There is no known case of isocyanate used in paints causing cancer! But they are the biggest cause of occupational asthma in the UK. To confuse the two may cause someone to overlook the classic early symptoms of asthma – wheezing, breathlessness and tightness of the chest. This means they don't seek medical attention and the problems at work that are leading to exposure aren't put right because they are unlikely to link their symptoms to work. See the HSE/BCF worker's leaflet "Breathing isocyanate paint mist causes asthma" and get more information on the asthma webpages.