The risks and alternatives of APEO and NPEO in textiles (1/2)
Introduction
The environmental activist group Greenpeace runs the Detox campaign requesting from international fashion brands to eliminate alkylphenol ethoxylates (APEOs) from their supply chain. In response to the Detox campaign, a group of international retailers has established a roadmap for “zero discharge of hazardous chemicals” (ZDHC) which has the aim of eliminating 11 most critical substance groups between 2013 and 2020. At the present time, strong focus in the ZDHC programme is put on APEOs (alkylphenols and their ethoxylates), in particular on NPEOs (Nonophenol ethoxylates). This report will show the use, the risks and alternatives of APEOs.
What are alkylphenol ethoxylates?
Alkylphenol ethoxylates (APEO) are surface active compounds due to their amphiphilic molecular structure. APEOs belong to the group of non-ionic surfactants, consisting of a branched chain alkylphenol which has been reacted with ethylene oxide, producing an ethoxylate chain. Commercial formulations are usually a complex mixture of homologues, oligomers and isomers. The main alkylphenols used are nonylphenol (NP) and octylphenol (OP), with nonylphenol ethoxylate (NPnEO) taking approximately 80%of the world market, and octylphenol taking the remaining 20%. These products have a large economic relevance. All other alkylphenols are less useful, because the alkyl chain is either too long or too short for a surfactant function. The length of the ethoxylate chain varies between 4 to 20 ethoxy units, depending on the application[1]. Cleaning products usually have a statistical distribution of ethoxylate chain length, centered approximately around 9 (NP9EO) or 10 (NP10EO) units.
For what are APEO are used?
Alkylphenol ethoxylates were first introduced in the middle of the last century. They are used primarily as the raw material basis for washing and cleaning agents. The surfactant properties, such as foaming behaviour, wetting, emulsifying, dispersing and also solubility increase. The properties depend on the degree of ethoxylation[2] – the application depends on the chain length of the ethoxylate chain which is the hydrophilic part of the product. A wetting agent contains mostly 4-5 ethoxylates and a dispersing agent 12-15 ethoxylates.
Use of APEO in textile and leather auxiliaries
In the textile and leather industry APEOs have been used as active substances in all washing processes. On the other hand they have been applied as auxiliaries with emulsifying and dispersing properties. In spite of a German voluntarity renouncement of the use of APEO in cleaning agents in the year 1986, the production volume of APEO used in the textile industry increased from 1997 to 2000 approx. 33%. But the APEO containing products were exported while the domestic consumption in Germany has been declining[3-4]. The wide range of uses has led to a worldwide production of 5 X 105 tons of total APEOs in 2001. Therefore, large amounts of NPEO (and OPEO) are continuously discharged into the environment[5].
Especially textiles cause a big amount of NPEO emissions around the world. These NPEOs are absorbed in the textiles and are washed-off in the (domestic) washing. Without further treatment of the NPEOs, they attain directly into the waste water. Rough estimations of producers and TEGEWA suggest that this path of waste water pollution could cause about 500 t/a NPEO in Germany.
A study from Greenpeace revealed NPEO in textiles of various famous fashion brands, collected in different countries all over the world. The following chart shows the different amounts of NPEs, found before and after washing[6]:
Germany imported approx. 181.000 t/a textiles and Austria approx. 138.000t/a of textiles from all over the world. Based on the Greenpeace study the amounts of NP and NPEO can be estimated which comes with the imported apparel and raw material from Asia and Middle/South America, and is washed of during domestic washing. This is one example why Detox and the ZDHC program requests to avoid any harmful chemicals in the complete textile production chain. With elimination of NPEO from production processes the toxicology problems of these products would be solved for the production sites as well as for the importing countries.
Biodegrability of alkylphenol ethoxylates
Biodegrading is generally understood to be the sum of all processes which reduce the load or contamination of polluting substances in water courses. As soon as biodegrabele pollutants enter a water course the respiration rate increases through the reproduction of microorganisms which are universally available reducing the load or concentration of pollutants. A succession of organisms is therefore build up.
The biodegration of APEOs in the environment has been extensively examined in the USA and Europe. 60% of the APEOs have been estimated to end up in the aquatic environment[7], most entering via sewage treatment plants (STP), where they are really degraded to stable metabolites. Numerous studies have focused on the occurrence and the fate of metabolites in surface water that has been infected with STP effluents, or transformation of APEOs in sewage treatment. Understanding the rates of conversation of APEOs in natural systems and waste water treatment plants (WWTP) is important because the risk of APEO residues are unknown. Figure 1 shows the possible biodegrading pathway of NPEOs, which are very hydrophobic and persistent compounds. Under aerobic conditions APEOs can be biodegraded into APEO residues with shorter ethoxy chains. After formation of shortened ethoxy chain APEOs residues (AP1EO and AP2EO), they can be further transformed by carboxylation of the terminal alcoholic groups to yield the persistent alkylphenol ethoxy carboxylats (APEC, AP1EC and AP2EC). Additionally, a few studies have demonstrated that some oligomers can be halogenated at the benzene ring[8,9].
Under anaerobic conditions, Alkylphenols (APs) are a group of significant APEO metabolites. APs are resistant to further anaerobic biodegrading, which is applied to unacclimated and predigested anaerobic granular sludge at 30 °C under agitated conditions over a 150 days period[10].
Bioaccumulation
APEOs are biodegraded to less biodegradable products, such as shortened ethoxy chain APEO residues, APECs and APs. These metabolites frequently accumulate trough sewage treatment and in the aquatic environment and under anaerobic conditions, generally from persistent APs. They are present near discharges from industrial and municipal wastewater treatment plants (WWTP). NPEOs and their metabolites persist in marine sediments with a half-life of 60 years, and could harm aquatic organism after time at sufficiently high concentrations [12-13].
Nonylphenol is not readily biodegradable and takes month or even longer to degrade in surface waters or in soils and sediments, where it tends to be immobilized. Non-biological degradation is negligible. Bioconcentration and bioaccumulation is significant in water dwelling organisms and birds, where it has been found internal organs at between 10 to 1000 times greater than the surrounding environment. NPs are not broken down effectively in sewage treatment plants and are concentrated in the effluent to surface water or bio accumulates in the eluent sludge[14].
But neither the OECD Screening Test nor the OECD Confirmation Test is any comprehensive protection against strong environmental pollutant surfactants like APEO. This nonionic surfactant fulfill the requirements of these tests, but it has shown that persistent degradation product are build, which are much more fish toxic than the surfactant itself[15].
The results of different analysis show that organisms placed the top of some trophic chains, such as fish, could be affected by the presence of NP in their food. Figure 2 shows the pathways of metabolites of APs and NPs, which may accumulate in the environment.
APs have been detected in surface water and in groundwater, sediment, aquatic organism, wastewater effluent, air, food products and even in human blood and urine. APs are present in all matrices of interest – in water, at ppt to ppb levels; in sediment, at ppb to ppm levels, and in biota samples, at ppb to ppm levels. Biota and sediment samples often contain higher concentrations than aqueous samples. Few data are available on APs input to the atmosphere but its low vapor pressure and tendency to be absorbed by soils and sediments are such that its atmospheric concentrations are expected to be extremely low[16].
Several studies present the concentrations of APs and the shortened ethoxy chain NPEOs, as measured in the surface water around the world[17-23]. The problems of comparability of the results are the parameters, which was measured in the different studies. All studies measured the concentration of para-nonylphenol, but some studies collect also datas of NP1EO, NP2EO or NP3EO, which are intermediates from the decomposition of NPEO to 4-NP.
But the results indicate extensive contamination of rivers by these metabolites. However, insufficient data on the concentration of metabolites of APEOs in other media including, sediments, aquatic organisms and food products are available. Data of the accumulation of these compounds are critical because they pose risks to human health and the environment.
Oestrogenic effect
Their persistent metabolites (i.e. alkylphenols and some metabolites of APEOs) have been reported to mimic natural hormones by interacting with estrogen receptors. 17β-oestradiol (E2) is a hormone, influences the development and maintenance of female sex characteristics, as well as the maturation and function of accessory sex organs. Alkylphenols may mimic the activity of this hormone because they have similar structures. Figure 3 presents chemical structures of E2 and one 4‑nonylphenol isomer[24]:
The most detailed study so far of the oestrogenic effects of APCs has found that 4-OP, 4-NP, 4-NP1EC and 4-NP2EO are able to stimulate vitellogenin gene expression in trout hepatocytes, gene transcription in transfected cells and the growth of breast cancer cell lines.1 This study shows that these effects were due to binding to the oestrogen receptor, since they required the presence of the receptor, and were blocked by oestrogen agonists. OP, NP and NP1EC were all able to compete with oestrogen for binding of the oestrogen receptor. OP was found not to bind a mutant receptor, which also did not bind oestradiol. The oestrogen receptor has two different transcriptional activation functions; OP was found to activate both[25].
Toxicity
APEOs have long polyethoxylates chains which are highly polar molecules with relatively low toxicity toward aquatic organisms. However, the aquatic toxicities of APEOs increase as the length of the polyethoxylate chain decreases, and the biodegradation of APEOs gives less polar but more toxic APEOs. Table 3 lists the toxicities of NPEOs with different EO units to aquatic fauna (mircoorganism), and shows that toxicity increases with shorter ethoxy chain, and 4-NPs are more toxic than NPEOs[26].
Estimated relative toxicity ratios of NP1EO and NP1EC compared to 4-NPs are approximately 0.5 and 0.05 mg/l, respectively, based on a review of acute and chronic toxicity data. This information is valuable and reveals that the hydrophobic moiety of these compounds plays a significant role in their toxicity. Therefore, many studies have focused on the toxicities of APs to aquatic organisms. However, little is known about their effect under actual field conditions[27].
It is necessary to know the concentration of chemical substances in river water to assess the ecological risk to aquatic life in a river. A risk assessment based on observation data only is insufficient, since observation points and frequency are restricted. For this reason, the National Institute of Advanced Industrial Science and Technology (AIST), Japan, develop Standardized Hydrology-based Assessment Tool for Chemical Exposure Load (abbreviated to AIST-SHANEL) to assess and manage the risks of chemical substances for detailed temporal-spatial estimation of the exposure concentration of chemical substances in the entire water system in Japan[28].
This model enables us to visualize the probability of a threshold concentration above which aquatic life is affected. If ecological risks need to be reduced, for instance, it is possible to quantitatively assess to what extent a risk reduction measure will be effective for cutting the concentration of chemical substances, by decreasing emissions by industry and increasing the waste removal rate in sewage treatment plants[27].
Outlook
The second part gives information about product alternatives to APEOs, the global regulations and the environmental advantages after the ban of APEO in Europe. Moreover, the results of the research of Greenpeace about residues of nonylphenol ethoxylates remaining in many clothing items will compared with the joined efforts of the ZDHC project.
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[3]„Alkylphenole, Alkylphenolexthoxylate und ihre Derivate: Massenbilanz, Anwendung, Exposition und Substitutionsmöglichkeiten“, zusammenfassender Ergebnisbericht einer Anhörung durch das Umweltbundesamt am 15.06.1998. Fachgebiet: „Wirkung auf Ökosysteme II 1.3“, Umweltbundesamt Berlin
[4] Hager, C.-D., Persönliche Mitteilung, Sasol Germany GmbH, 2001
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[6] Greenpeace Technical Report: Hazardous chemicals in branded textile products in sale in 27 places during 2012
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[8] Fujita, Y. and Reinhard, M., “Identification of metabolites from the biological transformation of the nonionic surfactant residue octylphenoxyacetic acid and its brominated analog”, Environ. Sci. Technol., 31, 1518-1524, 1997.
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[10] Razo-Flores, E., Donlon, B., Field, J., Lettinga, G., “Biodegradability of N-substituted aromatics and alkylphenols under methanogenic conditions using granular sludge”, Wat. Sci. Tech., 33, 47-57, 1996.
[12] Shang, D. Y., Macdonald, R. W., Ikonomou, M. G., “Quantitative determination of nonylphenol polyethoxylate surfactants in marine sediment using normal-phase liquid chromatography-electrospray mass spectrometry”, J. Chromatogr. A 849, 467-482, 1999.
[14] http://toxipedia.org/display/toxipedia/Nonylphenol+and+Nonylphenol+Ethoxylates
[15] http://www.umweltlexikon-online.de/RUBwerkstoffmaterialsubstanz/Tensidverordnung.php
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[17] Sole, M., Lopez de Alda, M. J., Castillo, M., Porte, C., Ladegaard-Pedersen, K.,Barcelo, D., “Estrogenicity determination in sewage treatment plants and surface waters from the catalonian area (NE Spain)”, Environ. Sci. Technol. 34,5076-5083, 2000.
[18] Tsuda, T., Takino, A., Kojima, M., Harada, H., Muraki, K., Tsuji, M., “4-nonylphenols and 4-tert.-octylphenol in water and fish from rivers flowing into Lake Biwa“, chemosphere, 41, 757-762, 2000.
[19] Bennie, D. T., Sullivan, C. A., Lee, H. B., Peart, T. E., Maguire, R. J., “Occurrence of alkylphenols and alkylphenol mono- and diethoxylates in natural waters of the Laurentian Great Lakes basin and the upper St. Lawrence River”, Sci. Total Environ., 193, 263-275, 1997.
[20] Blackburn, M. A., Kirby, S. J., Waldock, M. J., “Concentrations of alkyphenol polyethoxylates entering UK estuaries”, Mar. Pollut. Bull., 1999, 38, 109-118.
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[22] Snyder, S. A., Keith, T. L., Verbrugge, D. A., Snyder, E. M., Gross, T. S., Kannan, K., Giesy, J. P., “Analytical methods for detection of selected estrogenic compounds in aqueous mixtures”, Environ. Sci. Technol., 33, 2814-2820, 1999.
[23] Ding, W. H. and Tzing, S. H., “Analysis of nonylphenol polyethoxylates and their degradation products in river water and sewage effluent by gas chromatography-ion trap (tandem) mass spectrometry with electron impact and chemical ionization”, J. Chromatogr. A, 824, 79-90, 1998.
[24] Borgert, C. J., La kind, J. S., Witorsch, J. R., “A critical review of methods for comparing estrogenic activity of endogenous and exogenous chemicals in human milk and infant formula”, Environ. Health Perspect., 111,
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[25] White, R., Jobling, S., Hoare, S. A., Sumpter, J. P. and Parker, M. G. ”Environmentally persistent alkylphenolic compounds are estrogenic”. Endocrin. 135: 175-182, 1994
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[27] Servos, M. R., “Review of the aquatic toxicity, estrogenic responses and bioaccumulation of alkylphenols and alkylphenol polyethoxylates”, Water Qual. Res. J. Canada, 31, 123-177, 1999.
