Esterquats are a widely used class of cationic surfactants. They were introduced in the early 1980s when concerns were raised about the environmental profile of DHTDMAC (Di-Hardened Tallow Di-Methyl Ammonium Chloride) a fabric conditioner. Esterquats are similar to DHTDMAC except that ester links were introduced into the head-group of the molecules, making them more subject to degradation by hydrolysis and greatly facilitating biodegradation. Most, if not all, fabric conditioners marketed in Europe are now comprised of the three Esterquat groups, TEAQ, DEEDMAC, and HEQ ((Z)-2-hydroxy-3-[(1-oxo-9-octadecenyl)oxy]propyltrimethylammonium chloride). They combine a good environmental profile, especially in terms of ready and ultimate biodegradability, with the structural features required for an effective fabric conditioner.
The total volume of Esterquat surfactants used in Europe is estimated to be 130,000 tonnes/year on an active matter basis [HERA, 2004].
Human health assessment
Consumers are exposed to esterquats through their presence in fabric conditioners mainly via the dermal route, but to some minor extent also via the oral route. Skin exposure occurs mainly in hand-washed laundry and through esterquats being present on the fabric of laundry treated with fabric conditioner. Consumers are orally exposed to esterquats through residues in drinking water or eating foods that have taken up esterquats through their presence in surface waters. The maximum total aggregate exposure of consumers to esterquats has been estimated to be 36.9 µg/kg bw/day.
A substantial amount of toxicological studies demonstrate that esterquats are of low toxicity. Esterquats were found to be mildly to moderately irritating to rabbit skin and eyes. The degree of irritation was concentration dependant as dilutions in water resulted in proportionally lower level of irritation. Local dermal effects due to skin contact with esterquat containing handwasing solutions or esterquat residues on skin are not of concern because esterquats are neither considered skin sensitizer nor expected to be irritating under in-use conditions. Accidental eye contact with undiluted esterquat containing fabric conditioner formulation may cause mild irritation which is, however fully reversible shortly after exposure. As other components in the fabric conditioner formulation may contribute to these effects, immediate rinsing with plenty of water is recommended and will mitigate any potential eye irritation effects.
With regard to repeated dose toxicity, existing subacute and subchronic toxicity studies with esterquats coherently demonstrate a low level of systemic toxicity of all types of esterquats. No major clinical effects were observed in any of the studies, even at dose levels up to 1,000 mg/kg bw/day. There is further no information suggesting that esterquats are genotoxic, mutagenic or toxic to the foetus. Although no carcinogenicity study has been conducted with esterquats yet, the absence of genotoxicity and the overall low toxicity of esterquats do not raise any carcinogenicity concern. Likewise, although no multigeneration studies are available, the absence of any effects on gonads in well-conducted subacute and subchronic toxicity studies, does not raise an immediate concern for a possible effect of esterquats on fertility.
For assessing risks associated with human exposure to esterquats in context of their use in fabric conditioner, a conservative NOAEL of 300 mg/kg bw/day was established on the basis of 90-day oral toxicity study with a TEA-based esterquat. The comparison of the aggregate exposure of 36.9 µg/kg bw/day and the NOAEL results in an MOE of 8,100. Taking into account the conservatism in the exposure calculation and the assigned NOAEL for esterquats, this margin of exposure is considered to be large enough to account for the inherent uncertainty of the database and variability of the database.
In summary, the human health risk assessment has demonstrated that the use of esterquats in fabric conditioners is safe and does not cause concern with regard to consumer use.