In my first year living in an industrial, traffic-clogged mega-city, I was not that fussed about air pollution. Then my baby son started coughing.

My family had just returned from a trip abroad with lungs full of crisp, clean air.

As our plane descended from the big blue into a dense, brown blanket of smog, I thought something onboard was burning.

But it was Jakarta's smoggy air all along.

For three consecutive days this week Jakarta's air was rated the worst in the world. ( Reuters: Willy Kurniawan )

Two days later, our boy started waking up in the night with coughing fits — nothing particularly unusual for a 15-month-old.

But that was almost six weeks ago.

Almost every night since then, we have been up with him in the dead of night, often for several hours, trying to prop him up, give him water, anything to ease his discomfort.

In the meantime, I have become completely obsessed with Jakarta's air.

Instead of my phone, I now reach for the air quality monitor when I first wake up.

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I have taped up almost every window and door in our home and had quality air purifiers installed in every room.

Among the lucky few in this city who can afford to take such measures, we have taken our baby to Bandung, Bali and soon to Australia, to get some relief.

The vast majority of people here just have to cop it.

Air pollution appears to peak at odd times

Over the last two months, Jakarta has almost constantly ranked in the top 10 of the world's most polluted cities, according to AirVisual data.

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For three consecutive days this week, it has been ranked as the world's smoggiest.

Bizarrely, the most dangerous pollutants, known as PM 2.5 — particles smaller than 2.5 microns, which is about 25 times thinner than the width of a human hair — have been spiking during quiet periods.

Jakarta usually enjoys rare blue skies in June, thanks to a mass exodus for the Eid al-Fitr holidays, but not this year.

In the last month, some of the highest levels of air pollution have been recorded early on Sunday morning, during the city's 'car-free day' when motorists are banned from the roads.

Jakarta residents are wearing face masks, avoiding exercise and keeping their kids indoors. ( Reuters: Willy Kurniawan )

"The spike data is starting from 12:00am until 9:00am," said Bondan Andriyanu from Greenpeace Indonesia, who has been monitoring the levels of PM 2.5.

"This is [some] of the evidence that [when] we are talking about sources of air pollution, this is not coming from transportation."

Official data suggests transportation makes up 75 per cent of air pollutants in Jakarta — but that was published in 2012.

There has been no publicly released data since then.

"Somehow they stopped doing it and now the debate is happening in the public. Where is the air pollution coming from?" he asked.

Residents demand action as city chokes

At the Pasar Minggu Children's Hospital in Southern Jakarta, paediatrician Ardentry, who uses only one name, has been concerned by children's chest x-rays.

Dr Ardentry (left) says she's noticing more spots on children's lung x-rays lately. ( ABC News: Phil Hemingway )

She said around half of the patients who come to her clinic have breathing problems, and it seems to be getting worse.

"I've been observing this for a couple of months," Dr Ardentry said.

"Children who've been coming to the hospital with breathing difficulties and fever, their lungs showed more obvious and significant spots and infiltrations compared to those … in the previous months before dry season."

There is no direct scientific link with the worsening air pollution, but the smog is clearly not helping.

Jakarta residents have filed a civil lawsuit to demand better air quality in the capital. ( ABC News: David Lipson )

Yesterday, a group of concerned residents took the matter to court, hoping to force President Joko Widodo and Governor Anies Baswedan to improve the quality of air.

"We are hoping that the Government performs [its] duties that [are] prescribed in the law, that they have to maintain the air quality to be safe and healthy," said Nelson Nikidemus Simamora, one of the lead plaintiffs.

Another plaintiff, Veronica, was merely hoping for reliable information about Jakarta's air quality and how best to protect her six-year-old daughter, who has asthma.

"In the mornings [it's] terrible. It's getting harder for her to breathe," she said.

"I'm not really into environmental issues. I'm not an activist. I want to know more from the Government. I think that's my right to know."