Global Trends in Dietary Exposure to Polychlorinated Naphthalenes (PCNs): A Review of Contamination Levels and Health Implications

Polychlorinated naphthalenes (PCNs) belong to a class of persistent organic pollutants that are structurally related to chlorinated dibenzo-p-dioxins, dibenzofurans, and other chlorinated biphenyls as a result of the presence of benzene rings in their respective structures. Additionally, they display high levels of persistence in the environment, bioaccumulative, and dioxin-like toxicities characteristics. Although the production and use of PCNs is either banned or greatly regulated in several countries around the globe, unintentional production in industrial thermal processes and legacy usage have resulted in the ubiquity of these compounds in the environment and the food chain. Several studies have shown various exposure routes of PCNs, particularly dietary exposure as the major route for human exposure. However, an integrated approach is required to synthesize global data on PCN levels in foodstuffs and estimates of dietary exposure. In this review, data from research studies that have been published on PCNs from Asian, European, and other regions of the globe have been critically assessed comprising a broad spectrum of foodstuffs such as fish, seafood, meat, dairy produce, eggs, cereals, vegetables, and processed foods. The concentration levels, homologue distribution, and toxic equivalence factors have been critically examined, giving strong emphasis to regional variations and key foodstuffs for exposure. The available human exposure and risk assessment studies indicate consistently that the current dietary intake levels of PCNs are generally low and unlikely to pose health risks to the general population, though foods, especially fish and seafood, are the major contributors to exposure. Substantial data gaps still exist, however, particularly for Africa and other underrepresented regions, and also for some food matrices and highly toxic PCN congeners. This review emphasizes that there is an urgent need for expanded monitoring, harmonized analytical approaches, and further research in order to better characterise global dietary exposure to PCNs, as well as their use in support of informed risk assessment and food safety policies.