The air pollution in Indonesia's capital has become so bad that Jakarta regularly tops real-time charts of the world's most polluted cities, prompting a group of residents to sue their president and other Government officials for not taking action.

Key points: Air Quality Index scores of more than 200 are deemed "very unhealthy"

Air Quality Index scores of more than 200 are deemed "very unhealthy" At one point last month, Jakarta's air pollution levels exceeded 230 AQI

At one point last month, Jakarta's air pollution levels exceeded 230 AQI On the same day in Australia, the city of Sydney averaged just 15 AQI

Thirty-one plaintiffs lodged a citizen lawsuit in Central Jakarta District Court last week against President Joko Widodo, the Ministers of Health and Environment and Forestry, and three governors.

One plaintiff, Istu Prayogi, told the ABC she made a daily hour-long commute to the capital and that the poor air quality had affected her health.

"The doctor found several spots on my lungs," Ms Prayogi said.

"The doctor told me I have to always wear a mask and that makes me so uncomfortable and has disrupted my activities."

Just how bad is Jakarta's air?

Air Visuals app screenshots show Jakarta having the worst air pollution in the world in real-time rankings on June 4. ( Instagram: koalisipejalankaki )

Real-time air quality apps and indexes paint a startling picture.

Over the past month, Jakarta's scores have at times outstripped cities like Delhi, Beijing and Dubai.

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Swiss-based app Air Visuals ranks cities in real-time based on an Air Quality Index (AQI) of 0–500, with scores of 151–200 being "unhealthy" and 201–300 deemed "very unhealthy".

On June 25 this year, Jakarta peaked at a damning AQI of 231. In contrast, Sydney averaged an AQI of just 15 on the same day.

The Indonesian capital recorded the worst air pollution in South-East Asia last year, and Greenpeace said in March that Jakarta threatens to overtake China's capital of Beijing.

On average throughout the year, air quality in Jakarta regularly falls into the "unhealthy" category.

The index is based on the amount of particulate matter in the air of fewer than 2.5 micrometres (2.5 millionths of a metre).

The microscopic particles — about 3 per cent of the diameter of a human hair — can be damaging to public health because they can enter deep into the lungs, impact the heart and potentially enter the bloodstream.

Why is the air so filthy?

One of the main causes of air pollution in Jakarta is cars, which lead to traffic congestion every day. ( Flickr, VasenkaPhotography )

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A large percentage of the air pollution in Jakarta comes from cars and motorcycles.

According to estimates from the Jakarta Government, there approximately 3.5 million cars and 14 million motorcycles in the Indonesian capital.

And the number of petrol-guzzling vehicles hitting the streets of Jakarta increases by 8 or 9 per cent each year.

Jakarta, with its population of more than 10 million people, is known to struggle with traffic congestion, which costs the economy an estimated 100 trillion rupiah ($10 billion) annually.

Bondan Andriyanu, a climate campaigner at Greenpeace in Indonesia, said coal-fired plants were among the causes of bad air pollution in Jakarta.

"Emissions from coal-fired power plants are spreading all over the western part of Java," he said to Lowy Institute's The Interpreter, adding that there are seven existing plants and five planned plants within 100 kilometres of Jakarta.

What's the point of suing the president?

Indonesian President Joko Widodo, pictured with Australian Prime Minister Scott Morrison last year, is the subject of the lawsuit. ( AAP: Lukas Coch )

The lawsuit demands the President revise regulations on air pollution control and tighten national air quality standards to protect the health of its people and the environment.

It was coordinated by a coalition of Jakarta's Legal Aid Institute, Greenpeace Indonesia and the Indonesian Forum for Environment, or Walhi.

They began building a case after the aid institute started collecting online complaints from Jakarta residents in April 2018, following their study about worsening air pollution in Jakarta in 2016.

Lawyer Ayu Eza Tiara told the ABC the group had tried to explain the dire state of air pollution to Government officials but said they were dismissive.

"Their response was negative. They tend to be defensive by questioning our study methods," she said.

The residents of Jakarta said air pollution was putting their health at risk. ( Twitter, Indonesian Centre for Enviromental Law )

But Jakarta Governor Anies Baswedan said that every resident has right to lodge a lawsuit and he said he was grateful for the information provided by environmental activists.

"We could use and study the data that they provided," Mr Baswedan told the media.

What's the Government response to social media backlash?

Greenpeace Indonesia said emissions from coal-fired power plants also contributed to air pollution. ( Supplied )

Mr Baswedan also said the city would invest in more tools to monitor the air quality, telling local media the Air Visual app was limited because it only took data from a monitor at the US embassy.

"One of the steps we will work on is to have more air quality devices, so that we can get more data in Jakarta," he said last week.

However, Jakarta residents expressed their outrage on social media saying that the Government is not serious in tackling the problem.

They accused the government of denying the findings and created hashtag #SetorFotoPolusi, or "share your pollution photos", on social media, such as Twitter.

Dasrul Chaniago, the director of air pollution control at the Indonesian Environment and Forestry Ministry, cast doubt on the Air Visual rankings in an interview with CNN.

He said the dry season between May and September exacerbated the rankings and said that according to the Government's measurement system, Jakarta's air quality was better than Beijing's.