Breastfeeding duration and residential setting in relation to childhood exposure to organochlorine pesticides and PCBs: a longitudinal study of the Rhea cohort in Crete

Despite decades-old bans, persistent organic pollutants (POPs), including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), remain a public health concern owing to persistence and bioaccumulation. Previous Rhea mother–child cohort analyses (Crete, Greece) reported notably high DDE (DDT’s main metabolite) in children, raising questions about postnatal pathways sustaining this post-ban burden. We aimed to characterise associations of residential setting, breastfeeding duration and childhood diet with children’s serum OCP and PCB concentrations, accounting for maternal prenatal serum concentrations. Using linear mixed-effects models, we related breastfeeding duration and residential setting to 947 serum measurements from 443 Rhea children at ages 4, 6.5 and 11 years (n = 375, 239 and 333, respectively). Breastfeeding duration showed the strongest associations, with >4 months (versus never) consistently associated with higher DDE+DDT sum, HCB and PCB concentrations. Associations were strongest at age 4, then attenuated, consistent with growth dilution and elimination, but remained statistically detectable for DDE+DDT sum to age 11, independent of recent diet and parental agricultural occupation. Breastfeeding duration associations were stronger at higher maternal prenatal HCB concentrations (borderline for PCBs), consistent with lactation as one route of maternal-to-child transfer of accumulated body burden. Contrary to the hypothesis that agricultural proximity drives exposure, urban versus rural Heraklion residence was not significantly associated with serum POPs after adjustment for maternal prenatal concentrations, diet and household characteristics. Rather than implying any change to breastfeeding practice, these findings support reducing POP body burden in reproductive-age women, particularly before conception, during pregnancy and lactation, through continued exposure monitoring.