New Discovery: Perchlorate Contamination in Foods of Plant Origin

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New Discovery: Perchlorate Contamination in
Foods of Plant Origin
(August 2012 - June 2013)

Current news

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.

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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.


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]
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]
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            Info Box
            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

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].


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:

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
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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.

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.
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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.
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Table 1: Conventional and Organic Products With Higher Levels of
Perchlorate (≥ 0.1 mg/kg)#
     General                                                          Exhaustion of Preliminary
                                      Land of       Perchlorate
      Matrix          Matrix                                           BfR-Benchmark (EFSA
                                       Origin         (mg/kg)
     Category                                                           PRIMo Model) (%), [3]
                       Basil         Germany            0.32                     2
                                     Germany            0.10                          0.1
       Leaf           Savory
    Vegetables        Spinach          Italy            0.21                          48
                       Basil         Germany            0.12                          0.7
                                     Germany            0.88                          25
                      Tomato          Spain             0.40                          233
                      Tomato          Spain             0.31                          180
                       Melon        Costa Rica          0.16                          243
     Fruiting        Zucchini         Spain             0.32                          149
    Vegetables      Bell Pepper      Turkey             0.12                           76
                               1    Netherlands         0.33                          193
                     Zucchini          Spain            0.12                           56
                    Galia Melon        Spain            0.19                          288
                    Mandarine          Spain            0.20                          111
    Citrus Fruits
                     Grapefruit        Spain            0.18                          161
                    Mandarine          Chile            0.20                          111
  In violation of Article 2, Paragraph 2 of Regulation (EC) No. 315/93
  The source of increased levels of perchlorate in these samples has been traced to

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.
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Table 2: Perchlorate Findings in Conventional Foods, by Food Type

                         No.         No.    % With                                 Violations
Conventional           Samples    Findings Findings
                                                            Land of Origin             #           Amounts
                                                             Argentina (1),
                                                             Germany (1),
Berries & Grapes          52           6         12
                                                           Italy(1), Peru (1),
                                                               Spain (2),
                                                              Belgium (2),
                                                             Germany (24),
                                                                                                  0.12; 0.21;
Leaf Vegetables           61          38         62       Israel (3), Italy (5),       4
                                                                                                  0.32; 0.88
                                                               Kenya (1),
                                                              unknown (3)
                                                            Brazil (1), Costa
Exotic Fruit              69          10         14      Rica (3), Ghana (5),
                                                                 Italy (1)
                                                          Belgium (1), Brazil
                                                         (9), Costa Rica (12),
                                                             Germany (3),
                                                          Honduras (1), India
                                                                                                0.12 (3x); 0.16;
                                                              (1), Italy (1),
                                                                                                  0.19; 0.21;
Fruit Vegetables         144          76         53           Morocco (5),             7
                                                                                                  0.31; 0.32;
                                                            Netherlands (1),
                                                                                                   0.40; 0.88
                                                          Portugal (1), Spain
                                                           (24), Turkey (15),
                                                              Uganda (1),
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
                                                              Belgium (2),
                                                              Germany (1),
Processed Food
                          40           8         20         Netherlands (1),
                                                               Turkey (3),
                                                              unknown (1)
                                                          Chile (1), China (1),
                                                           Italy (1), Peru (2),
Citrus fruits             81          27         33                                    3        0.18; 0.20 (2x)
                                                               Spain (20),
                                                                Turkey (2)
Total Results                603       167         28                                 14
 In violation of Article 2, Paragraph 2 of Regulation (EC) No. 315/93, Minimizing
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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

                          No.           No.         % With                                   #
Organic                 Samples      Findings      Findings
                                                              Land of Origin    Violations        Amounts
                                                               Germany (5),
Leaf Vegetables            14            8            57        France (1),          1              0.1
                                                                  Italy (2)
Exotic Fruit                 1           1                *   Costa Rica (1)
                                                                 Italy (1),
Fruit Vegetables           18            4            22      Netherlands(1),        1             0.33
                                                                 Spain (2)
 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
 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

*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
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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.

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
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high perchlorate content was traceable to a fertilizer. The investigations
will continue.

[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 PRIMo Model,,
         19 June, 2013

Photo Credits:
Melonen, R. Sturm,, Image-ID=471311
Grünkohl 1, gnubier,, Image-ID=316148
Paprika (Capsicum), Kurt F. Domnik,, Image-ID=554986
Rot wie die Hölle., D. Schelpe,, Image-ID=506242
Weinlese, J. Christ,, Image-ID=612202
Weintrauben, M. Heinemann,, Image-ID=83895
Einmal Pommes bitte, R. Sturm,, Image-ID=495847
Einsichten, berwis,, Image-ID=395721

Authors: Anne Wolheim, Diana Kolberg, Cristin Wildgrube,
Ellen Scherbaum.

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Description: 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.