Table 5.

Summary of Studies Evaluating Styrene/SO in the in vitro Chromosome Aberration Assay

Cell type	Methods	Results	Comments	Reference
Styrene
Human lymphocytes	Single concentration: 0.03% v/v. Cytotoxicity measure: mitotic index. Chromosomal abnormalities, including interphase cells with MN, nuclear bridges, aneuploidy, polyploidy, breaks, and pulverized chromatids.	Mitotic index data not presented.	Not OECD TG473 compliant. The lack of an appropriate concurrent measure of cytotoxicity, scoring of events that are not currently normally scored and the use of a single concentration make this experiment uninterpretable.	Linnainmaa et al. (1978a, 1978b)
CHL cells	Methods not fully described. Scoring included polyploid cells in addition to structural aberrations.	The authors reported that styrene did not induce chromosomal damage; however, no data to evaluate.	Not OECD TG473 compliant. Insufficient data to evaluate. Uninterpretable.	Ishidate et al. (1981)
Human lymphocytes	Peripheral blood lymphocytes from a 29‐year‐old healthy female donor. Treated with concentrations between 5 × 10−4 and 5 × 10−6 mol/mL for 24 hr. No S9. When possible 200 metaphases scored per culture.	Data presented graphically. Authors report aberration percentage of 5% at the highest concentration (compared to 1.5% in the untreated control); however, there does not appear to be a dose‐related response and only the top concentration appears different than the untreated control.	Not OECD TG473 compliant. No measure of cytotoxicity. Uninterpretable.	Pohlová et al. (1984)
Human lymphocytes	Cultures with and without erythrocytes. Five concentrations between 0.5 and 6 mM styrene. Mitotic index used for cytotoxicity. 200 cells scored per culture.	Full tabulation of data. With erythrocytes: 4 mM culture had an appropriate level of cytotoxicity and was clearly positive (19 ± 3.0 aberrations per 100 cells compared to the untreated control which contained 2.0 ± 0 aberrations per 100 cells). Without erythrocytes: two concentrations (1 and 2 mM) of styrene with acceptable levels of cytotoxicity. Both concentrations appear to be positive (4.5 ± 0.5 and 7.0 ± 5.0 aberrations per 100 cells compared to the untreated control 1.5 ± 0.5).	Positive.	Jantunen et al. (1986)
Styrene Oxide
Human whole blood cultures	Methods not fully described. Two concentrations: 0.1 and 0.5 mM. 100 cells from control and 200 from each of two treated cultures scored. Gaps were included.	When gaps are excluded, the negative control had no aberrations, the low concentration had five aberrations and the top concentration had seven aberrations.	Not OECD TG473 compliant. Because there was no measure of cytotoxicity, only two test concentrations and insufficient technical detail, the study is considered uninterpretable.	Fabry et al. (1978)
Human lymphocytes	Single concentration: 0.008% v/v. Cytotoxicity measure: mitotic index. Chromosomal abnormalities, including interphase cells with MN, nuclear bridges, aneuploidy, polyploidy, breaks, and pulverized chromatids.	Mitotic index data not presented.	Not OECD TG473 compliant. The lack of an appropriate concurrent measure of cytotoxicity, scoring of events that are not currently normally scored and the use of a single concentration make this experiment uninterpretable.	Linnainmaa et al. (1978a, 1978b)
CHL cells	A single concentration (2.4 mM or 0.25 mg/mL) for styrene treatment was presented. No measure of cytotoxicity.	While no measure of cytotoxicity was used in the study, which evaluated a number of chemicals, it is clear from the text that concentrations were used for many of the test materials that resulted in no metaphases. Although the incidence of CAs was clearly much higher (and clearly positive) with S9 activation than without, it is not possible to determine the level of cytotoxicity attained in this culture.	Not OECD TG473 compliant. The lack of an appropriate concurrent measure of cytotoxicity, and only a single concentration make the experiment uninterpretable.	Matsuoka et al. (1979)
CHL cells	More than 400 chemicals were tested. Treatment times of 24 and 48 hr. Both with and without S9. Otherwise methods not fully described and no data provided.	No data included.	Not OECD TG473 compliant. No data. Uninterpretable.	Ishidate and Yoshikawa (1980)
CHL cells	Methods not fully described. Scoring included polyploid cells in addition to structural aberrations.	Reported data only a calculation of the concentration in which 20% of the cells had aberrations. For SO, this concentration was reported to be 0.057 mg/mL.	Not OECD TG473 compliant. Insufficient data to evaluate. Uninterpretable.	Ishidate et al. (1981)
Human lymphocytes	PHA‐stimulated lymphocytes from peripheral blood of healthy male donor. Three concentrations (0.05, 0.20, and 0.40 mM), 48 hr exposure. When possible 200 cells scored per culture. No measure of cytotoxicity.	The top concentration used for styrene resulted in no metaphases that could be scored. Although the middle concentration yielded a response that would clearly be positive, in the absence of an appropriate cytotoxicity measure it is not possible to determine if that concentration was excessively cytotoxic.	Not OECD TG473 compliant. No measure of cytotoxicity. Uninterpretable.	Norppa et al. (1981)
Human lymphocytes	Peripheral blood lymphocytes from a 29‐year‐old healthy female donor. Treated with concentrations between 1 × 10−3 and 5 × 10−6 mol/mL for 24 hr. No S9. When possible 200 metaphases scored per culture.	Data presented graphically. Authors report aberration percentage of 13.8% at the highest concentration (compared to 2% in the untreated control); there does appear to be a dose‐related response.	Not OECD TG473 compliant. No measure of cytotoxicity. Uninterpretable.	Pohlová et al. (1984)