An investigation of factors contributing to styrene and styrene-7,8-oxide exposures in the reinforced-plastics industry.
During the manufacturing of reinforced plastics, large amounts of styrene and trace quantities of styrene-7,8-oxide (SO) are released. Since previous work suggests that inhalation of even small amounts of SO might be an important health risk, we investigated several possible factors contributing to styrene and SO exposure during the manufacture of reinforced plastics. Factors related to job type, worker and the type and quantity of styrene-containing resins were investigated using mixed-effects multiple linear regression models. Overall, SO exposure levels were positively correlated with styrene exposure levels. However, this correlation was statistically significant only among hand laminators who had the highest exposures to both styrene and SO. An important factor for predicting both styrene and SO concentrations was the type of resin used, while the quantity of resin consumed was predictive of styrene but not of SO exposure. Since So exposure appears to be associated with factors other than coexposure to styrene, more effort should be placed on investigating emissions of SO per se. The type of mixed-models regression analysis employed in this study can be used for clarifying the underlying patterns for exposures to styrene and SO as well as for evaluating preventive measures. (+info)
Determinants of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment.
In a lumber mill in the northern inland region of British Columbia, Canada, we measured inhalable particulate, resin acid, and monoterpene exposures, and estimated wood dust exposures. Potential determinants of exposure were documented concurrently, including weather conditions, tree species, wood conditions, jobs, tasks, equipment used, and certain control measures. Over 220 personal samples were taken for each contaminant. Geometric mean concentrations were 0.98 mg/m3 for inhalable particulate, 0.49 mg/m3 for estimated wood dust, 8.04 micrograms/m3 for total resin acids, and 1.11 mg/m3 for total monoterpenes. Multiple regression models for all contaminants indicated that spruce and pine produced higher exposures than alpine fir or mixed tree species, cleaning up sawdust increased exposures, and personnel enclosure was an effective means of reducing exposures. Sawing wood in the primary breakdown areas of the mill was the main contributor to monoterpene exposures, so exposures were highest for the barker operator, the head rig operator, the canter operator, the board edgers, and a roving utility worker in the sawmill, and lowest in the planer mills (after kiln drying of the lumber) and yard. Cleaning up sawdust, planing kiln-dried lumber, and driving mobile equipment in the yard substantially increased exposures to both inhalable particulate and estimated wood dust. Jobs at the front end of the sawmill where primary breakdown of the logs takes place had lower exposures. Resin acid exposures followed a similar pattern, except that yard driving jobs did not increase exposures. (+info)
An easy cell-free protein synthesis system dependent on the addition of crude Escherichia coli tRNA.
The protein-synthesizing S30 extract of Escherichia coli contains tRNA, which limits its applications in cell-free protein synthesis. Here, we show that at least Arg- and Ser-acceptor activities can be removed from a standard S30 extract by treatment with an immobilized RNase A resin. This RNase-treated extract exhibits no protein synthesis activity, but regains it when supplied with crude E. coli tRNA and a small amount of human placental RNase inhibitor. The protein synthesis is dependent on the addition of tRNA in the presence of the RNase inhibitor. Chloramphenicol acetyltransferase was synthesized with this system and found to be active. (+info)
A study on dust emission, particle size distribution and formaldehyde concentration during machining of medium density fibreboard.
A study to characterise the quantity, particle size distribution and morphology of dust created during the machining of MDF was carried out. Four different types of MDF boards were included in this study, including a 'zero-formaldehyde' board that contains isocyanate-based resin, rather than urea-formaldehyde resin. In addition, natural softwood (pine) and natural hardwood (oak) were included in the study, for comparison with MDF. The results show that in general, the dust generated by machining MDF is comparable in terms of particle size distribution and morphology with the dust generated by similarly machining hardwood or softwood. The quantity of dust generated during sanding is higher for sanding MDF compared with sanding either hardwood or softwood. However, for sawing there is no significant difference between MDF and natural woods, in terms of the quantity of dust generated. Free formaldehyde in the air was less than 0.17mg m(-3) during machining of the Class B (higher formaldehyde potential) MDF board. There was no measurable isocyanate in the dust generated from the boards. (+info)
Apparent contradiction: psychrotolerant bacteria from hydrocarbon-contaminated arctic tundra soils that degrade diterpenoids synthesized by trees.
Resin acids are tricyclic terpenoids occurring naturally in trees. We investigated the occurrence of resin acid-degrading bacteria on the Arctic tundra near the northern coast of Ellesmere Island (82 degrees N, 62 degrees W). According to most-probable-number assays, resin acid degraders were abundant (10(3) to 10(4) propagules/g of soil) in hydrocarbon-contaminated soils, but they were undetectable (<3 propagules/g of soil) in pristine soils from the nearby tundra. Plate counts indicated that the contaminated and the pristine soils had similar populations of heterotrophs (10(6) to 10(7) propagules/g of soil). Eleven resin acid-degrading bacteria belonging to four phylogenetically distinct groups were enriched and isolated from the contaminated soils, and representative isolates of each group were further characterized. Strains DhA-91, IpA-92, and IpA-93 are members of the genus Pseudomonas. Strain DhA-95 is a member of the genus Sphingomonas. All four strains are psychrotolerant, with growth temperature ranges of 4 degrees C to 30 degrees C (DhA-91 and DhA-95) or 4 degrees C to 22 degrees C (IpA-92 and IpA-93) and with optimum temperatures of 15 to 22 degrees C. Strains DhA-91 and DhA-95 grew on the abietanes, dehydroabietic and abietic acids, but not on the pimaranes, isopimaric and pimaric acids. Strains IpA-92 and IpA-93 grew on the pimaranes but not the abietanes. All four strains grew on either aliphatic or aromatic hydrocarbons, which is unusual for described resin acid degraders. Eleven mesophilic resin acid degraders did not use hydrocarbons, with the exception of two Mycobacterium sp. strains that used aliphatic hydrocarbons. We conclude that hydrocarbon contamination in Arctic tundra soil indirectly selected for resin acid degraders, selecting for hydrocarbon degraders that coincidentally use resin acids. Psychrotolerant resin acid degraders are likely important in the global carbon cycle and may have applications in biotreatment of pulp and paper mill effluents. (+info)
Bacterial biodegradation of extractives and patterns of bordered pit membrane attack in pine wood.
Wood extractives, commonly referred to as pitch, cause major problems in the manufacturing of pulp and paper. Treatment of nonsterile southern yellow pine chips for 14 days with Pseudomonas fluorescens, Pseudomonas sp., Xanthomonas campestris, and Serratia marcescens reduced wood extractives by as much as 40%. Control treatments receiving only water lost 11% of extractives due to the growth of naturally occurring microorganisms. Control treatments were visually discolored after the 14-day incubation, whereas bacterium-treated wood chips were free of dark staining. Investigations using P. fluorescens NRRL B21432 showed that all individual resin and fatty acid components of the pine wood extractives were substantially reduced. Micromorphological observations showed that bacteria were able to colonize resin canals, ray parenchyma cells, and tracheids. Tracheid pit membranes within bordered pit chambers were degraded after treatment with P. fluorescens NRRL B21432. P. fluorescens and the other bacteria tested appear to have the potential for biological processing to substantially reduce wood extractives in pine wood chips prior to the paper making process so that problems associated with pitch in pulp mills can be controlled. (+info)
Automated solid-phase synthesis of oligosaccharides.
Traditionally, access to structurally defined complex carbohydrates has been very laborious. Although recent advancements in solid-phase synthesis have made the construction of complex oligosaccharides less tedious, a high level of technical expertise is still necessary to obtain the desired structures. We describe the automated chemical synthesis of several oligosaccharides on a solid-phase synthesizer. A branched dodecasaccharide was synthesized through the use of glycosyl phosphate building blocks and an octenediol functionalized resin. The target oligosaccharide was readily obtained after cleavage from the solid support. Access to certain complex oligosaccharides now has become feasible in a fashion much like the construction of oligopeptides and oligonucleotides. (+info)
Cloning and analysis of valerophenone synthase gene expressed specifically in lupulin gland of hop (Humulus lupulus L.).
Resin and essential oil derived from hop (Humulus lupulus L.) cones are very important compounds for beer brewing, and they specifically accumulate in the lupulin gland of hop cones. In order to identify the genes responsible for the biosynthetic pathway of these compounds and use the identified genes for hop breeding using Marker Assisted Selection and transformation techniques, genes expressed specifically in the lupulin gland were cloned and sequenced. One of them was suggested to be similar to the chalcone synthase gene from the DNA sequence. The translation product of the gene had the activity of valerophenone synthase, which catalyzes a part of the synthesis reaction of alpha-acid and beta-acid. Northern analysis showed that the valerophenone synthase gene seemed to be expressed specifically in the lupulin gland. (+info)