Can tattoos cause cancer?

A new study from researchers in Sweden - which suggests a possible link between tattoo ink and cancer. Here’s Christel Nielsen at Lund University…

Christel - One in two women younger than 40 years old have a tattoo. And yet we know so little about how that affects health. During recent years, there has been some work that has looked into the fate of tattooing in the human body. The tattoo ink is actually moved away from the skin and ends up in the lymph nodes, part of the body's natural immune system. We know that many of the chemicals in the ink are bad actors, yet that sort of linkage between the two hadn't been made. We thought that that would be a logical first step to take: to ask whether having this deposition, this translocation of tattoo ink within your immune system, would that cause cancer given what we know is in the colours?

Chris - Are there adequate records, though, of who's got tattoos and who's having outcomes with cancer? Because that's not something that doctors routinely say to a patient when they come in, 'Oh, how many tattoos have you got?' So how did you actually collect the data?

Christel - Yeah, that's a really good question. I think that is something that's been a limiting factor. What we did is that we used the registered data that we have in Sweden, on the whole population, on everyone who lives here, and a very useful register for research is the Swedish National Cancer Registry. Everyone who receives a cancer diagnosis ends up in that registry. What we could do was retrieve data on everyone who had had a diagnosis of cancer of the immune system during the last 10 years, and then we were able to link that to data from the total population to get individuals who had not had cancer during the same period of time. Then we went out there, using a questionnaire, and asked all these people about their tattoos, their lifestyle, other things you might do to your body, like use of tanning beds, piercings, scarification, smoking. The idea was that, by doing this, we would find out whether there was an overrepresentation of tattoos among those who later developed cancer of their immune system.

Chris - And is there?

Christel - The data suggested that we had a 20% higher risk among those who were tattooed.

Chris - Have you quantified how much body art people have? Because one of the arguments about causation, if something causes something to happen, there should be what we call a dose dependent relationship. If I smoke one cigarette, then that's far less bad than if I smoke 10, let's say. One would anticipate, if I was covered in tattoos, I ought to have a higher risk of getting one of these lymphomas that you've discovered this association with than if I had very few.

Christel - We have that data, but we didn't see that effect. We also expected it to be that way. We have discussed it a lot: what does this data represent? What does this mean? It could be that we asked the wrong question, basically. We distinguished between people who had a tattooed body surface of one hand palm or smaller or larger than that. We thought we would capture a dose effect that way. We don't know what happens in the body. We basically just looked at the first destination in the body where the ink ends up and I would speculate that the lymph nodes can only keep so much ink and there might be some kind of saturation effect that the rest of the ink passes on.

Chris - Could it be that the tattoo is an innocent bystander, but it's a reflection on a certain person's other lifestyle practices. So if they've got a tattoo, they might do something else and it's something else they do as well that's actually linked to the lymphoma, not the tattoo per se.

Christel - That is a very important point. But we collected data on those factors. We sat down and thought through thoroughly what factors may be related to getting lymphoma, and do we think that these factors may also be related to whether you have tattoos or not. If there was a 'yes,' or a 'perhaps yes,' then we made sure that we collected data on that. So, for instance, tattooed individuals are more frequent smokers. We also considered socioeconomic status, education, age of course.

Chris - And when you control for those various factors, do you still see this signal that it appears that there is some kind of association, having a tattoo, with this 20% increase in your overall risk of getting a lymphoma at some point? How does this make you feel about your own tattoo?

Christel - It's not more dangerous today than it was yesterday. There is no reason for people to be alarmed about this, but we have all gotten our tattoos for some reason. They are an important statement for some life event that you go through and I think that might have a psychological value for many people that shouldn't be underestimated. We are constantly exposed to different things in our everyday life and I think it's the sum of those exposures that add up to create your actual risk.