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Alkylphenolic compounds
In January 1995, Friends of the Earth Scotland and Friends of the Earth England, Wales and Northern Ireland jointly published a report which I had written about these compounds, 'An environmental assessment of alkylphenol ethoxylates and alkylphenols' (Warhurst, 1995; ENDS, 1995). The summary and recommendations of this report are available in html format. The full text is now available here in Acrobat format. It can also be purchased, see base of page for details.
This page should be read in association with the introduction page, as some items and recent research are only on that page.
Uses
See Introduction
Fate in the environment
Alkylphenol ethoxylates generally end up at sewage treatment plants, where unfortunately they are only partially degraded, mainly to other alkylphenolic compounds, which then enter rivers and the sea in the treated sewage. A recent modelling study concluded that 83 % of UK nonylphenol ethoxylate production enters the environment, with 37 % entering the aquatic environment (CES, 1993).
When alkylphenol ethoxylates break down in sewage treatment or a river they produce three main groups of alkylphenolic compounds: alkylphenol ethoxylates with fewer ethoxylate groups, alkylphenoxy carboxylic acids and alkylphenols (detailed breakdown pathway here). Extensive research in Switzerland has shown that these compounds persist in rivers and their sediments, and even in groundwater (e.g. Ahel et al., 1994a, b, 1996). Any measurement of pollution in a river must measure all these groups, otherwise only part of the pollution is being measured. Unfortunately all measurement of levels in UK rivers has so far ignored the alkylphenoxycarboxylic acids. As well as the alkylphenoxycarboxylic acids, a range of other carboxylated metabolites have also been identified; analysis of sewage effluents found that these compounds accounted for 63% of total alkylphenolic metabolites (Di Corcia et al., 1998).
Alkylphenolic compounds are concentrated by organisms such as fish and birds, leading to contamination in their internal organs between ten and several thousand times greater than in the surrounding environment.
Another source of nonylphenol ethoxylate contamination to the environment in the UK is the ICI plant at Wilton, Teeside.
Levels in the Environment
Unfortunately very little analysis has been done in the UK, or in many other countries, and no complete analysis (including APECs) of any UK river is yet available (as of December 1998). However, the River Glatt in Switzerland, a river passing through an industrialised area, like many in the UK, has been found to contain concentrations of tens of micrograms per litre of a large range of alkylphenolic compounds (Ahel et al., 1994b).
The River Aire, in Yorkshire, UK, has had some analysis done on it, and has been found to be very heavily polluted, particularly at a sampling point near Bingley (see pathway for an explanation of the abbreviations):
- 180 micrograms per litre nonylphenol and approximately 25 micrograms per litre NP2EO (Blackburn and Waldock, 1995).
- 310 micrograms per litre NP(>3)EO (Yorkshire NRA, personal communication)
Putting these together, you get an alkylphenolic compounds total of 515 micrograms/litre, even without measuring AP1EO, AP3EO, or any APnEC, which are very likely to be present. These figures are already 500 times higher than my suggested safety level of 1 microgram/litre (Warhurst et al., 1995, see recommendations). Denmark has also recently set a water quality criterion of 1 microgram/litre for NP and NPE (ENDS, 1996c). More partial testing of UK rivers has been done in the past year or so, which has demonstrated that many other rivers in the UK are contaminated with alkylphenolic compounds. Tests of treated sewage outfalls in Scotland have measured levels of alkylphenolic compounds of over 1,500 micrograms per litre, excluding alkylphenoxy carboxylic acids (SEPA, 1996).
In the UK, 30% of drinking water is abstracted from lowland rivers, many of which receive treated sewage effluent, there is no publicly-available data on the levels of alkylphenolic compounds in UK drinking water, though it is believed that Thames Water may have had some old unpublished data. Analysis of drinking water in the USA has found a total concentration of alkylphenolic compounds of almost 1 microgram/litre (Clark et al., 1992).
Toxicity of alkylphenolic compounds
Toxicity testing with various organisms including fish and Daphnia has shown that the breakdown products of alkylphenol ethoxylates are generally about ten times more toxic than the original compounds. Concentrations in most UK rivers may be below toxic levels, but insufficient data exists to confirm this. However, the toxicity tests used to determine these toxic levels do not detect oestrogenic effects.
Oestrogenic effects of alkylphenolic compounds
Alkylphenols were first found to be oestrogenic (oestrogen-mimicking) in the 1930s (Dodds and Lawson, 1938), and more evidence was published in 1978 (Mueller and Kim, 1978). However, it was only in 1991 that publication of the effects of nonylphenol on cultured human breast cells led to health concerns (Soto et al., 1991). This and more recent research has shown that the growth of these cells is increased by alkylphenols at concentrations 1000 to 10000 times higher than the oestradiol levels required to produce the same growth. Oestrogenic effects have also been shown on rainbow trout hepatocytes, chicken embryo fibroblasts and a mouse oestrogen receptor (Jobling and Sumpter, 1993; White et al., 1994). Oestrogenic effects are present at tissue concentrations of 0.1 µM for octylphenol and 1 µM for nonylphenol (Soto et al., 1995). A recombinant yeast screen using the human oestrogen receptor has shown similar results (Routledge and Sumpter, 1996).
Majdic et al. (1996) injected pregnant rats with 100 or 600 mg/kg of 4-octylphenol, or 100 or 500 micro-g/kg of DES , on days 11.5 and 15.5 after fertilisation. On day 17.5 the foetal testes were examined, and it was found that the activity of one of the enzymes involved in the synthesis of testosterone, cytochrome P450 17-alpha-hydroxylase, was significantly reduced in foetuses exposed to 600 mg/kg of 4-octylphenol, or 100 or 500 micro-g/kg of DES, when compared with controls. The messenger-RNA for this enzyme was also reduced in the treated animals. These results provide a possible mechanism by which oestrogenic chemicals can affect foetal steroid synthesis and masculinization.
Because alkylphenolic compounds are concentrated by organisms exposed to them, concentrations within the organs of an animal will be higher than those in the surrounding environment. By combining environmental concentrations, bioconcentration factors and the oestrogenic effect levels, my report (Warhurst, 1995) concludes that current environmental levels of alkylphenolic compounds are probably high enough to be affecting the hormonal control systems of some organisms. This conclusion has been confirmed by experiments which have shown that adult male rainbow trout exposed to 30 micro-g per litre of either octylphenol, nonylphenol or nonylphenoxy acetic acid (NP1EC), similar to levels found in UK rivers, produce the female egg yolk protein vitellogenin (Ashfield et al, 1995). Another experiment, examining the effects of exposure to 30 micro-g per litre of OP, NP, NP1EC and NP2EO on male rainbow trout has shown a reduction in testicular growth, and that OP can increase vitellogenin production when present in the water at only 4.8 micro-g per litre (Jobling et al., 1996).
It is already known that if male Rainbow Trout are placed in rivers into which treated sewage flows, for example the River Lea in north-west London, they start to produce a female egg-yolk protein (Purdom et al., 1994). It is believed that alkylphenol ethoxylates may be largely responsible for this effect in UK rivers polluted with industrial effluent (such as the River Aire). However, the oestrogenic effect in domestic effluent has been shown to be due to low levels of the natural female hormones oestradiol and oestrone, with, some of the time, a small contribution from ethinyl oestradiol (the pill) (Desbrow et al., 1996). A survey of wild fish (roach) in UK rivers has found that a high percentage of males had eggs in their testes, in addition to female egg yolk protein in their blood (Jobling et al., 1998).