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Marine Litter

Vital Graphics


Plastic on the plate

Assessing the risks to human health from marine plastic

is a complex process and there is still a lot of debate

over the quantity of plastic being ingested from seafood

and whether it has the potential to affect the health of

consumers. Consumption of filter feeding invertebrates,

such as mussels and oysters, appears the most likely

route for human consumption of microplastics, because

people eat the whole organism including the gut. It has

been shown that mussels can retain some plastic in their

circularity system for over 48 days (Browne et al., 2008). It

is estimated that high consumers of mussels in Belgium

could ingest up to 11,000 pieces of microplastic in a year

(an average of 90 particles per meal over 122 meals; Van

Cauwenberghe and Janssen, 2014). The presence of

microplastic particles in seafood could pose a human health

risk (Van Cauwenberghe and Janssen 2014; Bouwmeester

et al., 2015), especially if, following ingestion, the particles

move from the digestive system to come into contact with

organs and tissues. However, there is currently no evidence

of ingested microplastics moving from the gut into other

parts of the human body (Galloway, 2015).

In contrast to microplastics, it is thought that nano-sized

material (less than 100 nm) may be more readily absorbed

through the digestive system into the body. Evidence for

this comes largely from studies investigating the ingestion

of engineered nanospheres as a method of drug delivery,

where they have been seen to cross the gut barrier and

enter the circulatory system (e.g. Hussain et al., 2001).

Bouwmeester et al. (2015) reviewed laboratory studies that

demonstrate uptake of nanoparticles bymarine organisms,

including mussels and scallops. However, they conclude

that there is insufficient evidence to determine whether

the absorbed nanoparticles can go beyond the circulatory

system and enter cells. There is also some debate about the

extent of nanoplastics in the ocean. It has been suggested

that they are produced from the fragmentation of larger

plastic particles, helped by both physical and microbial

processes (Cozar et al., 2014 and Lawet al., 2014). At present

it is technically difficult to detect nanoparticles in tissue or

in the marine environment, so new detection methods are

required to determine the extent and fate of these particles

(Bouwmeester et al. 2015).

What about the chemicals?

In addition to the potential physical effects of ingesting

plastic, there may also be associated chemical toxicity.

Marine debris has been shown to contain a cocktail of

chemicals including monomers and additives like flame

retardants, antioxidants, UV-stabilizers and plasticizers.

There is research that indicates that some of these

chemicals can act as endocrine disruptors in humans

(reviewed in Talsness et al., 2009). Chemicals of particular

concern are phthalates and bisphenol A (BPA), which

animal studies suggest may impair reproductive function

and be carcinogenic, even at very low doses (Meeker et

al., 2009; vom Saal et al., 2007). However, even though

phthalates and BPA have been in commercial use for over

50 years, studies into the effects on humans are limited.

Several studies have explored possible associations

between phthalates and conditions such as altered

semen quality and shortened gestation, although data

are limited and the results inconclusive (Hauser and

Calafat, 2005). A hazard analysis of plastic polymers

identified polyurethanes (used in hard plastic parts and

There is growing concern that toxic chemicals from plastic debris, especially micro-

and nanoplastics, are making their way into the food chain. But are they harmful?

Anthropogenic marine debris has been observed throughout the ocean, from beaches

and shallow coral reefs to the deep sea. Plastic particles have been found in hundreds

of species of marine organisms, including many species of fish and shellfish sold

for human consumption. A recent study found plastic in one out of every four fish

purchased from markets in the United States and Indonesia (Rochman et al., 2015).

Globally, average per capita fish consumption is nearly 20 kg per year and seafood

equates to nearly 17 per cent of the world’s protein consumption (FAO, 2014), so there

is a potential pathway for human exposure to plastic.

Plastic in the food chain –

a threat to human health?