As the world’s understanding of the plastics crisis grows, new facets of the problem emerge and reveal impacts on human health and the environment. Recent advances in science are allowing scientists to explore how micro- and nanoplastics form a critical piece of the plastic pollution problem. First thought to be mainly a marine pollution issue, over the last decade, scientists have discovered micro- and nanoplastics exist in every environmental compartment — from freshwater to soil and air — and in thousands of species, including humans.[1] But like climate change and hazardous chemicals, most plastics are invisible to the naked human eye, meaning their impact goes relatively unseen.[2]
Contrary to popular depictions, oceans are not “the final sink”[3] for
microplastics. These tiny plastic particles can travel worldwide, ending up in
urban, rural, and remote areas. They take an even faster transport
pathway than oceanic currents: the atmosphere.[4] Moving
through the air, micro- and nanoplastics can cover thousands of kilometers in a
matter of days to weeks, creating what could be a “never-ending loop”
of plastic transport.[5] The
serious potential for long-range transport means that micro- and nanoplastics
can affect locations and populations vast distances from the sources of plastic
pollution, making microplastics “one of the most ubiquitous pollutants released
by anthropogenic activities”[6] and a
grave public health issue.[7] While
scientists may not yet know the full scope of the health impacts of micro- and
nanoplastics, the cause is undeniably clear: the production and use of
plastics.
The Problem
Everywhere they look, scientists are finding microplastics.[8] Often so
small that they are invisible to the human eye, these tiny plastic particles
are imperceptible as they pass through airways and reach the very bottom of the
lungs. Scientists have found that inhalation is a major contributor to human
intake of micro- and nanoplastics, and exposure rates — the amount of
atmospheric micro- and nanoplastics in an individual’s vicinity — can be as
high as 5,700 microplastics per cubic meter.[9] It’s
estimated that humans can inhale up to 22,000,000 micro- and nanoplastics
annually.[10]
To better understand the issue, it is essential to examine the scales
used to classify plastic particles. Microplastics are plastic particles less
than 5 millimeters (mm) in diameter, about the size of an orange seed.[11] Airborne microplastics, however, are much smaller —
even a 0.5 mm (500 micrometer (µm)) particle is considered large. When plastic
fragments are below 0.001 mm in size (equivalent to 1 μm or 1,000 nanometers
(nm)), they are less than 1/100th of the thickness of a human hair. Particles
this small are called nanoplastics and cannot be seen by the naked eye.[12]
Multiple Sources, Same Origin
Fundamentally, atmospheric microplastics come from human creation and use
of plastics. Microplastics fall into categories based on their origin.[13] Primary
microplastics[14] are
intentionally produced at microscale for a specific use (such as agrochemicals
or pharmaceuticals). In contrast, secondary microplastics result from the
mechanical, chemical, and physical fragmentation of larger (macro) plastics,
which can include “legacy” plastics disposed of in the environment decades ago.
Every stage of the plastics life cycle, from the extraction of feedstocks to
production, transport, use, disposal, and remediation, emits both primary and
secondary microplastics and other hazardous substances.[15]
Moving through Air
Since air is a strong environmental media, the spread and effects of
airborne microplastics can remain localized or extend far beyond the point of
release. While concentration levels vary, no location remains untouched.
Airborne microplastics have been collected worldwide, but especially in the
Northern Hemisphere, including France, Iran, China, Japan, Vietnam, Nepal, the
United States, Colombia, Saudi Arabia, South Korea, Kuwait, Greece, Romania,
Pakistan, and India.[16]
Exposure to airborne
microplastics can occur through inhalation, penetration through skin pores, and
ingesting foods that contain them.[17] Microplastics’ reach inside the human body
depends on their properties, size, shape, and an individual’s metabolism,
susceptibility, and lung anatomy.[18] They can enter the respiratory system through
the nose or mouth before being deposited in the upper airways or deep in the
lungs.[19]
Once there, evidence shows that micro-
and nanoplastics can be transferred from the lung epithelial surface to lung
tissue,[20] potentially to internal organs and the vascular
system,[21] and beyond.
A Trojan Horse
The very characteristics of microplastics reveal their potential to be a
dangerously potent vector for toxics and pathogens. Microplastics often have
large specific surface areas and are predominantly hydrophobic, meaning they
repel water. These characteristics make airborne microplastics a “Trojan Horse”
capable of hiding and carrying harmful substances inside the animals or humans
who inhale, absorb, and ingest them.[22] Therefore,
knowing what’s inside plastic is as important as knowing what
lies on it.[23]
Health Impacts
While airborne microplastics research is in its infancy, studies on the
inhalation of micro- and nanoparticles of plastics show a series of adverse
effects along the respiratory tract and beyond, ranging from irritation to the
onset of cancer in cases of chronic exposure.[24] These adverse effects include:
- immediate asthma-like reactions;
- inflammatory reactions and fibrotic changes, like chronic bronchitis;
- lung disorders such as extrinsic allergic alveolitis and chronic
pneumonia;
- pulmonary emphysema;[25]
- the development of interstitial lung diseases,[26] resulting
in coughing, difficulty breathing, and a reduction in lung capacity;[27]
- oxidative stress and the formation of reactive oxygen species (ROS)
and thus the ability to damage cells (cytotoxic effects);[28] and
- autoimmune diseases.[29]
A Toxic Cocktail
Exposure to airborne microplastics is not happening in a vacuum. Humans are
exposed to multiple pollutants and hazardous chemicals daily, including
microplastics ingested via other sources, such as food or drink. While research
on airborne microplastics is in its infancy, microplastic exposure typically
happens alongside other toxic substances.
The Bigger Picture
If no action is taken, the volume of airborne microplastic emissions will
follow the expected rise in plastic production, resulting in a greater risk of
spreading potentially toxic chemicals. Regulators need to dramatically reduce
the production of plastics and phase out hazardous chemicals.
Recommendations
1. Consider the
combined “cocktail” effect. Exposure to micro- and
nanoplastics is a multi-faceted problem touching on air, water, terrestrial
environments, food, and more. Regardless of how exposure
occurs, it typically happens alongside other toxics. Humans are exposed to
multiple pollutants and hazardous chemical compounds daily, including endocrine
disruptors and POPs linked to diabetes, infertility, and hormone-related
cancers. Regulators need to apply the precautionary principle to address the
risks of combined exposure. Such an approach should include ensuring access to
information on the petrochemical compounds in plastics products and processes
(both voluntary and non-intentionally added) for ALL plastic products, not just
food-grade plastics.
2. Adopt legally
binding measures without any further delay.
Self-regulation and voluntary approaches have failed to reduce plastic and
microplastic pollution. Banning intentionally added microplastics is the first
step. Mandatory regulations will need to reduce the production and release of
plastic and its associated compounds and reduce human exposure to plastics,
microplastics, and nanoplastics.
3. Address the
full life cycle of plastics. Airborne micro- and nanoplastics
are part of the bigger story of plastics. Thus, a systemic effort is needed to
address the full issue, beginning with the extraction of fossil fuels and
associated chemicals used in plastic production. Decision makers should further
support action at the global level, supporting ambitious and effective
provisions, including strict enforcement measures in the future international
legally binding agreement on plastic that will be negotiated before the end of
2024.
This post is an adapted summary of this issue
brief.
Published March 27th, 2023
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