Plastic straws are the target du jour of corporations, retailers, and even states and cities.

But according to a new report from NBC News, the source of our collective energy may be misplaced. The report suggests that the biggest man-made contaminant of the world’s oceans is not plastic straws, or even plastic bags, but cigarette butts.

Cigarette butts are not only ubiquitous, but also their disposal has largely been unregulated, meaning a nearly unlimited number hit the seas. But a number of individuals and organizations are fighting to change that.

Image: WHO

A campaign, the Cigarette Butt Pollution Project, hopes to ban cigarette filters, which are made from cellulose acetate, a type of plastic that can take over a decade to decompose, according to NBC. Of the 5.6 trillion cigarettes that are made with these filters each year, as many as two-thirds are dumped irresponsibly.

The campaign’s founder and public health professor Thomas Novotny explained to NBC that filters provide no health benefits, but rather serve as a marketing tool, while making it “easier for people to smoke.”

And it’s not just committed activists who are aware of the potential damage of the filters—the tobacco companies themselves have reportedly looked into everything from biodegradable filters and distributing portable ashtrays to avoid being held responsible for cigarette litter. But so far, these efforts have fallen flat, with smokers predominantly preferring to flick their cigarette butts.