Science Advocacy
Science Advocacy
You’ve probably seen the stories, juries awarding people millions of dollars because they developed cancer after years of using talcum powder. Does talc really cause cancer? Should you stop using baby powder? Is it time to panic? What the deal? Let’s talk talc.
Talc is a mineral, also called talcum, or magnesium silicate. It Is mined directly from the ground in places like Australia and France, and processed for use in many consumer products. Talc is used for a whole lot of things. It is commonly found in plastics, cosmetics, paint, rubber, and ceramics. Because it’s good at absorbing water, it is used in baby powder and in the “chalk” that keeps basketball players or rock climbers hands dry. Because of it’s high shear strength, it’s often used as a solid lubricant. It’s even approved for use as a food additive and a inactive ingredient in pharmaceutical tablets in most countries. Talc is everywhere.
The link between talc and cancer has been the subject of intense research for many years. Most of the early focus was on it’s role in causing lung cancer in people who breath it in – particularly people that work in talc mines. Several large studies have been run, and the results have been mixed – some show a link between lung cancer and working in talc mines, while others don’t. However, regardless of the outcomes, these studies are generally recognized as inconclusive because of two major confounding factors. The first is that talc generally forms under similar conditions to asbestos, and can therefore be right next to, or even mixed in with asbestos when it is mined. The other confounding factor is radon – a radioactive breakdown product of Uranium which can build up in enclosed spaces below ground (like your basement). Both asbestos and radon very clearly cause lung cancer, so it’s hard in scientific studies to tell if talc is causing cancer or if it’s just exposure to asbestos and radon that is the problem.
Most experts would agree that outside of professional talc miners, thee is no real risk of lung cancer from talc itself. However, since talc and asbestos do occur naturally together, questions do remain about the possibility of low levels of asbestos in talc causing lung cancer. Recently, a jury in New Jersey awarded $37M to a man after he claimed to have contracted mesothelioma from inhaling talc his entire life. Mesothelioma is an unusual cancer that is almost always associated with exposure to asbestos, and since requirements to make the talc in consumer products 100% asbestos free were not enacted until 1976, the jury thought it plausible that the plaintiff in this case had come down with cancer as a result of their heavy lifetime talc use.
Most of the lawsuits about talc and cancer are related to ovarian cancer. The link here was first described in 1971, when a study found that 75% of all ovarian tumors contained particles of talc. This led to a lot of research, which again has produced mixed results. Most case-controlled studies (which require women to remember how much talc they used) have shown a link between heavy talc use and ovarian cancer, but larger, more rigorous cohort studies (which follow women prospectively) have generally been negative.
In looking at the totality of the data, it’s fair to say that the jury is still out on the link between talc use and ovarian cancer. From a purely scientific standpoint, there is enough data to suggest some risk, but not enough to be certain, or to know how much risk there might be.
This is an important conversation, because based on the chemical similarities between asbestos and talc, if talc does cause cancer, it probably does so in a similar way to asbestos.
Asbestos is not your typical chemical carcinogen – like the chemicals in tobacco smoke – because it does not directly damage DNA. Instead, asbestos causes cancer because of its size and shape and the fact that your body can’t break it down. Asbestos is made up of fibers – long, thin, stringy crystals which are typically 0.1 to 10 microns long (a micron is 1 millionth of a meter). That size is a problem because it means that the asbestos fibers are short enough to be inhaled deeply into your lungs and be engulfed by macrophages, which are the cells in your lungs that clean up unwanted things you breathe in (like dust and bacteria), but too large to be effectively cleared from the lungs. Once the macrophages eat the asbestos (technically, this process is called phagocytosis), they have a problem: the enzymes they produce to degrade most things are useless against the asbestos, and the long thin fibers tend to poke out of them and kill them. Over time, this leads to a cycle of cells trying to get rid of the asbestos and dying, which causes chronic inflammation, and this chronic inflammation can eventually cause cancer. Importantly, the cancer only occurs at the site of inflammation (generally in and around your lungs).
Now talc is not a fiber, but like asbestos, it can’t be effectively degraded if it gets into your lungs in large quantities. However, that doesn’t necessarily mean that it would cause cancer. Another mineral that can be a problem if you breathe it in is sand (silica). If you breathe in enough very fine particles of sand over time it can cause silicosis (also called miner’s phthisis or grinder’s asthma). The effect on the macrophages of your lungs is similar, but the end result of inhaling very fine sand particles is not cancer – it’s fibrosis. Fibrosis occurs when your cells start producing a large amount of fibrous connective tissue, usually as the result of some local damage or inflammation. If fibrosis in your lungs is severe, they won’t inflate (and deflate) properly, and this can be fatal.
This mechanism for causing inflammation is what worries doctors and scientists when thinking about ovarian cancer. It is technically possible for small quantities of talc (when applied to the genital area) to make their way into the vagina, through the uterus, up the fallopian tubes and into the ovaries. The studies showing the presence of talc in ovarian tumors seems to prove this, and if this does happen, it seems likely that these particles of talc would cause local inflammation in the ovaries, which could, over many years, lead to cancer. Because the link here is not a strong one (the vast majority of women who use talc in this way do not get cancer), it seems likely that talc is a contributor to a women’s overall risk of ovarian cancer rather than a direct cause, though more research is needed to better understand the link.
Another reason the mechanism of asbestos’s (and potentially talc’s) effect is important is that is highlights the importance of the route of exposure to the toxicity of these minerals. We already mentioned that talc is an approved food additive, so how can it be in your food if it might cause cancer? The answer is that there is no risk of fine particles of talc in your food being absorbed into the body and making their way to the ovaries. This is not biologically possible – the talc you eat will just pass through your GI tract and be excreted in your feces. It’s only when very specifically sized particles of talc make their way into the ovaries that there could potentially be a problem. Similarly, asbestos that is molded into stable objects that do not release fibrous particles is perfectly safe, because you can’t breath it into your lungs. Asbestos in brake pads, insulation, gaskets, and many other manufactured goods are safe to be around and handle, so long as the asbestos stays in place.
It’s not clear if talc causes ovarian cancer. If you are a woman and use it lightly, it is almost certainly not going to be a problem. If you use baby powder in this way frequently, it might be a good idea to switch to corn-starch based baby powder, just to be safe.
For lung caner and mesothelioma specifically, it seems clear that there is no risk with modern asbestos-free talc products. With that said, the American Academy of Pediatrics (AAP) has recommended that parents no longer use baby powder on their young children. This is not due to cancer risk, but rather the risk that young children could breath in large quantities if the parents accidentally spilled it on them. In theory, this could lead to respiratory distress if the child breathed in enough powder. The AAP position is also informed by the fact that baby powder is unnecessary – diaper rash pastes work just as well without making a mess and risking a lung full of talc.
For the many other uses of talc, there is no identified cancer risk. Talc is perfectly safe when eaten, swallowed, or applied to the skin. Even if a definitive link between talc and ovarian cancer were established some day, talc would still be commonly, and safely, used in hundreds of products we encounter every day.
