PROPINEB First draft prepared by M. Watson Pesticide Safety Directorate, Ministry of Agriculture, Fisheries and Food Harpenden, Hertfordshire, United Kingdom EXPLANATION Propineb was first evaluated by the Joint Meeting in 1977, when a temporary ADI of 0-0.005 mg/kg bw was established (Annex I, reference 28). The temporary ADI was extended in 1980 and 1983 (Annex I, references 34 and 40). At the 1985 Joint Meeting (Annex I, reference 44), the temporary ADI was not extended in view of the carcinogenic response in the liver of mice to propylene thiourea (PTU) and the lack of NOAELs for thyroid effects of propineb and PTU. This monograph summarizes new or not previously reviewed data on propineb, as well as relevant data from previous monographs and monograph addenda on this pesticide. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOLOGICAL DATA Biochemical aspects Absorption, distribution and excretion In male Sprague-Dawley rats, dosed orally with 5 or 50 mg 14C- propineb/kg bw, 60-70% of the radioactivity was absorbed in 48 hours. About 50% of the activity was excreted via urine and 40% via faeces within this period. Exhalation during the first 24 hours after administration amounted to 7% and excretion in the bile to 3% of the administered dose (Ecker, 1975; Weber, 1980). Peak levels in blood and most organs were reached 3-5 hours after administration, whereas in the thyroid the maximum concentration was attained after 24 hours. Within 4 days the total elimination exceeded 99%. The half-life of elimination from the tissues (except the thyroid) was first rapid, than slower, varying between 5 and 20 days. Four days post-dosing (50 mg/kg bw), the concentration of radioactive material in the thyroid was about 100 times and in the kidney and pituitary 3-4 times higher than the average concentration for all other organs except the gastrointestinal tract. After 16 days the relative concentration factor for the thyroid was about 30 (Patschke & Wegner, 1975). Biotransformation The main metabolites found in the urine of dosed rats were propylene diamine (accounting for 12-15% of the renally excreted activity), PTU and propylene urea (PU) (accounting together for 40- 45%). A minor metabolite was 4-methylimidazoline (less than 5%). No compounds could be considered as potential intermediates for complete degradation to CO2 (Ecker, 1975). The metabolic pathway of propineb in rats is illustrated in Figure 1. Toxicological studies Acute toxicity studies Technical grade propineb of 84-87% purity was tested in the acute toxicity studies summarised in Table 1. WHO has classified propineb as unlikely to present acute hazard in normal use (WHO, 1992).Table 1. Acute toxicity of propineb Species Sex Route LD50 LC50 Reference (mg/kg bw) (mg/m3) Mouse M/F oral > 5000 Thyssen & Kimmerle, 1978 Mouse M/F s.c. 1500-2000 Thyssen & Kimmerle, 1978 Mouse M inhalation > 391 (1 x 4 h) Thyssen & Kimmerle, 1978 Rat M/F oral > 5000 Thyssen & Kimmerle, 1978 Rat F oral 5900 Flucke & Kimmerle, 1977 Rat M/F dermal > 5000 Thyssen & Kimmerle, 1978 Rat M/F i.p. 102-141 Thyssen & Kimmerle, 1978 Rat M/F inhalation > 522 (1 x 1 h) Thyssen & Kimmerle, 1978 Rat M/F inhalation > 693 (1 x 4 h) Thyssen & Kimmerle, 1978 Rat M/F inhalation > 193 (5 x 4 h) Thyssen & Kimmerle, 1978 Hamster M inhalation > 391 (1 x 4 h) Thyssen & Kimmerle, 1978 Cat M oral > 500 Thyssen & Kimmerle, 1978 Sheep M/F oral 2500 Hoffmann, 1983 Short-term toxicity studies Rats Groups of 50 male and 50 female Wistar rats received diets containing propineb (technical material, 93.5% purity) at concentrations of 0, 100 or 500 ppm. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. Half of the rats from each group were sacrificed after 6 months, the remainder were sacrificed after a subsequent withdrawal period of 8 weeks. Treatment with 100 ppm did not cause thyroid enlargement in either sex, whereas treatment with 500 ppm caused marked thyroid enlargement in both males and females. During the 8-week withdrawal period the enlargement receded in male rats, but relative thyroid weights were still higher than control values in females, indicating a tendency to reversibility (Loeser, 1968). In a 3-month feeding study in Wistar rats, groups of 15 males and 15 females received dietary levels of 0, 5, 10, 25, 50 or 100 ppm propineb (87% purity). The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. There was no treatment-related effect on behaviour, survival, food intake or weight gain. Haematological and urinalysis investigations revealed no indication of any reaction to treatment. Clinical chemistry investigations revealed increased sorbitol dehydrogenase activity in serum in male rats treated with 50 or 100 ppm and increased serum lactate dehydrogenase activity in males and females treated with 100 ppm. Gross pathology and organ weight analysis revealed no indication of any reaction to treatment. No histopathological examination of tissues was performed and it was thus considered inappropriate to derive an NOAEL from the results of this study (Loeser, 1969). Groups of 10 male and 10 female Wistar TNO/W74 rats were exposed to propineb aerosols at analytically-determined concentrations of 0, 5, 8, 29, or 44 mg/m3, five times per week for 6 hours, for 3 weeks. Rats exposed to 44 mg/m3 exhibited severely disturbed behaviour including paralysis of the extremities. All the female rats and 1 male rat at this exposure level died by the 13th exposure. Animals that died had sharp losses in body weight and were cachectic. Gross necropsies revealed small spleens and livers, enlarged adrenals, and inflamed lungs. Histopathology revealed acute vasculature congestion in the lungs, liver, kidneys, and bronchial lymph nodes, indicating that the cause of death was cardiovascular failure. One male rat at 29 mg/m3 also exhibited hind limb paralysis but survived to the end of the study. The remaining test animals did not differ from control animals with respect to appearance, behaviour or body-weight gains. Haematological examinations, clinical chemistry, and urinalyses (performed just prior to termination), and results of gross necropsies, organ weight determinations, and histopathological examinations revealed no indication of any reaction to treatment in animals surviving to termination (Thyssen & Mohr, 1979). In a study to compare the effects of propineb with various other thyro-suppressive agents, groups of 50 male and 50 female Wistar rats were treated orally with 50 mg/kg bw/day of the following compounds: pure propineb, two technical samples of propineb, PTU, ETU, zineb or methyl thiouracil as a positive control. An untreated control was also included and 10 male and 10 female rats were killed after 7, 14 or 21 days treatment and after 14 or 28 days recovery. Investigations of thyroid activity was limited to recording of thyroid weight, no biochemical analyses or histopathology were performed. PTU, ETU and methyl thiouracil caused significant increases in absolute and relative thyroid weight in rats of both sexes, while the three propineb samples caused an increase in the relative weight in females only. The thyroid enlargement induced by propineb was reversible during the withdrawal period, the effect of the other agents was partially reversible. Propineb had only a moderate effect compared to methyl thiouracil, whereas PTU had an equivalent effect to that of methyl thiouracil and was somewhat stronger than ETU (Kimmerle, 1972). Propineb of unknown purity was administered in the feed for 62 days to 5 groups of 80 male Wistar TNO/W74 rats at dosage levels of 0, 2, 10, 50, or 250 ppm. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. Ten rats per group were killed for interim sacrifice at 7 days or at 21 days. An additional 10 rats per group were also sacrificed at 7, 21, or 62 days for "thyroid function tests", which was reported separately (see Weber & Dressler, 1980). The remaining animals were sacrificed at 62 days. No mortalities occurred during the study and daily examinations indicated no effects that could be attributed to the test material. Mean body weights of animals in the 250 ppm group were slightly but consistently lower than those of the control group throughout the entire study, but food consumption was unaffected. Total thyroxin was decreased in the 50 and 250 ppm groups at 21 and 62 days. Thyroid weights were decreased in the 250 ppm group at 7 days, but later increased in the 50 and 250 ppm groups at 62 days. Histopathology did not reveal any treatment-related changes in the thyroid. Organ weight analysis and histopathological examinations of liver and adrenals revealed no effects that could be attributed to the test material. The NOAEL in this study was 10 ppm (equal to 0.74 mg/kg bw/day), based on changes in thyroxin concentration and increased thyroid weight at 50 and 250 ppm (Kroetlinger et al., 1980). Ten male rats per group from the above-described study were used for "thyroid function tests" at 7, 21, or 62 days. In addition, iodine accumulation in the thyroid was assayed 24 hours after oral intubation of 0.2 µCi of 131I-NaI tracer by measuring radioactivity in excised and weighed thyroid tissue. Concentrations of T3 and T4 in the serum were also determined by use of a commercially-available 125I radioimmunoassay test system. Mean thyroid weights were increased above control values in the 50 ppm group at 62 days, and in the 250 ppm group at 21 days and at 62 days. A decrease in mean thyroid weights was observed in the 2 ppm group at 7 days. Mean iodine accumulation in the thyroid, expressed as the amount of radioactive iodine per mg of tissue, was decreased below control values in the 50 ppm group at 62 days and in the 250 ppm group at 21 and 62 days. Mean T3 concentrations were increased above control values in the 2 ppm group and in the 10 ppm group at 7 days. A decrease in mean T3 was observed in the 250 ppm group at 62 days. Mean T4 concentrations were decreased below control values in the 250 ppm group at 7, 21 and 62 days. The study results indicate that propineb affects thyroid function at all dosage levels tested. The effect appears to be dose-related. At 50 ppm and 250 ppm, iodine accumulation in the thyroid was reduced and at 250 ppm, T3 and T4 serum levels were also reduced. A compensatory reaction occurred, however, at these dosage levels, as evidenced by increased thyroid weights and a return toward control values for several of the other parameters. At 2 and 10 ppm, an effect on thyroid function was indicated by the increased levels at 7 days of T3, the more biologically-active form of the thyroid hormone. However, this is considered to be a normal physiological response, without lasting adverse effect. The NOAEL in this study was thus 10 ppm, equal to 0.74 mg/kg bw/day (Weber & Dressler, 1980). The effect of propineb on thyroid function was investigated in a 63-day feeding study in Wistar rats. Groups of 36 males received dietary concentrations of 0, 0.2, 0.6, 2 or 10 ppm propineb. Technical material of 83.3% purity was used, but dietary levels refer to pure active ingredient. The homogeneity, stability and accuracy of admixture of the test material into the test diet was checked during the study and found to be adequate. On days 7, 21 and 63 thyroid function was investigated by determination of thyroid weight, measurement of 131I incorporation into the thyroid and by radio immunoassay determination of T3, T4 and TSH in the serum. Food and water intake was not affected by treatment, but body-weight gain was slightly depressed at 2 and 10 ppm in comparison with controls. Thyroid weights were unaffected by treatment at any of the examinations. Although minor inter-group differences in results of other investigations attained a level of statistical significance when compared with controls, there were no consistent, dose-related effects. Histopathological examination of thyroids was conducted later and this revealed a minimal to slight hypertrophy in the follicular epithelium of 2 of 10 rats treated with 10 ppm for 63 days. No similar changes were seen at the same dose level after shorter treatment periods or at lower doses at any of the treatment periods. The NOAEL in this study was 10 ppm since the minor histological changes seen in thyroid at 10 ppm were not considered to be a permanent adverse effect in rats. The apparent changes in body-weight gain were disregarded, since this effect was not supported by results of any other feeding study with propineb in rats, and there were large inter-group differences in initial body weight in this study, which hampered interpretation of the weight gain data (Weber et al., 1991). Rabbits Technical grade propineb of 87.3% purity was dermally applied to the shaven backs of groups of 6/sex New Zeeland white rabbits (one half of which had intact and one half abraded skin test sites), 5 times per week for 7 hours for 3 weeks at dosage levels of 0, 50, or 250 mg/kg bw/day. Three male rabbits died during the study of severe pneumonitis. Daily observations, including skin reactions, revealed no effects attributable to the test material. No differences in body weights between control and test animals were observed. All clinical laboratory tests, gross necropsies and histopathological examinations revealed no indication of any reaction to treatment with propineb. With the exception of slightly increased liver weights in female rabbits treated with 250 mg/kg bw/day, organ weights in control and test animals were similar (Mihail & Kaliner, 1979). Dogs In a 4-month feeding study, groups of beagle dogs (2/sex) received dietary concentrations of 0, 100, 400 or 1600 ppm propineb (86% purity). The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. The results of this study revealed no indication of any reaction to treatment in terms of survival, behaviour, food intake, weight gain, clinical laboratory investigations, gross pathology and organ weight analysis. No histopathological examination of tissues was carried out and it is thus considered inappropriate to derive an NOAEL from the results of this study (Loeser, 1967). In a 2-year feeding study, groups of 4 male and 4 female beagle dogs received dietary concentrations of 0, 100, 300, 1000 or 3000 ppm propineb (purity approximately 86%). The summarized results of this study revealed no indication of any reaction to treatment in terms of survival, behaviour, food intake, weight gain, clinical laboratory investigations, gross pathology, organ weight analysis or histopathology. The NOAEL for this study may therefore be defined as 3000 ppm (equivalent to 75 mg/kg bw/day), the highest dose level tested. A complete detailed report of this study was not available for evaluation (Loser, 1973a). Long-term toxicity/carcinogenicity studies Mice Propineb of 82.9% purity was administered in the feed to groups of NMRI mice (50/sex) for 104 weeks at dietary levels of 0, 50, 200, or 800 ppm. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. No substantial differences in mortality were observed between male and female control and test groups, although the best survival of any group was seen in the high-dose males. Clinical observations did not indicate any differences between test and control mice and food consumption and body-weight gain was similar in male and female control and test groups. Haematological, clinical chemistry, and urinalysis examinations did not reveal any effects attributable to the test material. Gross necropsies were reported to be negative for lesions attributable to the test material. Organ weight analysis did not reveal any differences that could be related to the test material. Non-neoplastic lesions were not reported in the histopathological evaluation. Percentages of female mice with tumours of any kind were 65, 66, 73, and 88% for the control, low-, mid-, and high-dose groups, respectively. A similar increase was not observed in treated male mice. Frequently- observed neoplasms were those commonly seen in NMRI mice and consisted of pulmonary adenomas and malignant lymphomas in male and female mice and benign granulosa cell tumours in the ovaries of female mice. Thyroid or adrenal tumours were not increased in treated male or female mice. An increased incidence of hepatocellular adenomas was observed in the high-dose male group. Percentages were 6, 7, 0, and 20 for the control, low, mid-, and high-dose male groups, respectively. Hepatocellular carcinomas in male mice ranged from 0 to 4%, but their incidence was not dose- related. Historical control data presented by the testing laboratory for hepatocellular adenomas in NMRI mice ranged from 4 to 12%. The increase in hepatocellular adenomas in the high-dose male group may possibly be related to treatment with the test material, but may have been affected by the higher survival rate in this group compared to the controls. Hepatocellular tumours were not increased in treated female mice. The NOAEL in this study was 200 ppm (equal to 26 mg/kg bw/day), based on the equivocal alteration in hepatic tumour incidence at 800 ppm (Brune et al., 1980). Rats Groups of Wistar rats (25/sex/dose and 50/sex/control group) were fed diets containing propineb (technical material, 93.5% purity) at dietary levels of 0, 1, 10, 100, 1000, 2000 or 8000 ppm for 2 years. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. The mortality rate was increased in comparison with controls at 1000 ppm and above, such that at 2000 and 8000 ppm in females and at 8000 ppm in males, no rats survived to termination. Dose-related reduced weight gain and food intake were also evident at 1000, 2000 and 8000 ppm. Apparent muscular weakness, leading to paralysis (described as myasthenia) was seen in rats receiving 1000, 2000 or 8000 ppm. The results of limited clinical chemistry investigations (conducted at 16 and 24 months) did not reveal any indication of reaction to treatment. At autopsy, increased kidney, liver and thyroid weights were noted at 100 ppm and above. Histopathology revealed no changes in kidney and liver, but did show evidence of degeneration of skeletal muscle at 1000 ppm and above, along with an increased incidence of TSH-related thyroid tumours in these groups. The NOAEL in this study was thus 10 ppm (equivalent to 0.5 mg/kg bw/day) based on the organ weight changes noted at 100 ppm and above (Loeser, 1974a). In a second study, carried out in order to more closely define the NOAEL in long-term administration to rats, groups of 40 male and 40 female Wistar rats (95/sex in the control group) were fed diets containing propineb (93.5% purity) at dietary levels of 0, 5, 10, 25, 50 or 100 ppm for 2 years. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. There were no clinical signs of reaction to treatment and no effects on food consumption, growth rate or mortality at any dose level. Limited clinical chemistry analyses revealed that serum ALT and AST activities were slightly higher than control values after 52 weeks in rats receiving 100 ppm, but no similar effect was seen at termination. Serum PBI levels were lower than control values, at 52 weeks and prior to termination, in rats receiving 100 ppm. At autopsy there were no macroscopic abnormalities attributable to treatment and organ weight analysis revealed no significant intergroup differences. Histopathology revealed no changes considered to be related to the administration of propineb, in particular, the nature, location and frequency of tumours provided no indication of any carcinogenic effect. The NOAEL was 50 ppm, equivalent to 2.5 mg/kg bw/day, in this study (Loeser, 1974b). Reproduction studies In a 3-generation study in rats, with two litters per generation, groups of 10 male and 20 female Long Evans rats received propineb (93.5% purity) at dietary levels of 0, 20, 60, 200 or 600 ppm. The homogeneity, stability and accuracy of admixture of the test material into the test diet was not checked during the study. Treatment with 200 ppm led to slight symptoms of hind limb paralysis in parental animals, while treatment with 600 ppm led to increased mortality, decreased weight gain and severe hind limb paralysis. With regard to the reproductive parameters, treatment with 200 ppm was associated with slightly lower gestation rates and a lower number of pups per litter after one mating, while treatment with 600 ppm was associated with substantially lower gestation rates (up to 50%) after nearly all matings and lower birth weight and lower numbers of pups per litter after some matings. Lactation performance of dams receiving 600 ppm which did have offspring was not, however, adversely affected. The NOAEL was 60 ppm (equivalent to 3 mg/kg bw/day) (Loeser, 1973b). Special studies on embryo/fetotoxicity Rats Groups of 17-23 mated female rats were given propineb by oral gavage at levels of 0, 3, 10, 30 or 100 mg/kg bw/day on days 6 to 15 of gestation. Treatment with 30 mg/kg bw/day was associated with slight maternal toxicity (somnolence, ruffled coat, limpness), while treatment with 100 mg/kg bw/day led to severe maternal toxicity (paralysis of extremities, ataxia, dyspnoea, tremors), leading to mortality in some cases. At this high dose, fetal growth was depressed, and teratogenic effects (dysplasia of extremities) were also seen. The NOAELs were 10 and 30 mg/kg bw/day for maternal and embryo/fetotoxicity, respectively (Machemer, 1974a). These results were supported by studies published in the literature; in one study, doses greater than 400 mg/kg bw/day caused abnormalities and maternal toxicity when given to rats on day 11 of gestation and in another study, using doses of 0, 25, 50 100 or 200 mg/kg bw/day on days 6 to 16 of gestation, abnormalities and maternal toxicity were observed at 100 and 200 mg/kg bw/day (Larsson et al., 1976; Vicari et al., 1985). Rabbits Groups of 16 mated female rabbits were given propineb (83.9% purity), by oral gavage, at dose levels of 0, 10, 30 or 100 mg/kg bw/day from day 6 to day 18 of gestation. Signs of severe maternal toxicity were seen at 100 mg/kg bw/day, including reduced weight gain and food intake in comparison with controls, dyspnea and ventro-lateral recumbency, and signs of abortion in two females. Body-weight gain and food intake were also reduced at 30 mg/kg bw/day. Evaluation of reproduction parameters revealed a dose-related increased post-implantation loss at 30 and 100 mg/kg bw/day. Fetal parameters, including external, skeletal and visceral examinations, revealed no effects associated with treatment with propineb. The NOAEL for maternal toxicity was 10 mg/kg bw/day, while there was no indication of embryo/fetotoxicity or teratogenicity at 100 mg/kg bw/day, the highest dose tested (Becker et al., 1988). Special studies on genotoxicity Results of genotoxicity tests on propineb are summarized in Table 2. The Meeting concluded that propineb was not genotoxic. Special studies on sensitization Propineb (83.9% purity) was tested for possible skin sensitizing potential in guinea-pigs in a Magnusson and Kligman maximization test, employing a test group of 20 animals and two Table 2. Results of genotoxicity assays on propineb Test system Test object Concentration Purity Results Reference Ames test S. typhimurium up to 2.5 mg/ 84.3% Negative Herbold, 1980a TA98, TA100, TA1535, plate TA1537 Ames test S. typhimurium up to 0.864 ? Negative Hatano Institute, 1978 TA98, TA100, TA1535, mg/plate TA1537, TA1538 E. coli WP2 Preferential B. subtilis M45, H17 up to 0.864 ? Negative Hatano Institute, 1978 toxicity mg/plate HGPRT forward CHO cells 0.11-60 mg/ml ? Negative Lehn, 1988 mutation assay UDS Rat hepatocytes 5-30 mg/ml ? Negative Cifone, 1987 Micronucleus test Mouse 2 x 1000 or 2 x 85.7% Negative Herbold, 1982 2000 mg/kg bw Micronucleus test Mouse not known ? Negative Rolandi et al., 1984 Dominant lethal NMRI mice 500 mg/kg bw ? Negative Machemer, 1974b control groups of 10 animals each. Following intradermal induction with 0.1% propineb and topical induction with 25% propineb, the first challenge was carried out using 25% propineb. A positive response was seen in all 20 test animals, against no positive reactions in the first control group. A second challenge was carried out using 2.5% propineb. Positive reactions were seen on this occasion in 18 test animals against 4 in the control group. This study therefore detected clear indications of the allergic potential of propineb in guinea-pigs (Heimann, 1987). In a further experiment, propineb (premix, 83.3% purity) was tested for possible skin sensitizing potential in guinea-pigs in a Buhler patch test employing a test group and two control groups of 12 animals each. Following epicutaneous induction with 50% propineb, challenge was carried out with 2.5% and 50% propineb. The test material was tolerated without reaction and this study revealed no indication of a skin sensitizing potential of propineb in guinea- pigs (Flucke, 1989). Irritant and/or allergizing characteristics of propineb in humans was not confirmed. Between 1964 (when production began) and 1988 no allergies or skin sensitizing reactions associated with propineb were recorded, "even though skin contact had been frequent as a result of cleaning work" (Mueller, 1988). Observations in humans No information available. COMMENTS Orally administered propineb in rats is rapidly absorbed and excreted largely via urine and faeces. Although there was some evidence of excretion by exhalation, the available metabolic data (which detected PTU and propyleneurea as the main urinary metabolites along with propylenediamine and a small amount of 4- methylimidazoline) found no metabolites which could be considered as potential intermediates for degradation to CO2. Study results indicated that a proportion of the administered dose accumulates temporarily in the thyroid. Although most elimination occurred within 4 days of dosing, the half-life of elimination for the proportion remaining was relatively long. This could be due to incorporation of portion of the molecule into endogenous substances following metabolism, which would also account for the radioactivity eliminated with exhaled air. Propineb has moderate to low acute toxicity in mice, rats, hamsters, cats and sheep. WHO has classified propineb as unlikely to present acute hazard in normal use. The results of toxicity studies clearly indicate that propineb has a goitrogenic effect in rats, although no similar finding was noted in rabbits or dogs. In a 62-day study in male rats using dietary levels of 0, 2, 10, 50 or 250 ppm, the NOAEL was 10 ppm (equal to 0.74 mg/kg bw/day), based on changes in thyroxine concentration and increased thyroid weight at higher doses. Although in a later 63-day study using dietary levels of 0, 0.2, 0.6, 2 or 10 ppm slight hyperplasia was seen in the thyroid in 2 rats out of 10 treated with 10 ppm, this finding was considered not to be a permanent adverse effect in rats. In a comparative study in rats of the effects of propineb, PTU, ETU, zineb and methyl thiouracil on thyroid weight, propineb had only a moderate effect compared to methyl thiouracil, whereas PTU had an equivalent effect to that of methyl thiouracil and was somewhat stronger than ETU. These results suggest that the effects of propineb on the thyroid in rats may be caused primarily by the metabolite, PTU. Dogs tolerated much higher doses of propineb, dietary administration of 3000 ppm, equivalent to 75 mg/kg bw/day, causing no adverse effects over 2 years. In long-term studies, treatment-related alterations in tumour incidence were seen in rats and mice. In mice treated with 0, 50, 200 or 800 ppm, an increase in hepatocellular adenomas was seen in males only, at the highest dose tested, but there was no increase in the incidence of hepatic carcinomas and no similar effect in females. The NOAEL was 200 ppm, equal to 26 mg/kg bw/day, based on this change in hepatic tumour incidence. In rats, there were two studies, using dietary levels of 0, 1, 10, 100, 1000, 2000 or 8000 ppm in the first and 0, 5, 10, 25, 50 or 100 ppm in the second. The overall NOAEL was 50 ppm, equivalent to 2.5 mg/kg bw/day, based on increased kidney and liver weight (without histological correlation) and increased thyroid weight at 100 ppm and above. An increase in thyrotropin-related thyroid tumours and skeletal muscle degeneration was seen in rats at dietary levels of 1000 ppm and greater, but these doses were accompanied by increased mortality. In a three-generation reproduction study in rats using dietary levels of 0, 20, 60, 200 or 600 ppm the NOAEL was 60 ppm, equivalent to 3 mg/kg bw/day, with adverse effects on maternal health and impaired reproductive performance seen at higher doses. Teratogenicity studies indicated that propineb has teratogenic potential in rats, but no evidence of teratogenicity was seen, even in the presence of maternal toxicity, in rabbits. In rats, using dose levels of 0, 3, 10, 30 or 100 mg/kg bw/day, the NOAELs were 10 and 30 mg/kg bw/day for maternal and embryo/fetotoxicity, respectively, with evidence of teratogenicity at 100 mg/kg bw/day. In rabbits, using dose levels of 0, 10, 30 or 100 mg/kg bw/day, the NOAEL for maternal toxicity was 10 mg/kg bw/day, while there was no evidence of teratogenicity or embryo/fetotoxicity at 100 mg/kg bw/day, the highest dose tested. Propineb has been adequately tested in a series of genotoxicity assays from which the Meeting concluded that it is not genotoxic. An ADI was allocated to propineb, which was based on the NOAEL from the short-term thyroid function study in rats (10 ppm, equal to 0.74 mg/kg bw/day) using a safety factor of 100. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Mouse: 200 ppm in the diet, equal to 26 mg/kg bw/day (2-year study) Rat: 10 ppm in the diet, equal to 0.74 mg/kg bw/day (62-day thyroid function study) 50 ppm, equivalent to 2.5 mg/kg bw/day (2-year study) Dog: 3000 ppm in the diet, equivalent to 75 mg/kg bw/day (2-year study). Estimate of acceptable daily intake for humans 0-0.007 mg/kg bw Studies which will provide information valuable in the continued evaluation of the compound Observations in humans. REFERENCES Becker, H., Vogel, W. & Terrier, Ch. (1988) Embryotoxicity (including teratogenicity) study with LH 30/Z in the rabbit. Report R 4460, Research and Consulting Company AG, Itingen, Switzerland. Unpublished report submitted to WHO by Bayer AG. Brune, H., Deutsch-Wenzel, R., & Mohr, U. (1980) Toxicology examination of propineb in a chronic feeding study on NMRI mice. Biological laboratory of Dr. Brune (Hamburg), Report No. R 1792. 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See Also: Toxicological Abbreviations Propineb (Pesticide residues in food: 1977 evaluations) Propineb (Pesticide residues in food: 1984 evaluations) Propineb (Pesticide residues in food: 1985 evaluations Part II Toxicology)