Extreme Heat May Increase Microplastic Exposure, Related Health Concerns: Eva R. Parker, MD

Although the dog days of summer are drawing to a close, extreme heat will persist across many parts of the US. Along with prolonged UV exposure, this heat may accelerate the breakdown of larger plastics into microscopic particles commonly known as microplastics, according to Eva R. Parker, MD, assistant professor of dermatology at Vanderbilt University Medical Center, who has a background in environmental science.

In an interview with The American Journal of Managed Care^® (AJMC^®), Parker discussed how extreme heat may increase microplastic exposure, how these particles enter the body, and their potential effects on internal and skin health. She also addressed gaps in current research and regulatory approaches, as well as practical steps people can take to reduce exposure.

This transcript has been lightly edited for clarity.

AJMC: What impact does extreme heat have on plastics, and how can it increase opportunities for microplastic exposure?

Parker: We know that microplastics can be shed as fine particles from everyday items that we use, from our tires to our clothing, and release pollution. But we also know another source of microplastics is macroplastics, large pieces of plastic that get degraded over time and weathered into small microscopic pieces. We know that temperature plays a big role, so the hotter it is, the more likely those high temperatures are to break down larger pieces of plastic into the tiny, microscopic pieces that we call microplastics.

AJMC: As temperatures continue to rise during the summer months, what are the biggest sources of microplastics exposure that people may not realize?

Parker: I think the scary thing about microplastics is we can't see them, and so they really are ubiquitous; they're everywhere. They're in the soil and water, they're in the air, and they're in our houses and in the dust in our homes. I think that trying to avoid microplastics is virtually impossible, but what we do know is that the more we pollute the planet with plastics, the greater our exposure.

With heat specifically, it’s really a double-edged sword, if you will. We are seeing that microplastics are actually contributing to warming and maybe playing a role in climate change and heat waves. All of the microscopic plastics that are released into the air that are dark in color are actually absorbing heat and hanging on to that. Several recent studies have demonstrated this, including one that was published a few months back in Nature Climate. The scary thing about that is that the microplastic pollution that we're releasing globally in 1 year warms the planet as much as 200 coal-fired power plants do. It's a tremendous amount of heat retention that plastics are causing in the atmosphere.

Additionally, we know that when it's hot outside, we may potentially have more exposure to microplastics through our skin and other sources and that the plastics, as they degrade with heat, may release more toxic chemicals into the environment.

AJMC: What do we currently know about how microplastics enter, move through, and potentially accumulate in the body?

Parker: There are 3 primary sources of entry into our body. The first is inhalation. If there are microplastics aerosolized in the air, we can inhale them, and they can embed in our lungs. Microplastics are sort of sticky, and so a lot of things can glom onto microplastics; other pollutants, toxins, heavy metals, and even microorganisms like bacteria and fungi can be on microplastics. From the lungs, microplastics can enter the bloodstream.

A second most common source is probably ingestion, so microplastics that contaminate our food. Then, the third is absorption through the skin through our follicular and sweat gland openings.

AJMC: Based on the available evidence, what are the potential health effects of microplastics?

Parker: I think it's a nascent area, and we're still learning a lot. What we know so far is that microplastics may be playing a role in things like atherosclerosis. I remember when it was discovered that a plaque in someone's carotid artery actually had microplastics in it, which is really frightening. We also see microplastics in most major organ systems, including our reproductive organ systems. Microplastics have been found in semen, sperm, and placentas, so we know even unborn children may be getting exposed in utero to microplastics.

What does that all mean? Just because it's in our body doesn't necessarily mean that it's bad, but all evidence points to detrimental health effects, and that can range from cardiovascular disease to endocrine disruption, which is probably one of the areas most studied. We're seeing that microplastics may be playing a role in small-growth babies and disrupting fetal development.

For skin, we're learning that microplastics may be playing a role in some of our hormonally driven processes, like hidradenitis suppurativa and acne. Also, there's concern that microplastics are carcinogenic. While there's evidence for some organ systems, in our skin, in particular, there's less evidence but some concern that it may be playing a role in skin cancers as well.

AJMC: What further research is needed to better understand the impact of microplastics on human health, both overall and on the skin?

Parker: I think just continued research looking at links between microplastic exposure and human disease in all organ systems. We're finding it in almost every organ in our bodies, and likely there are impacts on those systems, and there may be synergistic impacts on multiple systems. For example, you may have cardiovascular and endocrine effects that together work to enhance disease processes in your body. I think that's really the largest area: the need for organ-specific research that demonstrates causality; that's one piece that we have been missing a lot of. We’re finding microplastics in the body, but we don't have as much research showing that that's actually causing disease, and so we really need to have those causal studies that implicate microplastics in disease.

That doesn't help us necessarily avoid the detrimental effects because microplastics are so invisible in our environments and they're so ubiquitous. Right now, there's no way to get those out of our body, and so I think another area of research is, okay, microplastics are in our body; now, what do we do about it? I don't think anyone knows how to get rid of these from our body. I think most of the research has been on removing them from the environment; how do we filter our water, treat our soil, and improve our air quality so that we're not ingesting or inhaling these microplastics? But once they're in our bodies, what do we do? Research has not answered that question yet.

AJMC: In the meantime, what steps can people take to reduce unnecessary microplastic exposure?

Parker: First of all, don't panic. Don't go through your house and throw out every piece of plastic. Plastic serves an important role in our lives and has certainly modernized our ability to store and transport many things, including food and medications. I don't want to demonize plastic, and we're not going to be able to get rid of it all. But some of the biggest sources are plastics that enter our food when we cook and prepare it, so not microwaving food in plastic containers is a really simple thing.

Slowly substituting plastic storage containers for glass or other more ecologically friendly vessels and containers is one really easy option. Slowly get rid of your plastic utensils and replace them with wood, stainless steel, or silicone that aren't going to release plastics. Then, of course, the coating on a lot of nonstick pans is also potentially a source of harm, with not only forever chemicals but also potentially microplastics, and so replace pans that are coated with that with healthier options. Those are just a few things. That costs money, and that takes time, so I think everyone has to just take baby steps to do this.

Other things are when you're in the grocery store buying food, try to buy things in glass jars or alternative containers, and try to also minimize plastic purchases in your food in general. There are many brands where if it's a microwave dinner, it's in a cardboard dish or tray, not a plastic tray. Just making choices, intentional choices, with purchasing, I think, is really important. With skincare, look for containers that have less plastic, reusable containers, and look for glass, cardboard, or other options for skincare products rather than having everything be plastic-based. Again, it's just informed choices.

Lastly, I think recycling is really important. If we're using plastics, the last thing we want to do is throw them in the trash and have them become part of the pollution that is contributing to health effects. I would urge everyone to try to recycle their plastics and be judicious in what they can use or repurpose.