June 2001

Alkylphenols and Alkylphenol Ethoxylates:
Highlights of Environmental Safety

This overview is being provided by the Alkylphenols & Ethoxylates Research Council (APERC), which is composed of manufacturers, processors, users and raw material suppliers of alkylphenols (APs), alkylphenol ethoxylates (APEs) and other derivatives. For the past 13 years, APERC and its predecessor organization, the Alkylphenols and Ethoxylates Panel of the Chemical Manufacturers Association, now the American Chemistry Council, have been conducting research studies and providing science-based information regarding the health and environmental safety of APs and derivatives. This overview is part of that effort.

Alkylphenol ethoxylates are highly effective cleaning agents or surfactants that have been widely used for more than 50 years in a number of industrial sectors including textiles, pulp and paper, paints, adhesives, resins and protective coatings. APEs are also used in a variety of cleaning products and detergents for home and institutional use. Alkylphenols, the materials from which APEs are made, are also used to produce high performance products such as lube oil additives, stabilizers for rubbers and plastics, dispersants, emulsifiers and plasticizers for resins. APs used to produce APEs consist primarily of nonylphenol (80%) and octylphenol (most of the rest). Because of the importance of these materials and their uses, a large amount of scientific research has been conducted, and continues to be conducted, on the safety of these materials for human health and the environment. In 1998, The Alkylphenols & Alkylphenol Ethoxylates Review provided an overview of the key studies on APEs up to that time. This overview focuses on the key scientific studies published since.

The studies are grouped by topics related to the environmental safety of APs and APEs: biodegradation, levels in the environment, environmental effects concentrations and safety assessment. These studies demonstrate:

1. APs, APEs and APE biodegradation intermediates are highly biodegradable materials.
   
2. APs, APEs and APE biodegradation intermediates are effectively treated (biodegraded and/or removed) in well-functioning sewage treatment plants.
   
3. Levels of these materials in the aquatic environment from discharge of effluents of well-functioning sewage treatment plants are low -- lower than the levels at which any environmental effects have been observed.
   
4. Current uses of APs and APEs do not generally pose a risk to the aquatic environment, especially where modern sewage treatment practices are employed.
   
5. APs, APEs and APE biodegradation intermediates biodegrade in a wide variety of soils, including agricultural and non-cultivated soils in both temperate and Arctic regions. Consequently, residual levels of APs, APEs and APE biodegradation intermediates present in sewage solids (sludge) will continue to biodegrade when sludge is applied to soil as a fertilizer.
   
6. If sewage sludge is used to make compost, greater than 96% of the residual APEs biodegrade during composting.

Biodegradation

• C.A. Staples et al. ("Measuring the biodegradability of nonylphenol ether carboxylates, octylphenol ether carboxylates and nonylphenol," Chemosphere, vol. 38, pages 2029-39, 1999) examined the biodegradability of five biodegradation intermediates (NPEC1, NPEC2, OPEC1, OPEC2 and NP) of APEs using standard (OECD) biodegradation test methods that model rivers receiving treated sewage. All five of the intermediates show greater than 60% biodegradation to CO₂ or oxygen consumption (mineralization) in the 28-day test period. The results show that common biodegradation intermediates of APEs rapidly biodegrade under rigorous test conditions, strongly suggesting that they do not accumulate or persist in the environment.

• E. Topp and A. Starratt ("Rapid mineralization of the endocrine-disrupting chemical 4-nonylphenol in soil," Environmental Toxicology and Chemistry, vol. 19, pages 313-8, 2000) examined the biodegradation of nonylphenol in agricultural and non-cultivated soils from temperate and Arctic regions. Such soils may be exposed to nonylphenol from use of sewage sludge, which may contain residual levels of nonylphenol, as a fertilizer or soil conditioner. The results of the study showed rapid mineralization of the nonylphenol in the six soils tested, including two soils from the Canadian Far North which presumably had not been previously exposed to this substance. The authors conclude that nonylphenol "should be generally biodegradable in well aerated arable soils."

• F.W. Jones and D.J. Westmoreland ("Degradation of nonylphenol ethoxylates during the composting of sludges from wool scour effluents," Environmental Science and Technology, vol. 32, pages 2623-27, 1998) report on the biodegradation of nonylphenol ethoxylates and their biodegradation intermediates during the composting of sludge from treatment (flocculation) of wastewater from the cleaning of raw wool. This sludge contains practically all of the residual detergent, most commonly nonylphenol ethoxylates, from the wool cleaning. In the composting process, the sludge is mixed with shredded municipal tree and shrub prunings and incubated at ambient temperature for 14 weeks. The results of the study show that during the composting process, greater than 96% of the nonylphenol ethoxylate residuals are biodegraded. Nonylphenol, a biodegradation intermediate, is biodegraded at a rate about half of that of the nonylphenol ethoxylates.

• R.J. Maguire ("Review of the persistence of nonylphenol and nonylphenol ethoxylates in aquatic environments," Water Quality Research Journal of Canada, vol. 34, pages 37-78, 1999) reviews the available information on the treatability of nonylphenol ethoxylates and nonylphenol in sewage treatment plants and their biodegradation in the environment. The report concludes that nonylphenol ethoxylates can be biodegraded in sewage treatment plants and in natural environments, but that some of the biodegradation intermediates, including nonylphenol, are slower to biodegrade than the parent surfactants. These biodegradation intermediates are found in receiving waters of sewage treatment plants. Nonylphenol in particular is found at high concentrations in some sewage sludges that may be spread on agricultural soils as a fertilizer.

  The report notes that the removal efficiency of sewage treatment plants for nonylphenol ethoxylates and their biodegradation intermediates varies considerably depending on the load of surfactants to the treatment plant, its design and operating conditions and other factors such as temperature of treatment. The highest removal efficiencies were observed in the most efficient treatment plants, plants characterized by low sludge-loading rates and nitrifying conditions.

  In natural waters, nonylphenol ethoxylates are not persistent but some biodegradation intermediates may have moderate persistence, especially under oxygen deficient (anaerobic) conditions. Results from laboratory studies indicate moderate persistence of nonylphenol in sediments, with biodegradation rates (half-lives) of 28 to 104 days.

  Based on limited data, nonylphenol and other biodegradation intermediates are not persistent in soils but appear to be persistent in groundwater (which may have low levels of biodegradation organisms present and low oxygen levels) and in landfills under anaerobic conditions.

Levels in the Environment

• D.T. Bennie ("Review of the environmental occurrence of alkylphenols and alkylphenol ethoxylates," Water Quality Research Journal of Canada, vol. 34, pages 79-122, 1999) reviewed the extensive data available quantifying the levels of APEs and their biodegradation intermediates in environmental samples including raw sewage, treatment plant effluent and sludge, receiving waters and sediments. The report notes that most reported observations of APs and APEs are in conjunction with sewage treatment plants and their receiving waters. For instance, one of the earliest reports (from the late 1970s) of nonylphenol and octylphenol in river water (Delaware River, USA) was in conjunction with an industrial discharge of very high levels of these materials (600 micrograms per liter, µg/L, nonylphenol; 2000 µg/L octylphenol). Recent analysis of more representative sites in the US indicate nonylphenol levels of less than 0.1 to 0.6 µg/L in river water and from less than 0.003 to 3.0 µg/g (dry weight) in sediments. Nonylphenol levels in Canadian river water are similar (less than 0.01 to 0.9 µg/L) except for samples from the early 1980s of a single stream (Canagagigue Creek) in which nonylphenol had been spilled. Nonylphenol levels in Canadian river sediments are also similar to US levels except samples (containing up to 72 µg/g dry weight) from Hamilton Harbor (Lake Ontario) near the discharge of the Burlington sewage treatment plant.

  Reported environmental levels of APEs and other APE biodegradation intermediates are also summarized. Nonylphenol monoethoxylate levels in North American rivers, lakes and harbors ranged from less than 0.02 to 7.8 µg/L in water samples and from less than 0.002 to 38 µg/g dry weight in sediment samples. Highest levels were again from Hamilton Harbor. Nonylphenol diethoxylate levels in North America ranged from less than 0.02 to 10 µg/L in water samples and from less than 0.02 to 6.0 µg/g dry weight in sediments, again with Hamilton Harbor having the highest levels. Levels of the very water-soluble ether carboxylate intermediates, nonylphenoxyacetic acid (NPEC1) and nonylphenoxyacetic acid (NPEC2) ranged from not detectable to 2.0 µg/L and from not detectable to 12 µg/L, respectively, in US river water samples. Levels of nonylphenol ethoxylates with 3 to 17 ethoxylate units range from less than 1.6 to 15 µg/L in US river water samples.

  Octylphenol levels in Canada ranged from less than 0.005 to 0.5 µg/L in water samples and less than 0.005 to 1.8 µg/g in sediment samples. (As might be expected based on relative production volumes, these levels are lower than corresponding nonylphenol levels.)

  Follow-up studies of Hamilton Harbor indicate that the environmental distribution of NP, OP and nonylphenol mono- and diethoxylates in sediments is localized in areas close to the point of sewage treatment plant discharges (E.R. Bennett and C.D. Metcalfe, "Distribution of degradation products of alkylphenol ethoxylates near sewage treatment plants in the lower Great Lakes, North America," Environmental Toxicology and Chemistry, vol. 19, pages 784-792, 2000). Concentrations in sediments were found to decrease rapidly with distance from the treatment plant outflows.

  Similar or sometimes higher concentrations (apparently depending on the sewage treatment plant operating efficiencies) of APs, APEs and APE biodegradation intermediates have been reported in Western Europe.

• Two recent studies (C. Desbrow et al., "Identification of estrogenic chemicals in STW effluent. 1. Chemical fractionation and in vitro biological screening," Environmental Science & Technology, vol. 32, pages 1549-58, 1998; E.J. Routledge et al., "Identification of estrogenic chemicals in STW effluent. 2. In vivo responses in trout and roach," Environmental Science & Technology, vol. 32, pages 1559-65, 1998) have concluded that the observation in Britain of estrogenic activity in sewage treatment plant effluents and rivers can be attributed to the presence of natural and pharmaceutical human hormones, not alkylphenols or their derivatives. In the early 1990s, hormonal, specifically estrogenic, activity for fish was discovered in sewage treatment plant effluents and receiving waters in the UK. Since some APs and APE biodegradation intermediates have estrogenic activity in laboratory studies, the finding of estrogenic activity in sewage treatment plant effluents raised the question of the origin of this activity. Using a nonspecific analytical system, C. Desbrow et al. identified natural (estradiol and estrone) and, at lower levels, pharmaceutical (ethynylestradiol) hormones from human waste as the estrogenically active compounds present in effluents of sewage plants treating primarily domestic wastes. In a follow-up study, the same group of authors (E.J. Routledge et al.) demonstrated that the observed levels of estradiol and estrone were adequate to cause the estrogenic effects observed in fish exposed to sewage treatment plant effluents.

Environmental Effects Concentrations

• C.A. Staples et al. ("Evaluation of aquatic toxicity and bioaccumulation of C8- and C9-alkylphenol ethoxylates," Environmental Toxicology and Chemistry, vol. 17, pages 2470-80, 1998) review the extensive aquatic toxicity database on APs, APEs and APE biodegradation intermediates. Data is reviewed and summarized for freshwater and saltwater aquatic organisms, algae, invertebrates and fish inhabiting cold and warm water bodies and includes results from both short term (acute) and long term (chronic) exposures. For typical commercial APEs having an average of 9 to 10 ethoxylate units, acute toxicity values range from 1,000 to 10,000 µg/L. For APs, acute toxicity values range from about 20 to 3,000 µg/L. Chronic values are a factor of about 2 to 10 lower. Data from both laboratory and field studies indicate that APs have a low to moderate potential to accumulate in the food chain. These data provide an extensive and useful database for environmental safety assessment (see below).

• M.R. Servos ("Review of the aquatic toxicity, estrogenic responses and bioaccumulation of alkylphenols and alkylphenol polyethoxylates," Water Quality Research Journal of Canada, vol. 34, pages 123-177, 1999) also reviews the aquatic toxicity data on APs, APEs and APE biodegradation intermediates. Nonylphenol and octylphenol have acute toxicity values for fish, invertebrates and algae ranging from 17 to 3,000 µg/L. In chronic toxicity tests the lowest no-observed-effect concentrations are 6 µg/L in fish and 3.7 µg/L in invertebrates. Among APEs, there is a decrease in toxicity with increasing ethoxylate chain length. The APE biodegradation intermediates nonyl- and octylphenol ether carboxylates are less toxic than corresponding APEs and have acute toxicities similar to APEs with 6 to 9 ethoxylate units.

  APs and APEs (with short ethoxylate chains) bind to the estrogen hormone receptor resulting in the expression of several responses both in test tube (in vitro) and live animal (in vivo) studies, including the induction of the egg yolk protein (vitellogenin) in male fish. The threshold for vitellogenin induction in fish is 10 µg/L for nonylphenol and 3 µg/L for octylphenol (similar to the lowest no-observed-effect concentrations). At higher concentrations, these materials also affect the growth of testes, alter normal steroid metabolism, disrupt smoltification and cause intersex (ova-testes) in fish.

  The literature review suggests that the ability of APs and APEs to bioaccumulate in aquatic organisms in the environment is low to moderate.

Safety Assessment

• C.A. Staples et al,. ("An environmental risk assessment of the biodegradation intermediates of nonylphenol ethoxylates," Proceedings of the 4th World Conference on Detergents: Strategies for the 21st Century, A. Cahn, ed., AOCS Press, Champaign, Illinois, 1998, pages 298-303) have reported an environmental safety assessment for the major nonylphenol ethoxylate biodegradation intermediates, including nonylphenol. The safety assessment was conducted by comparing predicted exposure concentrations (PECs) in water and sediments for North America and Europe (1989-1998) with calculated predicted no effect concentrations (PNECs) for each material.

  PNEC values for nonylphenol in water were calculated using two approaches: 1) the US Environmental Protection Agency procedure for calculating water quality criteria; and, 2) the European technical guidance document method for calculating a hazard concentration at the 5th percentile. Both assessments are aimed at protecting environmental ecosystem structure and function by protecting at least 95% of the individual species of organisms present.

  The calculated PNEC values for nonylphenol ranged from 2.8 to 9.1 µg/L. PNEC values for nonylphenol monoethoxylate (NPE1), nonylphenol diethoxylate (NPE2) and the ether carboxylates NPEC1 and NPEC2 were calculated from the ratios of the acute and chronic toxicity data for these materials in the most sensitive aquatic organism, the invertebrate Ceriodaphnia, compared to the data for nonylphenol in that same organism. PNEC values for sediments were calculated for the corresponding aquatic values conservatively assuming the organic carbon content of sediment is 1% and using a sediment partition constant of 22,000 L/kg.

  Comparing PECs to these PNEC values reveals that measured surface water concentrations of nonylphenol for three of five UK rivers, three of four Swiss rivers, 38 US rivers and all 35 locations sampled in Canada are lower than the predicted no effect concentrations. All surface water concentrations of NPE1, NPE2, NPEC1 and NPEC2 are lower than the predicted no effect concentrations. All the surface water sites at which the PEC exceeded the PNEC were reported near large-scale sewage treatment plant effluent discharges (outfalls) or in streams receiving inadequately treated discharges.

  Similarly, 17 of 23 sets of measured sediment concentrations of nonylphenol, NPE1 and NPE2 (sediment levels of the very water-soluble NPEC1 and NPEC2 have not been reported) are all lower than the PNECs. Sediments with high concentrations of nonylphenol, NPE1 or NPE2 that exceed their PNECs were known or reported to be near highly polluted areas such as urban/industrial treatment plant outfalls and hazardous waste sites.

  This preliminary safety assessment of recent surface water and sediment concentrations of nonylphenol, nonylphenol ethoxylates and nonylphenol ethoxylate biodegradation intermediates concludes that these materials do not generally pose an adverse risk to the environment.

   
  

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