Female journalists and politicians were sent abusive or otherwise hostile tweets every 30 seconds on average in a study released Tuesday by Amnesty International.

For the study, Amnesty, with help from volunteers and global artificial-intelligence software firm Element AI, sorted through 288,000 tweets sent to 778 female politicians and journalists in the U.K. and U.S. last year. They found that 7 percent of tweets they gathered were abusive or otherwise problematic.

Based on that figure, the study extrapolated that 7 percent of all the estimated 14.5 million tweets the women received, 1.1 million, were abusive, hostile or hurtful, which comes to about one every 30 seconds. There are 525,600 minutes in a year.

The study also found that black, mixed-race, Asian and Latina women were mentioned in abusive or problematic tweets 34 percent more often than white women, while black women specifically were targeted 84 percent more often than white women.

"Twitter’s failure to crack down on this problem means it is contributing to the silencing of already marginalized voices," said Milena Marin, a senior research adviser at Amnesty, said in a statement.

The study defined abusive tweets as those that "promote violence against or threaten people" based on race, gender or other identifying factors. It classified as "problematic" tweets that are hurtful and hostile to a lesser degree.

The study, called "Troll Patrol," did not specify how many tweets among the 288,000 were problematic and how many abusive, but Amnesty said Twitter should do more to show the amount of hostile speech on its site and to work to prevent it.

"Amnesty International has repeatedly asked Twitter to publish data regarding the scale and nature of abuse on their platform, but so far the company has failed to do so," Amnesty said in a statement. "This hides the extent of the problem and makes it difficult to design effective solutions."

"Troll Patrol means we have the data to back up what women have long been telling us — that Twitter is a place where racism, misogyny and homophobia are allowed to flourish basically unchecked,” Marin said in Amnesty's statement.

Twitter says on its site that it prohibits abusive behavior and uses both human analysis and artificial intelligence to track violations. It also says it posts removal requests and other findings publicly.

"Twitter has publicly committed to improving the collective health, openness, and civility of public conversation on our service," Vijaya Gadde, a global policy leader for the company said in a statement shared with NBC News.

He also said it was unclear how the Amnesty study categorized tweets as "problematic" or whether the organization was suggesting such posts should be removed from Twitter.

The politicians in the study had diverse affiliations and the journalists were from a broad group of media organizations including The Daily Mail, The New York Times, The Guardian, The Sun and Breitbart. Regardless, the women in the survey received "similar levels of online abuse," according to Amnesty.