In document Acrylamide(原文) (Page 139-144)

No human data on acrylamide developmental effects were located.

3.4.2 Experimental Animal Data

The Expert Panel notes that there are a number of genotoxicity studies with endpoints that might be considered developmental (e.g., abnormality of conceptuses after parental treatment). Studies that were designed to evaluate genotoxicity were grouped in Section 2. These studies include those with dominant lethal (section, heritable translocation (Section, and specifi c locus mutation (Section endpoints. In addition, the mouse spot test (Section 2.3.1) involves changes in the offspring after treatment of the pregnant animal, and could be construed as a developmental test. Although these studies are placed for organizational purposes under the heading of genotoxicity rather than developmental or reproductive toxicity, the Expert Panel considers these studies important

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in evaluating the reproductive and developmental effects of acrylamide. Key studies on acrylamide developmental toxicity are summarized in Table 28 (shown on page II-118). The most useful studies were those by Zenick et al. (81), Field et al. (118), and Wise et al. (121).

The study by Zenick et al. (81) was designed as a female reproductive toxicology study, but included data relevant to an assessment of developmental toxicity as well. Acrylamide was given in drinking water to female rats at 0, 25, 50, or 100 ppm [[0, 4, 5–9, 10–14 mg/kg bw/day]. After 2 weeks of treatment, untreated males were placed overnight with the females for up to 7 nights. Acrylamide-treated water was withheld during mating, but availability of Acrylamide-treated water resumed during pregnancy and lactation. Dams delivered their young and litters were culled to four males and four females on PND 4. Endpoints included maternal weight gain, mating performance, pregnancy rate, pup survival and weight, and day of vaginal patency in female offspring. Neurologic toxicity (hindlimb splay), total or near total litter loss, and reduced body weight and fl uid intake occurred in dams given 100 ppm acrylamide; dam body weight and fl uid intake also were reduced at several time points in the animals given 50 ppm acrylamide. Pup weight was decreased in a dose-dependent manner in the 50 and 100 ppm groups and was transiently depressed in the fi rst week of life in the 25 ppm group. A regression analysis performed without the 100 ppm group, due to incapacity of the dams, showed a signifi cant effect of cumulative acrylamide intake on litter weaning weight. The developmental fi ndings at 50 and 100 ppm may have been due, at least in part, to maternal toxicity seen at these doses. A LOAEL for developmental toxicity of 25 ppm (~4 mg/kg bw/day ) was selected by the Expert Panel based on transiently decreased pup weight. It could not be determined if developmental toxicity was due to maternal gestational or lactational treatment, or both.

Field et al. (118) evaluated developmental toxicity of acrylamide in Sprague-Dawley rats (29–30/

group) and Swiss CD-1 mice (30/group). Rats received acrylamide by gavage at 0, 2.5, 7.5, or 15 mg/kg bw/day on GD 6–20. Mice received acrylamide by gavage at 0, 3, 15, or 45 mg/kg bw/day on GD 6–17. Maternal weight decreased in a dose-dependent manner in both species. In rats, there was a dose-related increase in the percent fetuses per litter with variations and the percent litters with variations on trend testing but not on pair-wise comparison. In mice, fetal weight per litter was decreased 15% in both sexes in the highest dose group. There was a signifi cant linear trend for percent fetuses/litter with extra ribs and percent litters with extra ribs, although none of the pair-wise comparisons showed a signifi cant increase compared to control. The NOAEL for maternal and fetal toxicity in mice was 15 mg/kg bw/day. The NOAEL for maternal toxicity in rats was 2.5 mg/kg bw/

day, and the NOAEL for fetal toxicity was 15 mg/kg bw/day, the highest tested dose [the increase in variations was not considered an adverse effect].

Wise et al. (121) conducted a developmental neurotoxicity study of acrylamide in Sprague-Dawley rats. Animals received acrylamide at 0, 5, 10, 15, or 20 mg/kg bw/day by gavage from GD 6 through PND 10. Behavioral assessments included open-fi eld motor activity, auditory startle habituation, and passive avoidance. Dams in the 20 mg/kg bw/day group all demonstrated hindlimb splay and all dams and pups in this group died or were euthanized by PND 4 due to excessive pup mortality.

In the 15 mg/kg bw/day group, dams all displayed hindlimb splay between PND 4 and 9. Maternal toxicity also became apparent in the 10 mg/kg bw/day dose group during the lactation period, when there was a signifi cant decrease in weight gain compared to control animals. Perinatal mortality occurred in the 15 and 20 mg/kg bw/day groups and was attributed by the authors to the severely

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compromised condition of the dams. Open fi eld activity and startle amplitudes were altered in the 15 mg/kg bw/day exposure group. Absolute brain weights decreased while brain weights relative to body weights increased in offspring in the 15 mg/kg bw/day group, attributed by the authors to the marked decrease in body weight. The decrease in offspring weight at exposure levels higher than 5 mg/kg bw/day was attributed, at least in part, to maternal toxicity. The decrease in pup weight in the 5 mg/kg bw/day group on PND 3 and 7 was signifi cant only in females, and was considered possibly not treatment-related by the authors, given the transitory nature of this weight decrease, statistical signifi cance achieved only in one sex, and the lack of a similar effect on pup weight in the Field et al.

study (118) at maternal acrylamide doses under 15 mg/kg bw/day. The authors identifi ed a NOAEL for developmental toxicity at <5 mg/kg bw/day and a NOAEL for developmental neurotoxicity at 10 mg/kg bw/day. The Panel agrees with the NOAELs, with the conclusions that there was no selective developmental neurotoxicity observed in this study, and that 5 mg/kg bw/day was a marginal developmental effect/no effect level.

A study conducted at Bio/dynamics Inc. (115) in Sprague-Dawley CD rats administered acrylamide in the feed to females at 0, 25, or 50 ppm for 2 weeks prior to mating and from GD 0 to 19. Acrylamide intake was estimated at 1.75–1.90 and 3.45–3.82 mg/kg bw/day in the 25 and 50 ppm dose groups, respectively. Litters were standardized to 3 male and 3 female pups on PND 4 and pups were examined for postnatal growth and mortality until weaning (PND 21). There was a slight but signifi cant reduction in body weight gain in the 50 ppm dams during the pre-mating period. Mating and pregnancy indices, gestation length, neonatal viability, live litter size at birth, pup survival throughout the lactation period, and pup weights were similar in all treatment groups. On histopathologic evaluation of brain and spinal cord and sciatic, tibial, and plantar nerves (116), acrylamide-associated changes were (116), acrylamide-associated changes were (116 confi ned to scattered nerve fi ber degeneration in the sciatic and optic nerves. Details on the incidence and severity of these histologic effects were not provided, reducing the utility of these fi ndings.

A study by Rutledge et al. (119) is unique in that female mice were dosed with acrylamide selectively during the perifertilization period at 125 mg/kg bw i.p. 1, 6, 9, or 25 h after mating. These times represented fertilization, the early pronuclear stage, pronuclear DNA synthesis, and the 2-cell stage, respectively. On GD 17 the uteri were inspected for resorptions, embryonic death, and live fetuses.

Live fetuses were inspected for external abnormalities. The number of live fetuses was decreased and the number of resorptions was increased at all treatment times. Among live fetuses, abnormalities were increased with treatment 6, 9, and 25 h after mating. In spite of the lack of important details in the paper and a discrepancy between text and table in reporting the results, this study showed that an acute administration of acrylamide at a high dose during the perifertilization period can produce very early death or structural malformations.

Additional studies were limited in their utility. Edwards (44) used single-dose dietary exposures in a series of experiments in pregnant rats; however, the lack of experimental detail and small number of litters prevented this study from being useful. Neuhäuser-Klaus and Schmahl (61) performed what they termed a “teratogenicity study” in conjunction with a mouse spot test (discussed in Section 2.3).

Acrylamide was given i.p. as a single dose or as three daily doses, a route and/or dosing schedule that are not relevant to human exposures. Design and analysis issues prevented this study from being useful in the evaluation of developmental toxicity, although the fi ndings generally supported results

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from other studies. A study by Agrawal and Squibb (120) that administered acrylamide at 20 mg/

kg bw/day by gavage from GD 7–16 to rats was suggestive of transient changes in the postnatally developing dopaminergic system, although this study did not describe several aspects of methodology and analysis clearly enough to permit any certainty in its interpretation. A study by Husain et al. (109) and a study by Friedman et al. (123) addressed effects of acrylamide administered at 25 mg/kg bw/

day by gavage during lactation. Toxicity in both dams and pups was prominent and there was no way to separate maternal toxicity from developmental fi ndings, or direct from indirect (i.e., maternally mediated) developmental toxicity.

The Expert Panel found no human data with which to directly evaluate possible developmental toxicity of acrylamide. Data are suffi cient to conclude that acrylamide is a developmental toxicant in rats, as manifested by a decrease in pup weight with maternal drinking water or gavage doses of approximately 4–5 mg/kg bw/day. The Expert Panel noted that a well-conducted gavage study and a dietary study failed to fi nd this adverse effect at maternal doses of close to 15 mg/kg bw/day and 4 mg/kg bw/day, respectively; no explanation for the discrepant fi ndings between studies was apparent.

Further, the Expert Panel concluded that acrylamide can produce developmental neurotoxicity, manifested as alterations in open fi eld activity and decreased auditory startle amplitude in rat offspring at a maternal gavage dose of 15 mg/kg bw/day, a dose that also produced signs of maternal neurotoxicity. The Expert Panel concluded that acrylamide is a developmental toxicant in mice as manifested by decreased fetal weight per litter at maternal gavage doses of 45 mg/kg bw/day. The Expert Panel was unable to separate the effects of acrylamide on rat or mouse offspring from effects that may have been due to maternal toxicity at exposures ≥10 mg/kg bw/day, or to determine whether maternal gestational or lactational treatment, or both, was the critical period for producing developmental toxicity in rodents. The rat and mouse data are assumed relevant to the assessment of potential effects in humans.

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Table 28. Key Developmental Studies Species/strainExposuresMaternal/paternal Effect level

Critical Developmental Effects

Developmental Effect LevelReference Long-Evans rat

Drinking water: 0, 25, 50, 100 ppm 2 weeks prior to mating through weaning of litter LOAEL=50 ppm (6–9 mg/kg bw/day) [decreased fl uid intake and decreased body weight gain] NOAEL=25 ppm (4 mg/kg bw/day)

Decreased pup weightLOAEL=25 ppm (4 mg/kg bw/day; lowest tested level) Zenick et al. (81) Decreased litter sizeLOAEL=100 ppm (10-14 mg/kg bw/day) Sprague-Dawley ratGavage: 0, 2.5, 7.5, 15 mg/kg bw/day GD 6–20

LOAEL=7.5 mg/kg bw/day (decreased body weight gain) NOAEL=2.5 mg/kg bw/day

No adverse developmental effectsNOAEL=15 mg/kg bw/day (the highest tested dose)Field (118) Sprague-Dawley rat

Dietary: 0, 25, 50 ppm 2 weeks prior to mating and GD 0–19 LOAEL=50 ppm (3.45–3.82 mg/kg bw/day) (decreased body weight gain) NOAEL=25 ppm (1.75–1.90 mg/kg bw/day)

No adverse developmental effects (full teratology evaluation not performed)

NOAEL=50 ppm (3.45–3.82 mg/kg bw/day)Bio/dynamics Inc (115) Sprague-Dawley ratGavage: 0, 5, 10, 15, 20 mg/kg bw/day, GD 6–PND 10

LOAEL=10 mg/kg bw/day (decreased body weight gain in lactation period) NOAEL=5 mg/kg bw/day

Transient decrease in female pup weightBorderline NOAEL/LOAEL= 5 mg/kg bw/day Wise (121) Behavioral testing, brain weightLOAEL=15 mg/kg bw/day NOAEL=10 mg/kg bw/day Swiss CD-1 mouseGavage: 0, 3, 15, 45 mg/kg bw/day GD 6–17

LOAEL=45 mg/kg bw/day (decreased body weight gain) NOAEL=15 mg/kg bw/day Decreased fetal weight per litterLOAEL=45 mg/kg bw/day NOAEL=15 mg/kg bw/dayField (118) LOAEL= lowest observed adverse effect level NOAEL= no observed adverse effect level.

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