Causation & 9/11 Dust

The NYT has a front-page story today about the problems of factual causation in 9/11-related lawsuits, in particular addressing the potential toxicity of the dust:

The question that arises in all these cases is straightforward: Can a link between the dust and disease be proved with scientific certainty? The answer is anything but simple.

“Certainty is a word we always dance around,” said Joseph Graziano, associate dean for research at the Mailman School of Public Health at Columbia University. For him, searching for the cause of disease is like developing film. “At first you see a faint image of what the real picture is,” Dr. Graziano said, “and then, over time, you see it with much more clarity. In these relatively early times, the image is still faint.”