Arsenic Content Assessment in Agricultural Crops: Standards, Methods, and Applications

Arsenic content assessment in crops is a fundamental food safety and agricultural quality control process that quantifies total arsenic and inorganic arsenic in cereals, vegetables, fruits, and other plant-derived products. Because inorganic arsenic is classified as a Group 1 human carcinogen and strict maximum limits are enforced under standards such as GB 2762, Codex Alimentarius, and EU Regulation 2023/915, accurate testing by accredited third-party laboratories helps producers, exporters, and regulators keep contaminated produce out of the food chain. This article explains the scope of crop arsenic assessment, the sample types involved, the testing items and analytical methods, and the practical applications of the results.

Technical Overview

Arsenic (As) is a toxic metalloid that enters agricultural ecosystems through both geogenic sources (natural mineralization in soil parent material) and anthropogenic activities (mining, smelting, historical use of arsenical pesticides, phosphate fertilizers, and irrigation with contaminated groundwater). Crops take up arsenic through the roots, and the degree of accumulation depends on soil properties, redox conditions, water management, and plant genotype.

Speciation is central to any arsenic evaluation. Arsenic occurs in crops primarily as inorganic species, arsenite As(III) and arsenate As(V), and as organic species such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Inorganic arsenic is by far the most toxic fraction and is the basis for most regulatory limits, while the organic species are comparatively less toxic. Chronic dietary exposure to inorganic arsenic is associated with skin lesions, cardiovascular disease, neurodevelopmental effects, and cancers of the skin, bladder, and lung, which is why the International Agency for Research on Cancer (IARC) classifies inorganic arsenic as a Group 1 human carcinogen.

Rice deserves particular attention in any arsenic assessment program. Under the anaerobic conditions of flooded paddies, iron oxides are reductively dissolved, mobilizing arsenic, and rice roots take up arsenite efficiently through silicon transport pathways. As a result, rice grain typically contains ten times more arsenic than other cereal crops, and a large share of it is in the inorganic form. A complete crop arsenic assessment therefore integrates representative field sampling, validated chemical analysis, speciation of the inorganic fraction, comparison against applicable maximum limits (MLs), and, where required, dietary exposure estimation.

Testing Samples

Assessment programs cover all major crop categories. Samples must be collected so that they are representative of the field, lot, or batch, and each sample should be accompanied by documentation of origin, variety, growth stage, and irrigation source.

Cereal Grains

Rice is the priority matrix, tested at the paddy, brown (husked), and milled (polished) stages because milling removes part of the arsenic concentrated in the bran layer. Wheat, maize, barley, oats, and other cereals are also tested, although their arsenic burden is generally lower and regulated as total arsenic in most jurisdictions.

Vegetables

Leafy vegetables (spinach, Chinese cabbage, lettuce), fruiting vegetables (tomato, pepper, eggplant), and stem vegetables are collected as the edible portion after standardized washing and trimming. Leafy crops grown on contaminated soils tend to show higher arsenic retention than fruiting crops.

Fruits

Tree fruits, melons, and berries are analyzed as the edible flesh. Arsenic transfer to fruit pulp is usually limited, but assessment is required for orchards established on former agricultural land where lead arsenate pesticides were historically applied.

Legumes and Oilseeds

Soybeans, common beans, peanuts, and rapeseed are included in monitoring programs because peanuts in particular can accumulate measurable arsenic in kernels and are widely used in processed foods and infant products.

Root, Tuber, and Aquatic Crops

Potato, taro, sweet potato, lotus root, water chestnut, and water spinach are frequently sampled, as root-zone contact with soil or contaminated irrigation water can produce elevated arsenic levels relative to above-ground commodities.

Specialty Crops and Derived Products

Tea leaves, edible fungi, medicinal and aromatic herbs, rice flour, rice-based snacks, and infant cereals are tested because of their concentrated processing, high consumption by sensitive populations, or explicit coverage under food contaminant regulations.

Testing Items

The core testing items for a crop arsenic assessment are:

• Total arsenic (sum of all chemical species), the primary compliance parameter for most cereals other than rice, vegetables, and fruits under standards such as GB 2762-2022.
• Inorganic arsenic (As(III) plus As(V)), the decisive parameter for rice and rice-based products, regulated by GB 2762-2022 in China, by Codex Alimentarius CXS 193-1995, and by EU Regulation 2023/915.
• Full arsenic speciation, quantifying As(III), As(V), MMA, and DMA to support risk characterization and agronomic investigations.
• Supporting matrix analysis, including arsenic in farmland soil (evaluated against GB 15618-2018 risk screening values) and in irrigation water (evaluated against GB 5084), to identify the contamination pathway.
• Dietary exposure estimation, combining measured concentrations with food consumption data for comparison against health-based guidance values such as the JECFA benchmark dose range of approximately 3 micrograms per kilogram of body weight per day.

Key regulatory reference values include: inorganic arsenic in rice of 0.2 mg/kg under GB 2762-2022; 0.2 mg/kg for polished rice and 0.35 mg/kg for husked rice under Codex; and 0.10 mg/kg for non-parboiled milled rice, 0.25 mg/kg for husked and parboiled milled rice, and 0.30 mg/kg for rice cakes under EU Regulation 2023/915. The U.S. FDA has issued an action level of 0.1 mg/kg inorganic arsenic for infant rice cereal. Total arsenic limits of 0.5 mg/kg generally apply to most other cereals, vegetables, and fruits under GB 2762-2022.

Testing Methods

Sampling and Sample Preparation

Grain lots are sampled dynamically or statically following procedures such as GB 5491 or ISO 24333 to obtain representative increments that are combined and reduced to a laboratory sample. Edible portions of vegetables and fruits are washed, drained, and homogenized. Samples are dried at low temperature, milled to a fine homogeneous powder, sealed, and stored under conditions that prevent both contamination and speciation changes. A typical laboratory sample is 0.5 to 2 kg of raw material.

Determination of Total Arsenic

Total arsenic is measured after complete decomposition of the matrix. Common approaches include:

• Inductively coupled plasma mass spectrometry (ICP-MS), the first-choice method for its very low detection limits, wide linear range, and multi-element capability; collision or reaction cell technology removes the argon chloride interference at mass 75, and isotopic internal standards such as germanium or rhodium correct for matrix effects. ICP-MS procedures are aligned with ISO 17294-2 and GB 5009.11.
• Hydride generation atomic fluorescence spectrometry (HG-AFS), a robust and cost-effective technique widely used in China, in which arsenic is pre-reduced to As(III) with potassium iodide and ascorbic acid and converted to arsine with sodium borohydride before detection.
• Inductively coupled plasma optical emission spectrometry (ICP-OES) and graphite furnace atomic absorption spectrometry (GFAAS), applied where expected concentrations are higher or instrument availability dictates.

Microwave-assisted digestion with nitric acid and hydrogen peroxide is the standard decomposition route, following principles compatible with US EPA Method 3052 and AOAC Official Method 2015.01 for elemental analysis of foods.

Speciation of Inorganic Arsenic

Because regulatory limits for rice are set on inorganic arsenic, species must be preserved and separated before detection. The workflow is:

• Mild extraction of arsenic species using dilute nitric acid, often with a small fraction of hydrogen peroxide, at controlled temperature to quantitatively leach the species without interconversion.
• Separation by anion-exchange high performance liquid chromatography (HPLC), typically with an ammonium carbonate or phosphate mobile phase at alkaline pH, resolving As(III), As(V), MMA, and DMA in a single run as specified in EN 16802:2016 and GB 5009.11.
• On-line coupling of the HPLC to ICP-MS or to hydride generation AFS for element-specific detection, achieving inorganic arsenic quantification limits of 0.005 to 0.02 mg/kg, well below the strictest regulatory limits.

Quality Assurance and Data Evaluation

Accredited third-party laboratories operating under ISO/IEC 17025 quality systems validate each batch with reagent blanks, duplicate digestions, matrix spikes, and certified reference materials such as rice flour CRMs. Typical acceptance criteria include spike recoveries of 80 to 110 percent and relative deviations below 10 percent between duplicates. Results are reported on a fresh-weight or dry-weight basis with measurement uncertainty, then compared against the applicable maximum limits of GB 2762, Codex, EU, or destination-market regulations to issue a conformity conclusion.

Applications

Crop arsenic assessment supports decision-making across the entire agricultural and food supply chain:

• Food safety surveillance and market supervision, identifying non-conforming lots before distribution and protecting consumer health.
• Import and export compliance, demonstrating conformity with destination-market contaminant limits for rice, vegetables, and processed agricultural products.
• Farmland classification and remediation, using paired soil and crop data to apply GB 15618-2018 screening values, delineate areas requiring safe-utilization measures, and verify the effectiveness of soil passivation or amendment treatments.
• Agronomic optimization, evaluating water management strategies such as alternate wetting and drying, which can cut grain inorganic arsenic by half or more, and screening cultivars with low arsenic uptake for breeding programs.
• Processing and product development, quantifying how milling, bran removal, washing, and cooking in excess water reduce inorganic arsenic, and controlling rice-based ingredients for infant foods subject to the strictest limits.
• Certification and traceability, providing the analytical evidence required for good agricultural practice schemes, organic certification, and origin-based brand claims.
• Epidemiological and regulatory research, generating exposure datasets for refined dietary risk assessments by national and international scientific bodies.

FAQ

What is the difference between total arsenic and inorganic arsenic testing?

Total arsenic measures the sum of all arsenic species after complete acid digestion, while inorganic arsenic testing preserves and chromatographically separates only the highly toxic As(III) and As(V) species. Most limits for rice and rice products are set on inorganic arsenic, whereas limits for other cereals, vegetables, and fruits are typically set on total arsenic.

Why does rice accumulate more arsenic than other crops?

Flooded paddy soils become oxygen-depleted, which dissolves iron minerals and releases arsenic into soil solution in the mobile arsenite form. Rice roots absorb arsenite efficiently through silicon transporters, so grain concentrations commonly reach 0.1 to 0.3 mg/kg, an order of magnitude above other cereals.

How much sample is needed and how should it be collected?

A representative laboratory sample of 0.5 to 2 kg of grain or 1 to 2 kg of fresh vegetable or fruit is sufficient. Multiple increments should be taken across the field or lot, combined, and documented with origin and variety details, because arsenic distribution is spatially heterogeneous.

Can processing and cooking reduce arsenic in rice?

Yes. Progressive milling removes arsenic-rich bran layers, thorough rinsing removes surface contamination, and boiling rice in a large excess of water that is discarded can reduce inorganic arsenic by roughly 40 to 60 percent. These steps are reflected in the different regulatory limits applied to husked versus milled rice.

How quickly can results be obtained and what do they cost?

Standard turnaround for total arsenic or inorganic arsenic determination is typically three to seven working days, with expedited options available from accredited third-party laboratories. Costs depend on the matrix, the number of species required, and whether supporting soil or water analysis is included.

Which laboratories are qualified to perform crop arsenic assessment?

Testing should be commissioned to accredited third-party laboratories holding ISO/IEC 17025 accreditation or national equivalents, with validated methods traceable to GB 5009.11, EN 16802, AOAC, or ISO standards, demonstrated low quantification limits, and routine use of certified reference materials for quality control.