Dr Swan’s research began by examining phthalate syndrome, something observed in rats which found that when fetuses were exposed to the chemical they were likely to be born with shrunken genitals.

She discovered that male human babies who had been exposed to the phthalates in the womb had a shorter anogenital distance – something that correlated with penile volume.

The chemical has an industrial use in making plastics more flexible, but Dr Swan says it is being transmitted into toys and foods and subsequently harms human development.