American jazz star Patti Austin has cancelled a concert in Beijing after suffering "a severe asthma attack".
A statement on the singer's website said Ms Austin was unable to perform at Forbidden City Concert Hall on Friday night "due to health problems".
While the cause of her illness has not been confirmed, it comes at a time of growing concern over air pollution levels in the Chinese capital.
The city has recently announced measures to combat worsening pollution.
They include taking half of the city's four million private cars off the roads on days when there are serious levels of pollution.
The system will be based on a vehicle's licence plate - odd numbers will be allowed on the roads one day, even numbers the next.
A statement on Patti Austin's website said: "She was taken in an emergency to the Peking Union Medical College Hospital this morning where she has been treated for a severe asthma attack in combination with respiratory infection.
"Ms Austin is currently resting in her hotel. Her current breathing condition does not physically enable her to perform tonight.
"Ms Austin is extremely disappointed about this situation since she was very much looking forward to performing."
Beijing has more than four million private cars, considered to be a major source of the city's air pollution
The new anti-pollution system will give out four different degrees of air pollution warning - blue, yellow, amber and red.
On days when an amber warning is given, factories will stop production and work will be halted on construction and building sites.
Restaurants which offer an open-air barbecues will be ordered to close temporarily, and fireworks will be banned throughout the city.
When a red warning is issued, the new car restriction measure will be implemented. Schools and kindergartens will also be closed.
The measure to restrict the number of private cars from using the road is proving to be controversial.
Critics have aired their concern that those who can afford to buy two or more cars will able to drive any day when the restriction is in force.
Beijing has almost 21 million permanent residents, according to official estimates.
Listen to Patti Austin's, 'The Ability To Swing' below: