Most liquid wall paints today are waterborne. When used in paints, however, water provides a favorable environment for bacteria and other microbes. In order to prevent the growth of these organisms, the paints are typically formulated with biocides to make them last longer. According to the German Paint and Printing Inks Industry Association, one in four buckets of paint will spoil unless preservatives are added. That translates to eleven million buckets per year, at a cost of ?470 million.1
There is a problem with biocide use, however: once the paint has been applied to the wall and begins to dry, liquid components evaporate, allowing biocides to escape into the air. Biocides, especially isothiazolinones, can trigger allergic reactions in some people.