Biomedical subjects

D Osborn

Publications and source records attributed to D Osborn.

At least 19 recordsLinked to original sources

PubMed2006

Embryo production from superovulated sheep inseminated with sex-sorted ram spermatozoa.

An experiment was undertaken to assess the fertilizing capacity of sex-sorted, frozen-thawed ram spermatozoa, artificially inseminated into superovulated ewes, and the quality and survivability of the resultant pre-sexed embryos. Synchronized (intravaginal progestagen pessary and GnRH) donors were superovulated using PMSG and repeat ovarian stimulation with FSH before insemination. Ewes (n=67) were inseminated with either 30x10(6) or 15x10(6) motile non-sorted (control) or 15x10(6) motile sex-sorted (sorted) frozen-thawed spermatozoa (control: C30 or C15; sorted: S15, respectively) and the resultant embryos transferred immediately into synchronized recipients (n=160). The percentage of transferable embryos, pregnancy rate and embryo survival were similar (P>0.05) across all treatments. Oocyte cleavage rate was higher for ewes inseminated with S15 (172/230; 74.8%; P<0.05) than for C15 (97/151; 64.2%) or C30 (89/141; 63.1%) spermatozoa. Of the lambs resulting from embryos produced with sex-sorted spermatozoa, 86/93 (92.5%) were born of the predicted sex. This study demonstrated for the first time that pre-sexed offspring derived from superovulated sheep can be produced following transfer of embryos. Furthermore, sex-sorting by flow cytometry did not compromise the in vivo fertilizing capacity of ram spermatozoa in superovulated sheep, nor did it affect the quality or survivability of the resultant embryos.

Animals↗

PubMed2006

Induction of decision trees using genetic programming for modelling ecotoxicity data: adaptive discretization of real-valued endpoints.

Recent literature has demonstrated the applicability of genetic programming to induction of decision trees for modelling toxicity endpoints. Compared with other decision tree induction techniques that are based upon recursive partitioning employing greedy searches to choose the best splitting attribute and value at each node that will necessarily miss regions of the search space, the genetic programming based approach can overcome the problem. However, the method still requires the discretization of the often continuous-valued toxicity endpoints prior to the tree induction. A novel extension of this method, YAdapt, is introduced in this work which models the original continuous endpoint by adaptively finding suitable ranges to describe the endpoints during the tree induction process, removing the need for discretization prior to tree induction and allowing the ordinal nature of the endpoint to be taken into account in the models built.

Decision Trees↗

PubMed2006

QSAR approach for mixture toxicity prediction using independent latent descriptors and fuzzy membership functions.

The principle of using a singe model to predict the toxicity of mixtures of chemicals based on the characterisation of the degrees of similarity and dissimilarity of the constituent chemicals using descriptors has been demonstrated in a previous work. The current study introduces a feature extraction technique, independent component analysis, to the method to remove the correlations and dependencies between descriptors and reduce the dimension prior to similarity and dissimilarity calculations. In addition, a goal attainment multi-objective optimisation technique is used for the determination of the fuzzy membership function parameters. For three mixtures, which include a new mixture and two previously studied mixtures that all inhibit reproduction (via different mechanisms of action) in green freshwater algae scenedesmus vacuolatus, the approach showed better or equivalent prediction performance than either concentration addition or independent action models. Unlike QSARs for pure compounds that require large collections of data, the new approach for mixtures only requires one mixture at a particular composition to determine the necessary fuzzy membership function parameter values. These values can then be used to predict the toxicity of the mixture at any other compositions. This could potentially lead to a reduction in the frequency of bioassay tests. Use of the fuzzy membership functions and parameter values obtained for one mixture when used to predict the toxicity of a completely different mixture is also tested and it is found that the approach also gives prediction results with good accuracy.

Chlorophyta↗

PubMed2005

After the Aznalcóllar mine spill: arsenic, zinc, selenium, lead and copper levels in the livers and bones of five waterfowl species.

In April 1998, a holding lagoon containing pyrite ore processing waste, failed and released 5-6 million m3 of highly polluting sludge and acidic water. Over 2650 ha of the internationally important Doñana Natural Park became contaminated, along with < 100 ha of the more pristine Doñana National Park. In order to assess the affect of the spill on waterfowl from Doñana, bone and liver samples from 124 individuals have been analysed for As, Pb, Cu, Zn and Se. Five species have been studied, from the Rallidae (rails), Anatini (dabbling ducks) and Aythyini (pochards) families. Geometric mean bone concentrations 2-3 months after the spill were in the order of Zn > Cu > Pb > Se > As, while liver concentrations were in the order of Zn > Cu > Se > Pb > As. Dry weight bone concentrations ranged from n.d-1.76 mg kg(-1) As, 109.4-247.6 mg kg(-1) Zn, 0.06-1.27 mg kg(-1) Se, n.d-134.11 mg kg(-1) Pb, and 2.18-8.92 mg kg(-1) Cu. Wet weight liver concentrations ranged from n.d-0.34 mg kg(-1) As, 29.8-220.1 mg kg(-1) Zn, 0.15-0.85 mg kg(-1) Se, n.d-3.80 mg kg(-1) Pb, and 7.30-742.96 mg kg(-1) Cu. The most important factor related to the accumulation of these metals was commonly species; however, location and sex also had important effects on liver As levels, location and age affected Cu levels, while Zn and Pb were affected by age, sex and location. Birds from Natural Park areas were found to have significantly higher levels of bone Zn, Pb and Cu, and liver As and Cu than birds from National Park areas. Female birds had higher liver As, Zn and Pb than males; whilst adults appeared to have lower bone As and Zn but higher liver Pb than chicks/juveniles. Although metal concentrations were elevated in certain individuals, in the majority of birds studied, they did not reach levels widely considered to be toxic. However, it would appear that As and Cu liver levels (which may be indicative of short-medium term pollutant exposure) were elevated in waterbirds which died in the spill contaminated Natural Park, 2-3 months after the disaster.

Accidents↗

PubMed2005

Arsenic levels in the soils and macrophytes of the 'Entremuros' after the Aznalcóllar mine spill.

In April 1998, a holding lagoon containing pyrite ore processing waste rich in arsenic, failed and released 5-6 million m(3) of highly polluting sludge and acidic water. Over 2700 ha of the internationally important Doñana National and Natural Parks were contaminated. The area of Natural Park to sustain the greatest impact was known as the Entremuros. This paper presents 0-5 cm soil monitoring data from the Entremuros, from sampling campaigns 6 and 18 months after the disaster; as well as macrophyte root, rhizome and stem data from samples taken 18 months after the spill. Results show a clear, decreasing, north-south arsenic soil pollution trend, both 6 and 18 months after the spill, and suggest a small reduction in total soil arsenic levels occurred over time; although a significant increase in extractable arsenic is also noted. The two macrophytes (Typha dominguensis and Scirpus maritimus) studied herein are not accumulating arsenic in stem parts, however, accumulation of arsenic on iron plaque on the roots of these plants may be occurring. Further work is recommended in order to determine the ecotoxicological significance of this process in relation to the avian food-chains of Doñana, and elsewhere.

Accidents↗

PubMed2005

The development, validity and reliability of a multimodality objective structured clinical examination in psychiatry.

OBJECTIVES: To evaluate the development, validity and reliability of a multimodality objective structured clinical examination (OSCE) in undergraduate psychiatry, integrating interactive face-to-face and telephone history taking and communication skills stations, videotape mental state examinations and problem-oriented written stations. METHODS: The development of the OSCE on a restricted budget is described. This study evaluates the validity and reliability of 4 15-18-station OSCEs for 128 students over 1 year. Face and content validity were assessed by a panel of clinicians and from feedback from OSCE participants. Correlations with consultant clinical 'firm grades' were performed. Interrater reliability and internal consistency (interstation reliability) were assessed using generalisability theory. RESULTS: The OSCE was feasible to conduct and had a high level of high perceived face and content validity. Consultant firm grades correlated moderately with scores on interactive stations and poorly with written and video stations. Overall reliability was moderate to good, with G-coefficients in the range 0.55-0.68 for the 4 OSCEs. CONCLUSIONS: Integrating a range of modalities into an OSCE in psychiatry appears to represent a feasible, generally valid and reliable method of examination on a restricted budget. Different types of stations appear to have different advantages and disadvantages, supporting the integration of both interactive and written components into the OSCE format.

Clinical Competence↗

PubMed2004

The distribution of arsenic in soils affected by the Aznalcóllar mine spill, SW Spain.

In April 1998, a holding lagoon containing pyrite ore processing waste, failed and released an estimated 5-6 million m(3) of metal rich sludge and acidic waters into the Rio Guadiamar, SW Spain. Over 2700 ha of the internationally important Doñana National and Natural Parks were contaminated. The sludge component of the waste contained up to 0.6% arsenic. This paper presents an extensive set of 0-5 cm soil analyses results from samples taken 6-8 months after the spill. Data are presented on pseudo-total arsenic levels in these samples, and on arsenic removed by both single batch and sequential extraction techniques. Pseudo-total levels of arsenic in the sludge ranged from 1521 to 3510 mg kg(-1), and a mean 4.4% of this was found to be extractable using 2.5% acetic acid. Soils in the Guadiamar Valley and Entremuros areas (those worst affected by the spill) were found to contain 85.4-782 mg kg(-1) and 7.1-196 mg kg(-1) pseudo-total arsenic, respectively. The mean acetic acid extractable component in these areas was 2.5% and 4.9%, respectively. Background pseudo-total arsenic levels in the soils of the area have been found to be 4.2-13.6 mg kg(-1). Rapid input of acidic waters, and the acidic nature of the sludge itself, may have caused depletion of Mg, Na and K, and to a lesser extent Mn, Ca and PO(4) in the upper 5 cm of the worst affected soils. Sequential extraction results suggest clear As-Fe associations, and possible As-Mn associations within the more soluble phases.

Journal Article↗

PubMed2003

Polychlorinated biphenyl (PCB) congener concentrations in seabirds found dead in mortality incidents around the British coast.

Livers from 121 birds killed in mortality incidents in U.K. coastal waters between 1991 and 1996 were analyzed for 16 PCB congeners (IUPAC numbers 8, 18, 28, 31, 52, 77, 101, 118, 126, 128, 138, 149, 153, 169, 170, and 180). Species analyzed were guillemot (Uria aalge), shag (Phalacrocorax arisotelis), kittiwake (Rissa tridactyla), puffin (Fratercula arctica), razorbill (Alca torda), fulmar (Fulmarus glacialis), gannet (Sula bassana), and herring gull (Larus argentatus). This is the first report of PCBs in U.K. seabird tissues to be presented since 1983. Mean concentrations of total PCBs ranged from 0.47 to 15.8 mg/kg WW, similar to concentrations reported for North Sea birds during the 1970s and 1980s and lower than those reported for the same species in the Irish Sea during the late 1960s and early 1970s. The congeners generally present in the highest concentrations were (in decreasing order) 153, 138, 180, 118, and 170. Despite the birds having similar diets, both inter- and intraspecies differences in PCB congener profile were found. In guillemots from several sites on the east coast, the dominant congener was 138, compared to guillemots from the south coast, which had the more typical congener pattern found in seabirds. Some of the differences in total PCB values could be due to different causes of death, with a subsequent effect on body lipid levels.

Animals↗

PubMed2003

19F NMR spectroscopic investigation into the absorption and metabolism of 3-trifluoromethylaniline in Eisenia veneta.

19F nuclear magnetic resonance (NMR) spectroscopy was used as a specific tool to investigate the metabolism of 3-trifluoromethylaniline (3-TFMA) in the earthworm species Eisenia veneta. Exposure was via a filter-paper contact toxicity test using five exposure levels (1000, 100, 10, 1, and 0.1 microg/cm(2)). Instant lethality was observed at the two highest levels. Worms exposed at the lower levels appeared to tolerate the compound. The 19F label of 3-TFMA allowed the uptake and metabolism of the earthworms to be monitored by 19F NMR spectroscopy. Metabolism of 3-TFMA was observed at 10 microg/cm(2) and, to a lesser extent, at 1 microg/cm(2). The possibility of 3-TFMA accumulation in specific organs was also investigated. As a simplified model, worms were cut into distinct anatomical regions (head, testes, crop, clitellum, and gut). At the two highest exposure levels, "uniform distribution" was observed. However, accumulation appeared to be proportional to the "size" of the extracted segments at the lower levels.

Absorption↗

PubMed2002

Dopamine for prevention of morbidity and mortality in term newborn infants with suspected perinatal asphyxia.

BACKGROUND: Perinatal asphyxia remains an important condition with significant mortality and long-term morbidity. Multisystem involvement including hypotension and low cardiac output is common in infants with perinatal asphyxia. Dopamine is commonly used for infants with hypotension of any etiology, with the goal of improving cardiac output and preventing its detrimental consequences. OBJECTIVES: To determine if dopamine, compared to placebo, no treatment, volume or another inotrope reduces morbidity and mortality in term newborn infants with suspected perinatal asphyxia. SEARCH STRATEGY: The standard search strategy of the Neonatal Review Group was used. Searches were conducted of the Oxford Database of Perinatal Trials, Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002), MEDLINE (1966 to March 2002), previous reviews including cross references, abstracts and conference proceedings (Perinatal Society of Australia and New Zealand 1998-2002 and Pediatric Academic Societies meetings 1998-2001). SELECTION CRITERIA: Randomised controlled trials comparing dopamine with placebo, no treatment, other inotropic agents, or volume in infants greater than 36 weeks gestation. Perinatal asphyxia could be suspected on the basis of a cord blood pH < 7.0, cord blood base excess < -16 mEq/L or 5 minute Apgar score < 6. DATA COLLECTION AND ANALYSIS: Standard methods of the Cochrane Neonatal Review Group with use of relative risk (RR), risk difference (RD) and weighted mean difference (WMD). The fixed effects model using RevMan 4.1 was used for meta-analysis. Data from individual studies were only eligible for inclusion if at least 75% of participants were followed up. MAIN RESULTS: Only one study (DiSessa 1981) was eligible. This study compared low dose dopamine at 2.5 mcg/kg/min with placebo (dextrose in water). This study enrolled 14 term infants with a 5 minute Apgar <6 and a systolic BP >=50 mmHg at a mean of 10 hours age. Seven infants only were randomised to treatment with dopamine and seven to receive placebo. No significant differences between these two groups were found for mortality or long term neurodevelopmental outcome. Length of hospitalisation was not significantly different between the two groups. No study was found that examined the effect of dopamine in infants with evidence of cardiovascular compromise, nor were any studies identified in which dopamine was compared to other inotropic agents for term infants with suspected asphyxia. REVIEWER'S CONCLUSIONS: There is currently insufficient evidence from randomised controlled trials that the use of dopamine in term infants with suspected perinatal asphyxia improves mortality or long-term neurodevelopmental outcome. The question of whether dopamine improves outcome for term infants with suspected perinatal asphyxia has not been answered. Further research is required to determine whether or not the use of dopamine improves mortality and long-term morbidity for these infants and if so, issues such as which infants, at what dose and with what co-interventions should be addressed.

Asphyxia Neonatorum↗

PubMed2002

Metabolism of 4-fluoroaniline and 4-fluorobiphenyl in the earthworm Eisenia veneta characterized by high-resolution NMR spectroscopy with directly coupled HPLC-NMR and HPLC-MS.

1. Little is known about metabolism of xenobiotics by earthworms, despite their importance in soil ecotoxicity testing. Normal earthworms and earthworms treated with antibiotics to ensure inhibition of gut microflora were exposed to two model xenobiotic compounds, 4-fluoroaniline and 4-fluorobiphenyl, to determine which metabolites were produced, and whether the pattern of metabolism was affected by the presence of microbial transformation ability. 2. (19)F-NMR spectroscopy detected the number and relative proportions of metabolites and directly coupled HPLC-(1)H-NMR spectroscopy and HPLC-MS then identified the metabolites. 3. Despite uptake, no metabolism of 4-fluorobiphenyl was observed at any stage, which appears to be a consequence of the lack of oxidative Phase I metabolic activity of the earthworms towards this substrate. In contrast, 4-fluoroaniline exhibited dose-dependent metabolism. At high doses (leading to mortality within 24 h) one predominant metabolite was observed, which was identified as the N-beta-glucoside conjugate. At lower dose levels, the predominant metabolite was the gamma-glutamyl conjugate, although the glucoside and another as yet unidentified metabolite were also detected. 4. The inhibition of gut microflora did not have any influence on metabolism. The study represents the first evidence for glucoside and glutamyl conjugation as a pathway for xenobiotic metabolism in earthworms.

Aniline Compounds↗

PubMed2002

19F-NMR and directly coupled 19F/1H-HPLC-NMR spectroscopic investigations of the metabolism of the model ecotoxin 3-trifluoromethylaniline in the earthworm species Eisenia veneta.

1. The metabolic fate of the model ecotoxin 3-trifluoromethylaniline (3-TFMA) in earthworm was studied by (19)F- and directly coupled (19)F/(1)H-HPLC-NMR spectroscopy. Earthworms of Eisenia veneta spp. were subjected to the ecotoxin during a filter papercontact toxicity test at exposure levels of 1000, 100, 10, 1 and 0.1 micro g cm(-2). A metabolic profile was obtained previously by (19)F-NMR spectroscopy and metabolites were observed at all the exposure levels. 2. Identification of metabolites in individual worm extracts at the (lethal) exposure levels of 1000 and 100 micro g cm(-2) could be achieved on-line without sample preparation by (19)F/(1)H-HPLC-NMR spectroscopy. (19)F-HPLC-NMR spectroscopy was used in the continuous-flow mode, which enabled the HPLC chromatographic retention times (t(R)) of the metabolites to be established in a single analytical step. 3. In total, three (19)F-NMR signals could be detected, of which one was identified as the parent compound. Two earlier eluting metabolites were identified to be alpha- and beta-glucoside conjugates of 3-TFMA. 4. Metabolites at the lower (sublethal) exposure levels of 10, 1 and 0.1 micro g cm(-2) escaped identification by (19)F/(1)H-HPLC-NMR spectroscopy as outlined here and will require concentration prior to analysis.

Aniline Compounds↗

PubMed2002

Which to measure, systemic or organ blood flow? Middle cerebral artery and superior vena cava flow in very preterm infants.

AIM: To describe, in very preterm babies, postnatal changes in measures of middle cerebral artery (MCA) Doppler variables. To relate these peripheral measures to echocardiographic measures of systemic blood flow and ductal shunting, and to study their relation to subsequent intraventricular haemorrhage (IVH). METHODS: 126 babies born before 30 weeks were studied with serial echocardiography and cerebral and Doppler ultrasound of the MCA at 5, 12, 24, and 48 hours of age. Echocardiographic measures included superior vena cava (SVC) flow and colour Doppler diameter of the ductal shunt. MCA Doppler measures included mean velocity, pulsatility index (PI), and estimated colour Doppler diameter. RESULTS: MCA mean velocity increased whereas the PI decreased significantly over the first 48 hours. Babies with low SVC flow had significantly lower MCA mean velocity and estimated diameter than babies with normal SVC flow. There was no difference in PI. On multivariant analysis, the significant associations with MCA mean velocity were mean blood pressure (MBP), heart rate, SVC flow, and lower calculated vascular resistance. The significant associations with PI were larger ductal diameter and lower mean MBP. The significant associations with MCA diameter were higher SVC flow and lower calculated vascular resistance. After controlling for gestation, there was a highly significant association between lowest SVC flow and subsequent IVH but no association between IVH and lowest MCA mean velocity, estimated diameter, PI, or MBP. CONCLUSIONS: These data are consistent with the speculation that SVC flow is a reflection of cerebral blood flow. Low SVC flow is more strongly associated with subsequent IVH than cerebral artery Doppler measures or MBP.

Blood Flow Velocity↗

PubMed2001

Brain proton magnetic resonance spectroscopy in children exposed to methamphetamine in utero.

OBJECTIVE: To examine the possible neurotoxic effects of prenatal methamphetamine exposure on the developing brain using 1H-MRS. METHODS: Methamphetamine-exposed children (n = 12) and age-matched unexposed control subjects (n = 14) were evaluated with MRI, localized 1H-MRS, and a Child Behavior Checklist. Metabolite concentrations of N-acetyl-containing compounds (NA), total creatine (Cr), choline-containing compounds, myoinositol, and glutamate + glutamine were measured in the frontal white matter and striatum. RESULTS: Despite an absence of visible structural abnormalities in either group, children exposed to methamphetamine in utero had higher [Cr] (+10%, p = 0.02) in the striatum. [NA], primarily a measure of N-acetylaspartate, was normal in both regions, which suggests no significant neuronal loss or damage in the two brain regions examined. There were no differences in reported behavior problems among the methamphetamine-exposed children relative to the unexposed group. CONCLUSIONS: The authors found increased [Cr] in the striatum with relatively normal [NA] in children exposed to methamphetamine. These findings suggest an abnormality in energy metabolism in the brains of children exposed to methamphetamine in utero.

Brain↗

PubMed2001

An NMR-based metabonomic approach to the investigation of coelomic fluid biochemistry in earthworms under toxic stress.

The endogenous metabolites of the coelomic fluid of the earthworm Eisenia veneta were characterised using high-resolution one-dimensional and two-dimensional 1H nuclear magnetic resonance spectroscopy. Signals from common organic acids, such as acetate, fumarate, malonate, malate, formate, and succinate, were identified together with adenosine and nicotinamide mononucleotide. The potential use of this information as a baseline dataset for future toxicological or physiological studies was demonstrated by a metabonomic analysis: a series of earthworms were dosed with the model compound 3-fluoro-4-nitrophenol, and toxic effects followed by multivariate analysis of the spectral data of the coelomic fluid. Relative concentrations of acetate and malonate were decreased in the dosed worms compared to the controls.

Acetates↗

PubMed2000

The initial pathogenesis of cadmium induced renal toxicity.

The novel application of magic angle spinning 1H NMR spectroscopy, coupled with pattern recognition techniques, has identified biochemical changes in lipid and glutamate metabolism that precede classical nephrotoxicity. These changes occurred in the bank vole (Clethrionomys glareolus) after chronic dosing, at a low level of exposure and at a renal Cd(2+) concentration (8.4 microgram/g dry wt) that was nearly two orders of magnitude below the WHO critical organ concentration (200 microg/g wet wt). These early stage effects of Cd(2+) on the biochemistry of renal tissue may reflect adaptation mechanisms to the toxic insult or the preliminary stages of the toxicological cascade.

Acidosis, Renal Tubular↗

PubMed2000

Chlorobenzenes in rivers draining industrial catchments

Eleven chlorobenzenes (out of a total of 12 in the congener series) were monitored weekly on four industrialized rivers (Aire, Calder, Don and Trent) of the Southern Humber Catchment in whole water samples. 1,2- and 1,4-dichlorobenzene were present at relatively high levels on both the Aire and Calder, having mean concentrations of approximately 30 ng/l. They were both at lower concentrations on the Don and Trent, although the 1,4-isomer dominated. All other chlorobenzenes monitored were routinely found on all the rivers, with the exception of hexachlorobenzene, which was only regularly detected on the Trent. Again, the rivers fell into two classes with respect to their total chlorobenzene concentrations, with the Aire and Calder being more polluted. The higher levels of chlorobenzenes (excluding hexachlorobenzene which was used widely as a agricultural pesticide) on the Aire and Calder, and the dominance of the 1,4-dichlorobenzene congener (accounting for 60-70% of sigma chlorobenzenes) on the Don and Trent, indicated that the Aire and Calder were predominately contaminated with chlorobenzenes through industrial sources, while the Don and Trent were mainly contaminated through domestic sources (1,4-dichlorobenzene is widely used as a toilet deodorant). 1,4-Dichlorobenzene dominated flux, with the Aire, Don and Trent exporting 52.5 kg/year into the Humber estuary, followed by the 1,2-dichlorobenzene at 38.8 kg/year. Sigma chlorobenzenes exported to the Humber was 133 kg/year. This is the first study to calculate chlorobenzene fluxes to the North Sea from a UK catchment.

Journal Article↗

PubMed2000

Spatial and temporal regulation of the pesticide dieldrin within industrial catchments

The river catchments of south Yorkshire support a very high density of wool processing industries. Dieldrin was once used as a moth proofing agent, as a sheep dip, and as a pesticide to protect wool fleeces during storage and transport, all of which caused pollution of these catchments due to textile processing. Weekly sampling of four of these rivers revealed two classes of dieldrin contamination: the Aire and Calder (the rivers which support very high concentrations of wool processing industries) had higher concentrations (averaging approximately 3 ng/l) than the Don and Trent (approximately 1 ng/l). The average flux of dieldrin from these rivers into the Humber estuary was 9.8 g/day, with the Aire (of which the Calder is a tributary) and the Trent contributing almost equally, with a smaller contribution from the Don. The Trent has the highest average flow, explaining its large contribution to dieldrin flux. Less detailed sampling of rivers from the north Humber catchment which drain predominantly rural areas had dieldrin concentrations similar to the heavily industrialized southern catchment rivers. This suggests that dieldrin from agronomic and domestic usage may be more persistent than the pollution caused by textile processing industries. Evidence is presented to suggest that the principle dieldrin sources to the Humber catchments are sewage treatment plants, and that the dieldrin sources are in rapid equilibrium with the water column.

Journal Article↗