Concentration and distribution of dioxins and related compounds in human tissues

Polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran and dioxin-like polychlorinated biphenyl concentrations in human blood, lung, liver, bile, pancreas, spleen, kidney and mesentery fat were determined to assess the concentrations and distribution of these chemicals in human tissues from 20 donors. The mean TEQ concentrations in blood, lung, liver, bile, spleen, pancreas, kidney and mesentery fat were 119, 178, 228, 50, 113, 163, 138 and 139 pg TEQ/g lipid, respectively. Parallel levels were seen in the blood, spleen, kidney and mesentery fat; in the lungs and pancreas, the levels were somewhat higher. Among the organ tissues samples, the highest concentration was observed in the liver and the lowest in the bile. Mean total-TEQ concentration of the liver was about 4.5 times higher than that of bile. Positive correlations were observed among the concentrations of dioxins in various tissues. However, the concentrations in bile were not correlated with any tissues. It is suggested that the distribution behavior of dioxin-like congeners in human tissues varies among tissues and the kinds of congeners ingested. To evaluate the relationship between the accumulation levels of dioxins and their pathophysiological significance or risk, data must be accumulated from a more extensive group of human samples.     

Electromyographic analysis of relevant muscle groups during completion of computer tasks using different computer mouse positions

Background. We analyzed muscular activity for different computer mouse positions during the completion of a timed computer task and determined whether the different mouse positions could affect muscular activity, productivity and perceived fatigue. Methods. The subjects were nine healthy young men. Two mouse positions were studied: the distal position (DP), with the forearm rested on the desk; the proximal position (PP), with only the wrist rested on the desk. The subjects performed a 16-min task in each position. Surface electromyography data were recorded for the upper back and shoulder muscles. Work productivity and muscular activity were measured for each mouse position. A visual analog scale was used to assess subjective fatigue. Results. Muscular activity was higher in muscle (m.) deltoideus (posterior) for the DP, while it was significantly higher in m. inferior infraspinatus for the PP. The visual analog scale score was significantly higher and work productivity was lower in the PP. Conclusions. We found that using a mouse in the DP rather than the PP leads to less activity of the external rotators, less perceived fatigue and more productivity. This suggests that the DP is preferable to the PP for computer work involving a mouse.     

Two-stage thermal gasification of polyolefins

Plastic pellets of polyethylene (PE), polypropylene (PP), and polystyrene (PS) were gasified in a two-stage thermal degradation process. The first stage is the conversion of polyolefins to distilled oils using a melting vessel. In the second stage, the oils from the first stage are gasified using a tubular reactor. The distilled oil yields of PE, PP, and PS in the first stage were 84, 89, 92 wt%, respectively, each at 470°C. The total gas yields of PE, PP, and PS in the second stage were 80, 74, and 6.2 wt%, respectively, each at 800°C. The main components of the product gas for PE and PP were methane and olefins such as ethene and propene. Some aromatic oils, including benzene, toluene, and xylene, were also produced as by-products. The amount of carbonaceous residue, or coke, was very low (less than 1 wt%). By dividing the process into two stages, the coking rate was considerably reduced compared with direct gasification of the polyolefins. Received: July 19, 2000 / Accepted: September 17, 2000     

Effects of tributyltin maternal and/or waterborne exposure on the embryonic development of the Manila clam, Ruditapes philippinarum

We examined the effect of tributyltin (TBT) on embryonic development of the Manila clam, Ruditapes philippinarum. In a maternal exposure test, 100 clams were exposed to TBT at measured concentrations of <0.01 (control), 0.061, 0.310, or 0.350 microg/l at 20-22 degrees C for 3 weeks, and the embryo developmental success (the ratio of normal D-larvae to all larvae) was measured. There was a significant negative correlation between embryo developmental success and TBT concentration in the female Manila clams (p < 0.001). These results indicated that TBT accumulated in the female clam decreased embryo developmental success. In a waterborne exposure test, fertilized eggs (4 h after fertilization) were exposed to TBT at measured concentrations of <0.01 (control), 0.062, 0.140, 0.320, or 0.640 microg/l for 23 h. Embryo developmental success was also significantly decreased in all TBT treatment groups compared with that in the control group. TBT accumulated in female adults and waterborne TBT clearly inhibit reproductive success of the clam.     

Ecological implications of fecal pellets produced by the Antarctic krill Euphausia superba in the Antarctic Ocean

Organic analyses and electron microscopic observations on fecal pellets produced by the Antarctic krill Euphausia superba Dana showed that krill fed on choanoflagellates, the abundant heterotrophic flagellate in the Antarctic Ocean. Two new pathways of organic materials in the Antarctic ecosystem are proposed: (1) a new food chain including non-living particulate and dissolved organics, and bacteria-choanoflagellate-krill-vertebrate, which coexists with the traditional diatom-krill-vertebrate food chain; (2) non-phytoplanktonic organic materials in surface waters are transferred into choanoflagellates and are transported to deep water as fecal pellets which are still useful as nutrition for other organisms there.