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Propylene Glycol n-Butyl Ether

  • Glycol ether solvents
  • CAS 5131-66-8
  • IUPAC: 1-Butoxy-2-propanol

H319 (eye irritation) and H336 (drowsiness/dizziness) ingredient-level classifications at high concentrations. Does NOT carry the reproductive-toxicity (H361) or repeated-dose target-organ-toxicity (H373) hazard codes that 2-butoxyethanol does — the propylene-glycol ether family is generally regarded as a less hazardous substitute. At <5% in finished consumer products and water-dilution working strength, ingredient-level hazards are not typically retained at the mixture-level GHS classification.

Propylene glycol n-butyl ether (PnB, sometimes labeled as 1-butoxy-2-propanol or Dowanol PnB) is a glycol-ether solvent commonly used in heavy-duty cleaners and degreasers to dissolve oily soils and help surfactants penetrate greasy films. It is part of the propylene-glycol-ether family, which the cleaning-products industry has broadly adopted as a replacement for ethylene-glycol-ether solvents — most notably 2-butoxyethanol — because the propylene-glycol variants carry a meaningfully cleaner toxicology profile (no H361 reproductive flag, no H373 organ-toxicity flag). It is a VOC under EPA and CARB definitions, so its contribution to total product VOC is tracked. In finished cleaners it typically appears at 1–5% as the active solvent.

Health & environment profile

VOC
yes
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
yes
Bioaccumulative
no
Persistent
no
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
3/5
Purpose: Glycol-ether solvent used to dissolve oily soils and improve surfactant penetration into greasy films; common replacement for 2-butoxyethanol in modern cleaner reformulations

1 product contain this

Health summaries are editorial — we synthesize from SDSs, peer-reviewed sources, and regulatory listings. Not medical advice.