Accounting for intended use application in characterizing the contributions of cyclopentasiloxane (D5) to aquatic loadings following personal care product use: Antiperspirants,skin care products and hair care products

Decamethylcyclopentasiloxane, commonly known as D5 (cyclopentasiloxane) has a wide application of use across a multitude of personal care product categories. The relative volatility of D5 is one of the key properties attributed to this substance that provide for the derived performance benefits from the use of this raw material in personal care formulations. On this basis, rapid evaporative loss following use of many products comprising D5 is expected following typical use application and corresponding wear time.     

Monitoring and modelling of siloxanes in a sewage treatment plant in the UK

Monitoring of cyclic volatile methylsiloxanes (cVMS) carried out at Anglian Water’s Broadholme sewage treatment plant (STP) is described. The method deployed used headspace gas chromatography/mass spectrometry (HS-GC/MS) and the addition of isotopically labelled cVMS to correct for partitioning in samples containing high levels of particulate and dissolved organic carbon. The method was capable of measuring cVMS in raw sewage samples, with recoveries of 80%, 85% and 71% respectively, for D₄, D₅ and D₆. The limit of quantification was 0.2 μg L⁻¹ for all three substances. Recoveries close to 100% were observed for all cVMS spiked into treated effluent (LOQ = 0.01 μg L⁻¹). Despite the volatile nature of cVMS and its ubiquitous presence in the ambient atmosphere, the methods deployed showed excellent recoveries, reproducibility and quantification limits. A distinct diurnal variation in cVMS concentration, probably linked with the use of personal care products was observed for raw sewage but not in treated sewage effluent. The estimated per capita consumption of D₅ (∼2.7 mg cap⁻¹ d⁻¹) derived for the population served by this plant was significantly lower than that derived in the Environment Agency (UK) risk assessment (11.6 mg cap⁻¹ d⁻¹). The cVMS were highly removed during sewage treatment with efficiencies greater than 98%. The methods and findings of this pilot study can be used as the basis for future studies on the fate of cVMS substances in STPs.     

Is PCBs concentration variability between and within freshwater fish species explained by their contamination pathways?

Many chemical, physiological, and trophic factors are known to affect bioaccumulation of polychlorinated biphenyls (PCBs) in biota. Understanding the primary factors affecting fish contamination is critical for predicting and assessing risks to upper-trophic level consumers, including humans. Here we identify PCB contamination pathways that could explain within- and between-species variability in fish concentration levels. Three freshwater river fish species (barbel, chub and bream) were sampled at three sites along the Rhone River (France) where fish consumption is partially prohibited because of PCB levels exceeding the European health-based benchmark. The trophic position was assessed using an innovative approach based on stable isotope analyses and Bayesian inference, which takes into account both isotope data variability and parameter uncertainty. The effect of foraging habitat on fish contamination was addressed using stable isotope mixing models. The fish trophic position and PCB concentrations were found to be unrelated while the exploitation of sediment detrital carbon as a food source appeared to be a critical factor affecting fish contamination. Fish length, PCB concentration of the sediment, and individual fish foraging habitat (exploitation of detrital versus planktonic carbon sources) explained 80% of within- and between-species variability observed in PCB concentrations. These results, obtained for species that have overlapping TPs and exploit different carbon sources, reveal that the important factor in fish PCB contamination is not only what fish consume, but also and essentially the feeding location.     

Particulate matter in new technology diesel exhaust (NTDE) is quantitatively and qualitatively very different from that found in traditional diesel exhaust (TDE)

Diesel exhaust (DE) characteristic of pre-1988 engines is classified as a "probable" human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC), and the U.S. Environmental Protection Agency has classified DE as "likely to be carcinogenic to humans." These classifications were based on the large body of health effect studies conducted on DE over the past 30 or so years. However, increasingly stringent U.S. emissions standards (1988-2010) for particulate matter (PM) and nitrogen oxides (NOx) in diesel exhaust have helped stimulate major technological advances in diesel engine technology and diesel fuel/lubricant composition, resulting in the emergence of what has been termed New Technology Diesel Exhaust, or NTDE. NTDE is defined as DE from post-2006 and older retrofit diesel engines that incorporate a variety of technological advancements, including electronic controls, ultra-low-sulfur diesel fuel, oxidation catalysts, and wall-flow diesel particulate filters (DPFs). As discussed in a prior review (T. W. Hesterberg et al.; Environ. Sci. Technol. 2008, 42, 6437-6445), numerous emissions characterization studies have demonstrated marked differences in regulated and unregulated emissions between NTDE and "traditional diesel exhaust" (TDE) from pre-1988 diesel engines. Now there exist even more data demonstrating significant chemical and physical distinctions between the diesel exhaust particulate (DEP) in NTDE versus DEP from pre-2007 diesel technology, and its greater resemblance to particulate emissions from compressed natural gas (CNG) or gasoline engines. Furthermore, preliminary toxicological data suggest that the changes to the physical and chemical composition of NTDE lead to differences in biological responses between NTDE versus TDE exposure. Ongoing studies are expected to address some of the remaining data gaps in the understanding of possible NTDE health effects, but there is now sufficient evidence to conclude that health effects studies of pre-2007 DE likely have little relevance in assessing the potential health risks of NTDE exposures.     

The feasibility of decontamination of reduced saline sediments from copper using the electrokinetic process

The remediation of metal contamination in estuarine and reduced sediments is another challenge for the electrokinetic process. Problems result from the complex chemical composition of saline reduced sediments. In the experiments described here copper was added into saline reduced sediments to simulate the natural situation. Two constant voltages were applied across the electrokinetic cell to investigate the effect of an increase in potential difference on the electrokinetic process. Acetic acid at pH 6 and 4 was also added to the cathode in separate experiments to enhance copper removal. The results from this study showed that in the unenhanced experiments most of copper remained in the soil and was unaffected by the electrokinetic process. At the end of unenhanced electrokinetic experiments, the copper concentration was found only to be slightly changed in the anode region. Up to 21% of the copper was found precipitated near the anode when the applied voltage was 10V and this increased to 25% when the applied voltage was 7V. In the enhanced electrokinetic experiments up to 98% of copper was removed from section 1 and precipitated again in sections 2 and 3. This indicates that a significant amount copper removal from the saline sediments may be achieved by the enhanced electrokinetic process.     

Spatial analysis of a large magnitude erosion event following a Sierran wildfire

High intensity wildfire due to long-term fire suppression and heavy fuels buildup can render watersheds highly susceptible to wind and water erosion. The 2002 "Gondola" wildfire, located just southeast of Lake Tahoe, NV-CA, was followed 2 wk later by a severe hail and rainfall event that deposited 7.6 to 15.2 mm of precipitation over a 3 to 5 h time period. This resulted in a substantive upland ash and sediment flow with subsequent down-gradient riparian zone deposition. Point measurements and ESRI ArcView were applied to spatially assess source area contributions and the extent of ash and sediment flow deposition in the riparian zone. A deposition mass of 380 Mg of ash and sediment over 0.82 ha and pre-wildfire surface bulk density measurements were used in conjunction with two source area assessments to generate an estimation of 10.1 mm as the average depth of surface material eroded from the upland source area. Compared to previous measurements of erosion during rainfall simulation studies, the erosion of 1800 to 6700 g m(-2) mm(-1) determined from this study was as much as four orders of magnitude larger. Wildfire, followed by the single event documented in this investigation, enhanced soil water repellency and contributed 17 to 67% of the reported 15 to 60 mm ky(-1) of non-glacial, baseline erosion rates occurring in mountainous, granitic terrain sites in the Sierra Nevada. High fuel loads now common to the Lake Tahoe Basin increase the risk that similar erosion events will become more commonplace, potentially contributing to the accelerated degradation of Lake Tahoe's water clarity.     

Phenotypic variation in shell form in the intertidal acorn barnacle Chthamalus montagui: distribution,response to predators and life history trade-offs

The acorn barnacle Chthamalus montagui can present strong variation in shell morphology, ranging from flat conic to a highly bent form, caused by a substantial overgrowth of the rostrum plate. Shell shape distribution was investigated between January and May 2004 from geographical to microhabitat spatial scales along the western coast of Britain. Populations studied in the north (Scotland and Isle of Man) showed a higher degree of shell variation compared to those in the south (Wales and south-west England). In the north, C. montagui living at lower tidal levels and in proximity to the predatory dogwhelk, Nucella lapillus, were more bent in profile. Laboratory experiments were conducted to examine behavioural responses, and vulnerability of bent and conic barnacles to predation by N. lapillus. Dogwhelks did not attack one morphotype more than the other, but only 15 % of attacks on bent forms were successful compared to 75 % in conic forms. Dogwhelk effluent reduced the time spent feeding by C. montagui (11 %), but there was no significant difference between conic and bent forms. Examination of barnacle morphology indicated a trade-off in investment in shell structure and feeding appendages associated with being bent, but none with egg or somatic tissue mass. These results are consistent with C. montagui showing an induced defence comparable to that found in its congeners Chthamalus anisopoma and Chthamalus fissus on the Pacific coast of North America, but further work to demonstrate inducibility is required.