Evaluating the sensitization potential of surfactants: integrating data from the local lymph node assay, guinea pig maximization test, and in vitro methods in a weight-of-evidence approach.

An integral part of hazard and safety assessments is the estimation of a chemical's potential to cause skin sensitization. Currently, only animal tests (OECD 406 and 429) are accepted in a regulatory context. Nonanimal test methods are being developed and formally validated. In order to gain more insight into the responses induced by eight exemplary surfactants, a battery of in vivo and in vitro tests were conducted using the same batch of chemicals. In general, the surfactants were negative in the GPMT, KeratinoSens and hCLAT assays and none formed covalent adducts with test peptides. In contrast, all but one was positive in the LLNA. Most were rated as being irritants by the EpiSkin assay with the additional endpoint, IL1-alpha. The weight of evidence based on this comprehensive testing indicates that, with one exception, they are non-sensitizing skin irritants, confirming that the LLNA tends to overestimate the sensitization potential of surfactants. As results obtained from LLNAs are considered as the gold standard for the development of new nonanimal alternative test methods, results such as these highlight the necessity to carefully evaluate the applicability domains of test methods in order to develop reliable nonanimal alternative testing strategies for sensitization testing.

Comparative testing for the identification of skin-sensitizing potentials of nonionic sugar lipid surfactants.

The Local Lymph Node Assay (LLNA) is the preferred test for the identification of skin-sensitizing potentials of chemicals in Europe and is also the first choice method within REACH. In the formal validation, only a very few surfactant chemicals were evaluated and SDS was identified as a false positive. In this study, 10 nonionic sugar lipid surfactants were tested in an LLNA, guinea pig maximization test (GPMT) and human repeated insult patch test. Of the 10 surfactants tested in the LLNA, 5 showed stimulation indices above 3.0. Three of five positive reactions were concomitant with signs of skin irritation indicated by an increase in ear thickness. In the GPMT, all test products were classified as nonsensitizers. In human volunteers, no skin reactions suggestive of sensitization were reported. In conclusion, these results are indicative of the LLNA overestimating sensitization potentials for this category of chemicals. This may in part be due to irritant effects generated by these surfactants. Until suitable nonanimal alternative tests obtain regulatory acceptance, use of other tests, e.g. GPMTs, may in cases be justified. Results such as these need be taken into account when developing nonanimal alternative methods to ensure reliable data sets for method validation purposes.

Application of a weight of evidence approach to assessing discordant sensitisation datasets: implications for REACH.

The local lymph node assay (LLNA) is the assay of choice in European regulatory toxicology. As with other toxicology/sensitisation assays, it has a potential for false results, the anionic surfactant sodium lauryl sulphate (SLS) representing a classic example. In the work reported here, examples of false positives in the LLNA are compared to published "benchmarks" such as SLS. Clear false positives (e.g. oleic acid) are also contrasted with examples where data interpretation is more challenging. As the LLNA will be applicable to >30,000 chemicals under REACH, and in the light of animal welfare considerations to do no more than the absolute minimum of animal testing, results from a single LLNA often represent the only available data on sensitisation. This reinforces the need to ensure data from this assay are interpreted intelligently, using scientific analysis of results and considering the weight of evidence, before decisions are made on which substances should be classified as representing a skin sensitisation hazard. In chemical classes where the LLNA has been shown to be an inappropriate assay other standardised methods (e.g. the Buehler or Magnusson and Kligman guinea pig tests [OECD 406]) should be employed as the first choice assays.

Human health risk assessment of long chain alcohols.

Representative chemicals from the long chain alcohols category have been extensively tested to define their toxicological hazard properties. These chemicals show low acute and repeat dose toxicity with high-dose effects (if any) related to minimal liver toxicity. These chemicals do not show evidence of activity in genetic toxicity tests or to the reproductive system or the developing organism. These chemicals also are not sensitizers. Irritation is dependant on chain length; generally, alcohols in the range C(6-)C(11) are considered as irritant, intermediate chain lengths (C(12-)C(16)) alcohols are considered to be mild irritants and chain lengths of C(18) and above are considered non-irritants. These chemicals are broadly used across the consumer products industry with highest per person consumer exposures resulting from use in personal care products. Margins of exposure adequate for the protection of human health are documented for the uses of these chemicals.

Environmental risk assessment of hydrotropes in the United States, Europe, and Australia.

An environmental assessment of hydrotropes was conducted under the Organisation for Economic Co-operation and Development (OECD) Screening Information Data Sets (SIDS) for High Production Volume (HPV) Program via the Global International Council of Chemical Associations (ICCA) Hydrotropes Consortium. The assessment and its conclusions were presented at a meeting of the OECD member countries in Washington, DC in 2005. The SIDS Initial Assessment Report (SIAR) was accepted by the membership. Their conclusion was "The chemicals in this [hydrotropes] category are of low priority for further work because of their low hazard profile." Hydrotropes are used to solubilize the water-insoluble ingredients of cleaning and personal care products including, for example, powder and liquid laundry detergents, hard-surface cleaners, machine dishwashing rinse aids, hand dishwashing liquids, body washes, shampoos, hair conditioners, and liquid hand and face soaps. Global production equals approximately 46 500 metric tons, a little more than half of which is used in the United States. The 8 chemicals accounted for in the "hydrotropes category" include ammonium, Ca, K, and Na salts that are described by 10 Chemical Abstract Service (CAS) registration numbers. The 8 chemical entities are generally comparable and predictable in their chemical behavior and that measured and/or modeled data for members from one subgroup can be applied to other subgroups and to the hydrotropes category as a whole. The assessment is based on a search for and evaluation of available data on physical­chemical properties, biodegradability, removal by wastewater treatment, and aquatic toxicity. Reliable ecotoxicity and environmental fate data were found for selected members of the category. Partitioning, once released into the environment, and exposure in surface waters were modeled for consumer use and manufacturing scenarios relevant to the United States, Europe, and Australia. The models indicate 99+% of the hydrotropes will partition to water. Furthermore, given the low potential for hydrotropes reaching the terrestrial environment and their lack of persistence or bioaccumulation, the focus of the assessment is on the aquatic environment, specifically the water compartment. Aquatic risks were assessed in each scenario using what is referred to as the PEC/PNEC ratio. The modeled predicted environmental concentration (PEC), accounting for volume released and wastewater treatment, is divided by the predicted no effect concentration (PNEC) derived from the aquatic toxicity tests. The closest a predicted environmental concentration came to the toxicity threshold is 0.125 (or 12.5% of the no effect concentration) and that is for a hypothetical manufacturing facility that produces the entire annual volume of hydrotropes and discharges to a small (10%ile) stream under low flow (7Q10) conditions. PEC/PNEC ratios were considerably smaller for consumer use scenarios. The ratios were 0.0002 for a low flow (7Q10) stream scenario in the United States, 0.026 to 0.089 for regional and local water bodies, respectively, in Europe, and 0.004 to 0.036 for oceans and rivers, respectively, in Australia. In conclusion, aquatic hazard levels are not expected to be reached under exaggerated conditions of manufacture or normal consumer use of hydrotropes. Hydrotropes are neither persistent nor bioaccumulative in the environment.