Seventeen million babies under the age of one are breathing toxic air, putting their brain development at risk, the UN children's agency has warned. <br/><br/>Babies in South Asia are worst affected, with more than 12 million living in areas with pollution six times higher than safe levels. A further four million are at risk in East Asia and the Pacific. <br/><br/>Unicef said breathing particulate air pollution could damage brain tissue and undermine cognitive development. <br/><br/>Its report said there is a link to verbal and non-verbal IQ and memory, reduced test scores, grade point averages among school children, as well as other neurological behavioural problems.