Fumigation of food during storage and transport

Key facts about ethylene oxide, methyl bromide, phosphane and sulfuryl fluoride

Dec. 2020. Storage protection for food and feed represents an important quality parameter within the production and supply chain. In order to increase the shelf life of products during transport and storage, producers have a variety of methods at hand to protect different product groups, especially against pest and mould infestation.

One of these methods is fumigation with storage protectants such as methyl bromide, phosphane, sulfuryl fluoride or ethylene oxide. Depending on the storage protection agent, a distinction is made between different areas of application. Gases are either used for disinfestation (elimination of animal pests) in soils and warehouses, or the finished product is protected by preceding container fumigation. The containers are fumigated with the appropriate substance prior to transport to protect the valuable goods from e.g. mould infestation or pests during transport. This also prevents the international spread of pests.

However, different international regulations on the use and maximum levels pose greater challenges for importers and manufacturers. The discovery of the illegal fumigation of sesame seeds with ethylene oxide in August 2020 has made the issue more pressing from the viewpoint of residue analysis and quality assurance. A warning via the European rapid alert system triggered a wave of investigations for this parameter and the previously unknown problem ultimately led to many recalls and necessary but costly destruction of goods.

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Stock protection agents: authorisation and maximum residue limits at a glance

The following table provides an overview of the current approval situation and the associated maximum quantities of the four storage protection agents ethylene oxide, methyl bromide, phosphane and sulfuryl fluoride.

Legal regulations in the EU for the use of fumigants

Source: according to Regulation (EC) No 396/2005

Ethylene oxide
The use of ethylene oxide is prohibited in Germany. Until 1981, fumigation with ethylene oxide was a proven means of protecting food from fungi, viruses and bacteria. However, due to the highly toxic properties of ethylene oxide, as well as the conversion product 2-chloroethanol, it was banned. Ethylene oxide as such is currently classified as a probable human carcinogen. Due to its high effectiveness as a fumigant, it is nevertheless used for container fumigation in some third countries.

Methyl bromide
Bromide can generally have a natural or anthropogenic origin. The former is mainly the case in soils near the sea. For soil disinfestation, the fumigant methyl bromide was widely used because of its rapid and highly effective action. As such, methyl bromide is detectable in soil for only a short period of 10-30 days. However, the decomposition product bromide can be present in the soil as a legacy contaminant for many years. Above all, its demonstrably damaging effect on the ozone layer led to a ban on fumigation with methyl bromide in Germany with effect from 01 September 2006. In accordance with Regulation (EC) No. 1005/2009, its production, marketing and use in the European Union has been prohibited since 2010. Nevertheless, it is used outside the EU due to its good efficacy, e.g. in rice production in the respective countries. Relatively high bromide levels were also measured in Thai coriander and basil samples (coriander: 48.5 mg/kg; basil: 45.5 mg/kg). In the coming years, a downward trend in the findings in food is expected, as methyl bromide has been banned worldwide since 2015.

Phosphane and sulfuryl fluoride
Phosphane is used in two different ways within food production: As a pesticide, it is applied during production on the field, as a storage protection agent it is used during processing of the raw materials.

In contrast to the other two substances mentioned, phosphane poses a little hazard when properly fumigated. The common, approved substance volatilises quickly when used properly. With appropriate declaration and correct handling, phosphane is therefore associated with low exposure for the user.

Sulfuryl fluoride is a popular gas for use in stock protection, although it is less effective than methyl bromide for pest control. Since 2009, the approval for sulfuryl fluoride by the German Federal Office of Consumer Protection and Food Safety (BVL) has included use on dried fruit, nuts, nutshell fruit and special cereals, as well as for disinfection of empty mills and rooms.