Thanks to the very rapid take-up of the technology in China and India, mobile ad blocking is growing more quickly than predicted, threatening the fastest growing area of ad spend and the business models of Facebook, Twitter and Google.

A new report by PageFair, a provider of ad tech and analytics for publishers, reckons about 419 million (at the end of March) mobile phone owners were using ad blocking technology. The report was prepared in conjunction with app intelligence firm Priori Data. The report claims the use of mobile ad blocking rose 90% last year and is on the way to another surge this year. “There are twice as many mobile adblockers than desktop adblockers,:” PageFair said in its report.

A report earlier last year from PageFair and Adobe examined the rapid growth of ad-blocking technology on PCs, laptops, etc. PageFair and Adobe’s frequently cited August 2015 report, estimated 198 million users of ad blockers on desktop browsers.

But according to PageFair’s latest report, the 419 million figure represents 22% of the world’s 1.9 billion global smartphone users who are blocking ads. The report estimated that 408 million people were actively using mobile ad-blocking browsers (i.e., a mobile browser that blocks ads by default), as of March this year. There were 159 million users of mobile ad-blocking browsers in China, 122 million in India, and 38 million in Indonesia, as of March 2016. Ad blocking on mobiles was not as widespread in Europe and North America, where the report found that there were 14 million monthly active users of mobile ad blocking browsers, as of March this year.

That means in-app ads on platforms such as Spotify, Apple News, and CNN are now vulnerable to ad blocking, along with “suggested” content on Facebook.

Ad blocking is now a huge threat to all mobile channels. “Failure to address user concerns about mobile advertising in North America and Europe will lead to the same kind of widespread ad block usage that we are seeing in the Asia Pacific region,” according to Sean Blanchfield, CEO and co-founder of PageFair. And Australia did not feature in the report.