The toxicity of tyre dust means that we need to concentrate on pedestrian and rail transport and simply drop mass road transport as we know it, says Alan Mitcham The researchers whose work you report on ( Study links childhood air pollution exposure to poorer mental health , 28 April) conclude that both “fumes” and “particulate matter” lead to higher “psychopathology scores”. We are told what constitutes “fumes” (nitrogen oxide) but not what makes up “particulate matter”. It is well known that particulates come from exhausts (especially from diesel vehicles) but, importantly, also from microscopic plastic and bitumen dust thrown up by abrasion between tyre tread and the tarmac of the road surface. Continue reading...