What needs to be factored is your total environmental exposure.
I was involved in an US-EPA, CAL-EPA turf conflict on establishing new exposure levels for TCE- http://en.wikipedia.org/wiki/Trichloroethylene - on a site where I was just starting the buildout of a 23 acre high tech corporate campus in Silicone Valley. 25 years earlier, the property had been the Siemens computer chip manufacturing site, and an underground TCE tank, a common solvent used in computer chip production, dry cleaning, aircraft fuselage cleaning, etc, had leaked into the ground during that period. The due diligence on the site during escrow had noted the spill and a previous engineering study had verified “safe” exposure levels within the US-EPA limits - when CAL-EPA suddenly proposed that TCE exposure limits be reduced in half of the current acceptable limit.
So we needed to retest the site to verify we met the new lower exposure limits to meet the compliance level, and more importantly to verify our employees would be safe working there. So I hired two of the best environmental engineering firms specializing in air quality to conduct independent exposure air monitoring studies to develop the required data to make a go/no decision on the project.
Ok, now the point to this long windup - turned out the exposure levels were well below the new proposed limits, and far less harmful then the air we were breathing every day just being outside. Over 50 different carcinogenic toxins were identified in measurable quantities within the 24/7 outside air sampling we were comparing to the inside sampling…worse in the mix? DIESEL EXHAUST…high levels of all the crap that comes out of the millions of diesel engines used in everything from pick-ups to semi’s to buses to earth movers. Unregulated, cancer causing free floating radicals streaming out black death from 4" exhaust pipes. Both engineering firms stated in their separated presentations, that if every other carcinogenic chemical could be removed from the air, just the diesel exhaust levels alone represents a guaranteed percentage of cancers per 100,000 folks. Combined with all the rest, carcinogenic soup. And per the testing companies, the outside air results in Silicone Valley were not anomalies, they were actually fairly normal for the average urban area across the nation and much less then industrial manufacturing areas.
So the real problem isn’t just what you’re exposed to in the glassing bay, it’s that exposure becoming a multiplier to the other carcinogens you’re exposed to 24/7. Live in an low wind, land locked urban area, the overall exposure is greater. Live on a wind washed coast, obviously less.
However, there is a good reason why the VOG in HI affects so many folks health when it’s bad …it’s composition is similar to diesel exhaust, though contains far less carcinogenics.
bottom line - we’re exposed to carcinogens in our food, in our air, throw away water bottles, etc etc…so when in the glassing bays, why not use the best protection you can to decrease the multiplier effect…?