That part of the image has this link in it https://www.canorml.org/vaporizers/

In that article, the first link to "Study: Vaporizers Deliver Safe, Reliable Doses Of Cannabinoids" works and so do the links it references if you want to go down a rabbit hole. It'll prob explain better somewhere along the way than most people could.

but the second link "Laboratory studies by California NORML and MAPS" goes to a dead page.

From what I can gather, it's largely because you're getting more smoke than vapour at that temperature. But I'm probably wrong.

This chart has been circulating the internet for a long time. However it doesn't accurately cite it's sources for all of this info.

As far as I've been able to deduce, the "Benzene" warning comes from a single study which found benzene gas in the vapor when the herb was cooked.

HOWEVER at the time when that study was conducted, there was only one federally approved supplier of the material for testing, and it came from the The University of Mississippi. If you look into it, you'll see that researchers have complained for YEARS about the quality of the material that came from this farm, they wanted to test better quality material from other suppliers but the Old Miss was the only one federally approved for research.

You can read more about the problem here - https://www.pbs.org/newshour/nation/scientists-say-governments-pot-farm-moldy-samples-no-guidelines

My problem is that since that study only used material from one supplier, who's to say that it wasn't tainted by a grower in the field? Maybe someone was refilling their tractor next to that plant that was plucked for testing?

Moreover, if you read further into the details, you'll see that the study found a very low concentration of benzene in the vapor. Look into how much benzene gas is consumed when you drive down a highway in your car, or walk along a busy highway.

Unfortunately for decades most funding for research studies has been focused on finding negative affects from the plant so that congress could further regulate the plant and lock people up for this "dangerous" plant. Things are finally changing and we're starting to see more government funding for the benefits of cannabis. But there's still a long way to go.

Just my $0.02 on this chart and benzene gas in vapor.

That's definitely worth a post or its own.