I don't know why some like Mark have such blind faith in "computer models" and object to criticism on that point, but those of us in the programming field see this result more often than not. Yet another flawed EPA study.

What speaks VOLUMES is this quote...
"Our deadline for getting this out is the end of 2003 and this software issue may impact our ability to meet that deadline," Martyak said. "We still believe strongly in the tie between the particulate matter and the health effects that it creates."

Here we see the study's sponsor admiting to holding strong beliefs. Good for him/her. But now tell me that the results of "computer models" do not "somehow" deliver what the sponsor expects. If not, like here, hey just re-work them a bit. This predilection is why double blind studies are good science and why computer models aren't. They too easily get co-opted by the modelers subconscious preferences even without trying.
They cannot be trusted.

-philw