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.
Indoor air / Measured in people or real products
Scented laundry products put fragrance chemicals into outdoor air: in two homes, limonene (a citrus scent chemical) came out of the dryer vent only when fragranced detergent or dryer sheets were used (up to 14.7 ug/m3), not in the no-product runs.
Moderate evidence.
Caveats
2 homes (Steinemann 2013), single grab samples; undiluted vent air, not a breathing-zone dose. Replicated at much higher magnitude and with a dose-response signal by Goodman et al. 2019 (6 Melbourne homes, before/after switch design): fragranced-detergent vent D-limonene 2.35-118 ug/m3 vs 0.24-0.26 ug/m3 in fragrance-free-only homes, and switching from fragranced to fragrance-free detergent cut vent D-limonene by up to 99.7% (mean 79.1%) within a month. The two studies share one author (Anne Steinemann) and neither ran statistical significance tests, so the combined evidence (8 homes total) stays below strong, but the qualitative and dose-response finding is now cross-country replicated within one research program rather than resting on a single 2-home study.
Source: Steinemann 2013, Air Quality, Atmosphere & Health Link to this fact
Indoor air / Measured in people or real products
Dryer-vent air carried far more of the citrus-scent chemical D-limonene when households used fragranced laundry detergent (2.35-118 ug/m3, mean 33.34) than when they used fragrance-free detergent (0.13-1.50 ug/m3 after switching; 0.24-0.26 ug/m3 in households that never used fragranced detergent).
Moderate evidence.
Caveats
6 Melbourne-area homes, D-limonene only (not the fuller VOC/HAP panel), no statistical significance testing; shares one author (Anne Steinemann) with the earlier 2-home study it builds on, so not a fully independent replication.
Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact
Indoor air / Measured in people or real products
Switching to fragrance-free laundry detergent also reduced D-limonene in the laundry room's own indoor air, not just at the dryer vent, by up to 72.7% (mean 45.8%) within one month.
Moderate evidence: 4 households, single background-air sample per round, no statistical testing.
Source: Goodman 2019, Air Quality, Atmosphere & Health Link to this fact
Indoor air / Measured in people or real products
Every one of 25 fragranced laundry products tested (US and Australian detergents and dryer sheets) emitted a terpene fragrance chemical (such as limonene, alpha-pinene or eucalyptol), while none of 10 fragrance-free laundry products emitted any terpene at all.
Moderate evidence.
Caveats
This paper restates chemical-panel data from Steinemann 2015 and Nematollahi 2018/2019, which are not yet independently checked in this evidence base; treat the 100%-vs-0% split as a secondary report until those primaries are read directly.
Source: Goodman, Nematollahi & Steinemann 2020/2021, Air Quality, Atmosphere & Health Link to this fact
Information, not medical advice. See also: myths we won’t tell you.