Chloronaphthalenes as food-chain contaminants: a review

Chloronaphthalenes are dioxin-like environmental and food contaminants that for many years have undergone diffusion from dispersed emission sources of various types on a global scale. When released into ambient air like many other semivolatile organohalogen compounds, chloronaphthalenes undergo various processes and pathways including sequestering by plant vegetation and biota. Recently available data indicate that sequestering rates of chloronaphthalenes by plant biomass and including edible plants as well as concentrations in food sources of plant origin can be greater than was earlier predicted. Additionally, it become known very recently that in some highly industrialized countries such as Japan, Canada and the UK, the technical chloronaphthalene mixtures are still a subject of industrial and commercial interest, even if such activities are illegal. Recent achievements in HRGC-HRMS have enabled elucidation and quantification of the chloronaphthalene congener composition in environmental matrices, food sources and technical mixtures, their persistency, environmental fate, accumulation in biota and potential for food chain biomagnification. However, at the same time this raised questions regarding human exposure to these compounds. By the late 1990s, these developments added to the relatively rapidly growing knowledge on these compounds and especially individual congener properties such as thermodynamic and physicochemical features and toxicity. Multistage fractionation has recently enabled routine congener-specific quantification of tetra- to octachloronaphthalene in various matrices. This paper reviews the literature on chloronaphthalenes as food chain contaminants and covers their origin, physicochemical properties, toxicity, environmental concentrations and persistency, and homologue group and congener composition in various matrices. The review also covers distribution in environmental compartments and subsequent fate and migration to food sources, as well as the magnitude of dietary intake and human body concentrations. Data on chloronaphthalene residues in food, however, are still scare, an exception being seafood sources and recently available data from Spain on their concentrations in staple foods and dietary intake.