Cairo, Egypt, is one of the world's most polluted cities, if not No.1.

I recently visited and found that, even after just a day in the city, I could feel the effects on my breathing, sleep, and skin.

The experience reminded me of how lucky I, as an American, am to have the air quality in the country I live. I think most Americans have no conception of what it is like to live in a heavily polluted city like much of the world in Egypt, China, and India.

The Egyptian government is taking steps to improve air quality, with a plan to reduce air pollution by half by 2023.

I don't think I understood what it was like to live in a truly polluted city until I went to one.

As an American, I'd never really experienced a place choked with smog. New York, my home, is the 21st most polluted city, according to a recent study by Eco Experts, which combines data on air quality, noise pollution, and light pollution. Los Angeles, which I've been to a few times, comes in 10th.

That's a far cry from the cities that top the list, where checking particulate matter levels, or PM, is as routine as checking the weather.

I got my first taste of the smog life in April, when I visited Shanghai and Beijing (7th and 3rd on the Eco Experts' list).

While the pollution was noticeable — I saw a blue sky only a few times on that entire trip — I was in town during what was comparatively the best time of the year, pollution-wise. The winter in Beijing, when millions are burning coal for heat, is when the real pollution rolls in.

Cairo is one of the most polluted cities — you can feel it

I rode in a taxi from the Cairo airport this past week, it hit me that I'd entered the big leagues.

As a city of more than 20 million people, Cairo is the most populous city in the Middle East and the second most populous in Africa. And it feels like it.

Every highway, road, and alleyway is clogged with cars and motorbikes spewing fumes into the air. The honking never stops: long honks, short beeps, and everything in between. The cars, and their drivers, are in every kind of conversation imaginable. Other noises proliferate, from street-side shouts to the rumble of construction. Every street seems to have a construction site and a building under renovation or being built.

Cairo is the most polluted city in the world, according to the Eco Experts' report. The World Health Organization's Global Ambient Air Quality Database, which focuses on measures of air quality, ranks Cairo second worst for PM10, or particulate matter that is 10 micrometers in diameter or less. When judging by PM2.5, or particulate matter that is 2.5 micrometers or less — the worst kind of pollution, according to the Environmental Protection Agency — Cairo is not quite as bad, but still near the bottom.

Particulate pollution is made up a mix of solid and liquid droplets in the air, including sulfates, nitrates, and carbon. It's largely caused by energy used by homes, automobile traffic, manufacturing, and power plants. Sand or desert dust can add to the air pollution. In Cairo's case, the city is in a valley and has a large industrial sector, tons of traffic, poor waste management, and a dusty climate, according to the Arab News.

“Air pollution threatens us all, but the poorest and most marginalized people bear the brunt of the burden,” Tedros Adhanom Ghebreyesus, WHO's director general, said in a statement regarding its most recent report.

On average, residents of Cairo breathe in air suffused with 11.7 times the WHO recommended safe level of PM2.5 and 14.2 times the safe level of PM10. Translation: The air is really bad and you can feel it.

Dry mouth, itchy eyes, and rashes: Bad pollution has immediate effects

The view from my hotel room in the morning. Harrison Jacobs/Business Insider

Within a day of being in Cairo, the effects started to settle in. When I woke in the morning to look out the window the first few days, a thick haze lay over the city.

After a few hours walking around in even one of the more green neighborhoods — the embassy-populated, moderately wealthy island of Zamalek — I found myself severely dehydrated despite having a water bottle by my side the whole time. The taste in my mouth was bitter, my nostrils felt caked in dust, and my eyes had grown itchy. It feels like you're constantly at a construction site, with sawdust or concrete dust in the air. After a few days, I'd found that my skin, unused to the pollution, was breaking out in hives on my face.

And that's just the air pollution.

Cairo's noise pollution is arguably worse, though it is rarely talked about. Eco Experts' research found that Cairo is the third loudest city, after Guangzhou, China, and Delhi, India. A report by the Egyptian National Research Center found noise pollution in Cairo reaches a daily average of 85 decibels or, in the words of Eco Experts, “like spending all day inside a factory.” Even at 3 a.m., the honking doesn't stop.

What my face wipe looked like after a day walking around Cairo. Harrison Jacobs/Business Insider

The honking, shouting, and construction noises are ever present, no matter where you are in the city. It literally leaves your ears ringing. Even as a New Yorker who lived for years above bars in the rambunctious East Village, I found the noise shocking.

Combine that with the light pollution — Eco Experts reported Cairo the third-brightest city, with artificial light 85 times as bright as the natural sky — and it all makes for a bad night's sleep.

Every night, I slept with blackout curtains drawn and earplugs in. And still I found myself to be getting terrible sleep. Every day, I overslept and woke up groggy. Before you assume jet lag, I was in the region for three weeks and slept fine while in the United Arab Emirates.

Over time, pollution has devastating effects

A farmer burns rice straw at his field in Qalyub in 2016, causing a "black cloud" of smoke that spreads across the Nile valley, near the agricultural road that leads to Cairo. REUTERS/Amr Abdallah Dalsh

All of this after a week. Imagine living in it for a few months, a year, or your whole life.

My partner, who has more sensitive lungs than I do, contracted pneumonia and a respiratory infection halfway through a semester studying in Shanghai. When we visited Shanghai in April, she'd contracted a wheezing cough after a day in the city.

Researchers and scientists are still studying the effects of pollution on humans, but it has been connected to health conditions like asthma, lung cancer, heart disease, stroke, and chronic obstructive pulmonary disorder, according to WHO and the EPA. Researchers suspect that pollution is connected to obesity, insomnia, depression, as well as effects on the immune, endocrine, and reproductive systems.

One recent study out of Beijing Normal University's school of statistics found that long-term exposure to particulate matter was correlated with cognitive declines in study participants as they aged.

The Egyptian government pushed back on the Eco Experts report shortly after it was published, criticizing the methodology of the study. But there's no denying the pollution in Cairo. It would appear the Egyptian government agrees with that much.

Earlier this year, the government announced a plan to reduce air pollution by half by 2023, and began an initiative to plant 1 million fruit trees in public spaces throughout the country.

A major pollution issue for Egypt since 1997 has been farmers' yearly burning of leftover rice straw from September to November, which can create a "dark cloud" over Cairo. To tackle the issue, the government has offered to buy the straw from farmers for $3 a ton, Mohamed Salah, head of the Egyptian Environmental Affairs Agency, said in October.

"Today, the dark cloud season is over and all citizens in Egypt are saying that they have not sensed any problem relating to this, unlike what had happened in previous years," Salah said.

But, for this American in Cairo, I found the city to be stark reminder of how lucky the US is when it comes to air quality and pollution and how little we bear the burden of global manufacturing and other polluting industries around the world.

When I told one Beijing resident in April that I head to the countryside outside New York City when I want fresh air, he looked at me incredulously. He said: "You have to understand: We think of New York City air as pristine."