Andreas M. Buser

Stocks and flows of PBDEs in products from use to waste in the U.S. and canada from 1970 to 2020

The time-dependent stock of PBDEs contained in in-use products (excluding building materials and large vehicles) was estimated for the U.S. and Canada from 1970 to 2020 based on product consumption patterns, PBDE contents, and product lifespan. The stocks of penta- and octaBDE peaked in in-use products at 17,000 (95% confidence interval: 6000-70,000) and 4,000 (1,000-50,000) tonnes in 2004, respectively, and for decaBDE at 140,000 (40,000-300,000) tonnes in 2008. Products dominating PBDE usage were polyurethane foam used in furniture (65% of pentaBDE), casings of electrical and electronic equipment or EEE (80% of octaBDE), and EEE and automotive seating (35% of decaBDE for each category). The largest flow of PBDEs in products, excluding automotive sector, to the waste phase occurred between 2005 and 2008 at ∼10,000 tonnes per year. Total consumption of penta-, octa-, and decaBDE from 1970 to 2020 in products considered was estimated at ∼46,000, ∼25,000, and ∼380,000 tonnes, respectively. Per capita usage was estimated at 10-250, 10-150, and 200-2000 g·capita(-1)·y(-1) for penta-, octa-, and decaBDE, respectively, over the time span. Considering only the first use (no reuse and/or storage) of PBDE-containing products, approximately 60% of the stock of PBDEs in 2014 or ∼70,000 tonnes, of which 95% is decaBDE, will remain in the use phase in 2020. Total emissions to air of all PBDEs from the in-use product stock was estimated at 70-700 tonnes between 1970 and 2020, with annual emissions of 0.4-4 tonnes·y(-1) for each of penta- and octaBDE and 0.35-3.5 tonnes·y(-1) for decaBDE in 2014.

Concentrations in ambient air and emissions of cyclic volatile methylsiloxanes in Zurich, Switzerland

Tens of thousands of tonnes of cyclic volatile methylsiloxanes (cVMS) are used each year globally, which leads to high and continuous cVMS emissions to air. However, field measurements of cVMS in air and empirical information about emission rates to air are still limited. Here we present measurements of decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) in air for Zurich, Switzerland. The measurements were performed in January and February 2011 over a period of eight days and at two sites (city center and background) with a temporal resolution of 6-12 h. Concentrations of D5 and D6 are higher in the center of Zurich and range from 100 to 650 ng m(-3) and from 10 to 79 ng m(-3), respectively. These values are among the highest levels of D5 and D6 reported in the literature. In a second step, we used a multimedia environmental fate model parametrized for the region of Zurich to interpret the levels and time trends in the cVMS concentrations and to back-calculate the emission rates of D5 and D6 from the city of Zurich. The average emission rates obtained for D5 and D6 are 120 kg d(-1) and 14 kg d(-1), respectively, which corresponds to per-capita emissions of 310 mg capita(-1) d(-1) for D5 and 36 mg capita(-1) d(-1) for D6.

Emissions of Polychlorinated Biphenyls, Polychlorinated Dibenzo-p-dioxins, and Polychlorinated Dibenzofurans during 2010 and 2011 in Zurich, Switzerland

Persistent organic pollutants (POPs) are ubiquitous contaminants of environmental and human health relevance, but their emissions into the environment are still poorly known. In this study, concentrations of selected POPs were measured in ambient air in Zurich, Switzerland, and interpreted with a multimedia mass balance model. The aim of the combination of measurements and modeling was to back-calculate atmospheric emission rates of POPs. Measurements were performed in summer 2010 and winter 2011 and target analytes included polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Estimated emissions were higher in summer than in winter. Emission estimates for Zurich can be extrapolated to annual averages for Switzerland of 312 kg·a(-1) (39 mg·capita(-1)·a(-1)), 53 kg·a(-1) (7 mg·capita(-1)·a(-1)), and 3 kg·a(-1) (0.4 mg·capita(-1)·a(-1), 94 g WHO98-TEQ·a(-1), 65 g I-TEQ·a(-1)) for the six indicator PCBs (iPCBs), the twelve coplanar dioxin-like PCBs (dlPCBs), and the 17 2,3,7,8-chlorosubstituted PCDD/Fs, respectively. The emission rates of iPCBs are in agreement with existing emission inventories, whereas for PCDD/Fs the emissions are five times higher than the estimates from the Swiss national emission inventory. Emissions of dlPCBs in Switzerland are presented here for the first time. Our study also provides the first seasonally resolved emission rates of POPs, which were determined with our combined measurement and modeling approach. These findings highlight the relevance of ongoing sources of POPs, even decades after regulations aiming to reduce or eliminate sources were established.

Calculation of Physicochemical Properties for Short- and Medium-Chain Chlorinated Paraffins

Short- and medium-chain chlorinated paraffins are potential PBT chemicals (persistent, bioaccumulative, toxic) and short-chain chlorinated paraffins are under review for inclusion in the UNEP Stockholm Convention on Persistent Organic Pollutants. Despite their high production volume of more than one million metric tonnes per year, only few data on their physicochemical properties are available. We calculated subcooled-liquid vapor pressure, subcooled-liquid solubility in water and octanol, Henrys law constant for water and octanol, as well as the octanol-water partition coefficient with the property calculation methods COSMOtherm, SPARC, and EPI Suite™, and compared the results to experimental data from the literature. For all properties, good or very good agreement between calculated and measured data was obtained for COSMOtherm; results from SPARC were in good agreement with the measured data except for subcooled-liquid water solubility, whereas EPI Suite™ showed the largest discrepancies for all prope...

Good modeling practice guidelines for applying multimedia models in chemical assessments.

Multimedia mass balance models of chemical fate in the environment have been used for over 3 decades in a regulatory context to assist decision making. As these models become more comprehensive, reliable, and accepted, there is a need to recognize and adopt principles of Good Modeling Practice (GMP) to ensure that multimedia models are applied with transparency and adherence to accepted scientific principles. We propose and discuss 6 principles of GMP for applying existing multimedia models in a decision-making context, namely 1) specification of the goals of the model assessment, 2) specification of the model used, 3) specification of the input data, 4) specification of the output data, 5) conduct of a sensitivity and possibly also uncertainty analysis, and finally 6) specification of the limitations and limits of applicability of the analysis. These principles are justified and discussed with a view to enhancing the transparency and quality of model-based assessments.

Emissions of polybrominated diphenyl ethers (PBDEs) in Zurich, Switzerland, determined by a combination of measurements and modeling

Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants but they are of concern and are currently being phased-out because of their environmentally hazardous properties and their potential to cause adverse health effects. We analyzed PBDEs in Zurich, Switzerland, and applied a multi-media environmental fate model to back-calculate the rate of PBDE emission to air. PBDE concentrations in ambient air were measured in summer 2010 and winter 2011 in the city center of Zurich. Concentrations were higher in summer (sum PBDEs 118-591 pg m(-3)) than in winter (sum PBDEs 17-151 pg m(-3)), and are on the upper end of concentrations reported in literature for urban sites with no point sources of PBDEs. The emissions derived from our measurements (summer: 53-165 μg capita(-1) d(-1), winter: 25-112 μg capita(-1) d(-1)) and extrapolated to annual emissions for Switzerland (114-406 kg a(-1)) lie in the middle of ranges reported on the basis of substance flow analyses and emission inventories. The difference between summer and winter emissions is small compared to the difference that would be expected from the temperature dependence of PBDE vapor pressure, which would be consistent with emissions occurring to a large extent from flame-proofed materials located indoors under nearly constant temperature conditions and/or emissions to air occurring by suspension of particles containing PBDEs. Compared to previous studies in Switzerland, concentrations and emissions of PBDEs appear to have increased during the last five years with an increasing contribution of decabromodiphenyl ether, despite the addition of PBDEs to national and international regulations.

Emissions of decamethylcyclopentasiloxane from Chicago

Decamethylcyclopentasiloxane (D5) is a high-production-volume chemical that is emitted to air in tens of thousands of tonnes each year globally. However, specific information about emission rates to air is still limited. Here we present an estimate of D5 emissions from the city of Chicago based on measurements that have recently been published. We used a multimedia environmental fate model parameterized for Chicago to back-calculate the emission rate of D5 from the measurements. Our estimated average emission rate for D5 is 500 (2.5-to-97.5-percentile interval: 260-1100) kg d(-1). The corresponding per-capita emissions of 190 (100-420) mg capita(-1)d(-1) agree well with previous estimates for Europe and North America.

Quantification of Element Fluxes in Wastewaters: A Nationwide Survey in Switzerland

The number and quantities of trace elements used in industry, (high-tech) consumer products, and medicine are rapidly increasing, but the resulting emissions and waste streams are largely unknown. We assessed the concentrations of 69 elements in digested sewage sludge and effluent samples from 64 municipal wastewater treatment plants as well as in major rivers in Switzerland. This data set, representative of an entire industrialized country, presents a reference point for current element concentrations, average per-capita fluxes, loads discharged to surface waters, and economic waste-stream values. The spatial distribution of many individual elements could be attributed either to predominant geogenic or to anthropogenic inputs. Per-capita element fluxes ranged from <10 μg day-1 (e.g., Au, In, and Lu) to >1 mg day-1 (e.g., Zn, Sc, Y, Nb, and Gd) and >1 g day-1 (e.g., for P, Fe, and S). Effluent loads of some elements contributed significantly to riverine budgets (e.g., 24% for Zn, 50% for P, and 83% for Gd), indicating large anthropogenic inputs via the wastewater stream. At various locations, precious metal concentrations in sludge were similar to those in profitable mining ores, with total flux values of up to 6.8 USD per capita per year or 15 USD per metric ton of dry sludge.