The influence of soil contamination on the concentrations of PCBs in milk in Siberia.

Although atmospheric deposition is generally the dominant pathway of PCBs into agricultural food chains, soil ingestion by livestock can be important in some cases. The relationship between PCB levels in cow's milk and in pasture soil was studied in the Irkutsk region in Siberia where an historical atmospheric source(s) of PCBs has led to widespread contamination of soil. Milk samples were collected in spring and again in autumn from 18 different farms and analyzed for PCBs. Pasture soil samples were also collected and analyzed. The PCB concentrations in both milk and soil ranged over more than an order of magnitude between the farms. A good correlation was obtained between PCB levels in autumn milk and in soil. This together with a range of other evidence suggested that ingestion of pasture soil was the dominant source of the PCB contamination in the milk. The average soil ingestion rate was estimated to be 1700 g/d, which is at the upper end of values reported in the literature. This may be due to the arid summer climate or the animal husbandry practices in Siberia.

Observations of the PCB distribution within and in-between ice, snow, ice-rafted debris, ice-interstitial water, and seawater in the Barents Sea marginal ice zone and the North Pole area.

To evaluate the two hypotheses of locally elevated exposure of persistent organic pollutants (POPs) in ice-associated microenvironments and ice as a key carrier for long-range transport of POPs to the Arctic marginal ice zone (MIZ), dissolved and particulate polychlorinated biphenyls (PCBs) were analyzed in ice, snow, ice-interstitial water (IIW), seawater in the melt layer underlying the ice, and in ice-rafted sediment (IRS) from the Barents Sea MIZ to the high Arctic in the summer of 2001. Ultra-clean sampling equipment and protocols were specially developed for this expedition, including construction of a permanent clean room facility and a stainless steel seawater intake system on the I/B ODEN as well as two mobile 370 l ice-melting systems. Similar concentrations were found in several ice-associated compartments. For instance, the concentration of one of the most abundant congeners, PCB 52, was typically on the order of 0.1-0.3 pg l(-1) in the dissolved (melted) phase of the ice, snow, IIW, and underlying seawater while its particulate organic-carbon (POC) normalized concentrations were around 1-3 ng gPOC(-1) in the ice, snow, IIW, and IRS. The solid-water distribution of PCBs in ice was well correlated with and predictable from K(ow) (ice log K(oc)-log K(ow) regressions: p<0.05, r2=0.78-0.98, n=9), indicating near-equilibrium partitioning of PCBs within each local ice system. These results do generally not evidence the existence of physical microenvironments with locally elevated POP exposures. However, there were some indications that the ice-associated system had harbored local environments with higher exposure levels earlier/before the melting/vegetative season, as a few samples had PCB concentrations elevated by factors of 5-10 relative to the typical values, and the elevated levels were predominantly found at the station where melting had putatively progressed the least. The very low PCB concentrations and absence of any significant concentration gradients, both in-between different matrices and over the Eurasian Arctic basin scale, suggest that ice is not an important long-range transport purveyor of POPs to the Arctic MIZ ecosystem.

Observer variation in interpreting radiographs of the pituitary fossa.

Observer variation in interpreting sellar radiographs in patients suspected or known to have a pituitary tumor has been examined. Two radiologists experienced in interpreting sellar radiographs examined independently, without clinical details, plain films and tomograms of the sella of 101 patients. In most, only minor changes were anticipated. Of the 93 female patients, 67 were under investigation for amenorrhea. Radiographs were examined four times, each radiologist examining each set twice. Appearances were classified as normal, doubtful or abnormal on each occasion. Overall intraobserver agreement was 76%--85%. Neither radiologist changes his opinion by more than one category, e.g. from normal to doubtful. Overall interobserver agreement was 63%--75%. Disagreement between observers concerning 11 (11%) of the patients resulted from differences of opinion about whether minor changes in sellar outline represented an abnormality or merely a normal variation. Kappa analysis suggested that much of the agreement may be ascribed to chance. Agreement rates resemble those for other clinical and radiological investigations.

Failure to prostaglandin A1 to modify renal diatrizoate uptake in experimental acute renal failure.

Acute renal failure (ARF) was induced in rats by intramuscular injection of glycerol. Forty-eight hours later prostaglandin A1 (PGA1) in a dose of 1, 5 or 25 microgram/kg bodyweight or phosphate buffer was infused intravenously over 15 min into these animals and controls. After 14 min, 125I-labeled diatrizoate was injected intravenously in a dose of 15 mg/kg bodyweight. Uptake and distribution of diatrizoate were measured one minute later in whole kidneys or kidney slices to provide indices of glomerular filtration. Diatrizoate concentrations were also measured in liver, plasma and washed red cells. Plasma volume was estimated with 125I-labeled albumin. PGA1 produced a dose-related increase in plasma diatrizoate concentration in ARF which was not accounted for by changes in uptake by the kidney, liver or red cells or by changes in plasma volume. It exceeded the relatively small increase in diatrizoate uptake which occurred in the kidney. Intrarenal distribution of diatrizoate did not change. These observations in the kidney suggest that intravenous PGA1 does not improve glomerular filtration in this model of established ARF.

Bone mass measurement using a xenon-filled multiwire proportional counter as detector.

The application of a xenon-filled multiwire proportional counter to photon absorptiometry of bone mass is described. Performance characteristics obtained from a prototype system are discussed and future developments indicated.

The effect of radiology electives on career choice at McMaster University.

Recruitment ot radiology is said to be affected by the extent to which radiologists participate in medical student teaching. At McMaster University, where radiologists make major contributions to the medical school curriculum, students appear to show little interest in radiology as a career. The characteristics, attitudes and career choices of students at McMaster who undertook elective periods in radiology between 1973 and 1976 were examined. Though students rated the elective experience very highly, none intended to become a radiologist. Half of the group wished to take up family practice, the proportion in the school as a whole being similar. This is consistent with policies of student selection and education at McMaster. Most of those choosing family practice did not change their career choice between entry to and exit from the school. Involvement of radiologists in the curriculum had no detectable positive influence on career choice.

Aging and simple cysts of the kidney.

Abdominal CT scans of 103 patients without evidence of renal disease were examined. Unsuspected simple renal cysts were demonstrated in 25 (24%). No cysts were demonstrated in patients less than 40 years old. Thereafter the number of cysts and the number of patients with cysts tended to increase with age. Cyst dimensions also increased. These observations suggest that the development of simple cysts of the kidney is related to aging.

Nephrographic density and renal diatrizoate content in experimental acute renal failure.

Reversible acute renal failure (ARF) was induced in rats by intramuscular injection of glycerol. In these animals and controls, renal concentrations of 125I-labelled sodium diatrizoate, injected intravenously in doses similar to those used clinically, were compared with the density of the nephrogram, subjectively assessed under carefully controlled conditions. Though a good statistical correlation existed between renal diatrizoate concentration and nephrographic density, individual variation was wide. At any given level of renal iodine concentration, nephrograms were judged to be denser in ARF than in controls. This was not due to differences in whole-body opacification or renal size, but was partly explained by the greater visibility of renal outlines on plain films in ARF. However, though at all doses of diatrizoate renal iodine concentrations were higher in controls, differences in nephrographic density were in general difficult to detect.

Estimation of glomerular size and number from radiographs of the kidney.

In 32 adult human kidneys obtained at necropsy, renal demensions, measured from radiographs, were correlated with the number and cross-sectional area of glomeruli, determined by point-counting and computerized image analysis. Cortical area, measured from post-mortem angiograms, was poorly correlated with glomerular area and was not significantly correlated with glomerular number per kidney. The area of the whole kidney was poorly correlated with the number of glomeruli per kidney and was not significantly correlated with glomerular area. However renal dimensions, particularly total renal area, were highly significantly correlated with the product of glomerular area and number. This may allow glomerular numbers to be estimated in life but will not assess loss of glon the ageing kidney, the number of glomeruli per unit volume increased.

Effect of rotation on radiographic dimensions of the humerus and femur.

Ten humeri and ten femora were radiographed in nine positions of longitudinal rotation. In each position total, medullary and cortical widths of the diaphyses (TW, MW, CW) were measured to assess the effect of rotation on these dimensions. The results were expressed as differences from the values in the neutral position (delta TW, delta MW, delta CW). In the humerus, medial rotation produced greater changes than lateral rotation. Though rotation in either direction increased CW, the systematic error due to medial rotation to only 5 degrees (approximately +0.0058 cm per degree) was more than double that due to lateral rotation. In the femur, lateral rotation had the greater effect, producing a marked decrease in CW (approximately -0.0072 cm per degree). Medial rotation produced only a slight increase in CW. The ratios CW/TW ("cortical index") and CA/TA ("area ratio") were calculated and expressed as differences from the values in the neutral position (delta CW/TW, delta CA/TA). Rotation affected these variables much less than the linear dimensions. Furthermore, through the variance of delta TW, delta MW and delta CA/TA increased only slightly or not at all. These results suggest that if radiographic morphometry is to be applied to the humerus and femur, these ratios rather than transverse dimensions should be used. Sequential changes in CW may be totally obscured by small rotational errors.

Loss of renal tissue in the elderly.

Eighty-eight kidneys obtained at necropsy from normotensive subjects aged over 50 years were examined histologically and by post-mortem pyelography and angiography. Moderate or severe scarring was present in 50%. Its distribution and the absence of calyceal deformity make pyelonephritic scarrig unlikely. Its extent was related to the severity of change in the renal vessels, but not to age. On pyelograms, scarring was difficult to distinguish from fetal lobation. Kidneys with the most severe histological changes in the vessels tended to show the most marked angiographic distortion, though in general the two techniques examine different parts of the renal vascular bed. Total renal area and "cortical" area, measured from the angiograms, were not significantly correlated with age, thouth both tended to be smaller in older subjects. These dimensions, particularly cortical area, were significantly correlated with vascular changes, being smallest when vessels were most markedly affected. Results suggest that the loss of renal tissue which occurs in the elderly, particularly selective loss of cortex, is more closely related to events in the renal vasculature than to age itself.

Uptake and transfer of PCDD/Fs by cattle fed naturally contaminated feedstuffs and feed contaminated as a result of sewage sludge application. 2. Nonlactating cows.

The dietary absorption and tissue distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was investigated in 4 nonlactating Simmental cows. During Phase 1 the dietary uptake and fecal excretion of these chemicals were measured over 10 days using feed containing background levels of PCDD/Fs that were primarily of atmospheric origin. Following this, two of the animals were sacrificed and samples of different fat, muscle, and organ tissues were collected. In Phase 2 the remaining two animals were fed grass silage from a field which had a history of repeated sewage sludge applications. During the last 10 days of the 27-day feeding period, the dietary uptake and fecal excretion of PCDD/Fs were again quantified, after which these two animals were also sacrificed and sampled. The dietary absorption of the PCDD/Fs in the nonlactating cows agreed well with values reported in Part I of this series for lactating cows. In the two animals sacrificed at the end of Phase 1 that were close to a contaminant steady state, the lipid-normalized concentrations were similar in almost all tissues. The exceptions were the liver, and to a lesser extent the lungs and the spleen, which had higher levels; and the degree of elevation increased with the degree of chlorination of the PCDD/Fs. During Phase 2, the animals' body burden of several of the PCDD/F congeners increased markedly. The tissue analyses indicated that the chemicals were initially sequestered primarily in the liver, from where they were redistributed to the other tissues and organs. The rate of redistribution was related to the perfusion of the organ/tissue and decreased in the order lung>spleen>kidney>muscle>fat tissue. The rate of redistribution also decreased with increasing degree of chlorination of the PCDD/F congeners. Whereas virtually all of the 1,2,3,7,8-Cl(5)DD taken up during Phase 2 had been deposited in fat tissue by the end of the 27-day feeding period, three-quarters of the Cl(8)DD was still in the liver.

The kinetics and reversibility of the partitioning of polychlorinated biphenyls between air and ryegrass.

Lolium multiflorum (ryegrass) was contaminated with technical mixtures of polychlorinated biphenyls (PCBs) via the gas phase and the subsequent elimination of the PCBs from the vegetation was studied under field conditions. There was a pronounced decrease in the concentrations of the di- through to the pentachlorinated congeners over the 240-h elimination period. For many of the congeners the elimination was nearly complete, suggesting that the partitioning of these compounds from the gas phase into ryegrass is largely reversible. The elimination followed first order kinetics. The elimination half-lives were linearly proportional to the plant/air equilibrium partition coefficients (K(PA)) of the PCB congeners and ranged from 22 h for PCBs 8 + 5 to 87 h for PCBs 84 + 101. For the hexa- through to the octachlorinated congeners no significant decrease in the concentration of the vegetation was observed during the elimination experiment. The elimination was described well using a two-resistance model of PCB desorption which indicated that elimination of the di- and trichlorinated PCBs was limited by transport within the plant itself while elimination of the higher chlorinated congeners was limited by transport from the plant surface into the atmosphere. Furthermore, the results demonstrate that if elimination of higher chlorinated PCBs from ryegrass via biological or photochemical degradation occurs, then it is very slow.

PCDDs in the water/sediment-seagrass-dugong (Dugong dugon) food chain on the Great Barrier Reef (Australia).

Polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) concentrations were measured in sediment and seagrass from five locations in or adjacent to the Great Barrier Reef Marine Park. A full spectrum of Cl5-8DDs were present in all samples and, in particular, elevated levels of Cl8DD were found. PCDFs could not be quantified in any samples. The PCDD concentrations ranged over two orders of magnitude between sites, and there was a good correlation between sediment and seagrass levels. There were large quantities of sediment present on the seagrass (20-62% on a dry wt. basis), and it was concluded that this was a primary source of the PCDDs in the seagrass samples. The PCDD levels in the seagrass samples were compared with the levels in the tissue of three dugongs stranded in the same region. The relative accumulation of the 2,3,7,8-substituted PCDD congeners in the dugongs decreased by over two orders of magnitude with increasing degree of chlorination. This was attributed to the reduced absorption of the higher chlorinated congeners in the digestive tract, a behaviour that has been observed in other mammals such as domestic cows.

A study of the influence of sewage sludge fertilization on the concentrations of PCDD/F and PCB in soil and milk.

The influence of the agricultural use of sewage sludge on the concentrations of PCBs and PCDD/Fs in soil, feed and milk was investigated on four dairy farms. Evidence of contaminant accumulation in the soil was found on both farms that fertilized with sewage sludge. The concentrations in feed and milk from one of these farms were similar to the concentrations in the matched control, while the concentrations in the samples from the second sludge user were elevated. The study demonstrates that the agricultural use of sewage sludge does under some conditions lead to higher levels of PCBs and PCDD/Fs in food products.

The influence of dietary concentration on the absorption and excretion of persistent lipophilic organic pollutants in the human intestinal tract.

The gastrointestinal exchange of polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans (PCDD/Fs) as well as hexachlorobenzene was measured in five volunteers. The dietary intake and the fecal excretion of the chemicals were quantified and the net absorption/net excretion was calculated as the difference between these two fluxes. Experiments were conducted using an elevated dietary intake and a reduced dietary intake of chemical, and the results were compared with the absorption during normal dietary intake. The net absorption varied widely with the dietary intake for those compounds which bioaccumulate in humans; high dietary intake of chemical resulted in absorption approaching 100% of intake, while low dietary intake resulted in a net excretion several times greater than the dietary intake. In contrast to net absorption, the chemical flux in the feces was largely independent of the dietary intake of chemical for a given individual. Good agreement was found between the feces/blood distribution coefficients measured in this study and in a study with contaminated workers whose blood concentrations were several orders of magnitude higher, indicating that fecal excretion of chemical is linearly proportional to the blood concentration. The results suggest that gastrointestinal exchange can be viewed as two processes operating simultaneously: absorption of contaminant from the diet, and excretion of contaminant from the body's reservoirs via the feces. By subtracting that component of the fecal flux originating from the body, the maximum dietary absorption could be calculated. This was >95% for most of the compounds, decreasing to a minimum of 50-60% for the octachlorinated dioxins and furans. The maximum dietary absorption showed a Kow dependency consistent with the two film model of gastrointestinal absorption of persistent organic chemicals.

A non-absorbable dietary fat substitute enhances elimination of persistent lipophilic contaminants in humans.

For individuals contaminated with persistent lipophilic pollutants, there is an urgent need for a therapy to enhance contaminant elimination from the body and hence reduce long term exposure. This study investigated the possibility of enhancing the excretion of native chemical via the faeces by augmenting the lipophilic properties of the faeces with the non-absorbable lipid substitute olestra. The faecal excretion of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) was measured in 3 volunteers. The excretion while eating an olestra-free diet was compared with the excretion while eating a diet supplemented wit 25 g/d of olestra. The excretion while on the olestra diet was higher by a factor of 1.5-11, depending on the compound. This resulted from higher concentrations of the contaminants in the faeces and higher excretion of faeces dry mass due to the food additive. Using 2,3,7,8-Cl4DD as an example, it was estimated that ingestion of 25 g/d of olestra would more than double the overall rate of elimination of this compound from the body. It is concluded that regular consumption of olestra may provide a therapeutic approach for reducing the body burden of persistent lipophilic contaminants.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in Great Barrier Reef (Australia) dugongs (Dugong dugon).

Fat tissue samples from dugong (Dugong dugon) carcasses stranded at three sites along the Great Barrier Reef were analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Relatively high levels of PCDDs were determined in all three dugongs. In particular OCDD, the PCDD/F congener that is usually considered the least bioavailable of all 2,3,7,8 substituted congeners, was found at levels higher than reported for other marine mammals. Tissue accumulation of PCDDs by dugongs may be a consequence of sediment and/or seagrass ingestion during feeding, microbial biotransformation of PCDD precursors in the animal's hindgut or, alternatively, the possession of a selective degradation capability for PCDFs.

PCDD/Fs in textiles--part II: transfer from clothing to human skin.

The transfer of PCDD/Fs from contaminated textiles to the outermost layers of the skin (stratum corneum) of human volunteers was measured. The experiments were conducted with cotton T-shirts containing high levels of hepta- and octachlorinated dibenzo-p-dioxins and dibenzofurans. The results indicated that there is little spatial variability in the transfer from the T-shirt to the skin surface (< factor2) and also little variability among individuals (< factor 3). The percent transfer from different cotton textiles (sigma PCDD/F: 1,900 pg/g - 281,000 pg/g) to the stratum corneum was found to be similar. The transfer from a white, unbleached polyester material was more than an order of magnitude lower, indicating that the PCDD/Fs were more tightly bound to the polyester than to the cotton. It was shown that the PCDD/Fs penetrate into deeper layers of the stratum corneum during an 8 hour exposure period. However, systemic exposure and a significant contribution of this pathway to the PCDD/F body burden is only possible if the compounds are able to overcome the penetration barrier posed by the viable epidermis.

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.