What are microplastics doing to human health? Scientists work to connect the dots

Plastic serves as a building block for our food packaging, water pipes, rubber tires and synthetic fabrics. But plastic also litters waterways, soil and air so humans and other animals wind up taking in tiny versions with unknown consequences. 

People unknowingly ingest microplastics from what we eat, drink and breathe. Some scientists fear exposure to microplastics could increase vulnerability to heart disease, cancer and other illnesses. They're working to connect the dots between microplastics and any health hazards.

At this week's United Nations' global summit on plastic pollution in Ottawa, delegates are working toward a treaty to address plastics from production to use and disposal. 

Dr. Leonardo Trasande directs the NYU Langone Center for the Investigation of Environmental Hazards and is attending the meeting in Ottawa. Trasande became interested in the hormone hacking or endocrine disrupting properties of plastics when he was resident in pediatrics and seeing patients with diabetes. 

"Microplastics are in many ways a harbinger of the much bigger problem," Trasande said.

While possible links between microplastics and illnesses like Type 2 diabetes are not definitive, researchers are exploring some concerning hints.

Most plastics aren't recycled and last for decades. When something made of plastic does break down, it fragments into small bits known as microplastics that can pollute and build up in the environment and leach chemicals. 

Scientists categorize degraded plastic waste products by size. Microplastics are tiny particles less than than five millimetres in diameter, or about the size of a sesame seed.

Nanoplastics are flecks too small to be noticed by the human eye with diameters of less than a billionth of a meter or a nanometer. By comparison, a sphere with a diameter of one nanometre is as small relative to a softball as a softball is to the Earth.

Sources of microplastics range from the microbeads used in cosmetic and personal care products to lentil-sized plastic pellets also known as nurdles.

Plastic production is on track to triple by 2060, according to the Organisation for Economic Co-operation and Development, unless the treaty sets production limits, as some have proposed.   

Last month, researchers writing in the New England Journal of Medicine using special microscopy techniques found microplastic and nanoplastic chemicals in the plaque lining arteries.

In the observational study of more than 250 patients who were having tests for carotid artery disease, finding polyethylene in their plaque was associated with heart problems compared with those without having any plastics detected. This type of study can't show whether the tiny plastics caused the heart problems, just associations.

"We've done studies documenting that 50,000 Americans die each year from heart disease due to phthalates, for example, which is frighteningly consistent with the findings of microplastics and linkages to coronary artery disease," Trasande said.