Three mechanisms are considered: 1) growth by the scavenging and subsequent aqueous phase oxidation of atmospheric SO2, 2) growth by coagulation, and 3) growth by scavenging of atmospheric sulfuric acid. The first two mechanisms are too slow to represent a significant source of CCN, scavenging of sulfuric acid can be an effective mechanism for transforming tiny sulfuric acid particles into CCN provided the concentration of preexisting CCN is less than some critical concentration. With ambient SO2 concentrations of about 30 parts per trillion by volume (pptv), this critical concentration is quite low (that is, about 1 cm-3). However, under conditions with enhanced SO2 the value of this critical concentration reach a level of about 10 cm-3 when SO2 is equal to 100 pptv. Coupling between dimethyl sulfide (DMS) emissions and CCN production in the marine boundary layer can only exist when the existing CCN concentrations at a specific locale fall below this critical concentration. -from Authors