Social media. All forms. Including this one.

I think it's about to be the weather

Carbon fiber dust.

Getting really speculative, but maybe Infinite Scrolling and similar UX design patterns. I think we learned it was dangerous pretty early in, but I have a feeling there isn't currently a widespread understanding of just how badly things like infinite scrolling shortcircuit parts of the brain and cause issues with attention and time regulation in large populations.

If I was more researched on it, I might include infinite short-form content feeds of almost any type to be honest, which may just be another way of saying social media.

Plastics

Microplastics and PFAS

No, seriously, these two will kill Earth, and us

By your definition we don't know yet. Ask again in 10 years.

Alcohol is a known carcinogen and many people still don't know that.

Don't forget teflon...

High Fructose Corn Syrup

Artificial sweeteners

ToS for digital products

Artificial sweeteners. Everyone is so obsessed with whether or not they cause cancer that their other potential effects get much less attention. There's a major industry push to keep them on the shelves, and we still have only recently discovered the gut microbiome.

Probably digital screen exposure. The impact of the digital age on mental health, especially due to increased screen time, is an area of active study. Some early research suggests potential risks, including impacts on sleep, attention, and mental well-being.

I would probably say either alcohol or microplastics. Both are carcinogenic. At least alcohol is avoidable, but microplastics pretty much saturate all of our environments. It reminds me of when they were doing experiments to figure out the impact of lead, they couldn't even open the door to the lab, because the airborne concentration of lead would throw off the readings. We might not ever know what real health is like without walking around with grams of microplastics inside us.

Gas cooking ranges

Edit to clarify: they're way too normal for how toxic they are.

Trans fats. Every processed food was full of the things until the mid 2000s, when it was discovered they were a leading cause of heart disease.

Soft drink. They are just sugar water and color chemistry that give color and flavor.

E-cigarettes
It is advertised as a safer option, but it is not.

Cars

Fossil fuels.

Things have slowly drifted from "we might wanna consider doing something before this becomes a problem" to "we need an immediate and concrete plan" to "anything short of immediate and drastic action is killing and will continue to kill people" over the course of the last decade or two.

Teflon.

It's been way more than one dangerous product per generation. So people should feel free to choose multiple current ones.

TikTok