Using talcum powder does not increase the risk of ovarian cancer, according to a major study.
Controversy has surrounded the use of the powder on women's genitals since the 1970s, after the talc mineral was discovered to be contaminated with asbestos – which is known to cause cancer.
But a review of four US studies of more than a quarter of a million women has now declared there is 'no significant association' between the powder and cancer.
Scientists praised the study, calling it 'robust' and 'very well conducted', and said it was reassuring for women worried about using talcum powder.
It comes after Johnson & Johnson was in 2018 ordered to pay £3.6billion ($4.7bn) in compensation to 22 women who won a US lawsuit in which they claimed the firm's baby powder gave them cancer.
The company also recalled 33,000 bottles of talc in the US in October 2019 because regulators found traces of asbestos in it.
Johnson & Johnson, which famously makes talc baby powder, was sued for a total of £3.6billion in 2018 by 22 women in the US who claimed the product had given the ovarian cancer. It has since won court cases against other women alleging the same thing
Krystal Kim, 53, is one of 22 women who sued Johnson & Johnson over claims using talcum powder gave them ovarian cancer
A team from the US National Institute of Environmental Health Science in North Carolina combined and analysed the results of four studies.
Some 252,745 women were enrolled in the studies between 1976 and 2009 and had their health and talcum powder use tracked for around 11 years.
More than a third of them (38 per cent) said they used the powder on their genitals.
Women have done this for decades to absorb moisture and odours, the scientists said.
The study found, among women who did use talcum powder, there were 61 cases of ovarian cancer per 100,000 women over an 11-year period.
Among women who had never used talcum powder this rate was 55 per 100,000, it found.
Although the number was higher, the rate of cancer rose only from 0.055 per cent to 0.061 per cent, which was deemed too small to be a solid link – it may have been down to chance.
WHY COULD TALCUM POWDER BE DANGEROUS?
Talcum powder is made of finely ground talc, a mineral which forms underground as a clay-like rock.
Talc is often mined from the same place as asbestos, a mineral known to cause lung disease.
While talc is used for the skin, thanks to its softness and moisture-absorbing properties, asbestos was used for insulation.
Non-contaminated talc is completely safe. But if it is tainted with asbestos, there is a risk it could be damaging to health. Tests have in the past found traces of asbestos in talcum powder products.
Asbestos is made up of six minerals that form together as tiny crystallised fibres. The minerals on their own aren't dangerous, but together they are a recognised cause of cancer.
About eight out of 10 people with mesothelioma – a type of lung cancer – have been exposed to asbestos. When asbestos fibres are breathed in, they travel to the ends of small air passages and reach the membranes of the thorax and lungs.
They can cause inflammation and scarring, damage cells’ DNA, or cause changes that result in uncontrolled cell growth.
If swallowed, these fibres can reach the abdominal lining, where they can cause mesothelioma.
Ovarian cancer is another cancer asbestos is believed to be linked to, and is at the heart of Johnson & Johnson lawsuits in which women have claimed talcum powder has given them ovarian cancer. In some cases they have won and received million-dollar payouts from the company.
It is not clear why asbestos travels to ovarian tissues.
A total of 2,168 women from both groups developed cancer during the study.
In their paper the researchers, led by Dr Kate O'Brien, wrote: 'In this analysis of pooled data from women in four US cohorts, there was not a statistically significant association between self-reported use of powder in the genital area and incident ovarian cancer.'
They admitted the study was not big enough to detect tiny changes in risk, but said it was the biggest one to have been done to date.
Cancer expert at Imperial College London, Professor Justin Stebbing, was not involved with the study but said: 'A very well conducted rigorous investigation pooled results from four studies in over 250,000 women, to show that talcum powder didn't cause ovarian cancer.
'There weren't many cases of ovarian cancer in the group so it's possible a small effect has been missed.
'But it doesn't look like talc is a carcinogen which is an important and reassuring finding, especially as they also looked at duration and frequency of use, again finding no causative effects.'
Talcum powder is created from the mineral talc, which exists naturally as a clay-like rock which has to be mined from the ground and finely ground down.
Talc, however, may be naturally contaminated with asbestos, which is also a naturally-occurring mineral which has been definitively linked to cancers of the lungs.
Johnson & Johnson has faced lawsuits over claims its products have caused cancer and has had to recall contaminated products.
The company, however, has consistently argued its product is safe and has appealed all court cases in which it has lost.
And a batch of 33,000 bottles of talc powder recalled in the US in October did not contain any traces of asbestos, the company said after commissioning independent testing.
Just last month a judge in St Louis ruled in favour of J&J when they threw out the case of a woman claiming to have developed cancer because of the product.
Statistics expert at the Open University, Professor Kevin McConway, didn't take part in the study but added: 'One thing this research clearly demonstrates is how difficult it is to tie down whether something like this is indeed a risk factor for cancer.
'Despite this being a good, competent, careful study involving over quarter of a million women, it still leaves room for doubt about the association, if there is one, between using powder in the genital area and ovarian cancer.
'What the research does establish, I’d say, is that if using talc or other powder on that part of a woman’s body does really increase the risk of ovarian cancer, the increase in risk is likely to be small.
'If I were a woman, this wouldn’t be high on my list of worries.'
The National Institute of Environmental Health Science's research was published in the Journal of the American Medical Association (JAMA).