Since an association was only found with green dust, it is more likely to be related to agents, such as resin acids or monoterpenes, which are present at elevated levels during pine processing, particularly in areas in which fresh wood is sawn [28]. These agents may either be allergenic themselves following oxidation [29] or possibly act as adjuvants, increasing the risk of becoming allergic to other agents. Microbial agents present in the sapwood of fresh pine logs may also play a role [30].