Development of threshold values for boron and fluoride in non-soil contact applications

Boron and fluoride are two exam-ples of water-diffusible compounds that are primarily employed where their abil-ity to diffuse through water in wood can be used to deliver chemicals into wood thatnormally resists traditionalpreserva-tive treatment using pressure processes. As such, these chemicals are excellent candidates for limiting fungal attack in the heartwood of species that are resis-tant to conventional preservative treat-ment (Cockcroft and Levy 1973; Becker 1973,1976) Boron has long been used in dip/diffusion processes for treatment of building framing topreventbeetleattack, while fluoride has been used to treat wooden windows and door frames (Becker 1976). In addition, both chemi-cals are used for remedial treatment of woodthat isdecaying inservice (Paneke