Safety evaluation of certain food additives - ipcs inchem

ALKOXY-SUBSTITUTED ALLYLBENZENES 395
Newborn male B6C3F1 mice (50–60 per group) were given four
intraperitoneal injections of methyl eugenol and 1-hydroxymethyl eugenol. The
doses were administered on days 1, 8, 15 and 22 of life, with fractions of the total
dose increasing with the age of the mice corresponding to the ratio 1:2:4:12
(i.e. 0.25, 0.5, 1.0 and 3.0 mg), respectively. A vehicle control group (trioctanoin)
and an untreated group were also included in the study. Surviving mice were
sacrificed at 18 months. Increased incidences of hepatocellular carcinomas (P <
0.001) were observed for mice treated with methyl eugenol (3.2 hepatomas per
mouse) and 1-hydroxymethyl eugenol (3.5 hepatomas per mouse) relative to the
incidence for the vehicle controls (0.5 hepatoma per mouse) (Miller et al., 1983).
(ii) Rats
Groups of 50 male and 50 female F344/N rats were administered methyl
eugenol (99% pure) in 0.5% methylcellulose by gavage daily at dose levels of 37,
75 or 150 mg/kg bw per day, 5 days per week, for 2 years (National Toxicology
Program, 2000). Stop-exposure groups received doses of 300 mg/kg bw per day
for 53 weeks, followed by the vehicle only (0.5% methylcellulose) for the duration
of the study.
All males in the 150 and 300 mg/kg bw per day dose groups died before the
end of the study. Mean body weights of all dosed groups were much lower than
those of the vehicle controls throughout the study. Since the minimal toxic dose
(MTD) is defined by NTP as the dose at which there is a 10% or greater depression
in weight gain compared with controls, weight gains in animals at the 150 and 300
mg/kg bw per day dose levels were well above those at the MTD, and weight gain
at 75 mg/kg bw per day was at those at the MTD (i.e. ~10%). The incidences of nonneoplastic
lesions in livers of dosed groups of males and females were increased
at 6 months, 12 months and 2 years. There were increases in oval cell hyperplasia,
hepatocyte hypertrophy and eosinophilic foci at all dose levels in male and female
rats. At the three highest doses (75, 150 and 300 mg/kg bw per day), atypical focal
bile duct hyperplasia, focal cystic degeneration and mixed cell foci were observed,
more in males than in females. Many of the same non-neoplastic lesions of the liver
were reported in the 300 mg/kg bw per day groups of male and female rats at both
6 and 12 months in the stop-exposure groups.
In males, hepatocellular adenomas and carcinomas were observed in control
and all dosed groups. Hepatocholangiomas and hepatocholangiocarcinomas
occurred only in the 75 (1), 150 (3) and 300 mg/kg bw per day (7) groups. Based
on the spontaneous background nature of hepatocellular adenomas and
carcinomas in male rats (14%), application of the NTP guideline (Haseman et al.,
1984) indicates that while there was a statistically significant increase in liver
tumours (56%, P < 0.01) in male rats at the MTD of 75 mg/kg bw per day, the
incidence of liver tumours at 37 mg/kg bw per day was not statistically significant
(28%, P = 0.049).
In females, liver neoplasms occurred in control and all dosed groups. In
controls and the 37 mg/kg bw per day group, adenomas were reported (1/50 and
8/50, respectively). No liver carcinomas were observed in females at the low dose.
In the 75 mg/kg bw per day group, increases (P < 0.01) in the incidences of