due to space restrictions). To estimate PBDE concentrations individual congener-based sampling rates were applied (1.1-1.9 m3/day). However for PCBs, the average R values for each homologue group (Tri-CB=0.72, Tetra-CB=0.70, Penta- CB=0.9, Hexa-CB=0.99 and hepta-CB=1.27 m3/day) were used due to the minimal variability of R values for individual isomers within each homologue group. Results and discussion Indoor air concentrations: The sampling locations and PCB & PBDE concentrations in indoor microenvironments along with outdoor air data from other studies are presented in Table 1. In the indoor environments studied, ΣPCB levels (sum of 63 congeners) ranged from 0.41 to 54.5 ng/m3 (mean = 5.2 and median = 2.55 ng/m3) and ΣPBDE levels (sum of congeners; 28, 47, 49, 66, 85, 99, 100, 153, and 154) varied from 5.1 to 1418 pg/m3 (mean = 148.2 and median = 38.4 pg/m3). To our knowledge, this is the first report on passive sampler-derived indoor air concentrations of PCBs. A previous study focused on highly contaminated indoor environments, reported levels of PCBs ranging from <100 to >6000 ng/m3 (mean = 790 ng/m3)4. However, our findings are in good agreement with the most spatially relevant study available for comparison, in which PCB levels between 1.1 and 69 ng/m3 (mean = 9.0 and median =3.9 ng/m3) were reported for 14 different indoor microenvironments from the West Midlands2. Importantly, t-test analysis revealed no statistically significant differences in ΣPCB concentrations between our data and those of the earlier study2 (P>0.34), suggesting that there has been no obvious decline in the contamination of indoor air with PCBs in the West Midlands over the last ca. 7 years. PBDE concentrations in this study are lower than those reported by Shoeib et al6 ranging from76.3 to 2088 pg/m3 and Harrad and co-workers1 (60-15509 pg/m3, mean=1855 pg/m3 and median =762 pg/m3). The reasons for these obvious variations are unclear but might be related to: differences in air sampling methods; unlike HiVols,1, 6 passive air samplers are not specifically designed to capture PBDEs present on particulate matter; the fact that the passive samplers provide concentrations that are time-weighted averages over 4-6 weeks under normal room-use conditions, rather than temporally brief snapshots recorded under more artificial conditions (e.g. no occupants due to sampler noise, and windows closed); as well as variations in concentrations between the different microenvironments sampled in different campaigns. This study’s data are comparable to but still lower than recently reported passive sampling results for ΣPBDEs in Canadian residential homes that reported a range between 2 and 3600 pg/m3 (mean = 260 and median = 100pg/m3).3 The differences between the two studies may be a reflection of the high profile of PBDE usage pattern in North America relative to Europe. Even though an appreciable proportion of ΣPBDEs are present in the particulate phase1; we compared our data with previously recorded data on concentrations of PCBs and PBDEs in West Midlands outdoor air using HiVol samplers1,7. The high indoor-outdoor gradients found in this study (on average 21 and 7 for PCBs and PBDEs, respectively) are in line with previous reports.1-3 These findings, along with the racemicchiral signatures of some PCB congeners in outdoor air 8,suggest that the ventilation of PCB and PBDE-contaminated indoor air provides a significant source of these compounds to outdoor air in the West Midlands conurbation.

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