Biomakers and other substitute measures in indoor air sciences

The variables that can be quantified in biological systems are called biomarkers. In a broadest sense biomarkers are substitute measures used because the variable of interest cannot be measured for practical, economical or principal reasons.The quality of a substitute measure refers to the quality of the predictions which can be made based on it. Those predictions must have a very low frequency of mistakes.The indices cannot be used alone unless better documentation of the quality of their predictions is established. Guideline values are to be established nationally or internationally by relevant organizations for the factors indoors which can cause adverse health effects. It is urgent to create such guidelines.