Know What You Smoke

20×more ammonia in cannabis smoke than tobacco smoke

1,375%increase in child cannabis poisonings since 2017

28 daysfor brain receptors to recover after quitting

What this site is about

Cannabis is legal in Canada as well as many US states. Most people who use it are not bad people. Most of them also don't have a clear picture of what the smoke actually does — to their own bodies, to the people nearby, or to children who grow up around it.

This site exists to fill that gap. Every claim links to a peer-reviewed study. If something turns out to be wrong, there is a correction link at the bottom of every page.

Three things most people don't know

1. Cannabis smoke is not harmless.

Burning cannabis produces ammonia at up to 20 times the concentration found in tobacco smoke, along with hydrogen cyanide at 3–5 times tobacco levels. The "it's just a plant" argument ignores what happens when you set that plant on fire and inhale the combustion products.

2. The product has changed dramatically.

Average THC concentration has risen from about 4% in the mid-1990s to over 12% by 2014. Modern dispensary flower routinely tests at 20–30%. Concentrates can hit 80–90%. The joints your parents might have tried in college are a completely different product from what is on shelves today.

3. Secondhand smoke is not just an annoyance.

In a preclinical study, one minute of secondhand cannabis smoke exposure caused blood vessel impairment lasting over 90 minutes — more than three times longer than the same exposure to tobacco smoke. For children, who breathe roughly twice as fast as adults, the exposure adds up quickly.

Where to go from here

Your body

Health Effects

What cannabis smoke actually does to your lungs and brain, based on clinical research.

Shared air

Secondhand Smoke

How smoke from one person affects everyone nearby — and why distance matters more than you think.

Children

Protecting Kids

Why children are especially vulnerable, and what the research shows about growing up around smoke.

Taking action

Quitting & Alternatives

What to expect when you stop, and how to switch to options that don't affect the people around you.

Why I built this

My name is Nathan Chen. I am a high school student, and cannabis smoke has become an unavoidable part of daily life in my community — parks, sidewalks, apartment hallways.

What pushed me to build this site was watching it happen around kids. Parents smoking next to strollers. Adults lighting up on playgrounds. I went looking for clear, honest information I could show people — something between a medical journal and a propaganda poster — and could not find it.

So I started putting the research together myself. Every claim here links to a study. No industry funding, no agenda, no ads.