At a glance
| Chemical family | Branched-chain carboxylic acid — volatile degradation product of foam catalysts (stannous octoate) and adipate plasticizers (DEHA) |
| CAS number | 149-57-5 |
| Classification | Not classified by IARC. EU CLP Repr. 2 (H361d — suspected of damaging the unborn child). Developmental toxicity in animal studies. Also classified Eye Dam. 1 (H318), Skin Irrit. 2 (H315) |
| Where you encounter it | Polyurethane foam off-gassing (from stannous octoate catalyst residue); degradation of DEHA plasticizer; desiccant vapours (cobalt 2-ethylhexanoate driers in paints); new mattress emissions |
| Sleep micro-environment relevance | Emitted from new polyurethane foam mattresses and furniture. EU Repr. 2 classification makes it one of the higher-concern foam VOCs. Relevant to new mattress off-gassing during the break-in period |
Regulatory & certification status
| European Union | CLP Repr. 2 (H361d — suspected of damaging the unborn child). Eye Dam. 1 (H318), Skin Irrit. 2 (H315). REACH registered. No specific indoor air quality guideline. Regulatory |
| United States | No EPA indoor air quality guideline. No OSHA PEL. Not restricted in consumer products. Listed under TSCA inventory. Regulatory |
| Canada | No Health Canada indoor air quality guideline. Under assessment as part of the organic acids group. Regulatory |
| International | Not IARC classified. EU CLP Repr. 2 is the most significant regulatory classification. No WHO indoor air quality guideline. Regulatory |
What it is
2-Ethylhexanoic acid is the free acid form of the 2-ethylhexanoate anion — the same branched C8 carboxylate that forms the basis of stannous octoate (the dominant catalyst in polyurethane foam production) and of many metallic drier compounds used in paints. In the context of foam off-gassing, 2-EHA is released when residual stannous octoate in the finished foam undergoes hydrolysis — the tin-carboxylate bond breaks, releasing the free acid. 2-EHA is also produced by the hydrolysis of DEHA (di(2-ethylhexyl) adipate), a plasticizer used in food wrap and some flexible PVC products. IARC has not evaluated 2-EHA. The EU classifies it as Repr. 2 based on animal studies showing developmental toxicity — skeletal malformations and reduced fetal weight in rats and rabbits at doses well above human exposure levels. The classification reflects a precautionary approach to developmental toxicants.
Where it shows up in bedding
2-Ethylhexanoic acid is emitted from new polyurethane foam mattresses and foam mattress toppers as a volatile by-product of the stannous octoate catalyst used in foam production. Emissions are highest when the mattress is new and decline over the first days to weeks of use (the 'new mattress smell' period). The compound has been detected in chamber studies of new mattress off-gassing alongside other VOCs like acetaldehyde, toluene, and formaldehyde. For the sleep environment, the EU Repr. 2 classification is noteworthy because pregnant women are sleeping on new mattresses during the period of highest emission. The practical recommendation is to air out a new foam mattress in a well-ventilated room for several days before sleeping on it, particularly during pregnancy.
Citations
- Campagnolo, D. et al. (2023). VOCs and Aldehydes in New Mattresses: Emission Chamber Studies. Indoor Air, 33(2): e13228. Source Peer-reviewed
- ECHA. 2-Ethylhexanoic acid — Substance Information. Source Regulatory
- EFSA (2005). Opinion on 2-Ethylhexanoic Acid in Food Contact Materials. Source Regulatory
Frequently asked questions
Is the new mattress smell dangerous?
The 'new mattress smell' from foam mattresses includes several VOCs, one of which is 2-ethylhexanoic acid. The EU classifies 2-EHA as Repr. 2 (suspected of damaging the unborn child). At the trace concentrations emitted from a new mattress, the risk is very low, but as a precaution — particularly during pregnancy — airing out a new foam mattress in a well-ventilated room for several days before sleeping on it is advisable. The emissions decline rapidly with time and ventilation.
Where does 2-ethylhexanoic acid come from in a mattress?
2-EHA is released from residual stannous octoate — the tin-based catalyst used in polyurethane foam production. During foam manufacture, stannous octoate accelerates the reaction between polyol and isocyanate. Not all of the catalyst is consumed in the reaction; the remainder slowly hydrolyses in the finished foam, releasing 2-ethylhexanoic acid as a volatile by-product.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-08. If you find a factual error, contact us.