Q I am worried about the dangers of plastics. I've heard that cling film may be carcinogenic, and my daughter has been given a plastic dental brace to wear at night; could it be dangerous? - Sarah Meon, Hailsham, E. Sussex
A There are basically five kinds of plastics, all of which may be a hazard to health to some extent. The most toxic is PVC (polyvinyl chloride), a major constituent of clear plastic films. PVC is widely used in the construction industry and for packaging non-food items. However, some PVC films are used by the food industry to wrap supermarket foods and, in the home, many cling films are also made of PVC.
Although PVC has been suspected of causing cancer in workers involved in its manufacture, consumer concerns have centred on the chemical plasticisers added to PVC to make it flexible and transparent. The trouble is, plasticisers are inherently mobile molecules - and so can easily travel from the wrapping to the food.
One common plasticiser is di-(2-ethylhexyl) adipate (DEHA), found to be carcinogenic in laboratory animals, possibly because it affects the endocrine system.
But rather than banning cling films outright, UK and EU regulations have only set limits to the amount of DEHA that is allowed to 'migrate' from the films into food. In what appears to be no more than a 'guesstimate', the upper safe limit has been set at 18 parts of DEHA per million parts of food, representing a 'tolerable daily intake of 0.3 mg/kg of bodyweight' - on the face of it, a rather high figure.
Even so, a recent Danish survey found that even this limit was exceeded in many shop-bought wrapped cheeses (Food Addit Contam, 1995; 12: 245-53). A later Danish investigation discovered that as much as 60 per cent of cling films - that according to EU regulations are perfectly safe - in fact breach the officially set DEHA limits (Food Addit Contam, 1997; 14: 345-53).
It may be that some foods attract DEHA molecules more than do others. In 1987, a major US investigation of supermarket food found the highest DEHA residues in cling film-wrapped cheeses, baked goods and sandwiches, but lower amounts in cooked meats and poultry, and the lowest amounts in fruits and vegetables. Broadly speaking, the higher the food fat content, the higher the cling film contamination.
In the home, the same US investigators found even higher DEHA levels - mainly due to microwave cooking. Subsequent tests have shown that high-fat foods such as meat, cakes and scones are the most vulnerable to cling film contamination when heated. However, if the film is not in direct contact with the food during cooking, there is little or no DEHA migration.
Another potential source of DEHA is from shop-bought sandwiches - not necessarily from the sandwich packaging, but from the PVC gloves worn by the sandwich-makers. In Japan, PVC gloves have now been banned in food preparation.
Is there a safer alternative to PVC in the kitchen?
Polyethylene, a plastic film used for food freezer bags and wraps, does not contain plasticisers, and is generally considered safe for storing and microwaving.
As for your daughter's dental brace, it is probably made of polymethyl methacrylate (PMMA), a kind of acrylic. This is the most widely used plastic in dentistry, and has been around for 40 years.
PMMA uses plasticisers called 'phthalates', hormone-mimicking chemicals that, at high doses, can cause testicular and fertility problems in lab animals. To see whether phthalates were safe for humans, one report recommended that PMMA dental braces be tested on monkeys (J Prosthet Dent, 1977; 37: 74-82) - but either such experiments were never done or, if done, the results have never seen the light of day.
Meanwhile, PMMA has continued to be used in dentistry and, because it hasn't caused any obvious problems of toxicity, dental authorities conclude that it is safe.
But that's what they said about amalgam fillings.
In the view of many holistic dentists like Robert Hempleman, while not ideal, plastic is certainly the lesser of two evils. The alternative, metal, creates an electrical current in your mouth and also deposits itself in many organs of your body.