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Comment by remarkEon | Hacker News Reader

>Unfortunately, there's also bad pollution. The valley makes SLC prone to pollution and especially inversion layers in the winter and ozone in summer. You'd expect mountain air and you get that sometimes, but other times it's as bad as or worse than major cities elsewhere.

I had no idea about this, wow. What causes it? Just the fact that it's in a valley? I've been to SLC only once to visit some friends, but I guess I didn't really notice (was only driving through).

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As others have stated it’s directly tied to geography. For the same effect in a far more dramatic way look at Kabul.

https://www.aa.com.tr/en/asia-pacific/afghanistanair-polluti...

Kabul’s geography resembles an elevated bowl much like Oregon’s Crater Lake. Just like the SLC area Kabul’s air pollution problem is magnified during the winter.

In some ways, mid-winter Kabul reminds me a lot of Blade Runner. It's 9:30 pm, pitch black outside, the air is choking with dust and smog from people burning literally everything possible to stay warm. Visibility is less than a city block. You're rolling through an area with some neon lit wedding halls and suddenly there's a giant lit up billboard with 4G LTE mobile phone advertising on it next to a dozen artificial plastic fuschia/green/blue neon lit palm tree in front of a banquet hall. You drive onwards, your colleague in the passenger seat clutching their rifle between their legs, barrel resting on the floor.

Yeah, it's just the geography that causes it. It's enclosed on three sides by the Wasatch, Traverse, and Oquirrh mountains which causes cold air to be trapped there. The Salt Lake metro area isn't much different from other cities of similar size and makeup when it comes to actual emissions. It's just that those emissions stick around sometimes during a couple of weeks in the winter. Because of this, Utah meets all the annual mean PM 2.5 EPA requirements but fails the 24-hour limits (we have occasional very bad days but most days are good).

LA and Beijing have the same inversion problem. I think Denver does as well, but I’ve never experienced one there. Seattle has an anti-inversion (clouds get trapped between mountain ranges on all sides, pushing them up into rain, which keeps the air fairly cleaner than it should be).

Unfortunately "its just geography" is kind of one of the talking points for not really addressing the problem. Although true, concerted reductions in pollution have happened when there was political will to make it happen (mostly through the federal gov. / EPA clean air regulations).

Ogden and Provo are some of the worst offenders for per household air pollution emissions. Like many western cities they have longish commutes (everywhere) in large cars (trucks / suv's) with a high number of cars / household and almost non-functional public transport system. For the Salt Lake Metro area, per capita carbon emissions doubled between 1980 and 2015 because of increasing sprawl. Air regulations here are spotty for personal vehicles and I'm guessing almost non-existent for commercial vehicles. Oh and the state governments solution to this is to push a publicly subsidized "inland port" that will bring increased truck and rail traffic to the valley. The leaders of these tech companies are starting to point out that terrible air pollution for parts of the year is hurting recruitment so it seems like as the money flows into this sector maybe there will be political will on the state and local side to address some of these issues.

My family lives north of Salt Lake and it does indeed get pretty bad, especially in the winter. I declined a job a Utah valley last year and the pollution was a major driver in that decision.

I agree with the GP about the air pollution. I also find the Salt Lake reeks in the summer. When I would go with my dad as a kid on his business trips, the smell in the summer was really off-putting. I think it's the same problem Mexico City has. Salt Like City is in a bowl, and there's no coastal winds to blow the pollution away like the bay area has, so the pollution just lingers. I do think it's a really clean city on the ground though and Park City is so close and really amazing for Skiing / Snow Boarding. The national parks in Southern Utah are also top notch.

The smell was likely from the lake rather than pollution. The lake can be famously stinky in the right conditions.

More specifically, it's the smell of brine shrimp decaying on the lakeshore. But it's actually not a common occurrence for the Salt Lake stink to be present in the city itself. OP was just lucky!

It's a big bowl, like Los Angeles and Phoenix. Smog just gets kind of stuck there.

Except the Los Angeles basin is open to the ocean for a good portion of it. And the other side has a valley that leads to the IE, where pollution seeps and sits.

It’s the complete opposite of the two other examples in that list.

It’s the same with Calgary, Alberta as well. Rocky Mountains on one side and the prairie on the other. It still gets inversions and bad pollution.

My understanding is it’s a layer of cold air that sits over warmer air on the ground.

Inversion means warmer air is above cooler air - it's inverted from normal where temperature decreases with altitude and leads to a very stable atmosphere with little convection. So the air on the ground stays there.

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