III. PLASTICS ARE ALSO DANGEROUS BECAUSE OF THE CHEMICALS THEY CONTAIN, WHICH IMPOSE EXORBITANT COSTS ON SOCIETY
A. PLASTICS ARE SOURCES AND VECTORS OF WORRYING CHEMICALS
· Plastics are sources of chemicals
Plastics production involves many chemicals at different stages in the manufacturing process. They can be categorised into four groups: starting substances, i.e. monomers and catalysts; additives added to these products to make them functional (plasticisers, anti-oxidants, flame retardants, colourants, etc.); manufacturing aids used to facilitate the production of plastic materials and products; non-intentionally added substances (NIAS), which are either impurities from other chemicals, byproducts formed during the manufacture of plastics, or byproducts of degradation that appear during their use or at the end of their life.
· A very large number of chemicals, a quarter of which are dangerous
More than 16,000 chemicals are listed in the PlastChem database23(*).
Four criteria have been adopted to determine chemicals' hazard: their persistence, in order to identify chemicals that do not break down easily in the environment; their capacity for bioaccumulation, referring to chemicals that accumulate in the human body or in other organisms; their mobility, which targets chemicals that spread easily in the environment and in drinking water; and their toxicity, to assess their danger to human health.
More than 4,000 of the 16,000 chemicals listed, i.e. a quarter of them, can be classified as hazardous. Their toxicity to the environment, particularly the aquatic environment, as well as to human health, has been well documented scientifically. Numerous studies have shown that these chemicals are toxic to certain organs, such as the liver, and that they are carcinogenic, mutagenic or reprotoxic. Some chemicals are endocrine disruptors.
A general scientific review24(*) has looked at the impact on health of three chemicals used almost exclusively in plastics: polybrominated diphenyl ethers (PBDEs), used as flame retardants in fabrics and electronic products and classified as persistent organic pollutants by the Stockholm Convention; bisphenol A (BPA), a monomer used in the manufacture of polycarbonate as well as in the composition of epoxy resins used to coat food tins and cans; and phthalates, especially DEHP - bis(2-ethylhexyl) phthalate used to make plastics more flexible.
This general review was based on data from nearly 1,000 meta-analyses from 52 systematic reviews, representing the equivalent of 1.5 million data points.
It found solid epidemiological evidence linking foetal exposure to PBDEs during pregnancy to low birth weight, delayed or impaired cognitive development in children and loss of intelligence quotient (IQ). Statistically significant evidence of endocrine disruption linked to the functioning of the thyroid hormone system in adults has also been found.
As for BPA, the general review establishes connections with genital malformations in newborn girls exposed to BPA in the uterus, type 2 diabetes in adults and insulin resistance, as well as polycystic ovarian syndrome in women. Exposure to BPA also increases the risk of obesity and hypertension in both children and adults, as well as the risk of cardiovascular disease in adults.
Finally, the general review establishes links between exposure to DEHP and miscarriages, genital malformations in newborn boys, delayed or impaired cognitive development in children, loss of IQ, delayed psychomotor development, early puberty in young girls and endometriosis in young women. Exposure to DEHP also has multiple effects on cardiometabolic health, including insulin resistance, obesity and increased blood pressure.
· Shortcomings in the assessment of chemicals lead to their danger being underestimated
Only 161 plastic chemicals have been deemed non-hazardous by national regulations, but these assessments lack scientific rigour insofar as they are based either on incomplete information or on only a portion of the hazard criteria.
There is no data on the danger posed by 10,000 chemicals used or present in plastics.
Internationally, only 6% of chemicals are regulated under the Basel Convention, the Stockholm Convention and the Montreal Protocol.
Additionally, while chemicals' toxicity is beginning to be well documented, information on their persistence, bioaccumulation or mobility is more difficult to find, as these criteria are not always included in government assessments.
Finally, the determination of the thresholds below which the migration of chemicals or their absorption remains tolerable depends on scientific data that is subject to significant change. For example, until 2023 the threshold value considered tolerable for bisphenol A in the blood was 233 micrograms per litre, defined according to a target corresponding to renal toxicity. Then a new test appeared, based on the quantity of certain immune cells in the spleen. As a result, the European Food Safety Authority (EFSA) revised its tolerable daily intake for bisphenol A to 0.011 micrograms per litre, which is 20,000 times less than before.
· The population is widely contaminated by plastic chemicals
Chemicals enter the environment and contaminate it throughout the plastics life cycle. This pollution in turn affects humans, particularly through food, water and air.
A recent study25(*) showed that 25% of the 14,000 chemicals contained in plastic materials in contact with food have been found in the human body. Another publication26(*) bringing together the results of studies published between 2020 and 2022 concludes that 61 substances contained in plastic materials in contact with food are potentially carcinogenic to the mammary gland.
For the four most common perfluorinated compounds, which are widely acknowledged to be toxic, the tolerable threshold value for absorption, translated into a threshold value for the blood, has been set at 6.8 micrograms per litre. A major European programme assessed the overall level of contamination in European populations and found that 15% of the European population exceeded this threshold value. This does not mean that there is an immediate danger, as the threshold value is quite protective, but it does serve as a warning.
As far as the presence of BPA in our bodies is concerned, practically the entire population is above the tolerable threshold since the threshold value was drastically lowered in 2023.
· Plastics are also vectors for chemicals
Hydrophobic plastics will adsorb hydrophobic chemical pollutants present in the environment, not only allowing them to disperse but to pass through barriers that they would not normally be able to cross.
This 'Trojan horse' effect is exacerbated by plastics' persistence in the environment and their slow decomposition into micro and nanoplastics, which encourages the accumulation of chemicals in the physical environment and in organisms.
Examples include the interactions observed in the laboratory between plastic particles and benzopyrene, a highly toxic polycyclic aromatic hydrocarbon (PAH) and a major air pollutant. Exposure of cells to benzopyrene-contaminated plastic particles allows benzopyrene to penetrate into the cells. In addition, a pro-inflammatory response was observed in cells exposed to particles coated with this pollutant, whereas benzopyrene alone and plastics alone did not induce this effect.
It therefore seems that there is a very specific effect of benzopyrene particles in combination with plastics, the mechanisms of which have yet to be analysed.
* 23 Martin Wagner et al., State of the science on plastic chemicals - identifying and addressing chemicals and polymers of concern, 2024.
* 24 Christos Symeonides et al., « An umbrella review of meta-analyses evaluating associations between human health and exposure to major class of plastic-associated chemicals », Annals of Global Health, 2024, Volume 90.
* 25 Birgit Geueke et al., « Evidence for widespread human exposure to food contact chemicals », Journal of Exposure Science and Environmental Epidemiology, 2024.
* 26 Parkinson et al., « Potential mammary carcinogens used in food contact articles: Implications for policy, enforcement, and prevention », Frontiers in Toxicology, 2024.