Safety evaluation of certain food additives - ipcs inchem

166 POLYDIMETHYLSILOXANE (addendum)
At its thirty-seventh meeting in 1990 (Annex 1, reference 94), the Committee
revised the specifications for material with a weight-average molecular weight range
of 6800–30 000 (90–410 subunits) and a viscosity range of 100–1500 cSt (mm 2 /s).
However, the toxicological properties of this material were not re-evaluated. As a
consequence, material with an average weight at the lower end of this range was
outside the limits covered by the previously established ADI.
The Committee at its present meeting considered new studies on the
absorption of two PDMS products: a material with a viscosity of 10 cSt and a
number-average molecular weight of 1000 and a material with a viscosity of 350 cSt
and a number-average molecular weight of 10 000. New toxicological studies were
also reviewed: short-term studies in rats fed diets containing one of these two
materials at concentrations of 10 000–100 000 mg/kg diet and a long-term study
of toxicity and carcinogenicity with the 10 cSt material administered at doses of
100–1000 mg/kg bw.
2. BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution and excretion
The data on blood absorption of PDMS were reported in rats (Lukasiak &
Falkiewicz, 2000). They examined the blood of five Wistar rats fed for 12 days with
a granulated feed diet without PDMS, five rats fed for 12 days with the diet with
added 5% PDMS and five rats fed for 12 days with the diet with added 5% cyclo-
PDMS oil. Concentrations of PDMS were 26 ± 14 μg/cm 3 and 70 ± 97 μg/cm 3 in
samples from animals given feed PDMS and cyclo-PDMS, measured with a 1 H
nuclear magnetic resonance (NMR) technique. PDMS was not detected in any
blood sample from animals given feed without PDMS.
The absorption of [ 14 C]PDMS with viscosities of 350 cSt and 10 cSt from the
gastrointestinal tract was evaluated in male and female F344 rats 96 h following a
single oral gavage to 1000 mg/kg bw. Orally administered [ 14 C]PDMS with
viscosities of 350 cSt and 10 cSt was excreted unchanged in the faeces, with little,
if any, absorption. The total dose recovery of [ 14 C]PDMS with a viscosity of 350 cSt
in male and female rats was 97.4% and 93.6%, respectively; for [ 14 C]PDMS with a
viscosity of 10 cSt, the total dose recovery was 91.0% and 93.4% for male and
female rats, respectively (United States Environmental Protection Agency, 2000,
2001).
These absorption experiments are compared in Table 1.