Residues of chlorate are detected in various food commodities, also in frozen products or ready-to-eat carrots. Authorities and industry are searching for possible sources for this contamination of food. Treatment of drinking water with chlorine containing agents is common all over the world and was identified as a possible source. Further pathways of the contamination are not yet fully clarified. The CVUA Stuttgart (Chemisches und Vete­rinäruntersuchungsamt) describes a further possible pathway: chlorinated water which was used for washing vegetables and fruits.

Application
Chlorates are the salts of chloric acid, which is used in pyrotechnics, for bleaching of paper and for tanning leather. Chlorates are also effective as plant protection agents (herbicides) and disinfecting agents (biocides), however, application as such is not authorised anymore. Chlorate may be present as a by-product in authorised chlorine containing disinfectants for drinking water production. Sodium hypochlorite solution for example contains up to 5.4 % of sodium chlorate (by reference to free chlorine / active chlorine).

Registration
In Germany, herbicides with the active substance sodium chlorate were authorised until 1992. Since 2010, the application of chlorate containing pesticides is prohibited in the EU. Relevant residues stemming from former applications can be ruled out. No chlorine containing substances for use as disinfectant are authorised as food additives.

Current Legal Background
In June, Efsa has published a statement in which toxicological maximum limits for the acute and chronic risks of chlorate in food were deduced. According to EFSA, a tolerable daily intake (TDI) of 3 µg/kg body weight is considered harmless. The interim values based on the risk assessment of the German Federal Institute for Risk Assessment (BfR), are revoked by the Federal Ministry for Food and Agriculture (BMEL).
Until maximum limits are valid for the whole EU, food should be controlled according to art. 14 of the basic regulation (EC) No. 178/2002 for safety. For this purpose, EFSA has deduced a maximum quantity for daily intake (acute reference dose ARfD) of 36 µg/kg body weight, which is to be applied without any variability factors.
The BMEL expects the EU commission to set specific maximum limits in the near future to minimise chronic exposition to chlorate.
For baby food, a maximum residue limit of 0.01 mg/kg for ready-to-eat food products is still applicable, irrespective of the source of the residue.

Analysis
The determination of chlorate and perchlorate at GALAB is carried out using a single residue method with LC-MS/MS detection. With our analytical method we safely determine chlorate in fruits, vegetables and juices with a limit of quantification of 0.01 µg/kg.

Links
EFSA statement June 2015
CVUA
BLL – Chlorate