Air pollution is so bad in Mexico City that residents have less sensitivity to smells, according to a recent study.
"Tests showed people in Mexico City -- a sprawling metropolis crammed with around 20 million people and 4 million cars -- struggled to sniff out everyday odors like coffee and orange juice compared to residents of a nearby town."
"Their noses are so badly damaged from a life inhaling toxic particles that they also find it harder to detect the scent of rotten food, said researcher Robyn Hudson who ran the study."
"Mexico City is one of the world's most polluted capitals, along with Beijing, blighted by its thin high-altitude air and a ring of surrounding mountains that trap exhaust fumes belched from smoky buses and factories on the city outskirts."
"Mexico City's ozone levels exceed World Health Organization standards on approximately 300 days of the year."