Microplastics are plastic particles less than 5 mm in diameter that are found in the environment and in humans.
In addition to the health threats they pose on their own, microplastics may also adsorb heavy metals and organic small molecules, causing additional harm to organisms.
A recent study published in Environmental Science and Technology Letters found that microplastics can interact with other pollutants to enhance toxicity.
Benzophenone is a common anti-UV ingredient in sunscreens and a contaminant.
Scientists compared the absorption of the heavy metal chromium by microplastics with and without benzophenone attached.
The results found that chromium was more readily adsorbed by polystyrene microplastics when benzophenone was present, changing from the less toxic trivalent ion to the more toxic hexavalent ion.
The mixture of the experimental group was able to significantly inhibit the growth of microalgae, compared to the control group without the presence of benzophenone.
This suggests that the microplastics interacted with organic matter and heavy metals and converted them to more harmful forms.