People may be ingesting as much as 5g of plastic every week - the equivalent of a credit card, a new study has found.

It focused on microplastics, which are plastic particles no bigger than 5mm. They can end up in our digestive system and bloodstream via the food chain.

Australian researchers carried out a systematic review of over 50 peer-reviewed studies on this topic and from that, they calculated an ingestion rate for humans.

They looked at the presence of microplastics in a number of food and drinks, such as water, beer, fish, salt and honey.

They found that the biggest source of plastic ingestion came from water, including tap and bottled water. European water was less polluted than water from the US.

Shellfish was another big source.

The researchers acknowledged that the amount of microplastics consumed by individuals depends on a ‘combination of parameters that is highly variable', such as age, geographic location and lifestyle options.

However, they said that they are confident that following their review and a subsequent analysis, ‘up to 5g per week of microplastic particles are potentially ingested by humans', or 250g per year.

The study was carried out by researchers at the University of Newcastle in Australia on behalf of the World Wildlife Fund (WWF). According to WWF International's director general, Marco Lambertini, not only are plastics polluting oceans and waterways and killing marine life, ‘it's in all of us and we can't escape consuming plastics'.

"If we don't want plastic in our bodies, we need to stop the millions of tonnes of plastic that continue leaking into nature every year.

"In order to tackle the plastic crisis, we need urgent action at government, business and consumer levels, and a global treaty with global targets to address plastic pollution," Mr Lambertini said.