Derivation of exposure factors for infant lactational exposure to persistent organic pollutants (POPs)

Quantifying the influence of breastfeeding on infant's dose and biological levels is critical for the risk assessment of persistent organic pollutant (POP) early exposures. We aimed to quantify infants' exposure relative to the mother for POPs. Using a validated pharmacokinetic model, Monte-Carlo simulations of infants' exposure during the first 2 years of life for POPs of different half-lives (i.e., 1-20 years) were performed. Infant:mother (I:M) ratios for dose and biological levels throughout infancy were derived. To evaluate model accuracy, simulated I:M biological level ratios were compared to ratios calculated from Inuit mothers' and infants' measured plasma levels of 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB-153), p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) and hexachlorobenzene (HCB). Practically all measured I:M biological level ratios from the Inuit cohort fell below the 95th percentile of the distributions of simulated PCB-153, p,p′-DDE and HCB levels. Peak I:M dose ratios were observed at the beginning of lactation with 95th percentile values of 13, 53, 84, 102 and 113 for half-lives of 1, 5, 10, 15 and 20 years, respectively. In contrast, peak I:M biological level ratios occurred after approximately 1 year of breastfeeding and plateaued at approximately 10.5 (95th percentile) for chemicals of half-lives >5 years. Simulated I:M dose and biological level ratios could be employed in risk assessment of early POP exposures through breastfeeding.