Chemical Exposure & Breast Cancer

You may have seen recent headlines saying something like, “More than 900 widely used chemicals may increase breast cancer risk.” There’s a lot to unpack here, so we’re going to explain the study, what it means for you, and what steps you can take to reduce your risk of breast cancer.

Let’s start with the headlines. When we read the study, the authors said that they found 216 chemicals – that’s a large number but a far cry from the 900 some articles are claiming1. Let’s take another step back and look at the source of that list of chemicals. A word of warning: we’ll be talking a little bit about the process of conducting animal studies, so if you are sensitive to the topic, skip the next two paragraphs. The important takeaway is that just because a chemical causes cancer in rodents doesn’t mean a human will develop cancer from that chemical.

The researchers found these chemicals by examining studies featuring chemicals that caused mammary gland tumors in rodent studies, not human studies. Human studies are really expensive and complicated to do, so most research on potential human carcinogens starts with animals, and then potentially, there will be a human study down the line. Some other reasons they start with rodents are that their mammary tissue is similar to that of humans, and it’s also really easy to give a rat or a mouse cancer. Generally, the smaller the mammal, the more likely they are to develop cancer. Rats and mice develop cancer very easily, but an elephant, for example, is much less likely to develop cancer than a human is2

When conducting these rodent studies, the animals are exposed to a far greater amount of a chemical in a short period of time than a human would necessarily be exposed to during the course of their life. This cranks the toxicity of the chemical up to 11, which helps illustrate if there is any possibility at all for the chemical to cause cancer. All known human carcinogens are carcinogens in rats and mice; however, not everything that causes cancer in a rodent causes cancer in humans as well. Therefore, rodent models can give us an idea of chemicals that may cause cancer in humans, but a rat developing cancer from a chemical does not mean that you will, too. 

Fortunately, scientists know all of this (unfortunately, most journalists don’t), so they have a threshold of when they start to get concerned about a chemical’s risk to humans. If the number of cancers developed in rodents equates to a 1 in 100,000 risk of developing cancer in the human population, they start to get nervous. 

So, what does all of this mean for you? Well, very little yet. Right now, for most of these chemicals, all we have is a warning sign that there could be a problem. We have no idea how these findings in animals will translate to the human population. For example, will daily application of your favorite foundation, which happens to have one of these chemicals in it, be enough to increase the risk of breast cancer, or would you have to wear a whole bottle of it every day? Will eating microwaveable meals a few times a week increase your risk for breast cancer, or would you have to actually eat the plastic packaging to increase risk? Are these chemicals mountains or molehills? We don’t know the answers to these questions.

What do you do with this ambiguous information? Whatever makes you comfortable. There is not enough evidence available for the majority of these chemicals for us to tell you to throw everything out, but if you want to limit your exposure to some of these chemicals, there are a few things to do. What will be the most effective but, unfortunately, most challenging way to limit exposure would be to advocate for increased funding for studying these chemicals and increased regulation on corporations to have them reduce or eliminate the use of these chemicals. 

Individual choices only go so far when it comes to systemic exposure, but you can still make personal choices to reduce exposure. Many of these suspected chemicals are present in stain-resistant fabrics, house cleaning products, and products like shampoo and makeup. The Campaign for Safe Cosmetics has a great guide for personal care products3. They rank potentially harmful chemicals by their risk and break them into categories based on where you are likely to find them, such as in anti-aging products or sunscreens. 

We recognize that replacing many of your products is expensive and inconvenient, so we aren’t suggesting that. Some tips we got from a presentation on The Campaign for Safe Cosmetics include:

  • You don’t have to throw out your favorite products.
  • Ingredients are listed by proportion in the product. If potentially harmful chemical A is in the first five ingredients listed on the product, try not to use any other products with chemical A as an ingredient.
  • It’s all about reducing exposure. You might reduce exposure by 5% by switching a product, but that still helps to reduce your potential risk.

Breast cancer doesn’t just have one cause but is most often a result of the interaction between your genes, your behaviors, and your environment. We never know what element in that equation will have the most impact on the individual, but if you are actively trying to reduce your risk of breast cancer in ways that you can control, it doesn’t hurt to take a look at the products you buy for your skin, your hair, and your home.

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