“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.”
It’s often told that a grandmother’s environment and lifestyle effects her unborn grandchildren, because a grandmother’s daughter carries all her children’s eggs inside her tummy too. Grandparents also have an effect on mitochondrial health, pointing to a new study on grandfathers.
A grandfather’s exposure to endocrine-disrupting chemicals, perhaps at work or on the farm, may impact the age when his granddaughter starts her first period, according to a study being presented Sunday at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco, Calif.
“Girls are starting puberty earlier than ever before, which can raise their risk for health problems later in life,” said lead researcher Xin Hu, PhD, of Emory University’s Rollins School of Public Health in Atlanta, Ga. “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.”
Endocrine-disrupting chemicals (EDCs) are substances in the environment (air, soil, or water supply), food sources, personal care products, and manufactured products that interfere with the normal function of the body’s endocrine system. Since EDCs come from many different sources, people are exposed in several ways, including air, food and water. EDCs also can enter the body through the skin. Microplastics are also a possible source.
The researchers used data from the Child Health and Development Studies (CHDS), a long-term study that began in the 1960s. They measured thousands of small molecules in blood samples taken from 249 couples in the 1960s. The researchers linked the couples’ chemical and metabolic profiles to the timing of puberty in their daughters and granddaughters.
The researchers studied the age at which their daughters (247 girls) and granddaughters (139 girls) started their periods. They found that while the median age of having a first period was stable between the grandmothers and their daughters, it dropped a full year from the daughters to the granddaughters, whose median year of birth was 1990.
They discovered that certain chemicals in both the mother’s and father’s blood were linked to when their descendants began puberty, with stronger effects seen in the granddaughters’ than in the daughters’ generation. Some chemicals such as phenoxyethanol, a common preservative in personal care products and foods, were linked to earlier puberty, especially when both parents had similar exposures.
“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,” Hu said. “Paternal exposure to environmental chemicals may play an unrecognized but critical role in shaping offspring endocrine health.”
She said this is the first population-based study to show that a father’s environment can affect reproductive development in both his daughter and granddaughter. “These findings highlight that prevention is possible if we identify mechanisms to protect future daughters and granddaughters, which cannot be effective if we do not consider the male line,” she said.
“Our results highlight the role of endocrine-disrupting chemicals during the vulnerable period of conception and pregnancy,” said senior author Barbara Cohn, PhD, MPH, of the Public Health Institute in Berkeley, Calif. “This research emphasizes the lasting impact of environmental exposures on reproductive health across generations.”
