As pressure builds on tech giants to clean up their platforms, Google-owned YouTube said it is getting faster at removing problematic videos, and took down 1.7 million entire channels in the third quarter.

The channel removals as well as one-off videos taken down added up to some 58 million videos going dark between July and September, and the company’s report said 74.5% of the videos removed had zero views.

The most common reason for removal — covering about 72% of the videos — was the determination that they were determined to be spam, as was the case for 80% of channel removals. For video removals, the other most common reasons were child safety (10.2%, nudity/sex (9.9%) and violent/graphic content (3.4%).

“We’ve always used a mix of human reviewers and technology to address violative content on our platform, and in 2017 we started applying more advanced machine learning technology to flag content for review by our teams,” the company wrote in a blog post. “This combination of smart detection technology and highly-trained human reviewers has enabled us to consistently enforce our policies with increasing speed.”

In addition to removing the videos and channels, YouTube also took down 224 million comments during the quarter, with automated systems eliminating 99.5% of them.

YouTube has faced scrutiny for being used by a range of bad actors, from white supremacists to ISIS and other terrorist groups, as a recruitment tool. Tech media outlets have also exposed videos in the YouTube Kids arena that show animated characters attempting suicide. Major advertisers, which flocked to digital platforms in recent years due to efficiencies in audience targeting as well as global reach have sometimes found their brands tarnished by appearing next to hate-group screeds or violent crime.

Broadcast and cable TV ad sales chiefs have recently taken to hammering YouTube and fellow digital ad giant Facebook over so-called “brand safety.” NBCUniversal’s Linda Yaccarino has been one of the most emphatic voices on that topic, telling attendees at the companies upfront in May, “We’re not in the ‘likes’ business. We’re in the results business.”

At the same gathering in 2017, Yaccarino said if you’re buying ad time on NBCU platforms, “you never have to worry about your ads showing up next to something objectionable.” She called that “a low bar” that companies like YouTube can’t clear.