## 1 Introduction  
Phthalates are esters of phthalic acid that have many applications. The most significant one is their usage as the main plasticizers in the polymer industry [1]. To improve the extensibility, elasticity and workability of the polymers they are mainly added to various plastic materials, such as polyethylene terephthalate, polyvinyl acetate, polyvinyl chloride and polyethylene [1, 2]. With the increase of the population on the planet, the need for food, including fish and seafood, constantly increases. It is expected that fish production from aquaculture could double by 2050 [3]. Although fish is considered a healthy food due to the favorable content of proteins, unsaturated fatty acids, vitamins and minerals [4], it is necessary to take care of the content of various contaminants in them. It is also known that the concentrations of certain chemical contaminants, including phthalates, can decrease or increase depending on the method of processing, packaging material, time of the storage, temperature and fat content [5]. Phthalates can be found in various foods, especially those with a high fat content [6, 7]. The major contamination of food with phthalates is due to the contact with various plastic food containers, including contact with packaging materials [8] and contamination during the food production process [9].  
According to the US EPA [10], phthalates are classified as probably carcinogenic for humans, leading to endocrine disruptors or hormonally active agents because of their ability to interfere with the endocrine system in the body. Therefore, the European Commission Regulation [11] on the registration, evaluation, authorization and restrictions of chemicals (REACH) has included DEHP, DBP and butylbenzyl phthalate (BBP) as toxic for reproduction. Some of the phthalates are restricted in the European Union [12], which regulates only the migration of some phthalates from food contact material to food but not the maximum permitted amount of phthalates in food. The values for DBP, BBP, DEHP and the sum of diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) in food contact materials are listed as 0.3 mg/kg, 30 mg/kg, 1.5 mg/kg and 9 mg/kg, respectively.  
As a continental country, Serbia produces freshwater fish species, common carp and trout mostly [13]. Carp and trout are often consumed and can be found on the market as fresh and smoked fish. Salmon is also often used as a smoked fish. Plastic packages are commonly used to store smoked fish, both during short storage at refrigerator temperatures and during longer storage at freezing temperatures. In the entire plastics industry, the production of packaging accounts for 40.1%, of which polyethylene accounts for 30% of the total production. Low-density polyethylene and high-density polyethylene types of packaging are the most common and account for 17.5% and 12.3% of the total European plastics demand [14]. Studies on the interaction between frozen fish and packaging are scarce. The importance of this investigation would be in reducing smoked fish contamination with chemical hazards and increasing the level of food safety.  
The main aim of this study was to determine the influence of the packaging material on the release of phthalate residues into the fish meat itself. This study aims to determine the effects of the time of storage and lipid content of the smoked fish samples on the levels of investigated phthalates.