Grandfather’s chemical exposure may affect puberty timing

A grandfather’s contact with environmental chemicals could influence when his granddaughter starts her period, new research suggests.

Scientists found that exposure to certain chemicals in both parents—particularly fathers—was linked to earlier puberty onset in daughters and granddaughters, with the average age falling by one year between generations.

Researchers from Emory University’s Rollins School of Public Health analysed data from the Child Health and Development Studies, which has tracked families in the US since the 1960s.

The team examined blood samples from 249 couples, measuring thousands of small molecules and chemical profiles. These were linked to puberty onset in 247 daughters and 139 granddaughters born around 1990.

While the average age at first period remained the same between grandmothers and mothers, it dropped from 13 to 12 years in the granddaughters.

One chemical in particular—phenoxyethanol, a preservative used in personal care products and foods—was associated with earlier puberty, especially when both parents had similar exposure levels.

 Xin Hu of Emory University’s Rollins School of Public Health in Atlanta said: “Girls are starting puberty earlier than ever before, which can raise their risk for health problems later in life.

“We wanted to explore why this might be happening by looking at how environmental exposures from grandparents can influence when girls get their first period.”

While maternal and paternal exposures both played a role, the father’s influence stood out.

Hu said: “While we found that both the mother’s and father’s exposures were linked to when their daughters and granddaughters began puberty, the father’s influence was surprisingly strong.

“Paternal exposure to environmental chemicals may play an unrecognised but critical role in shaping offspring endocrine health.”

Earlier puberty has been linked to increased risks of obesity, type 2 diabetes, certain cancers and depression, making these findings particularly significant.

In the US, the average age for a first period is now around 12, with some girls beginning as early as eight.