Using it regularly introduces tens of thousands of microplastic and nanoplastic particles into the body each year.
By Patrick Lejtenyi, Concordia University
The tropical beauty of Thailand’s Phi Phi islands is not the kind of place where most PhD journeys begin. For Sarah Sajedi, however, it was not the beaches themselves but what lay beneath them that sparked her decision to leave a career in business and pursue academic research.
“I was standing there looking out at this gorgeous view of
the Andaman Sea, and then I looked down and beneath my feet were all these
pieces of plastic, most of them water bottles,” she says.
“I’ve always had a passion for waste reduction, but I
realized that this was a problem with consumption.”
Sajedi, BSc ’91, decided to return to Concordia to pursue a
PhD with a focus on plastic waste. As the co-founder of ERA Environmental
Management Solutions, a leading provider of environmental, health, and safety
software, she brought decades of experience to compliment her studies.
Her latest paper, published in the Journal of
Hazardous Materials, looks at the science around the health risks posed by
single-use plastic water bottles. They are serious, she says, and seriously
understudied.
Sarah Sajedi with Chunjiang An: “Drinking water from plastic
bottles is fine in an emergency but it is not something that should be used in
daily life.”
Tiny threats, little known
In her analysis of more than 140 scientific papers, Sajedi
reports that people ingest an estimated 39,000 to 52,000 microplastic particles
each year. For those who rely on bottled water, that number climbs even
higher—about 90,000 additional particles compared to individuals who primarily
drink tap water.
These particles are invisible to the eye. Microplastics
range in size from one micron (a thousandth of a millimeter) to five
millimeters, while nanoplastics are smaller than a single micron.
They are released as plastic bottles are manufactured,
stored, transported, and gradually degrade. Because many bottles are made from
low-grade plastic, they shed particles whenever they are handled or exposed to
sunlight and changes in temperature. Unlike plastics that move through the food
chain before entering the human body, these are consumed directly from the
container itself.
According to Sajedi, the health risks are significant. Once
inside the body, these small plastics can pass through biological barriers,
enter the bloodstream, and reach major organs. Their presence may contribute to
chronic inflammation, cellular oxidative stress, hormone disruption,
reproductive issues, neurological damage, and some cancers. Still, their
long-term impacts are not fully understood, largely because of limited testing
and the absence of standardized ways to measure and track them.
Sajedi also outlines the range of methods available to
detect nano- and microplastics, each with benefits and limitations. Some
approaches can locate particles at extremely small scales but cannot reveal
their chemical makeup. Others identify the material composition but overlook
the tiniest plastics. The most sophisticated and dependable tools are often
prohibitively expensive and not widely accessible.
Education is the best prevention
Sajedi is encouraged by the legislative action that has been
adopted by governments around the world aimed at limiting plastic waste.
However, she notes that the most common targets are single-use plastic bags,
straws, and packaging. Very few address the pressing issue of single-use water
bottles.
“Education is the most important action we can take,” she
says. “Drinking water from plastic bottles is fine in an emergency but it is
not something that should be used in daily life. People need to understand that
the issue is not acute toxicity—it is chronic toxicity.”
Reference: “Unveiling the hidden chronic health risks of
nano- and microplastics in single-use plastic water bottles: A review” by Sarah
Sajedi, Chunjiang An and Zhi Chen, 14 June 2025, Journal of Hazardous
Materials.
DOI:
10.1016/j.jhazmat.2025.138948
Funding: Natural Sciences and Engineering Research Council
of Canada