The impact of photocatalytic interior paints on formaldehyde and VOCs in indoor air

Leif Wirtanen and Joonas Auvinen, Tikkurila Oy, Finland

People e.g. in the Nordic countries spend up to 90 % of their time indoors. Thus, we are almost continuously exposed to a multitude of chemicals commonly found in indoor air. Research conducted during the past decades has shown that these chemicals may cause adverse health effects, such as irritation of eyes, nose and throat, headache, fatigue, dizziness, sinus congestions, allergic reactions, and respiratory infections. Lately, photocatalytic paints have been launched on the market, which are claimed to have an air purifying effect. The photocatalyst added to these paints create radicals, when exposed to UV-radiation. These radicals react with e.g. organic compounds decomposing and degrading them via often very complex reaction chains. The end products of these chain reactions are carbon dioxide and water, if the reactions are fully complete (mineralisation). If mineralisation does not take place, then a great number of side products can be formed, which may be stabile and harmful.



In this study, six photocatalytic interior paints having different binder systems were examined. The target compounds used were formaldehyde and a mixture consisting of five common indoor air VOCs. The target compounds were introduced into environmental chambers containing the different paints. Tests were carried out using two different light sources under dynamic conditions. Samples were collected from the test chamber air and analysed using GC/MS and HPLC. A clear decrease of the formaldehyde or the VOC-mixture concentration could not be observed. But, on the other hand, it was observed that a number of new compounds was formed, both under normal office light and UVA-light. Typical new compounds included formaldehyde, acetaldehyde, acetone, etc. All possibly generated compounds could not be collected or analysed in this study, but the measurements clearly indicate that photocatalytic reactions generated by photocatalytic interior paints do not generate carbon dioxide and water only. The new compounds formed may be stabile and, in addition, detrimental to human comfort and health.