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Why herbs and spices are high-risk commodities

Herbs and spices are among the most challenging commodities in food safety monitoring. Their global production, fragmented supply chains and complex post-harvest handling contribute to a high and diverse contamination risk profile.

They are often cultivated in tropical and subtropical regions where pest and fungal pressure is high. After harvest, they undergo drying, processing and long-distance transport. These factors combined make herbs and spices particularly vulnerable to multiple types of pesticides and contaminants.

In the EU Rapid Alert System for Food and Feed (RASFF), pesticide residues remain one of the most commonly reported issues for herbs and spices.

General use of pesticides

Due to high pest pressure in warm climates, pesticide use is common in herb and spice cultivation. 

Leafy herbs such as parsley, basil, mint, and coriander are particularly vulnerable to insect and fungal damage, leading to frequent applications of insecticides and fungicides.

Spices derived from seeds, bark, or dried fruits may experience lower fungal pressure during cultivation, but insect control remains essential both in the field and during storage. In addition, post-harvest treatments are sometimes applied to protect dried products during transport and storage.

Ethylene oxide

Although not a conventional pesticide, ethylene oxide has been one of the most significant food safety issues affecting spices in recent years. It is used in some regions as a fumigation and sterilisation agent to reduce microbial contamination. However, its use in food within the EU is prohibited. Despite this, ethylene oxide has been repeatedly detected in imported spice products, leading to product recalls and border rejections.

Chlorpyrifos

An organophosphate insecticide historically used to control insects such as aphids, beetles and caterpillars. It has been widely applied in many spice-producing regions such as India, Vietnam, and parts of Africa due to its broad-spectrum activity and relatively low cost.  This widespread use has led to frequent detection of chlorpyrifos residues in imported herbs and spices. 

Imidacloprid

A systemic neonicotinoid insecticide used against sucking insects such as aphids and whiteflies. It can be applied via soil, seed or foliar treatment. This pesticide is widely used in herb and spice cultivation in Asia and Latin America, where insect pressure can be high due to warm climates. Its systemic properties allow it to be absorbed by the plant and provide long-lasting protection. 

The risk of residues arises because systemic pesticides can remain in plant tissues until harvest. In dried herbs and spices, residues can become more concentrated after dehydration. 

Cypermethrin

A pyrethroid insecticide used against a wide range of insect pests. It is widely applied both during crop growth and in some cases for post-harvest pest control.  This pesticide is commonly applied in the cultivation of cumin, coriander, chili, and various leafy herbs. Its stability under field conditions contributes to its continued widespread use. 

Contaminants in herbs and spices

Mycotoxins

Mycotoxins are toxic compounds produced by fungi such as Aspergillus species. Aflatoxins and ochratoxin A are the most relevant in herbs and spices. These contaminants typically develop when products are exposed to humid conditions during drying or storage. Spices such as chili powder, paprika, pepper, and nutmeg are particularly susceptible.

Pyrrolizidine alkaloids (PA)

Pyrrolizidine alkaloids are natural toxins produced by certain plant species as a defence mechanism against herbivores. Contamination occurs when PA-producing weeds are unintentionally harvested together with herbs or spices. This is particularly relevant for products such as oregano, cumin, and herbal infusions, where field contamination with weed species such as Senecio or Heliotropium can occur. 

(For more information on this topic, read our article: Pyrrolizidine alkaloids in herbs and spices)

Process-related contaminants: PAHs

Polycyclic aromatic hydrocarbons (PAHs) can be formed during traditional drying processes where direct smoke or open fires are used. This is especially relevant for spices such as paprika, chili, and pepper when smoke drying or roasting techniques are applied.

Environmental contaminants and heavy metals

Herbs and spices may also contain heavy metals such as lead, cadmium, arsenic, and mercury. These can enter the supply chain through contaminated soil, irrigation water, atmospheric deposition, or contact with contaminated drying surfaces. In some cases, elevated lead levels have also been linked to intentional adulteration practices, such as the addition of lead chromate to turmeric to enhance colour.

Why testing herbs and spices is analytically challenging

The complexity of herbs and spices makes them particularly demanding from an analytical perspective.

Key challenges include:

• highly complex plant matrices
• low residue levels requiring sensitive detection methods
• concentration effects due to drying
• presence of multiple contaminant classes in a single sample
• variability in origin, processing and storage conditions

Given this complexity, continuous monitoring and advanced analytical testing remain essential for importers and food manufacturers to ensure compliance and protect consumer safety in a global supply chain.