Withdrawal of Claim that Azo Blue Causes Congenital Malformations

Abstract

In a recent paper (1) in this Journal I presented data indicating that injection of a solution of the diazo dye azo blue into pregnant rats caused congenital malformations in the offspring. The experiment could not be repeated in the laboratory of Professor H. Tuchmann-Duplessis, University of Paris, who was gracious enough to inform me of this fact immediately. As a consequence, I returned the sample of my dye to the supplier for analysis. He finds that the substance purchased by me as azo blue was in reality the closely related dye trypan blue. This makes it necessary that I withdraw the claim that azo blue causes malformations as described in the published paper. The results attributed to the action of azo blue become valid if ascribed, instead, to trypan blue. All other observations in the same paper stand as presented.

An investigation into the manner in which the mistake was originally made revealed that the lot of dye in question was manufactured in 1941 as trypan blue. It was divided into two batches and placed in separate containers, each bearing the same lot number. For reasons not known, one of these containers was mislabelled azo blue while the other was correctly labelled trypan blue, although both retained the correct lot number. The company which manufactured the dye and originally mislabelled it is no longer in business. Needless to say, the company that has recently distributed the dye has made every effort to recall all samples of the erroneously labelled product, I am grateful to Professor Tuchmann-Duples-sis for informing me promptly of his negative results, and to the editor of the Proceedings for affording this opportunity to correct the error.