Absence of mutagenic activity of sodium borate (borax) and boric acid in the Salmonella preincubation test

The mutagenicity of borax and boric acid was examined in Salmonella typhimurium strains TA98 and TA100 by the preincubation method. No mutagenic activity of borax or boric acid was observed with or without S-9 rat liver enzymes. Experiments also were conducted to investigate the enhancement or inhibition of benzo[a]pyrene (B[a]P) mutagenicity by the two compounds. Neither Borax nor boric acid had any effect on the response of S. typhimurium test strains to B[a]P. Studies conducted to determine the influence of exposure to sunlight for 8 h on the mutagenicity of these materials showed that the nonmutagenic activity of borax or boric acid was not altered, but that the mutagenicity of B[a]P was reduced by approximately one-half. Photodecomposition may be an important factor in rendering this polycyclic aromatic hydrocarbon nonmutagenic under environmental conditions.