Plastics in agriculture and food production: uses, properties, and impacts - Results of the INRAE-CNRS collective scientific assessment

Plastics have shaped modern food value chains

At present, food packaging is the main reason plastics are used in agricultural and food systems. In France in 2023, agriculture and food production accounted for 20% of all plastics used: 91% of usage was associated with food and beverage packaging, and the other 9% of usage occurred in agricultural settings. In this latter category, 73% of usage was linked to livestock farming systems.

Plastics are used to protect, preserve, transport, and market food products (i.e., package design and labelling). Plastics are a solution to both regulatory constraints and the needs of economic stakeholders in the supply chain (e.g., lighter weight, greater robustness, lower cost). The majority of agricultural uses occur on livestock farms (fodder conservation); the remainder occur in horticultural systems (e.g., mulch, tunnel greenhouses). The increase in plastic use has largely been driven by corporate strategies rather than by consumer demand.

Plastics spread widely within food production systems after World War II as a result of marketing efforts by the petrochemical industry and the demographic growth and urbanisation that followed World War I. Plastics were instrumental in building 20th-century distribution and sales systems, facilitating the development of long distribution chains and greenhouse farming. A symbol of modernity, plastics transformed consumption patterns and even the very nature of certain foods, contributing to an emerging culture of disposability.

Why are plastics so compositionally complex and diverse?

When it comes to agriculture and food production, research has focused on plastics' mechanical properties, radiometric properties (i.e., transmission, reflectance, or absorption of solar radiation), and ability to act as gas and liquid barriers. The desire to combine sometimes incompatible properties has led to even more complex compositions, as different additives come into the mix or multi-material products are generated (multi-layer materials, alloys, or composites). An example can be seen in agricultural films, whose complexity has been increased to boost durability under long-term environmental exposure. However, research indicates that additional field trials, rather than laboratory trials, are needed to assess the effectiveness of plastics under real-life conditions; the results could help better meet actual needs. Biobased plastics are made entirely or partially from biomass. For example, polylactic acid (PLA) is made using maize. Although they are increasingly the focus of scientific studies and R&D projects, biobased plastics accounted for no more than 1.5% of the plastics produced in France and Europe in 2023. Their composition is often just as complex as that of traditional plastics; frequently, petroleum-based additives or polymers are included to achieve properties similar to those of petroleum-based plastics.

On top of these additives, plastics contain residual substances stemming from the manufacturing process as well as non-intentionally added substances (NIASs), contaminants that accumulate over the course of use at the interface between the plastic and the environment. As a result of the above and because of industrial secrecy, users are often left in the dark about the final composition of plastics.

Plastic waste management and recycling

Most plastics can be recycled, but few actually are. Worldwide, 64% of plastics end up in landfills. In Europe, 42% of plastics are incinerated, and 35% are sent to recycling. These figures are 33% and 35% in France, respectively. Little research has been conducted on methods for collecting and sorting plastics, even though both processes have a direct influence on recycling efficiency.

At industrial scales, recycling is mainly mechanical; the polymer chain is not modified. However, there are constraints related to material degradation, material contamination, and process cost-effectiveness. As far as food contact materials are concerned, only PET water bottles are recycled to create new PET water bottles, a process that is strictly regulated. Other food-grade plastics are recycled for use in different products because they no longer meet regulatory standards. Indeed, the recycling process requires the inclusion of more additives or even new plastics to maintain a product’s functional properties, and recycled plastics may contain contaminants. Because of their complexity, plastics are difficult to recycle, and there is no technology at present that allows them to be fully reused.

Certain plastics are supposed to be biodegradable but will only decompose under very specific conditions, which may be restricted to controlled industrial settings. Additionally, the presence of petroleum-based polymers and additives within biobased plastics complicates processing. The so-called biodegradable plastics biodegrade poorly under real-life conditions (in soils, home composting) and should be better labelled so they are managed in a way that actually spurs their biodegradation.

Is plastic contamination worse in soils than in oceans?

Plastics used in agriculture and food production are directly contaminating ecosystems. Throughout their life cycles, plastics are releasing compounds into the environment and are breaking down into different-sized particles, forming macroplastics (> 5 mm), microplastics (1–5 mm), and nanoplastics (< 1 µm).

All types of soils, even desert soils, are contaminated with microplastics (MPLs). Contamination rates in soils range from 100 to 10,000 MPL particles per kg in the top metre of soil. Agricultural soils are particularly affected. Research strongly suggests that the total MPL contamination of agricultural soils is greater than that of oceans. The sources of this contamination are agricultural practices that involve plastics, such as mulching, applying compost and liquid manure, and irrigating; there is also atmospheric deposition. However, given current knowledge, there is no way to quantify the exact contribution of each potential source.

MPLs create habitat for certain microorganisms that reduce soil microbial biodiversity. They also contaminate flora and fauna directly via their presence in the environment or indirectly via their transfer through the food chain, where contamination begins in soil organisms and plants.

Effects of microplastic contamination on human health and ecosystems

In animals, including humans, MPLs are found in most bodily organs, including the lungs, digestive system, human placenta, and fluids (e.g., breast milk). It was only recently discovered that nanoplastics can enter cells. At the molecular level, they induce oxidative stress and alter cell energy metabolism. These effects have been observed in distantly related taxa, underscoring that MPLs are a threat to all organisms within ecosystems. Preclinical studies have found that MPLs and nanoplastics can cause reproductive health problems, inflammation (colon), and fibrosis (liver, kidney, lung, heart). This work has established toxicity thresholds: as low as 20 µg/kg of body mass per day for various pathologies and organs and as low as 6.5 ng/kg of body mass per day for neurological conditions. MPLs also negatively affect livestock production (growth, milk production). Additionally, MPLs promote the adsorption of numerous substances, thus acting as "Trojan horses" for toxins such as heavy metals and chemical pollutants.

When it comes to human health, a large number of substances migrate from food contact plastics into foods. More than 10,000 substances are potentially present in food-grade plastics. Two categories have been extensively studied—phthalates and bisphenol A (BPA)—and are regulated within Europe. They are known endocrine disruptors. Additionally, numerous studies have demonstrated their universal toxicity to organisms, even at low doses. They particularly impact reproductive functions. BPA exposure increases the likelihood of developing cardiovascular disease, type 2 diabetes, and obesity. In Europe, these conditions result in estimated health care costs of several billion euros. EFSA has reported that the majority of Europeans are exposed to BPA at levels in excess of regulatory thresholds.

How could plastic use in agriculture and food production become more sustainable?

The use of plastics in agriculture and food production is inseparable from the use of plastics overall, hampering regulation and sustainability assessments. There are no regulations specific to plastics, whose use currently falls under three EU regulatory frameworks: those targeting food contact materials, chemical products, and waste management. In addition, these regulatory frameworks differ in scope when it comes to plastic use. Life cycle analysis (LCA) is the main tool being used to evaluate the sustainability of plastics. However, LCA is not a comprehensive methodology, and it generally does not address environmental impacts other than greenhouse gas emissions or the depletion of non-renewable resources.

The scientific community has clearly stated that plastic production must decrease. To date, strategies for managing plastics have prioritised recycling, which acts to treat rather than to prevent. Furthermore, given our current state of knowledge, the inclusion of virgin plastics is required for recycling to be successful. For example, because recycling is prioritised, less attention is paid to reuse strategies, and plastic usage remains entrenched, stalling major cultural transitions, especially in the way we eat. Even when accompanied by better collection or sorting methods, increases in plastic waste translate into increases in poorly managed waste. Potential alternatives like biobased plastics are nonetheless plastics, and their manufacturing, recycling, and disposal remains equally complex. Although tangible means for their implementation are lacking, strategies for reducing plastic use include education about the environmental impacts, greater limits on lobbying, and better enforcement of existing regulatory policies, such as the directive on single-use plastics, the anti-waste law for a circular economy, and the global plastics treaty that is currently under negotiation. Future research should focus on precisely identifying where plastics remain essential along the value chain, with a view to defining realistic solutions for reducing plastic production and use.