To Örebro University

Purpose: Perfluorooctane sulfonate (PFOS) belongs to a group of chemicals called perfluoroalkyl acids that have been extensively used in various applications such as stain and oil resistant treatments for fabrics, fire-fighting foams, and insecticides. These chemicals present an environmental and health risk being present in many samples both in wildlife and humans. In this study, we investigate the effect of PFOS on fatty acid β-oxidation in developing chicken embryos.

Methods: Fertilized chicken eggs were exposed in ovo to PFOS at day 4 of incubation. On day 10, the eggs were dissected and livers were incubated in vitro with (3)H-palmitic acid for 2 h. The media were collected, and after clean up, the amount of tritiated water was measured with liquid scintillation counting to determine the rate of palmitic acid β-oxidation.

Results: PFOS was found to induce fatty acid β-oxidation at doses starting from a lowest observed effect level (LOEL) of 0.1 μg/g egg weight. Maximum induction of 77 % compared to control was seen at 0.3 μg/g.

Conclusions: The administered doses in which effects are seen are around and even lower than the levels that can be found in wild populations of birds. General population human levels are a factor of two to three times lower than the LOEL value of this study. The environmental contamination of PFOS therefore presents a possibility of effects in wild populations of birds.

Polycyclic aromatic hydrocarbons (PAHs) are widespread fused-ring contaminants formed during incomplete combustion of almost all kind of organic materials from both natural and anthropogenic sources. Some PAHs have been shown to be carcinogenic to humans, and a wide range of PAHs are found in wildlife all around the globe including avian species. The purpose of this project was to assess the effects of a standard mixture of 16 PAHs (United States Environmental Protection Agency) on the hepatic fatty acid beta-oxidation in chicken embryos (Gallus gallus domesticus) exposed in ovo. The hepatic beta-oxidation was measured using a tritium release assay with [9,10-H-3]-palmitic acid (16:0) as substrate. Treated groups were divided into groups of 0.05, 0.1, 0.3, 0.5, and 0.8 mg PAHs/kg egg weight. The hepatic beta-oxidation was reduced after exposure in ovo to the 16 PAHs mixture compared to control. The mechanisms causing reduced fatty acid oxidation in the present study are unclear, however may be due to deficient membrane structure, the functionality of enzymes controlling the rate of fatty acid entering into the mitochondria, or complex pathways connected to endocrine disruption. To the best of our knowledge, this is the first time a PAH-caused reduction of hepatic beta-oxidation of fatty acids in avian embryos has been observed. The implication of this finding on risk assessment of PAH exposure in avian wildlife remains to be determined.

Current risk assessment of PAH-contaminated soils is usually based on chemical analysis of a small number of PAHs. The use of effect-based methods for risk assessment would yield results covering more of the effect of all the chemicals in the soil. To put such effect based data into context we tested a relative approach in which effects of contaminated soil were compared to clean rural and urban soils. This concept of relative risk assessment was tested by studying the mutagenic and AhR-agonistic potency of contaminated soil and urban soil compared to farm soil from selected ecological farms. A set of 21 soil samples was collected: 11 PAH-contaminated samples (collected in collaboration with three Swedish remediation companies), 5 urban samples (collected in Swedish cities) and 5 soil samples from ecological farms. The urban and rural samples were collected at the surface (0-10 cm deep), the contaminated samples were collected from piles during remediation (100-200 cm deep). To evaluate the toxicants in the soil sample, lipophilic sample extracts were tested in two different assays; (i) the Ames Fluctuation Assay (AFA) mutant strains TA98 and TA100 of Salmonella typhimurium with and without a metabolic activation system (rat-liver homogenate S9) to determine the mutagenic potential of the soil samples and (ii) the cell mechanism-specific H4IIE-luc assay to determine the Ahreceptor (AhR) activating potency of the soil extracts. The results showed clear mutagenicity, both direct and indirect, in one of the PAH-contaminated samples and three other PAH samples also demonstrated some mutagenic activity. The extracts from urban city soil showed mutagenicity in three of the 5 samples, while none of the ecological farm samples had mutagenic extracts. The bio-TEQ values were very high for all remediated samples and elevated in one urban sample. Bio-TEQ values were low in the ecological farm extracts. These findings demonstrate that the present investigation scheme using two different bioassays to determine the mutagenic potential and the Ah receptor activating potency of soil extracts is a suitable method for testing toxic properties of soil extracts. The concept of relative risk assessment using background samples from rural and urban areas and effect based testing shows promise for further development.