Toxic smoke from raging bushfires hit the Australian Open build up Tuesday as a qualifier retired with breathing difficulties and Eugenie Bouchard needed medical attention, while other players struggled in soaring pollution.
Air quality in Melbourne, habitually ranked as one of the world's most liveable cities, was among the worst on the planet and described as "hazardous" by city authorities.
Qualifying for the first Grand Slam of the year started late due to the conditions and Slovenian Dalila Jakupovic did not cope well, bringing an early end to her match against Switzerland's Stefanie Voegele after a coughing fit.
"I was really scared that I would collapse. That's why I went onto the floor because I couldn't walk anymore," she later told reporters, with searing heat not helping.
"It's not healthy for us," she added.
"I was surprised, I thought we would not be playing today but we don't have much choice."
Former Australian Open semi-finalist Bouchard also had problems and needed a medical time-out after reportedly complaining of a sore chest. She recovered to win the third set and the match.
Elsewhere in Melbourne, Maria Sharapova took to the court as scheduled against Germany's Laura Siegemund at the Kooyong Classic exhibition tournament. Both players agreed to call an early halt to the high-intensity contest at 7-6 (7/4), 5-5 in the German's favour after more than two hours, with the Russian star saying she could feel "a bit of a cough coming out through the end of the second set".
Melbourne's city government urged residents to "stay indoors, keep windows and doors shut, and keep pets inside" on Twitter.
Tennis officials have said there is little chance of the Australian Open being delayed, but that air quality is being monitored and umpires can halt matches to protect players' health.
Practice on outside courts was suspended but big-name players including world number one Rafael Nadal were not affected, with their hit-outs going ahead on Rod Laver Arena with the roof closed.