Based on a study done in Barcelona, air pollution is linked to slower cognitive development among 7-10 year old children. Researchers measured 3 cognitive outcomes, (working memory, superior working memory, and attentiveness) of 2715 primary school children in 39 schools. They compared students in high-polluted areas to those in lower polluted areas. Results showed that in less polluted areas children showed an 11.5% 12 month increase in working memory whereas children in more polluted areas showed only a 7.4% 12 month increase in working memory. The results claim that the developing brain may be vulnerable to air pollution well into middle childhood.