The Short Version
The claim is substantively accurate. Multiple peer-reviewed studies confirm that cellulose acetate cigarette filters resist natural biodegradation — with one PMC study recording less than 3% weight loss after 16 weeks in water, and another stating full natural degradation is "almost impossible." Research also documents leaching of nicotine, heavy metals, and over 100 microfibers per filter within days. However, the absolute phrasing "do not fully decompose" slightly overstates the case: one controlled study achieved 100% mass loss within 33 months, and degradation rates vary by environment.