Registration Dossier

Administrative data

two-generation reproductive toxicity
based on test type (migrated information)
Type of information:
experimental study planned
Study period:
Dependent upon feedback from ECHA

Data source

Materials and methods

Test guideline
according to guideline
OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)
GLP compliance:

Test material

Constituent 1
Reference substance name:
Sodium xylene sulphonate
Sodium xylene sulphonate

Test animals


Administration / exposure

Route of administration:
oral: unspecified

Results and discussion

Overall reproductive toxicity

Reproductive effects observed:
not specified

Applicant's summary and conclusion

Executive summary:

Three 90 day oral studies in the rat and mouse (according to / similar to OECD 408) and two 2 year chronic dermal studies on the rat and mouse (OECD 453) were performed using sodium xylenesulphonate. No distinct adverse effect on gross or histological appearance of the examined organs related to reproduction system was determined in 90d repeated dose study administered by orally to rats (Tilet al, 1969). A complete histopatho­logic examination in samples from each organ including genital systems were performed on all rats and mice that died prior to study termination, and on control rats and mice, and on 240 mg/kg rats and on 727 mg/kg mice at the end of the studies in the chronic carcinogenicity study. Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of sodium xylenesulphonate related to the incidences of nonneoplastic / neoplastic lesions in genital systems of male (epididymis, preputial gland, prostate, seminal vesicle, testes) and female (clitoral system, ovary, uterus) F344/N rats administered 60, 120, or 240 mg/kg and B6C3F1 mice administered 182, 364, or 727 mg/kg (NTP, 1998). One study on pre-natal developmental toxicity oral, rat was also observed no indications of developmental toxicity up to 3000 mg/kg day dose using the read-across substance of calcium xylenesulphonate (Ruetgers-Nease, 1994). However, the registrant agrees that some parameters of the two-generation reproductive toxicity study are missing in these studies. Also they do not address the fertility endpoint explicitly. Nevertheless, the combination of the results of the OECD 408 studies with the results of the dermal OECD 453 studies as well as the oral prenatal developmental toxicity study allows the assessment of the reproductive profile of sodium xylenesulphonate with the help of the observed findings. This is in line with the idea, that the information requirements under REACH are regarded as the evaluation of endpoints, which does not necessarily require data from specific studies. Because of a high correlation, histopathology data and organ weights from repeated dose studies may be used to assess male fertility (Mangelsdorf et al., 2003). These parameters, taken from 28/90-day studies, were in fact shown to be more sensitive than fertility parameters that were measured during multi-generation studies. It could also be shown that exposure for 4 weeks suffices for an assessment of male fertility, although 90-day studies have been regarded as superior in the past, because they cover a complete cycle of spermatogenesis (Mangelsdorf et al., 2003). If such a 28-day study shows neither relevantly elevated testis or ovary weights nor histopathological alterations in those organs, the weight of the evidence is that effects on reproduction are also not expected (German Federal Institute for Occupational Safety and Health; BAuA, 2003). A comparison of more than one hundred 90-day studies with two-generation studies that used the same test substance additionally showed that the NOAELs differed by less than the variation limit of studies, i.e. a factor of two (Janer et al., 2007). Therefore, the information gained from a two-generation study can be regarded as minimal if a 90-day study has been performed. When the critical targets of reproductive toxicity were identified using the Fraunhofer FeDTex database (Fertility and Developmental Toxicity in experimental animals database) in the pre-natal, one-, two- and three- generation studies of total 535, the adult stage within F1 generation was determined as mostly affected stage compared to the prenatal or postnatal stage. The alterations in body weight of F1 were identified as the most affected targets, while liver, kidney, testes, prostate, sperm parametersas well as developmental landmarks were determined as other important critical targets (Schulzet al,2014). As mentioned above, the repeated dose toxicity studies with sodium xylenesulphonate gave no hints for any reproductive or developmental toxicity. Against the background of the available data and due to animal welfare reasons (Article 25 of the REACH regulation), a two generation reproductive toxicity study is scientifically unjustified and will most probably not contribute to the overall risk assessment.

Nevertheless, ECHA has requested a 2-generation reproductive toxicity study (2-GRTS) in rats, oral route (test method: EU B.35/OECD 416) or an extended 1-generation reproductive toxicity study (EOGRTS) in rats, oral route (test method: OECD 443) to address this data requirement. The protocol used to conduct the 2-generation reproductive toxicity study (OECD 416) employs a flexible approach to the conduct of this study, permitting a scientifically based rationale that allows omitting the second generation (F2) on the basis of the results observed from the first generation. This flexibility in study design could save at least 2000 animals and is in accordance with Article 25 of the REACH Regulation, which states that testing on vertebrate animals shall be considered onlyas a last resort. This flexibility in the design of the OECD 416 protocol that allows omitting the second generation (F2) on the basis of the results observed from the first generation is supported by the following published evidence: Piersmaet al. investigated the necessity of producing a second generation to assess the potential for human health risks. The analysis included 498 rat multi-generation studies representing 438 different test substances. Detailed assessment of study reports revealed no critical differences in sensitivities between the generations on the basis of a consideration of all endpoints evaluated. This analysis indicated that the second generation mating and offspring will very rarely provide critical information (Piersmaet al., 2011). Martinet al.(2009) conducted an analysis on 329 multi-generation studies on 316 chemicals using the ToxRefDB dataset of USEPA. This analysis supports the hypothesis that the second, F2 generation in these 329 studies would rarely impact either the qualitative or quantitative evaluations of these studies. Janeret al.(2007) evaluated 176 multi-generation studies to assess potential differences between the first and the second generation and came to the conclusion that the second generation in the two-generation studies considered affected neither the overall NOAEL nor the critical effect, and had no impact on the ensuing risk assessment, nor on classification and labeling. Therefore, if the second generation had not been included in the reproductive toxicity test, the ensuing risk assessment and classification and labeling would have basically been the same for the substances that were considered. Myerset al.(2008) detected by analysis of 22 two-generation studies, 3 substances with adverse effects on reproductive performance solely in the F1 generation (not F0), but in these three studies concomitant effects would have also been triggered the mating of the F1 generation. No effects were seen in the original parental (F0) generation which would have activated the change from a one- to a two-generation study. Beekhuijzenet al.(2009) reviewed nine two-generation studies in rats and recommended that further breeding should not be conducted when the effects on parental fertility and fecundity are clear after first pairing. However, mating of the F1 generation is warranted if the effects on parental reproduction/breeding parameters are ambiguous. Likewise, if development and/or viability of the F1 generation are adversely affected, a second mating deserves considerations as potential exists for compromised reproductive integrity of the F1 animals. Rorijeet al.(2011) analyzed the possible impact on classification and labeling decisions of effects observed in second generation parental (P1) and offspring (F2) parameters in multi-generation studies. This was done for 50 substances classified as reproductive toxicants in Europe, for which a multi-generation study was available. The analysis shows that, except for a single case, effects observed in second generation mating and offspring did not impact the decision on classification and labeling for reproductive toxicity. Moreover, the single case where second generation mating and offspring effects appeared to be instrumental for classification would be identified as a reproductive toxicant in an extended one-generation reproductive toxicity study without second generation mating and offspring.Schultzet al.(2014) compared the responsiveness of the different generations and developmental stages in studies on reproductive toxicity. The F1 generation is identified as the most responsive generation in more than 50% of one-generation and multi-generation reproduction studies. Within the F1 generation the adult stage is mostly affected compared to the prenatal or postnatal stage. The findings in the F2 generation have shown a higher responsiveness than F1 only in 3% of the studies. Although in 29 studies new effects are observed in F2 offspring compared to F1 irrespective of dose levels, overall no severe new effects have emerged that would change classification and labeling and justify an F1 mating. The registrant therefore concludes that the extended one-generation reproductive toxicity study in rats, oral route (based on OECD 416 test method) will in most cases be sufficient in order to allow for a proper risk assessment including valid classification and labeling. However, the registrant acknowledges that there might be certain circumstances where it might be necessary to include the second generation (full OECD 416) to produce the F2 generation which shall be kept until weaning, namely if the results obtained during the study are ambiguous and do not allow a clear decision towards classification or no classification. Whether to produce the F2 generation or not should be based on a scientific point of view and decided by the study director. Hence, the registrant agrees to perform the 2-generation reproductive toxicity study. The registrant proposes to perform the OECD 416, oral route using rats, in a tiered approach (assess if 2ndgeneration part in OECD 416 is needed). This test will be started following a final decision pursuant to Article 51 of the REACH regulation.


NTP Technical report on the toxicology and carcinogenesis studies of technical grade sodium xylenesulfonate (CAS No. 1300-72-7) in F344/N rats and B6C3F1 mice (dermal studies). NTP TR 464, NIH Publication No. 98-3880, NIH, USA, 1998.

Til HP, Feron VJ, Huismans JW and de Groot AP, Subchronic toxicity study with Halvopon OR in albino rats, Central Inst for Nutrition and Food Research Report No: R2822, UK, 1969.

Mangelsdorf I, Buschmann J, Orthen B. Some aspects relating to the evaluation of the effects of chemicals on male fertility. Reg Toxicol Pharmacol. 2003; 37: 356-369.

Mangelsdorf I, Buschmann J. Extrapolation from results of animal studies to humans for the endpoint male fertility. German Federal Institute for Occupational Safety and Health (BAuA) Reserch Report, Forschungsbericht Fb 984. 2003.

Janer G, Piersma, AH, Vermeire T, Slob W. A retrospective analysis of the added value of the rat two-generation reproductive toxicity study versus the rat subchronic toxicity study. Reproductive Toxicol. 2007; 24: 103-113.

Schultz F, Batke M, Mangelsdorf I, Pohlenz-Michel C, Simetska N, Lewin G. Sensitivity of different generations and developmental stages in studies on reproductive toxicity. Toxicol. Lett. 2014 Feb; S0378-4274.

Piersma AH, Rorije E, Beekhuijzen ME, Cooper R, Dix DJ, Heinrich-Hirsch B, Martin MT, Mendez E, Muller A, Paparella M, Ramsingh D, Reaves E, Ridgway P, Schenk E, Stachiw L, Ulbrich B, Hakkert BC. Combined retrospective analysis of 498 rat multi-generation reproductive toxicity studies: on the impact of parameters related to F1 mating and F2 offspring. Reprod Toxicol. 2011 May; 31(4):392-401.

Martin MT, Mendez E, Corum DG, Judson RS, Kavlock RJ, Rotroff DM, Dix DJ. Profiling the reproductive toxicity of chemicals from multigeneration studies in the toxicity reference database. Toxicol Sci. 2009 Jul; 110(1):181-90.

Janer G, Hakkert BC, Slob W, Vermeire T, Piersma AH. A retrospective analysis of the two-generation study: what is the added value of the second generation? Reprod Toxicol. 2007 Jul; 24(1):97-102.

Beekhuijzen M, Zmarowski A, Emmen H, Frieling W. To mate or not to mate: a retrospective analysis of two-generation studies for evaluation of criteria to trigger additional mating in the extended one-generation design. Reprod Toxicol. 2009 Sep; 28(2):203-8.

Rorije E, Muller A, Beekhuijzen ME, Hass U, Heinrich-Hirsch B, Paparella M, Schenk E, Ulbrich B, Hakkert BC, Piersma AH. On the impact of second generation mating and offspring in multi-generation reproductive toxicity studies on classification and labelling of substances in Europe. Regul Toxicol Pharmacol. 2011 Nov; 61(2):251-60.

Myers DP, Willoughby CR, Bottomley Am, Buschmann J. An analysis of the results from Two-Generation Reproduction Toxicity Studies to assess the value of mating animals of the second (F1)generation for the detection of adverse treatment-related effects on reproductive performance. Reprod Toxicol. 2008 Sep; 26(1):47-50.