CO, carbon monoxide: it attaches to the red corpuscles and causes respiratory and cardiac problems, headaches, dizziness, nausea and problems with vision.
 NOx, nitrogen oxides: these irritate the bronchial tubes and lower immune defences. They increase the frequency of asthma attacks and encourage pulmonary infections in children.
 HC, hydrocarbons: they cause irritation to the bronchial tubes and eyes and can have a carcinogenic effect
 Pb, lead compounds: in heavy doses, they cause major neurological effects (lead poisoning) as well as growth problems, anaemia kidney failure. However, thanks to the use of lead free petrol, they are gradually disappearing from the air.
 Benzene: it is carcinogenic and has a depressive effect on the central nervous system.
 Particles: they transport other HC pollutants into the lungs and nasal membranes. They are particularly dangerous for people with asthma and heart problems.
 O3, troposperhic ozone: this is a very irritant gas. It alters respiratory function, irritates the eyes, chest and lungs, especially in children. It aggravates asthma and heart disease.