Recently, the scandal of tankers mixing cooking oil with fuel during transport sparked public outrage, once again striking a nerve on food safety and public health. In reality, food-borne safety hazards have long been lurking.
In March of this year, a study published in Nature Communications, titled “Serum Exposure Profiling Reveals Risk of Chronic Diseases in Chinese Populations”, found that 74 environmental hazardous chemicals – pesticides, insecticides, veterinary drugs, plastic degradation products and more – were frequently detected in the serum of the Chinese population, with multiple correlations to chronic disease.
As ordinary people concerned about food safety, what is worth knowing about this study? I.Research CredibilityA powerful research team: The study was conducted jointly by institutes, colleges and research centres under the Chinese Academy of Sciences, the University of Chinese Academy of Sciences, the Liaoning Provincial Key Laboratory of Metabolomics, the State Key Laboratory of Environmental Health, Huazhong University of Science and Technology, China Medical University and the Chinese Centre for Disease Control and Prevention, among others. Broad coverage of study subjects: The study covered 5,696 residents across 15 Chinese provinces – 2,141 healthy individuals and 3,555 patients – and examined links to 12 chronic conditions, including diabetes, hyperuricaemia, obesity, hypercholesterolaemia, hypertriglyceridaemia, metabolic syndrome, elevated diastolic blood pressure, elevated systolic blood pressure, abdominal obesity, hypertension, elevated LDL cholesterol and hyperlipidaemia.
Most chemicals screened simultaneously: Using gas chromatography–mass spectrometry, researchers detected residues of 267 chemicals in blood samples, including pesticides, insecticides, veterinary drugs, plastic degradation products and plasticisers.
II.The 267 Chemicals Detected in Human Serum and Their Sources
The 267 chemicals include insecticides, plastic degradation products, veterinary drugs, pesticides and plasticisers, of which 74 compounds showed high exposure levels in the population, detectable in the blood samples of more than half the volunteers.
● The 267 substances tested in the study and the 74 most frequently detected.The 97 compounds prioritised for analysis by the researchers include organochlorine compounds (organochlorine pesticides), organophosphate compounds (organophosphate pesticides), herbicides, insecticides, fungicides, veterinary drugs, food additives, polychlorinated biphenyls, polycyclic aromatic hydrocarbons and phthalates. In other words, they are closely tied to China’s agricultural production and people’s everyday dietary choices. III.Certain Organochlorine and Fluorinated Chemicals Are Closely Linked to Increased Chronic Disease Risk in ChinaAmong them, organochlorine pesticides (OCPs) are associated with hypertension, diabetes, metabolic syndrome and obesity, while per- and polyfluoroalkyl substances (PFASs) are linked to hyperlipidaemia, obesity, metabolic syndrome and hyperuricaemia.
● DDT is continually concentrated in the food chains formed by aquatic organisms and birds; after several trophic levels of amplification, concentrations in organisms can reach ten million times those in the water. Source: biologywise.com
► Organochlorine Persistent Organic Pollutants
Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are persistent organic pollutants in the environment. Their high toxicity, persistence, bioaccumulation potential and ability to travel long distances enable them to concentrate and magnify through the food chain in living organisms, causing adverse effects such as immune dysfunction, reproductive harm and endocrine disruption.
For humans, at the top of the food chain, these toxic effects can be magnified by as much as seventy thousand times. Although China continues to update its bans and restrictions on chemicals – OCPs and PCBs having been banned for years – their environmental accumulation remains a matter of serious concern.
● Products such as raincoats, fire extinguisher powder, electronics, fast-food packaging boxes and non-stick pan coatings all contain PFASs.
► Per- and Polyfluoroalkyl Substances (PFASs)
Per- and polyfluoroalkyl substances (PFASs) are widely used in industrial production, including food packaging, cutlery coatings and stain-resistant furniture. Humans are exposed to PFASs daily, primarily through drinking water and food, consumer products containing PFASs, and occupational exposure during the manufacture of related products. PFASs exhibit liver and kidney toxicity, immunotoxicity, reproductive toxicity, metabolic disruption, neurotoxicity and carcinogenicity, and can cause a wide range of adverse health effects.
IV. OCP and PFAS Residues in Chinese Populations Are Markedly Higher Than in Other Countries
Since the 1970s and 1980s, countries around the world began restricting highly toxic organochlorine pesticides, gradually phasing them out by banning their production, sale and use. China, however, did not officially ban organochlorine pesticides until 2002 – a reality closely linked to the country’s agricultural development needs. Since the 1950s, 4 million tonnes of BHC and over 500,000 tonnes of DDT had been used, contaminating 13.3 million hectares of farmland. By the time DDT was banned in the 1990s, China’s DDT usage alone accounted for more than 20% of the world’s cumulative total.
Most PFASs show the highest serum concentrations in China and South Korea, while a small number of PFASs reach peak concentrations in human serum in the United States and Canada. This pattern is closely tied to the shift in manufacturing from North America and Europe to emerging Asian economies since 2002. V. Harmful Compound Detection Rates Are Highest in Coastal Populations in Eastern China● Left: serum compound residue levels across 15 provinces – the darker the colour, the higher the residue. Right: veterinary drug and other pharmaceutical residues among the screened populations in the 15 provinces are also substantial.The study found that PFASs were most frequently detected in the populations of Jiangsu, Zhejiang and Shanghai, while OCPs were most commonly found in Shanghai, Jiangsu, Hubei and Chongqing. This may be related to these regions’ relatively developed economies, high degree of industrialisation, proximity to major rivers and abundant edible aquatic products. Notably, serum residues of various chemicals were highest among populations in the Yangtze River Delta. A possible explanation is that persistent organic pollutants cannot be effectively separated from wastewater and are transported downstream via groundwater and surface runoff. Among the study’s sample, the populations of Shaanxi and Guizhou showed the lowest serum chemical residue levels, possibly attributable to lower population density and less developed industry in those areas.
VI.Older People Accumulate More Harmful Environmental Chemicals in Their Blood
Age is the second most important factor explaining differences in exposure, possibly related to variations in cumulative exposure duration and metabolic capacity across age groups. The study found that most chemicals, such as OCPs and PFASs, accumulated in human serum at higher levels with increasing age. In particular, beta-BHC (used in the production of the pesticide Lindane), p, p′-DDE, pyrene (an insecticide ingredient) and indole-3-butyric acid (IBA, a plant growth regulator) all increased with age, reaching the highest concentrations in those over 70. PFAS concentrations also rose with age, peaking around the age of 50.
Conversely, the concentrations of some compounds showed an inverse relationship with age. Children under 10 had the highest serum residue levels of cyclamic acid (a metabolite of cyclamate) and acesulfame potassium, which may be related to their consumption of processed foods and drinks containing sugar substitutes.● Two pear paste drinks from the same brand: the children’s version contains sugar substitutes such as cyclamate and acesulfame potassium, while the regular version actually has a cleaner ingredient list.
VII. Education Level, Income Level and Gender Affect Chemical Residues in the Body
The study found that the higher the level of education and income, the greater the residues of harmful chemicals such as polycyclic aromatic hydrocarbons, OCPs and polychlorinated biphenyls. Women had significantly higher OCP levels than men, while PFAS and phthalate (plasticiser) levels were notably lower. The chemicals most affected by gender were beta-BHC (Lindane), monocyclohexyl phthalate (MCHP) and perfluorooctane sulfonate (PFOS). Gender thus emerges as an important factor influencing the accumulation and metabolism of chemicals in the body, likely linked to differences in body fat proportion and occupational exposure patterns.
VIII. Chemical Mixtures Pose More Significant Health Risks Than Single Substances
● A UK study found that multiple chemical residues were detected not only in everyday food but also in soil, rivers and pollinating bumblebees – none escaping the “cocktail effect”. Source: Pesticide Action Network UK
The study analysed the associations between exposure mixtures and chronic diseases. Results showed that three exposure mixtures produced significant enhancement effects on hyperuricaemia, hyperlipidaemia and metabolic syndrome – a finding not previously reported. The “cocktail effect” of chemicals warrants in-depth investigation.
Future research is recommended to focus on these chronic diseases and the relevant exposure mixtures: priority risk-control chemicals, primarily organochlorine pesticides (OCPs), per- and polyfluoroalkyl substances (PFASs), phthalates and other pesticides (see figure below).
The research has demonstrated a high degree of association between specific chemical groups and common chronic diseases, but this does not imply a definitive causal relationship – further in-depth toxicological and epidemiological studies are still needed. What is beyond doubt, however, is that these findings will provide guidance for future pollution management and the protection of susceptible populations. IX.Pesticide Residue Risks Spread Like Ripples, Lingering IndefinitelyBeyond OCPs and PFASs, this study did not elaborate on the health risks of other pesticides, because the chemical classification of pesticides is as complex as their dosage forms, formulations and chemical compositions, making it difficult to group them into broad categories as one would with OCPs and PFASs, unless targeted correlation studies are conducted. The neurotoxicity, liver toxicity, and acute or chronic toxicity with irritant effects of pesticides may, to varying degrees, lead to cancer, malformations and genetic mutations in organisms – highly hazardous pesticides (HHPs) being a case in point.
But does banning highly toxic organochlorine pesticides mean the problem is solved?
To reduce the environmental impact of traditional organochlorine pesticides, several new types of lower-toxicity organochlorine pesticides have emerged in recent years. Yet studies have also found that these new organochlorine pesticides are widespread across multiple environmental media – including soil, aquatic sediments and surface water – still posing considerable ecological risks and potentially harming human health.
For example, the degradation products of diphenamid in water are highly hazardous; the production of dicofol generates DDT as a by-product, which, once dispersed into the environment, may affect infant health; and methoxychlor suppresses mating behaviour in male quail. We must take the ecological and health risks of new organochlorine pesticides seriously.
Afterword
Scientific and technological progress has enabled humanity to produce an endless stream of novel chemical substances. Whatever the original intentions, the reality is that a vast number of chemicals have been proven harmful to the environment and to human health, and people are inevitably exposed to them. To eliminate harmful risks to the greatest extent possible, the United Nations established the three international chemicals and waste management conventions.
Among the vast array of chemicals, the risks posed by highly hazardous pesticides have attracted particular attention.
In 2015, the Fourth International Conference on Chemicals Management (ICCM-4) once again adopted a resolution recognising highly hazardous pesticides as an issue of international concern and calling for concerted action to address the problem. Shortly after, the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) jointly published the Guidance on Highly Hazardous Pesticides in 2016.
Pesticide regulation has also gradually been incorporated into the biodiversity conservation agenda. In 2022, both the State Council General Office’s Action Plan for the Governance of New Pollutants and the Kunming-Montreal Global Biodiversity Framework, adopted under the Convention on Biological Diversity, explicitly included pollution governance in their action plans.
As a major agricultural nation, China faces particularly direct health and environmental consequences from pesticide exposure among its agricultural producers – the end users themselves. Pesticide users must therefore first break free of a “pesticide-only” mindset in their approach to crop pest control, seeking integrated pest management while strengthening personal protection and reducing the indiscriminate, excessive and overuse of pesticides.
To reduce the environmental and health risks of harmful chemicals, countries establish their own maximum residue limits (MRLs) for pesticides in accordance with the WTO Agreement on the Application of Sanitary and Phytosanitary Measures (the SPS Agreement). These standards serve as a key technical benchmark for assessing the safety and quality of agricultural products, as well as a baseline for environmental and public health protection.
Producers must strictly comply with national pesticide restrictions. Regulators should conduct relevant outreach and provide technical training on pesticide alternatives, managing and controlling health and environmental risks at source. Consumers need to be aware of pesticide residues and should abandon the pursuit of cosmetically perfect produce, actively exploring alternative consumption choices, taking care with every humble meal on the table, and supporting practical measures to reduce pesticide risks from field to fork.
Foodthink authorDou HongDeputy Secretary-General of the Yunnan Green Environment Development Foundation. Holds an undergraduate degree in wildlife conservation and utilisation, a master’s degree in forest conservation, and a PhD in animal ecology from Yunnan University. Initially aspiring to become a naturalist, cross-industry work experience that spanned landscapes from the poles to the equator ultimately led to a career in the social sector. Has long been engaged in research, public education and training, and project and organisational management related to biodiversity conservation, biological resource protection, ecological agriculture development and the reduction of hazardous chemicals. Brings extensive experience in project organisation and implementation, and enjoys the intellectual stimulation of diverse perspectives and cross-disciplinary thinking.Editor: Zeen
