Country‐specific chemical signatures of persistent environmental compounds in breast milk

Abstract

Recent reports have confirmed a worldwide increasing trend of testicular cancer incidence, and a conspicuously high prevalence of this disease and other male reproductive disorders, including cryptorchidism and hypospadias, in Denmark. In contrast, Finland, a similarly industrialized Nordic country, exhibits much lower incidences of these disorders. The reasons behind the observed trends are unexplained, but environmental endocrine disrupting chemicals (EDCs) that affect foetal testis development are probably involved. Levels of persistent chemicals in breast milk can be considered a proxy for exposure of the foetus to such agents. Therefore, we undertook a comprehensive ecological study of 121 EDCs, including the persistent compounds dioxins, polychlorinated biphenyls (PCBs), pesticides and flame retardants, and non-persistent phthalates, in 68 breast milk samples from Denmark and Finland to compare exposure of mothers to this environmental mixture of EDCs. Using sophisticated, bioinformatic tools in our analysis, we reveal, for the first time, distinct country-specific chemical signatures of EDCs with Danes having generally higher exposure than Finns to persistent bioaccumulative chemicals, whereas there was no country-specific pattern with regard to the non-persistent phthalates. Importantly, EDC levels, including some dioxins, PCBs and some pesticides (hexachlorobenzene and dieldrin) were significantly higher in Denmark than in Finland. As these classes of EDCs have been implicated in testicular cancer or in adversely affecting development of the foetal testis in humans and animals, our findings reinforce the view that environmental exposure to EDCs may explain some of the temporal and between-country differences in incidence of male reproductive disorders.

Of possible cheminformatics futures

“…In the modern society, man is exposed to a large array of environmental chemicals, inherently present in food, cosmetics, medicines, as well as pollutants present in air, water and foodstuff, among others. Although many of these chemicals are present at a low concentration (i.e., below the threshold of toxicological concern in risk assessment), their combination can potentially affect human health and explain non-inherent genetic diseases such as infertility [20], metabolic disorders [21] and lung cancer [22]. Perhaps using similar approaches to the prediction of drug-drug interactions [23], more general ''chemical-chemical interaction'' tools (here referring to their effects in living organisms, not to chemistry and physics) would be extremely valuable in risk assessment.…”

A Brief Review of the Link between Environment and Male Reproductive Health: Lessons from Studies of Testicular Germ Cell Cancer

“…In this respect it is noteworthy that people in industrialised countries are exposed to a cocktail of numerous proven or suspected EDCs [53,54,55,56,57]. Chemicals of particular concern are, in addition to some phthalates, bisphenol A and other bisphenols, also polybrominated bisphenyls, PFCs, dioxins, several phenols including alkylphenol, triclosan and benzophenone 3, and other UV filters in sunscreens.…”

Exposure Variation and Endocrine Disruption of the Male Reproductive System

“…Concentrations of 58 chemicals out of 111 differed significantly between the countries, and in 54 cases the concentration was higher in Denmark than Finland, including the six compounds with the largest difference [25]. Dioxins include several congeners, and these were also different between the countries.…”

“…Principal component analysis of chemicals in the breast milk revealed distinct exposure profiles between Denmark and Finland [25]. Concentrations of 58 chemicals out of 111 differed significantly between the countries, and in 54 cases the concentration was higher in Denmark than Finland, including the six compounds with the largest difference [25].…”

“…Although the PCBs have not been produced in large scale after the 1980s [1] and the production and circulation of PCBs, dioxins, and most PBDE congeners was planned to be stopped under the Stockholm Convention [23] due to their chemical properties, they are still present in fauna even in remote locations such as Svalbard in the Arctic Ocean [24]. In the Danish-Finnish birth cohort study, exposures were measured in breast milk collected over a 2-month period starting at 1 month after delivery [14,17,25]. After each feeding when the baby was satisfied, the mother collected some of the remaining milk in a cup that was emptied in a glass bottle that was stored in the freezer.…”