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The Ministers of Environment and Health have released for final publication the assessment report for the priority substance nonylphenol and its ethoxylates. Notice concerning the assessment of this substance and a summary of its assessment report was published in the Canada Gazette, Part 1 June 23, 2001. The synopsis of the report is provided below.

A draft of this Assessment Report was made available for a 60-day public comment period (April 1, 2000 - May 31, 2000). Following consideration of the comments received, the Assessment Report was revised as appropriate. A summary of the comments and their responses may also be accessed from this page.

For paper copies of the Full Assessment Report, please contact the Inquiry Centre at Environment Canada:

To obtain an electronic version of the Assessment Report in PDF, please request a copy from the following address: ESB.DSE@ec.gc.ca

Synopsis

Nonylphenol ethoxylates (NPEs) are a class of the broader group of compounds known as alkylphenol ethoxylates (APEs). NPEs are high-volume chemicals that have been used for more than 40 years as detergents, emulsifiers, wetting agents and dispersing agents. Nonylphenol polyethoxylate-containing products are used in many sectors, including textile processing, pulp and paper processing, paints, resins and protective coatings, oil and gas recovery, steel manufacturing, pest control products and power generation. A variety of cleaning products, degreasers and detergents are also available for institutional and domestic use. These products have numerous applications, including controlling deposits on machinery, cleaning equipment, scouring fibres, as wetting and de-wetting agents, in dyeing, in machine felt cleaning and conditioning and in product finishing. NPEs are also used in a wide range of consumer products, including cosmetics, cleaners and paints, and in a variety of applications.

NPEs and their degradation products (e.g., nonylphenol [NP]) are not produced naturally. Their presence in the environment is solely a consequence of anthropogenic activity. NP and NPEs enter the environment primarily via industrial effluents and municipal wastewater treatment plant (MWWTP) effluents (liquid and sludge), but also by direct discharge, although it is not known how significant the latter pathway is in Canada. Once NPEs are released to sewage treatment systems, several transformations can occur. The mechanism of degradation is complex, but, in general, there is an initial loss of ethoxylate (EO) groups from the original moiety. Under aerobic and anaerobic treatment conditions, biodegradation to more toxic (and estrogenic) metabolites occurs. These products are NP, nonylphenol ethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), nonylphenoxyacetic acid (NP1EC) and nonylphenoxyethoxyacetic acid (NP2EC).

NPEs can be biodegraded through a mechanism of stepwise loss of ethoxy groups to form lower ethoxylated congeners, carboxylated products and NP. The intermediate and final products of metabolism are more persistent than the parent NPEs, but these intermediates are expected to be ultimately biodegraded. In aquatic environments, primary biodegradation of NPEs is fast, but the resultant products, such as NP1EO, NP2EO, NP1EC, NP2EC and NP, are moderately persistent, especially under anaerobic conditions. Microbial acclimation to such chemicals is required for optimal degradation efficiencies. Photodegradation of such products is also expected to be important. Based on the limited data available, NP and the lower ethoxylates and carboxylates are persistent in groundwater. NP can be moderately persistent in sediments. It appears to be persistent in landfills under anaerobic conditions, but it does not appear to be persistent in soil under aerobic conditions.

NP and NPEs are present at low concentrations in ambient air, water, soil, sediments and biota. There are limited data on the occurrence of NP and NPEs, and their degradation products, in the Canadian environment. Additionally, there are very few data available for NP/NPEs in Canadian soils, including those that have had sludge additions. Nevertheless, in Canada, these chemicals have been found in fresh water, sediment, fish and beluga whale tissue, textile mill effluents, pulp and paper mill effluents, MWWTP influents, effluents and sludges, and soil to which municipal sludges had been applied.

There are a large number of studies reporting acute and chronic effects of NP in aquatic biota. There are, however, fewer studies reporting the toxicity of NPEs, and only a few studies that included the NPECs. Although studies described in the literature have used many species, different test methods and different chemicals, there is a consistent pattern in the toxicity reported. The range of acute toxicity for NP is similar for different organisms: for example, fish (17–1400 µg/L), invertebrates (20–3000 µg/L) and algae (27–2500 µg/L). Chronic toxicity values (No-Observed-Effect Concentrations, or NOECs) for NP are as low as 6 µg/L in fish and 3.9 µg/L in invertebrates. An acute to chronic toxicity ratio of 4:1 was determined based on the available literature.

NP and NPEs have been reported to cause a number of estrogenic responses in a variety of aquatic organisms. Experiments in several different in vitro systems have indicated similar relative potencies among such compounds. NPEs bind to the estrogen receptor, resulting in the expression of several responses both in vitro and in vivo, including the induction of vitellogenin in trout. NP is, however, 100 000 times less potent than estradiol. In one study, NP2EO and NP1EC were only slightly less potent than NP in inducing vitellogenin in trout hepatocytes. NP, NPEs and NPECs are found as complex mixtures in effluents, and their combined estrogenic effects on aquatic organisms should be considered together. A critical consideration is the relative estrogenic potency of the APs and APEs and validation of the assumption of additivity. Estrogenic responses occur at concentrations similar to those at which chronic toxicity occurs, although biochemical and histological changes have been reported at concentrations a factor of 10 lower. The relative importance and significance of estrogenic responses in aquatic organisms to the individual or population are not currently well understood.

The literature suggests that the bioaccumulation of NP and NPEs in aquatic biota in the environment is low to moderate. Bioconcentration factors (BCFs) and bioaccumulation factors (BAFs) in biota, including algae, plants, invertebrates and fish, range from 0.9 to 3400. There are relatively few data available for NPEs, but, based on their structure, the BCF is expected to decrease with increasing chain length, and NPECs are not expected to bioaccumulate.

The major route for the release of NP and NPEs to the Canadian environment is through discharge of effluents. The composition of the mixture can differ considerably among the various effluents, depending on the source and the degree and type of treatment. Textile mill effluents represent a major source of NPEs to the environment. Untreated or partially treated textile mill effluents can have high concentrations of nonylphenol-9-polyethoxylate (NP9EO), NP1EO and NP2EO. There appears to be a recent decrease in discharge of NPEs from pulp and paper mills, but there are very few data available to validate this conclusion. Municipal effluents are a significant source of NPEs and are widespread across Canada. Untreated effluents can have high levels of NP, NP1EO and NP2EO, which may exceed thresholds for chronic effects in the aquatic environment. Treated effluents have relatively low levels of NPEs with longer EO chain lengths. NP1EO and NP2EO can remain at levels that may result in potential chronic toxicity in final effluents. There is potential for chronic toxicity to occur in aquatic biota due to exposure to NPEs and their metabolites in a variety of effluents. This can be associated with different metabolites of NPEs, depending on the source and degree and type of treatment. It is important that all of the NPE metabolites, not only NP, be considered together to assess the potential for impacts in the environment.

The concentration of NP is generally low in treated effluents, as it degrades and sorbs to sludge particles; however, NP sorbed to sediments may represent an alternative route of exposure that may result in chronic toxicity to sediment-dwelling organisms. Despite NP’s relatively low potential to bioaccumulate, sediment-dwelling organisms may be exposed to NP directly, either through contact with water or sediment or through ingestion of sediment or food.

Humans are exposed to environmental media and consumer products that can contain large numbers of different NP/NPEs. The database on both exposure and effects for the individual NP/NPEs that make up these complex mixtures is extremely limited. Consequently, a screening approach has been adopted for the assessment of potential risks to humans from exposure of the general population to this group of substances, primarily to ensure that conclusions drawn on the basis of a more robust data set on effects on environmental organisms are protective with respect to human health, at least for sources controllable under the Canadian Environmental Protection Act, 1999 (CEPA 1999), and to identify priorities for acquisition of additional data. This approach entailed comparison of identified effect levels for NP/NPEs with reasonable worst-case or bounding estimates of exposure for the entire class of substances. The estimated worst-case intake of NP/NPEs in food, the likely principal medium of exposure, is considerably less than the lowest effect level identified, for histopathological effects on the kidneys of male rats exposed to NP in the diet over three generations. (While NP has estrogenic activity in mammalian systems, the results of available studies indicate that this occurs at relatively high dose levels.) The margin between this effect level and estimated dermal intakes from some consumer products is relatively small; however, this comparison is based on the assumption that the NP/NPEs are absorbed through the skin to the same extent as via the gastrointestinal tract, whereas available data, although inadequate, indicate that dermal absorption is likely lower. Therefore, refinement of the assessment presented herein to incorporate, for example, results of additional research into the dermal absorption of these substances is a clear priority for further work to permit more meaningful assessment of exposure to NP/NPEs from these products. NP and NPEs are also likely early candidates for additional investigation when more sensitive frameworks for testing and assessment of endocrine-disrupting substances are developed.

Based on the information available, it is concluded that nonylphenol and its ethoxylates are entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. It is concluded, however, that nonylphenol and its ethoxylates are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger to the environment on which life depends. Therefore, nonylphenol and its ethoxylates are considered to be "toxic" as defined in Section 64 of the Canadian Environmental Protection Act, 1999 (CEPA 1999). On the basis of consideration of the margin of exposure between effect levels and reasonable worst-case or bounding estimates of intake by the general population from environmental media, NP and NPEs are not considered a priority for investigation of options to reduce human exposure through control of sources that are addressed under CEPA 1999. However, the relatively low margin of exposure estimated for some products indicates that there is an important need for refinement of this assessment, in order to determine the need for measures to reduce public exposure to NP and NPEs in products through the Acts under which they are regulated. Of priority in this respect is research into dermal absorption of these substances from such products and evaluation of the potential endocrine-mediated adverse health effects of NP and NPEs upon completion of more sensitive testing.

Under current use patterns, NP and NPEs in Canada can result in environmental concentrations that exceed the levels of concern in textile mill, pulp and paper mill and MWWTP effluents. At present, routine monitoring of these sites for NP/NPEs is not performed. Risk management of NP/NPEs should lead to a reduction in the use and release of these compounds in the processing of textiles and pulp and paper, thereby reducing environmental exposure.

The scope of this Assessment Report as specified by the Ministers’ Expert Advisory Panel on the Second Priority Substances List is limited to nonylphenol and its ethoxylates. However, because of the similar toxicological properties of octylphenol and its ethoxylates (OP/OPEs) and because they are present in similar environmental compartments, relevant data on these compounds have been reviewed in the supporting documentation for environmental effects (Servos et al., 2000). Based on preliminary review of these data, estrogenicity of these compounds in environmental organisms may be greater than that of NP/NPEs. Hence, additional assessment of these compounds under CEPA 1999 will be prioritized. Based on the results of this preliminary review, it should also be recognized that replacement of NPEs with OPEs may amplify rather than reduce the risk to the environment.