Time to find solutions to mineral oil contamination

17 March 2011 (Last Updated March 17th, 2011 18:30)

Food packed in recycled paperboard has got a bad press over the risk of mineral oil contamination. Nick Kernoghan, UK director of Pira International, examines the facts behind the headlines and warns the industry to take the time to find the right solutions.

Time to find solutions to mineral oil contamination

On 8 March 2011, BBC Radio and the Daily Telegraph in the UK ran stories about mineral oil contamination of food packed in recycled paperboard packaging, followed on 9 March by the Daily Mail.

By the morning of 10 March a Google search on mineral oil in recycled paper and board brought up 4,430 citations. News travels fast in the modern world.

However, news does travel somewhat slower from the scientific community to the wider world.

The evidence cited in the media coverage came from two studies undertaken by the Official Food Control Authority of the Canton of Zurich, both published in the journal European Food Research and Technology.

The first study was published in February 2010 and identified the inclusion of newsprint in recycled paper and board as the main source of the mineral oil and highlighted quite high levels of migration, as well as the conflict between meeting European recycling targets and controlling migration.

The second study was published in October 2010 and analysed 119 samples of dry food packed in paperboard boxes for migration of mineral oil. Once again mineral hydrocarbons were found in all the foods packed either without an inner plastic bag or with a polyethylene bag, with saturated hydrocarbons at concentrations of 4mg/kg-28mg/kg and aromatic hydrocarbons at concentrations from 0.7 mg/kg-6.1mg/kg depending on the food type and time in contact.

How safe are these levels?

Different hydrocarbons have different toxicological properties as illustrated by the list below:

  • Microcrystalline wax is the direct food additive E905.
  • Highly refined mineral oils may be used as plastic additives and do not have a specific migration limit in either directive 2002/72/EC or Regulation (EC) No 10/2011 which will soon replace it. However, there is a strict specification for them stating that: - they must be white mineral oils, paraffinic, derived from petroleumbased hydrocarbon feedstocks - they must have an average molecular weight not less than 480Da - they must have a viscosity at 100°C not less than 8.5cSt - the content of mineral hydrocarbons with carbon number less than 25 must not be more than 5% w/w.
  • An unofficial specific migration limit can be calculated for white mineral oils that meet the requirements of the specification outlined above based on an acceptable daily intake derived by the joint FAO / WHO Expert Committee on Food Additives in 2002. This unofficial specific migration limit is 0.6mg/kg and has been used for risk assessment purposes by both the Official Food Control Authority of the Canton of Zurich and the German BfR. However, it should be noted that this unofficial specific migration limit has not been adopted by the European Commission in the legislation for plastics.>
  • Technical grades of mineral oils which are mixtures of paraffinic and aromatic hydrocarbons. The latter class of hydrocarbons merit an unofficial specific migration limit of not detected at 0.01mg/kg unless there is toxicological evidence to support a higher limit.

It appears that it is mainly the technical grades of mineral oils that are used in newsprint and these are the main source of both the paraffinic and the aromatic hydrocarbons being found in foods packed in recycled paperboard. Other sources of mineral oils include:

  • the printing inks used on the packaging; the Official Food Control Authority of the Canton of Zurich estimated that this source accounted for about a quarter of the mineral oil contamination.
  • recycled paperboard used as secondary or tertiary packaging, probably a minor source given relatively short contact times
  • contamination during bulk shipment and processing of foods.

Toxicological information on mineral oils indicates that they bio-accumulate in the liver, heart valves and lymph nodes and cause inflammation of these organs. Additionally, there are additional concerns of potential carcinogenicity caused by the aromatic fraction.

However, these are all long-term chronic affects and people eating a balanced diet should not suffer any adverse health consequences in the short or medium term, and maybe not in the longer term unless their exposure is particularly high. Therefore there is time to develop solutions to this problem and the industry can afford to avoid knee-jerk decisions such as switching packaging to all virgin fibre.

What do the regulators say?

"Toxicological information on mineral oils indicates they bio-accumulate in the liver, heart valves and lymph nodes."

The German BfR carried out a risk assessment of mineral oil exposure in 2009.

They concluded that there is an urgent need to reduce the exposure from recycled paperboard, but did not introduce any specific legislation.

The Swiss authorities have concluded that consumers who eat a balanced and varied diet are safe.

In the UK the Food Standards Agency (FSA) has stated that it does not believe that the current data shows there to be a health risk to consumers who eat a balanced and varied diet, but the organisation is keeping the situation under review and carrying out research of its own.

Once again these opinions point to a conclusion that there is time to develop solutions to this problem.

Finding solutions

There probably will not be a universal solution that fits all cases. It will vary for different combinations of pack, food and shelf life. However, possible solutions, in no particular order, include those listed here:

  • Use an inner bag that is a barrier to mineral oil migration. This has cost implications and needs some research to determine suitable barriers to either prevent or sufficiently reduce the migration.
  • Incorporate more virgin fibre in paperboard food packaging. This does not eliminate the problem unless 100% virgin fibre is used. There are cost and environmental implications and it is potentially tremendously disruptive to the packaging supply chain if universally adopted in the short-term.
  • Improve the sourcing of recycled fibre so that newspapers do not find their way into food packaging. This would vastly reduce exposure to mineral oil, but not completely eliminate it because some cardboard is printed with mineral oil containing inks. Also there are there are practical issues in collection and sorting.

There are undoubtedly others, but the important thing is that industry is allowed the time to develop solutions.