Every fact on this site, with its evidence grade, its caveats, and a link to the source.
We start you on the strong ones: findings that have been replicated or come from one large, well-controlled study. Moderate and weak facts are here too, labeled for what they are. Use “Link to this fact” to share a single card.
Health effects / Hypothesis
A 2019 minireview proposes that frequent, long-term burning of scented candles in poorly ventilated rooms may increase bladder cancer risk, based on chemicals in candle emissions (PAHs, benzo[a]pyrene, formaldehyde, phthalates) that are separately linked to bladder cancer via occupational and other non-candle exposure routes.
Weak evidence.
Caveats
No case-control, cohort, or biomonitoring study has ever tested candle use against bladder cancer; the authors' own conclusion calls for that study to be done. This is a narrative minireview with no original data.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Health effects / Review of other studies
Higher urinary MEHHP (a DEHP phthalate metabolite) was correlated with increased urothelial cancer risk in patients with chronic kidney disease; phthalate esters have also been identified in synthetic candle fragrances.
Weak evidence: Single cohort restricted to chronic kidney disease patients, not the general population; not a candle-exposure study; secondhand citation of Huang & Chou 2018.
Source: Adamowicz 2019, Cancer Prevention Research Link to this fact
Information, not medical advice. See also: myths we won’t tell you.