Ruth E. Alcock

Different Levels of Polybrominated Diphenyl Ethers (PBDEs) and Chlorinated Compounds in Breast Milk from Two U.K. Regions

Polybrominated diphenyl ether (PBDE) congeners are constituents of flame retardants, and there is growing concern regarding their persistence, bioaccumulation, and toxicity. We collected breast milk samples between late 2001 and early 2003 from 54 U.K.-resident mothers. Of these, 27 originated from southeast England (London), and the other 27 originated from northwest England (Lancaster). Analysis of milk-fat extracts by gas chromatography–mass spectrometry was performed to determine the levels of 15 PBDE congeners, 15 polychlorinated biphenyl (PCB) congeners, and other selected chlorinated compounds. PCB and organochlorine (OC) levels in southeast samples were consistently higher, and significant differences (p < 0.05) were observed. ∑PBDE levels ranged from 0.3 to 69 ng/g lipid (geometric mean, 6.6 ng/g), and PBDE-47 was the most abundant congener. ∑PCB levels ranged from 26 to 530 ng/g lipid (geometric mean, 150 ng/g) and were composed mainly of PCB-153 (26%), PCB-138 (20%), and PCB-180 (13%). OC levels for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDT) and its metabolites (∑DDX) ranged from 24 to 2,300 ng/g lipid (geometric mean, 160 ng/g); hexachlorobenzene ranged from nondetectable levels to 180 ng/g lipid (geometric mean, 17 ng/g); and ∑hexachlorocyclohexane levels ranged from 1.2 to 1,500 ng/g lipid (geometric mean, 16 ng/g). Using nuclear magnetic resonance–based metabonomics, samples (n = 7) containing the highest contaminant levels were compared with samples (n = 7) containing the lowest levels. Excellent separation along the first principal component implied that the chemical constituents of the two groups were significantly different. Although reasons for such differences remain obscure, lifestyle factors associated with a more heterogeneous London cohort could be responsible. Identifying primary routes of contaminant exposures and their biologic effects is of great importance.

Polychlorinated biphenyls (PCBs) in the British environment: Sinks, sources and temporal trends

This paper estimates the present UK environmental loading of polychlorinated biphenyls (PCBs). Of the estimated approximately 40,000 t SigmaPCB sold in the UK since 1954, only an estimated 1% (400 t) are now present in the UK environment. Comparisons of estimated production and current environmental loadings of congeners 28, 52, 101, 138, 153 and 180 suggest that PCB persistence broadly increases with increasing chlorination. Those PCBs that are not now present in the UK environment are considered to have been destroyed--by natural or anthropogenic mechanisms, to be still in use, to reside in landfills or to have undergone atmospheric and/or pelagic transport from the UK. The dramatic fall in PCB levels in archived UK soils and vegetation between the mid-1960s and the present is evidence that the latter mechanism is the most important and that a significant proportion of PCBs released into the UK environment in the 1960s have subsequently undergone environmental transport away from the UK. The bulk (93.1%) of the estimated contemporary UK environmental burden of SigmaPCBs is associated with soils, with the rest found in seawater (3.5%) and marine sediments (2.1%). Freshwater sediments, vegetation, humans and sewage sludge combined account for 1.4% of the present burden, whilst PCB loadings in air and freshwater are insignificant. Although consideration of individual congeners does not reveal any major deviations from the relative partitioning of Sigma PCBs, the importance of sinks other than soils is enhanced for individual congeners, particularly 138 and 180. In particular, around 2% of the total UK burden of congener 180 is present in humans, implying that biodata as a whole may constitute an important sink for the higher chlorinated congeners. The contemporary flux of SigmaPCBs to the UK surface is estimated at 19 t yr(-1), compared with an estimated annual flux to the atmosphere of 44-46 t. This implies that the major sources of PCBs to the UK atmosphere have been identified and that there is currently a net loss of these compounds from the UK. These sources are: volatilisation from soils (88.1%), leaks from large capacitors (8.5%), the production of refuse-derived fuel (RDF) (2.2%), leaks from transformers (0.6%), the recovery of contaminated scrap metal (0.5%) and volatilisation from sewage sludge-amended land (0.2%). Interestingly, whilst large excesses of estimated annual fluxes to the atmosphere over deposition fluxes for individual congeners exist for congeners 28, 52 and 101, estimates of fluxes in both directions across the soil-atmosphere interface agree closely for congeners 138, 153 and 180. This suggests that lower chlorinated congeners are more susceptible to both long-range environmental transport beyond the UK and to atmospheric degradation. Retrospective analysis of dated sediment cores, vegetation and soils indicates that environmental transport from North America and continental Europe introduced PCBs into the British environment well before the onset of their commercial production in the UK in 1954. Since that time, the input of PCBs to the UK environment has essentially reflected temporal trends in UK use. After peaking in the 1960s they declined rapidly through the 1970s following restrictions on PCB use. Recent evidence, however, is that the rate of decrease has diminished and that further significant reductions in fresh environmental input will take some time to occur. Such reductions will be especially slow for humans and other biota with long life-spans. This stems partly from cross-generational transfer from parents to offspring and also because the persistence of PCBs in biota means that present body burdens will reflect past as well as current exposure.

Dioxin-like PCBs in the environment - human exposure and the significance of sources

Dioxin-like PCBs represent an important component of the Sigma-TEQ in many environmental media. Specifically, in animal produce and in fish PCBs dominate the Sigma-TEQ ingested by humans. This in turn leads to high background body burdens in humans with PCB-TEQ greater than that associated with PCDD/Fs. High fish consumers are apparently subject to elevated TEQ exposure from dioxin-like PCBs. This has important implications for exposure assessment studies which have previously only been concerned with PCDDs and PCDFs. Unlike PCDD/Fs, dioxin-like PCBs are not controlled within the food chain. Sources and pathways of exposure are poorly defined. Aroclor formulations and their subsequent usage are considered to be the most important sources in terms of human exposure to some TEF-rated congeners, notably PCB-118, PCB-156 and part of PCB-126. Emissions from combustion sources contribute additional PCB-126. More research is needed to place these compounds in an integrated risk evaluation framework.

Understanding levels and trends of BDE-47 in the UK and North America : an assessment of principal reservoirs and source inputs.

Despite increasing interest in the occurrence of Polybrominated diphenyl ethers (PBDEs) in the environment, there has been only limited effort expended to identify principal source input reservoirs and pathways into the environment. Taking a single congener BDE-47, an important component of the penta commercial product, we have estimated principal contemporary reservoirs and emissions in two regions with very different historical use patterns. In North America, production and use of the penta-product has been rising steadily for the last 20 years, whilst in the UK, use has been restricted over the last 10 years, and most recently, there has been an EU ban on use. Mass balance models have been applied using our contemporary emission estimates to predict environmental levels. Results highlight that contemporary emissions to air can account for contemporary air concentrations but cannot account for measured concentrations in principal reservoirs such as soils and sediments. Future efforts are needed to improve our knowledge of the stocks of PBDEs in use, and emission factors from those stocks, to better understand/predict past and likely future trends.

Assessment of organic contanhnant fate in waste water treatment plants I: Selected compounds and physicochemical properties

An extensive and comprehensive literature review has been conducted for compounds which we hypothesise could be present in sludge and maintain their integrity following application to agricultural land. The following compounds have been selected for review; chlorinated paraffins, quintozene, brominated diphenyl ethers, polychlorinated naphthalenes, polydimethylsiloxanes, chloronitrobenzenes, and a range of biologically active and pharmaceutical compounds. All have received interest as a result of their persistence and/or toxicity in environmental media. Physicochemical property information has also been compiled and/or calculated. In this way, an accompanying paper will attempt to predict compound fate in waste water treatment plants (WWTPs) and assess likely transfers from soil/plants to grazing livestock. These papers describe a first attempt to predict the fate of these classes of compounds in the environment and prioritise those of greatest concern.

A congener-specific PCDD/F emissions inventory for the UK: do current estimates account for the measured atmospheric burden?

Considerable effort has been expended in the UK and elsewhere to quantify and rank PCDD/F primary sources and emissions to the environment, principally the atmosphere, so that cost-effective source reduction measures can be taken. Here, we predict a congener-specific emissions inventory for primary and secondary nondioxin-regulated sources to the UK atmosphere, estimated to have ranged from 3 to 22 kg in 1996. The inventory profile is dominated by OCDD (approximately 30-40%), 1,2,3,4,6,7,8-HpCDD (approximately 15-19%) and 1,2,3,4,6,7,8-HpCDF (approximately 14-19%). Congeners 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD dominate the sigmaTEQ composition. Mass balance modelling suggests that the predicted congener pattern in UK air (based on the emission inventory) is similar to observed measurements, with absolute concentrations being estimated within a factor of 2 for most congeners. Calculations taking into account atmospheric weathering processes and long range (advective) transport suggest that PCDD/F sources to ambient air are primarily ongoing and that atmospheric mixing will mask individual emission source profiles/identities. This supports measured evidence for the consistency of PCDD/F air profiles observed around the UK throughout the year.

Contamination of Environmental Samples Prepared for PCB Analysis

Archived air-dried soil that had been collected, stored, and sealed in 1914, before the commercial manufacture of PCBs, together with wet freshly sampled ancient peat, which contained little or no PCBs, were exposed to contemporary air in a laboratory. Measurable increases in the concentration of PCBs, particularly the low molecular weight congeners, were detectable after exposure for as little as a few hours. Concentrations after a few days exposure to laboratory air were similar to those measured in contemporary field surface soils (-20-30 pg of CPCB kgl). Laboratory air concentrations ranged between 4.7 and 8.2 ng of CPCB m-3 during the period of exposure, markedly higher than routinely detected in outdoor U.K. urban air. The calculated average net dry deposition flux from air-soil in the laboratory over 25 days was 5 pg of CPCB m-2 day1. Indoor air concentrations might be expected to be higher than those routinely measured outside, exacerbating the potential problems of sample contamination. Extreme caution is needed in the preparation and handling of samples which contain inherently low concentrations of PCBs and before ascribing the presence of these compounds in certain samples to ‘natural production’ mechanisms.

Kinetic constraints on the loss of organic chemicals from contaminated soils: Implications for soil-quality limits.

Generic or site-specific soil-quality limits for organic contaminants have been adopted or proposed in various countries in an effort to control or assess contamination. The most comprehensive generic limits, established in the Netherlands, distinguish between background concentrations for naturally occurring substances and analytical detection limits for man-made organic compounds (target values) and threshold concentrations above which remediation may be necessary (intervention values). These are being employed to highlight contaminated sites that require treatment/remediation, ideally resulting in the reduction of the compounds of concern. These limits have been derived in a number of ways but are largely based on professional judgment, usually on information concerning pathways of human exposure, phytotoxicity, and ecotoxicological effects. Effective remediation of contaminated soils is frequently limited by the slow kinetics of contaminant loss from soils under prevailing environmental conditions. This is frequently underestimated, even though it may be of fundamental importance in determining the success of treatment/remediation with respect to the assigned quality limits. This is because loss of contaminants from soils is often biphasic, whereby a short period of rapid dissipation is followed by a longer period of contaminant release. Dissipation processes, including leaching and volatilization, exhibit similar behavior. The primary rate-limiting factors governing this behavior are postulated to be fundamental sorption/ desorption mechanisms, including intraparticle diffusion, intrasorbent diffusion and chemisorption, which control the distribution of contaminant between the solid and aqueous or gaseous phases of soils and, hence, the supply of contaminant available to the various dissipation processes. In this article, we consider the relevance of biphasic desorption kinetics to existing soil-quality limits. We contend that the concentration of a given contaminant in a given soil when the “residual” phase of dissipation is reached represents an intrinsic kinetic constraint to the remediation of contaminated soil. Because of the effects of the primary rate-limiting mechanisms discussed above, it is unlikely that (in the absence of any engineering solution to the problem) any appreciable change in the contaminant concentration will occur over practical time scales under prevailing environmental conditions for a given soil. We define this contaminant concentration as a kinetically constrained soil quality limit (KCSQL) and apply it to selected examples of contaminant dissipation from the literature, including polychlorinated biphenyls, polynuclear aromatic hydrocarbons, industrial solvents, and pesticides in a range of soils. Finally, we examine the relationship between the derived KCSQLs and the Dutch “cleanup” values and soil-quality criteria adopted in other countries.

Polychlorinated biphenyls in digested UK sewage sludges

Abstract Twelve sewage sludges from rural, urban and industrial waste water treatment works in north west England were analysed for polychlorinated biphenyls by capillary GC-ECD. The total polychlorinated biphenyl content ranged between 106 to 712 μg/kg, with a mean of 292 μg/kg. Di- and penta-chlorinated congeners made the greatest contribution to the ΣPCB concentrations at most sites. The 6 IUPAC congeners were found in the following order of abundance, 101>180>153>138>52>28. Industrial inputs would appear to influence levels of ΣPCB in the sludge. If these sludges were ploughed into arable land at typical rates only a slight elevation in soil ΣPCB levels would result. Alternatively, if the same quantity of sludge were applied to the surface of pasture grassland, significant elevations in the potential transfer of PCBs to grazing livestock may result.

A generic model of human lifetime exposure to persistent organic contaminants: development and application to PCB-101.

We have developed a model which successfully reconstructs the lifetime polychlorinated biphenyl (PCB)-101 burden of the UK population for individuals born between 1920 and 1980. It not only follows burdens and clearance of persistent organic contaminants throughout a human lifetime--taking changes in age and body composition into account--but also, importantly, incorporates changing environmental concentrations of the compound of interest. Predicted results agree well with available measured lipid concentrations in human tissues. Its unique construction takes into account both changing environmental concentrations of PCBs in principal food groups and changing dietary habits during the time period. Because environmental burdens of persistent organic contaminants have changed over the last 60 years, residues in food will also have mirrored this change. Critically in this respect, the year in which an individual was born determines the shape and magnitude of their exposure profile for a given compound. Observed trends with age represent an historical legacy of exposure and are not simply a function of equal yearly cumulative inputs. We can demonstrate that the release profile of PCB-101 controls levels in the food supply and ultimately the burden of individuals throughout their life. This effect is expected to be similar for other PCB congeners and persistent organic compounds such as polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs). Models of this type have important applications as predictive tools to estimate the likely impact of source-reduction strategies on human tissue concentrations.