From Environment Agency

Assessing the impact of exposure to microplastics in fish

Report – SC120056 MARCH 2015

Executive summary

Plastic wastes are rapidly accumulating in landfill and in natural habitats, especially the marine environment, where they create a potential hazard for wildlife. The full environmental impacts of plastic waste are not understood, but the United Nations Environment Programme (UNEP) estimates that marine plastic wastes cause the deaths of hundreds of thousands of aquatic vertebrates each year. These deaths result partly from entanglement or physical damage caused by macroplastics, but there are also concerns that ingested plastic fragments (microplastics) may block the digestive system and cause starvation. Furthermore, it is thought that persistent organic pollutants may partition to plastics and be transported into the food chain. To address these concerns laboratory exposures were conducted to assess the biological effects
of ingested plastic particles.

In a first experiment, larval three-spined stickleback (Gasterosteus aculeatus) were exposed for 7 days to suspended 1.0 µm fluorescent polystyrene spheres at a density of 10, 100 and 1,000 mg/l. Fluorescent imaging confirmed that the larvae ingested the plastics and that the quantity of fluorescence within the digestive tract was proportional to the density of plastics added to the water. There was no evidence that ingestion of the plastics impacted larval survival, but a negative relationship between quantity of plastic added to the beaker and condition factor was observed (r = -0.380; p<0.001, n = 144); condition factors in the low, medium and high exposures were 14.6% (p<0.05), 18.9% (p<0.01) and 31.6% lower (p<0.01), respectively, when compared to the controls. An increase in expression of the gene encoding the detoxification enzyme CYP1A was also observed in larvae exposed to the medium and high densities of plastic (p<0.05). In a second experiment, adult three-spined stickleback were exposed for 7 days to Artemia that had been exposed to 1.0 µm or 10 µm fluorescent plastic spheres. High and low dose groups were generated by feeding with either 100% or 10% contaminated Artemia, respectively. The low dose groups and a control group were fed 90% and 100% non-contaminated Artemia, respectively. Excretion of the plastics was monitored in a sub-group of fish that were fed non-contaminated Artemia for a further 14 days after exposure. Estimates of fluorescent intensity in faecal samples indicated that uptake and excretion of the plastics was rapid; plastics were found in the faeces within 1 day of initiating exposure, but within 2 days of ceasing exposure a 71% decrease in fluorescence was observed, implying that the plastics are not retained within the digestive tract for prolonged periods. There was no evidence for translocation of the plastics from the digestive tract to the circulatory system as reported in other studies. Furthermore, there was no evidence that ingestion of the plastic-contaminated Artemia impacted on adult fish survival, body size or condition or expression of CYP1A (p>0.05).

In a third experiment, larval stickleback were fed for 14 days on Artemia that had been exposed to graded concentrations of bisphenol-A (BPA) in the presence or absence of 0.5 µm fluorescent polystyrene spheres. Ingestion of the microplastics (MPs) and/or BPA-exposed Artemia did not impact survival, growth or body condition of the fish larvae; however, a positive relationship between BPA concentration and CYP1A expression was observed (r = 0.415, p<0.05, n = 31) in fish fed Artemia that had been exposed to BPA in the presence of MPs. This relationship was not evident for fish fed Artemia exposed to BPA in the absence of the MPs, indicating that MPs were indeed partitioning the BPA and transporting it through the food chain.

Collectively, these experiments demonstrate that fish will actively take up microplastics from the water column, as well as ingesting them via their diet. Although ingestion of the micron-sized plastics does not appear to adversely impact the survival or health of adult fish, at least in the short term, there is evidence to support negative changes in the body condition of larval fish. Furthermore, there was evidence that MPs have the potential to partition an organic pollutant and act as a vector to transport this chemical into the food chain. These results highlight the need for longer-term studies that can more fully evaluate the environmental impacts of plastic ingestion for aquatic organisms.

4 Discussion

Plastics have become a ubiquitous environmental contaminant and each year large numbers of aquatic vertebrates are reported to die as a consequence of ingesting macroplastics or becoming entangled in plastic debris. Until now relatively little has been known about the potential hazard posed by MPs; however, the results of this investigation suggest that MPs may pose a hazard to early life-stages of fish. Larval
fish were observed to actively feed upon the MPs and to accumulate large quantities of fluorescing particles within their digestive system. This ingestion resulted in impacts for health with body condition decreasing by 14% to 32% after 7 days of exposure depending on exposure densities.

It has recently been shown that ingestion of MPs can negatively impact algal feeding in zooplankton ( In our study, there was also no evidence for an impact of MPs on survival of the three- spined stickleback larvae during the 7-day exposure; however, a negative effect on body condition was observed for all exposure groups. Surprisingly, the reduction in larval condition factor appeared to result from a small but significant increase in body length, rather than a direct effect on body weight.

The mechanism underlying the MP-induced increase in body length is unknown. There are reports that polystyrene can leach styrene oligomers which are weakly oestrogenic (Bang et al. 2012); oestrogens are known to be involved in regulation of fish growth and exposure to oestrogens has been shown to have a growth-promoting effect in larval stickleback (Hahlbeck et al. 2004). However, the lack of evidence for an effect of MP exposure on expression of vitellogenin mRNA would suggest that biologically active concentrations of oestrogenic compounds were not leaching from the plastics. Furthermore, there was no evidence for an effect of MP exposure on expression of IGF1, further indicating that the increased growth was unlikely to be a direct consequence of perturbation of the endocrine system. However, a relationship between quantity of MP ingested and expression of the CYP1A gene was observed. This may indicate leaching of organic compounds from the MPs; CYP1A is an important enzyme involved in detoxification of xenobiotics (Široká and Drastichová 2004). As cytochrome P450s also play a role in endogenous metabolism, the MP-induced increase in CYP1A may have indirectly increased endogenous sterol biosynthesis and thus increased energy for somatic growth, although further work would be necessary to confirm this.
Irrespective of the mechanism underlying the effects of MPs on somatic growth, it is important to note that as body weight did not increase proportionally to body length it is unlikely that the growth-promoting effects of the MPs would be sustainable in the longer term and continued exposure to MPs would be likely to result in starvation- induced mortality in the longer term.

In the second experiment, uptake of the MPs via ingestion of MP-contaminated Artemia (trophic transfer) was investigated. Consistent with a previous study in which a range of zooplankton were demonstrated to have the capacity to ingest 1.7–30.6 µm polystyrene beads (Cole et al. 2013), the Artemia were observed to ingest both the 1.0 µm and 10 µm polystyrene bead plastic particles once they had undergone their first moult (

Given the rapid egestion of the MPs, the lack of an effect of MPs on somatic growth, body weight or even body condition of the adults is therefore not surprising. However, there was also no evidence for an effect of ingested MPs on CYP1A mRNA expression in the adults, which may indicate that the adults were not exposed to sufficient MPs to induce a response. It should be noted that in the larval fish, CYP1A was isolated from whole body homogenates, whereas for the adults CYP1A was isolated from the liver. There is some evidence that intestinal expression of CYP1A in mammals can be regulated by the Toll-like receptor 2 (TLR2) which is involved in pathogen recognition (Do et al. 2012). Orthologs of TLR2 have been identified in teleost fish and it is possible that the increased expression of CYP1A mRNA observed in the larvae was a consequence of microbes adhered to the MPs (Zettler et al. 2013) inducing an immune response. This would be an interesting area of research for future studies.

It is also important to note that the size of the plastics relative to the size of the animal is likely to be an important consideration when considering the effects of the plastics (Besseling et al. 2012); it is possible that induction of CYP1A in the larvae was an indirect consequence of altered metabolism caused by blockages in the gut that did not occur in the adults due to their greater relative size. Furthermore, despite reports that MPs may translocate from the digestive system to other organs within the organism where they have the potential to induce biological effects (Browne et al. 2008), we found no clear evidence for translocation of the MPs to the circulatory system of the adult fish. Thus, at least under the exposure scenario described here, ingestion of zooplankton contaminated with 1–10 µm plastics does not appear to pose a significant hazard in this context. Although these results indicate that ingestion of small (1–10 µm) MPs is unlikely to present a significant biological hazard for larger-bodied fish in the short term, further investigations using both larger plastics and longer exposure periods are necessary before it can be concluded that trophic transfer of small MPs does not pose a threat.

Additional to the potential for ingested MPs to induce biological effects, there are also concerns that MPs may act as vectors to transport organic pollutants through the food chain (Teuten et al. 2009). Hydrophobic organic contaminants have been shown to have an affinity to adsorb to plastics and have been detected on plastic pellets collected from the marine environment (Mato et al. 2001, 2002, Endo et al. 2005, Rios et al. 2007, Teuten et al. 2007, 2009, Bakir et al. 2012, 2014, Antunes et al. 2013). Furthermore, there is some evidence for plastic-mediated transfer of organic contaminants to organisms (Ryan et al. 1988, Teuten et al. 2007, Besseling et al. 2012), although little is known about the potential for accumulation of these contaminants through the food chain. In this experiment, fish larvae were exposed via their diet to live Artemia that had been exposed to graded concentrations of BPA in the presence or absence of MPs. A positive relationship between nominal BPA concentration and expression of the CYP1A gene was observed in fish fed Artemia that had been exposed to BPA in the presence of the MPs, but no such relationship was observed for fish fed Artemia exposed to BPA in the absence of MPs. As the fish were not directly exposed to the BPA but only indirectly exposed through feeding on the Artemia that had ingested the BPA-contaminated MPs, this would suggest that the MPs can act as vectors to transport BPA through the food chain and that BPA is desorbing from the plastics at concentrations sufficient to result in a detectable response to exposure as indicated by CYP1A expression.

Collectively, these experiments demonstrate that fish will actively take up microplastics from the water column, as well as ingesting them via their diet. Although ingestion of the micron-sized plastics does not appear to adversely impact the survival or health of adult fish, at least in the short term, there is evidence to support negative changes in the body condition of larval fish. Furthermore, there was evidence that MPs have the potential to partition an organic pollutant and act as a vector to transport this chemical into the food chain. These results highlight the need for longer-term studies that can more fully evaluate the environmental impacts of plastic ingestion for aquatic organisms.

To download the complete study go to: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/411982/Assessing_the_impact_of_exposure_to_microplastics_in_fish_report.pdf

Related:

How Microplastics from fleece could end up on your plate

By Elizabeth Grossman on January 15, 2015 From Civil Eats

New research on fish in the Great Lakes could have implications for seafood everywhere.

You wouldn’t eat the tiny plastic fibers that come off your fleece jacket, would you? Research released last week suggests we might be eating the fish that do. The study–the first of its kind–found that Great Lakes fish are swallowing micro-plastic fibers [PDF] that have found their way into the waste stream from washing machines. And the fish that ingest them include species sought after by Great Lakes anglers, among them: brown trout, cisco–also known as “lake herring”–and perch.

“Every one of the 18 species we sampled showed some plastic and the majority of this was fibers,” explained Sherri Mason, professor of chemistry and environmental sciences program coordinator at the State University of New York at Fredonia. Mason then sampled 17 different southern Lake Michigan fish species for the presence of microplastics. None of the species they examined were free of contamination.

The fibers, Mason explained, get sluiced down the drain when synthetic fabrics, often made up of plastic, go through the wash. Washing machines don’t typically have filter traps and the tiny fibers also slip through wastewater treatment. Made of plastic polymers designed to resist environmental degradation, these fibers they do just that and persist in the environment, rather than degrading quickly as might bio-based fibers, like cotton or wool. Fish then ingest the fibers when they feed. When we eat those fish, we’ll be eating those fibers, too.

The fibers “get enmeshed in their G-I [gastrointestinal] tracts,” where they can pose physical and physiological hazards, explained Laura Kammin, pollution prevention specialist with the Ilinois-Indiana Sea Grant who worked with Mason on the study that documented fibers in Lake Michigan waters. If these fibers are so tiny–the National Oceanic and Atmospheric Administration (NOAA) defines “micro” to be 5 millimeters or less (around the length of a typical housefly)–why does it matter if fish are eating them?

As it turns out, these tiny fibers can pose physical hazards as they get ingested and lodged in the gut, the researchers say. And, as Chelsea Rochman, a postdoctoral fellow at the University of California Davis who specializes in microplastic pollution research, explains, this debris brings chemical contaminants that can potentially harm fish, among them endocrine disruptors, neurotoxins, and potential carcinogens. The plastics–whether fragments of larger plastics, microbeads or the fibers Kammin and Mason have found–are made of chemicals that, at any size, may pose health hazards to aquatic organisms and humans alike.

These microplastics also “act as a sponge” and can “transfer a cocktail of chemicals” to fish and other aquatic species, says Rochman. This means that these fibers and other plastic debris are also delivering chemical contaminants into our food web.

In their research off the California coast, Rochman and her colleagues have found metals (including lead and cadmium, known neurotoxins) and flame retardants–polybrominated diphenyl ethers (PBDEs)–that have been used widely in both hard plastics and upholstery foams and are known to be persistent pollutants. They have also found polycyclic aromatic hydrocarbons (PAHs), compounds associated with fossil fuels and a variety of adverse health effects, and PCBs (polychlorinated biphenyls). The researchers have also found evidence that plastic debris is affecting endocrine hormone activity in fish.

Other researchers on the East Coast and in the U.K. have found similar results in examining microplastics: evidence that such fibers and fragments had absorbed PBDEs, metals, PCBs and other contaminants that can be passed up the food web to humans. The European researchers also found microplastic fibers and fragments in commercially grown shellfish, including mussels and oysters destined for dinner plates. Eat one of those shellfish and you’ll be eating whatever that mollusk has.

Although she hasn’t published the research yet, Rochman says that she and colleagues have found microplastics in seafood sold in markets in the U.S. and Indonesia. The fish sampled from the U.S. market, she says, had plastic fragments and fibers in it–just like those found by the Great Lakes researchers. So it seems increasingly clear that if we want seafood free from chemical contaminants, we need water free of both invisible toxics and the ubiquitous plastic debris that’s acting as a pollutant delivery system.

Next steps for Kammin and Mason will be analyzing chemicals in the plastics they’ve found and their health effects. They also plan to expand their freshwater research to rivers and streams.

What can be done to stem the tide of this debris? The researchers think the solution will have to be upstream–where these fibers are getting into the water in the first place. Perhaps doing less laundry, they say. Or, we could all start wearing more natural fibers. But, more realistically, washing machine filters are probably needed. In the meantime, some of our seafood may come with a sprinkle of microplastic.

For more on this story go to: http://civileats.com/2015/01/15/how-microplastics-from-fleece-could-end-up-on-your-plate/#sthash.BJb67F7a.dpuf