Chlorate management

• Chlorates are by-products of the breakdown of chlorine-based sanitisers and chlorine chemicals, which are frequently used to sterilise water. 
• Chlorate can cause iodine deficiency in people and is therefore regulated through legal MRLs (maximum residue limits) for a range of foods, including fresh produce.
• Crops grown in water treated with chlorine-based sanitisers can accumulate chlorate within their tissues.
• Special allowances are made for processed foods under specific conditions, although the burden of proof lies with the food business operator (FBO).

Chlorate (ClO₃⁻) is a substance formed as a by-product during the use of chlorine, chlorine dioxide or hypochlorite in the disinfection of drinking water, water used in food production or processing, and during the cleaning of food contact surfaces (1). According to expert opinion from the European Food Safety Authority (1), and based on surveillance data (2), the levels of chlorate found in food and drinking water were considered too high and capable of interfering with iodine uptake in humans. This is particularly concerning for vulnerable groups such as infants and young children.

Insufficient iodine uptake can lead to significant health issues, including decreased red blood cell production and alterations in bone marrow composition. To address these concerns, the European Union introduced Regulation 2020/749 in June 2020, amending Regulation 396/2005. This newer regulation revoked older approvals for plant protection products containing chlorate and instead recognised that chlorate residues primarily arise as unintended by-products of disinfectant use.

Regulation 2020/749 mandates careful use of chlorine-based products to ensure compliance with statutory limits and introduces new MRLs for a wide range of food products, particularly fresh fruits and vegetables. Notably, the EU does not set an MRL for chlorate in irrigation or processing water itself. Instead, it regulates residues at the food product level, shifting responsibility to growers and food processors. Studies have shown that crops irrigated with chlorinated water can absorb chlorate into plant tissue, occasionally leading to residue levels exceeding the legal limits (3).

Although Regulation 2020/749 sets MRLs for fresh produce, it also includes specific allowances for processed foods. These allowances are aligned with Article 2 of Regulation 852/2004 and recognise that some chlorate residues may arise from compliant sources such as drinking water or processing aids used during food preparation.

When assessing chlorate levels in processed foods, contributions from other legally compliant ingredients can be taken into account. For instance, food that has been in contact with materials containing allowable chlorate levels, or that contains ingredients like water or additives within permissible limits, may still be compliant. However, the responsibility for demonstrating that these residues are legally sourced rests entirely with the food business operator.

Although the EU regulation does not establish a legal maximum for chlorate in drinking water, the World Health Organisation (WHO) has provided a guideline value of 0.7 mg/L (4). It is important to note that this is a non-binding recommendation and not a statutory limit within EU legislation.