The risk transfer pathways of toxic chemicals by food trade and logistics

Main text

Global food trade, driven by population growth and resource imbalances, has become a key vector for transferring persistent toxic chemicals (PTCs) across borders.¹ While alleviating resource pressures, this system shifts environmental degradation, directly exposing populations to PTCs, including pesticides, dioxins, methylmercury, and polychlorinated biphenyls (PCBs).^2,3,4,5 Current research prioritizes atmospheric/oceanic transport, yet food trade transfers PTCs 10-fold faster,⁵ as shown in the Europe-to-Africa PCB-contaminated fish trade.² However, origin-tracing gaps and fragmented regulations hinder risk mitigation.³ We highlight recent advances in quantifying trade-driven contamination pathways, identify policy gaps (e.g., harmonized standards, blockchain traceability), and propose potential governance strategies to address transboundary health disparities amid expanding trade and climate disruptions.

An emerging transport pathway of toxic chemicals

A rapidly growing population and economic globalization have driven increasing global crop and meat trade in recent decades, particularly among areas and countries with agricultural resource surpluses or deficits. Demand for crops and meat is significantly driven by the services and resources embedded within traded foods. The increasing need for environmental carrying capacities is another driver promoting rapid global food trade and logistics. For example, China consumed 8 million tons of beef and over 100 million tons of soybeans in 2018, of which approximately 1 million tons of beef and 94 million tons of soybeans were imported. As a result, food imports remarkably relieve the stress on land and water shortages and reduce environmental and climate impacts in China. While the associations between food trade and agricultural resources have been explored extensively, human exposure and health risks related to food trade and logistics are still poorly understood. Pesticides, fertilizers, additives, and antibiotics have been widely used in food production.¹ These chemicals often exhibit toxicity, persistence, and bioaccumulation, posing potential risks to both human health and ecosystems. Concern has been raised about whether toxic chemicals are delivered from their sources to receptors via the atmosphere, oceans, and transboundary rivers, where human food webs (the foods we consume) as “endpoints” of toxic chemicals are located. In this case, human exposure to contaminated foods is assessed at the endpoint of toxic substances. Figure 1 provides a schematic view of the atmospheric and food trade pathways.

Figure 1.

Schematic view of global atmospheric and food trade/logistics pathways

The yellow solid lines highlight major shipping routes of traded crops, meat, and other food items.

Endpoints of PTC-contaminated food

Extensive studies focus on the atmospheric and oceanic dispersion of toxic chemicals at varying scales (local to continental) to trace pollutant pathways reaching receptors. In contrast, modern food trade and logistics provide a new, direct, and increasingly important pathway via shipping that seems to be overlooked.^1,2,4 The source-receptor relationship of this pathway can be referred to as food “origin” (food exporting region) to “destination” (food importing region). The transport of a PTC through international food trade can be understood along three key dimensions. First, the concentration of a PTC in a given food commodity determines the contaminant load transferred from the exporting to the importing country or region. Second, the volume of food traded and consumed, particularly when contaminated, influences the magnitude of chemical exposure. Third, chemical-specific properties (e.g., persistence, lipophilicity) and food-type characteristics (e.g., fat content, processing level) jointly affect the bioavailability and biomagnification potential of the contaminant. PTC contamination originating from export regions thus poses health risks that are ultimately borne by consumers in importing regions. Mitigating this transboundary hazard requires that global food safety assessments incorporate not only the chemical identity and food matrix properties but also the geographic origin of production within the exporting jurisdiction as a critical factor.

The question now is: Which pathway is more efficient? Atmospheric transport of a pollutant is subject to atmospheric circulation patterns (winds), dispersion (turbulence), and degradation.³ However, food undergoing commercial shipping does not experience significant dispersion or degradation. A recent study demonstrated that health risks from dioxins transported via atmospheric pathways are significantly lower than those embodied in globally traded pork.⁵ Further analysis estimates that annual PTC transfer via food trade (1,200 metric tons) surpasses atmospheric transport (120 metric tons) by 10-fold, based on 2020 global meat trade volumes.⁵ Due to limited atmospheric exchange between hemispheres, international food trade (e.g., beef, crops) serves as a significant pathway for inter-hemispheric transfer of toxic chemicals. For example, 84% of PCB-153 exposure in African fish consumers stems from European imports, a major historical PCB source.² African per capita PCB intake from imported fish is 2.3 times that in Europe, despite lower consumption, with risk transfer primarily driven by trade.

The shipping cost is often a top priority in food trade and logistics, which drives food imports from the nearest place of origin. Food produced in those origin places with higher chemical levels often yields higher risks, which, however, are neglected. A recent modeling study designed an optimal food transportation pathway that considers food origins, logistics, and risk simultaneously. The results identified high risk for consumers in polluted coastal zones and switching to remote, low-contamination seafood would reduce risk. Despite higher logistics costs, accounting for health savings yielded net economic benefits.

Tracking contaminated food from its origin

Contaminated food products under trade are strongly dependent on their origins. This poses a new challenge in predicting contaminated foods and corresponding health risks embodied in trade at food origins or starting points. Differing from the assessment of the PTC-contaminated food web at the endpoint (receptor) of its airborne transport via a bottom-up (source-receptor) approach, tracking contaminated food from its origin to destination in a food importing country depends on reliable information about where the food is produced (food origin inspection), the local PTC emissions and environmental quality in the food origin (clean or polluted), and the extent to which the imported food is contaminated by the PTC at its origin.² Picking up information about food origins is the most challenging task in the rapidly expanding food trade and logistics, particularly in many less-developed countries.

Emerging evidence highlights global food trade as a prioritized pathway for PTC transfer, surpassing atmospheric and oceanic routes in efficiency and directness. Enhanced origin transparency enables systematic assessment of this emerging contamination route, which is projected to dominate food safety risks amid expanding trade networks. We propose a paradigm shift in risk assessment frameworks by integrating food logistics with traditional atmospheric models, emphasizing that trade-driven PTC transfer constitutes a primary, rather than secondary, exposure driver for import-dependent regions.

Policy implications and future directions

Addressing the transfer of PTCs through global food trade requires coordinated policy innovation. Harmonizing international food safety regulations (e.g., unified pesticide limits under WHO) is critical but faces challenges from divergent national capacities, industry resistance, and enforcement gaps. A practical pathway involves gradual regional adoption of standards, supported by technical and financial assistance for vulnerable economies. Enhancing transparency could be achieved through mandatory labeling of priority PTC levels (e.g., PCBs, dioxins, methylmercury) in imported foods, supported by blockchain technology. Additionally, addressing transboundary risk disparities demands binding multilateral agreements. Sub-Saharan Africa’s reliance on PCB-contaminated fish imports from Europe highlights the need for treaties to regulate such transfers.² By integrating technology, governance, and sustainability, the global food system can advance toward safer and more equitable trade practices.

Funding and acknowledgments

This study was supported by the National Natural Science Foundation of China (U21A2038, 42407134) and the National Key R&D Program of China (2023YFE0112900).

Declaration of interests

The authors declare no competing interests.

Published Online: August 27, 2025