Benzene from vehicle exhausts suppresses bone marrow and the development of red blood cells, and has been linked to leukaemia.

A six-city European study ascertained that, although hotter climates encouraged the build up of air pollution, the highest exposure levels were found in the Northern cities of Antwerp, Copenhagen and Rouen. The explanation seemed to be interior decor. When benzene enters a home, absorbent surfaces on walls, floors and furnishings tend to trap it. Northern decors - carpets, linoleum, wood, wallpaper - trap more than southern decors - tiling, marble and bare walls.

The study also asked 50 volunteers in each town to wear benzene monitors in order to compare personal exposure to measured street levels. They found that, on average, personal exposure was double that suggested on the street. The study’s leader, Dr. Vincenzo Cocheo of the Salvatore Maugeri Foundation in Padova (Italy) hoped that lawmakers will take this new approach to measuring exposure to air pollution into account.