The first study of the effects of plastic on the stomach tissue of seabirds has encountered a new condition, which the discoverers named "plasticosis". Although not immediately fatal, the condition threatens birds’ capacity to obtain the nutrients they need to grow, and eventually to survive. Although Bond and co-authors are the first to describe plasticosis, its progression and effects are familiar from both human and animal diseases. Ingested plastic inflames the stomach lining, which forms scar tissue as a result. Despite our adaptability to temporary inflammation, vertebrates seldom cope so well with ongoing attacks. Repeated scarring at the same site leads to fibrotic disease, which damages the flexibility of the tissue and the stomach’s capacity to digest food.
The name plasticosis has been used before for a very different condition – the breakdown of plastics deliberately inserted during joint replacements. However, the term never became widespread. Consequently, the discoverers of the new condition considered the word available to describe what they had found, and the similarities of the scars to those seen in asbestosis and silicosis make the name appropriate.
Even birds that look healthy can have digestive tracts scarred by small pieces of plastic.
The quantity of plastic in the oceans is rising so fast that by one calculation there will be more of it there by 2050 than fish. Although biologists are certain the consequences of all that indigestible material floating around will be dire, we’re still only starting to understand the ways in which the effects are felt.
Dr Alex Bond of the UK Natural History Museum is co-author of a study that looked at the effects on the stomach tissue of wild birds, something he says has never been investigated in this way before. The results are published in the Journal of Hazardous Materials.
Shearwaters are particularly vulnerable, because they mistake small pieces of floating plastic for food. plastic causes major scarring of the proventriculus, the first chamber of the shearwaters’ digestive system.
The consequences are most severe in young birds whose stomachs have not yet fully grown.
The damage can spread. "The tubular glands, which secrete digestive compounds, are perhaps the best example of the impact of plasticosis," Bond explained in a statement. "When plastic is consumed, these glands get gradually more stunted until they eventually lose their tissue structure entirely at the highest levels of exposure."
The glands play an important role in the birds’ immune system, as well as their capacity to absorb vitamins.
The authors previously found birds with more plastic items were more likely to have stunted growth.
Shearwater numbers are in decline at Lord Howe, and it would hardly be surprising if plastic is to blame.
Many birds deliberately ingest stones to help with the process of breaking down their food supply. The shearwaters consume pumice, possibly for the same reason. Pumice alone does not damage their digestive systems, but it appears to exacerbate the risk of scarring by breaking down the plastic.
Bad as the effects on the shearwaters’ digestive systems are, they may be just the tip of the iceberg. The team have found microplastic particles in the birds’ spleens and kidneys, and fear they may also be damaging the lungs.
The paper is published open access in the Journal of Hazardous Materials.