Apart from the known damage microplastics are causing to marine life, environmental health expert Professor Frank Kelly from the King's College London said that these particles could also be contaminating the air we breathe.

Kelly's group of researchers has just started to investigate on whether or not these microparticles of plastic in the air are a significant threat. "The particles are of a size that they are [breathable]," Kelly said. "They are increasing in number in our environment and there is a question to be asked."

Kelly said that when inhaled, these airborne microplastics can be carried out to the lower part of the lungs and may also affect the body's circulation.

Kelly is referring to microbeads, which are now said to be the most abundant form of solid-waste pollution in the planet. These are a type of microplastics commonly used as exfoliants in facial cleansers or toothpastes. Approximately 100,000 microbeads are being flushed down the drain in a single shower. As these plastics are too small to be filtered by sewage treatment plants, they find their way instead to the sea and pollute marine life.

According to Kelly, the microplastics caught in sewage treatment plants are being carried in the air. "When [farmers] spread slurry on fields, it dries out. You end up having microplastics lying on the surface of the field," he said.

Aside from already containing harmful chemicals, plastics also tend to attract other chemicals, the reason plastics are branded "toxic" and damaging to the environment. Smaller-sized plastics, however, could cause respiratory problems the same way burnt fossil fuels can, scientists claim.

Some manufacturers are already on the move to stop the use of microbeads. Alternatives to microbeads are now being considered in the manufacturing process, such as salt and ground nutshells.

Further research is still being conducted on the subject of airborne microplastics.