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Abstract
Formaldehyde (HCHO) is classified as a "probable human carcinogen" under condition of unusually high or prolonged exposure. The objective of this study was to measure formaldehyde concentration in the air surrounding different woodworking places during machining of board-like materials. The research results have shown that formaldehyde concentrations in the observed furniture factory and carpentry do not exceed the allowed limit values of 0.6 mg/m(3). The highest formaldehyde concentration was measured in the furniture shop as a consequence of indoor air conditions: high temperature, small volume and low indirect air velocity. The formaldehyde concentration in different woodworking rooms is not affected by indoor air dustiness.
Six kinds of curing agents were selected to research the effect of curing agent on the curing behaviors of the urea-formaldehyde resin which was synthesized under initial weak acidity condition. The curing behaviors investigated here include curing rate, pot life, bonding strength and formaldehyde emission of the UF resin. The results showed that when hydrogen peroxide was used as curing agent in the one-component curing system, pot life of the UF resin was the longest and curing speed of the ammonium chloride is the highest. When the mass fraction of hydrogen peroxide is 5% in the UF resin, the resin bonded material has the lowest formaldehyde emission and biggest bonding strength. When using the multi-component curing system which contained polyvinyl alcohol ester, ammonium dihydrogen phosphate, aluminum chloride, citric and urea, the UF resin had the longest pot life. When the multi-component curing agent was composed of aluminum chloride, aluminum sulfate and urea, the resin condensate had the lowest formaldehyde emission and curing temperature.
To better understand where, when, and how to control occupational exposures, it is vital that hygienists understand the factors that contribute to elevated or reduced exposure levels. Over the last two decades a burgeoning literature examining the determinants of exposure has developed, yet to date the methods used in this regard have rarely been summarized in texts or elsewhere. The purpose of this article is to provide an overview of the techniques used to study the predictors of workplace exposures. Both experimental and observational studies are examined, and the advantages and limitations of each are discussed. Fundamental study design features are reviewed. These include the selection and measurement of factors potentially related to exposure, as well as the measurement of exposure itself. Decisions reached by investigators in selecting the number of sites and workers, the number of repeated observations per worker, and the duration of sampling are discussed. Also examined are issues that commonly arise in the course of data analysis of exposure determinants. These include transformation of exposure variables, correlation of predictor variables, empirical model building, and interpretation of results. Finally, methods employed to evaluate the validity of findings are summarized.
Neuere epidemiologische Studien ergaben eindeutig, daß das Risiko einer Nasenkrebserkrankung (Adenokrazinom) bei holzstaubexponierten Personen vor allem mit der Tätigkeit im Bereich des Schreinerhandwerks assoziiert ist. Um nähere Hinweise auf die für diese Berufsgruppe spezifische kanzerogene Noxe zu erhalten, wurden im Rahmen einer Literaturstudie die in der Vergangenheit im Zusammenhang mit der Holzbe- und Holzverarbeitung verwendeten Fremdstoffe (Hilfs-, Begleit-, Arbeitsstoffe) zusammengestellt und hinsichtlich einer ursächlichen Beteiligung an den aufgetretenen Nasenkrebsfällen beurteilt. In zahlreichen Leimen, Klebern, Lacken, Polituren, Füll- und Farbstoffen sowie in Holzschutzmitteln finden sich Substanzen, die nachgewiesenermaßen krebserzeugend sind oder im Verdacht stehen, ein krebserzeugendes Potential zu besitzen (aromatische Amine, Arsensalze, Benzol, Chromate, Dichlorethen/-ethan, Di-/Tetrachlormethan, Dioxan, Dioxin, Formaldehyd, Steinkohlenteer bzw.-teeröl, Trichlorethen). Aufgrund arbeitsmedizinischer, berufsspezifischer und zeitlicher Einschränkungen können diese Substanzen—mit Ausnahme der Chrom-VI-Salze—nicht mit dem Auftreten von Adenokarzinomen der Nase bei handwerklich tätigen Schreinern in einen kausalen Zusammenhang gebracht werden. Belastungen mit Chromatstäuben bzw. hochgradig chromatbelasteten Holzstäuben stellen eine für die Risikogruppe der handwerklichen Schreiner und einiger naher verwandter Berufe/Tätigkeiten spezifische kanzerogene Noxe dar. Laut arbeitsmedizinischer Literatur verursachen Chromate bösartige Tumoren der Bronchien und Nase, wobei u.a. auch Adenokarzinome beschrieben werden. Der mögliche Zusammenhang zwischen Chromatexpositioin und Nasenkrebs bei Holzhandwerkern ist Gegenstand einer folgenden Publikation.
Since 1985 dust particles from beech and oak wood have been classified by the Senate Commission of the German Research Council (DFG) as being working materials which are definitely carcinogenic to humans. All other wood dusts, including those from softwoods, are classified as being materials with reasonable suspicion of carcinogenic potential. The carcinogenic principle of action remains unclear despite the partial findings of new studies. The contamination of wood dust with non-genuine substances, like heavy metals, is one of a number of possible triggering principles.
This study examines wood dust collected from 33 German wood processing companies with regard to the concentration of dust in the air and its contamination with chromium, copper and boron. The machining of wood treated with preservatives occurred more often than had been expected. Other sources of wood dust contamination, apart from wood preservatives, have been identified. Woodworkers are exposed to higher levels of chromium, copper and boron than the average citizen, but these levels are far from the threshold values. The level of exposure to heavy metals seems unlikely to be the sole carcinogenic principle of action.
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.