Chlorate Residues in Plant-Based Food: an Update

Ein Bericht aus unserem Laboralltag

Dr. Ingrid Kaufmann-Horlacher

 

Since the publishing of our findings on chlorate residues in plant-based foods at the beginning of March 2014, well over a thousand additional plant-based foods have been examined for the presence of chlorate residues. The most recent analytical data show that, since that publication, the number of samples found with quantities of chlorate residues above the current EU-wide valid MRL of 0.01 mg/kg has decreased. As before, leafy and fruit vegetables are still higher than other foods, and processed/deep frozen vegetables are especially salient in that precisely two-thirds of the analyzed products were detected with chlorate residues over 0.01 mg/kg. The highest amounts in this group were in ready-to-eat carrots, at 0.30 mg/kg, and in deep frozen broccoli, at 0.31 mg/kg. The origin of both products is unknown.

 

Since May 2014 the highest value found has been in basil from Malaysia, at 1.5 mg/kg. Soy beans from China contained 0.56 mg/kg and peeled, cubed mango pieces were detected with 0.65 mg/kg chlorate. There are various possible reasons for the presence of these residues (see Info Box). However, the exact cause for the reduction of samples exceeding the MRL of 0.01 mg/kg seen in our analyses over the last several months is not yet readily clear. Depending on which toxicological reference values and variability factors the evaluation is based on, the possibility of an unwanted, acute health risk cannot be ruled out, at least with the mango cubes.

 

 

Current Analytical Results

Between May and October 2014 a total of 1,020 plant-based foods were analyzed for chlorate residues within the realm of our routine testing. In 919 of these samples either no chlorate was detected or the quantity of residues was under the MRL of 0.01 mg/kg. The remaining 101 samples (9.9 %) contained chlorate residues above this value. Chlorate residues over 0.1 mg/kg were measured in 16 samples (1.6 %). Our test results, categorized in detail by food type, are depicted in Table 1.

 

 

 

Illustration 1: Overview of samples tested for chlorate between May and Oct. 2014

 

 

Table 1: Results of analyses from May to October 2014 by food category

Food Category	No.  Analyzed Samples	No. with Chlorate Residues ≥0.01 mg/kg	%	Median mg/kg*	Mean mg/kg*	Maximum mg/kg	Minimum mg/kg
Berries	172	3	1.7	0.016	0.016	0.019	0.012
Leafy Vegetables	161	19	11.8	0.027	0.13	1.5	0.01
Exotic Fruit	61	2	3.3	0.34	0.34	0.65	0.027
Fruit Vegetables	189	27	14.3	0.016	0.037	0.21	0.01
Vegetable Products	44	28	63.6	0.054	0.075	0.31	0.013
Cereals/Cereal Products	25	0	0
Legumes	3	1			0.56	0.56	0.56
Potatoes	17	1	5.9		0.019	0.019	0.019
Pome Fruit	69	0	0
Fruit Products	18	1	5.6		0.079	0.079	0.079
Mushrooms	24	2	8.3		0.077	0.14	0.013
Mushroom Products	12	6	50.0	0.042	0.084	0.23	0.011
Juices	4	2			0.011	0.011	0.011
Baby Food	11	3	27.3	0.011	0.017	0.03	0.011
Sprouts	42	1	2.4		0.050	0.05	0.05
Stone Fruit	96	4	4.2	0.019	0.038	0.10	0.012
Root Vegetables	30	0	0
Citrus Fruit	38	1	2.6		0.012	0.012	0.012
Other	4	0	0
Total Results	1020	101	9.9	0.025	0.078	1.5	0.01

* Based on samples with quantities ≥0.01 mg/kg.

 

The leafy and fruit vegetable samples, especially the vegetable products, contained higher levels of chlorate residues than the total average. Approximately 12 % of the leafy and 14 % of the fruit vegetables contained residues above 0.01 mg/kg, with a maximum of 1.5 mg/kg in basil from Malaysia. The vegetable product samples were especially notable; a full 63 % of all the samples exceeded the MRL. The highest level measured in this reporting period in this food category was 0.30 mg/kg in ready-to-eat carrots and 0.31 mg/kg in deep frozen broccoli, origin unknown. That a high number of mushroom product samples contained residues can be explained by the fact that, with few exceptions, they were dried mushrooms. However, a sample of preserved mixed mushrooms was striking for its high level of chlorate, at 0.23 mg/kg. All samples analyzed between May and October 2014 that contained chlorate residues above 0.1 mg/kg are summarized in terms of their origin and food category in Table 2.

 

Table 2: Samples (from May-Oct. 2014) with Chlorate ≥ 0.1 mg/kg

Food Category	Origin	Chlorate in mg/kg
Sweet Cherries	Spain	0.1
Sugar Snaps	Peru	0.11
Basil	Germany	0.12
Broccoli, deep frozen	Germany	0.13
Cultured Mushrooms, fresh	Poland	0.14
Peas, deep frozen	Unknown	0.15
Cultured Mushrooms, Mixed, Dried	Unknown	0.16
Tomatoes	France	0.2
Cultured Mushrooms, Mixed, Preserved	Unknown	0.23
Coriander	Cambodia	0.37
Soy Beans	China	0.56
Mango	Unknown	0.65
Basil	Malaysia	1.5

 

Our test results from the previous months show a reduction in the number of plant-based foods containing chlorate residues. Perhaps manufacturers and marketers have taken positive measures, such as changing the methods of production and processing of food, increasing testing for residues, and rejecting foods with high residues, etc.

 

Table 3: Test results from May to Oct. 2014, based on concentration intervals

	May 2014	June 2014	July 2014	Aug. 2014	Sept. 2014	Oct. 2014
No. Samples Analyzed	196	122	182	167	173	179
No. Samples w/ Chlorate ≤0.01 mg/kg	166	105	167	152	164	164
No. Samples w/ Chlorate ≥ 0.01 mg/kg	30	17	15	15	9	15
≥ 0.01 < 0.02	12	8	7	9	4	4
≥ 0.02 < 0.05	7	4	4	2	1	5
≥ 0.05 < 0.10	6	2	2	3	2	3
≥ 0.10 < 0.5	3	3	2	1	1	3
≥ 0.5  < 1.0	1	0	0	0	1	0
≥ 1.0	1	0	0	0	0	0

 

 

Illustration 2: Percentage of samples with chlorate residues based on residue intervals in the months of May to Oct. 2014, compared to data from our March 2014 report on data from 2013.

 

 

The analyzed plant-based foods came mostly from EU countries (72 %), and approximately 5 % came from Africa, 7 % from Asia, and 5.2 % from South and Central America. There were 15.5 % more samples with chlorate residues from Asia than from other countries.

 

Table 3: Origin of the analyzed samples (May to October 2014)

Origin	No. Samples	No. Samples with Chlorate ≥0.01 mg/kg	%
Africa	48	3	6.3
Asia	71	11	15.5
EU	737	51	6.9
Europe (non-EU)	8	1	12.5
North America	4	2	50.0
Oceania	6	0	0.0
South and Central America	53	1	1.9
Unknown	93	32	34.4
Total Results	1,020	101	9.9

 

The origin of 93 samples (9.1 %) was unknown. Most of these samples were processed products such as deep frozen or preserved foods, for which there is no obligation to provide the country of origin.

 

 

The category „vegetable products“ had the highest percentage of samples containing chlorate residues, at 63 %. This could be an indication that chlorine or substances which produce free chlorine were used during the after-harvest treatment of the crop, e.g., when the food is disinfected in chlorine-containing processing water. This process can lead to the contamination of the products with chlorate, which is a by-product of chlorination (see Info Box).

This situation can be seen especially in carrots. None of the fresh, unprocessed carrots (mostly from EU member states) contained chlorate residues over 0.01 mg/kg, but more than 50 % of the processed carrots showed chlorate residues higher than 0.01 mg/kg. One-third of the ready-to-eat carrots (mostly from the USA), and 100 % of the deep frozen carrots contained chlorate residues above 0.01 mg/kg (see Table 4).

 

 

Table 4: Test results for carrots, raw and processed (May to October 2014)

Food Category	No. Samples Analyzed	No. Samples with Chlorate ≥0.01 mg/kg	%	Mean mg/kg*	Maximum mg/kg	Minimum mg/kg
Raw Carrots	11	0	0.0
Processed Carrots	9	3	33.3	0.13	0.300	0.043
Deep frozen Carrots	5	5	100.0	0.085	0.099	0.056

* Based on samples with quantities ≥0.01 mg/kg≥

 

 

Illustration 3: Carrots, raw and processed (May to Oct. 2014)

 

The investigations will continue.

 

For more information, see our Internet articles:

• “Chlorate Residues in Plant-Based Food: Origin Unknown“
• "Chlorate Residues in Carrots Traced to Chlorinated Water Used in Post-Harvest Treatment“

 

Translation

 Catherine Leiblein

 

Artikel erstmals erschienen am 09.04.2015