IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

3.4 Intraperitoneal administration
3.4.1 Mouse
In a screening assay based on multiplicity and incidence of lung tumours in a highly
susceptible strain of mice (A/J), administration of 200 μmol (~100 mg/kg bw) styrene by
intraperitoneal injection three times per week for 20 doses, followed by observation for
20 weeks, produced no increase in lung adenoma incidence in the styrene-treated mice
compared with controls (Brunnemann et al., 1992).
3.4.2 Rat
Groups of 40 male and 40 female Sprague-Dawley rats, 13 weeks of age, received
four intraperitoneal injections of 50 mg styrene (99.8% pure) per animal in olive oil at
two-month intervals. Control groups received olive oil alone. The study was terminated
when the last rat died [duration unspecified]. There was no increase in tumour incidence
(Conti et al., 1988). [The Working Group noted the incomplete reporting of data, the
short duration of treatment and the low total dose.]
3.5 Subcutaneous administration
Rat: Groups of 40 male and 40 female Sprague-Dawley rats, 13 weeks of age,
received a single subcutaneous injection of 50 mg styrene (> 99% pure) per animal in
olive oil. Control groups received olive oil alone. The study was terminated when the last
rat died [duration unspecified]. There was no increase in tumour incidence (Conti et al.,
1988). [The Working Group noted the incomplete reporting of data and the single lowdose
treatment.]
4. Other Data Relevant to an Evaluation of Carcinogenicity
and its Mechanisms
4.1 Absorption, distribution, metabolism and excretion
Studies on the pharmacokinetics and metabolism of styrene were evaluated in 1994
as part of a previous IARC monograph (IARC, 1994a), which may be consulted for more
details on the earlier studies.
4.1.1 Humans
(a) Absorption
STYRENE 479
As noted previously (IARC, 1994a), the pulmonary retention of styrene is 60–
70% of the inhaled dose based on studies in both volunteers and workers (Stewart et al.,