Despite recent improvements, "the level of key air pollutants in many European countries remain stubbornly above World Health Organization" (WHO) guidelines, particularly in central-eastern Europe and Italy, said the EEA after a study in over 30 countries, including the 27 members of the European Union. Seven million dead annually Poor air quality can also "aggravate chronic conditions like asthma, which afflicts nine percent of children and adolescents in Europe, as well as increasing the risk of some chronic diseases later in adulthood". Fine particulate matter, primarily from cars and trucks and which can penetrate deeply into the lungs, is considered the worst air pollutant, followed by nitrogen dioxide and ozone