A survey of PCB congeners in U.K. cows' milk.

Samples of unpasteurised bulked milk, taken directly from ten herds of dairy cattle on rural and urban farms in the north west of England on five separate sampling occasions, were analysed for a range of PCB congeners. Sigma PCB concentrations (sum of 37 congeners) ranged from 3.4-16.4 ng/g milk fat with a mean sigma PCB concentration of 8.4 ng/g milk fat. The dominating congeners were 118, 153, 138 and 180, which contributed 15%, 20%, 17% and 9% of the sigma PCB load respectively. The chlorine pattern of the congeners which made moderate or major contributions to the sigma PCB concentration were typically substituted at both para positions (4,4'), while the PCB congeners not detected in the milk had at least one ring that was not 4-substituted. These results indicate the 4,4' substitution pattern as being the key to PCB persistence in cows. It is estimated that consumption of typical daily intakes of milk with the PCB concentrations measured in this study would contribute 11% of the average daily sigma PCB intake for individuals in the UK. This contribution would increase to 30% when exposure through the consumption of dairy products prepared from such milk (e.g. cheese, butter) is taken into account. It is estimated that the inclusion of the TEF assigned PCBs would typically increase the TEQ rating of cows' milk by approximately 40% over that attributed to PCDD/Fs alone.

PCDD/Fs and non-o-PCBs in digested U.K. sewage sludges.

Twelve digested sewage sludges from rural and urban waste water treatment works in the north-west of England were analysed for PCDD/Fs and non-o-PCBs. The PCDD/F analysis of eight samples was repeated using high-resolution mass spectrometry, which enabled detection of the lower chlorinated congeners and calculation of TE values. sigma TEQ values for these eight samples ranged from 19-206 ng/kg with the higher values detected in the samples from urban/industrial areas. Examination of the congener/homologue profiles for the more contaminated samples suggests a major input from the use of pentachlorophenol. Archived sewage sludge samples collected and stored from one sewage treatment works in the south of England between 1942 and 1960 were analyzed to gain some insight into temporal trends and possible variations in source inputs. These provide some evidence of changing sources of PCDD/Fs over time and a decline in sigma TEQs since the 1950s.

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.

The relative contribution of individual polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-p-furans (PCDFs) to toxic equivalent values derived for bulked human adipose tissue samples from Wales, United Kingdom.

Five bulked human adipose tissue samples were analyzed for individual polychlorinated biphenyl (PCB) congeners (including selected non-ortho-substituted compounds) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Mean sigma PCB and sigma PCDD/F (tetra-through octachlorinated homologues) concentrations were 0.75 microgram/g and 1.22 ng/g adipose tissue respectively. Both the congener patterns and levels detected were similar to those reported by laboratories in other industrialised countries. Each sample comprised of tissue taken from donors within a given locality. However, no obvious relationships were apparent between sampling area, absolute concentrations and congener pattern of PCBs and PCDD/Fs. The contribution of individual PCDD/F and non-ortho-(o), mono-o-, and di-o-substituted PCB congeners to the total calculated toxic equivalent values (sigma TEQ) was assessed for each sample. The main contributions to the sigma TEQ were the mono-o-substituted PCB congeners #118 (TEQ = 42.5 pg/g of lipid), #156 (TEQ = 24.8 pg/g) and #105 (TEQ = 20.7 pg/g), followed by 1,2,3,6,7,8-HxCDD (TEQ = 18.2 pg/g), 2,3,4,7,8-P5CDF (TEQ = 12 pg/g), 1,2,3,7,8-P5CDD (TEQ = 11.5 pg/g), and the non-o-substituted PCB congener #126 (TEQ = 11.3 pg/g). Collectively, these compounds accounted for 80% of the sigma TEQ values. Based on the TEFs proposed by Safe (1990), the overall TEQs calculated for the monitored PCBs, were twice those due to sigma PCDD/Fs.