## Materials and Methods  
### Sample Collection  
Data about the content of HIM in fish products were obtained from official control analyses performed on 474 batches (3130 determinations) of imported and national fish products collected in Puglia and Basilicata (Italy) in the years 2015-2019. Generally, each batch was collected by the technicians of the local Health Service and border control authorities in nine sample units, as indicated in the Commission Regulation (EC) 2073/2005 [15]. However, in specific cases (suspected poisoning episode or sampling in the retail market) only a sample unit was taken. The samples were subdivided into three categories: 294 (62%) fresh/frozen and defrosted products--yellowfin tuna (_Thunus albacares_, [PERSON] 1788), skipjack tuna (_Katsuwonus pelamis_, [PERSON] 1758), bluefin tuna (_Thunus thynnus_, [PERSON], 1758), anchovies (_Engraulis encrasicolus_, [PERSON], 1758), mackerel (_Somber scombrus_, [PERSON], 1758), sardines (_Sardina pilchardus_, [PERSON] 1792), herring (_Clupea harengus_, [PERSON], 1758), other kind of fish as swordfish (_Xiphias gladius [PERSON], 1758), salmon (_Salmo salar_, [PERSON], 1758), and other species as gadidae and cephalopods; 119 (25%) cannot products (mainly tuna and mackerel), and 61 (13%) ripened products (mainly anchovies and sardines). Canned tuna samples--made with skipjack tuna or yellowfin tuna--and canned mackerel samples, in water or in oil, were stored at room temperature until analysis. The majority of tuna samples were in 80 g cans while mackerel samples were in 125 g cans. The only non-compliant sample among the canned products was commercialized in a 2500 g can. The fresh fish samples were brought to the laboratory in cold storage conditions and stored at -20 \({}^{\circ}\)C until analysis. The dietary exposure estimates are usually derived from the minimum, mean and maximum residue levels found in each category of product monitored. These levels, combined with representative data about food consumption, generate three different exposure scenarios (low, average and high) that represent the likely exposure across a population [22]. During the survey, different samples with high HIM concentrations (up to 5542 mg kg\({}^{-1}\)) were registered. Obviously, these high concentrations are responsible for acute poisoning and the risk assessment under high exposure scenario loses its sense. Consequently, the risk assessment was developed taking into account the average exposure scenario. Moreover, in order to give a more significant contribution to the evaluation, the HIM concentrations detected during monitoring were subdivided into 6 ranges (C \(\leq\) 2.5 mg kg\({}^{-1}\), 2.5 mg kg\({}^{-1}\) \(<\) C \(\leq\) 10 mg kg\({}^{-1}\), 10 mg kg\({}^{-1}\)\(<\) C \(\leq\) 50 mg kg\({}^{-1}\), 50 mg kg\({}^{-1}\)\(<\) C \(\leq\) 100 mg kg\({}^{-1}\), 100 mg kg\({}^{-1}\)\(<\) C \(\leq\) 200 mg kg\({}^{-1}\), C \(>\) 200 mg kg\({}^{-1}\)) and the risk assessment was also developed taking into account the mean concentration registered in the range with the highest amount of data (most likely scenario). All samples monitored during this survey were commercialized in Italy. So, the reference data about fish consumption were obtained from the INRAN-SCAI 2005-06 [23; 24; 25], which provides the mean consumption of the Italian population relating to the following categories of seafood: fresh and frozen, preserved (canned and ripened fish) and overall. For each category, data on 5 subgroups of the population were available: infants (0-2 a), children (3-9 a), adolescents (10-17 a), adults (18-64 a), the elderly (65-97 a). Among these 5 subgroups, only the last 4 were taken into account for risk assessment, since the estimations relating to the first one (infants) was not representative (\(n<30\)) [26]. The risk assessment was elaborated using data related to the whole population and to the seafood consumers, since the reference document supplied this type of information.