New Discovery: Perchlorate Contamination in Foods of Plant Origin

Anne Wolheim, Diana Kolberg, Cristin Wildgrube, Ellen Scherbaum

 

(August 2012 – June 2013)

 

From August 2012 to June 2013, 747 samples of plant-based foods were analyzed for the presence of perchlorate using a method developed at CVUA Stuttgart.
 

Approximately 70 % of the plant-based samples were free of perchlorate. However, the analyses of conventionally produced foods revealed conspicuously high levels of perchlorate (> 0.1 mg/kg) in 14 of the 603 samples (2.3 %). Among the organically grown food samples 1.4 % were detected with 0.1 mg/kg and higher.

 

The foods most affected were leaf vegetables such as herbs and lettuce, fruiting vegetables such as tomatoes and zucchini, and citrus fruits. The quantity was so high in a few isolated cases that, according to the National Institute for Risk Assessment (BfR), especially sensitive population groups such as children cannot be adequately protected because it can lead to a (reversible) inhibition of iodine intake in the thyroid. [1] Our investigatory results indicate that perchlorate contamination can occur in the fruit as well as on the surface. We were able to confirm this in distribution experiments on, e.g. melons and grapefruit.

 

Foods that contain overly high quantities of perchlorate may not be sold, due to health risks. In keeping with the dictate of minimizing foreign substances in foods, producers and sellers are fundamentally required to ascertain the cause of these substances and to remove them from sale. The investigations will continue.

 

Introduction

Substance, Occurrence and Usage

Perchlorates are the salts derived from perchloric acid. They are usually easily dissolved in water and are persistent (long-lasting) in the environment, where they can be anthropogenically caused (by humans) as well as found in mineral deposits. Perchlorate can also grow out of oxidative processes in the atmosphere where they settle onto dust particles in the air. [2]

Chemical structure of perchlorate

The industrial use of perchlorate is extensive and diverse. It is used for processing metal, refining paper, drainage, and oxidation, as well as for explosives and fuel. This widespread industrial use of perchlorates could be one reason for the contamination of foods. [2] Another reason could be the use of the fertilizer sodium nitrate, which is mined mainly in the Atacama Desert, where there is a huge natural deposit. Perchlorate accumulates in such dry regions because there is little precipitation by which it could get into the water cycle and be degraded by micro-organisms. [3]

Illustration 1: Chemical structure of perchlorate

 

Legal Background

Perchlorates are not currently authorized in the EU as pesticides or biocides. Perchlorate findings, therefore, fall under the regulations of the contamination ordinance, a precautionary measure to protect consumers vis-a-vis a general minimizing of foreign substances in foods. There is no legal maximum limit for contamination with perchlorate as of yet. [1]

 

Info Box

Contaminants

Contaminants are undesireable substances that, although not intended, get into foods as a result of environmental pollution or residues that come about from, e.g. the harvesting, production, processing, or preparation of food.  Many substances find their way into the environment because of industrial usage (e.g. PCBs and heavy metals) or as unintended by-products (e.g. dioxins). Depending on their characteristics, they can occur in or on food, or even be enriched. Other substances develop when food isn’t properly produced or handled (e.g. PAHs, nitrosamines). When food isn’t properly stored or when the growth or harvest conditions aren’t appropriate, natural contaminants such as molds and bacterial toxins can develop. In the interest of consumer protection it is absolutely necessary to minimize toxic contaminants such as perchlorate in food as much as possible.

 

Toxicological Background

The consumption of perchlorate leads to a (reversible) inhibition of iodine intake by the thyroid. Long-term suppression of iodine absorption can lead to a change in the thyroid’s hormone level, which can severely impair one’s health.
On the basis of currently available information, the BfR has compiled preliminary recommendations regarding a health-based valuation of perchlorate found in foods. The institute recommends employment of the standard procedures used for analyzing pesticide residues, as long as the assessment of entry pathways has not been completed. This means that, for every type of food, interpretation of the findings must consider several factors, including the quantity of the food normally consumed ((European Food Safety Authority (EFSA) PRIMo Model)) [1, 4].

 

Analytics

A description of the analytical method developed by CVUA Stuttgart in 2012 is available via download from the following link from the homepage of the European Reference Laboratory for single determination methods:

http://www.crl-pesticides.eu/docs/public/tmplt_article.asp?CntID=887&LabID=200&Lang=EN
 

Further information on methods can also be found in the 2nd issue of CVUA Stuttgart’s E-Journal:

“Analysis of Perchlorate in Food Samples of Plant Origin Applying the QuPPe-Method and LC-MS/MS”, May 2013

 

Test results from supermarket samples

From August 2012 to June 2013, 747 samples of fruit, vegetables and processed food products were analyzed for perchlorate.  Of these samples, 183 contained perchlorate in quantities above the MRL of 0.002 mg/kg, of which 16 contained > 0.1 mg/kg (see Illustration 2).

 

Illustration 2: Overview of all results from the analyses of perchlorate since August 2012.

Illustration 2: Overview of all results from the analyses of perchlorate since August 2012.

 

The foods most affected by perchlorate were leaf vegetables, fruiting vegetables and citrus fruits. Perchlorate contamination was detected in 46 of the 75 leaf vegetable samples (61 %). Five samples (2 basil, spinach, lettuce and savory) with high quantities of perchlorate (≥ 0.1 mg/kg) were in violation of the contamination ordinance. Further evidence of perchlorate was found in 80 of the 162 samples of fruit vegetables (49 %). Eight of these samples (2 tomatoes, cucumber, bell pepper, 2 zucchini and 2 melons) were conspicuous for their higher quantities. Of all the fruit samples, citrus fruits were most likely to contain perchlorate; detection was made in 28 of the 100 samples analyzed (28 %). Three of the samples (2 mandarines, grapefruit) were in violation of the contamination ordinance, with a content of ≥ 0.1 mg/kg.

 

Illustration 3: Overview of perchlorate findings, itemized by product group.

Illustration 3: Overview of perchlorate findings, itemized by product group.

 

 

In 16 food samples (conventional and organic), mostly in fresh vegetables, (13 samples; 4.6 % of all analyzed vegetable samples) perchlorate was detected in amounts of ≥ 0.1 mg/kg. Just 1.1 % of the fruit samples contained amounts of ≥ 0.1 mg/kg. A list of all samples with a quantity of ≥ 0.1 mg/kg can be found in Table 1.

 

Table 1: Conventional and Organic Products With Higher Levels of Perchlorate (≥ 0.1 mg/kg)#
General Matrix Category Matrix Land of Origin Perchlorate (mg/kg) Exhaustion of Preliminary BfR-Benchmark (EFSA PRIMo Model) (%), [3]
Leaf Vegetables

Basil1

Germany

0,32

2

Organic Savory

Germany

0,10

0,1

Spinach

Italy

0,21

48

Basil

Germany

0,12

0,7

Field Lettuce

Germany

0,88

25

Fruiting Vegetables

Tomato

Spain

0,40

233

Tomato

Spain

0,31

180

Melon

Costa Rica

0,16

243

Zucchini

Spain

0,32

149

Bell Pepper

Turkey

0,12

76

Organic Cucumber1

Netherlands

0,33

193

Zucchini

Spain

0,12

56

Galia Melon

Spain

0,19

288

Citrus Fruits

Mandarine

Spain

0,20

111

Grapefruit

Spain

0,18

161

Mandarine

Chile

0,20

111

#In violation of Article 2, Paragraph 2 of Regulation (EC) No. 315/93.
1 The source of increased levels of perchlorate in these samples has been traced to fertilizer.

 

Conventionally Produced Foods

The majority of the 747 samples came from conventional cultivation (603 samples). 167 of these (28 %) were detected with perchlorate. Table 2 presents an overview of the conventionally produced food samples containing perchlorate.

 

Table 2: Perchlorate Findings in Conventional Foods, by Food Type
Conventional No. Samples No. Findings % With Findings Land of Origin Violations# Increased Amounts (mg/kg)
Berries & Grapes

52

6

12

Argentina (1),

Germany (1), Italy(1), Peru (1), Spain (2),

 

 

Leaf Vegetables

61

38

62

Belgium (2),

Germany (24), 

Israel (3), Italy (5),

Kenya (1),

unknown (3)

4

0,12; 0,21; 0,32; 0,88

Exotic Fruit

69

10

14

Brazil (1), Costa Rica (3), Ghana (5), Italy (1)

 

 

Fruit Vegetables

144

76

53

Belgium (1), Brazil (9), Costa Rica (12), Germany (3), Honduras (1), India (1), Italy (1), Morocco (5), Netherlands (1), Portugal (1), Spain (24), Turkey (15), Uganda (1), unknown(1)

7

0,12 (3x); 0,16; 0,19; 0,21; 0,31; 0,32; 0,40; 0,88

Cereals

14

 

 

 

 

 

Cereal Products

1

 

 

 

 

 

Legumes

12

 

 

 

 

 

Potatoes

18

1

6

Italy

 

 

Seed Fruits

17

 

 

 

 

 

Mushrooms

48

 

 

 

 

 

Baby Food

2

 

 

 

 

 

Sprout Vegetables

42

1

2

Spain

 

 

Stone Fruits

2

 

 

 

 

 

Processed Food Products

40

8

20

Belgium (2), Germany (1), Netherlands (1),

Turkey (3),

unknown (1)

 

 

Citrus fruits

81

27

33

Chile (1), China (1),

Italy (1), Peru (2),

Spain (20), Turkey (2)

3

0,18; 0,20 (2x)

Total Results

603

167

28

 

14

 

# In violation of Article 2, Paragraph 2 of Regulation (EC) No. 315/93, Minimizing Requirement

 

Organically Produced Foods

A further 144 samples from organic production were also analyzed for perchlorate. The investigations revealed evidence of perchlorate in 16 samples (11 %), two of which contained ≥ 0.1 mg/kg. A summary of the perchlorate findings in organic foods can be found in Table 3.

 

Table 3: Perchlorate Findings in Organic Foods, by Food Type
Organic No. Samples No. Findings % With Findings Land of Origin Violations# Increased Amounts (mg/kg)
Berries

22

 

 

 

 

 

Leaf Vegetables

14

8

57

Germany (5),

France (1), Italy (2)

1

0,1

Exotic Fruit

1

1

*

Costa Rica (1)

 

 

Fruit Vegetables

18

4

22

Italy (1), Netherlands(1), Spain (2)

1

0,33

Cereal

9

 

 

 

 

 

Cereal Products

1

 

 

 

 

 

Spices

1

1

*

Germany

 

 

Legumes

20

1

5

Germany

 

 

Potatoes

3

 

 

 

 

 

Wine Grapes

3

 

 

 

 

 

Seed Fruit

3

 

 

 

 

 

Mushrooms

2

 

 

 

 

 

Baby Food

13

 

 

 

 

 

Sprout Vegetables

2

 

 

 

 

 

Stone Fruit

1

 

 

 

 

 

Processed Food Products

11

 

 

 

 

 

Wine

1

 

 

 

 

 

Citrus Fruit

19

1

5

Spain

 

 

Total Results

144

16

11

 

 2

 

# In violation of Article 2, Paragraph 2 of Regulation (EC) No. 315/93, Minimizing Requirement
*No. of analyses too small for statistical significance

 

Analysis of Perchlorate Contamination in Foods with Inedible Skin Conducted Separately

More detailed data regarding the assessment of perchlorate (processing factors, food skin/peel factors, and further toxicological information) is not currently available, according to the BfR. [1] Therefore, several positive samples with inedible skins were reevaluated, analyzing the skins separately from the fruit.
In the melons the amount of perchlorate detected in the separately tested skins was twice as high as that found in the fruit. In the one grapefruit sample the perchlorate was found mainly in the peel. The findings of these separate analyses are presented in Table 4.

 

Table 4: Perchlorate Analyses of Fruit and Peel
 
Quantity of Perchlorate in mg/kg
Type of Sample
Whole Fruit
Peel
Fruit Flesh
Honey Melon

0,081

0,160

0,052

Galia Melon

0,042

0,089

0,024

Galia Melon

0,047

0,093

0,029

Galia Melon

0,043

0,10

0,033

Cantaloupe Melon

0,076

0,16

0,036

Cantaloupe Melon

0,086

0,21

0,064

Grapefruit

0,021

0,043

0,005

 

To better assess the amount of perchlorate in or on the fruit, the quantity  was converted, based on the weight of the specific part (skin or fruit flesh) being analyzed.

 

Illustration 4: Presentation of the perchlorate findings, in reference to the absolute distribution in the fruit.

Illustration 4: Presentation of the perchlorate findings, in reference to the absolute distribution in the fruit.

 

The absolute quantities of perchlorate detected in melon showed that the amounts were similarly high in both the peel and the fruit flesh (e.g. honey melon: peel 0.067 mg vs. flesh 0.056 mg; see Illustration 4). In contrast, the flesh of the grapefruit contained much less perchlorate than the peel (0.003 mg vs. 0.012 mg; see Illustration 4).

 

The analytical results of the grapefruit clearly show that a surface treatment could have occurred. More tests must follow, nevertheless. The results of the melons do not point to a surface treatment alone; an application of perchlorate on the plant roots is also a possibility that must be taken into consideration. In certain individual cases the source of the high perchlorate content was traceable to a fertilizer.

 

The investigations will continue.

 

Literature

[1]       Recommendation of the BfR regarding the health-based evaluation of perchlorate residues in food, Policy Brief No. 015/2013 from 6 June, 2013

[2]       Report of the Federal Environment Agency (Umweltbundesamt) on the occurrence and application of perchlorates as well as their principal entry pathways into foods, 18 Sept., 2012

[3]       Wikipedia, keyword "Perchlorate"

[4]       EFSA-Modell PRIMo, 19.06.2013

 

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Bericht erschienen am 27.06.2013 15:17:30