Is nothing sacred?
By MICHAEL HAEDERLE, UNIVERSITY OF
NEW MEXICO HEALTH SCIENCES CENTER
Now, University of New Mexico Health Sciences researchers
have used a new analytical tool to measure the microplastics present in human
placentas.
In a study published on February 17 in the journal Toxicological Sciences, a team led by Matthew Campen,
PhD, Regents’ Professor in the UNM Department of Pharmaceutical Sciences,
reported finding microplastics in all 62 of the placenta samples tested, with
concentrations ranging from 6.5 to 790 micrograms per gram of tissue.
Health Concerns and Study Methodology
Although those numbers may seem small (a microgram is a
millionth of a gram), Campen is worried about the health effects of a steadily
rising volume of microplastics in the environment.
For toxicologists, “dose makes the poison,” he said. “If
the dose keeps going up, we start to worry. If we’re seeing effects on
placentas, then all mammalian life on this planet could be impacted. That’s not
good.”
In the study, Campen and his team, partnering with
colleagues at the Baylor College of Medicine and Oklahoma State University,
analyzed donated placenta tissue. In a process called saponification, they
chemically treated the samples to “digest” the fat and proteins into a kind of
soap.
Then, they spun each sample in an ultracentrifuge, which
left a small nugget of plastic at the bottom of a tube. Next, using a technique
called pyrolysis, they put the plastic pellet in a metal cup and heated it to
600 degrees Celsius, then captured gas emissions as different types of
plastic combusted at specific temperatures.
“The gas emission goes into a mass spectrometer and gives
you a specific fingerprint,” Campen said. “It’s really cool.”
Prevalence and Types of Plastics Found
The researchers found the most prevalent polymer in
placental tissue was polyethylene, which is used to make plastic bags and
bottles. It accounted for 54% of the total plastics. Polyvinyl chloride (better
known as PVC) and nylon each represented about 10% of the total, with the
remainder consisting of nine other polymers.
Marcus Garcia, PharmD, a postdoctoral fellow in Campen’s
lab who performed many of the experiments, said that until now, it has been
difficult to quantify how much microplastic was present in human tissue.
Typically, researchers would simply count the number of particles visible under
a microscope, even though some particles are too small to be seen.
With the new analytical method, he said, “We can take it
to that next step to be able to adequately quantify it and say, ‘This is how
many micrograms or milligrams,’ depending on the plastics that we have.”
Environmental Impact and Health Implications
Plastic use worldwide has grown exponentially since the
early 1950s, producing a metric ton of plastic waste for every person on the
planet. About a third of the plastic that has been produced is still in use,
but most of the rest has been discarded or sent to landfills, where it starts
to break down from exposure to ultraviolet radiation present in sunlight.
“That ends up in groundwater, and sometimes it
aerosolizes and ends up in our environment,” Garcia said. “We’re not only
getting it from ingestion but also through inhalation as well. It not only
affects us as humans, but all off our animals – chickens, livestock – and all
of our plants. We’re seeing it in everything.”
Campen points out that many plastics have a long
half-life – the amount of time needed for half of a sample to degrade. “So, the
half-life of some things is 300 years and the half-life of others is 50 years,
but between now and 300 years some of that plastic gets degraded,” he said.
“Those microplastics that we’re seeing in the environment are probably 40 or 50
years old.”
While microplastics are already present in our bodies, it
is unclear what health effects they might have, if any. Traditionally, plastics
have been assumed to be biologically inert, but some microplastics so small
they are measured in nanometers – a billionth of a meter – and are capable of
crossing cell membranes, he said.
Future Concerns and Research Directions
Campen said the growing concentration of microplastics in
human tissue might explain puzzling increases in some types of health problems,
such as inflammatory bowel disease and colon cancer in people under 50, as well
as declining sperm counts.
The concentration of microplastics in placentas is
particularly troubling, he said, because the tissue has only been growing for
eight months (it starts to form about a month into a pregnancy). “Other organs
of your body are accumulating over much longer periods of time.”
Campen and his colleagues are planning further research
to answer some of these questions, but in the meantime he is deeply concerned
by the growing production of plastics worldwide.
“It’s only getting worse, and the trajectory is it will
double every 10 to 15 years,” he said. “So, even if we were to stop it today,
in 2050 there will be three times as much plastic in the background as there is
now. And we’re not going to stop it today.”
Reference: “Quantitation and identification of
microplastics accumulation in human placental specimens using pyrolysis gas
chromatography mass spectrometry” by Marcus A Garcia, Rui Liu, Alex Nihart,
Eliane El Hayek, Eliseo Castillo, Enrico R Barrozo, Melissa A Suter, Barry
Bleske, Justin Scott, Kyle Forsythe, Jorge Gonzalez-Estrella, Kjersti M Aagaard
and Matthew J Campen, 17 February 2024, Toxicological Sciences.
DOI: 10.1093/toxsci/kfae021
