Biomedical subjects

K C Jones

Publications and source records attributed to K C Jones.

At least 91 records · Page 5Linked to original sources

PubMed1996

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.

Animals↗

PubMed1996

Contribution of coplanar and non-coplanar polychlorinated biphenyls to the toxic equivalence of grey seal (Halichoerus grypus) milk.

We measured the concentration of coplanar polychlorinated biphenyl (PCB) congeners #77, #126 and #169 in the milk of 21 individual grey seals (Halichoerus grypus) from the same Scottish colony. Using the toxic equivalency factors (TEFs) of Ahlborg et al. (1994) we found TEQs ranged between 8.4 and 45.7 pg/g, with a mean of 22.3 +/- 9.3 pg/g on a lipid weight basis (n = 32). For some samples we also had concentrations of mono-ortho and di-orthochlorinated PCBs. Inclusion of these congeners approximately doubled the TEQ. There was a good correlation between the concentration of non-ortho PCBs and that of other congeners in the same sample.

Animals↗

PubMed1996

Persistence and fate of polychlorinated biphenyls (PCBs) in sewage sludge-amended agricultural soils.

Four metal enriched sewage sludges containing different concentrations of polychlorinated biphenyls (PCBs) were applied to two field soils in the UK in 1968. Samples of the sludges, sludge-amended soils and soils from untreated control plots were stored and analysed retrospectively. Sludge concentrations ranged from 1 to 7 mg SigmaPCB kg(-1). The pattern of PCBs was similar in three of the four sludges, with congeners 14, 18, 28 and 52 present at the highest concentrations. The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. SigmaPCB concentrations in control plot soil have declined over the last 20 years, indicating a reduction in atmospheric deposition inputs of PCBs to the soil. SigmaPCB concentrations also declined on the sludge-amended plots, reaching control plot concentrations (30-60 microg SigmaPCB kg(-1)) in the late-1980s. Half-lives ranged from < 1 to 8.5 years for congeners 18, 28 and SigmaPCB. Biodegradation and/or the formation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important loss process on both the control and sludge-amended plots. Using the fugacity approach, congener concentrations in soils at Luddington were predicted still to have not reached equilibrium with the air. Further losses to the atmosphere are likely.

Journal Article↗

PubMed1995

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.

England↗

PubMed1995

Polynuclear aromatic hydrocarbons in the United Kingdom environment: a preliminary source inventory and budget.

This paper presents the first attempt to quantify the production, cycling, storage and loss of PAHs in the UK environment. Over 53 000 tonnes of sigmaPAHs (sum of 12 individual compounds) are estimated to reside in the contemporary UK environment, with soil being the major repository. If soils at contaminated sites are included, this estimate increases dramatically. Emission of PAHs to the UK atmosphere from primary combustion sources are estimated to be greater than 1000 tonnes sigmaPAHs per annum, with over 95% coming from domestic coal combustion, unregulated fires and vehicle emissions. It is estimated that approximately 210 tonnes of sigmaPAH are delivered to terrestrial surfaces each year via atmospheric deposition. Therefore, inputs of PAHs to the UK atmosphere outweigh the outputs by a factor of over 4. This may be explained by enhanced particulate deposition near point sources, PAH degradation in the atmosphere and transport away from the UK with prevailing winds. Disposal of waste residues is estimated to contribute a further 1000 tonnes of sigmaPAH per year to the terrestrial environment. It is illustrated that the use of creosote has the potential to release considerable quantities of PAHs to the UK environment. Temporal trends in PAH cycling are then considered. There is good evidence to suggest that air concentrations and fluxes to the UK surface are now lower than at any time throughout this century. Nonetheless, the UK sigmaPAH burden is still increasing at the present time, principally through retention by soils. However, there are marked differences in the behaviour of individual compounds: there is evidence, for example, that phenanthrene concentrations in soils have declined since the 1960s, although soil concentrations of benzo[a]pyrene and other heavier PAHs have continued to increase through this century. Volatilisation of low molecular weight PAHs accumulated in soils over previous decades may be making an important contribution to the current atmospheric burden. The major uncertainties identified by data on this budget are: (1) the lack of PAH concentrations in some environmental matrices; (2) the possible importance of contaminated soils as a major repository and source of PAHs; (3) the lack of emission data (especially vapour phase releases) for some PAH sources; (4) the importance of biodegradation and volatilisation as loss mechanisms for low molecular weight PAHs in soils; and (5) the importance of creosote use in the PAH cycle.

Journal Article↗

PubMed1994

A model for the tissue factor pathway to thrombin. II. A mathematical simulation.

A mathematical simulation of the tissue factor pathway to the generation of thrombin has been developed using a combination of empirical, estimated, and deduced rate constants for reactions involving the activation of factor IX, X, V, and VIII, in the formation of thrombin, as well as rate constants for the assembly of the coagulation enzyme complexes which involve factor VIIIa-factor IXa (intrinsic tenase) and factor Va-Xa (prothrombinase) assembled on phospholipid membrane. Differential equations describing the fate of each species in the reaction were developed and solved using an interactive procedure based upon the Runge-Kutta technique. In addition to the theoretical considerations involving the reactions of the tissue factor pathway, a physical constraint associated with the stability of the factor VIIIa-factor IXa complex has been incorporated into the model based upon the empirical observations associated with the stability of this complex. The model system provides a realistic accounting of the fates of each of the proteins in the coagulation reaction through a range of initiator (factor VIIa-tissue factor) concentrations ranging from 5 pM to 5 nM. The model is responsive to alterations in the concentrations of factor VIII, factor V, and their respective activated species, factor VIIIa and factor Va, and overall provides a reasonable approximation of empirical data. The computer model permits the assessment of the reaction over a broad range of conditions and provides a useful tool for the development and management of reaction studies.

Blood Coagulation Factors↗

PubMed1994

Polychlorinated biphenyls (PCBs) in the UK population: estimated intake, exposure and body burden.

This paper presents a detailed congener-specific estimate of PCB exposure to the UK population. The average sigma PCB intake (i.e. the sum of IUPAC congeners No. 28, 44, 52, 61/74, 66, 99, 101, 105, 110, 118, 138, 151, 153, 156, 170, 180, 183, 187, 189, 194/205, 201, 202, 206 and 209) for the contemporary UK population was estimated to be 0.53 micrograms/person/day. Food consumption accounted for 97% of the sigma PCB exposure, with fish, milk and dairy products, vegetables and meat and animal fat accounting for 32, 24, 24 and 15%, respectively. The congener pattern for different food products varied, with vegetables playing a major part in the intake of lower chlorinated compounds, whilst fatty foods such as fish, dairy products and meat, were of greater importance for the intake of higher chlorinated compounds. Theoretical body burdens and body fat concentrations of selected PCB congeners were derived for the UK population, based on the estimated contemporary human daily intake of PCBs and a number of assumptions. PCB body burdens and adipose tissue concentrations were generally predicted to increase with age. However, adipose concentrations increased at a slower rate in the older population, due to a dilution effect caused by the increase in body fat weight with age. These theoretical estimates were then compared with measured values for adipose tissue from the Welsh population. Theoretical body burdens and adipose tissue concentrations (not accounting for any metabolic losses) were below the actual values measured for the contemporary Welsh population by between a factor of 2.5 and 4. This discrepancy becomes greater when metabolic losses are included, and probably occurs because present day exposure to PCBs through foodstuffs is likely to be lower than in the past. The lower chlorinated congener No. 28 is more readily removed from the body and is predicted to reach an equilibrium concentration in humans. In contrast, the higher chlorinated No. 153 was predicted to accumulate in the body throughout life. The effect of PCB transfer via breast milk is shown to be important in lowering the body burden of the mother (by approximately 20% over 3 months) and substantially increasing that in the offspring.

Adipose Tissue↗

PubMed1994

Dehydrogenase activity of the microbial biomass in soils from a field experiment amended with heavy metal contaminated sewage sludges.

Dehydrogenase activity (DHA) of the microbial biomass was measured in sewage sludge amended soil samples collected from the Braunschweig experimental site, Germany. The site had received additions of sludge with or without heavy metals at two application rates (100 m3/ha per year and 300 m3/ha per year) on soils of 'low' (4.8-5.8) and 'high' (5.4-7.0) pH since 1980. DHA was found to be a sensitive and precise assay for determining the effect of heavy metals on substrate-induced (glucose) microbial biomass in sewage sludge amended soils. Effects on DHA were determined in relation to heavy metal concentrations and other soil factors. Addition of relatively uncontaminated sludge enhanced DHA, but this was dependent on the level and type of sludge addition. Adverse metal effects were only significant in the most contaminated soils where sludge had been added to the 'high' and 'low' pH treatments at Braunschweig. However, these effects were small compared to the effects of high rates of sludge addition alone, despite exceeding statutory limits for Zn and Cu, where concentrations reached 341 and 99 micrograms/g, respectively.

Hydrogen-Ion Concentration↗

PubMed1994

PCBs and other organochlorines in human tissue samples from the Welsh population: I--Adipose.

The general exposure of humans to polychlorinated biphenyls (PCBs) and SigmaDDT (i.e., p,p'-DDT + p,p'DDE = p,p'-DDD) in Wales (UK) was determined through the analysis of adipose tissue samples collected from 75 individuals during post-mortem examinations in 1990-1991. Fifty PCB congeners were screened, of which 29 were identified in most of the samples. Congener IUPAC numbers 138, 153 and 180 were the most abundant compounds, accounting for an average of 55% of the SigmaPCB congeners analysed. SigmaPCB concentrations varied between 0.2 and 1.8 microg g(-1) of adipose tissue and were positively correlated with the donors age and negatively associated with the percentage of lipid in the adipose tissue. A progressive change in the congener pattern was noted with increasing subject age. Tissue from older individuals generally contained a relatively high proportion of the more persistent and higher chlorinated congeners. SigmaDDT concentrations ranged from 0.11 to 5.6 microg g(-1) adipose tissue, with p,p'-DDE contributing 96% towards the SigmaDDT concentration. SigmaDDT levels were also positively correlated with age. No significant differences in the SigmaPCB and SigmaDDT concentrations were noted between males and females, between people living in rural and urban locations or with the subjects' body weight at the time of their death.

Journal Article↗

PubMed1994

PCBs and other organochlorines in human tissue samples from the Welsh population: II--Milk.

Polychlorinated biphenyl (PCB) and SigmaDDT (i.e. p,p'-DDT + p,p'-DDE = p,p'-DDD) concentrations were determined from the analysis of 115 Welsh breast milk samples collected in 1990 and 1991. Fifty PCB congeners were screened, of which 24 were identified in most samples. The PCB congener pattern was consistent between individual milk samples, with IUPAC congeners 28, 138, 153 and 180 being the most abundant and accounting for an average of 50% of the SigmaPCB concentrations determined. PCB concentrations varied between 2 and 70 ng g(-1) whole milk, were positively correlated with age, and negatively correlated with the total lactation period and with the percent lipid content of the milk. PCB pattern distributions differed between milk and adipose tissue samples. Human milk had a higher proportion of tri- (18 and 28), tetra- (44, 52 and 66) and pentachlorinated biphenyls (101) compared to human adipose tissue. SigmaDDT concentrations ranged from 0.3 to 71 ng g(-1) of whole milk, with p,p'-DDE contributing towards an average of 92% of the SigmaDDT concentrations. SigmaDDT levels were also positively correlated with age and negatively associated with the lactation period, though these correlations were rather weak. No significant differences in the SigmaPCB and SigmaDDT concentrations were noted between milk samples from donors living in rural and urban locations, or between the subjects' body weight, smoking habits or diet.

Journal Article↗

PubMed1994

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.

Journal Article↗

PubMed1994

The influence of sewage sludge applications to agricultural land on human exposure to polychlorinated dibenzo-p-dioxins (PCDDs) and -furans (PCDFs).

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) are organic chemicals of suspected extreme toxicity. PCDD/Fs are ubiquitous in the environment and relatively enriched in sewage sludges. The deliberate application of sewage sludge to agricultural land can therefore potentially increase exposure of the human population to these compounds via transfers through the foodchain. This paper presents a protocol for assessing the background human exposure to all seventeen 2,3,7,8-substituted PCDD/Fs for which toxic equivalent factors (TEFs) are available. Background daily human exposure in the UK to 2,3,7,8-T(4)CDD and I-TEQ are calculated to be 0.0239 ng and 0.203 ng, respectively. The potential increases in crop plant and livestock tissue PCDD/F concentrations, and hence in human exposure, following applications of sewage sludge to agricultural land are quantified for different sludge application scenarios. The key role of PCDD/F transfer into livestock via ingestion of sludge adhered to vegetation in determining increases in human exposure is demonstrated.

Journal Article↗

PubMed1993

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.

Adipose Tissue↗

PubMed1993

The effect of heavy metals on dinitrogen fixation by Rhizobium-white clover in a range of long-term sewage sludge amended and metal-contaminated soils.

An investigation was conducted to determine whether effective strains of Rhizobium leguminosarum biovar. trifolii capable of symbiotic N2 fixation with white clover (Trifolium repens) were present in a range of metal-contaminated soils. A number of historically sewage-amended sites (including experimental, pasture grassland and arable sites) were selected and compared with highly contaminated samples from abandoned heavy metal mines. Many sites had metal concentrations above the limits established by the UK Government, based on those developed by the European Commission (EC) for sludge-amended soils. Acetylene reduction activity (ARA) was used to screen the samples for effective N2 fixation. When the host plant was indigenous to the sward, rhizobia were found in the nodules and in the soil rhizosphere at all the sites tested. They were shown to be capable of effective symbiosis and N2 fixation, even though metal concentrations greatly exceeded the soil metal limits in some cases. However, nodulation failed to occur in some cases where T. repens was not indigenous to metal-contaminated soils. This indicated either that an ineffective rhizobial population was present, or that effective cells were absent from the soil. The influence of individual metals on ARA could not be determined conclusively because of the confounding effects of soil physicochemical variability and the presence of different metals at high concentrations together in the soil. However, Cd concentrations appeared to be particularly important in determining the presence of effective ARA in soils with no indigenous clover. In contrast to previous studies, the results presented here suggest that heavy metals may have had a quantitative effect on the free-living population of rhizobia, rather than a genetic effect.

Journal Article↗

PubMed1993

The use of the cotton-strip assay to assess cellulose decomposition in heavy metal-contaminated sewage sludge-amended soils.

Cellulose decomposition in soils amended over twenty year ago with heavy metal-contaminated sewage sludges was assessed by using the cotton-strip assay. The soils of the Luddington Experiment now contain concentrations of Cu, Ni and Zn in selected plots that approximate to or exceed the statutory limits for these elements in sewage sludge-amended soils. The rates of cellulose decomposition were generally lower in the plots with elevated metal concentrations, relative to uncontaminated sludge-amended and unsludged controls. Generally, the metal-rich plots showed reductions in the time taken to reach 50% cotton-tensile-strength loss (CTSL). However, the reductions could not be consistently related to any one metal. The difference in decomposition rates between treatments was systematically reduced over the duration of a time-course experiment. A lower initial population of the appropriate decomposer community of micro-organisms may account for the observed short-term lag in decomposition rates.

Journal Article↗

PubMed1993

Bioremediation of soil contaminated with polynuclear aromatic hydrocarbons (PAHs): a review.

Polynuclear aromatic hydrocarbons (PAHs) constitute a group of priority pollutants which are present at high concentrations in the soils of many industrially contaminated sites. Criteria established for the removal or treatment or both of soils contaminated with PAHs vary widely within and between nations. The bioremediation of contaminated soils with in-situ, on-site, and bioreactor techniques is reviewed, together with the factors affecting PAH degradation. Current in-situ remediation techniques are considered ineffective for the removal of most PAHs from contaminated soil. On-site 'landforming' methods have been used successfully (and within a reasonable period of time) to degrade only those PAHs with three or fewer aromatic rings. Bioreactors have proved most effective for soil remediation, since conditions for enhanced degradation can be achieved most readily. However, bioreactors are still at the development stage, and further research is required to optimise their efficiency and economy for routine use. Degradation of the more recalcitrant high-molecular-weight PAHs is contaminated soil has not been particularly successful to date. Further research needs are identified to help develop bioremediation into a most cost-effective technology. The importance of full site assessments and treatability studies for successful application in the field is emphasised.

Journal Article↗

PubMed1993

New advances in automatic disposable rotating cartridge skin staplers.

This report describes the design, operation, and mechanical performance of Auto Suture Multifire Premium disposable skin staplers and staples in a biomechanical laboratory investigation and a clinical evaluation. The performance of this reloadable stapler has been compared with that of a new disposable skin stapler with a rotating cartridge, the Proximate RH stapler. The latter exemplifies a disposable skin stapler whose cartridge cannot be reloaded. The Auto Suture Multifire Premium disposable skin stapler has been designed so that its cartridge can be reloaded during a single surgical procedure. The most obvious advantage of this new device is that it substantially reduces the cost of skin stapling during surgery. Another unique benefit of this stapler is that it can accommodate either regular or wide staples, allowing the surgeon to use both size of staples without discarding the stapler. On the basis of this investigation, the Auto Suture Multifire Premium disposable skin stapler is recommended for skin incision and graft closure, since it provides maximal visualization of the wound as well as the staple during its formation. It delivers the staple into the skin or skin graft so that the topspan of the staple is above the skin or wound surface. In addition, the Auto Suture Multifire Premium disposable skin stapler has a prepositioning (precocking mechanism) that is controlled by the surgeon with minimal force, a mechanism which allows the stapler to hold its staple securely, even when its pointed legs extend beyond the delivery end of the stapler. The force required to form its staples is so low that the surgeon can staple repetitively without fatigue.(ABSTRACT TRUNCATED AT 250 WORDS)

Disposable Equipment↗

PubMed1992

A source inventory and budget for chlorinated dioxins and furans in the United Kingdom environment.

Polychlorinated dibenzo-p-dioxins (PCDDs) and -furans (PCDFs) are ubiquitous in the environment. This paper estimates the present UK environmental loading of PCDD/Fs in soils, vegetation, air, water and sediments. Greater than 95% of the estimated total PCDD/F loading of 5.7 t in the UK environment is present in surface soils. Annual emissions from known primary sources of PCDDs and PCDFs are estimated. The most important of these include: municipal waste incinerator stack emissions (10.9 kg sigma PCDD/F per annum); industrial (7.7 kg/year) and domestic (5.1 kg/year) combustion of coal; clinical waste incinerators (1.7 kg/year); volatilisation from chlorophenol-treated substrates (1.7 kg/year) and combustion of leaded petrol by motor vehicles (0.7 kg/year). These sources are generally easy to define and reasonably reliable national estimates can be obtained. More difficult to quantify are secondary releases from the large UK stock of pentachlorophenol (PCP) and PCP-treated products, which may represent quantitatively one of the most important sources of total PCDD/Fs to the environment. Estimates of homologue-specific emissions indicate that combustion processes represent a far more significant source of tetra and penta CDD/Fs than do chlorophenols, which in turn constitute a greater source of hepta- and octachlorinated congeners. Direct emission of PCDD/Fs into the atmosphere from combustion processes facilitates their atmospheric transport to remote locations. This, coupled with the diffuse nature of combustion processes, means that the effects of PCDD/F contamination originating from anthropogenic combustion are more widespread than those from the use and disposal of chlorophenols. Contamination from chlorophenols will be more localised, owing to the insignificance of direct atmospheric release pathways for this source. Although there is reasonable agreement between the estimated current annual flux and the present UK environmental loading of PCDDs and PCDFs, a large discrepancy exists between the sum of the annual contributions from primary sources and this annual flux. Whilst the existence of an as yet unidentified source or sources or gross underestimates of known sources cannot be excluded, it is proposed that much of this discrepancy may be accounted for by secondary releases from the use and disposal of chlorophenols and the long-range transport, continued remobilisation and subsequent redeposition of PCDDs and PCDFs already present in the environment. Despite limited evidence for a modest decline in levels of PCDDs and PCDFs in some environmental compartments over the last 20 years, the environmental persistence of these chemicals means that they will remain in the UK environment for the foreseeable future despite recent action to curb primary emissions.

Air Pollutants↗