More information of food processing impact on chlorate residues needed - CONTAM

By Joseph James Whitworth contact

- Last updated on GMT

Fruit and veg was the most affected food group and frozen varieties often accounted for highest chlorate levels
Fruit and veg was the most affected food group and frozen varieties often accounted for highest chlorate levels

Related tags: Food, Chlorine

An EFSA panel has called for more data on the impact of processing on chlorate residues in food but said total daily intake at the highest estimated amount is unlikely to exceed safe levels.

The panel on Contaminants in the Food Chain (CONTAM) said the impact of the uncertainties on the risk assessment is large.

A scientific opinion found drinking water was the main source for chlorate in the diet​.

EFSA 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.

Long-term exposure to chlorate can inhibit iodine uptake and a high intake on a single day could be toxic as it can limit the blood’s ability to absorb oxygen, leading to kidney failure.

Use in food industry

Chlorate is formed as a by-product when using chlorine, chlorine dioxide or hypochlorite for the disinfection of drinking water, water for food production and surfaces coming into contact with food.

In many fruit and vegetable commodities chlorate levels exceeding the default maximum residue levels (MRL) of 0.01 mg/kg are found.

No specific MRLs have been established for chlorate under Regulation (EC) No 396/2005 so a default of 0.01 mg/kg is applicable to all foods listed.

Chlorate residues (unlike pesticide residues) usually arise post-harvest through food processing and local contamination resulting in high variation within individual samples is less likely to occur.

The panel said chlorate residues in food come mainly from using chlorinated water for food processing (e.g. washing) and disinfection of surfaces and food processing equipment coming into contact with food.

More information about the impact of processing (e.g. blanching) on chlorate residues in food is needed, said the panel. 

The World Health Organisation (WHO) established a guideline level in drinking water of 0.7 mg/L.

Based on current practices in the food industry, application of a hypothetical MRL of 0.7 mg/kg for all foodstuffs and drinking water would only minimally reduce acute/chronic exposures and related risks, according to CONTAM.

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, it added.

The panel said any efforts to reduce residues should take into account whether these would have an impact on microbiological food safety.

In foods of plant origin chlorate is frequently analysed after extraction with methanol by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Chlorate in which foods

The EFSA Evidence Management Unit (DATA Unit) held a call for data on chlorate levels in food and drinking water which received 8,028 samples.

Food groups most represented were ‘Vegetable and vegetable products’ and ‘Fruit and fruit products.

The highest mean concentrations were for ‘Chilli pepper’ (lower bound, LB = 164 μg/kg, upper bound, UB = 169 μg/kg,), ‘Aubergines’ (LB = 157 μg/kg, UB = 164 μg/kg,) and ‘Vegetable and vegetable products, unspecified’ (LB = 216 μg/kg, UB = 222 μg/kg).

Food commodities reported as ‘frozen’ showed the highest levels of chlorate within each group.

However, in many such samples levels were below the limit of quantification, indicating they may depend on how food is processed (levels of chlorine in water and rinsing).

Occurrence data are needed for foods for which there is none such as tea, coffee and beer.

There were indications high levels of chlorate might be in yoghurt and infant/follow-on formula but the data were insufficient for exposure assessment, said the panel. 

EFSA’s scientific advice was requested to support the Commission and Member States who are re-examining existing measures to limit consumer exposure to chlorate in food.

Related topics: Food Safety & Quality

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