2-vinylpyridine

Endpoint summary

Additional information

The genotoxicity of 2-vinylpyridine has been studied in three bacterial reverse mutation assays. In all assays performed with Salmonella typhimurium, the test material was found to be nonmutagenic both with and without metabolic activation. When an alternative bacterium was studied, Escherichia coli with the WP2 uvr A mutation, 2VP (98.3% purity) was positive with metabolic activation (negative without activation).  An increase in the number of mutant colonies was observed based on average mutation frequency, primarily in cultures at high doses between 1500 and 2500 microgram/plate. Higher concentrations caused toxicity. A confirmatory trial was undertaken with six doses ranging from 2500 to 5000 microgram/plate.  The extent of increase was not impressive (around 2-fold), and was significantly lower than the values of the positive control. No statistical analysis was performed on the data, and a dose-response was not always demonstrated.  The criteria for consideration as mutagenic was defined as a dose-related increase in revertant colony count and the number of revertant colonies per plate with the test substance was more than twice that of the negative control, and when reproducibility of test result was observed. Based on the one guideline study, 2VP may initally be considered mutagenic in vitro.  

Chromosomal aberrations were studied after continuous or short term exposure to 2VP in the same laboratory using Chinese Hamster Lung (CHL) cells. Cells were exposed for either 24 h, 48 h (both without activation) or for 6 h (short term) with or without metabolic activation (rat liver induced with Phenobarbital and 5,6-benzoflavone).  The highest concentrations tested in each group were: 30 microgram/ml for 24 h, 15 microgram/ml for 48 h, 120 microgram/ml for short term-no activation, and 300 microgram/ml for short term-with activation.  Treatment with 2VP in all four exposure groups resulted in an increase in the incidence of various aberrations, especially at high doses. These data seem to demonstrate a dose response relationship, however, as no statistical analysis was performed, it is difficult to determine if the increase in the number of aberrations was not increased due to chance. There appeared to be several instances where the positive control for the short-term treatment, cyclophosphamide, did not induce clastogenic results. Among the various aberrations, there were few chromosome breaks in any of the four experimental group; most of the aberrations were chromatid breaks or exchanges. Data were positive for aberrations excluding as well as including chromatid breaks.  The results of this study suggest positive (clastogenic) findings for 2VP when administered in vitro under these conditions.

A second clastogencity test is available, using the Williams Assay (performed by the laboratory of the author of the test, Dr. Gary Williams) in rat primary hepatocyte culture. This assay was similar to the U.S. Environmental Protection Agency's test protocol OPPTS 870-5550. Hepatocytes were cultured at concentrations of 2VP at doses from 2.5 to 10 mM; however, excess toxicity was observed in all concentrations other than 2.5 mM. At this subtoxic dose, 2VP was found to be negative, with no induction of DNA repair. This test was part of a larger study of 2VP (99% pure) where mutagenicity was assessed in bacteria and in mice via the expression of lung tumors. All assessments of genetic toxicity in this series of experiments were negative (nongenotoxic).

 For further detail on the in-life portion of this study, 2-vinylpyridine was investigated in a non-guideline mouse lung tumorigenicity assay. The substance was administered intraperitoneally three times weekly for 7 weeks to A/J mice at one dose of 200 micromol/mouse.  Statistical analysis was performed using Student’s t-test. After 20 weeks of a post-dosing observation period, no increase in adenoma frequency was observed. The positive controls (the nicotine derivative NNK) demonstrated significant increases in lung tumors (24 +/- 7 per animal). 2-Vinylpyridine was judged to be non-genotoxic and non-tumorigenic. 

 The behaviour of 2VP in an in vivo mouse micronucleus was estimated using a validated structure-activity relationship model. The model, composed primarily of chemicals tested in the U.S. National Toxicology Program (NTP), located substructures similar to those in 2VP within the reference dataset and reported the activity of these chemicals in the micronucleus assay. The model predicted that 2VP is negative (non-genotoxic) in inducing micronuclei. Furthermore, as the ultimate outcome of mammalian mutagenicity is often malignant tumor formation, a prediction of carcinogenic activity is a strong but indirect assessment of mutagenic behavior.

2VP was investigated by a computer model in a cancer bioassay model based on the Carcinogenic Potency Database of chemicals. In this model, 2VP was predicted to be inactive (non-carcinogenic). 

 In summary, the genotoxicity of 2VP has been investigated in both in vitro and in vivo tests. The majority of studies indicate that 2VP shows no evidence of mutagenicity or clastogenicity. One laboratory produced two studies which suggest genotoxicity.  The robustness of these conclusions is very weak due to the absence of statistical analysis to verify with certitude whether a change was due to chemical exposure rather than to chance. There is sufficient uncertainty about the conclusions to suggest that these screening studies be repeated before a conclusion of genotoxicity is considered. While the in vivo study investigating the indirect mutagenicity (as tumor formation) of 2VP is an older, non-guideline study, the absence of tumors is an important finding. As in vitro mutagenicity tests are surrogates for worst-case exposure in humans, the negative findings in an animal model suggest pharmacokinetic handling to minimize the development of damage associated DNA replication or tumors, or frank absence of genotoxicity in vivo. This is supported by two modeling exercises indicating that chemicals with structures similar to those found in the 2VP molecule are not associated with in vivo micronucleus formation or cancer development. 

 The weight of evidence indicates that 2VP is not mutagenic or otherwise genotoxic. 

 2-Vinylpyridine is a highly reactive molecule which would likely react immediately upon contact with cellular structures including cell membranes.  It is corrosive to the skin and severely irritating to the eye. When administered by gavage to animals, the non-glandular stomach becomes irritated, showing signs of inflammation, granulation and acanthosis upon repeated exposure. The introduction to Annex VIII of the REACH legislation states that "in vivo testing with corrosive substances at concentration/dose levels causing corrosivity shall be avoided."  It is inappropriate that, within the spirit of REACH, further in vivo testing of 2VP is undertaken without a significant indication of probable genotoxicity.

Short description of key information:
A weight of evidence approach was applied to the evaluation of studies of the mutagenicity of 2VP. The conclusion is that 2VP is not genotoxic.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

A weight of evidence approach results in a conclusion that 2VP is not genotoxic.