Ah Shit, Here We Go Again


Piotr Jakubowski





English / Indonesia

One of the main reasons that I became interested in air pollution is the data. Nearly 4 years ago we had the crazy idea of installing the largest outdoor air quality data network in Indonesia.

Today, nafas - Air Quality Solutions has the largest network of sensors in Indonesia - over 200. That’s 3x more than the Indonesian Government and is the largest privately owned air quality network in South East Asia.

Each year, the Nafas network collects over 70,000,000 outdoor air quality data points.

In fact, Nafas data was used by the Indonesian Health Minister Budi Sadikin in his presentation to President Jokowi during the emergency cabinet meeting in August 2023, when thousands of children were in hospitals and an air pollution crisis became top headlines:

The best part of access to real-time air quality data - trends.

Nafas utilizes the US EPA scale for air quality measurement, which starts at Good, then Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy and Hazardous. For reference, the World Health Organization recommended yearly exposure of PM2.5 is 5 ug/m3.

Here’s a myth-busting example. In 2021, Katadata & Bicara Udara conducted a survey of air quality knowledge among nearly 7,000 Indonesians which discovered some interesting insights.

The survey showed that over 80% of respondents believed that air quality was BEST in the morning (before 8am) - because there’s less cars on the road.

Looking through 4 years of data we can see that this is false.

Air quality is WORST in the morning. Here's 24hour data from Tangerang Selatan, DKI Jakarta and Surabaya averaged out across 2023. Which is the worst hour of the year for air pollution?

DKI Jakarta 24 Hour Average - 2023

Tangerang Selatan 24 Hour Average - 2023

Surabaya 24 Hour Average - 2023

7AM, smackdab in the middle of the morning.

Merging air quality data with atmospheric data explains this point, variations in the planetary boundary layer and the height of the mixing layer within our troposphere throughout 24 hours play a massive role in this - but that’s another post.

Or another one - 75% of respondents believed that planting trees will help reduce pollution and make air quality healthier.

Looking through 4 years of data, we can see that this is false - air quality in Tangerang Selatan a suburban area of DKI Jakarta has been between 18%-26% worse than the capital city.

Developers in Tangerang Selatan have been selling the healthy air dream since the 1990s, but the numbers say otherwise.

Trees don’t reduce PM2.5 pollution significantly.

Merging air quality data with meteorological data and geospatial data helps us understand why places we think are healthy - like Tangerang Selatan or Bandung - are actually much worse. But that’s also a separate post.

But to see the largest, and most damning trend, we need to take a look at the last 10 years.

After 2 years of Nafas data, we were able to see what we’ve now called the “Bad Air Season”. Each year, the average pollution levels would start increasing in May/June.

Here’s what the last few years looks like:

DKI Jakarta Monthly Average PM2.5 Percentage - 2021

This was the "pandemic" year, where even today people remember "all the days of blue skies". In April, the percentage of "Unhealthy" air per month increased significantly between April and September.

DKI Jakarta Monthly Average PM2.5 Percentage - 2022

The following year between April & September, the number of "Unhealthy" and "Unhealthy for Sensitive Groups" hours increased significantly.

DKI Jakarta Monthly Average PM2.5 ePercentage - 2023

And in 2023, from May until October, air pollution levels increased significantly and remained terrible throughout the end of the year - thanks to El Nino.

To get an even longer term picture, let’s take a look at US Embassy data from the last 8 years. Looking past the variation of “how bad” each year is, there’s a very clear trend - from May until September/October, air pollution levels are unhealthy. Even during the pandemic!

Bad Air Season is actually a “thing”, and high air pollution episodes happen.


It’s been happening in the past, and the University of Indonesia predicts it’s going to get even worse in the future.

So if you’re living in Jakarta, or any large cities in Indonesia - it’s time to get ready. We’re at the start of May, and this is what it looked like this morning:

Remember last year?

When hospitals were full of kids, everyone was coughing or sick, and the President called an emergency cabinet meeting?

Ah shit, here we go again.