here is neat infographic by vinsnaturel.fr stating the maximum amount of total so2 allowed in wine according to various categories:
conventionnel = conventional
bio = organic
biodynamie = biodynamic certified demeter (strictest of all)
naturel = as per the natural wine association (http://bit.ly/1zy4amy)
s.a.i.n.s = "healthy" in french for those wine makers who add nothing at all (http://bit.ly/1zy4hyL)
a very important point must be specified however. i find this type of chart a little misleading in some way. because it sort of implies that if a winery is not certified "organic" or biodynamic" that it automatically makes wine as per the "conventional" way & therefore used all kinds of additives & a total so2 levels between 150 & 200. this is far from the truth.
in fact, a study (peterson 2000 -http://bit.ly/1CSsxtk) has shown that the average amount of total so2 in american wines tested in 1999 was 64 mg/l with only 4% of those tested above 150 mg/l. this is well within the biodynamic requirements.
to put that in further perspective, another study has shown that healthy individuals can consume 400 mg of so2 per day for a few weeks without adverse effects (hotzel 1969 - http://1.usa.gov/1CStu4H)
many winemakers friends, who are not certified in any way & are recognized as some of the best in their category without calling themselves "natural" or "authentic", have told me over & over that they use about 40-55 mg total so2 in average.
this is why i feel the issue of "no so2" wine must be taken seriously & also critically...