A study has found that Mexico City's notorious pollution is damaging people's sense of smell, reports Reuters.

Robyn Hudson, a researcher at Mexico's National Autonomous University in Mexico City and her team found that residents of the capital were less able to detect common odours like coffee and orange juice than those in a nearby town with low air pollution.

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, researcher Robyn Hudson, who ran the study, told Reuters. "We added a substance [to powdered milk] that is a common contaminant of food, something that smells disgusting, basically - like a sour, rotting cabbage," said Hudson.

"We were able to see at what point ... they would start to reject the contaminated sample, say, 'Ew, yuck! No! Take it away, please'," said Hudson.

Reuters didn't say if Hudson had published a paper on her smell study, but a Google search showed an earlier study in the journal Chemical Senses, authored by Hudson and titled "Effect of Air Pollution on Olfactory Function in Residents of Mexico City". In that study, published in 2005, researchers exposed subjects to squeeze-bottles filled with common beverages like mango Tang.

The researchers found that the subjects from Mexico City had higher thresholds for detecting a smell, a poorer ability to describe smells, and a poorer ability to discriminate between smells than subjects from Tlaxcala, a state to the east of Mexico City that is geographically similar but has less pollution.

Mexico City is known for some of the world's most polluted air. The city of 25 million sits in a valley atop a high plateau, an ideal spot for smog to settle. Government figures suggest that the poor air quality may account for tens of thousands of premature deaths.

Reuters notes that a 2007 study in the American Journal of Respiratory and Critical Care Medicine found that school children in Mexico City had developed unusually small lungs.