Jakarta. As Indonesia prepares to host thousands of competitors and fans at next month's Asian Games, pollution concerns have flared following a spell of unhealthy air in Jakarta and forest fire hotspots near the second venue, Palembang in South Sumatra.

Traffic congestion in Indonesia's sprawling capital of 10 million consistently ranks among the world's worst, and it has long struggled to boost air quality, regularly rated as unsafe by the World Health Organization (WHO).

Organizers of the Asian Games, set to run from August 18 to September 2, drawing nearly 17,000 athletes and officials and more than 100,000 spectators, said they were working with city officials to tackle the pollution.

"It is expected that there will be better air quality at Asian games competition venues," the organisers said in a statement on Tuesday.

Strategies being considered include wider curbs on private cars depending on whether their licence-plate numbers are odd or even, creating special lanes for the sports event, and building gardens.

Indonesia is following a path blazed by other large Asian cities, such as Beijing, which adopted traffic curbs and closed factories to improve air during the 2008 Olympics.

Jakarta's average score on the Air Quality Index (AQI) had exceeded 100 in the last week, said Budi Haryanto, an environmental health expert at the University of Indonesia.

"Air quality is unhealthy, and this with the odd and even vehicle plate policy," he told Reuters.

By 11 a.m. on Tuesday, the air quality in Jakarta stood in the "unhealthy" range at 171, the Real-Time AQI Index showed.

"Since athletes need to give their maximum performance for the competition, a better AQI is a must," said Budi, who felt the optimum would be less than 50.

Lung function is affected after over two months of daily exposure to an index reading below 200, Budi said, but gasoline emissions, a frequent pollutant in Jakarta, can be linked to cardiovascular and pulmonary diseases, besides cancer.

Fire Hot Spots 

The smaller city of Palembang generally has cleaner air than Jakarta, but can suffer the ravages of forest and land fires, sometimes blanketing the area in a thick haze.

"The primary pollutant sources in Jakarta are mostly traffic and industry, while in Palembang, it is mainly from peatland burning," said Hsiang-He Lee of the Singapore-MIT Alliance for Research and Technology.

"Now is the peak of the burning season."

Indonesia's weather authorities are monitoring 12 fire "hotspots" in South Sumatra, they said this week.

Authorities are looking into the possibility of cloud seeding to combat the hotspots by triggering rainfall in dry areas with flares of salt shot into suitable clouds.

The strategy was successful in 2011, when Indonesia hosted the Southeast Asian Games in Palembang, but would depend on weather conditions, said Sutopo Purwo Nugroho, the spokesman of the disaster management agency.

Erick Thohir, head of the Asian Games organizing committee, told reporters last week he understood concerns over the haze, but believed efforts to control the fires were proving successful.

Reuters