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.
Fragrance is everywhere / Measured in people or real products
General-population blood styrene levels (US NHANES, general adult population) run in the range of roughly 0.02-0.2 nanograms per milliliter (50th to 95th percentile across several 1988-2008 survey cycles) — two to three orders of magnitude below levels reported in occupationally exposed reinforced-plastics or rubber workers.
Strong evidence: NHANES biomonitoring data; does not by itself establish health risk at these levels, only relative exposure magnitude versus occupational cohorts.
Source: IARC 2019 (Vol. 121) Link to this fact
Health effects / Review of other studies
Chamber studies show irritant gases cause severe airway narrowing in people with asthma at concentrations at or below standard workplace exposure limits: asthmatics had severe bronchoconstriction to sulfur dioxide at about 0.4 ppm (1.1 mg/m3) after just 5-10 minutes of exercise, and to sulfuric acid at about 1 mg/m3.
Strong evidence.
Caveats
Quantified by Johansson 2016 (103-study systematic review): asthmatics showed severe airway narrowing (SRaw >=200%, FEV1 drop >=20%) to sulfur dioxide at >=1.1 mg/m3 (~0.4 ppm) after 5-10 min exercise and moderate-severe responses to sulfuric acid around 1 mg/m3 (oronasal) or 0.35 mg/m3 (mouth-only); both sit at or below typical occupational exposure limits for these substances (e.g. ACGIH SO2 TWA ~2 ppm/STEL 5 ppm; background knowledge, verify against current ACGIH tables). This is now primary chamber data, not only a secondary citation of Baur 2012's occupational-asthma review. Still not specific to fragrance chemicals; these are combustion/industrial irritant gases. Strong for sulfur dioxide and sulfuric acid only; no equivalent chamber data exist for fragrance chemicals, so do not transfer the grade to fragrance.
Source: Kleinbeck & Wolkoff 2024, Archives of Toxicology Industry-funded Link to this fact
Indoor air / Measured in people or real products
In week-long air measurements across 11 European cities, the scent chemicals limonene and alpha-pinene were the compounds most concentrated in homes compared with workplaces (about 4x), attributed to perfumes, cleaning and fragranced products.
Strong evidence: Source attribution by the authors, not measured per product.
Source: Geiss 2011, Atmospheric Environment Link to this fact
The industry / Review of other studies
The cosmetics industry's own safety panel judged PGME 'safe' only for nail products and calculated only skin absorption; it did not estimate how much users or nail-salon workers breathe in, and relied on the smell to limit inhalation.
Strong evidence: Verdict probably right for occasional home users; the weakness is in the reasoning, not a demonstrated harm.
Source: CIR 2008, International Journal of Toxicology Industry-funded Link to this fact
The industry / Review of other studies
All but one author of this fragrance-industry potency review were full-time, fully paid employees of the Research Institute for Fragrance Materials (RIFM) at the time of the work, and the remaining author was paid by RIFM for the time spent preparing the paper — a fully industry-funded and industry-staffed study that sets the potency categories RIFM and IFRA use to justify their own safety limits.
Strong evidence: Disclosed by the authors themselves in the paper's own conflict-of-interest statement.
Source: Na et al. 2022, Dermatitis Industry-funded Link to this fact
Laws and loopholes / Review of other studies
Product safety data sheets are written for workers, not shoppers, and only have to list hazardous ingredients present above 1% (0.1% for cancer-causing ones), a level most individual fragrance chemicals fall below.
Strong evidence: 'Most fragrance chemicals below 1%' is general formulation knowledge, not measured in this paper.
Source: Goldsmith 2014, Food and Chemical Toxicology Link to this fact
Laws and loopholes / Other evidence
A cosmetic product's fragrance-allergen labeling can legally differ between Great Britain and Northern Ireland, because Northern Ireland automatically continues to track EU cosmetics rules under the Windsor Framework (Annex 2's general alignment mechanism for placing manufactured goods on the market) while Great Britain runs its own, separately updated regime.
Strong evidence.
Caveats
Official UK government statutory guidance, updated 29 June 2026, checked directly (accessed 2026-09-28). States the general EU-alignment mechanism for NI, not a specific confirmation that any one EU amendment (such as Regulation 2023/1545) has by name reached NI.
Source: OPSS 2026 (GB/NI guidance) Link to this fact
Laws and loopholes / Other evidence
As of September 2026, Great Britain has not adopted the EU's expanded fragrance-allergen labeling list (Commission Regulation (EU) 2023/1545): the most recent identified GB amendment to the cosmetics regulation's restriction annexes (UK SI 2026/109, made 4 February 2026) addresses unrelated CMR substances, ozone, and a hexyl-salicylate concentration cap, and neither adds to the fragrance-allergen declaration list nor references Regulation 2023/1545, while Northern Ireland continues to track EU cosmetics rules generally under the Windsor Framework.
Strong evidence.
Caveats
Based on this SI's full primary text plus the GB/NI split documented in this batch's other two sources; does not rule out an allergen-list change in one of the five earlier GB cosmetics SIs (2022/659, 2023/836, 2024/455, 2024/1334, 2025/413) named in this SI's own footnote but not independently read here. GB's non-adoption is 'as of' this capture (2026-09-28), not a claim about a permanent decision; industry sources describe an OPSS consultation on alignment as only 'expected.'.
Source: UK SI 2026/109 Link to this fact
Information, not medical advice. See also: myths we won’t tell you.