What are microplastics doing to human health? Scientists work to connect the dots
Plastic serves as a building block for our food packag‐ ing, water pipes, rubber tires and synthetic fabrics. But plastic also litters wa‐ terways, soil and air so hu‐ mans and other animals wind up taking in tiny ver‐ sions with unknown conse‐ quences.
People unknowingly in‐ gest microplastics from what we eat, drink and breathe. Some scientists fear expo‐ sure to microplastics could increase vulnerability to heart disease, cancer and other illnesses. They're work‐ ing to connect the dots be‐ tween microplastics and any health hazards.
At this week's United Na‐ tions' global treaty on plastic pollution in Ottawa, dele‐ gates are working toward a treaty to address plastics from production to use and disposal.
Dr. Leonardo Trasande di‐ rects the NYU Langone Cen‐ ter for the Investigation of Environmental Hazards and is attending the meeting in Ottawa. Trasande became in‐ terested in the hormone hacking or endocrine disrupt‐ ing properties of plastics when he was resident in pe‐ diatrics and seeing patients with diabetes.
"Microplastics are in many ways a harbinger of the much bigger problem," Trasande said.
While possible links be‐ tween microplastics and ill‐ nesses like Type 2 diabetes are not definitive, re‐ searchers are exploring some concerning hints.
What are microplastics?
Most plastics aren't recy‐ cled and last for decades. When something made of plastic does break down, it fragments into small bits known as microplastics that can pollute and build up in the environment and leach chemicals.
Scientists categorize de‐ graded plastic waste produc‐ ts by size. Microplastics are tiny particles less than than five millimetres in diameter, or about the size of a sesame seed.
Nanoplastics are flecks too small to be noticed by the human eye with diame‐ ters of less than a billionth of a meter or a nanometer. By comparison, a sphere with a diameter of one nanometre is as small relative to a soft‐ ball as a softball is to the Earth.
Sources of microplastics range from the microbeads used in cosmetic and person‐ al care products to lentilsized plastic pellets also known as nurdles.
Plastic production is on track to triple by 2060, ac‐ cording to the Organisation for Economic Co-operation and Development, unless the treaty sets production limits, as some have proposed.
Microplastics and heart damage
Last month, researchers writing in the New England Journal of Medicine using special microscopy tech‐ niques found microplastic and nanoplastic chemicals in the plaque lining arteries.
In the observational study of more than 250 patients who were having tests for carotid artery disease, find‐ ing polyethylene in their plaque was associated with heart problems compared with those without having any plastics detected. This type of study can't show whether the tiny plastics caused the heart problems, just associations.
"We've done studies docu‐ menting that 50,000 Ameri‐ cans die each year from heart disease due to phtha‐ lates, for example, which is frighteningly consistent with the findings of microplastics and linkages to coronary artery disease," Trasande said.
The microplastics go along for the ride, transmit‐ ting chemicals that have been found in the urine of people and linked to a variety of diseases, he noted.
WATCH | Ending plastic pollution:
We're only beginning to see the tip of the iceberg when it comes to the health effects of microplastics, said Dick Vethaak, an emeritus professor of ecotoxicology at VU University Amsterdam who started and co-leads the Dutch Momentum Consor‐ tium on Microplastics and Health.
Recent studies report finding microplastics and nanoplastics (MNP) in blood as well as in the liver, kidney, placenta and arteries.
"This makes me conclude that MNPs will likely affect our health," Vethaak said in an email. "However, the ex‐ tent of that impact is still un‐ known."
Researchers say to uncov‐ er the answers they need to answer several questions, in‐ cluding:
How much plastic is in the body? Where does the plastic go? Do the plastic particles trigger or connect to respon‐ ses leading to serious dis‐ eases?
Part of the challenge to finding answers is that the studies have mostly been done on cells or animals like mice, which often don't equate to human health im‐ pacts in medical research. Complicating matters, mi‐ croplastics also move and build up in the body, which could unknowingly be con‐ tributing to chronic illnesses.
Factors like diet could also affect their human health im‐ pacts.
Population studies needed
Plastics range in shape from spheres to fibres, with chemical compositions that include a wide array of com‐ pounds.
Vethaak said that's why scientists need reference models and analytical tools to reflect degraded mi‐ croplastics in the environ‐ ment, rather than the virgin plastics from petrochemicals that have been studied so far.
Vethaak notes many dis‐ eases affecting the gastroin‐ testinal tract, immune sys‐ tem, cardiovascular system, brain and reproductive or‐ gans in recent decades aren't fully explained. But the ob‐ servational studies can't show whether microplastics and nanoplastics caused a condition or exacerbated it.
In one study from 2000, post-mortems on 29 patients with knee or hip replacement implants found mostly low levels of polyethylene nanoparticles in lymph nodes or organs.
To shed light on the health impacts of microplas‐ tics more conclusively, scien‐ tists aim to do experiments such as removing all sources of plastics from a family's household to check for the effects. Following popula‐ tions of people over longer periods would also help.
Trasande calls for people to take a broader perspective on plastic pollution, including microplastics and nanoplas‐ tics.
"We need to reduce plas‐ tic production because that will drive chemical exposures like we found in plastics and in people and that contribute to disease and disability across the lifespan and cost society substantially."
The talks wrap on Mon‐ day. The final meeting aiming for a global treaty on plastic pollution is scheduled for the fall in South Korea.