Recent research published in Environmental Science & Technology (an American Chemical Society [ACS] publication) by a collaborative team from Hohai University and Nanjing University in Nanjing, China have found that contact lenses could shed tiny fragments of plastic after exposure to sunlight.
Let’s start with microplastics.
Microplastics are tiny plastic particles typically >5 mm in size and divided into two wide-ranging classifications: primary and secondary.
Primary microplastics, designed to be very small, are often found in cosmetic and cleaning products; they’re typically washed down the drain and enter into waterways.
Secondary microplastics are larger and typically used in packaging or building materials that are ground down over time: plastic bags, bottles, food containers, paints, electronics.
Both categories are found in oceans, lakes, waterways, soil, air, and food [specifically shellfish, such as oysters, and other fish for human consumption].
And their impact?
They can have a significantly negative impact on the environment—particularly marine life, where it can disrupt reproductive systems, stunt growth, and cause tissue inflammation, including liver damage.
While research is ongoing into the human impact, inhaling fine particles of any type are known to cause respiratory irritation that could lead to more serious cardiovascular problems.
How are these microplastics typically measured?
In marine life, plastic fragments are filtered from large samples of water and then manually counted under a microscope.
That sounds tedious.
Indeed. Not to mention time-consuming, slow, and sometimes inconsistent.
So how does this relate to the new research?
Researchers wanted to develop an automated method that could detect and count microplastic particles in small samples—like contact lenses—quickly.
So what’d they do?
They collected six different contact lenses (of varying lifespans):
- 1-3 → same brand with lifespans of 1 day, 1 month, and 6 months
- 4-6 → Three different brands, all with lifespans of 6 months
The lenses were stored in water under a lamp (to mimic sunlight) and rinsed with water every 10 hours for three times total to simulate normal wear.
After each of the lenses received an equivalent of 30 or 90 days of sunlight, the researchers studied their water.
How’d they study microplastics?
The researchers designed a high-content, automated screening system that captured microscopic images of the samples, identifying and validating the microplastics on a 1 to 100 μm threshold.
These images were then processed and quantified—measuring the diameter, area, and shape of each particle—to determine the number of microplastics present in the water.
Findings?
They noted faster, more accurate data when compared to a manual analysis of the microplastics.
With no sunlight, no microplastics were noted in the water.
However, after a 90-day equivalent of light exposure, increasing amounts of microplastics were evident.
See here for data numbers (Table S1).
Which water had the greatest amount?
Lenses with a shorter lifespan (daily and monthly) demonstrated the largest number of microplastics following sunlight exposure.
‘Wow’ me with a number.
Based on the findings, the study authors estimated that 90,968 particles of microplastic could be released from a pair of contact lenses during a year of wearing if worn for 10 hours a day.
Conclusions?
The study authors noted that, despite the data, the direct human health impact of eye exposure to microplastics remains a mystery; however, they stressed the urgent need for more research to further assess potential health risks.