Burden and Risk of Polychlorinated Naphthalenes in Chinese Human Milk and a Global Comparison of Human Exposure.

Polychlorinated naphthalenes (PCNs) are carcinogenic contaminants. Residues from historical production and ongoing unintentional releases from industrial thermal sources have led to the ubiquitous presence of PCNs in the environment. Our previous study has revealed that unintentional releases may be the main sources of PCNs in human milk from China. However, an assessment of PCN burden in human milk and exposure differences between historical residues and unintentional release exposure has not been conducted. In this study, we performed the first comparison of human exposure to PCNs and evaluated the differences between the estimated health risks from historical residues and unintentional releases. Three characteristic PCN congener patterns found in Chinese human milk specimens collected from 100 cities/counties can be considered characteristic of PCN exposures in regions with unintentional industrial releases as the main PCN sources. The health risk assessment suggested potential noncarcinogenic health effects in infants aged 0-6 months. The hazard index calculated for infants in Sweden indicates a strong impact of historical residues that nonetheless decreases over time, and a comparison of the hazard indices calculated for China and Ireland suggests that ongoing unintentional formation and release of PCNs from industrial processes should be a matter of public health concern.