When food is exported, the food itself is not the only thing that may be regulated. Packaging that comes into contact with food—especially plastic packaging—may also need to meet safety requirements.
Two terms often encountered in this field are OML and SML.
What Are OML and SML?
OML stands for Overall Migration Limit.
It measures the total amount of substances that migrate from a plastic material into food or a food simulant under specified test conditions.
In simple terms, OML asks:
How much material comes out of the plastic altogether?
Under the European Union’s food-contact plastics rules, the general OML is 10 mg per dm² of food-contact surface.
SML stands for Specific Migration Limit.
Instead of measuring everything together, SML focuses on a particular chemical substance that may migrate from the plastic into food.
It asks:
How much of this particular substance comes out of the plastic?
Different substances can have different limits depending on their toxicological properties and permitted uses.
Why Is Migration Testing Necessary?
Plastic is not completely inert.
During storage, heating or prolonged contact with food, very small amounts of monomers, additives, stabilizers and other substances may migrate from packaging into the food.
The amount of migration can depend on factors such as:
- temperature;
- contact time;
- whether the food is acidic, fatty, alcoholic or water-based;
- the type of plastic;
- the thickness and structure of the packaging.
Because testing every real food product would be impractical, laboratories often use standardized food simulants and controlled temperature/time conditions.
The same basic scientific principle is also used in the United States, where the FDA evaluates the migration of food-contact substances into food or food simulants as part of safety assessments.
Is OML/SML a Worldwide Standard?
No.
There is no single global organization that issues one universal OML/SML certificate for all countries.
OML and SML are particularly associated with the European Union regulatory system, especially Regulation (EU) No 10/2011 for plastic materials and articles intended to come into contact with food.
Other countries and regions have their own food-contact regulations.
Japan, for example, operates its own regulatory system for food utensils, containers and packaging. It has introduced a positive-list system for synthetic resins, under which permitted substances are specified by Japanese regulations.
The United States uses the FDA’s food-contact substance framework, including Food Contact Notifications and migration/exposure assessments.
China likewise has its own GB standards for food-contact materials.
Therefore, a package that complies with EU requirements is not automatically guaranteed to comply with every country’s rules.
The Most Important Question for Exporters
For an exporter, the first question should not simply be:
Is the package made of plastic?
It should be:
Which market is this product being exported to?
The destination determines which legal standards, migration tests, permitted substances and documentation requirements apply.
This is why the same plastic packaging may require different compliance checks when exported to the EU, Japan, the United States, China or another market.
In short, OML and SML are tools for evaluating chemical migration from food-contact plastics, but they belong to specific regulatory systems rather than a single worldwide certification scheme.