Chlorate in food Questions and answers about origin and health risks

Chlorates are salts of chloric acid (HClO₃) consisting of the chlorate anion (CIO₃^-) and various cations. Well-known chlorate compounds include sodium and potassium chlorate. It is not known which chlorate compounds were present in the foods in which chlorate was detected.

In the past, sodium and potassium chlorate were used for weed control. In the EU, plant protection products (PPP) or biocidal products containing chlorate as an active substance are no longer permitted. However, chlorate can form as a by-product during the storage or use of cleaning products or disinfectants containing chlorine.

According to current knowledge, chlorates enter food through contact with water that has been treated with biocidal products which contain chlorine. Chlorate can form as a by-product when such products are used or may already be present in a product during storage. Residues may remain on surfaces or equipment after cleaning or disinfection and enter food in this way. Water is also added to some foods during production.

Repeated intake of chlorate can inhibit iodine absorption and possibly lead to a deficiency. This inhibition can cause temporary changes in thyroid hormone levels in members of risk groups. People with thyroid disorders or iodine deficiency as well as newborns and children are particularly susceptible to adverse effects. Pregnant women who already have thyroid dysfunction are another vulnerable group. However, the inhibition of iodine uptake by chlorate is not permanent: if chlorate is no longer ingested, iodine uptake returns to normal after some time. A single intake of chlorate has no significant effect on the inhibition of iodine uptake. However, even a single intake of higher concentrations of chlorate can cause damage to red blood cells.

For chlorate, EFSAshort forEuropean Food Safety Authority has derived a tolerable daily intake (External Link:TDI) of 0.003 milligrams (mgshort formilligram) per kilogram (kgshort forkilogram) of body weight. Based on the finding that a single intake of higher concentrations of chlorate can damage red blood cells, EFSAshort forEuropean Food Safety Authority has also derived an acute reference dose (ARfDshort forAcute Reference Dose) of 0.036 mgshort formilligram per kgshort forkilogram body weight for chlorate.

The maximum residue levels of plant protection products (PPP) permitted in and on food are regulated uniformly across the EU. In 2020, External Link:provisional maximum residue levels for chlorate in food were set. The maximum permitted levels vary depending on the type of food and the expected, unavoidable level of residues. The maximum levels are based on measurements of the actual prevalence of chlorate in food from between 2014 and 2018, which were provided by Member States and food business operators. In 2025, current data on prevalence in food is to be used as a basis to review these maximum levels and adjust them if necessary. They should be as low as possible and follow the External Link:ALARA principle (ALARA = as low as reasonably achievable).

For chlorate, the World Health Organization (WHO) has published a provisional guideline value of 0.7 mgshort formilligram per litre of drinking water. However, a reduction of this value is currently under discussion. The regulations in the German Drinking Water Ordinance are already significantly stricter and stipulate a limit value for chlorate of 0.07 mgshort formilligram per litre of drinking water, ten times lower than the WHO. An exception is provided in the case of immediate hazard prevention. Following, for example, local contamination due to leaks in drinking water pipes, the chlorate concentration in drinking water may rise to 0.7 mgshort formilligram per litre for a short period.

Based on the evaluated data on the prevalence of chlorate in food, EFSAshort forEuropean Food Safety Authority concludes in its opinion that repeated intake of chlorate in younger population groups with mild to moderate iodine deficiency is a cause for concern. However, a single intake is not considered to pose a critical health risk.

Chlorate is detected in a wide range of foods of both plant and animal origin. It is frequently found in frozen and processed foods, fruit juices and salads/herbs. The presence of chlorate in these products could be due to processes such as glazing frozen goods, diluting juice concentrates or washing herbs and salads with water which contains chlorate.

Chlorate residues have been detected in food from numerous countries of origin, including Germany.

Consumers should eat a balanced and varied diet. The health benefits of fruit and vegetables remain undisputed.