Filtration elements on most mid-priced dust collectors are bags. The problem withs bags are threefold. First, bags are usually rated at 1 micron or more. Fine dust, the size of particles that could cause respiratory problems over the long term, is usually smaller at around 0.5 microns. Second, bags only have about 25-35 square feet of surface area for filtration which isn't a lot and the bags themselves are not easy to clean. Third, the effectivity of a bag (1 micron) does not comply with any industry standard. Therefore, any bag can be claimed as 1 micron if the bag is first clogged up to perform the test. I'm not saying this is the case with Delta or any specific mfg. It's just a possibility as no mfg publishes their testing criteria.
In this video, I'll be replacing the OEM 1 micron bag on my Delta 50-760 with a 0.5 micron pleated filter element with 100 sq ft of filtration surface area. It's housed in a metal mesh, cleanable by blowing compressed area while installed and will last the lifetime of the dust collector.