Placing fresh fish in a plastic tray or wrapping it in cling film before storing it in the fridge or freezer is routine in many Spanish homes. But new research from IDAEA-CSIC and the University of Florence, published in Environment International, suggests the habit may be less harmless than it seems. Led by Maria Vittoria Barbieri, the study examined 49 chemicals associated with food packaging and found that fish can absorb substances from packaging during storage, including from trays and freezer bags. Transfer also continued from transparent films at temperatures as low as -18°C. After a month in the freezer, the study recorded its highest contamination levels.
How Chemicals Migrate Into Fish
Until now, most studies have focused on contaminants present in food at the point of purchase. This research tracked what happens when consumers store fish at home for days or weeks. The team analyzed 49 chemicals commonly used in food packaging, including plasticizers and bisphenols found in materials used by supermarkets and fishmongers across Spain.
Fish stored in plastic packaging contained significantly higher levels of the chemicals examined than fish that had not been in contact with plastic. The longer the fish remained in its packaging, the more contaminants were detected. Migration levels varied by fish species and packaging, and also with storage time and temperature.
Migration is a recognized feature of food-contact materials, not by itself proof that a package is unsafe. The European Commission says that substances transferring from packaging into food may affect its chemical safety and human health. Under EU rules, food-contact materials must not release substances at levels that could endanger health. Plastic packaging is subject to authorized-substance rules and migration limits assessed against intended conditions of use, including the food type and the temperature and duration of contact.
For plastics, Commission Regulation (EU) No 10/2011 sets specific migration limits for certain substances and an overall migration limit of 60 milligrams per kilogram of food, or 10 milligrams per square decimetre of contact material. These are compliance thresholds, not a guarantee that no chemical transfer occurs. The wider structure also covers food-contact materials under Regulation (EC) No 1935/2004. Good-manufacturing-practice requirements are set out in Regulation (EC) No 2023/2006.
Which Chemicals Are Most Concerning?
Not all chemicals migrate equally. The study identified DEHA, or di-(2-ethylhexyl) adipate, a plasticizer used to make plastics more flexible, as one of the most mobile substances. In some cases, particularly with fatty fish such as salmon, more than 95% of the DEHA associated with the packaging was reported to have transferred to the fish. That is a study-specific result, not a general migration rate for every film, freezer bag or fish species. Although DEHA is used as a replacement for some phthalates, its health effects remain less well established.
The study identified bisphenol A (BPA), a chemical associated with hormonal effects, as the basic contributor to potential health risk in its assessment. Fatty fish such as salmon can take up fat-soluble chemicals, while water-soluble bisphenols are more likely to migrate into leaner species such as hake. Detecting a chemical in food does not by itself establish that a consumer received a harmful dose. Risk assessment also considers exposure and toxicological evidence.
Regulation and the BPA Ban
Spain began restricting BPA in food packaging in 2022, and the European Union adopted Commission Regulation (EU) 2024/3190 on BPA and other bisphenols in food-contact materials. The EU measure strengthened the rules, amended Regulation (EU) No 10/2011 and repealed Regulation (EU) 2018/213. Manufacturers have transition periods for some packaging types, extending as far as 2028. The director of IDAEA-CSIC has called for strict enforcement and urged producers to remove BPA from packaging as soon as possible to reduce public exposure.
The regulation sets requirements for materials placed on the EU market. It is separate from the fish-storage experiment and does not show that a particular package caused illness. EU rules distinguish between detecting a chemical, compliance with applicable migration limits and evidence of a health risk.
Compostable Trays: Not Always Safer
One of the study’s most surprising findings was that compostable trays, often marketed as eco-friendly, did not perform better than conventional plastics. The highest levels of chemical migration were found in hake stored for a month in compostable packaging. These materials may require additives, including plasticizers, to achieve the necessary performance. The researchers warn that consumers have little information about the chemicals used in packaging, making informed choices at the supermarket difficult.
Freezing Doesn’t Stop Contamination
Heat has often been treated as a major driver of chemical migration from packaging to food. This study shows that transfer can also occur at -18°C. The findings point to the need to consider packaging’s intended use, including contact time and temperature, and suggest that materials used for long-term frozen storage deserve closer scrutiny. Similar questions may arise for other foods, including dairy and meat. The researchers also stress the need for more toxicological data on new additives entering the market.
How to Store Fish More Safely
Children and infants may receive a higher dose of contaminants relative to their body weight, even if they eat less fish. To minimize potential exposure, the study recommends using glass containers for home storage and considering cloth bags without plastic additives. It also advises keeping frozen storage times as short as possible. Practical steps include:
- Storing fish in glass containers instead of plastic.
- Avoiding long-term freezing, and not keeping fish in the freezer for months.
- Reducing prolonged contact with plastic packaging, including trays and cling film.
- Opting for cloth bags without plastic additives when feasible.
The less time fish spends in contact with certain packaging, the lower the potential for exposure. Consumers should follow the packaging manufacturer’s instructions on temperature and intended use, rather than assume that freezing prevents migration. The findings do not establish that all plastic packaging creates a hazardous exposure, but they suggest it is worth rethinking everyday storage habits. The findings do not call for panic.
For those interested in other hidden risks in the home, including the legal and safety issues around inflatable pools on balconies, see this analysis on what Spanish law really allows for balcony pools.
