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Summary of alkylphenols report
- Alkylphenol ethoxylate surfactants are usually made from a branched-chain nonylphenol or octylphenol, reacted with ethylene oxide. They are used in a variety of industrial processes, including wool washing, but are no longer in domestic detergents in the UK. Alkylphenols are also used by some industries.
- Alkylphenol ethoxylates are biodegraded by removal of ethoxy groups, producing less biodegradable products: alkylphenol mono- and di-ethoxylates, alkylphenoxy acetic and alkylphenoxypolyethoxy acetic acids, and alkylphenols. These metabolites frequently persist through sewage treatment and in rivers. Anaerobic conditions generally lead to the accumulation of alkylphenols.
- Rivers in Switzerland have been found to contain concentrations of tens of µg/1 of a wide range of alkylphenolic metabolites. Low levels have also been found in drinking water in the USA, with a total concentration of alkylphenolic compounds of almost 1 µg/1. There is little UK data on concentrations in the environment, but a recent modelling study concluded that 83 % of UK nonylphenol ethoxylate production enters the environment, with 37 % entering the aquatic environment.
- Metabolites of alkylphenol ethoxylates accumulate in organisms, with bioconcentration factors varying from ten to several thousand, depending on species, metabolite and organ.
- The metabolites of alkylphenol ethoxylates are generally more toxic than the original compounds. Alkylphenol ethoxylates have LC50s above about 1.5 mg/1, whereas nonylphenol LC50s are generally around 0.1 mg/1.
- Alkylphenols were first found to be oestrogenic (oestrogen-mimicking) in the 1930s, but more recent research has highlighted the implications of these effects. The growth of cultured human breast cancer cells is affected by nonylphenol at concentrations as low as 1 µM (220 µg/1), or concentrations of octylphenol as low as 0.1 µM (20 µg/1). Oestrogenic effects have also been shown on rainbow trout hepatocytes, chicken embryo fibroblasts and a mouse oestrogen receptor.
- Studies on UK rivers receiving sewage effluent have shown that an oestrogenic pollutant is present, as male rainbow trout placed in these rivers produce a female egg yolk protein.
- By comparing environmental concentrations, bioconcentration factors and in vitro oestrogenic effect levels, this report concludes that current environmental levels of alkylphenolic compounds are probably high enough to be affecting the hormonal control systems of some organisms. It is also possible that human health could be being affected.
- Some progress has been made in phasing out alkylphenols and alkylphenol ethoxylates, but many industries are still using them.