Back in the 1990s, two workers were discovered lying comatose at the bottom of an empty pool. They were rushed to the hospital and later made a full recovery but they couldn't remember anything about how they'd gotten there or what they were doing. Well, for a while they couldn't even talk. Investigators later figured out that the fumes from the glue they'd been using to stick tiles to the floor of the pool had built up at the bottom of the hole. Essentially the two workers had been unknowingly sniffing glue for a while.

You've probably seen warning labels on things like glue and paint about this. Deliberately inhaling fumes, a.k.a. inhalant abuse, can be harmful, also fatal. The warnings are there because it's dangerous and there are people who do it on purpose but it's a really really stupid way to try and get high.

Inhalants can make people feel good for a short period of time, but they can also cause choking, asphyxiation, seizures, comas, death. The culprit here is usually a compound called toluene, a hydrocarbon meaning it's made up of carbons and hydrogens, and it's used in this like glue as a solvent. In the short-term, toluene has a direct effect on the central nervous system.

At first, inhaling it can cause a sense of euphoria as the toluene boosts the production of dopamine, a neurotransmitter that's involved in pleasure and reward. But it can also cause agitation, belligerence, apathy, vomiting, and other symptoms that are not as much fun. And of course it can be addictive. A high enough dose can lead to more severe symptoms like seizures or death. But even at lower doses, toluene can lead to serious health problems because it causes the sort of damage that stacks over time. I may have previously mentioned that inhalant abuse is a really bad idea. It may be worth mentioning again here. 

Among other things, chronic inhalant abuse can damage the sheath that protects nerves, which as you can probably imagine is not great for the brain or the rest of the body. It can lead to all kinds of cognitive problems and even dementia. That is on top of the heart, lung, liver, and kidney damage that can also come from chronic inhalant abuse. So glue-sniffing is addictive and causes all kinds of organ damage and sometimes death. Like I keep saying, it's dumb. It's a real dumb way to get high. And that is why they have the warning labels. 

Thanks for asking and thanks especially to all of our patrons on Patreon who keep these answers coming. If you would like to submit questions to be answered, you can go to patreon.com/scishow, and don't forget to go to youtube.com/scishow and subscribe.