|Substance Group: Alcohol Ethoxylates|
Alcohol ethoxylates (AE) are a major class of non-ionic surfactants which are widely used in laundry detergents and to a lesser extent in household cleaners, institutional and industrial cleaners, cosmetics, agriculture, and in textile, paper, oil and other process industries.
The presence of AE in household detergents gives rise to a variety of possible consumer contact scenarios including direct and indirect skin contact from its use in laundry detergents, inhalation through the use of spray cleaners and oral ingestion derived from residues deposited on dishes. The aggregate consumer exposure to AE has been conservatively estimated to be at maximum 6.48 µg/kg bw/day.
A substantial amount of toxicological data and information in vivo and in vitro demonstrates that there is no evidence for AEs being genotoxic, mutagenic or carcinogenic. No adverse reproductive or developmental effects were observed. The majority of available toxicity studies revealed NOAELs in excess of 100 mg/kg bw/d but the lowest NOAEL for an individual AE was established to be 50 mg/kg bw/day. This value was subsequently considered as a conservative, representative value in the risk assessment of AE. The effects were restricted to changes in organ weights with no histopathological organ changes with the exception of liver hypertrophy (indicative of an adaptive response to metabolism rather than a toxic effect). It is noteworthy that there was practically no difference in the NOAEL in oral studies of 90-day or 2 years of duration in rats. A comparison of the aggregate consumer exposure and the systemic NOAEL (taking into account an oral absorption value of 75%) results in a Margin of Exposure of 5,800. Taking into account the conservatism in the exposure assessment and the assigned systemic NOAEL, this margin of exposure is considered more than adequate to account for the inherent uncertainty and variability of the hazard database and inter and intra-species extrapolations.
AEs are not contact sensitizers. Neat AE are irritating to eyes and skin. The irritation potential of aqueous solutions of AEs depends on concentrations. Local dermal effects due to direct or indirect skin contact in certain use scenarios where the products are diluted are not of concern as AEs are not expected to be irritating to the skin at in-use concentrations. Potential irritation of the respiratory tract is not a concern given the very low levels of airborne AE generated as a consequence of spray cleaner aerosols or laundry powder detergent dust.
In summary, the human health risk assessment has demonstrated that the use of AE in household laundry and cleaning detergents is safe and does not cause concern with regard to consumer use.
The environmental risk assessment uses the 'sum of toxic units' approach, in which the ratio of the predicted environmental concentration (PEC) of each individual AE homologue to the predicted no effect concentration (PNEC) of that AE homologue is first calculated, and then the sum of these ratios, or 'toxic units', is calculated for all AE homologues used in laundry cleaners and household cleaning products. Thus 230 different AE homologues, with hydrocarbon chain lengths from 8 to 18 and with ethylene oxide chain lengths from 0 to 22, are considered in the AE environmental risk assessment.
The environmental concentrations in river water are determined from measured effluent concentrations from European sewage treatment facilities, using recently developed analytical methods able to measure environmental concentrations of individual AE homologues with hydrocarbon chain lengths from 12 to 18 and ethylene oxide chain lengths from 0 to 18. These homologues cover more than 80% of the tonnage used in laundry cleaners and household cleaning products. Conservative estimates have been made for the concentrations of the other AE homologues, and these are included in the risk assessment. The total local AE concentration in river water receiving sewage effluent (PEClocaldissolved) is 1.01µg/l.
The equilibrium partitioning method has been used to predict the concentrations of the individual AE homologues in river sediment from the river water concentrations. Maximum values for soil concentrations have been estimated from measured concentrations of several representative European sewage sludges. The local sediment, soil, and sewage treatment plant concentrations have been determined as 1.01mg/kg wet sediment, 0.24 mg/kg wet soil, and 9.8 µg/l respectively, with the sewage treatment plant concentration determined from the measured AE effluent concentrations.
Two complementary methods, both based on high quality chronic effects data, are used to determine the toxicity of the AE homologues in river water. The deterministic method uses a recently published QSAR for the species with the best high quality chronic information, Daphnia magna, with an application factor of 10. The probabilistic method uses a chronic QSAR, recently developed using data from 17 different species and an application factor of 1, to predict the NOEC values for each AE homologue. Equilibrium partitioning is then used to determine the toxicity of AE homologues in sediment and soil, with the soil values being supported by acute and chronic single homologue data for some AE homologues.
Two risk assessments, one using the deterministic (D) method and one using the probabilistic method (P), have been carried out for the environmental concentrations of AE used in laundry cleaners and household cleaning products. The resulting risk assessment ratio (PEC/PNEC value) for all the AE homologues in surface water is 0.041 with the deterministic method (D), and 0.024 with the probabilistic method (P). Risk assessment ratios are 0.316(D) and 0.181(P) in sediment, 0.103(D) and 0.068(P) in soil, and 0.007 in the sewage treatment plant, where a simple method assuming the acute data for the most toxic AE mixture applies to all AE has been used. As all the risk assessment ratios are below 1, there is no cause for concern in any of the environmental compartments.
In summary, AE usage in laundry cleaners and household cleaning products is not a cause for concern in the EU environment, as shown by consideration of surface water, sediment, sewage treatment facilities, and soil.