Recycled and reused food contact plastics are “vectors for spreading chemicals of concern” because they accumulate and release hundreds of dangerous toxins like styrene, benzene, bisphenol, heavy metals, formaldehyde and phthalates, new research finds.

The study assessed hundreds of scientific publications on plastic and recycled plastic to provide a first-of-its-kind systematic review of food contact chemicals in food packaging, utensils, plates and other items and what is known about how the substances contaminate food.

“Hazardous chemicals can accumulate in recycled material and then migrate into foodstuffs, leading to chronic human exposure,” the study’s authors wrote, noting bottles made from polyethylene terephthalate (PET) plastic as a common example.

The study comes amid a debate over how to reduce the amount of plastic waste filling up the globe. The petrochemical industry, some governments and many environmental groups have pushed for improvements to the recyclability of plastic.

Though some types of the material can be recycled, most cannot, and the study highlights how improving recyclability of the material comes with risks: it identified 853 chemicals used in PET recycled plastic and many of those have been discovered during the last two years.

The most commonly detected were antimony and acetaldehyde, while potent toxins like 2,4-DTBP, ethylene glycol, lead, terephthalic acid, bisphenol and cyclic PET oligomers were also most frequently found.

Moreover, the chemistries of plastics can be something of a black box. In the US, there’s very little regulation around what goes in the material and the EU only requires light testing to determine which chemicals are in plastic.

The study characterizes plastics as “very complex materials containing hundreds of different, synthetic compounds which are more often than not poorly characterized for their hazard properties”. Some chemicals found in recycled plastics cannot be identified, the analysis notes, adding to the risk of repeatedly recycling and accumulation.

“It’s not safe, and as the quality of recycled plastic decreases, the amount of potential contaminants goes up,” said Birgit Geueke, the study’s lead author and senior scientific officer with the Zurich-based Food Packaging Forum.

The data indicates chemicals are added or created during the recycling process. While 461 kinds of VOCs were detected in virgin plastic, some 573 were found in recycled material. Geueke said it was difficult to say why that occurred, but it could stem from the addition of chemicals during the recycling process, the addition of chemicals from the contaminated recycling stream, reactions among chemicals, or from plastic taking up additional chemicals when used the first time.

The review also highlighted widespread “illicit” recycling in which industry uses non-food grade plastic made with flame retardants and other toxic compounds in recycled food packaging. Despite strict regulations on which types of plastic can be used for food contact, studies identified recycled electronics in the US, South Korea and European markets.

“There are clear indications of brominated flame retardants that came from your old TV, computer, keyboard,” Geueke said. “It’s certainly not legal.”

The review identified similar problems with reusable plastic items for food contact, such as kitchen utensils, water bottles, tableware, baby bottles, water dispensers, tubing of milking machines and more.

Food from plastic’s first use or detergents used to clean the material can be absorbed and cause chemical changes and contamination in reused material, as can heating it or otherwise using it in a way it is not designed to be.

Consumers can protect themselves by avoiding plastic as much as possible, bringing non-plastic carryout packages to restaurants and moving food products from plastic packaging to containers made of safer materials.

But, ultimately, the most effective remedy is the elimination of plastic and the societal use of safer materials, the study’s authors wrote.

“A shift towards materials that can be safely reused due to their favorable, inert material properties could be a promising option to reduce the impacts of single-use food packaging on the environment and of migrating chemicals on human health,” the paper states.

A devastating 2005 flood that killed 1,000 people in the Indian city of Mumbai was blamed on a tragically simple problem: plastic bags had blocked storm drains, stopping monsoon flood water from draining out of the city.

Now a new report, attempting to quantify this problem, estimates that 218 million of the world’s poorest people are at risk from more severe and frequent flooding caused by plastic waste.

The number is equivalent to the population of the UK, France and Germany combined. About 41 million of those are children, older people and people with disabilities, the report found. Three-quarters of those most at risk live in south-east Asia and the Pacific region.

Researchers from Resource Futures, an environmental consultancy, and Tearfund, an international Christian charity, found that communities in Cameroon, Nigeria, the Democratic Republic of the Congo (DRC), Ghana, Bangladesh and Indonesia had experienced more severe flooding due to plastic waste blocking drainage systems in the last few years. In these communities, plastic waste was a “risk multiplier” for flooding, they said.

To identify those most at risk, they used a study of flood risk and poverty published in 2022 by Jun Rentschler and othersthat identified 1.8 billion people at high risk of flooding in 188 nations. They narrowed their analysis to only low and middle-income countries with inadequate urban drainage, solid waste management and sanitation. To focus on the populations most at risk from plastic exacerbating the flood risk, they also excluded countries with mismanaged waste of less than 1kg for each person a year, and focused on urban slums.

Rich Gower, a senior economist and policy associate at Tearfund, said: “Around the world, from Brazil to the DRC, from Malawi to Bangladesh, we see plastic pollution making floods worse. Without decisive action, this problem is only going to get worse.”

Plastic waste pollution has doubled in the last decade, and is predicted to triple by 2060. Only 9% is recycled globally.

Gower said: “The aim of the report is to give an order of magnitude to the number of people at risk. What we are saying is that plastic pollution affects the poorest, most marginalised communities the most. We’ve seen it with plastic burning, and we are now seeing it with flood risk. These communities bear the brunt of plastic pollution.”

The authors stressed the limitations of the estimate. It was based on the best available data, they said, admitting that “detailed data on impacts of plastic-aggravated flooding is not available”. Neither, they said, was there sufficient modelling of the links between plastic pollution, flooding and health. But they had applied “multiple conservative assumptions and sense-checks”, and considered the estimate “realistic and conservative”, they said.

Gower urged governments, which will come together in Paris next week to begin negotiations on a legally binding plastics treaty, to consider these worst-affected communities. “Through the plastics treaty, world leaders have a once-in-a-lifetime opportunity to end this crisis by driving down plastic production and making sure the rest is safely collected and recycled,” he said.

Brendan Cooper, a consultant at Resource Futures, said they used the Rentschler flood-risk study as a starting point. “We then broke that down to those more in line with plastic-aggravated flooding,” said Cooper. “We found urban areas have high levels of mismanaged waste.”

While the figures were estimated, he said, they were a “conservative” estimate.

Densely populated slums in south Asia, east Asia and Pacific and sub-Saharan Africa were likely to be experiencing the worst effects of plastic-aggravated flooding due to rapid, poorly planned development, with limited flood-mitigation infrastructure, the report found.

It showed that plastic pollution in slums in many low and middle-income countries was making flooding more severe by blocking drainage systems, resulting in health problems, including gastrointestinal diseases such as cholera and diarrhoeal disease.

The researchers excluded coastal communities and small-island developing states from the research, as coastal flooding is unlikely to be aggravated by plastic waste.

More than 1 billion people live in slums globally, and this is expected to reach 3 billion by 2050. The most commonly observed plastic items blocking drainage systems, the report found, were bottles, nylon threads from the fishing industry, plastic bags and sachets.

The study said the accumulation of plastic pollution could cause the water level to rise by one metre within the first hour of a flood.

Recycling plastic can make it more toxic and should not be considered a solution to the pollution crisis, Greenpeace has warned before the latest round of negotiations for an international plastics treaty.

“Plastics are inherently incompatible with a circular economy,” the global environmental network said in a report that brings together research showing recycled plastics are more toxic than their virgin constituents.

The report, timed to coincide with the beginning of fresh talks for a potential global plastics treaty, comes as separate research has found breaking down plastics for recycling scatters microplastic pollution into the environment.

Representatives from 173 countries last year agreed to develop a legally binding treaty covering the “full lifecycle” of plastics from production to disposal, to be negotiated over the next two years.

Next week they are due to meet in Paris, for talks that have already been criticised for excluding communities in developing countries harmed by dumping and burning of plastic waste, as well as marginalised waste pickers, who are crucial to recycling.

Without those voices, the fear is that negotiations will be swayed by corporate interests. “The plastics industry – including fossil fuel, petrochemical and consumer goods companies – continues to put forward plastic recycling as the solution to the plastic pollution crisis,” said Graham Forbes, who leads Greenpeace USA’s global plastics campaign.

“But … the toxicity of plastic actually increases with recycling. Plastics have no place in a circular economy and it’s clear that the only real solution to ending plastic pollution is to massively reduce plastic production.”

Since the 1950s about 8bn tonnes of plastic has been produced. The Greenpeace report catalogues peer-reviewed research and international studies showing not only that just a tiny proportion (9%) of plastics are ever recycled, but also that those that are end up with higher concentrations of toxic chemicals, multiplying their potential harm to human, animal and environmental health.

Recycled plastics, the report says, often contain higher levels of chemicals such as toxic flame retardants, benzene and other carcinogens, environmental pollutants including brominated and chlorinated dioxins, and numerous endocrine disruptors that can cause changes to the body’s natural hormone levels.

Waste plastics earmarked for recycling are typically exported from high-income countries to poorer parts of the world

Dr Therese Karlsson, a science adviser with the International Pollutants Elimination Network (IPEN), said: “Plastics are made with toxic chemicals, and these chemicals don’t simply go away when plastics are recycled. The science clearly shows that plastic recycling is a toxic endeavour with threats to our health and the environment all along the recycling stream.

“Simply put, plastic poisons the circular economy and our bodies, and pollutes air, water and food. We should not recycle plastics that contain toxic chemicals. Real solutions to the plastics crisis will require global controls on chemicals in plastics and significant reductions in plastic production.”

Plastic production is forecast to triple by 2060. Greenpeace said any global plastics treaty must achieve immediate significant reductions in plastic production, as a first step on a pathway to the total elimination of the manufacture of virgin plastic.

Those plastics that remain must be reused as far as possible, while waste disposal technologies are developed that do not involve simply burning it or burying it, Greenpeace said.

Recycling has been promoted by the plastics industry as a key solution to the growing problem of plastic waste. But a study has found recycling itself could be releasing huge quantities of microplastics.

An international team of scientists sampled wastewater from a state-of-the-art recycling plant at an undisclosed location in the UK. They found that the amount of microplastics released in the water amounted to 13% of the plastic processed.

The facility could be releasing up to 75bn plastic particles per cubic metre of wastewater, they estimated.

“I was incredibly shocked,” said Erina Brown, the lead researcher of the study, conducted at the University of Strathclyde in Glasgow. “It’s scary because recycling has been designed in order to reduce the problem and to protect the environment. This is a huge problem we’re creating.”

The researchers tested the water before and after the plant installed a water filtration system and found the filter reduced the amount of microplastics from 13% of the plastic processed to 6%.

The estimate of 75bn particles per cubic metre is for a plant with a filter installed. A majority of the particles were smaller than 10 microns, about the diameter of a human red blood cell, with more than 80% smaller than five microns, Brown said.

Microplastics, usually considered to be any particle of plastic measuring less than 5mm, have been found everywhere from freshly fallen snow in Antarctica to the depths of the ocean, and can be toxic for animals and plants.

The results also revealed high levels of microplastics in the air around the recycling facility, with 61% of the particles less than 10 microns in size. Particulate matter less than 10 microns has been linked to human illness.

The facility was a “best case scenario”, Brown said, given that it had made efforts to install water filtration while many other recycling plants may not.

“An important consideration is what other plants globally are emitting,” she said. “This is something we really need to find out.”

The study, published in the Journal of Hazardous Material Advances, suggests the recycling plant discharged up to 2,933 metric tonnes of microplastic a year before the filtration system was introduced, and up to 1,366 metric tonnes after.

“More than 90% of the particles we found were under 10 microns and 80% were under 5 microns,” said Brown. “These are digestible by so many different organisms and found to be ingested by humans.”

“For me, it highlights how drastically we need to reduce our plastic consumption and production.”

Globally, only about 9% of the 370m metric tonnes of plastic produced gets recycled.

Judith Enck, a former senior official at the US Environmental Protection Agency, who now leads Beyond Plastics, a lobby group, said: “The findings are disturbing but not surprising. This one recycling facility, a state-of-the-art facility, demonstrates the serious problem of using plastics. It causes serious problems, even in terms of the infrastructure to recycle plastics. It is a clarion call to use less.”