The beautiful beaches of Thailand’s Phi Phi Islands may seem like an odd place to begin a PhD journey, but for Sarah Sajedi, a moment on those sandy shores changed everything.
While admiring the stunning view of the Andaman Sea, she glanced down and saw the sand littered with plastic waste—mostly discarded water bottles.
That simple moment made her realize the problem wasn’t just about litter, it was about overconsumption.
Sajedi had always cared about reducing waste. With a background in business and a successful career as co-founder of ERA Environmental Management Solutions, she had years of experience in environmental safety.
But this moment inspired her to return to Concordia University to earn her PhD, focusing on the dangers of plastic waste.
In her most recent research paper, published in the Journal of Hazardous Materials, Sajedi explored the health risks linked to single-use plastic water bottles. Her findings were alarming—and pointed to a problem that isn’t getting enough attention.
Sajedi reviewed over 140 scientific studies on the topic. The results showed that the average person consumes between 39,000 and 52,000 microplastic particles every year. People who regularly drink bottled water may consume up to 90,000 more particles compared to those who drink tap water.
These tiny plastic particles are nearly impossible to see. Microplastics range from one micron (a thousandth of a millimeter) to five millimeters in size. Nanoplastics are even smaller than that. These particles are created as plastic bottles are made, transported, stored, and used.
Since many water bottles are made from cheap, low-quality plastic, they easily break down into small pieces when they’re handled or exposed to heat and sunlight. Unlike plastic particles that enter our bodies through food, these are swallowed directly from the bottle.
Once inside the body, micro- and nanoplastics can pass into the bloodstream and reach important organs.
They may cause long-term inflammation, stress on cells, hormone problems, trouble with reproduction, brain damage, and even cancer. But because there isn’t yet a standard way to measure or track these plastics, the full impact on human health is still unclear.
Sajedi’s paper also discusses the challenges of studying microplastics. Some methods are good at finding very small particles but can’t tell what kind of plastic they are. Others can analyze what the plastic is made of but miss the tiniest particles. The most accurate tools are expensive and not always available to researchers.
While laws in many countries are helping reduce plastic waste—often by banning bags, straws, or packaging—Sajedi notes that single-use plastic water bottles are usually left out of these efforts. That’s a big problem.
She believes education is the key. “Plastic bottles might be okay during an emergency,” she says, “but they shouldn’t be used every day.” Sajedi wants people to understand that the danger isn’t immediate poisoning—it’s long-term health damage from small amounts of plastic that build up in the body over time.
Her work serves as an important reminder that the choices we make every day—like reaching for a bottle of water—can affect our health in ways we may not yet fully understand.
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The study is published in Journal of Hazardous Materials.
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