Is it true that sodium benzoate is carcinogenic?
Well, no according to “Final report on the safety assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate.” Nair, B. 2001 Int. J. Toxicol. 20 Suppl 3:23-50. The abstract can be read here – and I downloaded the pdf. The report cites two carcinogenicity studies for soudium benzoate, one in which they fed rats the sodium benzoate (220-280 mg/rat/day) and one in which mice’s drinking water was spiked with 2% sodium benzoate. In neither experiment was there any increase in the number/amount of cancers seen. In a few experiments on cells in cell culture (2 of the 10 reported) sodium benzoate did induce some changes in chromosomal abnormalities and it is possible (though pretty unlikely IMO) that those might lead to cancer. Sodium benzoate can produce skin irritations and rashes which can be a worry as it is mainly used in cosmetics and creams.
