Chlorate in food: risks for public health

Long-term exposure to chlorate in food, particularly in drinking water, is a potential health concern for children, especially those with mild or moderate iodine deficiency. But the total intake on a single day even at the highest estimated levels is unlikely to exceed the recommended safe level for consumers of all ages.

These are the main conclusions of EFSA’s scientific opinion on the chronic and acute public health risks from dietary exposure to chlorate (including drinking water).

Chlorate can be present in food from the use of chlorinated water for food processing and the disinfection of food processing equipment. The most affected food groups are fruit and vegetables. Frozen varieties often account for the highest levels of chlorate within each food group. This probably depends on the amount of chlorate in chlorinated water used for food processing. Drinking water, however, is the main source of chlorate in the diet, possibly contributing up to 60% of chronic chlorate exposure for infants.

Chronic exposure – over time, exposure to chlorate can inhibit iodine uptake. EFSA has set a tolerable daily intake (TDI) of 3 micrograms per kg (µg/kg) of body weight per day for long-term exposure to chlorate in food. EFSA’s highest estimates of chronic exposure for infants, toddlers and other children (up to 10 years of age) are over the TDI, indicating a concern for all children with mild or moderate iodine deficiency.

Acute exposure – a high intake of chlorate on a single day could be toxic for humans as it can limit the blood’s ability to absorb oxygen, leading to kidney failure. EFSA has, therefore, also set a recommended safe intake level for a daily intake (called the ‘acute reference dose’) of chlorate of 36 µg/kg of body weight per day. The highest estimates of acute dietary exposure for all age groups were below this safe intake.

In addition, EFSA was asked by the European Commission to consider the impact on dietary exposure of applying the WHO guidance level for chlorate in drinking water of 0.7 milligrams per kilogram (mg/kg) to all foods covered by EU legislation. If 0.7 mg/kg were used as the maximum level in food for assessing dietary exposure to chlorate (i.e. excluding foodstuffs and drinking water containing chlorate above this level), exposures would drop only slightly and, consequently, this would not affect the potential risk. Under the unlikely scenario that chlorate levels in all food and drinking water were equal to 0.7 mg/kg, however, dietary exposure would be substantially above current levels.

There were several limitations in the available data for this work, at least partly due to the limited timeframe allowed for the assessment. Consequently, EFSA’s experts concluded that the impact of these scientific uncertainties on the risk assessment is large.

EFSA’s scientific advice was requested to support decision-makers in the Commission and Member States who are re-examining existing measures to limit consumer exposure to chlorate in food. When considering efforts to reduce chlorate residues in food, besides the toxicological aspects of these residues, the impact on microbiological food safety should also be taken into account. EFSA did not, however, evaluate these aspects as part of this risk assessment.

During the development of this scientific opinion, EFSA and Germany’s Federal Institute for Risk Assessment (BfR) were involved in a continuous dialogue regarding their respective risk assessments of chlorate in food.

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