Effect of homolog distribution on the toxicity of alcohol ethoxylates

Previous work established a high correlation between the potential environmental toxicity of oxyethylenated nonionic surfactants and the average degree of ethoxylation. For this reason, it was considered of interest to determine whether a narrow- or broad-range homolog distribution of polydisperse commercial alcohol ethoxylates would influence toxicity. Ethoxylated fatty alcohols, both linear and branched, were synthesized with sodium hydroxide or an unconventional calcium-based catalyst. Toxicity tests were run onDaphnia magna and luminescent marine bacteria. Toxicity of ethoxylated alcohols as a function of type of ethoxylate homolog distribution (narrow or broad) and average degree of polyaddition is analogous for both test species. However, narrow-range ethoxylates show lower toxicity values than conventional ethoxylates. Differences in toxicity values between broad- and narrow-range ethoxylates depend on the degree of ethoxylation.