Lisa Melymuk

Estimation of PCB stocks, emissions, and urban fate: will our policies reduce concentrations and exposure?

PCBs, used to manage risks from the flammability of dielectric fluids and to increase the durability of elastic sealants, had declining environmental concentrations after legislation banning new production was passed during the 1970s and 1980s in Europe and North America. To answer why PCB temporal trends are now nearly stable and if current policies will further reduce concentrations and our exposure, we estimated PCB stocks in Toronto, Canada (population of approximately 2.5 million) of 437 (282-796) tonnes, of which 97 and 3% are in closed sources and building sealants, respectively. The greatest geographic density of PCBs is downtown, specifically in commercial, electricity-intensive skyscrapers. An unknown stock is within now-buried landfills and other waste-handling facilities as well as diffuse sources such as electrical wiring and paints. Using the Multimedia Urban Model, we estimated city-wide emissions of approximately 0.14-1.4 mg m(-2) y(-1) or 35-350 mg capita(-1) y(-1) of SigmaPCB(70), which is approximately 0.01-0.3% annually of total documented stocks. Canada, as one of 159 signatories of the Stockholm Convention and the 35 parties that have reported progress toward environmentally sound management of their PCB inventories by 2028, has passed national legislation with a timetable of inventory reductions. It is unclear whether this legislation will successfully reduce concentrations and exposures, however the analysis should inform our management of other contaminants.

Polychlorinated biphenyls in domestic dust from Canada, New Zealand, United Kingdom and United States: Implications for human exposure

Ingestion of indoor dust has been highlighted as an important pathway of exposure to brominated flame retardants. Hence, polychlorinated biphenyls (PCBs) were determined in indoor dust from homes in Amarillo/Austin, TX, USA (n=20; median concentration=200 ng Sigma PCB g(-1)); Birmingham, UK (n=20; 48 ng Sigma PCB g(-1)); Toronto, Canada (n=10; 260 ng Sigma PCB g(-1)); and Wellington, New Zealand (n=20; 46 ng Sigma PCB g(-1)). Concentrations in Canadian and US samples were statistically indistinguishable, but exceeded significantly (p<0.05) those in both New Zealand and UK dust. Principal component analysis revealed that while UK samples were enriched comparatively in lower molecular weight congeners; samples from other countries contained proportionally more mid-to-high molecular weight congeners. Concentrations of PCBs determined in air from the same 10 Canadian homes showed concentrations (median=4.9 ng Sigma PCB m(-3)) higher than those reported previously for UK homes (1.8 ng Sigma PCB m(-3)). Interpretation of these data alongside that for dietary exposure from other studies suggest that indoor exposures (i.e. air and dust combined) may be a significant contributor to overall exposure for the majority of the population - ranging from 4.3% to 87% in adults and 1.6-73% in toddlers. While inhalation is the principal indoor pathway under a typical dust ingestion scenario, exposure via dust ingestion exceeds that from either inhalation or diet for a small proportion of North American toddlers.

PCBs, PBDEs, and PAHs in Toronto air: Spatial and seasonal trends and implications for contaminant transport

The distributions of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of Toronto, Canada and the surrounding suburban/rural area were examined. A series of temporally- and spatially-distributed air samples was collected over a 1-year period with a high-volume active air sampler at one downtown site and polyurethane foam passive air samplers at 19 sites. Passive sampler air concentrations of ΣPAHs ranged from 0.27 to 51 ng/m³. Concentrations of ΣPCBs ranged from 6.0 to 1300 pg/m³, and concentrations of ΣPBDEs ranged from 0.47 to 110 pg/m³. All compounds exhibited the highest concentrations in the urban core, and lowest concentrations in the surrounding rural areas, however the exact ratio depended on location since concentrations varied considerably within the city. Results from the application of a radial dilution model highlighted the influence of the central business district (CBD) of the city as a source of contaminants to the surrounding environment, however the radial dilution comparison also demonstrated that sources outside the CBD have a significant influence on regional contaminant concentrations. A strong relationship between temperature and partial pressure of the gas-phase PCBs, low molecular weight PBDEs and less-reactive PAHs suggested that their dominant emissions originated from temperature-controlled processes such as volatilization from local sources of PCBs, PAHs and PBDEs at warm temperatures, condensation and deposition of emissions at cold temperatures, and ventilation of indoor air with elevated concentrations. The relationship between temperature and atmospheric PAH concentrations varied along the urban-rural gradient, which suggested that in highly urbanized areas, such as downtown Toronto, temperature-related processes have a significant impact on air concentrations, whereas winter emissions from domestic heating have a greater influence in areas with less impervious surface coverage.

Current Challenges in Air Sampling of Semivolatile Organic Contaminants: Sampling Artifacts and Their Influence on Data Comparability

With current science and policy needs, more attention is being given to expanding and improving air sampling of semivolatile organic contaminants (SVOCs). However, a wide range of techniques and configurations are currently used (active and passive samplers, different deployment times, different sorbents, etc.) and as the SVOC community looks to assess air measurements on a global scale, questions of comparability arise. We review current air sampling techniques, with a focus on sampling artifacts that can lead to uncertainties or biases in reported concentrations, in particular breakthrough, degradation, meteorological influences, and assumptions regarding passive sampling. From this assessment, we estimate the bias introduced for SVOC concentrations from all factors. Due to the effects of breakthrough, degradation, particle fractions and sampler uptake periods, some current passive and active sampler configurations may underestimate certain SVOCs by 30-95%. We then recommend future study design, appropriateness of sampler types for different study goals, and finally, how the SVOC community should move forward in both research and monitoring to best achieve comparability and consistency in air measurements.

Continuing sources of PCBs: the significance of building sealants.

To investigate the significance of building sealants as a remaining source of PCBs to the environment a combined measurement campaign and GIS-based stock estimation were undertaken for Toronto, Canada. This showed that 14% of buildings measured had detectable quantities of PCBs present in sealants, with concentrations from 0.57 mg/g to 82 mg/g (n=95). We then constructed a GIS-based database of remaining PCB-containing sealants in Toronto. This showed that there is an estimated 13 t still present in the city. Mass balance calculations showed that up to 9% had been lost via volatilization alone. This potentially has important implications for both human exposure and the continued presence of PCBs in the environment.

Particle Size Distribution of Halogenated Flame Retardants and Implications for Atmospheric Deposition and Transport

This study investigates the distribution of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and a group of novel flame retardants (NFRs) on atmospheric aerosols. Two high volume cascade impactors were used to collect particulate fractions of ambient air over a one year period at urban and rural sites. The majority of FRs were found on the finest aerosols (<0.95 μm). Concentrations of HBCD were higher than those of ΣPBDEs. Moreover, we noted seasonality and spatial differences in particle size distributions, yet a large portion of the observed differences were due to differences in particulate matter (PM) itself. When normalized by PM, the size distributions of the FRs exhibited much greater heterogeneity. Differences existed between the FR distributions by molecular weight, with the higher molecular weight FRs (e.g., BDE-209, Dechlorane Plus) distributed more uniformly across all particulate size fractions. The seasonal, spatial, and compound-specific differences are of crucial importance when estimating dry and wet deposition of FRs as smaller aerosols have longer atmospheric residence times. Estimated wet and dry deposition of four representative FRs (BDE-47, BDE-209, HBCD, and Dechlorane Plus) using size-segregated aerosol data resulted in lower deposition estimates than when bulk aerosol data were used. This has implications for estimates of long-range atmospheric transport and atmospheric residence times, as it suggests that without size-specific distributions, these parameters could be underestimated for FRs.

From the city to the Lake: loadings of PCBs, PBDEs, PAHs and PCMs from Toronto to Lake Ontario.

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

Application of Land Use Regression to Identify Sources and Assess Spatial Variation in Urban SVOC Concentrations

Land use regression (LUR), a geographic information system (GIS), and measured air concentrations were used to identify potential sources of semivolatile organic contaminants (SVOCs) within an urban/suburban region, using Toronto, Canada as a case study. Regression results suggested that air concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and polycyclic musks (PCMs) were correlated with sources at a scale of <5 km. LUR was able to explain 73-90% of the variability in PCBs and PCMs, and 36-89% of PBDE and PAH variability, suggesting that the latter have more spatially complex emission sources, particularly for the lowest and highest molecular weight compounds/congeners. LUR suggested that ~75% of the PCB air concentration variability was related to the distribution of PCBs in use/storage/building sealants, ~60% of PBDE variability was related to building volume, ~55% of the PAH variability was related to the distribution of transportation infrastructure, and ~65% of the PCM variability was related to population density. Parameters such as population density and household income were successfully used as surrogates to infer sources and air concentrations of SVOCs in Toronto. This is the first application of LUR methods to explain SVOC concentrations.

Perfluoroalkyl contaminants in Lake Ontario Lake Trout: detailed examination of current status and long-term trends.

Perfluoroalkyl contaminants (PFCs) were determined in Lake Ontario Lake Trout sampled annually between 1997 and 2008 in order to assess how current trends are responding to recent regulatory bans and voluntary phase-outs. We also combined our measurements with those of a previous study to provide an updated assessment of long-term trends. Concentrations of PFCs generally increased from the late 1970s until the mid-1980s to mid-1990s, after which concentrations either remained unchanged (perfluorooctane sulfonate (PFOS) and perfluorocarboxylates) or declined (perfluorodecanesulfonate (PFDS)). The temporal trends were assessed using three models, quadratic, exponential rise to maximum, and two-segment linear piecewise function, and then evaluated for best fit using Akaike Information Criteria. For PFOS and perfluorocarboxylates, the exponential rise to maximum function had the best fit. This is particularly interesting for PFOS as it suggests that although concentrations in Lake Ontario Lake Trout may have stopped increasing in response to voluntary phase-outs in 2000-2002, declines have yet to be observed. This may be due to continuing input of PFOS from products still in use and/or slow degradation of larger precursor molecules. A power analysis of PFOS suggested that 15 years of data with a within-year sample size of 10 is required to obtain sufficient power (80%) to detect a 5% decreasing trend. However, the length of the monitoring program had a greater influence on the ability to detect a trend compared to within-year sample size. This provides evidence that additional sampling years are required to detect a response to bans and phase-outs, given the variability in the fish data. The lack of observed declines of perfluorocarboxylate residues in fish may be expected as regulations for these compounds were only recently enacted. In contrast to the other compounds, the quadratic model had the best fit for PFDS. The results of this study emphasize the importance of long-term monitoring for assessing the effectiveness of bans and phase-outs on PFCs in the environment.

Organophosphate esters flame retardants in the indoor environment

Concentrations of 13 organophosphate ester flame retardants (OPEs) were measured in air, dust and window wipes from 63 homes in Canada, the Czech Republic and the United States in the spring and summer of 2013 to look for abundances, differences among regions, and partitioning behavior. In general, we observed the highest concentrations for halogenated OPEs, particularly TCEP, TCIPP and TDCIPP, and also non-halogenated TPHP. Differences between regions strongly depended on the matrix. The concentrations of OPEs in dust were significantly higher in the US than in Canada (CAN) and Czech Republic (CZ). CZ had the highest concentrations in window film and CAN in air. ΣOPE concentrations were 2-3 and 1-2 orders of magnitude greater than ΣBFRs in air, and dust and window films, respectively. We found a significant relationship between the concentrations in dust and air, and between the concentrations in window film and air for OPEs with log KOA values <12, suggesting that equilibrium was reached for these compounds but not for those with log KOA>12. This hypothesis was confirmed by a large discrepancy between values predicted using a partitioning model and the measured values for OPEs with log KOA values >12.