The phrase "about how harmful" is correct and usable in written English.
It can be used when discussing the negative effects or consequences of something, often in a context of analysis or evaluation.
Example: "The report focuses on the debate about how harmful social media can be to mental health."
Alternatives: "regarding the harmful effects" or "concerning the damage caused".
I've spent the better part of the past year attempting to debunk every viral hoax that comes down the pike and yelling at anyone who'll listen about how harmful the internet's viral bullshit culture is to the way we consume, and produce, news and surprise surprise, it's been a thankless and ultimately fruitless pursuit.
But on the other, and just about as quickly, knowledge continues to expand about how harmful lead is in the ever smaller amounts that remain.
Second, all the moral "cluck-clucking" about how harmful this dishonesty is does nothing — or maybe even less than nothing — to change anything.
Even now, there is debate about how harmful the dust was, and whether it could cause cancer or debilitating chronic diseases, although there is emerging medical consensus that workers who arrived at ground zero early and stayed longest were at greatest risk of getting sick.
Inconsistencies also remain about how harmful red meat really is.
I've been thinking about how harmful labels are like the word "feminist". Obviously, as a woman, you want women and men to be equal, but so many people get turned off by the word even though the definition just means that you want women and men to have equal rights.
Fewer and fewer young people are trying cigarettes, perhaps because the message about just how harmful they are is finally being not just heard, but heeded.
While throwing a helpless cat out the window depicted the awfulness of Dafoe's character in "The Grand Budapest Hotel," Anderson allows that symbolism to encompass the entire movie this time around, presenting us with a lesson about the how harmful fear of the "other" can be.
Everywhere (Facebook, Twitter, blogs, respectable news sites, gossipy web pages, you name it), there have been headlines about how hugging your dog is harmful and wrong! wrong! wrong! Cute pups educate us on five different embraces.
He says he wanted to make a point about religious doctrine and how harmful it can be.
Try getting him more information about smoking and explaining to him how harmful smoking is.
