Marine litter has become a global concern because untreated solid and liquid waste increasingly ends up in the oceans, says Satish Sinha of Toxics Link.
Sinha says plastics, hazardous chemicals and microplastics can affect marine biodiversity, enter food chains and raise concerns for human health.
Better waste management, safer plastics and stronger systems to collect and process difficult-to-recycle materials are essential to addressing the problem, he says.
Marine litter is emerging as a major environmental and public health concern, as waste generated on land and at sea increasingly ends up in the oceans. Satish Sinha, associate director at environmental nonprofit Toxics Link, says the problem is not limited to visible plastic waste, but includes hazardous chemicals, microplastics and poorly managed packaging that can affect marine biodiversity and enter the food chain.
He talks to Down To Earth on why marine litter has become a global concern, what is known about its impact on ecosystems and human health, and why better waste management and safer plastics are central to any solution.
Akshit Sangomla (AS): Why is marine litter a topic of discussion in India and globally right now?
Satish Sinha (SS): It is interesting that marine litter has come to the forefront now. A lot of things have happened. Essentially, most of the waste we generate — including liquid and solid waste — finally ends up in the oceans. The ocean is the biggest sink we have for all the waste that has not been treated.
In the last 10-15 years, we have realised that litter has become a huge problem for the marine ecosystem and for the planet as a whole. Globally, this has also been recognised as a major problem.
The idea that we may see more plastic than fish in the oceans is a popular statement that is often heard, and it could become true if we do not mend our ways. We could lose fish populations, or fish populations could become contaminated. This is the kind of marine litter challenge we have in front of us.
AS: What are the major impacts of marine litter on biodiversity?
SS: One of the major sources of marine pollution is hazardous chemicals, such as persistent organic pollutants. We understand their impacts to an extent. But marine litter, such as plastic, also contains some of these chemicals as additives, apart from the microplastics that get diffused in the oceans through currents and sometimes settle on the ocean floor.
Organisms such as zooplankton tend to consume a lot of microplastics, mistaking them for food because of their size. The chemicals adsorbed by microplastics can enter organisms in this way. These organisms are then eaten by other organisms, and microplastics can get biomagnified through the food chain.
This is a huge problem because the chemicals absorbed by these microplastics are known for their toxicity. Food-chain contamination is a serious issue. It can also alter the behaviour of marine organisms.
AS: How pervasive are microplastics in the environment, and what are their impacts on human health?
SS: Microplastics are pervasive in the environment today, which was not the case earlier. They have been studied since the early 2000s. The data and research show that microplastics are present everywhere — in food, water, soil, various organs of the human body and in blood.
On average, one cubic metre of seawater contains 100,000 particles of microplastics. Microplastics are known to enter the stomach and cause irritation and digestive issues. They also enter the lungs through the air we breathe, though the exact impacts are yet to be scientifically concluded.
Some impacts are known, but confirmed evidence and the cause-and-effect relationship have not yet been fully established.
AS: Why is there a lack of conclusive studies on the impacts of microplastics on human health?
SS: Studying human health is complicated. Studies on other biota are easier, and those findings are then correlated with human health. Directly studying the impacts of microplastics on human health is difficult.
There are studies which suggest that many of these chemicals have adverse impacts on laboratory animals. The same could possibly be true for human beings as well. Some studies are now being taken up using computer simulations, which could act as empirical evidence to suggest that microplastics have health impacts on humans.
It is also easier to find out how much lead or mercury is present in the human body than to determine the concentration of microplastics.
AS: What kind of solutions are being adopted to manage marine litter?
SS: Some initiatives were taken a long time ago, especially on ocean-related litter. In 1973, there was a treaty called MARPOL for marine pollution. It was aimed at reducing pollution in the oceans due to shipping and tourism.
There have been many other international initiatives. In 2019, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services looked at marine pollution from a biodiversity perspective. There is also the Plastics Treaty process, which addresses many concerns around marine litter.
Another important aspect is the solid-waste management scenario across countries, especially in geographies close to coastlines. We should also look at improving the quality of the plastics we use. If plastic has less toxicity and fewer hazardous chemicals, it becomes less problematic to deal with.
If we are able to address most waste-management issues, we will have a better marine environment.
AS: Are certain types of plastic more difficult to manage, while others are easier?
SS: Many of us feel that all plastics are manageable, but some are extremely hard to manage.
If we talk about multi-layer plastics, or thermoset plastics such as Bakelite, which is used in utensil handles and cannot be remoulded, these are extremely difficult to recycle. Another category is single-use plastic, such as polyethylene and polypropylene. These are comparatively easier to recycle, but difficult to collect.
Then there are multi-layered plastics made of composite materials, used primarily for packaging, which also do not have a clear management solution. The packaging we use is too difficult to process, so we dispose it through poor processing. The percentage of poorly processed plastic has been increasing in recent years.