(CNN)Fed up about worsening air pollution in the Indonesian capital, a group of Jakarta residents is suing the country's president.
Ayu Eza Tiara, one of the lawyers working on the case, said that 31 people had joined the lawsuit in the past week, which will be filed against President Joko Widodo, as well as the country's Home Affairs Minister, Health Minister, Environmental Minister and the Jakarta Governor Anies Baswedan.
Those joining the lawsuit are ordinary citizens, including artists, academics and businessmen, according to Ayu Eza Tiara, from the Jakarta Legal Institute.
"We have been trying so far to make it clear to the government how bad the pollution is in Jakarta and its impact, by showing them data and study research," she said. "But ... they have given a negative response to us."
The government denied there had been a drop in quality air around Jakarta in the past year, and called on the media not to "dramatize" the situation.
But Bondan Andriyanu, a climate and energy campaigner for Greenpeace Indonesia, said air pollution has been steadily worsening.
The Indonesian capital had the worst air pollution in Asia on June 14, higher than any pollution black spots in China and India, Greenpeace said. On that day, Jakarta's air quality rated 189, according to the US Air Quality Index, which is considered "unhealthy."
According to the US embassy's pollution meter, Jakarta's AQI reading for June 2017 on average was 74. In June 2019, it was twice that -- 148.
While Jakarta ranked 160th out of thousands of cities for overall air pollution in the 2018 World Air Quality Report by IQAir Air Visual, the average amount of hazardous PM 2.5 particulates in the air rose more than 50% between 2017 and 2018.
Dasrul Chaniago, the director of air pollution control at the Indonesian Environment and Forestry Ministry, said his government didn't recognize the Air Visual rankings, because they were measured by instruments held indoors, not outdoors.
Chaniago added that air quality always worsened during the dry season in Jakarta, between May and September.
According to the government's measurement system, the Air Quality Monitoring System (AQMS), Jakarta's pollution levels were still lower than Beijing's, he said. By AQMS measurements, Jakarta's average pollution level in 2018 was 34 micrograms per cubic meter, while in 2019 it is currently 30 micrograms.
"Don't dramatize the situation," Chaniago said.
But Greenpeace's Andriyanu accused the government of ignoring demands for an explanation.
"Transportation is not the only thing that's causing the air pollution, there are many other sources," he said, noting that Jakarta's famous congestion is easing. "How about the industry area near the city?"
The government was initially notified of the impending lawsuit in December 2018, to give officials a chance to improve the quality of the air, said Ayu Eza Tiara, from the Jakarta Legal Institute.
"But they ignored us. It is also (a) human rights violation because air pollution is a silent killer," she said.
A study by the World Health Organization in 2017 found that air pollution caused about one in four deaths of children aged under five, worldwide.
While the lawsuit makes it way through the courts, Greenpeace's Andriyanu called on the government to conduct more research into the causes of pollution. "It should be done with other institutions and cross-border stakeholders," he said.