OECD SIDS AMINE OXIDES SIDS Initial Assessment Report For SIAM 22 Paris, France, 18-21 April 2006 Category Name: Amine Oxides CAS Numbers: 1643-20-5 1-Dodecanamine, N,N-dimethyl-, N-oxide 3332-27-2 1-Tetradecanamine, N,N-dimethyl-, N-oxide 70592-80-2 Amines, C10-16-alkyldimethyl, N-oxides 68955-55-5 Amines, C12-18-alkyldimethyl, N-oxides 2605-79-0 Decanamine, N,N-dimethyl-, N-oxide 7128-91-8 Hexadecanamine, N,N-dimethyl-, N-oxide 2571-88-2 Octadecanamine, N,N-dimethyl-, N-oxide 61788-90-7 Amine oxides, cocoalkyldimethyl 85408-48-6 Amines, C10-18-alkyldimethyl, N-oxides 85408-49-7 Amines, C12-16-alkyldimethyl, N-oxides 61791-47-7 Ethanol, 2,2'-iminobis-, N-coco alkyl derivs., N- oxides 2530-44-1 Ethanol, 2,2'-(dodecyloxidoimino)bis- 14048-77-2 Ethanol, 2,2'-(octadecyloxidoimino)bis- 61791-46-6 Ethanol, 2,2'-iminobis-, N-tallow alkyl derivs., N- oxides 93962-62-0 Ethanol, 2,2'-[(9Z)-9-octadecenyloxidoimino]bis- 3. Sponsor Country: United States 4. Shared Partnership with: Amine Oxides Consortium 5. Roles/Responsibilities of Industry was the main preparer; U.S. EPA was the main reviewer the Partners: Name of industry sponsor or Amine Oxides Consortium consortium Process used Industry coalition conducted a comprehensive literature search, including all generally accepted databases, reference books, unpublished studies and data in company files, and prepared first drafts; U.S. EPA reviewed and edited drafts to achieve a final document. 6. Sponsorship History How was the chemical or The industry coalition agreed to sponsor AOs in the SIDS-ICCA category brought into the program, with the U.S. being the sponsor country. OECD HPV Chemicals Programme ? 7. Review Process Prior to Prepared by industry. Reviewed and edited by U.S. EPA to reach the SIAM: a consensus document. 8. Quality check process: Industry coalition members developed the documents, which were then reviewed by outside third parties. 1 OECD SIDS AMINE OXIDES 9. Date of Submission: September 2006 10. Comments: In addition to the sponsored chemicals above, one supporting substance is included that provides data on the genetic toxicity endpoint: 60729-78-4 1-(methyldodecyl)dimethylamine-N-oxide 2 OECD SIDS AMINE OXIDES SIDS INITIAL ASSESSMENT PROFILE 1643-20-5 1-Dodecanamine, N,N-dimethyl-, N-oxide CAS No. 3332-27-2 1-Tetradecanamine, N,N-dimethyl-, N-oxide 70592-80-2 Amines, C10-16-alkyldimethyl, N-oxides 68955-55-5 Amines, C12-18-alkyldimethyl, N-oxides 2605-79-0 Decanamine, N,N-dimethyl-, N-oxide 7128-91-8 Hexadecanamine, N,N-dimethyl-, N-oxide 2571-88-2 Octadecanamine, N,N-dimethyl-, N-oxide 61788-90-7 Amine oxides, cocoalkyldimethyl 85408-48-6 Amines, C10-18-alkyldimethyl, N-oxides 85408-49-7 Amines, C12-16-alkyldimethyl, N-oxides 61791-47-7 Ethanol, 2,2'-iminobis-, N-coco alkyl derivs., N- oxides 2530-44-1 Ethanol, 2,2'-(dodecyloxidoimino)bis- 14048-77-2 Ethanol, 2,2'-(octadecyloxidoimino)bis- 61791-46-6 Ethanol, 2,2'-iminobis-, N-tallow alkyl derivs., N- oxides 93962-62-0 Ethanol, 2,2’-[(9Z)-9-octadecenyloxidoimino]bis- Chemical Category Name Amine Oxides (AO) Typical structures for amine oxides are as follows: C12 dimethyl amine oxide O N Structural Formula C12 dihydroxyethyl amine oxide HO O N OH SUMMARY CONCLUSIONS OF THE SIAR Category Identification/Justification The justification for grouping the amine oxides (AO) into a category is based on their structural and functional similarity. All of the substances in this category are surfactants, consisting of a polar “head” (the amine oxide) and a relatively inert, hydrophobic “tail” (the long alkyl substituent). The structural variations in the category are three- fold: 1) the nature of the second and third substituents on the amine are either methyl groups or hydroxyethyl groups; 2) the long alkyl chain ranges in length from 8 to 20 carbons; and 3) the long alkyl chain may contain one or two double bonds (i.e. unsaturation) as in C18:1 (oleyl) or C18:2 (linoleyl). Alkyl chain lengths range from 8 to 20 with 12 and 14 being predominant. Average chain lengths for the mixtures are 12.9 to 13.5, with the exception of one tallow-derived compound. The presence of methyl- vs. hydroxyethyl-substituents affects the basicity of the 3 OECD SIDS AMINE OXIDES nitrogen only marginally, and the hydroxyethyl group lends more bulk to the hydrophilic head-group of the surfactant. The length of the longest alkyl substituent does not alter the chemical reactivity of the molecule, but does affect its physical properties. The influence of unsaturation in the alkyl chain (as in CAS Nos. 93962-62-0 Ethanol, 2,2'-[(9Z)-9-octadecenyloxidoimino]bis- and 61791-46-6 Ethanol, 2,2'-iminobis-, N-tallow alkyl derivs., N-oxides) is expected to make the molecule prone to reactions as typical for unsaturated fatty alkyl chains. Nevertheless, their overall chemical behavior fits within that of the group of C8-18 alkyl dihydroxy ethyl amine oxides. Human Health Substantial data exist for mammalian toxicity by in vitro and in vivo testing. Amine oxides are produced, and transported in aqueous solutions that are 25-35% concentration and most tests were conducted with aqueous solutions in that concentration range. Sometimes aqueous formulations were tested where the AO was at lesser concentrations than 25-35%. Whatever concentration were tested, results are reported below for the active ingredient, amine oxide, in mg AO/kg bw for dermal and oral acute toxicity results and mg AO/kg bw/day for repeated dose studies. Toxicokinetic and metabolism studies indicate AO’s are extensively metabolized and readily excreted after oral administration. Amine oxide was readily absorbed dermally by rats, mice and rabbits after 24 to 72 hours of exposure. After 8 hours of dermal exposure, humans absorbed <1%. In rat oral acute toxicity limit tests, no deaths occurred at single doses of 600 mg C AO/kg bw or less (for CAS 10-16 No 70592-80-2). In multi-dose studies, acute oral LD values for rats ranged from 846 mg AO/kg bw to 3873 mg 50 AO/kg bw (both values for CAS No 61788-90-7), with several other AO’s having rat oral LD50’s falling within this range. In single dose acute dermal toxicity limit tests, no deaths occurred at a dose of 520 mg AO/kg bw (CAS No 70592-80-2). This dose was equivalent to 2 mL/kg of a 30% formulation. There were no deaths observed in a rat acute inhalation study to aerosol droplets of a consumer product providing a dose of 0.016 mg AO/L. In a series of studies on rabbits, AO’s of varying chain length showed consistent results and all 1) were not irritating to the skin or eyes at low concentrations (1%), 2) were moderately irritating at 5%, and 3) more severely irritating when tested as produced (e.g., ~30% aqueous solutions). In studies that included rinsing, eye irritation effects diminished with rinsing after 30 seconds of exposure and were slight with rinsing after 4 seconds of exposure. In Draize rabbit eye irritation tests using ~30% AO solutions, rabbits experienced severe to moderate irritation. (The maximum concentration of AO is 10% active in consumer products.) Accidental eye exposure in manufacturing employee incidents and consumer incidents established that eye irritation effects of exposure during manufacturing and use of products containing AO and other surfactants are moderate, transient and reversible There is no indication of skin sensitization for the AO category based on the available animal and human data. In four repeated-dose studies with rats and mice exposed to AO via oral and dermal routes (all with CAS No 70592-80-2), three dermal studies were designed to assess the effect of repeated exposure on skin at maximum doses of 1.5 mg AO/kg-bw/day. Higher doses were tested in a 90-day dietary study with rabbits. No treatment- related clinical chemistry, hematology and histopathological changes were observed. In these studies, LOAELs ranged from 87 to 150 mg AO/kg bw/day with the highest oral NOAEL below the lowest LOAEL as 80 mg AO/kg bw/day. Signs of toxicity observed in the oral study included suppressed mean body weight gain, lenticular opacities and diarrhea; in the dermal studies, local dermal irritation was evident. In five in vitro bacterial (Salmonella) mutagenicity studies, AO shows no evidence of mutagenicity either with or without S9 metabolic activation at concentrations up to 250 ug/plate (higher concentrations caused cytotoxicity). Three in vivo studies investigated clastogenic effects on a close structural analog of the category, 1- (methyldodecyl)dimethylamine-N-oxide including: a mouse micronucleus, a Chinese hamster micronucleus and a Chinese hamster cytogenetics study. These studies were all negative showing no increase in micronuclei or chromosome aberrations. An in vivo mouse dominant lethal assay showed no evidence of heritable effects. Two AOs (CAS No 1643-20-5 and CAS No 3332-27-2) were negative in an in vitro cell transformation assay tested at concentrations up to 20 ug/ml. The carcinogenic potential of amine oxides has been thoroughly investigated in three carcinogenicity studies in rats or mice by dermal, dietary, or drinking water routes. In all cases the substances demonstrated no evidence of a carcinogenic response. No evidence of reproductive toxicity or fertility effects was observed in a study in which rats were given dietary doses of AO in the diet over two generations (CAS No 1643-20-5). No macroscopic or histopathological changes 4 OECD SIDS AMINE OXIDES were attributable to treatment with the test substance. The maternal NOAEL from this reproductive study was >40 mg AO/kg bw/day, which was the highest dose tested. At all treatment levels, the rate of bodyweight gain for the F1 and F2 offspring was reduced during the lactation period, however, this reduction was not greater than 10%. This effect appeared to be dose-related, but was not statistically significant until after weaning in the mid and high dose levels. This was not considered an adverse effect since the body weight change only reached statistical significance when the rat pups were getting the majority of their calories from solid food (Developmental NOAEL >40 mg/kg bw/day). In three developmental toxicity studies via gavage in rats and rabbits (with CAS No 1643-20- 5 & 70592-80-2), effects such as decreased fetal weight or delayed ossification, were most often observed only at maternally toxic doses and were associated with the irritation effects of AO on the gastrointestinal tract. No decreases in litter size, no changes in litter parameters, no malformations or significant differences in skeletal defects were observed at oral doses up to 25 mg/kg bw/day in rats (based on decreased fetal weight at 100 mg/kg bw/day) and >160 mg/kg bw/day in rabbits (the highest dose tested). Environment The chemicals of the amine oxides category do not exist as ‘pure’ substances, but are produced, transported and used as aqueous solutions, typically within a range of 25-35% AO/water. Experimental values for melting points of C10 to C16 amine oxides range from 125 to 136°C. Amine oxides undergo Cope elimination, i.e., the formation of an olefin and a hydroxylamine by pyrolysis of an amine oxide, in the temperature range 150-200°C, thus decomposition is likely to occur before the melting point is reached, and all boiling points are predicted to be far above the decomposition temperature. Amine oxides are not volatile: predicted vapor pressure values are < 4.6E-7 hPa. Amine oxides are highly water soluble – measured values for a C12.6 average chain length is ~410g/L. Although it is impossible to accurately measure an octanol-water partition coefficient for surface-active agents like amine oxides, an octanol-water partition coefficient (Log value) of < 2.7 has been calculated for amine oxides of chain length C14 and below. The predicted atmospheric oxidation half lives are of the order of 5 hours, indicating a relatively rapid atmospheric degradation potential. Amine oxides are removed by conventional sewage treatment systems and biodegrade under aerobic and anaerobic conditions. Of the collected data, four amine oxides meet the “readily biodegradable” OECD criterion, two are “ultimately biodegradable,” and two are “inherently biodegradable.” These studies are conducted on complex mixtures with a high degree of alkyl chain length overlap. Further, biodegradation is not dependent on chain length. Removal of amine oxides in biological wastewater treatment has been studied in laboratory simulation studies (>99.8% removal, OECD 303A study) as well as through monitoring activities in different geographies; the main removal mechanism can be attributed to mineralization and an average removal number of 98% can be assumed as applicable for secondary activated sludge treatment. Level III fugacity modeling, using loading rates for air, soil, and water of 1000 kg/h for each media, shows water receiving compartment receiving 99.5%; the other compartments are negligible. The bioconcentration factor for amine oxides <C14, is predicted to be <87, based on log Kow data, indicating low potential for bioaccumulation in aquatic organisms. Extensive aquatic toxicity data are available for commercially representative amine oxides (C10 to C18) that are single chain length as well as mixtures. Based on hazard data, freshwater green algae are considered the most sensitive species, for acute and chronic endpoints. Acute toxicity is affected by chain length for fish and invertebrates. Chain length affects hydrophobicity, wherein longer chain-lengths increase the rate of uptake and decrease depuration. All but four supporting AO’s have been tested for acute toxicity in fish, daphnia, and algae. The range of acute LC /EC /ErC values based on a review of the aquatic toxicity data on AO were 0.60-32 50 50 50 mg/L for fish, 0.50-10.8 mg/L for Daphnia magna and 0.010-5.30 mg/L for algae. Chronic toxicity data were normalized to a chain length of 12.9 carbon atoms, as this average chain length represents the largest volume product for North America (CAS No 70952-80-2). Chronic toxicity (NOEC, EC20) for an amine oxide of average chain length of C12.9 ranged as follows for the different trophic levels: 0.010-1.72 mg/L for algae, 0.28 mg/L for Daphnia (flow through) and 0.31 mg/L for fish (flow through). These are based on geometric mean values, and a dataset of 21 chronic toxicity studies. Based on a chronic periphyton microcosm bioassay that included 110 taxa of algae (most sensitive species), a NOEC value of 0.050 mg/L was derived when normalized for a C12.9 amine oxide. Exposure For the AO category as a whole, current production is approximately 26,000 metric tonnes in the US (sponsor country), 16,000 tonnes in Europe and 6,800 tonnes in Japan. In the production phase, manufacturing processes have been designed to maximize production yield and minimize potential releases. The potential for human exposure to AO is minimized by a water solubility of 409.5 g/L, having volatility below 4.6E-5 Pa and being produced in aqueous solutions. Engineering controls (e.g., closed system operations, exhaust ventilation, dust collection) and personal protective equipment (e.g., protective clothing, eyewear, and gloves) at manufacturing and 5 OECD SIDS AMINE OXIDES formulation facilities further mitigate worker exposure. No special engineering controls or additional personal protective equipment are uniquely specified for AO. A limited amount of AO in aqueous solution may be released as a dilute solution from washing and rinsing operations in the manufacturing process and is discharged to wastewater treatment. Labeling of consumer products containing AO and other surfactants include warnings of the potential for eye irritation and first aid instructions to rinse with water. Amine oxides are amphoteric surfactants used at active concentrations between 0.1 and 10% in consumer cleaning and personal care products, usually in conjunction with other surfactants. They function as foam stabilizers, thickeners and emollients, emulsifying and conditioning agents in liquid dishwashing and laundry detergents, liquid hard surface cleaners, shampoos, hair conditioners, creams, moisturizers, bar soaps, cleansing and other personal care products. There are no known commercial uses or industrial process intermediate uses of the amine oxides. Data suggest that inhalation of AO-containing products during use will be low. Spray cleaning products containing AO are designed to produce the large particle sizes needed for efficient delivery of the spray to the surface being cleaned. In laboratory simulations with six spray nozzles representing those used in spray cleaning products, less than 0.1% of the total volume sprayed consists of respirable particles (particles under 10 microns in diameter) and air concentrations in the breathing zone are in the 0.13-0.72 mg/m3 range. Based on these data, it is expected that inhalation exposures to AO in respirable particles are low. Results of environmental field monitoring in the United States and the Netherlands indicate that surface water concentrations downstream from sewage treatment plant mixing zones range from <0.1 to <1 µg/L. Results of a four season monitoring program in major urban rivers of Japan found concentrations ranging from non-detect (< 0.01 µg/L) to 0.34µg/L, with a median concentration of 0.04µg/L. RECOMMENDATION AND RATIONALE FOR THE RECOMMENDATION AND NATURE OF FURTHER WORK RECOMMENDED Human Health: This category is currently of low priority for further work. The chemicals in this category present properties indicating a hazard for human health (skin and eye irritation). However, these hazards do not warrant further work as they are related to reversible, transient and non-lasting effects. Nevertheless, these hazards should be noted by chemical safety professionals and users. Environment: The chemicals in this category are candidates for further work. The chemicals in this category have properties indicating a hazard for the environment (aquatic toxicity <1 mg/L for fish, aquatic invertebrate and/or algae). This category is anticipated to biodegrade and has a limited potential for bioaccumulation. Member countries are invited to perform an exposure assessment and, if necessary, a risk assessment. 6 OECD SIDS AMINE OXIDES SIDS Initial Assessment Report 1 IDENTITY Surfactants known as amine oxides (AO) contain even numbered linear alkyl chains ranging from C to C . Also known as fatty alkyl dimethyl AOs, they are usually produced by reacting alkyl 8 20 dimethyl amines with hydrogen peroxide in water. The AOs are produced, transported and used in water solutions, typically at a 25-35% activity level. The AOs are produced and used either as single chain length substances (e.g., C ) or as a mixture of different chain lengths (e.g., C to C ). 12 12 18 The most common AO in commerce is the alkyl dimethyl AO, where the alkyl group contains 10 to 16 carbon atoms, predominately C and C , and the average chain length is C . There is a high 12 14 12.9 degree of overlap between the chain length ranges represented in several AOs that have High Production Volume (HPV) status in one or more OECD country: C alkyl dimethyl AO (CAS 10-16 No. 70592-80-2) and C alkyl dimethyl AO (CAS No. 68955-55-5) predominantly contain the 12-18 C and the C dimethyl AOs (CAS Nos. 1643-20-5 and 3332-27-2, respectively). The other AOs 12 14 in this category include both individual chain length as well as mixed chain length substances. 1.1 Identification of the Substance Category CAS Numbers: 1643-20-5 1-Dodecanamine, N,N-dimethyl-, N-oxide (C AO) 12 3332-27-2 1-Tetradecanamine, N,N-dimethyl-, N-oxide (C AO) 14 70592-80-2 Amines, C10-16-alkyldimethyl, N-oxides (C AO) 10-16 68955-55-5 Amines, C12-18-alkyldimethyl, N-oxides (C AO) 12-18 2605-79-0 Decanamine, N,N-dimethyl-, N-oxide 7128-91-8 Hexadecanamine, N,N-dimethyl-, N-oxide 2571-88-2 Octadecanamine, N,N-dimethyl-, N-oxide 61788-90-7 Amine oxides, cocoalkyldimethyl 85408-48-6 Amines, C10-18-alkyldimethyl, N-oxides 85408-49-7 Amines, C12-16-alkyldimethyl, N-oxides 61791-47-7 Ethanol, 2,2'-iminobis-, N-coco alkyl derivs., N-oxides 2530-44-1 Ethanol, 2,2'-(dodecyloxidoimino)bis- 14048-77-2 Ethanol, 2,2'-(octadecyloxidoimino)bis- 61791-46-6 Ethanol, 2,2'-iminobis-, N-tallow alkyl derivs., N-oxides 93962-62-0 Ethanol, 2,2'-[(9Z)-9-octadecenyloxidoimino]bis- Category Name: Amine Oxides Description: AOs are used in cleaning and personal care products as foam stabilizers, thickeners, emollients, emulsifying and conditioning agents. Primary uses are in liquid hard surface cleaners, laundry and dishwashing detergents, shampoos and hair conditioning products. Molecular Formula: CH3.(CH2)R.N(CH3)2:O Where R is 9-17 Molecular Weight: 237 (70% C : 30% C ) (molecular weight will vary depending on 12 14 structure) 7 OECD SIDS AMINE OXIDES Synonyms: General: dimethyl alkyl amine oxide, AO, DDAO, N,N-dimethyl alkyl amine oxide, amine oxides, fatty alkyl dimethyl amine oxides, ADAO, alkyl dimethyl amine oxide 1643-20-5: Dimethylaurylamine oxide, Dimethyldodecylamine oxide, Lauramine oxide, Lauryldimethylamine N-oxide 3332-27-2: Myristamine oxide, Myristyldimethylamine oxide, N,N-Dimethyl 1- tetradecanamine N-oxide, N,N-Dimethylmyristylamine oxide, Tetradecyldimethylamine oxide 70592-80-5: Alkyl (C ) dimethyl amine oxide, N,N-dimethyl alkyl amine oxide 10-16 68955-55-5: Alkyl (C ) dimethyl amine oxide, N,N-dimethyl alkyl amine oxide 10-18 Category Justification for AOs The AO Consortium has identified fifteen AO substances that are included in this category. The justification for grouping the AOs into a category is based on their structural and functional similarity. All of the substances in this category are surfactants, consisting of a polar “head” (the AO) and a relatively inert, hydrophobic “tail” (the long alkyl substituent). The structural variations in the category are three-fold: 1) the nature of the second and third substituents on the amine are either methyl groups or hydroxyethyl groups; 2) the long alkyl chain ranges in length from 8 to 20 carbons; and 3) the long alkyl chain may contain one or two double bonds (i.e. unsaturation) as in C18:1 (oleyl) or C18:2 (linoleyl). Commercial AOs are either alkyl dimethyl AOs or alkyl dihydroxyethyl AOs which contain 2 methyl groups or 2 hydroxyethyl groups, respectively, attached to the tertiary nitrogen. Alkyl chain lengths range from 8 to 20 (Table 1) with 12 and 14 being predominant. Average chain lengths for the mixtures are 12.9 to 13.5, with the exception of one tallow-derived compound. It should be noted that the nomenclature and CAS identifications for these AOs are based on historical and geographical considerations, not on significant differences in the structure and composition of the commercial substances. Table 1 illustrates the analogous nature of the substances. Typical structures for AOs are as follows: C12 dimethyl AO O N C12 dihydroxyethyl AO HO O N OH 8 OECD SIDS AMINE OXIDES Note: In the structure diagrams, the N-O bond that is typically depicted as double, covalent (N=O), is really a polar coordination-covalent bond (N(+)-O(-)). A tertiary nitrogen atom “shares” two electrons with oxygen; the oxygen is a powerful hydrogen bond acceptor. The AOs and their typical chain length distributions compiled from commercial product information and test articles are shown in Table 1. All names are 9th Collective Index (CI) or CA Index name. Table 1 : Typical Alkyl Chain Length Distribution of AOs in Category (%)* CAS No. Chemical Name Avg. C C C C C C C 8 10 12 14 16 18 20 Chain Length 1643-20-5 1-Dodecanamine, N,N- 0-1 98-100 0-1 12.0 dimethyl-, N-oxide 70592-80-2 Amines, C10-16- <1 41-75 22-51 4-9 <1 12.9 alkyldimethyl, N-oxides 68955-55-5 Amines, C12-18- 0-3 50-64 18-26 9-17 6-14 0-2 13.5 alkyldimethyl, N-oxides 3332-27-2 1-Tetradecanamine, N,N- 2-6 86-97 1-10 14.0 dimethyl-, N-oxide 2605-79-0 1-Decanamine, N,N-dimethyl-, 96-100 0-4 10.0 N-oxide 61788-90-7 Amine oxides, <1-3 64-74 21-30 2-13 <1-9 13.0 cocoalkyldimethyl 85408-48-6 Amines, C10-18- 2 58 24 10 6 13.2 alkyldimethyl, N-oxides 85408-49-7 Amines, C12-16- 0-3 40-62 20-50 9-13 5-9 13.4 alkyldimethyl, N-oxides 7128-91-8 1-Hexadecanamine, N,N- <3 >94 <2 16.0 dimethyl-, N-oxide 2571-88-2 1-Octadecanamine, N,N- <5 >94 <5 18.0 dimethyl-, N-oxide 2530-44-1 Ethanol, 2,2'- > 98 12.0 (dodecyloxidoimino)bis- 61791-47-7 Ethanol, 2,2'-iminobis-, N-coco 5 6 50 19 10 10 13.1 alkyl derivs., N-oxides 61791-46-6 Ethanol, 2,2'-iminobis-, N- 1 4 31 64 tallow alkyl derivs., N- 17.2 oxides** 14048-77-2 Ethanol, 2,2'- > 95 18.0 (octadecyloxidoimino)bis- ** 93962-62-0 Ethanol, 2,2'-[(9Z)-9- > 80 18.0 octadecenyloxidoimino]bis-** *Chain length distributions based on a survey of Industry Consortia members that summarized the relevant data for sponsored materials. This distribution is a condensation of the AOs described by a particular CAS No. that are commercially available. There are some differences in industry nomenclature practice and/or use patterns across geographical regions that, in some cases, lead to differences in how some substances are identified on national and regional chemical inventories. ** The long alkyl chain may contain one or two double bonds (i.e., unsaturation) as in C18:1 (oleyl) or C18:2 (linoleyl) 9 OECD SIDS AMINE OXIDES The chemical behaviors of the AOs are expected to be very similar (Kirk Othmer, 2001). Differences relate to the alkyl substituents: their nature (methyl, hydroxyethyl) and the number of carbon atoms in the alkyl chain (8 to 20). These structural variances impact the physical and chemical properties of these surfactants. The presence of methyl- vs. hydroxyethyl-substituents affects the basicity of the nitrogen only marginally, and the hydroxyethyl group lends more bulk to the hydrophilic head-group of the surfactant and this may have flow-on effects on properties. The length of the longest alkyl substituent does not alter the chemical reactivity of the molecule, but does affect its physical properties. The influence of unsaturation in the alkyl chain (as in CAS Nos. 93962-62-0 Ethanol, 2,2'-[(9Z)-9-octadecenyloxidoimino]bis- and 61791-46-6 Ethanol, 2,2'- iminobis-, N-tallow alkyl derivs., N-oxides) is expected to make the molecule prone to reactions as typical for unsaturated fatty alkyl chains. Nevertheless, their overall chemical behavior fits within that of the group of C8-20 alkyl dihydroxy ethyl AO. These substances share similar physical chemical properties, environmental fate characteristics, ecotoxicity and mammalian toxicity. A data matrix of available studies is presented in Tables 2 and 3. 10