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Abstract

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of 6 trimellitic anhydride copolymers as used in cosmetics. These ingredients are related as copolymers in that they all share trimellitic anhydride (ie, 1,2,4-benzenetricarboxylic acid anhydride) as a monomer, are reported to function as film formers in cosmetics, and are reported to be primarily used in nail products. Very limited safety data were available or submitted. The Panel concluded that Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer are safe in nail product formulations in the present practices of use and concentration, but the data are insufficient to make a determination of safety on the use of these 2 ingredients in all other types of cosmetic formulations. The Panel also concluded that the available data are insufficient to make a determination that the remaining trimellitic anhydride copolymers are safe for use in cosmetic formulations.

Keywords

cosmetics safety trimellitic anhydride copolymers

Introduction

This assessment pertains to the safety of the following 6 trimellitic anhydride copolymers as used in cosmetic formulations:

Adipic Acid/CHDM/MA/Neopentyl Glycol/Trimellitic Anhydride Copolymer

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

Isostearoyl Trimellitic Anhydride/Trimethylolpropane Copolymer

Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer

Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer

Trimethylpentanediol/Isophthalic Acid/Trimellitic Anhydride Copolymer

According to the International Cosmetic Ingredient Dictionary and Handbook (Dictionary), most of the trimellitic anhydride copolymers are reported to function as film formers in cosmetic formulations¹ (Table 1).

Table 1.

Definitions and Reported Functions^{1, CIR Staff}.

Ingredient (CAS No., if available)	Definition	Function(s)
Adipic Acid/CHDM/MA/Neopentyl Glycol/Trimellitic Anhydride Copolymer (67970-02-9)	A copolymer of adipic acid, cyclohexanedimethanol (CHDM), maleic anhydride (MA), neopentyl glycol and trimellitic anhydride monomers	Film former
Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer (28407-73-0)	A copolymer of adipic acid, neopentyl glycol and trimellitic anhydride monomers	Film former
Isostearoyl Trimellitic Anhydride/Trimethylolpropane Copolymer (1190965-82-2)	A copolymer of trimellitic anhydride and trimethylolpropane chain-terminated by isostearic acid.	Skin protectant; skin-conditioning agent—emollient; skin-conditioning agent—miscellaneous
Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer (186688-25-5)	A copolymer of phthalic anhydride, trimellitic anhydride, ethylene glycol, and neopentyl glycol monomers	Film former; viscosity increasing agent—nonaqueous
Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer	A copolymer of propylene glycol, sebacic acid and trimellitic anhydride	Film former
Trimethylpentanediol/Isophthalic Acid/Trimellitic Anhydride Copolymer	a copolymer of trimethylpentanediol, isophthalic acid and trimellitic anhydride monomers	film former; viscosity increasing agent—nonaqueous

Abbreviation: CHDM, cyclohexanedimethanol.

The ingredients in this report are related as copolymers in that they all share trimellitic anhydride (ie, 1,2,4-benzenetricarboxylic acid anhydride) as a monomer. Each copolymer is also composed of 1 to 4 of the following additional monomers: adipic acid, cyclohexanedimethanol (CHDM), ethylene glycol, isophthalic acid, maleic anhydride, neopentyl glycol, phthalic anhydride, propylene glycol, sebacic acid, trimethylpentanediol, or trimethylolpropane (chain-terminated by isostearic acid).¹ Relevant information on the toxicity of these monomers is presented in Table 2.^{2

–31} This information is not intended to be exhaustive or complete, but purely summary information intended to provide insight as to any possible toxicity concerns for these monomers.

Table 2.

Monomer Safety Data.

Monomer (CAS No.)	Summary Information	Reference
Trimellitic anhydride (552-30-7)	Molecular weight: 192.13 g/mol Toxicokinetics: rapidly converted to trimellitic acid in the body (complete hydrolysis likely occurs in <10 minutes); in rats exposed to 0.95 mg/m³ for 45 minutes and killed 3 hours or 1, 2, 4, 8, 16, and 32 days following exposure, in general, the highest tissue concentrations were obtained at the first time point (T-max <3 hours), and a second T-max of 8 days was reported for lung lymph nodes in male rats, suggesting a possible role in the gender differences observed for lung toxicity; the biological half-life in the lungs was estimated to be 21 days in male rats and 16 days in female rats, and in lung associated lymph nodes, half-lives of 13 and 33 days were estimated for male and female rats, respectively; some of the rats became sensitized Oral toxicity: The oral LD₅₀ has been reported to range from 2030 to 3340 mg/kg in male and female rats, with stomach lesions appearing as the most consistent lesion upon necropsy; no adverse effects were observed in rats in a 90-day feed study with 1000-10000 ppm (50-500 mg/kg/d) Dermal toxicity: The dermal LD₅₀ was >2000 mg/kg in rabbits after a 24-hour occlusive application Inhalation toxicity: The LC₅₀ in rats was reported to exceed a concentration of 2330 mg/m³ (4-hour exposure), with lung lesions appearing as the most consistent lesion upon necropsy Numerous studies were conducted in rats, and in each of the following studies, the exposure was 6 h/d, 5 d/wk: in 2-week studies, no adverse effects were observed with 0.3 mg/m³; in rats exposed to 0.1 mg/m³, lung injury was absent after 2 days of exposure, minimal after 6 days of exposure, and marked after 10 days of exposure; a dose-dependent increase in antibody levels and lung foci was observed in rats exposed to up to 0.30 mg/m³ for 1-2 weeks, and the lung foci completely resolved within 12 days after the last exposure, but reappeared following exposure to a single challenge concentration; exposure to 0.5 mg/m³ produced hemorrhagic foci of the lung and increased antibody levels, and treatment with estrogen but not testosterone reduced the number of lung foci in both male and female rats; in a 13-week study, a dose-dependent increase in lung lesions (hemorrhagic foci, inflammatory cell infiltration, bronchoalveolar pneumonia) and antibody levels was observed in rats exposed to ≤0.054 mg/m³, and these effects were more pronounced in rats following 6.5 weeks of exposure than observed in animals following 13 weeks of exposure, and an NOEL was not identified In a 5-day inhalation study in mice with a 14-day recovery period, decreased time of inspiration and expiration and increased length of apneic periods were observed, and the LOEL was 0.01 mg/m³ Reproductive and developmental toxicity: No teratogenic effects or fetal deaths in rats or guinea pigs exposed to 500 µg/m³ via inhalation on days 6-15 of gestation; however, lung foci and TMA-specific antibody were observed in exposed dams and TMA-specific antibody was also noted in neonatal rats and in fetal but not neonatal guinea pigs, lung foci were only observed in the challenged offspring of rats whose mothers had not completely recovered from the original TMA exposure, but lung foci were not observed in adult rat offspring or in neonatal or adult guinea pig offspring; histopathological changes to reproductive tissues have not been observed in rats following subchronic exposures Genotoxicity: Not genotoxic with or without metabolic activation in 2 Ames tests (≤10000 µg/plate), in a CHO/HGPRT mutation assay (≤2000 µg/mL), or a chromosomal aberration assay in CHO cells (≤2080 µg/mL) Dermal irritation/sensitizer: Mild skin irritation potential was a dermal sensitizer in guinea pigs with induction with a 30% solution in DMSO and challenge with 5% in acetone, but 300 mg of powder was not a sensitizer in guinea pigs; sensitizer in rats with 25%-50% solutions in acetone/corn oil; sensitizer in mice with 10%-50% solutions in acetone/olive oil Ocular irritation: highly irritating to rabbit eyes when instilled undiluted Effects with occupational exposure: may be a respiratory irritant and sensitizer; elevated antibody levels, asthma, allergic rhinitis, and a late respiratory systemic syndrome are associated with occupational exposures in some workers Immunologic response: TMA-induced syndromes are related to high chemical reactivity, which couples to human serum albumin and other proteins to form trimellitate protein conjugates, and some of the TMA syndromes have been correlated to immunologic responses to trimellitate haptenic groups; in TNF-α^+/+ mice, in the late phase of TMA-induced contact hypersensitivity, the peak of ear swelling responses occurred at 24 hours with single challenge and at 8 hours after repeated challenge Recommended limits: REL (US NIOSH; exposure during a work week)—TWA 0.04 mg/m³ (0.005 ppm)	^2 –7
Adipic acid (124-04-9)	Panel Conclusion: safe in the present practices of use and concentration; reported to be used at a maximum of 0.000001% in leave-on formulations and 18% in rinse-off formulations Molecular weight: 146.14 Toxicokinetics: Under normal physiological conditions, dicarboxylic acids are rapidly β-oxidized, resulting in very low cellular concentrations and practically non-detectable concentrations in the plasma, and oxidation of odd- and even-numbered chains proceed to different end points with even chains completely, and odd-number chains not completely, oxidized; most of a single oral dose administered to rats was exhaled as carbon dioxide, and adipic acid and its metabolites were recovered in the urine, while very little adipic acid was found in the tissues; recovered unchanged in the urine of rabbits: with oral and IV dosing, approximately 53%-67% and 59%-71% was recovered, respectively; in human studies using 1 subject per dose and various doses/durations, 6.76%-61% was found in the urine after oral administration Oral toxicity: Oral LD₅₀ in rats ranged from 0.94 g/kg to greater than the highest dose tested (11 g/kg); in feeding studies in rats, the NOAEL was >435 mg/kg bw/d in a 4-week study; with ≤34000 mg/kg bw/d sodium adipate in a protein-deficient diet, the NOAEL was 3333 mg/kg bw in a 19-wk study; 10/14 rats fed a diet containing 3200 mg/kg bw/d died during weeks 0-4 of a 33-week study, body weights of the surviving animals in that group were similar to controls at study termination, and slight effects were seen in the liver; in a 2-year study, the NOAEL was 1%; slight decreases in weight gains were observed with 3 and 5% Inhalation toxicity: in mice exposed to 13 or 129 mg/m³ adipic acid via inhalation for 4 months (details of exposure not provided), decreased weight gain, altered oxidase activity, and upper respiratory tract, liver, kidney, and central nervous system effects were observed Reproductive and developmental toxicity: NOAELs for maternal and developmental toxicity were 288 mg/kg bw in CD-1 mice (highest dose given orally on days 6-15 of gestation) and 288 mg/kg bw in Wistar rats (highest dose given orally on days 6-15 of gestation); NOAELs for maternal toxicity and developmental toxicity were ≥250 mg/kg bw and 250 mg/kg bw, respectively, in Dutch-belted rabbits (maximum dose given by gavage on days 6-18 of gestation) Genotoxicity: not genotoxic in vitro in the Ames tests (concentrations up to 10000 mg/plate), yeast gene mutation assay (concentrations ≤200 mg/L), mouse lymphoma assay (concentrations of ≤2000 µg/plate), or cytogenetic assay (human embryonic lung fibroblast cells, ≤200 mg/L), or in vivo in a cytogenetics assay (chromosomes from rats dosed by gavage with 5000 mg/kg bw (single dose) or 2500 mg/kg bw (1× per day for 5 days) or in a dominant lethal assay (up to 5000 mg/kg bw); a significant increase in resorption per implant site was observed in hamsters with 205 mg/kg bw adipic acid, resulting in a decreased number of live fetuses (this decrease was not evaluated statistically, and no effects were reported at this or the other doses [≤44 mg/kg bw]) Carcinogenicity: not carcinogenic in a 2-year chronic study in rats fed up to 5% adipic acid Dermal irritation: Occlusive application of a 50% aq. solution to intact and abraded rabbit skin for 24 hours produced an erythema score of 2-3/4 for intact skin, with clearing by day 3, and mild to severe erythema and edema, for abraded skin, which cleared by day 7; when applied undiluted or as an 80% aq. paste to the backs or ears of rabbits for 24 hours, no irritation was observed on the backs and erythema was observed on the ear, with clearing by 72 hours; no irritation was observed with a 24-hour application (no details provided; semi-occlusive application of a 50% paste in propylene glycol produced slight to mild irritation in 3/6 rabbits; a semi-occlusive application of undiluted adipic acid was not corrosive; 50%, in propylene glycol, was not irritating to guinea pigs Dermal sensitization: not a sensitizer (1% for intradermal induction, up to 50% in propylene glycol for dermal challenge) and produced very mild or no irritation Ocular irritation: mild to severe ocular irritant in rabbit eyes; irritation was dose-dependent Peroxisome proliferation: did not induce peroxisome proliferation and did not affect relative liver to body weights in rats fed 2% dissolved in alcohol for 3 weeks	⁸
Cyclohexanedimethanol (105-08-8)	Molecular weight: 144.21 g/mol Toxicokinetics: When rats were dosed by gavage with 40 or 400 mg/kg/bw (¹⁴C; 70% trans-, 30% cis-isomers), there was rapid absorption from the GI tract and after 48 hours, 95% of dose was excreted in urine, 2.5% in feces, 0.03% respired as ¹⁴CO₂, and 0.4% remained in carcass, recovery of radioactivity averaged 98.9% of dose, and the half-life in plasma from rats dosed with 400 mg/kg was about 13 minutes; the test article and 4-hydroxymethylcyclohexanecarboxylic acid were detected in plasma, unchanged test article was not detected in urine and the major metabolites identified in urine were cyclohexanedicarboxylic acid (68%) and 4-hydroxymethylcyclohexanecarboxylic acid (31%), <2% of radioactivity in urine was not fully characterized, and the cis-trans ratio of metabolites excreted in urine was the same as that of original dose Oral toxicity: observations in rats given a single oral dose by gavage of 400-6400 mg/kg bw ranged from normal to very weak with prostration and vasodilatation; the oral LD₅₀ is reported to be >3200-6400 mg/kg in rats; in a 13-week study in which rats were given 4-12.5 mg/L (ie, 256-861 mg/kg bw/d for males and 440-1754 mg/kg bw/d for females) in drinking water, the LOAELs were 861 and 1754 mg/kg bw/d for males and females, respectively, based on decreased survival, abnormal urine and feces, reduced body weights and weight gains, decreased feed consumption and increased urinary protein levels, and the NOAELs were 479 and 754 mg/kg bw/d for males and females, respectively Reproductive and developmental toxicity: Male and female rats were given 4-12.5 mg/L (ie, 256-861 mg/kg bw/d for males and 440-1754 mg/kg bw/d for females) in drinking water prior to and during mating and until day 4 of lactation, for systemic toxicity, the LOAELs were 861 and 1360 mg/kg bw/d (based on bloody or discolored urine, reductions in body weights and weight gains and decreased feed consumption) and the NOAELs were 479 and 854 mg/kg bw/d for males and females, respectively, for developmental toxicity the LOAEL was 1360 mg/kg bw/d (based on decreased fetal weight and postnatal survival) and the NOAEL was 854 mg/kg bw/d, and for reproductive toxicity the LOAEL was greater than the highest dose tested and the NOAEL was 1360 mg/kg bw/d Genotoxicity: not genotoxic in vitro in an Ames test at ≤5000 µg/plate without and with activation, in a chromosomal aberration assay in human lymphocytes at ≤10 mM with or without metabolic activation, or in vivo at doses up to 2000 mg/kg in a mammalian bone marrow chromosomal aberration test in rats or a micronucleus test in mice Dermal irritation/sensitization: not irritating to rat skin when applied undiluted with a semi-occlusive patch; not a sensitizer in a guinea pig maximization test with 1% at intradermal induction at neat, applied neat for topical induction, and neat and at 50% for challenge Ocular irritation: moderately irritating to rabbit eyes	^9,10
Ethylene glycol (107-21-1)	Panel Conclusion (Special Report on reproductive and developmental toxicity): The metabolites of ethylene glycol monoalkyl ethers are reproductive and developmental toxins, but in general, these metabolites of concern are not expected to be formed in cosmetic formulations that contain polymers of ethylene glycol Molecular weight: 62.07 g/mol	¹¹
Isophthalic acid (121-91-5)	Molecular weight: 166.13 g/mol Toxicokinetics: readily eliminated from the body, largely unchanged, through the urine; in a 13-week feed study in rats, levels of test article in the blood increased in a dose-dependent manner, and 24-hour urinary excretion samples collected on days 7, 30, 60, 90 indicate that urinary excretion, presumably as the unchanged chemical, is the primary route of excretion; exposure of rats to 10 mg/m³ for 6 h/d resulted in immediate detection of the test article in the blood, serum levels were 5.3-9.3 µg/mL in females and 1.4-3.4 µg/mL for males, but no test article was detected in the blood 1 week following exposure Oral toxicity: Oral LD₅₀ _s have been reported in the range >5000 to 13000 mg/kg in rats; in a 13-week feeding study in rats with 800 mg/kg/d, a slight increase in the incidence of crystalluria and renal pathology (mild hydronephrosis, pelvic calcification) were observed, the NOAEL was 250 mg/kg/d, and the LOAEL was 800 mg/kg/d Dermal toxicity: No mortality was observed in rabbits following acute exposure to 23000 mg/kg; in a study with a 24-hour occlusive application, the oral LD₅₀ was >2000 mg/kg bw Inhalation toxicity: No mortality was observed in rats following acute inhalation exposures to 11400 mg/m³; in a 4-week study in which rats were exposed 6 hours/d 5 days/wk, no significant effects were observed with up to 10 mg/m³, and the NOAEL was 10 mg/m³ Reproductive and developmental toxicity: no maternal or developmental toxicity at inhalation exposures up to 10 mg/m³ in rats on days 6-15 of gestation Genotoxicity: Mixed results were reported in 3 Ames tests; negative in a chromosomal aberration assay in CHO cells at up to 5000 µg/mL with and without metabolic activation, in an HGPRT assay, and a mouse lymphoma mutation assay (with metabolic activation) Dermal irritation/sensitization: No dermal irritation with application of a single dermal dose to rabbits; a 4-hour semi-occlusive application and a 24-hour occlusive application of undiluted test material was not irritating to rabbit skin; mild dermal irritation with application of 2000 mg/kg; a 30% solution was not a skin sensitizer in guinea pigs (a reaction were observed in 1/10 of the guinea pigs) Ocular irritation: 0.1 g, undiluted, was non- to slightly irritating to rabbit eyes	^12 –14
Maleic anhydride (108-31-6)	Molecular weight: 98.06 g/mol Toxicokinetics: readily hydrolyzed to maleic acid under aqueous conditions Oral toxicity: according to the OECD summary, relatively low acute toxicity, with the oral LD₅₀ of about 1.0 g/kg in rats, but according to the EPA summary, acute oral studies in rats, mice, rabbits, and guinea pigs have demonstrated moderate to high acute toxicity by ingestion; oral feeding studies have resulted in kidney damage in rats at relatively high doses (> 100 mg/kg/d after 90 days of exposure), with the effects (which were more severe in males than in females) likely due to maleic acid; no kidney effects were observed in rats that were fed diets containing 32 and 100 mg/kg/d maleic anhydride for 2 years; a dietary study in dogs dosed with up to 60 mg/kg for 7days/wk for 90 days, showed no adverse effects related to maleic anhydride exposure Dermal toxicity: according to the OECD summary, relatively low acute toxicity, with a dermal LD₅₀ in the range of 1.6-2.6 g/kg in rabbit, but according to the EPA summary, moderate acute dermal toxicity Inhalation toxicity: bronchial asthma was observed with acute exposure in guinea pigs; possible respiratory sensitizer to rats; repeated exposure by inhalation to rats, hamsters, and monkeys resulted in effects that were limited to the respiratory tract and eye irritation; in a 4-week study in rats exposed 6 hours/d to up to 84 mg/m³ (21 ppm), evidence of nasal, trachea, and lung irritation was observed at all exposure levels, and the effects were concentration-related and included epithelial hyperplasia and the presence of inflammatory exudates in the nasal turbinates and trachea; and epithelia hyperplasia, squamous metaplasia, and intra-alveolar hemorrhage in the lung, with an LOAEL of 12 mg/m³ (3 ppm); in a 6-month inhalation study in which rats, hamsters, and monkeys were exposed to up to 9.8 mg/m³ (2.4 ppm), respiratory tract and eye irritation were observed, hyperplastic and metaplastic changes in the nasal passages were considered indicative of irritation and judged to be reversible, and the NOAEL for rats was 3.3 mg/m³ (0.8 ppm) and the NOAEL for hamsters and monkeys was 9.8 mg/m³ (2.4 ppm) Reproductive and developmental toxicity: In a 2-generation reproductive toxicity study in which rats were dosed via gavage with up to 150 mg/kg/d, the NOAEL for reproductive effects was 55 mg/kg/d (highest dose tested due to parental death at 150 mg/kg/day), but in the parental group, adverse effects (mortality, body weight changes, and respiratory irritation) were observed at 150 mg/kg/d, and there were histopathological effects in the kidneys and bladder of the parental animals (first generation only) in all treated dose groups, and the LOAEL for parental effects was 20 mg/kg/d; no developmental toxicity was observed when pregnant rats were dosed via gavage with up to 140 mg/kg/d, but the dams in all dose groups either lost weight or failed to gain weight between days 6 and 9 of gestation (effect was not statistically significant at any interval and was reversible), and the NOAEL (maternal) was determined to be 140 mg/kg/d Genotoxicity: negative in bacterial gene mutation tests; a single in vitro chromosomal aberration test with and without S-9 was positive (due to inadequate documentation on this study, it is unclear whether the results were due to the test material itself or a change in pH to an acidic environment, which could have resulted in a nonspecific effect); exposure of Sprague-Dawley rats of up to 100 mg/m³ (25 ppm) did not increase chromosomal aberrations in the bone marrow Carcinogenicity: not carcinogenic when given to rats in their diets for 2 years at doses up to 100 mg/kg/d; the EPA has not classified maleic anhydride for carcinogenicity Dermal irritation/sensitization: severely irritating to the skin of rabbits after application of 0.5 g to the skin for 4 hours (mean irritation score of 3.67-4.00 during the 7-day observation period); shown to be a skin sensitizer to guinea pigs Ocular irritation: severely irritating to the eyes of rabbits (eye irritation score was 106.7/110); in humans, exposure to 0.25-0.38 ppm (1-1.6 mg/m³) produced eye irritation, no irritation was reported at 0.22 ppm Respiratory effects (human): exposure to 0.25-0.38 ppm (1-1.6 mg/m³) produced respiratory tract irritation, no irritation was reported at 0.22 ppm Effects with occupational exposure: According to the OECD summary, there have been a few published human cases suggesting that maleic anhydride provokes asthma in a relatively small proportion of exposed workers; however, questions have been raised whether the asthma was actually related to maleic anhydride exposure; according to the EPA summary, chronic (long-term) exposure has been observed to cause chronic bronchitis, asthma-like attacks, and upper respiratory tract and eye irritation in workers, and in some people, allergies have developed so that lower concentrations can no longer be tolerated Recommended limits: The EPA RfD is 0.1 mg/kg bw/d based on renal lesions in rats (the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime; it is not a direct estimator of risk but rather a reference point to gauge the potential effects); OEHHA inhalation REL (chronic exposure level, exposure 24 hours/d for a lifetime) is 0.7 µg/m³ (2.5 ppb)	^15 –18
	Maleic Acid—Panel Conclusion: safe for use in cosmetic formulations as a pH adjustor in the practices of use described in the safety assessment (only use as a pH adjustor was evaluated); was reported to be used at 0.004% in “other” bath products; used in hair straighteners, other hair-coloring preparations, and shaving cream according to VCRP data, but no concentration data were reported for these uses According to the Discussion of the report, the Panel recognized that maleic acid itself may be a dermal and/or ocular irritant, but its use as a pH adjustor in cosmetic formulations dictates that most of the acid would be neutralized into various maleate salts; additionally, the concentration of maleic acid would be dependent on the alkaline content of the formulation; the Panel also stated that safety of maleic acid as a pH adjustor should be based on the amount of free maleic acid remaining after neutralizing the formulations	¹⁹
Neopentyl glycol(126-30-7)	Molecular weight: 104.15 Toxicokinetics: After rabbits were dosed with 1-1.5 g/kg bw (unlabeled) by gavage, 62% of the dose was found in the 24-hour urine as the conjugate of glucuronic acid, indicating rapid absorption, 1.9% was recovered as the metabolite 3-hydroxy-2,2-dimethylpropionic acid, and only 0.7% of the dose was present unchanged Oral toxicity: Oral LD₅₀ in rats reported as 3200 mg/kg to 6920 mg/kg; with repeated dosing with up to 1000 mg/kg/d by gavage, the NOAEL for males and females were 300 and 1000 mg/kg/d, respectively; in a 90-day gavage study, no adverse effects were observed at doses up to 1000 mg/kg Dermal toxicity: The dermal LD₅₀ was >4000 mg/kg bw in guinea pigs with a 24-hour occlusive application to a 20% solution in acetone/corn oil vehicle Inhalation toxicity: There was no mortality in rats exposed to a saturated vapor for 8 hours (the calculated nominal concentration was 140 mg/m³); rats exposed for 6 hours to 39400 ppm (168 mg/L) showed symptoms of irritation of the respiratory tract, 1/3 died within 24 hours; 3 rats were exposed to 4000 ppm, 6 hours/d for 10 days, and irritation of the respiratory tract and dilatation of the skin blood vessels were detected, but no evidence of toxic effects on internal organs was observed at necropsy Reproductive and developmental toxicity: The NOAEL for maternal and prenatal developmental toxicity was 1000 mg/kg with dosing with ≤1000 mg/kg on days 6-19 of gestation; in a reproductive toxicity study in which rats were dosed with up to 1000 mg/kg/d by gavage before and during mating and through day 3 of lactation, the NOAEL was 1000 mg/kg for the parent and F₁ generation Genotoxicity: not genotoxic in an Ames test (up to 5000 µg/plate) or to Chinese hamster ovary cells (up to 1 mg/mL) Dermal irritation/sensitization: An 80% aq. solution was not an irritant to rabbit skin with a 20-hour occlusive exposure; slightly irritating to rabbit skin with a 4-hour exposure to undiluted test material; not a sensitizer in a mouse LLNA (60% in propylene glycol) Ocular irritation: Instillation of crystalline test substance resulted in serious damage to rabbit eyes in one study, and instillation of neat test article in rabbit eyes resulted in irreversible damage in one study and slight to moderate irritation in another study	^20,21
Phthalic anhydride(85-44-9)	Molecular weight: 148.12 g/mol Stability: rapidly hydrolyzed to phthalic acid upon contact with water Toxicokinetics: Unconjugated compound was found in the urine of humans exposed by inhalation, demonstrating systemic absorption and elimination via the urine and the existence as a hydrolysis product in vivo Oral toxicity: oral LD₅₀ of 1530 mg/kg bw in rats; low repeated dose toxicity in rats; in a 7-week feed study in which mice were given up to 7140 and rats up to 3330 mg/kg bw/d, there were no effects in mice, but there was a significant reduction in body weight gains in rats of the high dose group, and centrilobular cytoplasmic vacuolation was seen in the livers in most of the male rats fed 1660 mg/kg bw/d; in male and female mice fed 4670 and 3430 mg/kg bw/d, respectively, for 105 weeks, significantly increased incidences of lung and kidney lymphocytosis in the low- and high-dose males and females, chronic bile duct inflammation in the high-dose males and females, and dose-related adrenal atrophy and mineralization of the thalamus in the low-and high-dose males were observed, and the time weighted LOAELs were approximately 1717 and 2340 mg/kg bw/d in female and male mice, respectively, and no NOAEL was obtained Dermal toxicity: The dermal LD₅₀ was >10000 mg/kg bw in rabbits Inhalation toxicity: The LC₅₀ was >2.14 mg/L following a 4-hour nose-only exposure; respiratory sensitization potential in guinea pigs, and animals exposed to and challenged with 5.0 mg/m³ phthalic anhydride dust had significant numbers of hemorrhagic lung foci Reproductive and developmental toxicity: No evidence of toxicity to reproductive organs was observed in comprehensive carcinogenicity studies in rats and mice, as no treatment-related changes were observed for any reproductive organ investigated during macroscopic and microscopic examination; decreased sperm motility time was reported in a study in which male rats were exposed via inhalation at 0.2 mg/m³, and no effects were observed at 0.02 mg/m³ (it was noted that confidence in this study was limited because of the small sample size of 6/group, poor documentation, and lack of data on the biological and statistical relevance of the observed effects) Genotoxicity: not mutagenic in the Ames test (up to 5000 µg/plate); induced chromosomal aberrations in mammalian cells only at the high concentration of 10 mM without metabolic activation; not genotoxic in a sister chromatid exchange assay (10-300 µg/mL with and without metabolic activation) Carcinogenicity: No evidence of carcinogenicity in rats fed 1000 mg/kg bw/d or in male and female mice fed 4670 and 3430 mg/kg bw/d, respectively, 105 weeks Dermal irritation/sensitization (animal): Mild irritation was observed when 550 mg of flakes were applied to rabbits for 4 hours, the average dermal irritation index after semi-occlusive exposure was 1.21/8, and observed effects were reversible; semi-occlusive application of 500 mg (moistened with water) on the ear for 24 hours was not an irritant; sensitizer in the GPMT and at a concentration of 10% in the LLNA in mice Dermal irritation (humans): Contact with either the solid or a vapor has been reported to cause skin irritation after occupational exposure; erythema, blistering, ulceration, and necrosis have been reported following skin contact Ocular irritation: irritating to rabbit eyes (undiluted) Mucous membrane irritation: a primary irritant in humans when in the form of vapor, fumes, or dust Respiratory effects (humans): a primary irritant to the upper respiratory tract when in the form of vapor, fumes, or dust Effects with occupational exposure: conjunctivitis, rhinitis, rhinoconjunctivitis, bronchitis, and irritation of the skin and mucous membranes of the respiratory tract have been observed in exposed workers; initial exposure produces coughing, sneezing, burning sensations in the nose and throat, and increased mucous secretion; occasional bloody sputum, emphysema, lower blood pressure, and minor signs of central nervous system excitation have been observed in chronically exposed workers Recommended limits: The EPA has calculated a provisional RfC of 0.12 mg/m³ (the RfC is an estimate [with uncertainty spanning perhaps an order of magnitude] of a continuous inhalation exposure to the human population [including sensitive subgroups] that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime. It is not a direct estimator of risk but rather a reference point to gauge the potential effects); the EPA has established an oral RfD of 2.0 mg/kg bw/d	^22 –25
Propylene glycol(57-55-6)	Panel Conclusion: safe in the present practices of use and concentration when formulated to be nonirritating; reported to be used at up to 73% in leave-on formulations Molecular weight: 76.09 g/mol Toxicokinetics: the major route of metabolism is to lactaldehyde and then lactate via hepatic alcohol and aldehyde dehydrogenases Dermal absorption: penetration from a ternary cosolvent solution through hairless mouse skin was 57% over a 24-hour period, and it appears that it does not reach the dermis; it can act as a penetration enhancer Oral toxicity: The oral LD₅₀ was 21 g/kg in rats; no mortality in mice given 10% in drinking water for 14 days; lesions were not observed in rats that were fed diets containing 50000 ppm (2.5 g/kg/d) for 15 weeks or up to 50000 ppm in the diet for 2 years; similar results were reported in a study in which dogs were fed 2 or 5 g/kg in the diet for 103 weeks; in dogs given 5% in drinking water for 5-9 months, no hepatic or renal impairment was noted Inhalation toxicity: Some effects in rats due to exposure of 2.2 mg/L air for 6 hours/d, 5 days/wk, for 13 weeks, but these effects were inconsistent and without dose-response trends Reproductive and developmental toxicity: not teratogenic in female CD-1 mice when administered orally at a concentration of 10000 ppm (vehicle not specified) on days 8-12 of gestation; no reproductive effects in a continuous breeding reproduction study in albino mice with up to 5% administered in feed or water; no adverse effects on reproduction or development when given orally at doses up to 1600 mg/kg in mice and rats, 1230 mg/kg in rabbits, or 1550 mg/kg in hamsters Genotoxicity: not mutagenic in an Ames test at up to 10000 µg/plate with or without metabolic activation; caused a dose-dependent increase in the frequency of SCEs in a Chinese hamster cell line and was classified as a weak inducer of SCEs, but in another SCE study, it was not genotoxic in human cultured fibroblasts or a cultured Chinese hamster cell line with or without metabolic activation; chromosomal aberrations were induced in Chinese hamster fibroblasts in another assay; was not genotoxic in additional tests for chromosomal aberrations, mitotic recombination, or basepair substitution, or DNA damage or a micronucleus test Carcinogenicity: not carcinogenic in a 2-year feeding study at up to 50000 ppm in rats; did not induce skin tumors and was not carcinogenic in a lifetime dermal study at concentrations up to 100% in mice Dermal irritation/sensitization (animal): 10% was not a dermal irritant in a 24-hour test in nude mice, but hypertrophy, dermal inflammation, and proliferation were observed at a concentration of 50%; not an irritant to intact or abraded skin of rabbits in a Draize test, to guinea pig or rabbit skin when applied for 48 hours using open and occlusive patches or to swine skin in 48-hour and 21-day open and occlusive patch tests; not a sensitizer in a mouse external ear swelling sensitization test undiluted, in a GPMT, OET, or chamber (Finn chamber) test (at 70%); was a potentially weak sensitizer in one maximization test, but the results of 6 other guinea pig sensitization indicated it was not an allergen Dermal irritation/sensitization (human): induced skin irritation and sensitization reactions in normal subjects and patients in studies with test concentrations ranged from 2%-100%, and reactions were observed at concentrations as low as 10% in predictive tests and as low as 2% in provocative tests; however, the dermal irritation potentials of deodorant formulations containing 68.06% or 69.15% were evaluated in an SIOPT and compared to a reference in-use control formulation, and the formulations containing propylene glycol were no more irritating or even less irritating than the reference control; use studies of deodorant formulations containing 35%-73% did not report any potential for eliciting irritation or sensitization; deodorant formulations containing 69.15% or 86% did not induce sensitization reactions; questionable results were obtained in an RIPT of a deodorant containing 73%; retrospective analysis of pools of patient patch test data indicated that ≤6.0% of patients tested had positive reactions to a 30% aq. solution; increased the allergic responses in 43 patients patch tested with 50 µg 1% nickel sulfate solution Photoallergenicity: did not produce a photoallergic response in a provocative photopatch test (concentration not specified) Ocular irritation: did not induce corneal damage in rabbit eyes in one study; was a slight ocular irritant in another	^26,27
Sebacic acid(111-20-6)	Panel Conclusion: safe in the present practices of use and concentration; reported to be used at a maximum of 0.03% in leave-on formulations and 1% in rinse-off formulations Molecular weight: 202.25 Toxicokinetics: oxidized to water and carbon dioxide, passing through acetyl-CoA and succinyl-CoA formation; under normal physiological conditions, dicarboxylic acids are rapidly β-oxidized, resulting in very low cellular concentrations and practically non-detectable concentrations in the plasma, and oxidation of even-numbered chains is complete; recovered unchanged in the urine of rats: with IV dosing, approximately 35% sebacate was recovered Oral toxicity: Disodium sebacate was not toxic to rats or rabbits fed up to 1000 mg/kg bw for 6 months Reproductive and developmental toxicity: In dietary studies, disodium sebacate was not a developmental toxicant in rats (500 mg/kg bw/d; days of dosing not stated) or rabbits (1000 mg/kg bw)	⁸
trimethylpentanediol(144-19-4)	molecular weight: 146.23 oral toxicity: oral LD₅₀ was 1800 mg/kg bw and >2000 mg/kg bw in male mice and female rats, respectively; in rats fed ≤2% for 57 days, the NOAEL for males and females was 0.5% (376 mg/kg bw/day) because of changes in organ wts at higher doses dermal toxicity: in a study in guinea pigs (1 animal/dose), the dermal LD₅₀ was >1 g/kg bw inhalation toxicity: the LC₅₀ was >4.5 mg/l in rats with a 6-h exposure period (the respirable concentration of the test substance was 1.43 mg/l and the calculated exposure to the respirable portion of the test substance was 2.8 g/kg bw) reproductive and developmental toxicity: in a 3-generation dietary study in rats at concentrations up to 1% in feed, the NOAEL was 1% for both parental and for reproductive and developmental toxicity genotoxicity: not genotoxic, with or without metabolic activation, in an Ames test at concentrations up to 5000 µg/plate, in a mammalian cell assay at concentrations up to 1462.3 µg/mL in mouse lymphoma cells, or in a chromosomal aberration assay at concentrations up to 1500 µg/ml in CHO cells irritation/sensitization: an occlusive 4-h exposure was not irritating to intact or abraded rabbit skin; 0.1 M was not a sensitizer in guinea pigs ocular irritation: undiluted test material was a slight irritant to rabbit eyes	^28,29
Trimethylolpropane(77-99-6)	Molecular weight: 134.17 g/mol Oral toxicity: In a gavage study, the LD₅₀ was ∼14700 mg/kg in male rats; in a 90 day feeding study with up to 1.0% (667 mg/kg bw/d) in rats, the NOAEL was 0.1% (67 mg/kg bw/d) based on significant changes of clinical chemistry or hematological data (at ≥0.3%) and histopathological changes, mainly in liver and spleen (at 1%) Dermal toxicity: The dermal LD₅₀ was >10000 mg/kg bw in rabbits with a 24-hour occlusive application Inhalation toxicity: The LC₅₀ was >850 mg/m³ (vehicle, ethanol/lutrol 1:1) in rats with a 4-hours exposure period Reproductive and developmental toxicity: in rats dosed by gavage with up to 1000 mg/kg/d on days 6-20 of gestation, the NOAEL was 100 mg/kg bw/d for developmental toxicity due to decreases in fetal weight and 100 mg/kg bw/d for maternal toxicity due to decreased body weight and weight gains; in a study in which male and female rats were dosed by gavage with up to 800 mg/kg bw/d before, during, and after mating, the NOAEL was 800 mg/kg bw/d for reproductive and developmental toxicity and 200 mg/kg bw/d for general toxicity Genotoxicity: not genotoxic, with or without metabolic activation, in an Ames test at concentrations up to 5000 µg/plate, in a mammalian cell assay at concentrations up to 1400 µg/mL in Chinese hamster lung fibroblasts, or in a chromosomal aberration assay at concentrations up to 1340 µg/mL in Chinese hamster lung cells Dermal irritation/sensitization: Application to the inner ear of rabbits did not produce irritation; no sensitization in a mouse LLNA at concentrations up to 50% Ocular irritation: not irritating to rabbit eyes when instilled undiluted or melted	^30,31

Abbreviations: DMSO – dimethyl sulfoxide; EPA – Environmental Protection Agency; CHO – Chinese hamster ovary; GPMT – guinea pig maximization test; HGPRT - hypoxanthine-guanine phosphoribosyltransferase; LLNA – local lymph node assay; LOAEL – lowest observable adverse effect level; NIOSH – National Institute for Occupational Safety and Health; NOAEL – no-observable adverse effect level; OECD – Organisation for Economic Co-operation and Development; OEHHA - Office of Environmental Health Hazard Assessment (California); OET – open epicutaneous test; NIOSH REL – recommended exposure limit; OEHHA REL – reference exposure level; RfC – reference concentration; RfD – reference dose; RIPT – repeated insult patch test; SCE – sister chromatid exchange; SIOPT – single insult occlusive patch test; TMA – trimellitic anhydride; TWA – time-weighted average; VCRP – Voluntary Cosmetic Registration Program.

The safety of several of the non-anhydride monomers has previously been reviewed by the Expert Panel for Cosmetic Ingredient Safety (Panel). In 2012, the Panel concluded that adipic acid and sebacic acid are safe in the present practices of use and concentration⁸ and that propylene glycol is safe as used in cosmetic formulations at the present practices of use and concentration when formulated to be nonirritating.²⁶ In 1999, the Panel published a special report on the reproductive and developmental toxicity of ethylene glycol and its ethers, concluding that the metabolites of ethylene glycol monoalkyl ethers are reproductive and developmental toxins, but in general, these metabolites of concern are not expected to be present in cosmetic formulations that contain polymers of ethylene glycol.¹¹

Chemistry

Definition and Structure

The ingredients in this report are copolymers that share in common trimellitic anhydride as a monomer. They are interconnected via ester bonds to form highly branched polymeric (polyester) networks. For example, Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer is the result of the polymerization of propylene glycol, sebacic acid, and trimellitic anhydride (Figure 1). In this case, there are 2 acid monomers (sebacic acid and trimellitic anhydride) and one alcohol monomer (propylene glycol). This means that to form a polyester copolymer, every other repeat unit must be propylene glycol. Whether the repeat unit on either end of propylene glycol is the residue of sebacic acid or the residue of trimellitic acid is dependent on the polymerization conditions. Since trimellitic anhydride serves as a rigid, nonlinear, trifunctional (trivalent) monomer, these polymers are branched, if not highly branched, in a manner similar to dendrimers. The definitions and structures of the ingredients included in this review are provided in Table 1.

Figure 1.

Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer—the connectivity between alcohols (propylene glycol, in this case) and which acids (sebacic acid and trimellitic anhydride, in this case) can vary; this is just one theoretical example of a fragment within a polymeric network.

Chemical Properties

Limited chemical properties data on the trimellitic anhydride copolymers as cosmetic ingredients were found in the published literature, and unpublished data were not submitted. The information that was identified is presented in Table 3.^32
–34

Table 3.

Chemical Properties.

Property	Description	Reference
Adipic Acid/CHDM/MA/Neopentyl Glycol/ Trimellitic Anhydride Copolymer
Form	Liquid or solid	³²
Solubility	Insoluble in water	³²
Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer
Form	clear liquid	³³
Avg molecular weight	8999 Da	³⁶
Solid content	70-80% (in butyl acetate)	³³
Solubility	Low solubility in cold water; soluble in all “common solvents”	³³
Acid number	10-20 mg KOH/g	³³
Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer
Number avg molecular weight (Mn)	>1000 Da	⁴¹
Water solubility	Insoluble	⁴¹
Dissociation constant	Expected to be ionized under environmental conditions (pH 4-9)	⁴¹
70% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer/30% butyl acetate
Form (at 20 °C)	Light yellow liquid	⁴¹
Density	1091 kg/m³	⁴¹

Abbreviation: CHDM, cyclohexanedimethanol.

Method of Manufacture

Common, general polyester synthesis techniques can be described for the manufacture of trimellitic anhydride copolymers.³⁵ The manufacture of each of these trimellitic anhydride copolymers begins with trimellitic anhydride (an activated form of trimellitic acid). For example, synthesis would start by dissolving trimellitic anhydride in a dry solvent, such as dimethylformamide, under an inert gas, such as nitrogen. Next, the appropriate polyol monomer (eg, propylene glycol, neopentyl glycol, cyclohexanedimethanol, trimethylolpropane, ethylene glycol, or trimethylpentanediol) would be added to the solution and distilled under reduced pressure. In a second step, the resultant terminal alcohol groups may be further esterified with appropriate mono- or multifunctional carboxylic acids (eg, sebacic acid, adipic acid, maleic anhydride, isostearic acid, phthalic anhydride, sebacic acid, or isophthalic acid), and, likely, a catalyst. This 2-step methodology would result in dendrimer-like copolymers, with trimellitic acid as the central core in each. Alternatively, trimellitic anhydride, a polyol, and an additional carboxylic acid of choice could be reacted together in 1 step, under similar conditions, to form more randomly structured copolymers. Due to the trivalent nature of trimellitic acid, however, the resultant polymers from either of these 2 methodologies would be nonlinear.

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

In the synthesis of Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer, the trifunctional glycol(s) and the di- and tribasic acids are charged into a clean and dry reaction vessel.³⁶ Heat is applied to drive the polyester reaction, and water is generated as a by-product of the reaction; the rate of reaction is controlled by the heat applied. The reactant mixture is heated gradually to 200 °C, and the in-process wet properties are measured. The reaction mixture is cooled and dissolved in the solvent; the final product is cooled further and packaged.

Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer

Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer results from condensation of phthalic anhydride, trimellitic anhydride, ethylene glycol, and neopentyl glycol monomers.³⁷

Impurities/Composition

Limited impurities data on the trimellitic anhydride copolymers as cosmetic ingredients were found in the published literature, and unpublished data were not submitted. The reactions used to manufacture the copolymers can be designed to result in little to no residual monomer, but information on the exact manufacturing process was not available for most of the polymers. Without having a precise manufacturing method, the remaining residual amount of monomer present in the copolymer is unknown. Therefore, it is possible that residual amounts of the following monomers (used in the production of these copolymers) could be present in these ingredients: adipic acid, cyclohexanedimethanol, ethylene glycol, isophthalic acid, maleic anhydride (or maleic acid), neopentyl glycol, phthalic anhydride (or phthalic acid), trimellitic anhydride (or trimellitic acid), trimethylpentanediol, trimethylolpropane, and isostearic acid.

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is synthesized from adipic acid, neopentyl glycol, and trimellitic anhydride.³⁶ A quantitative [¹ H] nuclear magnetic resonance study reported that approximately 1.5% residual glycol is present. Residual trimellitic anhydride and adipic acid concentrations were below the limit of detection (ie, 50 ppm or 0.005%).

One supplier has reported that Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is sold in butyl acetate (70%-80% solids) and does not contain formaldehyde, toluene, or xylene.³³

Use

Cosmetic

The safety of the cosmetic ingredients included in this assessment is evaluated based on data received from the US Food and Drug Administration (FDA) and the cosmetics industry on the expected use of these ingredients in cosmetics. Use frequencies of individual ingredients in cosmetics are collected from manufacturers and reported by cosmetic product category in the FDA Voluntary Cosmetic Registration Program (VCRP) database. Use concentration data are submitted by Industry in response to surveys, conducted by the Personal Care Products Council (Council), of maximum reported use concentrations by product category.

According to 2016 VCRP data, Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is reported to be used in 471 cosmetic formulations, 470 of which are nail formulations, and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer is reported to be used in 85 cosmetic formulations, 83 of which are nail formulations; the remaining uses reported to the VCRP indicated dermal exposure³⁸ (Table 4). However, the results of the concentration of use survey conducted by the Council in 2015 only report use in nail formulations. According to the Council survey, the highest maximum concentration of use for both of these ingredients is in nail polish and enamel; Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is reported to be used at up to 32.8% and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer at up to 12%.³⁹

Table 4.

Frequency and Concentration of Use According to Duration and Type of Exposure.

	# of Uses ³⁸	Max Conc of Use (%) ³⁹	# of Uses ³⁸	Max Conc of Use (%) ³⁹
	Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer		Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer
Totals*	471	5.4-32.8	85	1.8-12
Duration of Use
Leave-On	470	5.4-32.8	85	1.8-12
Rinse-Off	1	NR	NR	NR
Diluted for (Bath) Use	NR	NR	NR	NR
Exposure Type
Eye Area	NR	NR	NR	NR
Incidental Ingestion	NR	NR	NR	NR
Incidental Inhalation-Spray	NR	NR	NR	NR
Incidental Inhalation-Powder	NR	NR	NR	NR
Dermal Contact	1	NR	2	NR
Deodorant (underarm)	NR	NR	NR	NR
Hair—Non-Coloring	NR	NR	NR	NR
Hair—Coloring	NR	NR	NR	NR
Nail	470	5.4-32.8	83	1.8-12
Mucous Membrane	NR	NR	NR	NR
Baby Products	NR	NR	NR	NR

* Because each ingredient may be used in cosmetics with multiple exposure types, the sum of all exposure types may or may not equal the sum of total uses.

NR – not reported.

The remaining trimellitic anhydride copolymers (ie, Adipic Acid/CHDM/MA/Neopentyl Glycol/Trimellitic Anhydride Copolymer; Isostearoyl Trimellitic Anhydride/Trimethylolpropane Copolymer; Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer; or Trimethylpentanediol/Isophthalic Acid/Trimellitic Anhydride Copolymer) are not reported to be in use.

None of the trimellitic anhydride copolymers named in the report are restricted from use in any way under the rules governing cosmetic products in the European Union.⁴⁰

In Australia, according to a National Industrial Chemicals Notification and Assessment Scheme (NICNAS), Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer was determined to be a polymer of low concern (PLC), having met criteria for molecular weight requirements, functional group equivalent weight requirements, low charge density, approved elements only, stability under normal conditions, it is not water absorbing, and it is not a hazardous substance or dangerous good.⁴¹ Therefore, it is not considered to pose an unreasonable risk to the health of workers and the public when used as a component of cosmetic nail products.

Non-Cosmetic

Adipic Acid/CHDM/MA/Neopentyl Glycol/Trimellitic Anhydride Copolymer is used in preparation of glass fiber reinforced plastic.³² Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer is used in the manufacture of dyes, pharmaceuticals, insecticides, and as a hardener for resins.⁴²

Toxicokinetics

Absorption, Distribution, Metabolism, and Excretion

Toxicokinetics studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Toxicological studies

Toxicological studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Developmental and Reproductive Toxicity Studies

Developmental and reproductive toxicity studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Genotoxicity Studies

Genotoxicity studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Carcinogenicity Studies

Carcinogenicity studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Dermal Irritation and Sensitization Studies

Human repeated insult patch tests (HRIPTs) were conducted with nail polish formulations containing up to 15% Adipic Acid/ Neopentyl Glycol/Trimellitic Anhydride Copolymer^43

–48 and up to 7.5% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer^49,50 (Table 5). None of the formulations were sensitizers or irritants.

Table 5.

Human Repeated Insult Patch Tests of Nail Polish Formulations.

Concentration in formulation	Concentration/Dose	Test population	Procedure	Results	Reference
ADIPIC ACID/NEOPENTYL GLYCOL/TRIMELLITIC ANHYDRIDE COPOLYMER
3.85%	Undiluted	52 subjects	¾” × ¾” patches applied to the backNo other details provided	No irritation or sensitization	⁴³
7.98%	Undiluted; 0.2 mLVolatilized for 30-60 minutes prior to patch application	113 subjects	24-hour semi-occlusive induction patches were applied to the back 3 times per week for 3 weeks; 24-hour challenge patches were applied after a 2-week nontreatment period to previously untreated sites	Not an irritant or sensitizerSporadic generally transient, barely perceptible (0.5) response were observed in some subjects	⁴⁴
10%	Undiluted; test material was volatilized	213 subjects	24-hour semi-occlusive induction patches were applied to the back 3 times week for 3 weeks; 24-hour challenge patches were applied after a 2-week nontreatment period to previously untreated site	Not an irritant or sensitizer	⁴⁵
10.5%	Undiluted	107 subjects	1” × 1” patches applied to the upper backNo other details provided	No irritation or sensitization	⁴⁶
13.9%	Undiluted; 0.2 mLDried to touch before application	213 subjects	24-hour semi-occlusive induction patches (2 cm × 2 cm) were applied to the back or upper arm 3 times a week for 3 weeks; 24-hour challenge patches were applied after a 10-15 days of nontreatment period to previously untreated sites	No irritation or sensitization	⁴⁷
15%	Undiluted; test material was allowed to air dry on patch	108 subjects	24-hour semi-occlusive induction patches were applied to the upper back 3 times a week for 3 weeks; 24-hour challenge patches were applied after a 2-week nontreatment period to previously untreated sites	Not an irritant or sensitizer	⁴⁸
PHTHALIC ANHYDRIDE/TRIMELLITIC ANHYDRIDE/GLYCOLS COPOLYMER
7%	Undiluted; 0.2 mLVolatilized for 30-60 minutes prior to patch application	53 subjects	24-hour semi-occlusive induction patches were applied to the back 3 times a week for 3 weeks; 24-hours challenge patches were applied after a 2-week nontreatment period to previously untreated sites	Not an irritant or sensitizer	⁴⁹
7.5%	Undiluted; 0.2 mLVolatilized for 15 minutes prior to patch application	103 subjects	9, 24-hour semi-occlusive induction patches; 1 challenge patch was applied after a 10-15 days of non-treatment period	One subject had minimal or definite erythema, often with itching, at all but 2 of the induction readings and at challenge; no other reactions were noted.	⁵⁰

According to an NICNAS report, there is uncertainty regarding the potential sensitization of Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer, but the ingredient cannot be classified for sensitization.⁴¹

Ocular Irritation Studies

Ocular irritation studies on the trimellitic anhydride copolymers were not found in the published literature, and unpublished data were not submitted.

Clinical Reports

Case Reports

Several case reports describing allergic reactions to Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in nail polish were available.^37,42,51 Details from these case reports are summarized in Table 6.

Table 6.

Case Reports With Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in Nail Polish

Case history	Patch testing	Reference
A female subject had a 2-month history of an intermittent itchy rash on the neck and around the eyes, associated with episodes of swelling of the eyelids; mild erythema and scaling were present the upper eyelids and neck	- Patch testing was performed with the British standard series, a modified cosmetic series, a modified plant series, with her cosmetics, and her nail varnish (which was applied to a Finn Chamber and allowed to dry before application); a positive reaction (+) was observed with the nail varnish at days 2 and 4; there was no reaction to tosylamide/formaldehyde resin- Patch testing with the nail varnish components resulted in a positive reaction (++) to 1% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in petrolatum was observed at days 2 and 4; a + reaction was also observed to the 5 coloring bases that contained this ingredient- Testing in 12 control subjects had negative results	⁵¹
A female subject had a 12-month history of periorbital and fingertip eczema	- The subject was patch-tested with the BCDSB, a cosmetic and medicament series, and her own cosmetics; a positive reaction (+) was observed with her nail varnish (which was applied to a Finn Chamber and allowed to dry before application) on day 4- Patch testing with the nail varnish components resulted in a positive reaction (++) to 1% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in petrolatum at day 4	⁴²
A female subject had a 6-month history of perioral eczema and dry, fissured lips	- The subject was patch-tested with the BCDSB, a cosmetic and dental series, and her own cosmetics; a positive reaction (+) was observed with her nail varnish (which was applied to a Finn Chamber and allowed to dry before application) on day 4	⁴²
A female subject had a 6-month history of intermittent eczema of her face and fingers	- The subject was patch-tested with the BCDSB, a cosmetic series, and her own cosmetics; positive reactions (+) were observed with her nail varnish (which was applied to a Finn Chamber and allowed to dry before application) on days 2 and 4- Patch testing with the nail varnish components resulted in a positive reaction (+) to 1% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in butyl acetate on day 4	⁴²
A female subject had periungual dermatitis affecting all her fingers; she had been wearing nail varnish and acrylic nails for several years	- The subject was patch-tested with the BCDSB and acrylic series; she had positive reactions to several compounds, including 1% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in butyl acetate on days 2 and 4	⁴²
Three case reports were described:An atopic female subject presented with generalized eczema and major lichenification of lips and eyelids progressively worsening during the past 4 years; recent patch testing with the standard ICDRG series (2) was negativeA female subject had recurrent eyelid and neck dermatitis, with severe nail dystrophy; patch testing with a standard series, toluene sulfonamide formaldehyde resin, and her own nail polishes were negative; the lesions persisted for several months, and she was referred againA female subject had a history of occupational contact dermatitis and asthma due to glutaraldehyde presented with head and neck eczema lasting for 3 months	- Patch testing with all nail polish formulations resulted in positive reactions to a few of the polishes; patch testing with toluene sulfonamide formaldehyde resin was negative- Patch testing with the nail varnish components Identified Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer (tested at 1% and 5% in petrolatum) as the allergen in all 3 subjects- Subsequent patch testing with the raw monomers, ie, phthalic anhydride, trimellitic anhydride, and glycols was performed in 2 subjects; the results were negative	³⁷

Abbreviations: BCDSB - British Contact Dermatitis Society Standard Battery; ICDRG - International Contact Dermatitis Research Group.

Summary

This report addresses the safety of 6 trimellitic anhydride copolymers as used in cosmetics. According to the Dictionary, these ingredients are reported to function as film formers. The trimellitic anhydride copolymers are related as they all share a common monomer, that is, trimellitic anhydride; each copolymer is also composed of 1 to 4 different monomers. The monomers that comprise these copolymers are interconnected via ester bonds to form highly branched polymeric (polyester) networks. Limited information on the amount of residual monomer in these copolymers was submitted.

Voluntary Cosmetic Registration Program data obtained from the FDA and data received in response to a survey of the maximum reported use concentration by product category conducted by the Council indicate that 2 of the 6 ingredients included in this safety assessment are used in cosmetic formulations. According to the VCRP, Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is reported to be used in 471 cosmetic formulations, 470 of which are nail formulations, and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer is reported to be used in 85 cosmetic formulations, 83 of which are nail formulations. Only uses in nail products were reported in response to the Council survey, and the highest maximum concentration of use for both of these ingredients is in nail polish and enamel; Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer is reported to be used at up to 32.8%, and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer is reported to be used at up to 12%.

Human repeated insult patch tests were conducted with nail polish formulations containing up to 15% Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer and up to 7.5% Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer. None of the formulations were sensitizers or irritants. Several case reports have, however, described allergic reactions to Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in nail polish. Toxicokinetics, toxicological, genotoxicity, and ocular irritation data were not found in the published literature, and unpublished data were not submitted.

Discussion

The Panel considered this safety assessment of 6 trimellitic anhydride copolymers as used in cosmetics; these ingredients are related in that they all include trimellitic anhydride (aka 1,2,4-benzenetricarboxylic acid anhydride) as a monomer. Because very limited data were available for use in determining the safety of these ingredients, the Panel issued an Insufficient Data Announcement (IDA) at its September 2015 meeting, notifying the public that the data on the trimellitic anhydride copolymers were insufficient to determine whether the ingredients, under each relevant condition of use as indicated in this assessment, are either safe or unsafe. Both, the FDA VCRP data and the Council concentration of use survey, report that these ingredients are used (or are likely to be used) in nail products but only the VCRP data indicate that any of these ingredients are used in products that are intended to come into contact with the skin.

Dermal irritation and sensitization data on nail polish formulations were submitted to the Cosmetic Ingredient Review (CIR) in response to the IDA; the test data were not at the maximum concentrations of use indicated in this assessment. The Panel remained concerned that the copolymers were essentially chemically undefined. In response to this concern, method of manufacture and composition data were received for Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer; these data were sufficient for the Panel to conclude on the safety of Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer in nail, but not in non-nail, formulations.

The Panel considered the NICNAS determination that Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer is a PLC and is not considered to pose an unreasonable risk to public health of workers and the public when used as a component of cosmetic nail products. The PLC criteria that were met include molecular weight requirements, functional group equivalent weight requirements, low charge density, approved elements only, stability under normal conditions, not water absorbing, and not a hazardous substance or dangerous good. The fact that Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer met these criteria mitigated concern regarding the safe use of this ingredient in nail formulations; it did not address information needs for use in non-nail cosmetic formulations.

In order to determine safety of the use of Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer in cosmetics other than nail products, irritation and sensitization data at maximum leave-on concentrations of use are needed.

The data remain insufficient to determine the cosmetic safety of the remaining 4 ingredients included in this safety assessment; these ingredients are not reported to be in use. The following are needed to evaluate the safety of these ingredients for use in nail products:

Method of manufacture; and

Composition data.

In addition, the following data are needed to evaluate the safety of these 4 ingredients in non-nail cosmetic formulations:

Molecular weight;

Impurities, specifically, the amount of residual monomer in each copolymer;

Metabolism, specifically, whether these ingredients are metabolized in the skin;

Dermal absorption; if absorbed, then genotoxicity and reproductive toxicity data are needed; and

Dermal irritation and sensitization data at maximum leave-on concentrations of use.

The Panel acknowledged that anhydride monomers (eg, trimellitic anhydride) can be respiratory sensitizers, and exposures in the workplace to the anhydrides that are used in the production of these copolymers have resulted in numerous adverse effects. However, because the levels of residual monomer in nail products are expected to be minimal, exposure to trimellitic anhydride is not expected with cosmetic use and is not of concern.

Conclusion

The Panel concluded that Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer and Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer are safe in nail product formulations in the present practices of use and concentration described in this safety assessment; the data are insufficient to make a determination of safety on the use of these ingredients in all other types of cosmetic formulations.

The Expert Panel for Cosmetic Ingredient Safety also concluded that the available data are insufficient to make a determination that the following 4 trimellitic anhydride copolymers are safe under the intended conditions of use in cosmetic formulations:

Adipic Acid/CHDM/MA/Neopentyl Glycol/Trimellitic Anhydride Copolymer*

Isostearoyl Trimellitic Anhydride/Trimethylolpropane Copolymer*

Propylene Glycol/Sebacic Acid/Trimellitic Anhydride Copolymer*

Trimethylpentanediol/Isophthalic Acid/Trimellitic Anhydride Copolymer*

* Not reported to be in current use.

Footnotes

Author’s Note

Unpublished sources cited in this report are available from the Executive Director, Cosmetic Ingredient Review, 1620 L Street, NW, Suite 1200, Washington, DC 20036, USA.

Author Contributions

Fiume and Heldreth contributed to conception and design, contributed to acquisition, analysis, and interpretation; drafted manuscript; and critically revised manuscript. Bergfeld, Belsito, Hill, Klaassen, Liebler, Marks, Shank, Slaga, and Snyder, P. contributed to conception and design, contributed to analysis and interpretation, and critically revised manuscript. All authors gave final approval and agree to be accountable for all aspects of work ensuring integrity and accuracy.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The articles in this supplement were sponsored by the Cosmetic Ingredient Review. The Cosmetic Ingredient Review is financially supported by the Personal Care Products Council.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

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Safety Assessment of Trimellitic Anhydride Copolymers as Used in Cosmetics

Abstract

Keywords

Introduction

Chemistry

Definition and Structure

Chemical Properties

Method of Manufacture

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

Phthalic Anhydride/Trimellitic Anhydride/Glycols Copolymer

Impurities/Composition

Adipic Acid/Neopentyl Glycol/Trimellitic Anhydride Copolymer

Use

Cosmetic

Non-Cosmetic

Toxicokinetics

Absorption, Distribution, Metabolism, and Excretion

Toxicological studies

Developmental and Reproductive Toxicity Studies

Genotoxicity Studies

Carcinogenicity Studies

Dermal Irritation and Sensitization Studies

Ocular Irritation Studies

Clinical Reports

Case Reports

Summary

Discussion

Conclusion

Footnotes

Author’s Note

Author Contributions

Declaration of Conflicting Interests

Funding

Declaration of Conflicting Interests

Funding

References