Montreal Gazette - Dr. Joe: Altering the male-female birth ratio

(Joe Schwarcz, McGill University Dept. of Chemistry)

"The train on the way from Milan to Lake Como pulled into a small railway station. I was looking out the window and noted a number of pretty girls waiting on the platform. Yes, even chemistry profs do notice such things.

But what really grabbed my attention was a sign. Seveso! I had often talked about the "Seveso incident" in lectures, a landmark case in the annals of toxicology, but had never given much thought to where exactly in Italy the town was located. And here it was! Furthermore, the plethora of young ladies on the platform now made some sense. Sort of.

The famous incident at Seveso occurred in 1976 when a chemical plant producing trichlorophenol accidentally released a significant amount of dioxin, a toxic byproduct, into the environment. At the time, trichlorophenol was needed for the production of the disinfectant hexachlorophene and the herbicide 2,4,5-trichlorophenol (2,4,5-T). Dioxin was already known to be extremely toxic to some animals, but until the Seveso incident, no human population had been exposed to the chemical to such an extent. […]

After the dioxin release, the male to female ratio of newborns in Seveso decreased! Was it evidence of this phenomenon I was now seeing on the train platform? Could it be that exposure to dioxin had somehow selectively affected sperm that carry the Y chromosome, the one that results in a male baby when it unites with the egg's X chromosome?"