Heat-treated timber: potentially toxic byproducts presence and extent of wood cell wall degradation

Wood which underwent a relatively mild thermal treatment according to a one -step process leading to improved dimensional stability and improved timber performance was extracted with organic solvents to determine the presence of potentially toxic compounds produced by the thermal treatment. The extra ctives were examined by GC-Mass spectrometry as well as by C-13 NMR to dete rmine which type of loose chemical compounds were produced by the thermal t reatment. The formation of some toxic polynuclear aromatic hydrocarbons der ivatives of phenantrene as well as other classes of polyaromatics compounds was detected. It is most likely that the presence of all such compounds co ntributes, perhaps to a relatively substantial extent, to the reported resi stance of heat treated timber to fungal and other biological attack. Other allegedly nontoxic compounds due to wood constituents degradation were also found, mainly the by-products of lignin pyrolysis. The extent of toxic and non-toxic compounds in the heat treated wood were not quantified, but it c an be stated that their proportion appears to be quite small. The lack of q uantification of the concentration of these products does not allow to asce rtain if the final product is toxic or not, and to what extent. Nonetheless , the amount of polynuclear aromatic hydrocarbon-type derivatives should be quantified and related to the type of heat treatment process undertaken be fore assigning to this type of wood treatment a completely clean health saf ety label.