Polluted city air alters the molecular structure of “bad cholesterol” (LDL), facilitating the build-up of fatty layers in the arteries and increasing the risk of heart attack and stroke, according to a study by Sandra Regina Castro Soares, for her doctorate in medicine at the University of São Paulo. Her study compared mice that lived their first four months (equivalent to 40 human years) in chambers with filtered air, with others that breathed São Paulo air. The second group was found to have altered LDL and antibodies that indicate higher risk of heart attack.

São Paulo air has improved a great deal in the past decade, reducing the volume of particulates of less than 50 micrograms, but the study showed that “it is insufficient,” said Lucía García, Castro Soares' advisor.