Steve and Tom, Following the NY/NJ Harbor project presentation at the last GLBTS meeting and again after talking to Steve a few weeks ago, I have been looking to see what information I can find on emissions of PAH or b(a)p from creosote treated wood. The NY/NJ harbor project had listed this as one of the most important sources identified in their work. As you know, our emissions group has been completing a revision to their b(a)p inventory and a report summarizing the outcomes. The only significant source of information on this that I've been able to turn up is the attached article a group in Switzerland published in 2000. While there is a large amount of uncertainly in how they've inventoried this source, they've done us the great favor of producing some actual emission factors and emission estimates. My guess is that this is the work that the NY/NJ harbor estimate was based on. An important thing to point out is that while the PAH emissions from the railroad ties studied appears to be quite large, this is primarily lower weight PAH compounds. Their results show that the 4-to-6 ring PAH (i.e., including b(a)p) are emitted in much lower quantities. Their analysis of creosote shows that benzo(a)pyrene is less than 0.1% of the total PAH content. In addition, their results of testing new and aged wood show that the heavy PAHs like b(a)p are greatly enriched in the outer layers, suggesting they volatilize at a much lesser rate. While they don't give an actual emission estimate for b(a)p, it must be at least 3 orders of magnitude and probably even lower than the 139 tonnes they estimate for 2&3 ring PAHs. There are some other factors to consider, such as that the Great Lakes region likely has more railroad ties than Switzerland and that there may be some other creosote-treated wood products to consider. However, it appears that, at most, this category might amount to a few percent of the current b(a)p inventory and not the gaping hole of missing emissions data that a brief comparison with the NY/NJ harbor results might suggest. None of this negates the findings of that study; it's just a matter of distinguishing PAH from b(a)p. The absence of creosote treated wood emissions from our inventory is a bigger factor for the lighter PAH than for b(a)p and may be something we want to consider looking at further in the future. Best regards, Jon ______________________ Jon Dettling Great Lakes Commission 734-971-9135 dettling@glc.org
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Kohler2000EST.pdf
Description: Adobe PDF document