The present study was aimed at evaluating fluorine contamination of the eggs of free-ranging laying hens in Northern Poland, in the Central Pomerania region, in relation to the distance from the emission sources. Fluorine levels in the soil, feed, and the shells, and contents of the eggs were assayed with the potentiometric method using an ion-selective electrode from ORION Ion Meter. The sampled eggs were subjected to pressure microwave digestion with the use of a Milestone MLS-1200 microwave. All the samples were digested in 5 ml of supra-pure grade concentrated HNO3 from Merck. The mean level of fluorine in the studied soils ranged from 3.79 mg kg-1 of DM in typical river alluvial soil to 126.19 mg kg-1 of DM in lessive soil. The study revealed an average fluorine content in the feeds administered to the hens on the farms in zone 1 (17.29 mg kg-1 of DM), it being 3.5 times higher than the corresponding content in zone 2 (4.92 mg kg-1 of DM). A statistically significantly higher mean fluorine level was identified in the eggshells of hens on zone 1 farms, located closer to the pollution emission sources (17.52 mg kg-1 of DM), the value being more than 3-fold higher than that in zone 2 (5.47 mg kg-1 of DM). The present study revealed an almost twice as high fluorine mean content in the hen eggs collected on farms in zone 1 (1.488 mg kg-1 of DM) compared with the hen egg contents in the experimental zone 2 (0.640 mg kg-1 of DM), the difference being statistically significant.
Keywords: Egg contents; Eggshell; Fluorine contamination; Plant; Soil type.