Why Microplastics Are So Dangerous for Human Health

From our collaborating partner “Living on Earth,” public radio’s environmental news magazine, an interview by producer Aynsley O’Neill with 

Plastics have been widely adopted in all sorts of products from food packaging to toys to medical devices, in part because they were believed to be chemically inert—meaning they don’t easily undergo chemical reactions when in contact with other substances. 

But when it comes to microplastics, a recent study challenges that notion.

The study, published this month in the journal Nature, looked at several kinds of microplastics in a lab and found that when they came into contact with water, it essentially acted as a catalyst to create free radicals. Those are unstable molecules which in the human body are linked to inflammation and disease. Unlike larger, intact pieces of plastic, microplastics have far more surface area as compared to their volume, creating the conditions for chemical reactions to occur.

Dr. Leonardo Trasande is a pediatrician who directs the NYU Center for the Investigation of Environmental Hazards and was not part of the study. He shared his perspective on the results with us. This interview has been edited for length and clarity. 

AYNSLEY O’NEILL: When we say that plastic is considered chemically inert, what exactly does that mean, and what did this new study find to change our understanding of that?

LEONARDO TRASANDE: When plastic is inert in the notion of human physiology, it means it doesn’t do anything or interact with the human body. It goes, enters and leaves unseen essentially, from a human health perspective. What this study reveals is that plastic is not inert, particularly micro- and nanoplastics. 

The assumption was that micro-nanoplastics don’t get transformed or cause any interaction with the human body. What this study found was that inflammation, the body’s response to a variety of exposures, was increased. The inflammation in the human body is important because it underlies many different medically important conditions, particularly cardiovascular disease—but I can think of a host of others. 

To use cardiovascular disease as an analogy, we know that inflammation in the coronary arteries promotes the acceleration of plaque and ultimately, conditions like heart attack and even stroke. When we talk about oxidative stress or inflammation being increased in the human body as a result of plastic exposures, that by definition is not inert. It means that these plastics are quite biologically active. To be clear, we’re not even talking about the chemicals added to plastic materials or the chemical impurities that exist in plastic materials. This was simply focusing on one aspect of the multi-dimensional threat that’s posed by plastic to human health.

O’NEILL: Microplastics are fairly ubiquitous in the world these days, and as we were saying, they’ve already been linked to health concerns like inflammation and hormone disruption. To what extent does this research simply explain why microplastics have these effects, versus give us new health concerns to consider?

TRASANDE: If I can pick up the cardiovascular disease issue, the New England Journal of Medicine a couple years back published a study looking at the carotid artery, which is the artery that provides large amounts of blood flow to the brain, head and neck. What it found was that polyvinyl and polyethylene micro-nanoplastics, the levels in those carotid arteries—these are patients who underwent a procedure called endarterectomy to essentially clean out the carotid artery—the microplastic concentrations in those plaques were associated with a fourfold increase in the composite of heart attack, stroke and death. 

So what this study does is further unravels a mechanism that may directly explain why those microplastics were associated with such a steep increase in a major human health condition.

O’NEILL: What, if anything, does this study tell us about why microplastics are acting differently than their macro counterparts?

TRASANDE: Microplastics may do one of two things: they may deliver chemicals of concern to human tissue, or they themselves can be human wrecking balls, or otherwise cause inflammation by just their interaction and physical properties. This study suggests a little bit more that the latter is the case, but it doesn’t preclude the fact that chemicals that are coming along for the ride may further exacerbate the inflammation that was observed in relationship to micro-nanoplastics.

O’NEILL: We’ve talked about a few of the health concerns here. Which one stands out to you?

TRASANDE: Well, oxidative stress and inflammation is such a common thread throughout so many human health conditions that it’s hard to pick any one. Let’s even take hormone disruption, for example. Inflammation can further contribute to endocrine disruption. Inflammation can contribute to immune dysfunction. I can go condition by condition across the lifespan, and this study indirectly reveals a link that hadn’t been previously described. 

It’s not to say that microplastics are the cause of everything and anything under the sun, or not the totality of chronic disease. I’m still always going to say that diet and physical activity are important risk factors for obesity and cardiovascular disease, just to name those two. But this study adds further basis for considering a third leg to that stool, and those are environmental exposures that may be impactful.

O’NEILL: We’re throwing around some pretty concerning health conditions here. What can people do to reduce their exposure to microplastics?

TRASANDE: There are safe and simple steps that we can all take to reduce our plastic exposure. We can use more glass and stainless steel. For example, if I’m getting on a plane, I’ll bring an empty water bottle, clear security and fill that water bottle out on the other end. We can avoid microwaving or machine dish-washing plastics. We can use more fresh fruits and vegetables and cook our food at home and bring it into the workplace. We can avoid nonstick cookware and use cast iron or stainless steel. 

And we need to be the force of consumers that drives the change that we seek. That’s a very powerful thing. We forget back about 15 years ago when BPA baby bottles and sippy cups were the source of outrage among many moms. It was not science that drove the action to get BPA banned by the FDA. It was consumer activism that led the industry to run to the FDA and insist on getting that out in the first place. We forget the power of the consumer in driving the change, both at a company level but also at a public policy level.

O’NEILL: I do want to talk a little bit about public policy. What can you tell us about where U.S. regulation on plastic stands?

TRASANDE: The United States uses a lot of plastic in its day-to-day manufacturing. So do many industrialized countries. I wouldn’t say that our plastic production per unit capita is particularly outlandish. It’s been accelerated by the modern lifestyle, but that doesn’t mean we don’t have the responsibility to be the proverbial change we seek. 

The Make America Healthy Again movement has sparked further conversations about microplastic and nanoplastic, as well as chemicals in plastic materials. There have been efforts to increase federal investment in research to understand the effects of micro-nanoplastic. This study is just an early stage, but an important step in the right direction to know where microplastics are going in the body and ultimately doing harm. But we’ve had 50 years of evidence that plastic chemicals, particularly, hack our hormones, our signaling molecules that underlie so many basic biological functions like temperature, metabolism, salt, sugar and even sex. 

We know that plastic chemicals cost the U.S. economy $250 billion in disease burden. That’s 1.2 percent of our gross domestic product out the window. The reality is that we’ve misbalanced our priorities. Adam Smith, the father of modern economics, would be rolling over in his grave because this is creating externalities, harms that we bear, even though we did not buy or sell the material involved in many cases. The way to regulate our economy and put it back in the more optimal line is through actions to reduce exposure to plastic, and that can come through individual action as well as regulatory action.