Appendices 1-18 to: Report on the Health Effects of Selected Pesticide Coformulants

Appendices 1-18 to: Report on the Health Effects of Selected Pesticide Coformulants

102 Evaluation

Based upon evaluation of radioactivity excreted in urine and faeces in rats following oral administration of the acetate (¹⁴C-DEGBEA) of DEGBE or dermal contact to ¹⁴C-DEGBE or ¹⁴C-DEGBEA, the absorption is about 85% following oral administration, and about 30-50% at low dose levels (200 mg/kg b.w.) and about 3-18% at high dose levels (2000 mg/kg b.w.) following dermal application. Only minor amounts (a few percent) are excreted in faeces and about 5% as carbon dioxide. Following dermal application, female rats tended to excrete a larger proportion of the applied dose of DEGBE than did male rat. The major urinary metabolite was 2-(2-butoxyethoxy)acetic acid at both exposure routes. No evidence was found for excretion of 2-butoxyacetic acid (BAA) following oral administration of DEGBEA (a single dose of 200 or 2000 mg/kg b.w.), whereas trace levels of BAA were present in urine following dermal application of DEGBE (200 or 2000 mg/kg b.w. under occlusion for 24 hours), but not DEGBEA (2000 mg/kg b.w. under occlusion for 24 hours).

DEGBE is of low acute toxicity following oral administration and dermal application in experimental animals with oral LD₅₀-values ranging from 2000 to 9600 mg/kg b.w. (rats, mice, rabbits, and guinea pigs) and dermal LD₅₀-values greater than 2000 mg/kg b.w. (rats and rabbits). The limited data on acute toxicity following inhalation of DEGBE in experimental animals do not allow an evaluation of this end-point; however, an LC₅₀-value of about 73000 mg/m³ for rats following exposure to the acetate of DEGBE indicate a low order of acute inhalation toxicity for DEGBE as well. No human data have been found.

Overall, DEGBE is considered to be of low acute toxicity in humans.

A few human case reports of irritation (skin, eyes, and upper respiratory tract) and sensitisation to DEGBE have been reported. In rabbits and guinea pigs, DEGBE has shown a very low skin irritating potential in conventional tests for skin irritation whereas it is a moderate eye irritant in rabbits. DEGBE was not sensitising in the guinea pig maximisation test.

A 13-week dermal study in rats has revealed skin irritation, which was concentration dependent in incidence, severity, and time of onset. In contrast to this study, skin effects (scab formation) were only noted in 5/12 females in another 13-week study at the highest concentration used. No treatment-related effects on the skin were noted in rabbits in a 4-week dermal study; however, the concentration used was low compared to the concentrations used in the two dermal studies in rats. In a dermal teratogenicity study (OECD-guideline 414) in rabbits, skin irritation was observed after about 1 week of treatment and persisted until the dams were sacrificed. The NOAEL for skin irritation is considered to be below 200 mg/kg b.w./day based on the skin irritative effects observed in the first 13-week dermal study in rats although skin irritation was not observed in the other 13-week dermal study in rats at dose levels up to 600 mg/kg b.w./day; according to IUCLID, the second 13-week study cannot by used to conclude a NOAEL for local effects. Furthermore, the NOAEL is considered to be above 100 mg/kg b.w./day based on the dermal teratogenicity study in rabbits in which a NOAEL and a LOAEL of 100 and 300 mg/kg b.w./day, respectively, was observed for skin irritation.

Overall, DEGBE is considered to be a skin and eye irritant and to have the potential of causing respiratory irritation in humans. As the guinea pig maximisation test was negative, DEGBE is not considered to have a skin sensitising potential although a few human cases have been reported.

No data on repeated dose toxicity in humans following inhalation of DEGBE have been found.

A two-week inhalation study in rats has revealed a dose-related decrease in spleen weight in males and effects indicative of local lung effects (perivascular and peribronchial accumulations of granulocytes and activation of alveolar epithelium) at exposure levels from 100 mg/m³; increased (but not dose-related) lung weights were observed from 350 mg/m³. Similarly, another 2-week inhalation study performed according to OECD Guideline 412 (but only with female rats and only one exposure concentration: 350 mg/m³) also revealed effects indicative of local lung effects whereas no effects were noted on organ weights. These types of effects were, however, not reported in a 5-week or in a 13-week inhalation study in rats. In the 5-week study, only effects on the liver were reported (dose-related decreased relative liver weight in males from 40 mg/m³, dose-related increase in relative liver weight in females from 40 mg/m³ (significant only at 122 mg/m³), and slight paleness of the liver (at 122 mg/m³) and slight hepatocyte vacuolisation at all dose levels); based on this study, a NOAEL of 13 mg/m³ for liver effects can be considered. However, in the 13-week study (OECD Guideline 413), the only observed effect was a dose-related decreased level of serum aspartate aminotransferase in males of all exposure groups (13, 40, or 95 mg/m³), an effect, which is not considered as being toxicologically relevant because, according to IUCLID (2000), no effects on the liver were observed and because the change was within the range of biological variation.

Overall, a NOAEL of 95 mg/m³ is established for the various effects, both systemic as well as local effects in the lungs, observed in rats following exposure by inhalation to DEGBE.

No data on repeated dose toxicity in humans following oral intake of DEGBE have been found.

Regarding repeated dose toxicity following oral administration in experimental animals, two gavage studies in rats are available. However, the results of these studies have not been cited similarly in the different sources used in this evaluation and, as the results of the studies have not been published, it is impossible to evaluate the results. But, based on the results as they have been cited in the sources used in this evaluation (predominantly IUCLID 2000 but also DECOS 1996), DEGBE appears to induce changes in haematological parameters indicative of a haemolytic effect following oral gavage to rats at dose levels from 1782 mg/kg b.w./day for 6 weeks (only male rats were included in this study) or at dose levels (in females) from about 50 mg/kg b.w./day for 13 weeks. Haematological changes (increase in total red cells and haemoglobin content at the mid-dose level) were, according to DECOS (1996), also observed in male rats in the 13-week study; however, these changes are opposite to those seen in female rats and cannot be interpreted based on the data available. Furthermore, increased spleen weights (absolute and relative) were observed at dose levels from 1782 mg/kg b.w./day in the 6 week-study whereas the relative spleen weight was, according to DECOS, decreased in male animals at 327 mg/kg b.w./day in the 13-week study. Effects on the liver have also been reported consisting of decreased liver weight at dose levels from 1782 mg/kg b.w./day in the 6 week-study, but increased liver weights (absolute and relative) in male animals at 327 mg/kg b.w./day in the 13-week study. The contradictory results reported in the 6-week and 13-week oral gavage studies cannot be explained based on the data available. Hyperkeratosis in the stomach was observed in all dosed rats (from 891 mg/kg b.w./day) in the 6-week study; this effect was not reported in the 13-week study.

Overall, a NOAEL for effects of DEGBE following oral administration cannot be considered based on the citations of the two oral gavage studies in the sources used in this evaluation. According to Gingell et al. (1996), NOAEL of about 300 mg/kg b.w./day can be justified based upon these two studies.

No data on systemic toxicity in humans following repeated dermal application of DEGBE have been found.

The systemic toxicity of DEGBE following dermal application has been studied in rats and rabbits. A 13-week study in rats revealed no adverse systemic effects at dose levels up to 2000 mg/kg b.w./day. Similarly, no systemic effects, including neurotoxicity, were noted in another 13-week study in rats at dose levels up to 2000 mg/kg b.w./day. In rabbits, haematological changes (decreased eosinophil and monocyte count in males; decreased haemoglobin, erythrocyte, leukocyte and neutrophil count in females) were observed in a 4-week dermal study at a dose level of 30 mg/kg b.w./day (the only dose level in the study); however, these effects were, according to IUCLID (2000), not considered treatment-related because of a wide variation within one group and/or between the groups before and after exposure.

Overall, a NOAEL for systemic effects, including neurotoxicity, of 2000 mg/kg b.w./day following dermal application of DEGBE is considered based on the two 13-week dermal studies in rats because of the limitations in the dermal rabbit study.

No data on toxicity to reproduction in humans following exposure to DEGBE have been found.

No indications of reproductive and developmental effects were observed in rats in two one-generation studies at dose levels of up to 1000 mg/kg b.w./day (oral study) and 2000 mg/kg b.w./day (dermal study); in the oral study, post-natal effects (decreased weight of pups at day 14 of lactation) were observed in offspring from females administered 1000 mg/kg b.w./day and mated with untreated males whereas no post-natal effects were noted in the dermal study.

Overall, a NOAEL of 1000 mg/kg b.w./day can be considered for reproductive and developmental effects, and of 500 mg/kg b.w./day for post-natal effects following oral administration of DEGBE. Following dermal application, a NOAEL of 2000 mg/kg b.w./day can be considered for reproductive, developmental and post-natal effects.

No data on developmental toxicity, including teratogenicity, in humans following exposure to DEGBE have been found.

Developmental toxicity studies have been performed in rats (oral), mice (oral), and rabbits (dermal, OECD-guideline 414). No developmental effects, including teratogenicity, were observed in rats (dietary dose levels of up to 633 mg/kg b.w./day, day 0 to 20 of gestation) or in rabbits (dermal application of dose levels of up to 1000 mg/kg b.w./day, day 7 to 18 of gestation). In mice, no developmental effects were observed at a dose level of 2050 mg/kg b.w./day (gavage, day 7 to 14 of gestation); according to IUCLID, examinations of pups for malformations were not performed. Maternal effects were observed in rats (reduced body weight gain from 25 mg/kg b.w./day), in mice (mortality (25%) at 2050 mg/kg b.w./day), and in rabbits (reduced body weight gain and skin irritation from 300 mg/kg b.w./day).

Overall, NOAELs for developmental toxicity, including teratogenicity of 633, 2050, and 1000 mg/kg b.w./day can be considered for the rat (oral), mouse (oral, developmental only), and rabbit (dermal), respectively. For maternal effects, NOAELs of 500 and 100 mg/kg b.w./day can be considered for mice and rabbits, respectively; in rats, the NOAEL for maternal effects is below 25 mg/kg b.w./day.

The data on mutagenicity and genotoxicity indicate that DEGBE is not a mutagenic or genotoxic substance neither in vitro nor in vivo; no data on mutagenic and genotoxic effects in humans have been found.

No data on carcinogenic effects in humans or experimental animals have been found.

102.1.1 Conclusion

The critical effects following exposure to DEGBE are the irritative effects on the skin and eyes and the haemolytic effect observed in studies in experimental animals.

Only a slight skin irritation has been observed in conventional tests for skin irritation; however, skin irritation, which was concentration dependent in incidence, severity, and time of onset was observed in a repeated dermal toxicity study in rats as well as in a teratogenicity study in rabbits. Based upon these two studies, the NOAEL for skin irritation following repeated dermal application of DEGBE is considered to be between 100 and 200 mg/kg b.w./day. DEGBE is a moderate eye irritant in rabbits and is classified for eye irritative properties according to the EU classification criteria.

A few case reports in humans support the skin and eye irritative potential of DEGBE and also suggest that DEGBE has the potential of causing respiratory irritation in humans.

DEGBE appears to induce changes in haematological parameters indicative of a haemolytic effect following oral gavage to rats at dose levels from 1782 mg/kg b.w./day for 6 weeks (only male rats were included in this study) or at dose levels (in females, but not males) from about 50 mg/kg b.w./day for 13 weeks. No changes in haematological parameters have been reported in repeated dose toxicity studies on inhalation and dermal exposure or in the reproductive and developmental toxicity studies using oral or dermal administration routes. As mentioned above, the validity of the results of the two oral gavage studies cannot be evaluated as the study reports are not public available and the citations in the sources used in this evaluation are not consistent.

The mechanism(s) behind the haemolytic effect is not fully understood, but the metabolite 2-butoxyacetic acid (BAA) has shown a significantly greater haemolytic effect in vitro than EGBE whereas DEGBE has shown a considerably less haemolytic activity than EGBE. (ECETOC 1995).

BAA is a possible metabolite of DEGBE and trace levels were present in the urine of rats following dermal application of DEGBE (200 or 2000 mg/kg b.w. under occlusion for 24 hours), but not following oral administration of the acetate (DEGBEA) of DEGBE (a single dose of 200 or 2000 mg/kg b.w.)

Overall, DEGBE is considered to have the potential of inducing haemolysis in humans, but probably only at high dose levels and following repeated exposure.