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Chromium in food and drinking water Table 16: NOAELs and LOAELs for the critical non-neoplastic toxic effects of Cr(VI). Effect Species Study duration NOAEL LOAEL mg Cr(VI)/kg b.w. per day Reference Haematology Rats 2-year 0.21 0.77 NTP (2008) Microcytic, hypochromic Mice 2-year - 0.38 NTP (2008) anemia (maximum effect after 22- 23 days) Liver Rats 2-year 0.21 0.77 NTP (2008) Enzyme induction 90-day 1.7 3.5 NTP (2007) Histiocytic cellular Mice 2-year - 0.38 NTP (2008) infiltration or glycogen 90-day 3.1 5.2 NTP (2007) depletion Chronic inflammation Rats 2-year 0.24 0.94 NTP (2008) 2.4* 7* 90-day 11.5 21.3 NTP (2007) Mesenteric lymph node Hystiocytic cellular infiltration Pancreatic lymph node Hystiocytic cellular infiltration Duodenum Hystiocytic cell infiltration Mice 2-year 3.1 8.7 NTP (2008) Rats 2-year 0.21 0.77 NTP (2008) Mice 2-year - 0.38 NTP (2008) Rats 2-year 2.4 7.0 NTP (2008) Mice 2-year 2.4 3.1 NTP (2008) Rats 2-year 0.21 0.77 NTP (2008) Hyperplasia Mice 2-year - 0.38 NTP (2008) Villous cytoplasmic vacuolisation Mice 90-day 1.1 4.7 4.7 12.2 Thompson al. (2011a) Apoptosis/crypt cell hyperplasia/ hystiocytic infiltration in the villous lamina propria Apoptosis Rats 90-day 0.2 3.6 Thompson et al. (2012b) Hystiocytic infiltration in Rats 90-day 0.2 3.6 Thompson et the villous 3.6 8.7 al. (2012b) crypt cell hyperplasia Jejunum Villous cytoplasmic vacuolation Mice 90-day 1.1 4.7 Thompson al. (2011a) et Crypt cell hyperplasia/hystiocytic infiltration in the villous lamina propria Hystiocytic infiltration in the villous Kidney degeneration of basement membrane in Bowman’s capsule and renal tubular degeneration Stomach Ulcer, hyperplasia, metaplasia 4.7 12.2 Rats 90-day 3.6 8.7 Thompson (2012b) Rats * increase severity of effect; b.w.: body weight. 22-week - 0.8 et Chopra et al. (1996) Mice 90-day 9.1 15.7 NTP (2007) Rats 90-day 11.1 20.9 NTP (2007) EFSA Journal 2014;12(3):3595 84
7.2.2.3. Developmental and reproductive toxicity Chromium in food and drinking water A number of studies have investigated the induction of reproductive effects in animals orally exposed to Cr(VI). Detailed review of these studies has been reported by EPA (U.S. EPA 1998b; CA EPA, 2009) and ATSDR (2012). NOAELs and LOAELs of the studies are reported in Table 17 and the studies are described in details in Table H6 (see Appendix H). No treatment-related effects on fertility or reproductive performance have been observed in 2-generation studies on mice exposed via the diet to potassium dichromate up to 400 mg/kg diet (corresponding to 30 mg Cr(VI)/kg b.w. per day) (NTP, 1997). In studies conducted on Sprague- Dawley rats or BALB/c mice exposed up to 400 mg/kg diet potassium dichromate daily (corresponding to 12.7 and 40.7 mg Cr(VI)/kg b.w. per day, respectively) for 9 weeks followed by a recovery period of 8 weeks, no effect on the testis and epididymes or spermatogenesis have been observed (NTP, 1996a, b, 1997). Similarly, exposure to sodium dichromate dihydrate in drinking water did not produce morphological changes to male reproductive organs of B6C3F1 mice exposed to 27.9 or 5.9 mg Cr(VI)/kg b.w. per day or F344 rats exposed to 20.9 or 5.9 mg Cr(VI)/kg b.w. per day for 3 months or 2 years, respectively (NTP, 2007, 2008) or affect sperm count or motility in B6C3F1, BALB/c and C57BL/6N mice exposed to 9.1 mg Cr(VI)/kg b.w. per day for 3 months (NTP, 2007). Other studies on Cr(VI) showed adverse reproductive effects, with the male reproductive system exhibiting the highest sensitivity. An inhibitory effect on sexual and aggressive behaviour has been observed in male rats treated with potassium dichromate via drinking water, as well as effects on the reproductive organs (decrease testes, seminal vesicles and preputial gland weights) at a dose of 1000 mg/L (corresponding to 32 mg Cr(VI)/kg b.w. per day) (Bataineh et al., 1997). In a study in mice potassium dichromate reduced seminal vesicles and preputial glands weight (Elbetieha and Al-Hamood, 1997). Reduction of epididymal sperm counts, increased frequency of abnormal sperm and decreased diameter of seminiferous tubules have been reported in rats dietary exposed to 10 mg/kg chromium trioxide (5 mg Cr(VI)/kg b.w. per day) (Li et al., 2001) (Li et al., 2001). Low doses of sodium dichromate (≤ 7.9 mg Cr(VI)/kg b.w. per day) caused partial loss of cellular activity in testicular tissues of rats whereas treatment with higher dose of chromium (≥ 15.9 mg/kg b.w. per day) caused deleterious effects both on spermatogenic and steroidogenic activity (Chowdhury and Mitra, 1995). The effect of Cr(VI) on spermatogenesis was studied in BALB/c mice (Zahid et al., 1990). Mice were given 100, 200 or 400 mg potassium dichromate/kg diet (corresponding to 16, 28 or 63 mg Cr(VI)/kg b.w. per day) for 7 weeks. Histological examination of the testes of treated animals revealed degeneration of the outermost cellular layers of seminiferous tubules with no spermatogenesis present and reported increase in the number of resting spermatocytes. Undegenerated tubules without spermatogenesis were significantly increased in all treated groups. Epididymal sperm count was lower at 200 and 400 mg/kg diet and the percentage of morphologically abnormal sperm was higher. Chromium treatment was reported to cause accumulation of germ cells in resting spermatocyte stage. These data are of questionable value because the methods described by the authors were not sufficient to show that they could identify spermatogonia. The methods used to evaluate the epididymal sperm very probably resulted in clumped sperm and poorly reproducible counts and the reduction in spermatogonia numbers concurrent with unchanged spermatocyte and spermatid numbers is biologically implausible. Moreover there are inconsistencies regarding the number of mice used in the study, the sizes of the experimental groups do not satisfy minimal requirements for such toxicity study and inappropriate statistical methods were used (Finley et al., 1993; NTP, 1996b). Moreover, no effects have been observed in a similar study performed by the NTP (1996b). Therefore, the CONTAM Panel did not take into account the results of the Zahid et al. (1990) study for the evaluation of the reproductive toxicity of Cr(VI). Effects on testes and epididymal weights as well as on sperm have also been reported in rabbits exposed to potassium dichromate (Yousef et al., 2006). EFSA Journal 2014;12(3):3595 85
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