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CarCareTruthProducts · Ranked

Cyclotetrasiloxane (D4)

  • Silicones
  • CAS 556-67-2
  • IUPAC: 2,4,6,8-Tetramethyl-1,3,5,7,2,4,6,8-tetraoxatetrasiloctane

Cyclotetrasiloxane (D4) (CAS 556-67-2) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026). It is classified as a VOC.

Low acute toxicity at consumer product concentrations. Classified as an endocrine disruptor in EU regulatory assessments (reproductive effects in animals at high doses). Relevance to trace consumer exposure is debated. No H334 respiratory sensitization classification.

Cyclotetrasiloxane (D4) is a volatile cyclic silicone used as an evaporating carrier in detailing and personal-care formulations. D4 carries stronger EU regulatory classification than its sibling D5 — it has been an ECHA Substance of Very High Concern (SVHC) since 2018 due to its PBT/vPvB environmental profile and endocrine disruption potential. Restricted to <0.1% in EU wash-off personal care products. US regulatory status remains limited.

Health & environment profile

VOC
yes
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
yes
Biodegradable
no
Bioaccumulative
yes
Persistent
yes
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
1/5
Purpose: Volatile cyclic siloxane carrier; evaporates after application leaving a silicone-rich film. Regulatory scrutiny higher than D5 due to stronger PBT/vPvB classification.

Common questions about Cyclotetrasiloxane (D4)

What is Cyclotetrasiloxane (D4) used for in car care?
Volatile cyclic siloxane carrier; evaporates after application leaving a silicone-rich film. Regulatory scrutiny higher than D5 due to stronger PBT/vPvB classification.
Is Cyclotetrasiloxane (D4) a VOC?
Yes. Cyclotetrasiloxane (D4) is classified as a volatile organic compound (VOC).
Is Cyclotetrasiloxane (D4) on California's Proposition 65 list?
No. Cyclotetrasiloxane (D4) 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.