Grandfather's Exposure to Environmental Chemicals May Affect Timing of Girls' First Period

Recent research presented at ENDO 2025 reveals that a grandfather's exposure to certain environmental chemicals could influence the age at which his granddaughter experiences menarche, the first menstrual period. The study highlights intriguing intergenerational effects, emphasizing how chemical exposures in one generation can impact reproductive development in subsequent generations.

Scientists analyzed longitudinal data from the Child Health and Development Studies (CHDS), conducted since the 1960s, which included blood samples from couples and information about their children’s pubertal timing. They particularly focused on endocrine-disrupting chemicals (EDCs)—substances commonly found in air, soil, water, food, personal care products, and manufactured items—that interfere with endocrine system functions.

The findings showed that although the average age of menarche remained consistent over time for the immediate generations, there was a notable decrease of approximately one year from the daughters to the granddaughters, who were born around 1990. This shift appears to be linked to specific chemicals present in parents’ blood, with stronger effects observed in the granddaughters. Notably, chemicals such as phenoxyethanol, a preservative in many personal care products and foods, were associated with earlier puberty, especially when both parents had similar chemical exposures.

An unexpected and significant discovery was the strong influence of paternal exposure. The study suggests that environmental chemical exposure in fathers may play a critical role in shaping the reproductive development of both their daughters and granddaughters, a factor previously underappreciated in reproductive health research.

This groundbreaking research underscores the importance of considering paternal environmental factors and their potential long-term effects on health across generations. The authors believe that understanding these mechanisms can lead to better prevention strategies for early puberty and related health issues later in life. Senior researcher Barbara Cohn emphasized that protecting future generations requires addressing both maternal and paternal exposures, particularly during conception and pregnancy.

The study titled "Transmission of environmental health risks across generations and the impact on age at menarche" will be further discussed during ENDO 2025. These findings highlight the lasting influence of environmental exposures and the need for targeted public health interventions to reduce harmful chemical contact across all reproductive ages.