Every breath in modern cities contains more than just oxygen, carbon dioxide, or smog. A new invader, as small as it is dangerous, has colonized the air we breathe: microplastics. Invisible, ubiquitous and persistent, they move between avenues and skyscrapers, cling to urban dust and fall with the rain.
A recent study led by Chinese scientists confirms this with alarming figures: the concentrations of microplastics in the urban atmosphere could be up to a million times higher than what was estimated with previous technologies. Smart cities, emblematic of urban development in the 21st century, now face an unexpected and monumental challenge: how to reverse the presence of plastic in the air?
“Plastic is everywhere”: from the ground to the air
By: Gabriel E. Levy B.
For decades, the dominant narrative about plastic pollution focused on oceans, rivers, and soils. Images of turtles trapped in bags or fish with stomachs full of synthesized polymers dominated environmental campaigns.
However, for a little over a decade, evidence began to emerge about the presence of these materials in the atmosphere.
In 2019, a study by Allen et al. in the French Pyrenees revealed that microplastic particles could travel hundreds of kilometers in the air before being deposited in seemingly “pure” mountainous areas.
It was a first wake-up call. Since then, research such as the one recently published by the Institute of the Terrestrial Environment of the Chinese Academy of Sciences has been dismantling an inconvenient truth: the air in cities is deeply polluted by plastics, in ways that traditional technology had barely glimpsed.
The Chinese study, published in Science Advances, went further than any previous work: it detected nanoplastics as small as 200 nanometers and measured concentrations reaching up to 180,000 particles per cubic meter in cities such as Guangzhou and Xi’an.
The particles float in the air, travel attached to dust, and fall with the rain. They are inhaled by millions of people every day, and their accumulation poses not only an environmental problem, but also a health and urban challenge.
Breathing plastic: the silent enemy of smart cities
The idea of Smart Cities revolves around sustainability, connectivity and citizen well-being.
These are data-driven urban environments, where sensors, artificial intelligence and digital planning work to optimise transport, reduce energy consumption and improve quality of life.
However, what these systems are not yet able to detect and combat effectively are the invisible pollutants that inhabit the air. And among them, microplastics are emerging as the most elusive.
The accumulation of these polymers in the urban atmosphere is not only an environmental problem, but a direct threat to public health.
Researchers such as María José López de San Román, an expert in environmental toxicology at the CSIC, warn that prolonged inhalation of microplastics can cause lung inflammation, immunological alterations and possible systemic effects that are still poorly understood.
Unlike other pollutants, microplastics do not dissolve or disappear: they fragment, disperse and become embedded in everyday life.
In this sense, Smart cities face a structural contradiction: while their infrastructures seek to digitize the environment to make it more habitable, plastic pollution, a product of this same industrial and consumer development, continues to infiltrate through uncontrolled channels.
Plastic is present in textiles, tires, packaging, electronic devices and even in the layers that protect urban sensors. The smart city, paradoxically, may be feeding the cloud of microplastics that surrounds it.
And the problem is not only local: the study by the Chinese Academy revealed that the re-suspension of urban dust and rain are the main vectors of transport and elimination of microplastics, generating flows of up to 2,500 million particles per square meter per day.
This means that plastics not only stay where they are generated, but circulate, fly, deposit, rise again. The urban atmosphere becomes a gigantic corridor of volatile plastics.
The smart future demands clean air
Although Smart City technologies promise more efficient cities, their success will be conditioned by their ability to face challenges that are not only technological, but also environmental and structural. Incorporating sensors that measure the presence of microplastics in real time, redesigning urban materials to prevent plastic degradation or implementing large-scale atmospheric filtering mechanisms are still distant but urgent steps.
Authors such as Roland Geyer, a researcher at the University of California and author of the influential article Production, Use, and Fate of All Plastics Ever Made, insist that plastic will not disappear, but it can be managed more rationally if the paradigm of production and consumption is transformed.
In Smart cities, this management must include not only waste treatment, but also the monitoring and mitigation of invisible pollutants such as microplastics.
Likewise, architect Carlo Ratti, director of MIT’s Senseable City Lab, has proposed that true urban intelligence does not lie in the number of sensors deployed, but in the ability of cities to learn from their mistakes and anticipate their consequences.
From this perspective, air pollution by microplastics represents a lesson not yet learned: the need to integrate environmental health into the very design of the urban planning of the future.
The urban atmosphere, therefore, should not be seen as a simple empty space between buildings, but as a dynamic ecosystem that interacts with every human action.
In this ecosystem, plastic has also found its place, and reversing its presence will be one of the greatest sustainability challenges of the 21st century.
From Paris to Bogota: cities under the plastic cloud
The problem is not unique to China. Paris, one of the first cities to systematically measure microplastics in its atmosphere, found alarming concentrations in 2020 reaching up to 10 particles per cubic meter in residential areas.
The figure seems modest compared to the numbers of the Chinese study, but the methodologies used then were less sensitive. It is estimated that, with new techniques, the real figures could be hundreds or thousands of times higher.
In Latin America, a pioneering study by the Institute of Environmental Studies of the National University of Colombia detected microplastics in the air of Bogotá in 2023. Although monitoring is just beginning, the researchers warned about its possible link to respiratory diseases and pollution from vehicular traffic and the textile industry.
In London, the Breathe London initiative has begun exploring methods to include emerging pollutants, such as microplastics, in its urban sensor networks. However, there is still a lack of robust infrastructure that allows a systematic and reliable reading of these volatile polymers.
Even in cities considered leaders in sustainability, such as Copenhagen or Amsterdam, the management of atmospheric microplastics is still a pending issue.
Plastic pollution infiltrates the atmosphere from shoe soles, tire wear, fibers released by washed and dried clothing, or scattered industrial waste.
The air, as a common space, becomes the great collector of urban excesses. And so far, no city has managed to establish an effective protocol to stop this silent invasion.
In conclusion
Reversing the accumulation of microplastics in the urban atmosphere is one of the most urgent challenges for Smart Cities.
It is not enough to digitize traffic or automate street lighting.
The urban intelligence of the future will also have to be ecological, and decisively confront invisible but lethal pollutants. Breathing plastic cannot be the price of progress.
References
- Zhang, L., Liu, Y., Wang, L., & Li, W. (2024). Atmospheric micro- and nanoplastics in urban environments. Science Advances.
- Geyer, R., Jambeck, J. R., & Law, K. L. (2017). Production, use, and fate of all plastics ever made. Science Advances, 3(7), e1700782.
- Allen, S., Allen, D., Phoenix, V. R., Le Roux, G., Jiménez, P. D., Simonneau, A., … & Galop, D. (2019). Atmospheric transport and deposition of microplastics in a remote mountain catchment. Nature Geoscience.
- López de San Román, M. J. (2022). Environmental toxicology of inhaled microplastics. CSIC, Institute of Environmental Diagnosis and Water Studies.
