Residues (petroleum), heavy coker gas oil and vacuum gas oil

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

A number of samples of heavy fuel oil components have been tested in both in-vitro and in-vivo tests.  Variable results were seen but heavy fuel oil components showed no consistent evidence of mutagenic activity in a range of in vivo and in vitro assays other than in the Ames test.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Additional information

Additional information from genetic toxicity in vitro:

Results are available from a number of investigations that have examined the mutagenicity and genotoxicity of Heavy Fuel Oil Components in vitro and in vivo using GLP-compliant and/or guideline study designs.

 

A sample of heavy vacuum gas oil was positive in a bacterial mutagenicity assay (Modified Ames Assay; Mobil, 1986a). The same sample did not cause chromosomal damage in an in vivo micronucleus assay (Mobil, 1987a). These data do not provide convincing evidence of the mutagenicity of this material.

 

Cracked Heavy Fuel Oil Components have been tested in eight bacterial mutagenicity assays (Modified Ames Assay; API, 1986b; Pryzgoda, 1999; Feuston, 1994) and all but one of the assays was positive, the exception being visbreaker gas oil (Feuston, 1994). Other studies conducted included an in vitro mouse lymphoma assay (API, 1985b) which was positive with metabolic activation but only weakly positive without metabolic activation, two in vitro mammalian cell gene mutation assays (using Chinese Hamster Ovary (CHO) cells) one of which was negative (API, 1985c), while the second was positive in the presence of Aroclor 1254-induced rat S9 fraction and weakly positive in the absence of S9 fraction (API, 1985d). Additionally Cracked Heavy Fuel Oil Components have also been demonstrated to be negative in an in vitro cell transformation assay (API, 1986c) in the absence and presence of metabolic activation.

In a supporting study (Verspeek-Rip, 2015), 9 fume condensates of heavy fuel oils labelled CONCAWE A (01,02,03), CONCAWE-B (01,02,03) and CONCAWE-C (01,02,03), were examined for mutagenic activity in one histidine dependent auxotroph of Salmonella typhimurium, strain TA98 using the modified AMES test according to the ASTM Standard Test Method E 1687. Although some variations in control reproducibility were seen and issues with infected plates affected some of the results, overall the samples tested in this assay are judged to have a high probability of being non-carcinogenic in a mouse skin-painting bio-assay.

 

An in vivo sister chromatid exchange assay (API, 1985e) which tested catalytic cracked clarified oil was positive with and without metabolic activation, while the same sample was negative in an in vivo chromosome aberration test (API, 1985b). A cracked sample has also been demonstrated to cause unscheduled DNA synthesis in an in vivo study (API, 1985f). Eight in vivo micronucleus assays have also been conducted, all but two of which were negative (Pryzgoda, 1999; Mobil, 1990a, 1990b; 1987a, 1986b), while one was weakly positive (Mobil, 1989a), and the other positive (Mobil, 1991a).

 

It has long been recognised that the standard Ames assay is not sufficiently sensitive, even for petroleum streams that contain significant levels of 3-7 ring PAC, and this led to the development of the Modified Ames Assay which was able to identify those materials that were likely to be carcinogenic in skin painting bioassays. It was demonstrated further that activity in the Modified Ames assay was related to the 3-7 ring PAC content and also to the carcinogenic activity of the petroleum stream. Results from the modified Ames Assays that have been conducted on the Heavy Fuel Oil Components are therefore not sufficient alone to demonstrate mutagenic activity.

The mixed results from the other in vitro and in vivo studies do not provide consistent evidence of genotoxic activity and are not considered sufficient to conclude that heavy fuel oil components should be classified as mutagenic.

Justification for selection of genetic toxicity endpoint

The mutagenic activity of a number of samples of heavy fuel oil components have been assessed in both in-vitro and in-vivo test systems. Equivocal results were obtained but modified Ames tests gave positive responses in most cases.

Justification for classification or non-classification

The mutagenic potential of Heavy Fuel Oil Components has been extensively studied in a range of in vivo and in vitro assays. The majority of the studies showed no consistent evidence of mutagenic activity, particularly in in-vivo systems, and no classification is required under the EU CLP Regulation (EC No. 1272/2008).