Urban air is being polluted by antibiotic resistance genes (ARGs) whose exposure is posing threat to human health, researchers have warned.

Antibiotic resistance is caused by the incorrect use of antibiotics, and it has allowed many bacteria to be resistant to the commonly used antibiotics, which means that many antibiotics are no longer effective in treating common infections, Xinhua news agency reported. 

Many countries have adopted plans to tackle this problem, including monitoring the release of ARGs in waste water, pharmaceutical factories and animal husbandry, according to lead researcher Yao Maosheng, from the Peking University in China. "However, the presence of ARGs in urban air has not received enough attention," Yao said.

For the study, published in the journal Environmental Science and Technology, the team collected air samples from 19 cities in 13 countries and analysed the particulate matter (PM) using molecular technology. The analysis revealed 30 different types of ARGs that make bacteria resistant to seven types of antibiotics. ARGs resistant to vancomycin, one of the most effective antibiotics, were found in the air of six cities.

The study showed that some regions had seen increasing ARGs in the air in the past decade. ARGs can also adhere to airborne particles and spread to other regions, including places that use fewer antibiotics, which increases the chance of breeding new drug-resistant bacteria. Airborne transmission of ARGs might contribute to the spread of antibiotic resistance. The findings highlight the threat of urban airborne transmission of ARGs and the need of redefining our current air quality standards in terms with public health, the researchers said.