We are all exposed to polluted air. Among main air pollutants are nitrogen oxides —the so-called ‘NOx ‘— and ozone , which cause irritation of respiratory tract and eyes, favouring cough, lung infections in children and asthma.

It is not obvious when examining a wrapped lettuce or a microwavable bowl of Chinese soup. But plastic food packaging is made of multiple layers designed to act as a barrier for oxygen or bacteria .