Registration Dossier

Administrative data

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route
Dose descriptor:
NOAEL
600 mg/kg bw/day
Additional information

The OECD High Molecular Weight Phthalate Ester (HMWPE) Category consists of phthalate esters with an alkyl carbon backbone with 7 carbon (C7) atoms or greater. The category is formed on the principle that substances of similar structure have similar toxicological properties. The data available on high molecular weight phthalates demonstrate that members of this category have similar biological activities and toxicological properties; this verifies the use of read-across data as an appropriate approach to characterize endpoints. DIUP (C11) is a high molecular weight phthalate ester. Where data maybe insufficient for DIUP, then DIDP (C10), DTDP (C13), and C9 -11 phthalate ester, which are also high molecular weight phthalate esters, are used as read-across substances to provide toxicological information. 

In two 2-generation reproductive toxicity studies, there were no changes in reproductive indices and no effects on fertility. Additionally, there were no effects on reproductive organs in the repeated dose study. Accordingly, the overall conclusion from these studies was that DIDP has no effect on fertility. DIDP did produce a small, statistically significant decrease in postnatal survival indices which was observed in the second generation of both of the two-generation studies leading to the NOAEL of 0.06% (33-76 mg/kg/d). These effects were found in association with maternal toxicity: reduced body weight, instances of increased kidney weight, and /or liver enlargement. Therefore, the effects on post-natal survival are considered secondary rather than a direct effect of DIDP on the rat pups. Cross fostering studies demonstrated that post natal body weight effects observed were reversible when post natal exposure to DIDP via the dams stopped. See developmental section for further discussion on this effect.

DTDP has been assessed in a combined repeat dose and reproductive/developmental toxicity screening test (OECD 422, Japan Ministry of Health and Welfare, 1997, DTDP CAS 119-06-2). The registrant does not have access to the full study report but the following information is publically available. Sprague-Dawley rats were administered 10, 50 or 250 mg/kg/day of DTDP by oral gavage. Males were treated for 42 days and females from 14 days prior to mating to day 3 of lactation. Maternal effects were observed at 50 and 250 mg/kg/day, consisting in suppression of body weight gain, increase in liver weight, and hypertrophy of centrilobular hepatocytes. There were no adverse effects observed on the number of corpora lutea, implantation sites, number of pups born, or on pup weight, sex ratio and external morphological appearance through post-natal day 4. A slight non-significant decrease in the pup viability at post-natal day 4 was reported at 250 g/kg/day, possibly related to poor lactation caused by maternal toxicity. It is interesting to note that this same effect of decreased pup viability (in the F2 generation) has been observed for DIDP (Hushka et al. 2001) with a NOAEL of 33 mg/kg/day. The effect was also observed in association with maternal toxicity (reduced body weight, increased kidney and/or liver enlargement). Therefore the effects are considered to be secondary rather than a direct effect of DIDP. In the DIDP study cross-fostering was carried out and demonstrated that post-natal body weight effects were reversible when high dose pups were cross-fostered with control animals.

Reproductive effects were also investigated on a C9-11 phthalate ester in a 2 -generation reproductive toxicity study by Willoughby et al. (2000). The test substance did not impair reproductive function in rats at any dose level tested (100-1000 mg/kg/day). Signs of systemic toxicity were observed at the highest dose group. The 1000 mg/kg bw/day males showed reduced body weights in both the F0 and F1 generations. There was no impairment of fertility, fecundicity, or development in either generation, but pup body weights were slightly reduced in the highest dose group over the weaning period. A NOAEL of 1000 mg/kg/day is supported by the data for reproductive function and 500 mg/kg/day for general toxicity.


Short description of key information:
Reproductive toxicity of DIDP was evaluated in two 2-generation reproductive toxicity tests (key data published in Hushka et al., 2001). Rats were exposed by dietary administration to levels of DIDP ranging from 0.0 to 0.8% (or approximately 15 to 600 mg/kg/day). There were no statistically significant differences in male mating, male fertility, female fertility, female fecundity, or female gestational indices between treated and control animals in the P1 or P2 generation. Mean days of gestation and mean litter size and of the treated and control groups were similar. There were no statistically significant differences in the mean sex ratio of the treated offspring compared with controls. It was concluded that fertility was unaffected by DIDP treatment at levels up to 600 mg/kg/day. Regarding parental toxicity, in both studies, liver and kidney effects were observed in the P1 generation. Increased liver weights and associated hepatocellular hypertrophy were observed at dietary concentrations of 0.4% and greater in both studies. These dietary concentrations also produced kidney effects that were associated with alpha 2u microglobulin toxicity, a male rat specific effect and thus not relevant to humans. In the first study, minor effects on the liver were observed at 0.2% (103 – 203 mg/kg/day). In the second study, no hepatic effects were recorded at this concentration (114 – 225 mg/kg/day). As there is a range in intake levels, it is likely this dietary concentration results in ingestion of DIDP at or near the NOAEL for systemic effects from repeated dosing. In the P2 generation liver and kidney changes were observed in the P2 males. A NOAEL of approximately 33 to 76 mg/kg bw/d (0.06%) was derived with the range being due to the fact received doses differed depending on the period considered. Like for the P1 generation, up to the highest dose tested no overt signs of reproductive toxicity were reported, and no effects were observed on fertility parameters.

Effects on developmental toxicity

Description of key information
An array of HMWPEs were tested in either OECD 414 developmental toxicity testing, OECD 416 reproductive toxicity testing or an OECD 422 screening test with a range of doses. Of the nine representative studies, no effects were observed in 3 studies and NOAELs were set at the highest dose tested. In 4 of the remaining 6 studies skeletal variations were observed. The adversity of the type of skeletal effects seen in HMWPE studies have been questioned, in particular the increase in supernumerary ribs as is discussed in detail as part of the WoE. In these four studies the lowest dose producing the effect was 250 mg/kg/d. Doses were tested below this level in the other studies that did not show an effect. As such the NOAEL for HMPWEs for skeletal variations is 100 mg/kg/d. The 2 other LOAELs were determined by either "slightly decreased pup body weight/pup weight gain" or a small but significant increase in pup mortality at the highest dose tested. The most sensitive NOAEL for these effects is 33 mg/kg/d. The true developmental NOAEL for the registered substance is likely higher, however, 33 mg/kg/d is selected as a conservative NOAEL for this substance based on the totality of the data. This value was used for the recent risk assessment conducted by ECHA for DINP/DIDP and not found to be associated with risk to women of child bearing age. See document "Developmental Data for HMWPE" attached in section 13 for table and graphical depiction of data.
Effect on developmental toxicity: via oral route
Dose descriptor:
NOAEL
33 mg/kg bw/day
Additional information

Developmental toxicity Endpoint Summary

Developmental toxicity and reproductive toxicity testing on the registered substance has not been conducted. However, a developmental toxicity study has been conduction on a phthalate of the same structural nature, as well as several studies for structurally similar substances that are informative and should be considered in an overall weight of the evidence and as supporting information adequate for the purposes of hazard identification, classification and labeling and risk assessment. Based on the weight of evidence the substance is not expected to be a developmental toxicant and no new information is expected to be gained through additional animal testing.

Key data elements or information considered in this overall WOE assessment are as follows:

 

1.  OECD414 prenatal developmental toxicity study on DUDP. In this study, no evidence of adverse effects were observed. These data support a low developmental toxicity potential for the registered substances

2.  Five prenatal developmental toxicity studies (OECD414) on read across substances (analog approach). In all five studies no evidence of adverse developmental effects were observed. Accordingly, these data support a low developmental toxicity potential for the registered substances

3.  Three reproductive toxicity studies on read across substances (analog approach) demonstrating no effects on fertility or reproductive performance in the parental animals.  

4.  Data demonstrate differential reproductive/developmental toxicity outcomes between LMWPE and HMWPE. Based on the many studies conducted on LMWPE and HMWPE, the differences in the reproductive and developmental toxicity profile clearly lies in the structural differences between the phthalates themselves, namely the carbon backbone in the ester side chain. Primary alkyl chains in the range C4-C6 are optimal for induction of reproductive and developmental toxicity. Phthalate esters with a carbon backbone of C7 and greater have similar developmental and reproductive toxicity profiles.

The available information summarized above, which individually may not be adequate by themselves to meet the information requirement, provides reliable, relevant and adequate information for assessing this endpoint when considered together. Based on these data, it is not expected that the registered substance would be a developmental toxicant. The data are described in more detail below and the reliability, relevance and adequacy evaluated.

A developmental toxicity study conducted on the phthalate of the same structural nature, DUDP (alkyl carbon backbone with 11 carbon (C) atoms (C11)), was used to inform the developmental toxicity of the registered substance. DIUP (registered substance) is described as a di-ester of phthalic anhydride and isoundecyl alcohol. Based on HNMR analysis, DIUP has an average number of branches per alcohol molecule of 2.4, and an average carbon number of 11.15. The predominant alcohol chains found in the ester are di-methyl nonanols (dimethyl C9). DIUP can be described as containing mainly C11-branched isomers (total carbon number (C11), mainly C9 with some C8/C10 backbone, table of backbone range and representative isomer attached in section 13). This differs slightly from the test material (DUDP; CAS 3648-20-2), which is described as having over 80% a straight ester side chain of eleven carbons, and with some methyl C10 branched material (total carbon number (C11), mainly C11 with some C10 backbone). DUDP shares the same number of carbons in the alkyl chain as the registered substance with overlap of the longest linear carbon chain lengths. This substance overlaps the registered substance and brackets the high end of the alkyl chain analogue read across.

Saillenfait al. (2013) conducted a prenatal developmental study on diundecyl phthalate (DUDP; CAS 3648-20-2), a high molecular weight phthalate ester which has over 80% a straight ester side chain of eleven carbons, and with some methyl C10 branched material (total carbon number (C11), mainly C11 with some C10 backbone). DUDP showed no statistically significant effects on body weight, body weight gain and food consumption of pregnant Sprague-Dawley rats up to and including 1000 mg/kg/day, which was the highest dose tested. The number of live fetuses, percent of post-implantation loss and of resorptions, and fetal body weights were not affected by DUDP. An increased incidence of short supernumerary lumbar ribs was observed in fetuses from the 500 and 1000 mg/kg/day DUDP dose groups, compared to the control, statistically significant at 1000 mg/kg/day. As described in more detail in the sections below, rudimentary supernumerary ribs are usually considered as common reversible variants in rodent bioassays (Wickramaratne et al. 1988, Chernoff et al. 1991, Chernoff et al. 2004, Tyl et al. 2007). No other significant changes in the incidences of any other skeletal variations at any dose of DUDP were observed. There was no evidence of adverse developmental effects at any dose level. DUDP did not induce any anomaly of the reproductive tract in fetuses. Male anogenital distance (AGD) was identical to control at 250 mg/kg/day, and it was slightly, although not significantly, reduced at 500 and 1000 mg/kg/day (3–4%). A statistically significant difference was only noted at the intermediate dose of 500 mg/kg/day, after fetal weight adjustment. However, when considering the variability in AGD in control animals (as described below) this is not considered biologically significant.

Saillenfait 2013 simultaneously evaluated the developmental toxicity of two high molecular weight dialkyl phthalate esters, diundecyl phthalate (DUDP) and ditridecyl phthalate (DTDP). Sprague-Dawley rats supplied by Charles River Laboratories (Saint-Germain-sur-l′Arbresle, France) were housed overnight with adult males from the same strain and supplier. Mated females were randomly assigned to treatment groups by stratified randomization so that mean body weights on GD 0 did not differ among treatment groups. Given the random nature of the assigned groups the animals from the DTDP study can be compared to the DUDP animals. AGD distances for the control animals from the DTDP study were smaller than all dose groups in the DUDP study, thus AGD value for the DUDP data lies between the control values for the concurrent experiments (raw (Fig 1A) & scaled (Fig 1B), attached section 13). When the AGD values are put in context of the entire information available, it is clear no treatment related effects have occurred in any group.

Additionally, the same laboratory has conducted multiple studies in the same strain of animals, using the same protocol with other phthalates. These studies provide the basis for historical control ranges of observed AGD in untreated animals. Based on these data, the DUDP data, at all doses, are within that range (Fig 2, attached section 13) (Saillenfait et al. 2009, 2011a, 2011b, & 2013). Given the lack of dose response and the lack of difference versus concurrent DTDP controls and historical controls this effect is not considered biologically significance. Discussion of the Saillenfait paper along with figures comparing control AGD data to AGD data from the DUDP study are provided in the document "Discussion on Saillenfait publication w/ Figures" attached in section 13 of IUCLID.

An evaluation of the literature for reproductive and developmental endpoints for a series of analogous high molecular weight phthalates was conducted to support these conclusions. Similarity among all of these analogues, including the registered substance, has been previously described by the OECD as part of the documentation on high molecular weight phthalate esters (HMWPE) (HMWPE, SIAM, 19-22 October 2004). Substances in this evaluation are identified asortho-phthalates esters with an alkyl carbon backbone with 7 carbon atoms or greater (HMWPE, SIAM 19, 19-22 October 2004). The structure activity relationship outlined in the OECD evaluation was independently assessed by the Netherlands, National Institute for Public Health and the Environment (RIVM) (Fabjan et al 2006). The RIVM assessment concluded “phthalates with the alkyl side-chain length from C4 to C6 produce similar severe reproductive effects in experimental animals”. These two resources give independent confirmation of the proposed structure activity relationship, further information is provided below on how branching of the side chain impacts this relationship.

Ortho-phthalates have a similar pathway of breaking down with metabolites formed according to the differences in C-backbone lengths of the parent compound. A more highly branched phthalate will have a lower carbon-backbone than a linear phthalate of the same identified carbon number (i.e. a highly branched C7 phthalate will have a carbon-backbone less than C7 in comparison to a linear C7 phthalates whose carbon-backbone will also be C7). This creates a differentiation between total carbon number and carbon number of the longest linear chain length which is dependent upon branching.

The basis for the OECD and RIVM assessments are the different reproductive and developmental effects demonstrated by different phthalates that are dependent on carbon backbone number of the ester side chain. The marked difference of the LMWPE and HMWPE in terms of reproductive and developmental toxicity is noteworthy and makes read-across, in the context of weight of the evidence considerations, to other HMWPEs for reproductive and developmental toxicity an appropriate adaptation to the standard information requirements of Annex X, 8.7.2 and 8.7.3 of the REACH Regulation for the registered substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation. The use of the following data to support the DIUP registration by WoE with other HMWPE is elaborated in the next paragraphs. A figure compiling the substance identity for the phthalate esters used in the WoE titled "Phthalate Alcohol Carbon Backbone Distribution" has been attached to section 13.

Hellwig et al. 1997 assessed the developmental toxicity of several phthalate esters in both the LMWPE and HMWPE carbon backbone range and found significant differences in the responses elicited. Pregnant Wistar rats were exposed to three LMWPEs (DEHP, DIPP, or di-711-phthalate) and two HMWPEs (DINP or DIDP) by gavage at dose levels of 40, 200 or 1000 mg/kg/day on GD 6 through GD15. At 1000 mg/kg/day DEHP showed clear foetotoxicity, embryolethality and teratogenicity. No significant effects were recorded at 40 and 200 mg/kg/day. DIPP and Di-711 phthalate, a phthalic ester with linear and branched components generating over 1/3rdof the total phthalate esters with side chains in the C4- C6 backbone length (i.e. LMWPE), showed a similar spectrum of effects. Both HMWPEs showed minor effects at 1000 mg/kd/day: mild signs of maternal toxicity and an increased incidence of skeletal variations, but no teratogenic effects.

Another study by McKee et al. (2006) assessed the developmental toxicity of di-isoheptyl phthalate (DIHP), a branched phthalate ester with seven carbon alkyl side chains with predominantly methyl-hexyl isomers (>80%) as constituents i.e. a LMWPE. Significant reductions in uterine weight, increased resorptions and reduced fetal weight and survival at the highest dose group (750 mg/kg/day) were observed. Fetal examination revealed significant increase in external, visceral and skeletal malformations and variations in the 750 mg/kg dose group. There was no evidence of developmental toxicity in the intermediate dose (300 mg/kg/day) group. Comparatively, the linear C8 phthalate ester DnOP had no teratogenic effects after oral administration to Sprague-Dawley rats on GD6 through GD 20 at doses up to 1000 mg/kg/day in a study by Saillenfait et al. (2011b). DnOP did not affect the embryo-fetal survival, intra-uterine growth, AGD of male fetuses, and fetal testicular migration. However, an increased incidence of supernumerary lumbar ribs was observed at 250 mg/kg/day and higher doses.

A study by Saillenfait et al. (2013b) assessed the developmental toxicity of di-isooctyl phthalate (DIOP), composed of 70-75% of isomers with a C4-C6 backbone and less than 25% of isomers with a backbone≥7 i.e. a LMWPE. There was a significant increase in resorptions at the highest dose of 1000 mg/kg/day and a reduction in fetal weights at 500 and 1000 mg/kg/day. No increase in the incidence of external, visceral, or skeletal malformations in the fetuses were observed. Short supernumerary lumbar rib was the only skeletal variant to be significantly increased at 500 and 1000 mg/kg/day. Several studies in rats and mice have shown that short supernumerary lumbar ribs may disappear postnatally, probably becoming a part of the lateral vertebral process (Wickramaratne et al. 1988, Chernoff et al. 1991, Chernoff et al. 2004, Tyl et al. 2007).

The developmental toxicity of DIDP, a HMWPE, was investigated in Sprague-Dawley rats by Waterman et al. (1999). DIDP was administered by gavage to mated rats at doses of 0, 100, 500 and 1000 mg/kg/d on gestation days (GD) 6 through 15. Cesarean sections were performed on GD 21 and fetuses removed for evaluation. Maternal body weight gain and food consumption were significantly reduced at 1000 mg/kg/day during the exposure period. Fetal morphologic observations showed no treatment related effects, except for an increased frequency of skeletal variations at the maternally toxic dose level of 1000 mg/kg/day. The most prominent skeletal variation observed was a significantly increased incidence of rudimentary lumbar ribs/litter at 1000 mg/kg/day. Rudimentary lumbar ribs were subjectively defined as those less than one half the length of the 13ththoracic rib. An increase in supernumerary ribs on the seventh cervical vertebrae/litter was also apparent at the highest dose group. No other exposure-related increase in skeletal variations was observed among any of the treated groups in the study.

In rodent fetuses, supernumerary ribs are known to occur spontaneously, following non-specific maternal toxicity (e. g. maternal stress), and following exposure to a number of chemicals (Kavlock et al. 1985, Chernoff et al. 1987, Beyer et al. 1986). The increase in fetal variations observed by Waterman et al. (1999) could indeed have been secondary to maternal toxicity. Maternal effects at 1000 mg/kg/day consisted of reduced body weight gain and food consumption during the treatment period (GD 6 through GD15). However no statistically significant differences were observed in maternal body weight, body weight change, or food consumption during the overall gestation interval (GD 0 through GD21). The reduction in maternal food consumption was likely the reason for the concomitant decrease in maternal body weight gain during the exposure period.

The biological significance of supernumerary ribs, especially in the lumbar region, has been well studied. Supernumerary ribs are not regarded as malformations, but rather as minor deviations in skeletal structure commonly observed in control animals (Kimmel et al. 1973, Harris et al. 1994, Chernoff et al. 1991, Mylchreest et al. 2013, Tyl et al. 2007). Chernoff et al. 1991 have shown that the incidence of rudimentary (short) lumbar ribs declines during postnatal development in rats. Another study showed furthermore that the decline of supernumerary ribs during postnatal development was accompanied by an increase in the prevalence of a fully ossified transverse process on the first lumbar vertebrae (Wickramaratne et al. 1988). These authors concluded that supernumerary ribs in rats are a result of developmental delays and not considered to be a manifestation of a teratogenic event.

The data of Waterman et al. (1999) are consistent with data from a developmental toxicity study by Hellwig et al. 1997, where pregnant Wistar rats were exposed to DIDP by gavage at dose levels of 40, 200 or 1000 mg/kg/day on GD 6 through GD 15. Mild signs of maternal toxicity and an increased incidence of skeletal variations, but no teratogenic effects were seen at 1000 mg/kg/day. No signs of maternal or fetal toxicity were observed at 40 and 200 mg/kg/day.

In the absence of more profound signs of developmental toxicity (e. g. growth retardation, embryolethality or malformations), the supernumerary ribs observed in the key study by Waterman et al. (1999) were considered as minor and potentially reversible. Both maternal and developmental NOAELs were therefore established at 500 mg/kg/day (Waterman et al. 1999, European Chemicals Bureau 2003) and 33 mg/kg/day (Hushka et al 2001, European Chemicals Bureau 2003). In reviewing the draft European Chemicals Bureau Risk Assessment on DIDP, the Scientific Committee on Toxicity, Ecotoxicity and the Environment (CSTEE 2001) agreed with the maternal NOAEL of 500 mg/k/day but supported the NTP-CERHR Expert Panel report which concluded that 100 mg/kg/day is more appropriate based on a statistical re-evaluation of cervical and accessory 14th ribs. CSTEE did not agree with the NTP-CERHR Expert Panel with respect to their choice of a NOAEL of 40 mg/kg/day based on an increase in affected fetuses per litter with variations (Hellwig et al 1997). CSTEE considered the variations seen may be transient and were not observed in the two generation study. CSTEE did agree with the NOAEL of 33 mg/kg/day for DIDP based on the two-generation study. ECHA (2013) in reviewing all of this information and expert evaluations concluded that the NOAEL of 33 mg/kg/day (Hushka et al 2001) for DIDP is the most relevant, and that the developmental NOAEL for skeletal variations is 100 mg/kg/day (Waterman et al 1999) and for foetal variations is 40 mg/kg/day (Hellwig et al 1997). ECHA did not state why they disagreed with the CSTEE with respect to the NOAEL of 40 mg/kg/day (Hellwig et al 1997).

The decrease in pup viability indices in F2 (day 1 and day 4) in the DIDP two-generation study (Hushka et al. 2001) as well as skeletal variations in developmental studies on DIDP and DTDP (Waterman et al. 1999, Hellwig et al. 1997 and Saillenfait et al. 2013) are not sufficient to justify classification for fertility, developmental or lactational effects (ECBI/51/00 – Rev.2 23.11.00). This opinion on fertility, developmental and lactational effects for DIDP was concluded during the May 2000 meeting of the EU CMR and Pesticides Working Groups on Classification and Labelling (European Commission Working Group. 2000a; 2000b) and included in the EU Risk Assessment for DIDP. This conclusion is quoted by ECHA (2013) in their report “Evaluation of new scientific evidence concerning DINP and DIDP – In relation to entry 52 of Annex XVII to REACH regulation (EC) No. 1907/2006 – Final Review Report”.

A standard developmental toxicity study is also available by Fulcher et al. (2001) on a C7-9 phthalate (D79P) and a C9-11 phthalate (D911P), a mixture primarily composed of phthalate esters with linear alkyl chains of n-heptyl, n-octyl and n-nonyl; and n-nonyl, n-decyl and n-undecyl respectively. Sprague-Dawley rats were administered 0, 250, 500 or 1000 mg/kg/day by gavage on GD1 through GD19. For both phthalates no evidence of maternal toxicity, fetal mortality or teratogenicity was observed. There were only significant increases in the incidence of fetuses with dilated renal pelvis at 1000 mg/kg/day and with supernumerary lumbar ribs at 500 and 1000 mg/kg/day. The increase in 14th rudimentary supernumerary ribs, defined as being less than 50% the length of the 13th rib, are a common skeletal variation that occurs spontaneously at a high frequency in rats. A survey of 2320 Sprague Dawley rat litters form control groups in 109 studies terminated at GD20 reported a maximum incidence of 55% (MARTA & MWTA 1996). Furthermore, this variation seems spontaneously reversible in rats and its incidence diminishes as rats mature (Wickramaratne et al. 1988).

Information is available, though registrants do not have access to the fully study report. on a reproductive/developmental study on DTDP is available. DTDP has been assessed in a combined repeat dose and reproductive/developmental toxicity screening test (Japan Ministry of Health and Welfare, 1997, DTDP CAS 119-06-2). Sprague-Dawley rats were administered 10, 50 or 250 mg/kg/day of DTDP by oral gavage. Males were treated for 42 days and females from 14 days prior to mating to day 3 of lactation. Maternal effects were observed at 50 and 250 mg/kg/day, consisting in suppression of body weight gain, increase in liver weight, and hypertrophy of centrilobular hepatocytes. There were no adverse effects observed on the number of corpora lutea, implantation sites, number of pups born, or on pup weight, sex ratio and external morphological appearance through post-natal day 4. A slight non-significant decrease in the pup viability at post-natal day 4 was reported at 250 g/kg/day, possibly related to poor lactation caused by maternal toxicity. It is interesting to note that this same effect of decreased pup viability (in the F2 generation) has been observed for DIDP (Hushka et al. 2001) with a NOAEL of 33 mg/kg/day. The effect was also observed in association with maternal toxicity (reduced body weight, increased kidney and/or liver enlargement). Therefore the effects can be considered to be secondary rather than a direct effect of DIDP. In the DIDP study cross-fostering was carried out and demonstrated that post-natal body weight effects were reversible when high dose pups were cross-fostered with control animals.

In addition to the Japan Ministry of Health and Welfare study, a prenatal developmental study was conducted by Saillenfait et al. (2013) on ditridecyl phthalate (DTDP, CAS 119-06-2). This phthalate is a high molecular weight phthalate ester which has predominantly thirteen carbons straight alkyl side chain with some methyl branching (C12 methyl branched isomers), which is a longer carbon backbone than the registered substance (DIUP can be described as containing mainly C11-branched isomers). DTDP, in the Sailenfait study, had no substantial effects on body weight, body weight gain, and food consumption of pregnant Sprague-Dawley rats up to and including 1000 mg/kg/day, which was the highest dose tested. DTDP did not induce any anomaly of the reproductive tract in fetuses. There was no significant change in fetal anogenital distance at any dose level. No treatment related effects were detected after external, visceral and skeletal examination of the fetuses. Several common skeletal variations occurred occasionally and/or were scattered with no significant differences between treated and control groups. The authors concluded that DTDP did not induce developmental toxicity at dosages as high as 1000 mg/kg/day.

Finally, toxicity to reproduction of di-(2-propylheptyl) phthalate (DPHP) was evaluated in a Two-Generation Reproduction Toxicity Study performed under GLP according guidelines OECD 416, EU Method B.35 and EPA OPPTS 870.3800 (CPSC,Robust summary DPHP 010610). DPHP is an ester plasticiser based on isomeric C10 alcohols. The mono ester has a total carbon number of C10 and a primary carbon backbone of C7. This molecule demonstrates how branching in itself is not problematic, but rather how the branching effects the longest linear chain length of the ester side chain. The study included the enhanced endpoints that evaluate perturbation of the endocrine system, highlighting the lack of effect for phthalate esters with a carbon backbone of C7 and greater. The test substance was administered to groups of 25 male and 25 female young Wistar rats via the diet over two parental (F0 and F1) generations with dietary target dosages of 0, 40, 200 and 600 mg/kg bw/day. The test substance concentrations in the diet were adjusted regularly throughout the study to maintain the intended dose levels. It was found that di-(2-propylheptyl) phthalate neither influenced fertility nor reproductive performance in the parental animals, nor viability, sex ratio and sexual development/maturation of offspring, up to the top dose of 600 mg/kg bw/day. Also, neither anogenital distance/anogenital index nor the number and percentage of F1 and F2 male pups having areaolae were influenced in all treated groups.

Similar to the other HMWPEs, the NOAEL for developmental toxicity of DPHP in the F1 and F2 progeny is 200 mg/kg bw/day, based on slightly decreased pup body weights/pup weight gain in the second third of lactation. Importantly, the developmental effects do not occur in the absence of parental toxicity. 

In this detailed study which includes additional endocrine sensitive endpoints (i.e. AGD, nipple retention, etc.), there was no evidence of endocrine activity at this carbon chain length (C10), with a C7 backbone. This is in contrast with LMWPEs with carbon backbones in the C4-C6 range where potentially endocrine mediate adverse effects are noted with similar study designs (attached section 13). These findings support that phthalates in the carbon range of the registered substance are not developmentally toxic and do not have adverse effects on endocrine mediated endpoints. 

Based on the many studies conducted on LMWPE and HMWPE, the differences in the reproductive and developmental toxicity profile clearly lies in the structural differences between the phthalates themselves, namely the carbon backbone in the ester side chain. Primary alkyl chains in the range C4-C6 are optimal for induction of reproductive and developmental toxicity. In contrast HMWPEs including DINP, DIDP, DPHP, DUDP, and DTDP elicit only minor skeletal variations and some effects on pup viability in animal studies – these effects are seen in association with maternal toxicity. In addition substances with mainly C7 carbon backbones in the alkyl side chains such as D79P (at least 80% linear, with predominantly mono-2-methyl branching) and DPHP (mono 2-propyl branching) for example do not show the reproductive and developmental effects of LMWPE. 

This contrasts with di-711-phthalate (CAS no. 68515-42-4, 1,2-Benzenedicarboxylic acid, di-C7-11-branched and linear alkyl esters), which has a high degree of branching and therefore a high level of alkyl side chains with a C6 backbone, resulting in the presence of primary alkyl chains in the range optimal for developmental toxicity. This substance is classified for developmental effects under the CLP (Category 1B) and is included in the REACH Candidate list. The differences in study data clearly delineates the structure activity relationship of phthalate esters with carbon backbone number of C7 and above with those that contain primarily C4, C5, and C6 carbon backbones. 

As emphasized above, the HMWPE are phthalate esters with an alkyl carbon backbone with 7 carbon (C7) atoms or greater. The data available on high molecular weight phthalates demonstrate that phthalate esters consisting predominantly of side-chains with a carbon backbone of C7 and greater, have similar biological activities and toxicological properties; this verifies the useful information provided by these phthalates in the WoE for DIUP. It is important to note that branched C7 Phthalate Esters will contain a carbon backbone of C6 or lower, and therefore share the toxicological profile of LMWPEs. The developmental/reproductive results for the branched di-711-phthalate would be predicted by the structure activity relationship that has been established for LMWPEs. This is not the case for DIUP (a C11 phthalate with predominantly a C9 backbone), which is a HMWPE. Where individual data on DIUP may be potentially insufficient for the purposes of hazard identification, classification and labeling and risk assessment, multiple developmental and reproductive studies for a range of phthalate esters clearly demonstrate a structure activity relationship. This provides an overall weight of the evidence adequate for the purposes of hazard identification, classification and labeling and risk assessment. An independent assessment of the substances identified as HMWPE in the provided WoE, including the registered substance, was conducted, for examples, as part of the OECD High Production Volume (HPV) programme (2004). The conclusion of the assessment agrees with the provided WoE that additional testing for these substances is not necessary: “[t]he chemicals in this category [HMWPE] are currently of low priority for further work because of their low hazard profile”.

 

Additional references

Beyer et al. 1986, The induction of supernumerary ribs in rodents: role of the maternal stress, Teratogen Carcinogen Mutagen, 6, 419-429

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Chernoff et al. 1991, Significance of supernumerary ribs in rodent developmental toxicity studies: postnatal persistence in rats and mice. Fundam Appl Toxicol, 17, 448-453

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Saillenfait et al. 2009, Differential developmental toxicities of di‐n‐hexyl phthalate and dicyclohexyl phthalate administered orally to rats. Journal of Applied Toxicology, 29(6), 510-521.

Saillenfait et al. 2011a, Developmental toxic potential of di‐n‐propyl phthalate administered orally to rats. Journal of Applied Toxicology, 31(1), 36-44.

Saillenfait et al. 2011b, Prenatal developmental toxicity studies on di-n-heptyl and di-n-octyl phthalataes in Sprague-Dawley rats, Reproductive Toxicology, 32, 268-276

Saillenfait et al. 2013a, Prenatal developmental toxicity studies on diundecyl and ditridecyl phthalates in Sprague-Dawley rats. Reproductive Toxicology, 37, 49-55.

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Justification for classification or non-classification

No classification for repeat dose effects is indicated according to the general classification and labeling requirements for dangerous substances and preparations (Directive 67-548-EEC) or the classification, labeling and packaging (CLP) regulation (EC) No 1272/2008.