Abstract
Perfluoroalkyl acids (PFAAs) are ubiquitous environmental contaminants and eggs and nestlings of raptors and fish-eating birds often contain high levels of PFAAs. We studied developmental effects of a mixture of ten PFAAs by exposing chicken embryos to 0.5 or 3 μg/g egg of each compound in the mixture. Histological changes of the thyroid gland were noted at both doses and increased expression of mRNA coding for type III deiodinase was found at 0.5 μg/g egg. Serum concentrations of the free fraction of thyroid hormones (T3 and T4) were reduced by the PFAA mixture at 3 µg/g egg, which is in line with a decreased synthesis and increased turnover of thyroid hormones as indicated by our histological findings and the decreased mRNA expression of type III deiodinase. The relative weight of the bursa of Fabricius increased at a dose of 3 μg/g egg in females. The bursa is the site of B-cell development in birds and is crucial for the avian adaptive immune system. Analysis of plasma and liver concentrations of the mixture components showed differences depending on chain length and functional group. Our results highlight the vulnerability of the thyroid hormone and immune systems to PFAAs.
Highlights
The perfluoroalkyl acids (PFAAs) comprise a large group of synthetic environmental contaminants that raise great concern regarding possible adverse health effects in humans and wildlife
Mortality was low in all groups; 2/21 (10%) in the control, 1/21 (5%) in the group exposed to 0.5 μg Perfluoroalkyl acids (PFAAs)/g egg and 1/20 (5%) in the group exposed to 3 μg PFAA/g egg
The mean bursa-somatic index was 18% higher in the group exposed to 0.5 μg PFAA/g egg and 30% higher in the group exposed to 3 μg PFAA/g egg compared to the control
Summary
The perfluoroalkyl acids (PFAAs) comprise a large group of synthetic environmental contaminants that raise great concern regarding possible adverse health effects in humans and wildlife. PFOS is since 2009 regulated globally under the Stockholm convention on Persistent Organic Pollutants (POPs), and PFOA and perfluorohexanesulfonic acid (PFHxS) are currently under review for listing. Levels of these PFAAs are still high and some of the other long-chain PFAAs continue to show increasing concentrations in humans and wildlife[12,13,14]. A few PFAAs have been studied in avian models and there are indications that some of them, e.g. PFOA, PFOS and PFHxS, induce various developmental effects including cardiotoxicity, altered fatty acid metabolism, thyroid hormone disruption and immunotoxicity[27,28,29,30]
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