Heavy Metals and Chemical Contaminants in Food: A Risk-Based Testing Guide

Testing or auditing is valuable only when the result is tied to a defined decision. The questions below should be agreed before sampling so that the sample, method, specification and response are aligned.

Metals can arise from geology, irrigation water, environmental deposition, agricultural inputs, processing equipment or packaging contact. Other chemical contaminants may be process-generated, environmental or residue-related. The risk profile therefore changes by commodity and process. Rice, spices, leafy vegetables, seafood, beverages and processed foods should not be assigned identical contaminant panels without a technical reason.

Contaminant results can also be distorted by sample preparation. A small non-representative portion of a heterogeneous food may under- or over-estimate the lot. Poor laboratory controls can introduce metals from reagents, vessels or grinding equipment. The quality system needs blanks, calibration, suitable reference/recovery checks and contamination-resistant preparation appropriate to the method.

• Start from the current FSSAI contaminant schedule for the exact food category, then add risk-based customer parameters only where justified.
• Record country/region of origin and supplier lot for agricultural ingredients because source patterns can matter during investigations.
• Define whether the result/limit is on an as-is, dry-weight or other specified basis before comparing values.
• Use suitable clean containers and tools for trace-level metals; sampling hardware itself can contaminate the sample.
• Keep detection/quantification capability below the decision level so a less-than result is meaningful.

FSSAI's Manual on Metals gives the national analytical framework, while the current contaminant regulation provides limits. Instrumental techniques can include AAS, ICP-OES or ICP-MS where the applicable validated method and laboratory scope permit; method choice should consider required sensitivity, matrix interferences, digestion, calibration and uncertainty rather than instrument prestige. The 2026 contaminant amendment is a reminder that the regulatory register must be actively maintained.

A method number is not, by itself, a product specification or legal limit. The method tells the laboratory how a defined measurand is determined; the applicable regulation, product standard, consent, customer specification or validated internal plan supplies the criterion and decision context.

Trace contaminant sampling should be designed around the lot and likely heterogeneity. A composite may estimate lot average concentration, but it can hide a localized high unit; individual units may be needed when the specification or enforcement plan is unit-based. The business should agree whether the decision concerns an average, maximum, supplier trend or investigation.

Sample containers and preparation tools can be sources of the analyte being measured. Metals work therefore needs particular attention to cleanliness, compatible materials and blank control. When a value is close to a legal limit or a commercial dispute is possible, retained sample material and chain of custody become especially important.

• Use documented random or stratified sampling across the lot rather than collecting only from the top/front of a consignment.
• Avoid metal tools or containers that can contribute the target analyte.
• Homogenize only with equipment demonstrated not to introduce relevant contamination.
• Keep retained portions for confirmatory work when results are close to a legal limit or dispute is possible.
• Provide matrix, ingredient list and expected range so digestion and calibration decisions are appropriate.

Interpretation should include the limit source, unit and decision context. A result close to a maximum limit deserves careful review of measurement uncertainty and sampling representativeness. A result far below a limit may support current conformity, but a rising supplier trend can still justify preventive action before a regulatory failure occurs.

A single high result should be contained and investigated, not automatically dismissed as an outlier. Confirmatory analysis is most useful when it follows a predefined sampling and decision plan that preserves the original lot evidence.

A contaminant programme should be prioritized by hazard and exposure, not by how many analytes can be placed on an instrument run. Review supplier history, commodity origin, consumer group, serving/exposure, process concentration and regulatory surveillance signals. Use failures to update risk ranking so future sampling focuses on the source and season that produced the signal.

Long-term control belongs upstream wherever possible. Supplier specifications, agricultural/environmental controls, water quality and process-material controls prevent contamination more effectively than relying solely on finished-product screening.

• Maintain a current contaminant-limit register with source regulation, amendment date, commodity and unit.
• Link every laboratory report to supplier lot and receiving record.
• Escalate new suppliers and high-risk origins until a stable evidence history is established.
• Use CAPA to remove/control the source; repeated screening of contaminated material is not a preventive solution.
• Review the panel after regulatory amendments, origin changes, process changes or new scientific/regulatory alerts.

Standards, regulations and official methods are revised over time. Before a result is used for a regulatory conformity decision, confirm the current FSSAI notification or Gazette text, the exact food or water category, the latest applicable BIS edition and amendments, the customer or statutory specification, the sampling requirement and the laboratory method/scope. FSSAI compendia are useful ready references, but the original notifications and amendments prevail where there is a conflict. This article is technical guidance, not a substitute for the applicable law, permit or product specification.

• FSSAI Contaminants, Toxins and Residues – amendments
• FSSAI Manual(s) of Method(s) of Analysis
• FSSAI Product Standards
• BIS Indian Standards portal
• Heavy Metals & Pesticide Analysis
• Food & Agricultural Products Testing
• Adulteration Analysis
• How to Send Samples
• All Technical Blogs

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• Nuts and nut products