Plenary Lecture 1

Now more than ever we are aware of a multitude of risks we face in indoor and outdoor environments where we live, work and play. Many of these risks are related to the quality of the air we breathe: ambient particulate matter is one of the main risks, as well as airborne infection transmission. Particles in indoor and outdoor air originate from many different sources. Scientific knowledge about the emission, transformation, transport, and impact of particles is advanced, based on decades of research. However, in practice, we cannot protect ourselves from infectious respiratory particles, nor can we derive the exposure–response relationships of ultrafine particles or decide how to scale up the application of low-cost optical particle sensors for routine indoor air monitoring. There are missing elements in the jigsaw puzzle of science, technology, applications, and regulations that prevent us from achieving healthy, clean air for all. How can we complete this puzzle?