Miriam Diamond was watching her young son jump on the living room couch when it suddenly dawned on her: his casual horseplay might not be so carefree after all.
As the foam cushions compressed and rebounded, Diamond, an environmental chemist at the University of Toronto, wondered what might be getting puffed into the air.
"I thought, 'I know there are flame retardants in that couch,'" she says, "and I know the compression of the foam would cause the chemical to be ejected more quickly."
The moment prompted her to investigate how toxic chemicals can be emitted by everyday household products - from consumer electronics to children's mattresses. Her research has shown how a wide range of common consumer products can expose people to contaminants such as per- and polyfluoroalkyl substances (PFASs), or "forever chemicals," which are associated with immune problems, impaired fetal and infant growth, and increased risk of cancer.
Diamond didn't set out to scrutinize the safety of our shopping carts. Her early-career research focused on how contaminants move through outdoor ecosystems, examining how substances such as arsenic and mercury enter, circulate and settle in aquatic systems such as the Great Lakes and waterways of Canada's Far North.
But over time, the questions that would come to define her work moved closer to home.
"Most researchers in my field wanted to work in cool places like the Arctic or the high mountains," says Diamond, a professor of Earth sciences in U of T's Faculty of Arts & Science. "But I turned my attention to the indoors because I had two young children before tenure and couldn't travel - and now I'm worrying about their health and the health of my grandchildren."
Diamond arrived as a member of U of T's faculty after pursuing an unconventional academic path. After earning an undergraduate degree in biology from U of T, she completed a master's in zoology at the University of Alberta - studying bird behaviour - and another in mining engineering at Queen's University before returning to U of T for her PhD in chemical engineering and applied chemistry.
"Bird behaviour studies showed me the importance of being very observant - and engineering taught me to think about how to connect the dots within a system to understand it and to solve problems," says Diamond, who holds, or has held, cross appointments at U of T's School of the Environment, the department of chemical engineering and applied chemistry in the Faculty of Applied Science & Engineering, the Dalla Lana School of Public Health and the department of physical and environmental sciences at U of T Scarborough.
Her son's couch bouncing illustrated her multidisciplinary approach at work: she quickly realized what she was witnessing wasn't just a child at play - it was chemical transport in action.
From that point on, Diamond and her team began viewing humans not just as recipients of chemical exposure, but active agents in chemical transport. That key insight helped reframe how exposure was understood within indoor environments, which scientists had previously believed was mainly the result foods we ate.
In 2005, a study led by Diamond found that inhalation and ingestion of household dust were key routes of exposure to flame retardants , particularly among toddlers. This raised the possibility that exposure could come from everyday sources in environments that we consider to be safe refuges.
Diamond set out to test this idea in gymnastics facilities (by this point, her son had graduated from bouncing on the couch to jumping and rolling on flame-retardant foam gym mats). Her team surveyed the relevant chemical levels in dust and air inside the gym. "Lo and behold, they were 10 to 20 times higher than in homes," she says.
Diamond has since continued to uncover new sources of exposure, from school uniforms and cosmetics to fast food packaging .
A 2025 study on children's mattresses, which Diamond's team found emit flame retardants and other harmful chemicals, drew international media attention , which Diamond further leveraged to outline practical steps people can take to reduce exposure - from washing bedding and limiting items on children's beds.
However, she pointed out, consumers have little ability to choose products with fewer added chemicals because this information is generally unavailable without scientific testing.
As a result, she emphasizes that the onus for reducing harms shouldn't lie with consumers. "Culpability ultimately lies with the manufacturers," she says. "Government must have better oversight, but they cannot keep up with innovations in the private sector."
Diamond has attempted to speed the process by engaging in significant outreach to raise awareness of the risks, prompt regulatory scrutiny and drive changes in industry practices. This includes working with CBC's Marketplace to translate scientific research for public consumption. In one investigation, she carried out lab testing that found high levels of toxic cadmium in children's jewelry, prompting Health Canada to tighten regulations and one retailer to pull products off shelves . Another episode uncovered high levels of lead and PFAS in fast-fashion clothing, with retailers later ceasing sale of products of concern in the Canadian market .
"Many researchers believe that if we do the research, it will be adopted through evidence-based legislation and policy. That's wishful thinking," she says. "Policy doesn't change because of evidence alone."
Diamond continues to promote evidence-driven chemicals management as a vice-chair of the International Panel on Chemical Pollution. She previously served on numerous national and global forums as co-chair of the federal Chemicals Management Plan Science Committee and the provincial Toxics Reduction Scientific Expert Panel.
She says her sense of responsibility to build bridges between academia, government and the public was shaped by her mentors, particularly her U of T PhD supervisor Donald MacKay , who "left an indelible mark on international chemicals management," and metallurgist and peace activist Ursula Franklin , "an incredibly compassionate and generous person who deeply influenced my ways of thinking." (Diamond's office, as it happens, is located on Ursula Franklin Street . "How wonderful is that?")
That influence carries through in the mentorship Diamond provides today. Kayla Simpson, a PhD student in Diamond's lab, describes her as "a powerful woman in STEM" and a supportive supervisor. "She teaches us to present ourselves clearly and confidently," says Simpson, whose research is developing approaches to determine sources of microplastic pollution, "and gives us the freedom to pursue our own ideas, with her support always alongside."
Diamond says it's important for her to create an environment where women and people from underrepresented groups feel empowered. "It's when you feel confident and supported that you can do your best work," she says. "And we need everyone to be able to do their best work."
In addition to her longstanding research on PFAS, microplastics and human exposure in indoor environments, Diamond's lab is now also exploring one of the field's most ambitious questions: what level of chemical pollution can the planet sustain before the damage is irreversible?
"I want to save the world," she says. "I'm not doing a great job - but we all chip away at it."
