Microparticles containing an ultraviolet light absorbing polymer and 3-iodo-2-propynyl butylcarbamate (“IPBC”) resist discoloration by sunlight and other ultraviolet light sources. Methods for preparing the microparticles produce polymer-shielded, formaldehyde-free IPBC formulations which resist discoloration and leaching, and are especially useful in water-based applications. The microparticles include a polymer that absorbs light over a range of ultraviolet wavelengths associated with IPBC discoloration. The microparticles may be utilized in paints, stains, stuccoes, adhesives, and plastics, for example.