(Bloomberg) -- Jakarta’s air quality deteriorated to the worst in four years in 2023 as a drier-than-usual El Nino weather pattern exacerbated the Indonesian capital’s pollution, according to a report.

The city of more than 10 million saw levels of particulate matter rise to 40-50 micrograms per cubic meter throughout the second half of last year, the highest since 2019, according to the Centre for Research on Energy and Clean Air. The World Health Organization said the level shouldn’t exceed an annual average of 5 micrograms.

Jakarta’s air pollution was the world’s worst on several days last year, compelling President Joko Widodo — himself nursing a cough due to the pollution — to struggle for solutions that ranged from planting trees, shutting down company facilities and spraying water on the streets. One minister said that air pollution costs 21.5 trillion rupiah ($1.4 billion) in economic losses.

The dry season induced by El Nino had worsened the capital’s existing emission from motor vehicles, factories and fossil fuel power plants, including those in surrounding areas. This year, Indonesia’s weather agency expects the dry season to begin in April, with a senior minister already floating the idea of boosting the use of cleaner fuels to curb air pollution and slash energy subsidies.

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