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PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid)

  • Chelators
  • CAS 37971-36-1
  • IUPAC: 1,2,4-Butanetricarboxylic acid, 2-phosphono-

PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) (CAS 37971-36-1) appears in 1 of the 2,122 car-care products CarCareTruth tracks (as of August 2026).

Skin corrosion/irritation: Not classified. Serious eye damage/irritation: Not classified. Not a component of the product's sole SDS-classified hazard (skin sensitization is attributed to the thioglycolate active, not this chelant).

PBTC is a phosphonate-class chelating agent widely used in water-treatment and cleaning formulations to sequester calcium, magnesium, and iron ions, preventing them from forming visible mineral deposits ("water spots") as rinse water evaporates. It is not itself the iron-reactive active in color-changing wheel cleaners; it is a supporting ingredient that improves rinse-clean appearance.

SDS toxicology data for the pure substance (per ECHA/NLM sources cross-referenced in the SONAX Beast Wheel Cleaner SDS, CAS 37971-36-1): oral LD50 (rat) > 3250 mg/kg, dermal LD50 (rat) > 4000 mg/kg, inhalation LC50 (rat, 4h) > 1979 mg/m3, all indicating low acute toxicity. Not classified for skin corrosion/irritation or serious eye damage/irritation. Aquatic toxicity data (LC50 fish > 1042 mg/l, EC50 algae 140 mg/l, NOEC Daphnia 104 mg/l over 21 days) indicate low aquatic hazard; no bioaccumulation expected.

Not on the OEHHA Proposition 65 list (CAS 37971-36-1 checked against data/prop65/oehha-list.json, 2026-07-30, no match).

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
no
Bioaccumulative
no
Persistent
no
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
4/5
Purpose: Scale/mineral chelant: binds dissolved calcium and other minerals to prevent water-spot formation during rinsing

Common questions about PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid)

What is PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) used for in car care?
Scale/mineral chelant: binds dissolved calcium and other minerals to prevent water-spot formation during rinsing
Is PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) a VOC?
No. PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) is not classified as a volatile organic compound (VOC).
Is PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) on California's Proposition 65 list?
No. PBTC (2-Phosphonobutane-1,2,4-tricarboxylic acid) is not on California's Proposition 65 list.

1 product contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.