I wouldn't want to be a zealot on the topic Phil, and it seems likely that reduced exposure should lessen the risk. Against that though there's a long history of our underestimating the effects of environmental health factors.
It doesn't necessarily take a lot of dust to cause problems either - I know for example that in my own case my sensitivity to dust started following a period of about seven years of seemingly innocent hobby building of model aircraft from balsa wood. I did a lot of hand block sanding of parts to fit using a technique much like a shooting board during that time.
I do agree that some respectable (statistically as credible as is reasonably possible) investigation of the recorded incidence of problems and stating of what it is would be useful. Not because it seems like it needs proving that wood dust is harmful (national health and safety bodies the world over have already pretty much standardised on the 1 - 5mg/m3 TLV range limit for industry, and there presumably is a clear basis for this, and the US ACGIH for example seems pretty clear on it too), but because perhaps reduced exposure is less of an issue.
How much less is open to question - it's pretty clear from this forum that there's rather more than a few of us older guys that have experienced issues relating to wood dust. Actually possibly quite a high proportion of those posting it seems, and quite a proportion of those that I know in the business here too that might not be regarded as ill but boy do they tend to wheeze a lot. There's of course too always the woodworking equivalent of your mythical grandmother about who smoked like a chimney all her life, sank a large whisky every night and is still flying at 90.
'Proof' Phil I think is a mythical beast that's never truly found on stuff like this, and ends up becoming a football to be kicked around by the interested parties. It tends to entail the presumption of innocence until proven guilty, and the tragedy of that approach is that it tends to be that (a) by the time the risk is proven to the standard demanded by law it's far too late for many, and (b) the bigger vested interests have in other fields a long established history of weighing in to buy or use bad science to muddy the waters and greatly delay any such eventuality.
Common sense suggests taking a careful look, but where a significant risk seems likely erring on the side of caution until better data is available. i.e. the law tends to create a scenario where the objectors have to 'prove' a problem, when in practice the onus should surely be on the sponsors of potentially dangerous processes and technologies to prove (or at least demonstrate to an acceptably high level of assurance) their safety.
It'd be unfortunate should any dust systems project bog down through politically correct or mistaken chasing of will of the wisps.
The other issue you raise is the question of which solutions work, and which don't. As above it seems rational enough that with effective hooding its likely that smaller systems can if optimised (short and free flowing connections etc) and used on small machines can do a good job. The task here is clearly to table cost effective solutions that work - so none should be excluded on ideological grounds. One big caution in that regard though is that one of the big benefits of high CFM and pressure capable systems is that they handle bigger machines much better, and are much less sensitive to loss of performance through issues like dirty filters, less than perfect machine hoods, restrictions in the system, awkward to shield cuts and so on. It's surely more advisable that DIY woodworkers are steered towards equipment that's as tolerant of less than ideal installations as is possible....
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Originally Posted by Michael W. Clark
). For instance you could vary the material size and CFM independently for a couple of data sets of each you could do some moderately interesting extrapolated curves for the intermediate points.