© Sergio Moraes / Reuters
Despite the much-touted health benefits of fish, you may be getting more than you asked for on your dinner plate. A new study reveals that around a quarter of fish sampled from markets in Indonesia and California contains plastic or fibrous material.

Researchers from the University of California, Davis, and Hasanudd University in Indonesia link this difference to the way humans process waste. Indonesian fish mostly had plastic residue in their guts leading scientists to suggest that it is directly linked to the amount of plastic tossed into the ocean and on the beach. This may also be escalated by the amount of bottled water consumed in Indonesia due to a lack of purified tap water.

Californian fish on the other hand showed high quantities of fibrous materials and in this case laundry may be to blame. Authors of the report suggested that copious amounts of small bits of fabric and thread get into the sewage system on a daily basis with millions of people adding to the share each time they do the laundry. These items are so small they pass all the filters in more than 200 wastewater treatment plants off the Californian shore and end up in the ocean and subsequently inside fish.

"We think the type of debris in the fish is driven by differences in local waste management," said lead author Chelsea Rochman, a David H. Smith postdoctoral fellow at the UC Davis.

The researchers sampled 76 fish from markets in Makassar, Indonesia, and 64 from Half Moon Bay and Princeton in California.

So far to avoid eating plastic one must stick to filleted fish as scientists are still studying whether chemicals from ingested plastic can transfer into meat.