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Migration of chemicals from plastic into food

What is the issue?

Plastic packaging plays a significant role in the shelf life and ease of storage and cooking for many foods. Plastic packaging, containers and cling films often have instructions on how to use them safely to keep the chemical migration to a minimum. However some people have expressed health concerns regarding chemicals migrating from the plastic packaging or cling film into food in contact with it.

The information below outlines different types of plastics and their uses around food, and packaging, and how to reduce the risk of chemicals from plastic migrating into food.

What plastics are commonly used in food containers or packaging?

More than 30 types of plastics have been used as packaging materials including polyethylene, polypropylene, polycarbonates and polyvinyl chlorides¹. Polyethylene and polypropylene are the most common.

Polyethylene plastic comes in high or low density. High-density polyethylene is stiff and strong and used for milk bottles, water and juice bottles, cereal box liners, margarine tubs, grocery, rubbish and retail bags but is not heat stable (i.e. it melts at a relatively low temperature). Low-density polyethylene is relatively transparent and used to make films of various sorts (including domestic/household cling film), and bread bags, freezer bags, flexible lids and squeezable food bottles.

Polyethylene terephthalate (PET or PETE) is a polyester. It is commonly used in soft drink bottles, jars and tubs, thermoformed trays and bags and snack wrappers because it is strong, heat resistant and resistant to gases and acidic foods. It can be transparent or opaque.

Polypropylene is more heat resistant, harder, denser and more transparent than polyethylene so is used for heat-resistant microwavable packaging and sauce or salad dressing bottles.

Polycarbonate is clear, heat resistant and durable and often used as a replacement for glass in items such as refillable water bottles and sterilisable baby bottles. It is also sometimes used in epoxy-based lacquers on the inside of food and drink cans to prevent the contents reacting with the metal of the can.

Polyvinyl chloride (PVC) is heavy, stiff and transparent and often used with added plasticisers such as phthalates or adipates. Common uses of PVC with plasticisers include commercial-grade cling films for over-wrap of trays in supermarkets and filled rolls at delicatessens.

What components of plastic can migrate into food?

In New Zealand, plastics in common household use are very stable if used appropriately. Most plastics in contact with food have a basic composition of high molecular weight and therefore have very low potential for migration into food.

To make plastics more useful, low molecular weight additives are used to increase flexibility, make them more ‘sticky’ (for cling film), heat stable or have anti-microbial compounds in them (for example). Small amounts of low molecular weight compounds may potentially leach into food during cooking or storage.

From plastic bottles and some cans lined with polycarbonate – tiny amounts of bisphenol A are formed when polycarbonate bottles are washed with harsh detergents or bleach (eg, sodium hypochlorite). Some food or drink cans may be lined with a lacquer to stop the food interacting with the tin. This may also release tiny amounts of bisphenol A. At high levels of exposure, bisphenol A is potentially hazardous because it mimics the female hormone estrogen.

From commercial cling films made from PVC – DEHA: diethylhexyl adipate is a food-compatible phthalate plasticiser and tiny amounts may migrate into fatty food (such as meat or cheese), especially with heating. DEHP (diethylhexyl phthalate) is another plasticiser that has been of concern because it can migrate, and for that reason it is not used in food-related products in USA. It has been used as jar or bottle seals and lid inserts of bottles, spreads and juices and may be in printing ink for labels.

Is our intake well below safety limits?

YES! In general, our intake is well below safety limits, based on New Zealand studies and comparing our use of plastics with overseas studies.

Bisphenol A – even the highest estimated dietary intake of bisphenol A in New Zealand is 0.0003mg/kg of body weight/day, well below the Tolerable Daily Intake level adopted by the European Commission of 0.05mg/kg body weight/day².

DEHA – commercial cling films are predominantly PVC, used for over-wrap of supermarket trays, filled rolls at delicatessens etc. Use of cling film by New Zealanders is thought to be similar to that of the United Kingdom, and experts from the European Union have recommended a safe level (Tolerable Daily Intake) of DEHA intake to be up to 21 mg/day for a 70 kg adult, without causing harm. Their dietary exposure is estimated to be up to 8.2 mg/day, below the safety limit. It is highly unlikely, but theoretically possible that if someone ate fatty foods such as fish or cheese wrapped in commercial cling film, each and every day of their lives, they could consume high levels of DEHA³. However most people eat a variety of foods in moderation, with different types of packaging which keeps exposure to DEHA well below the TDI.

Who ensures plastic products are safe for use around food?

Food manufacturers and sellers should ensure their products are safe and that they comply with relevant legislation. In practise, packaging suppliers will need to ensure their products are suitable for the intended use.

Are there laws around food-contact materials?

Yes. In New Zealand, there are requirements under the Food Standards Code and the Food Act 1981 that packaging must not cause food to be unsafe or tainted. The Code refers manufacturers to overseas regulations on the types of plastics permitted around food. Compliance with recognised international food standards such as those of the European Union (EU), the United States Food and Drug Administration and with Australian standards is reasonable evidence that materials are suitable for food use.

Australian standards relate to the manufacture, composition, and testing of a number of plastic materials intended for use in contact with food: (AS)2070, "Plastics Materials for Food Contact Use". It also refers to a number of polymers and certain plastic additives that can be used in packaging which comes in contact with food.

For some food-contact chemicals the code also puts limits on acceptable levels that can be present in food without causing safety concern.

There is also a New Zealand Code of Practice for Consumer Goods Packaging⁴ and an independent system for performance monitoring and handling complaints procedures.

What is NZFSA doing about chemicals from plastics that migrate into food?

With the revision of the Food Act, manufacturers and suppliers will need to show evidence that their materials in contact with food are fit for purpose, under their Food Control Plan. This might include evidence that their packaging comes from a company that meets international specifications for packaging safety so that chemical migration into food is nil, or within safety limits, and that their use of packaging is appropriate.

FSANZ is considering the need to review requirements for packaging materials which would include the potential migration of substances.

Can I reduce the migration of chemicals from plastic into food?

YES! Proper use of plastic packaging lowers chemical migration:

• follow manufacturers instructions when using household plastics such as cling films and bags

• follow recommendations for cleaning products to be used on containers, bottles and lids

• use the correct type of plastic for the role eg: only use microwave-safe plastics in the microwave

Oven bags, freezer bags and food-storage containers

• these have been designed for use with food. Follow manufacturers’ instructions

Household cling film in the microwave

• don’t let it touch the food during microwave cooking as it melts at a low temperature

• leave a corner of the dish uncovered to allow the steam to escape. This reduces the risk of the film being blown off and settling on to the food

Meat in trays and commercial wrap

• meat can be safely frozen in the tray and wrap, but thaw at a cool temperature. Migration of DEHA increases with heating in contact with a fatty food.

Re-using plastic containers

• re-use plastic containers that are food compatible, in the way the original food was presented. For example, you can freeze food in ice-cream containers but don’t heat them in the microwave – they were designed for use on cold food

• some types of plastics are not microwave proof as they melt at moderate temperatures eg, margarine containers.

Canned food

• avoid food or drink from dented food cans.

Supermarket checkout bags

• don’t heat food in supermarket checkout bags

• use the bags right-side-in so that food does not contact printing ink

• standard types of supermarket checkout bags can be used in the fridge or freezer.

Related links

• Re-use of plastic bottles

• Baby’s bottles and bisphenol A (BPA)

• The 6 Most Common Plastics & the Plastic Identification Code [Plastics New Zealand]

• Code of Practice for Consumer Goods Packaging [Packaging Council Of New Zealand]

• Introduction to packaging [Food Standards Agency, UK]

• Food contact substances [US Food and Drug Administration]

• Low-dose reproductive & developmental effects of bisphenol A [Harvard Center for Risk Analysis]

• An example of a company supplying food-grade plastic packaging [Bagbarn.com]

• Reduce or recycling of plastic packaging [New Zealand Packaging Accord]

5 June 2008

¹ Marsh, K. and Bugusu, B., 2007. Food Packaging – Roles, Materials, and Environmental issues. Journal of Food Science. Vol 72 (3). Pp R39 – R55.

² Thompson, B.M., and Grounds, P. R 2005. Bisphenol A in canned food in New Zealand: An exposure assessment. Food Additives and Contaminants 22 (1): 65 - 72.

³ Goulas, A.E., Salpea, E., Kontominas, M.G 2008. European Food Research and Technology 226 (4): 915 – 923.

⁴ Packaging Council Of New Zealand: http://www.packagingaccord.org.nz/CodeofPractice.php