Researchers find link between late onset of puberty with pesticide exposure

Researchers in Spain have found that exposure to two common pesticide-related compounds was associated with changes in the timing of menstruation, with one linked to an earlier first period and the other associated with a later one.

The findings suggest that chemicals capable of disrupting hormone activity may influence puberty in different, and sometimes opposing, ways, as highlighted by the SciTechDaily outlet.

The study, published in the Environmental Research journal, involved 506 girls participating in the INMA (Childhood and Environment) collaborative birth cohort study. Researchers from the University of Granada and the ibs.granada Biomedical Research Institute followed participants from Asturias, Guipúzcoa, Sabadell and Valencia.

Urine samples were collected between 2013 and 2016, when the girls were between seven and 10 years old. Researchers analysed the samples for compounds produced as the body processes several pesticides.

The girls were then followed until ages 14–16, with researchers recording when each participant experienced her first menstrual period.

The clearest association involved ethylenethiourea (ETU), a residue associated with dithiocarbamate-type fungicides.

Girls with higher concentrations of ETU tended to experience menarche, or their first menstruation, at a younger age.

ETU can interfere with thyroid function. Because thyroid hormones play an important role in coordinating growth, metabolism and development, researchers suspect that disruption of thyroid activity could affect the biological signals that control the onset of puberty.

A different pattern emerged for TCPy, a substance produced when the body breaks down the insecticide chlorpyrifos.

Girls in whom TCPy was detected generally began menstruating later. The association was particularly noticeable among participants who were overweight or obese, suggesting that body composition may influence how chemical exposures affect development.

Puberty depends on a carefully coordinated exchange of signals between the brain, ovaries, thyroid and other parts of the endocrine system.

Endocrine-disrupting chemicals can interfere with this communication by mimicking hormones, blocking their effects or altering how hormones are produced and processed. Exposure may be particularly significant during childhood, when the reproductive system is still developing.

The timing of a first period is more than a developmental milestone.

Earlier menstruation has been associated with emotional and psychological difficulties during adolescence, as well as a higher risk of hormone-dependent cancers, including breast cancer, later in life.

Delayed puberty can also signal disruptions in development, although its causes and potential consequences can vary widely.

The researchers' findings do not establish that the pesticide-related compounds directly caused changes in the timing of menstruation, but they add to evidence that environmental chemical exposure may influence pubertal development.

Pesticide restrictions in Europe

Chlorpyrifos and several dithiocarbamate fungicides, including mancozeb and maneb, are no longer approved in the European Union because of concerns involving neurological development, fertility and environmental damage.

Chlorpyrifos has also been targeted internationally as a persistent organic pollutant. However, exposure can continue through residues, environmental contamination, imported products or other pesticides that remain in use.

Under the “Farm to Fork” strategy of the European Green Deal, the EU has set non-binding targets to reduce both the use and risk of chemical pesticides, as well as the use of more hazardous pesticides, by 50% by 2030.

Studies such as this one could help identify which chemical exposures warrant the closest attention as regulators work towards those targets.

By Nazrin Sadigova