The Health Department issued a warning over Trilucent implants, which have been on the market for four years, after receiving 74 reports of "adverse incidents". In some cases the implants ruptured, producing globules of an emulsified yoghurt-like substance causing swelling. In a few instances they have become rancid and smelt. Although all types of implant are liable to rupture, when oil leaks from the Trilucent implants it appears to react with the body, producing "biologically active substances".
About 8,000 women a year have breast implants. Experts said the number of soya-oil types was about one in six of the total. Around 70 per cent of Trilucent implants were done privately. NHS hospitals and clinics were told not to use any more and to return stocks.
The implants, introduced in 1995, were promoted by private cosmetic-surgery clinics after scares about the safety of the older, silicone gel devices. However, silicone implants have been cleared after two government inquiries and an independent review.
David Sharpe, chairman of the Breast Special Interest Group of the British Association of Plastic Surgeons, said: "It is quite worrying for patients with the implants, because they are the ones scared about silicone gel, so they are more sensitive to the issue." In cases where the oil leaked and formed the "emulsified product like yoghurt" which collected in the breast, it could cause inflammation. "It's a natural oil put in an unnatural place and it's not behaving in the way they thought it would." Jeremy Metters, deputy Government Chief Medical Officer, said all women with the implants should consult their doctor for advice but there was no need for them to take immediate action unless they experienced symptoms. "There has been no evidence of permanent injury or harm to health. However, on the precautionary principle we consider that no more of these devices should be implanted."
Dr Metters said investigations were continuing so that further advice could be given to women who already had the implants. For women who are worried, the Health Department has set up a help line, which will be open for the next three days, on 0800 004440.
The latest warning will renew fears about the safety of all breast implants, which have been the subject of multi-million lawsuits in Britain and the US.
The warning was issued by the Medical Devices Agency, which tests medical equipment. In advice to the Health Department it said investigation of women affected by rupture of the implants had found that the chemical breakdown of the oil leaking into the breast was "significantly different" from that predicted during pre-clinical testing. "This breakdown results in some biologically active substances, the toxicology of which has not been adequately evaluated."
The swelling associated with rupture of the implants could be due to local inflammatory response. "The local swelling is believed to resolve once the ruptured implant has been removed."
Vicki Allanach, adviser on women's health to the Royal College of Nursing, said: "It is an anxious time for women but this is a very small number of implants. We should not get it out of proportion."
The implants are manufactured by the Swiss company Lipomatrix. Before its purchase by Sierra Medical Technologies in November it was a subsidiary of Collagen Aesthetics International, the UK suppliers. Lipomatrix and Collagen Aesthetics issued a joint statement saying that Trilucent implants had "a very good safety profile".
David Cooper, managing director of Transform, the country's market leader in cosmetic surgery, said women who had received soya-oil implants should not panic. "Like everyone else, we are awaiting to hear from the Medical Devices Agency to see what the next step will be ... I have received assurances from the Department [of Health] that there is no reason to panic. This is a precautionary measure taken because people's health comes first."
Mr Cooper said Transform would arrange for worried clients who had received Trilucent implants to get reassurance from the surgeons who had carried out their operations. According to Transform, the demand for Trilucent implants has decreased recently as women have become less worried about the danger of silicone.
From Silicone To Soya: Types Of Implants
Silicone gel: the commonest implant, in use since 1962 but banned from cosmetic surgery after a health scare. Reprieved after two Government inquiries and an independent review.
Cohesive silicone gel: more jelly-like and slightly firmer.
Saline: filled with salt water, commonly used in the US. The shape and feel are less realistic than silicone gel and the outer case can crease or wrinkle. Deflation after a rupture - said to occur in one in 10 cases - is usually instant.
Hydrogel: sugar, starch and water in a jelly-like state, a synthetic version is available. Offers a more natural effect, but there could be "rippling". Cancer screening can be complicated.
Soya Bean Oil: a natural product in use since 1993 thought (until now) to be safe. The filling is a natural fat, which is excreted naturally if there is a rupture. Less realistic than silicone, it is "radiolucent", breast tissue is not hidden during screening.