At a glance
| Chemical family | Antineoplastic (chemotherapy) drug — a fluoropyrimidine antimetabolite |
| CAS number | 51-21-8 |
| Classification | IARC Group 3 (not classifiable as to carcinogenicity to humans); listed by NIOSH among hazardous drugs requiring occupational handling controls |
| Who it concerns | Patients receiving the drug, their household members and caregivers, and healthcare workers — not the general public |
| Excretion | Largely cleared in urine within ~24 hours, predominantly as the metabolite FBAL (alpha-fluoro-beta-alanine) |
| Bedroom-specific evidence | Thinner than for cyclophosphamide — detected in healthcare-environment surface contamination, but without a documented sweat-to-textile measurement |
What it is
5-Fluorouracil is a fluoropyrimidine antimetabolite — one of the foundational chemotherapy drugs, used for colorectal, breast, gastrointestinal, and other cancers, and applied topically for some skin conditions. It is a cytotoxic drug and a NIOSH-listed hazardous drug, handled in healthcare with the same occupational-control framework as other antineoplastics. Regulatory — NIOSH, USP <800>
Crucially for an honest atlas, 5-FU is not classified as a carcinogen: IARC places it in Group 3 — not classifiable. Peer-reviewed — IARC, Group 3 That distinguishes it sharply from cyclophosphamide, the IARC Group 1 drug whose body-to-textile transfer is so well measured. 5-FU belongs in the Atlas as part of the antineoplastic-residue picture, but with appropriately lower stakes and thinner bedroom-specific evidence.
How it relates to the bedroom
Excreted mostly in urine, as FBAL
After a dose, a large fraction of 5-FU is cleared in the urine within about a day, predominantly as its metabolite FBAL (alpha-fluoro-beta-alanine). Peer-reviewed — Heggie et al., pharmacokinetics, PMID 3829006 Because the dominant route is urinary rather than dermal/sweat, the contamination that has been measured is mostly surface- and urine-related, and the kind of direct skin-to-clothing transfer documented for cyclophosphamide has not been characterized for 5-FU.
Documented in healthcare-environment contamination
5-FU is one of the antineoplastic drugs tracked in hospital surface-contamination and biological-monitoring studies, which detect it on work surfaces and sometimes in worker urine — the basis for the occupational handling controls. Peer-reviewed — Multi-site biological monitoring, PMID 36981860 By analogy with cyclophosphamide, household surface and linen contamination during the high-excretion window is plausible — but for 5-FU specifically this is inferred, not quantified for bedding. Inferred — household bedding transfer is plausible from the excretion and surface data but not directly measured for 5-FU
The honest limits
We include 5-FU for completeness and because it is a major, NIOSH-listed antineoplastic — but we won't overstate it. It is not a carcinogen by IARC's evaluation, its excretion is mainly urinary, and there is no published sweat-on-textile measurement. The cyclophosphamide page carries the strong body-to-textile evidence; this page is the honest, lower-stakes companion. Speculation — bedroom-specific 5-FU exposure is not quantified
Reducing secondary exposure
These are documented household- and occupational-hygiene measures, not medical advice; patients and caregivers should follow their own care team's instructions.
Follow the care team's household-precaution guidance for the days after a dose, when excretion is highest.
Handle soiled linens with gloves and launder them separately during that window, as with other antineoplastic drugs.
Use washable, wipeable mattress and pillow protectors to limit what reaches the mattress and to ease cleanup.
Routine surface cleaning and ventilation reduce the surface reservoirs that contamination studies measure.
Open research questions
- Whether 5-FU or its metabolite FBAL deposits onto a patient's bedding at measurable levels, as cyclophosphamide does. Speculation
- The household secondary-exposure profile of 5-FU compared with cyclophosphamide, given its mainly urinary excretion. Speculation
Citations
- IARC. 5-Fluorouracil — Group 3 (not classifiable as to carcinogenicity to humans). Peer-reviewed
- NIOSH. List of Antineoplastic and Other Hazardous Drugs in Healthcare Settings (5-fluorouracil listed); USP <797>/<800> handling guidance. Regulatory
- Occupational Exposure to Antineoplastic Drugs in Twelve French Health Care Settings: Biological Monitoring and Surface Contamination. PMID 36981860 Peer-reviewed
- Heggie GD et al. Clinical pharmacokinetics of 5-fluorouracil and its metabolites in plasma, urine, and bile. PMID 3829006 Peer-reviewed
Frequently asked questions
What is 5-FU?
5-Fluorouracil (5-FU) is one of the most widely used chemotherapy drugs, given for colorectal, breast, and several other cancers, and used topically for some skin conditions. This page describes documented secondary (environmental) exposure to the excreted drug — a household- and occupational-hygiene topic. It is not medical advice about cancer or chemotherapy.
Is 5-FU a carcinogen?
Unlike cyclophosphamide (IARC Group 1), 5-FU is classified by IARC as Group 3 — not classifiable as to its carcinogenicity to humans. It is, however, a cytotoxic drug and is listed by NIOSH among hazardous drugs requiring occupational handling controls in healthcare settings.
How is 5-FU excreted?
After a dose, a large fraction of 5-FU is cleared in the urine within about 24 hours, predominantly as its metabolite FBAL (alpha-fluoro-beta-alanine). Because the main excretion route is urinary, the documented environmental contamination is mostly surface- and urine-related, and the patient-to-textile transfer is less characterized than it is for cyclophosphamide.
Does 5-FU end up on bedding like cyclophosphamide?
We are not aware of a 5-FU equivalent of the cyclophosphamide sweat-on-clothing measurements, so the specific bedding evidence is thinner. What is documented is that 5-FU is detected in healthcare-environment surface-contamination studies and excreted heavily in urine, which makes household surface and linen contamination plausible during the high-excretion window — but not quantified for bedding the way cyclophosphamide has been.
Who should take precautions?
Households of patients receiving 5-FU and healthcare workers who handle it — not the general public. The relevant steps are the household-hygiene precautions provided by the care team for the days after a dose: handling soiled linens with gloves, laundering them separately, and routine surface cleaning. Patients and caregivers should follow their own care team's instructions.
Related compounds
This Atlas entry describes documented environmental and secondary exposure science. It is not medical advice; patients and caregivers should follow their care team's guidance. Last reviewed 2026-06-27. If you find a factual error, contact us.