As the Australian Open started play on Monday, tournament officials were still monitoring a potential environmental crisis as a result of Australia's ongoing bushfires.
For all of the concerns about air quality, it turned out that the biggest issue related to playing conditions on Day 1 was heavy rain.
Last week, Tennis Australia boss and Australian Open tournament director Craig Tiley said that when it becomes obvious that smoke could have an impact, officials are prepared to act for the welfare of all involved, including players, fans and staff. Tennis Australia said it will work with its medical team, the Bureau of Meteorology and Environment Protection Authority Victoria scientists when making decisions about whether it's healthy to play.
Here are some frequently asked questions regarding the impact the bushfires could have on the first Grand Slam of the year:
How close are the fires to Melbourne?
Melbourne, home of the Australian Open, is the capital and most populous city of Victoria, one of the six states that make up Australia. The city is in the southeast corner of the country, along the coast where most people live and most of the bushfires have been burning. The major cities have largely been spared, but dense smoke has caused severe problems in some places, such as the Australian capital of Canberra. An ATP Challenger event scheduled for Canberra in early January had to be moved about 400 miles west to Bendigo because of excessive smoke in the atmosphere.
On Dec. 30, about 100,000 people were urged to flee five Melbourne suburbs as a heat wave combined with high winds left the city suffocatingly hot and dense with smoke. One firefighter was killed on the outlying countryside. While fire is the preeminent danger, smoke -- sometimes driven over great distances by wind -- is a more sinister threat that cannot be fought.
The situation in the state of Victoria has forced @vicemergency (the state's official alert system) to issue at least one recent emergency warning of "imminent" danger from a bushfire for Noorinbee, 230 miles east of Melbourne. "You are in danger and need to act immediately to survive," the warning said.
Is it safe to attend the Australian Open?
There appears to be little danger from fires at the moment, but heat is always a factor Down Under. This year, smoke -- and the toxic elements it carries -- is an active concern, especially in combination with the familiar Melbourne heat.
The city has already closed a number of beaches and pools, sporting events have been canceled, and construction workers have been forced to abandon outdoor projects. Ambulance calls for people struggling to breathe have also risen significantly.
The smoky days at the start of the new year spurred many people to purchase P2 and N95 masks. The Australian Medical Association has advised people with preexisting lung or heart conditions, as well as those sensitive to smoke, to take special precautions. Many have purchased the common, relatively inexpensive, small respirators that slip over the nose and mouth -- the ones commonly used by house painters, woodworkers and others. Visitors to Australia have been advised to bring their own.
How will Tennis Australia determine whether conditions are safe for the players?
In a statement issued to the media on Jan. 6, Tiley said: "There will be meteorological and air quality experts onsite to analyse all available live data and assess in real-time the air quality at Melbourne Park, and we always work closely with our medical personnel and other local experts."
On Tuesday morning, with Melbourne's air quality officially ranked third-worst in the world, Tiley and chief operating officer Tom Larner fronted a hastily arranged media opportunity to assure that the tournament would act in the best interests of the players, fans and staff.
"This is a new experience for all of us in how we manage air quality, so we have to listen to the experts," Tiley said.
On Friday, Australian Open organizers belatedly published details of their "Air Quality Policy," confirming that play at the first Grand Slam event of the year could be stopped if conditions are considered to be adverse to players' health.
Responding to criticism from players who said they had not been fully informed earlier in the week, when smoke from the bushfires blew into Melbourne during the qualifying event, officials released the policy.
However, the decision of whether to stop play will still be largely at the discretion of the tournament referee.
The Air Quality Rating (AQI) consists of five bands from one to five, "determined by analyzing concentrations of air pollutants at Melbourne Park and in particular, the fine particulate matter rating (PM2.5)."
Play is allowed under the first three bands -- "good" (below 27), "moderate" (27-62) and "air may affect sensitive groups" (62-97) -- but if the level is between 97 and 200, "match play may be suspended," though that will be up to the tournament referee.
If the rating is in the fifth band -- more than 200 -- then play will automatically be suspended.
The publication of the policy came three days after organizers were heavily criticized for allowing play to go on when a number of players complained of breathing difficulties at the qualifying event.
The AQI reading from the station nearest Rod Laver Arena on Monday morning was 427, which is considered "hazardous."
Tennis Australia has never had an air-quality policy because it has never before been a significant issue.
Due to the constant threat of excessive heat, tournament officials have established sophisticated protocols for measuring conditions, including the WetBulb Globe Temperature (WBGT), and the tournament has a transparent extreme-heat policy in place. It features a five-step Australian Open heat-stress scale that measures heat-related factors that trigger a variety of remedial actions, from brief breaks to suspension of play sitewide.
Over the years, those protocols have evolved from a simple dictate in 1998 to suspend play when the temperature hit 104 degrees Fahrenheit to a suite of responses depending on the temperature and WBGT index (which takes factors other than temperature, including humidity, into consideration). The measures include closing the roof on covered courts during day matches, heat-mandated 10-minute breaks between sets and stoppages of at least two hours.
The athletes have various ways of dealing with heat, including iced towels, appropriate headgear, misting fans, frequent changes of clothing and strategies that include prematch hydration at hourly intervals, salt tablets, etc. But there's little that anyone can do to help the air quality. Masks might help, but they impair oxygen intake. Inhalers that soothe sore throats might provide temporary relief from soreness, but they could also mask the damage being done.
Do the ATP and WTA have protocols to safeguard their players?
Both the ATP and WTA have told ESPN.com that they are leaving decisions about the playing conditions in the hands of Tennis Australia. But Djokovic told reporters that he put air-quality considerations on the agenda at the annual player meeting that precedes the tournament.
That's a good idea, given Tennis Australia's lack of a transparent mechanism for determining when to pull the plug on play due to hazardous air quality.
While practicing in Melbourne during the worst days of smoke in early January, Denis Kudla told The New York Times, "If it's anything like yesterday, I don't think it would be safe over a two-, three-week period. You could play [in the Australian Open], but who knows what damage we're actually causing ourselves? It can't be good."
What recourse does the tournament have in the event that the air quality halts play?
It sounds far-fetched, but in a worst-case scenario, the Australian Open could become the first hybrid outdoor-indoor tournament. That's because the National Tennis Center has four roofed stadiums as well as eight indoor courts. The air circulation systems in the roofed venues include some filtration, but earlier this month in Sydney, the smoke overwhelmed some air-conditioning units and triggered smoke alarms in some buildings. Tiley said, "[We have] effectively weatherproofed the Australian Open."
We might yet see whether that also means they have smoke-proofed it.
How are the players feeling about the challenges they might face?
Some players struggled with breathing during qualifying last week, when the air was among the worst in the world because of smoke from fires 100 miles away. On Monday, though, all appeared to be fine.
"Today, it seemed normal," Serena Williams said after her first-round victory. "Yeah, it seemed pretty good."
During qualifiers, smoke and hazy conditions at Melbourne Park affected the players, with organizers criticized for allowing matches to proceed. The start of qualifying was delayed by an hour on Tuesday due to the smoky haze, but practice sessions were canceled.
A number of players complained, including Australian Bernard Tomic, who sought medical treatment after he struggled to breathe during his first-round loss. Slovenia's Dalila Jakupovic said she feared she would pass out before she retired from her match after collapsing to her knees with a coughing spell.
"I was really scared that I would collapse," Jakupovic said. "That's why I went onto the floor -- because I couldn't walk anymore."
Australian Open officials delayed play by three hours during qualifiers on Wednesday, but the air-quality index was still graded as "unhealthy" when the players took to the court.
On Thursday, British player Liam Broady accused Australian Open officials of treating qualifiers worse than animals. Calls are growing among players to form a union.
Tiley addressed the criticism from players saying: "Our medical team were satisfied with the conditions that the players were competing in [in qualifying], per all of the research and the data and the science that they have.
"But they also make an assessment. You could have been two hours into those matches and have 25 people presenting themselves with a medical condition that may be related to the pollutants."
The ATP and WTA Player Councils met separately on Friday in Melbourne, with smoke and playing conditions high on the agenda at both.
Despite the concerns, many of the top tennis players have vowed to support Australians suffering because of the bushfires.
Nick Kyrgios got the ball rolling when he pledged to donate $140 (U.S.) for every ace he hit during the ATP Cup. Scores of ATP and WTA players followed suit. Williams donated her $43,000 ASB Classic winner's check to Australian wildfires victims. The ATP donated $725,000 on behalf of the players, and the ITF will contribute an additional $400,000.
Roger Federer, Rafael Nadal, Kyrgios, Williams and others took part in a Rally for Relief bushfire charity exhibition at Rod Laver Arena on Wednesday. According to Tennis Australia, the event raised nearly $3.5 million for the bushfire relief effort. The event drew a capacity crowd of more than 15,000. During the event, Nadal announced that he and Federer would combine to donate $250,000. Despite the drive to support the bushfire victims.
During Saturday's media day, Federer led a chorus of criticism of tournament organizers for their handling of events earlier this week. Federer said he had made a point of going to see tournament officials when conditions were at their worst to try to find out the rules.
"I said, 'I think we're all confused. Is it super unsafe, or is it totally safe to play?'" he said.
Nadal said he also consulted tournament officials and was content with their explanation, but other players were more forthright in their criticism.
Canadian Denis Shapovalov said the players had been "left in the dark," it was "scary," and he would refuse to play if he felt the conditions were unsafe, regardless of what the tournament says.
Information from the Associated Press, AAP and Reuters contributed to this report.