You track your calories. You grill your chicken instead of frying it. You swap refined oil for cold-pressed canola. You eat your vegetables. By every visible metric, you are eating well. And yet, in the precise moment that the meat fat drips onto the hot grill plate and sends up a curl of fragrant smoke — or when the mustard oil reaches its smoking point in the kadai — a class of chemical compounds is forming that your nutritional tracker will never record and your recipe book will never mention.
They are called polycyclic aromatic hydrocarbons, or PAHs. And a growing body of rigorous food toxicology research confirms they are hiding in plain sight — not merely in junk food or industrial processing, but in the daily cooking of foods we consider wholesome: grilled meats, smoked fish, roasted vegetables, and the cooking oils we use to prepare them all.
What Are PAHs and Why Should You Care?
Polycyclic aromatic hydrocarbons are a family of hydrophobic organic compounds characterised by multiple fused aromatic rings — stable, carbon-rich structures that form when organic material undergoes incomplete combustion or is exposed to intense heat. They are among the most studied environmental and dietary carcinogens in toxicology, appearing in cigarette smoke, vehicle exhaust, industrial emissions — and, critically, in food.
The National Cancer Institute (NCI) identifies the primary mechanism of dietary PAH formation with disarming simplicity: when fat and juices from meat drip onto a hot surface or open flame, they create smoke that deposits PAH compounds back onto the food surface. The same chemistry occurs during smoking, grilling, roasting, and high-temperature frying — cooking methods that span virtually every culinary tradition in the world, and that are especially prevalent in Indian domestic cooking, from tandoor-roasted meats to deep-fried snacks to the daily tempering of spices in very hot oil.
Among the PAHs of greatest regulatory concern are Benzo[a]pyrene — classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC) — alongside Benzo[a]anthracene, Benzo[b]fluoranthene, Benzo[k]fluoranthene, Chrysene, Indeno[1,2,3-cd]pyrene, Dibenz[a,h]anthracene, and Benzo[g,h,i]perylene. These eight compounds form the core panel measured in the most rigorous food safety studies, and together constitute what regulators call the EU Priority PAH4 and PAH8 panels.
PAHs have been shown to cause cancer in animal studies with consistent reproducibility. Human epidemiological studies have not yet established a definitive causal link between dietary PAH exposure from cooked foods and cancer incidence — partly because isolating diet from other confounding variables is methodologically challenging. But the NCI explicitly notes this uncertainty as a reason for better measurement, not complacency. You cannot manage what you cannot accurately detect.
Why PAH Testing Has Lagged
For decades, the challenge in food PAH science has not been identifying the compounds — their chemistry has been well understood since the mid-twentieth century — but detecting them accurately, quickly, and affordably across the enormous variety of food matrices in which they can appear.
Conventional extraction methods for PAHs from food samples — solid phase extraction (SPE), liquid-liquid extraction (LLE), and accelerated solvent extraction (ASE) — each carry significant practical disadvantages. They are labour-intensive, requiring extensive sample preparation time. They consume substantial volumes of hazardous organic solvents, creating both occupational health risks for laboratory workers and environmental disposal problems. They are costly at scale, limiting the frequency of routine food safety surveillance. And their performance can vary considerably across different food types — the fat content, water content, protein composition, and physical structure of a sample all affect extraction efficiency.
The result has been food safety surveillance that is reactive rather than proactive — deployed when a specific concern arises, rather than as a continuous quality management tool across the food supply chain.
QuEChERS: The Method That Changes the Equation
The answer to this detection bottleneck has a deliberately catchy acronym: QuEChERS — standing for Quick, Easy, Cheap, Effective, Rugged, and Safe — a streamlined sample preparation methodology originally developed for pesticide residue analysis in agricultural produce, and now being systematically adapted for PAH detection across food categories.
The core QuEChERS workflow is elegant in its efficiency. Food samples are extracted using a minimal volume of acetonitrile, a relatively mild solvent. The extract is then purified using selected combinations of sorbents — materials that selectively bind interfering matrix compounds while allowing PAHs to pass through cleanly. The purified extract is then analysed by gas chromatography coupled with mass spectrometry (GC-MS) — the gold-standard analytical technique for identifying and quantifying trace organic compounds in complex matrices.
A landmark 2025 study from the Department of Food Science and Biotechnology at Seoul National University of Science and Technology (SeoulTech), led by Professor Joon-Goo Lee, validated this QuEChERS approach specifically for the eight priority PAHs across multiple food matrices. The analytical performance was exceptional by any standard:
Calibration linearity — R² values above 0.99 for all eight PAHs, confirming a highly reliable, linear measurement system across the quantification range.
Detection sensitivity — limits of detection ranging from 0.006 to 0.035 µg/kg, and limits of quantification from 0.019 to 0.133 µg/kg — sensitivities well below the regulatory thresholds set by the European Food Safety Authority (EFSA) and other bodies.
Recovery accuracy — at three spiking levels (5, 10, and 20 µg/kg), recovery rates ranged from 86.3% to 109.6%, 87.7% to 100.1%, and 89.6% to 102.9% respectively — all comfortably within internationally accepted validation criteria of 70–120%.
Precision — relative standard deviation values between 0.4% and 6.9% across all matrices, indicating outstanding reproducibility.
Professor Lee summarised the method’s significance: “This method not only simplifies the analytical process but also demonstrates high efficiency in detection compared to conventional methods. It can be applied to a wide range of food matrices.”
Where the PAHs Were Found?
The SeoulTech study’s most immediately actionable finding — beyond the methodology itself — was the distribution of PAH concentrations across tested food categories.
Soybean oil recorded the highest PAH levels among the foods tested. Duck meat followed. Canola oil placed third. These are not obscure processed foods or industrial by-products. Soybean and canola oils are among the most widely used cooking oils globally — and in India, soybean oil in particular has grown substantially in market share over the past decade. Their high PAH burden likely reflects both the high-temperature refining processes used in commercial oil production and the natural vulnerability of unsaturated fatty acids to PAH-generating oxidative chemistry at elevated temperatures.
The duck meat result is consistent with broader evidence that fatty meats cooked at high temperatures — where fat dripping onto heat sources generates PAH-laden smoke that re-deposits on the food surface — carry significant PAH loads. The same mechanism applies to any high-fat meat on a grill or in a tandoor.
Beyond SeoulTech: A Converging Body of Evidence
The SeoulTech findings are part of a rapidly expanding literature applying QuEChERS-based methods across different food categories and geographies.
A companion 2025 study published in the journal Foods developed a modified QuEChERS approach incorporating a freeze-out purification step and applied it to 302 retail food samples. Among the most significant findings: Kezuribushi — a Japanese smoked and dried fish product — recorded the highest concentrations of the four priority PAHs. Grilled chicken feet were identified as a potential health concern based on the EFSA margin-of-exposure methodology. The smoked fish result is particularly relevant to Indian food safety contexts, where smoked and dried fish products are widely consumed across coastal and northeastern regions.
A third 2025 study focused on cereals and cereal-based products — one of the food categories least intuitively associated with PAH contamination — using a modified QuEChERS method with Z-Sep⁺ clean-up and GC-MS/MS on 96 cereal samples and 18 cereal-based products from the Romanian market. Chrysene was quantified in 17% of cereal samples, though no PAHs were detected above quantification limits in derived cereal products. The finding confirms that PAH contamination extends beyond animal-origin and oil-based foods into grain matrices — likely through atmospheric deposition and drying processes.
Together, these studies confirm QuEChERS-based PAH surveillance as a cross-category, practical, and analytically robust approach ready for deployment at regulatory and industrial scale.
The Great Indian Kitchen
For Indian food safety regulators, public health researchers, and consumers, this body of research carries particular resonance. Indian culinary tradition is built on high-heat cooking. Tandoor temperatures exceed 480°C. Tempering — the foundational technique of heating whole spices in very hot oil until they crack and release — exposes cooking oils to temperatures at or above their smoke points as a deliberate cooking step. Smoke flavour is a prized quality in many regional cuisines. Smoked and dried fish are dietary staples in coastal Andhra, Kerala, Bengal, and across the Northeast.
India’s Food Safety and Standards Authority (FSSAI)has PAH regulations in place for certain food categories, but comprehensive, routine PAH surveillance across the domestic food supply — including street food, restaurant cooking, and home kitchen practices — remains limited. The QuEChERS methodology, with its reduced cost, faster turnaround, lower solvent requirement, and demonstrated accuracy across diverse food matrices, offers a practical pathway to scaling up that surveillance without the resource burden of conventional extraction methods.
The broader public health implication is not one of panic, but of informed awareness. As Professor Lee notes: “Our research can improve public health by providing safe food. It also reduces the use and emission of hazardous chemicals in laboratory testing.” The goal is not to make people afraid of their kitchens, but to give regulators, food companies, and eventually consumers the measurement infrastructure to understand, manage, and reduce PAH exposure — through cooking technique awareness, oil selection, temperature control, and ventilation.
From Laboratory to Policy
The convergence of sensitive, validated QuEChERS methods with the analytical precision of GC-MS creates an opportunity for food safety that was not practically available a decade ago. What was once expensive, slow, and chemically intensive is becoming faster, cleaner, and accessible enough for routine deployment.
The implications cascade through the food system. Regulators gain a practical surveillance tool scalable to large sample volumes without prohibitive cost. Food manufacturers gain quality management capability for monitoring PAH levels in heat-processed products. Researchers gain the sensitivity to detect PAHs at the sub-µg/kg levels needed to study exposure across realistic dietary patterns. And eventually, the knowledge generated flows back into evidence-based cooking guidance — the kind that might, one day, appear on cooking oil labels, restaurant safety certifications, or public health advisories.
The compounds themselves are not new. The smoke rising from a grill has carried PAHs since humanity first cooked over fire. What is new is our ability to find them precisely, measure them reliably, and act on what we find.
That, in the end, is what food science is for.
–V Devaki Nandini
