Perchlorate Residues in Plant-Based Food – an Update

Ein Bericht aus unserem Laboralltag

Dr. Ingrid Kaufmann-Horlacher

 

Photo: Vegetables.

 

Since the publication of our test results on perchlorate residues in plant-based foods in June 2013 [1], more than 3,000 samples have been analyzed. The situation hasn’t changed drastically since then, but a shift toward lower levels has been observed. Nevertheless, individual cases of high quantities still exist. In the time period of March 2014 to February 2015 the percentage of samples containing perchlorate residues over 0.1 mg/kg was 1.5 %, including an extremely high level of 3.9 mg/kg in a German-grown sample of spinach. Among 1,900 samples analyzed during this time just two spinach samples (0.1 %) were verified as containing levels above the reference value that has been valid thus far, established by the Standing Committee for the Food Chain and Animal Health (SCoFCAH) [2]. In October 2014 the European Food Safety Authority (EFSA) published a risk assessment for perchlorate residues in food [3] from which, in comparison to the previously set toxicological reference value, a very low value for the acceptable daily intake (ADI) of perchlorate was established. In reaction, the Standing Committee for Plants, Animals, Food and Feed (SC PAFF) agreed upon new reference values for perchlorate residues in plant-based food for intra-Community trade [4]. Despite the new, extremely low ADI value, the reference values were only moderately changed, however. If one retroactively applies these new reference values (as of 16 March, 2015) to the samples analyzed between March 2014 and February 2015, the picture looks only slightly different; a maximum of seven samples (0.4 %) exceed the new reference values with verification.

 

Infokasten

Perchlorate

Perchlorates are the salts derived from perchloric acid. They are easily dissolved in water and are relatively stable. Perchlorates are persistent in the environment and are considered ubiquitous environmental contaminants. Their presence in nature can stem from both anthropogenic (man-made) and natural sources, including the usage of natural fertilizers such as Chile saltpeter, industrial emissions, the natural formation of perchlorate in the atmosphere and surface water, as well as its formation during the disinfection of water with sodium hypochloride. Plants absorb perchlorate mostly from the roots; thus, the most critical pathway for perchlorate into food is via perchlorate-containing fertilizers, perchlorate-contaminated soil, and the irrigation of plants using perchlorate-contaminated water.

 

The ingestion of perchlorate leads to the reversible inhibition of iodine intake in the thyroid. Extreme iodine deficiency in humans can lead to a lack of thyroid hormones (hypothyroidism). Even a small to moderate deficiency of iodine can lead to the formation of a goiter or to hypotheyroidism.

 

Our Analytical Results

On 20 June, 2013 the results of our investigations on perchlorate residues were published under the title "New Discovery: Perchlorate Contamination in Foods of Plant Origin". Almost 25 % of the analyzed plant-based food samples contained perchlorate residues in amounts over the limit of detection and 2.1 % were higher than 0.1 mg/kg. Since the publication of these findings 3,000 additional plant-based food samples have been tested for the presence of perchlorate residues (see Illustration 1). In 76.2 % of the samples analyzed since June 2013 either no residues or quantities less than 0.005 mg/kg were detected. The percentage of samples containing residues above 0.1 mg/kg lies at 1.9 % in the time period of June 2013 to February 2015.

 

Illustration 1: Comprehensive overview of plant-based food samples analyzed for perchlorate following our first report, from June 2013 to February 2015.

Illustration 1: Comprehensive overview of plant-based food samples analyzed for perchlorate following our first report, from June 2013 to February 2015.

 

The residue situation has not drastically changed since our last report (June 2013). The percentage of samples with residues stayed almost the same, although a slight shift in the direction of lower residue values was observed. Illustration 2 depicts the percentages of samples with different concentrations of perchlorate residues in three time periods, in which the first period refers to the timing of our first report (August 2012 to May 2013). In the second timeframe of June 2013 to February 2014, only certain food groups were chosen for analysis within the framework of our perchlorate project. From March 2014 perchlorate investigations were integrated into our routine analyses, thereby covering all plant-based foods included in the Baden-Württemberg pesticide residue analysis program. The third time period encompasses the period from March 2014 to February 2015, and will be presented in further detail.


Illustration 2 shows clearly that the number of samples with perchlorate residues ranging from 0.01 mg/kg to 0.5 mg/kg declined over time. The few cases with higher quantities of residues hardly changed in the last years, and individual cases of high levels continue to exist.

 

Illustration 2: Percentage of samples with perchlorate residues in different concentrations, in the three time periods of July 2012 to May 2013, June 2013 to February 2014, and March 2014 to February 2015.

Illustration 2: Percentage of samples with perchlorate residues in different concentrations, in the three time periods of July 2012 to May 2013, June 2013 to February 2014, and March 2014 to February 2015.

 

Current Analytical Results (March 2014 to February 2015)

All pesticide samples have been routinely analyzed for perchlorate since March 2014. The following data refer exclusively to the time period of March 2014 to February 2015. Illustration 3 depicts the number of samples analyzed during this time, grouped by levels of residue concentration. A total of 1,900 samples were analyzed for perchlorate, 76.6 % of which contained residues in levels under the limit of determination (0.005 mg/kg). On the other hand, 283 samples (14.9 %) were detected with perchlorate residues over 0.01 mg/kg. Four samples (0.2 %) contained residues over 0.5 mg/kg, with the highest level of 3.9 mg/kg detected in a German-grown sample of spinach.

 

Illustration 3: Number (and percent) of samples, grouped by levels of concentration (in mg/kg) from the investigative period of March 2014 to February 2015.

Illustration 3: Number (and percent) of samples, grouped by levels of concentration (in mg/kg) from the investigative period of March 2014 to February 2015.

 

Perchlorate was detected mostly in leafy vegetables, fruit vegetables and citrus fruit; leafy vegetables in particular contained the higher levels. Cereals, cereal products and potatoes were free of perchlorate residues in the time period of March 2014 to February 2015, and the quantities measured in pome and stone fruits as well as sprouts were under 0.02 mg/kg for all analyzed samples in this timeframe. Dried fruit- and mushroom products tend to have higher levels of perchlorate residues; when recalculating the measurements taking the water content into consideration residues of the unprocessed fruits were in the lower concentration levels. Illustration 4 depicts the samples itemized by concentration levels of residues detected and by type of food. Tables 1 and 2 show the percentage of samples containing residues and the average and highest amounts of residues, grouped by type of food and by conventional vs. organic production.

 

Illustration 4: Overview of perchlorate findings above 0.005 mg/kg, itemized by type of food, in the time period of March 2014 to February 2015.

Illustration 4: Overview of perchlorate findings above 0.005 mg/kg, itemized by type of food, in the time period of March 2014 to February 2015.

 

There was no significant difference in perchlorate test results between conventional and organic production. The percentage of samples with perchlorate residues and the average amount therein was similar between the two groups, as can be seen in Tables 1 and 2.

 

Table 1: Overview of samples from conventional production, in the investigatory time period of March 2014 to February 2015.
Type of Food No. Samples Findings > 0.005 mg/kg % Average* mg/kg Maximum mg/kg

Berries

231

21

9.1

0.020

0.14

Leafy vegetables

298

149

50.0

0.073

3.9

Exotic Fruit

128

17

13.3

0.027

0.063

Fruit vegetables

314

126

40.1

0.029

0.35

Vegetable products / mixtures

59

8

13.6

0.010

0.021

Cereals/Cereal products

33

0

0

 

 

Spices/Tea

2

2

 

0.138

0.18

Legumes

3

1

   

0.044

Potatoes/Tapioca

33

0

0

   

Pome fruit

94

1

1.1

 

0.006

Chestnuts

6

0

0

   

Fruit products

41

7

17.1

0.028

0.14

Mushrooms

34

1

2.9

0.006

0.006

Mushroom products

35

8

22.9

0.082

0.22

Fruit/Wine/Beer

9

1

11.1

 

0.057

Baby food

5

0

0

   

Sprouts

84

7

8.3

0.008

0.010

Stone fruit

107

5

4.7

0.012

0.019

Root vegetables

68

10

14.7

0.012

0.026

Citrus fruit

80

24

30.0

0.019

0.066

TOTAL

1,664

388

23.3

0.045

3.9

*Average of all samples with residues

 

Table 2: Overview of samples from organic production, in the investigatory time period of March 2014 to February 2015.
Type of Food No. Samples Findings > 0.005 mg/kg % Average* mg/kg Maximum mg/kg

Berries

13

1

7.7

 

0.028

Leafy Vegetables

36

19

52.8

0.025

0.092

Exotic Fruit

7

1

14.3

 

0.011

Fruit Vegetables

43

11

25.6

0.038

0.19

Vegetable products

26

14

53.8

0.037

0.13

Cereals/Cereal products

3

0

0

   

Potatoes

7

0

0

   

Pome fruit

13

0

0

   

Fruit products

10

1

10.0

 

0.011

Mushrooms

12

0

0

   

Juice

1

0

0

   

Baby food

8

1

12.5

 

0.007

Sprouts

16

3

18.8

0.009

0.010

Stone fruit

14

2

14.3

0.009

0.010

Tea

1

1

 

 

0.40

Root vegetables

10

1

10.0

 

0.006

Citrus fruits

16

2

12.5

0.009

0.010

TOTAL

236

57

24.2

0.034

0.40

*Average of all samples with residues

 

A conventionally grown sample of spinach from Germany had by far the highest amount of perchlorate found during the time period of March 2014 to February 2015, at 3.9 mg/kg. All samples containing perchlorate residues above 0.1 mg/kg are presented, together with their countries of origin, in Table 3. Fresh herbs appear often in this table. The chlorate residues are also presented.

 

Table 3: Samples with higher perchlorate residues (>0.1 mg/kg) together with their chlorate residues, in the time period of March 2014 to February 2015.
Matrix Country of Origin Perchlorate mg/kg Chlorate mg/kg

Spinach

Germany

3.9

0.01

Basil

Germany

0.69

0.024

Spinach

Germany

0.64

< 0.005

Lamb’s lettuce

Germany

0.54

0.059

Jasmine tea

China

0.4

0.055

Tomato

Turkey

0.35

0.019

Tarragon

Germany

0.34

< 0.005

Tomatoes

Germany

0.3

0.005

Green beans

Spain

0.28

< 0.005

Basil

Germany

0.27

0.048

Chives

Germany

0.26

< 0.005

Chives

Germany

0.24

< 0.005

Dried shiitake mushrooms

Thailand

0.22

0.068

Rucola

Italy

0.21

0.36

Lamb’s lettuce

Germany

0.19

< 0.005

Basil

Germany

0.19

0.059

Melon

Brasil

0.19

< 0.005

Bell pepper

Netherlands

0.19

< 0.005

Thyme

Unknown

0.18

< 0.005

Dried shiitake mushrooms

Unknown

0.17

0.078

Green beans

Spain

0.16

0.22

Green beans

Spain

0.15

< 0.005

Raisins

Unknown

0.14

0.024

Basil

Germany

0.14

< 0.005

Table grapes

Chile

0.14

< 0.005

Broccoli TK

Unknown

0.13

0.013

Dill

Germany

0.13

0.061

Bell pepper

Turkey

0.11

< 0.005

Green highlights: samples from organic production.

 

A large proportion of samples containing higher perchlorate values came from Germany, as can be seen in Table 3. This can be accounted for by the fact that most of the leafy vegetable samples, which is the food category with the highest level of residue contamination (see Illustration 4), came from Germany. Fully 70 % of the leafy vegetables, including fresh herbs, were German grown, whereby approximately 37 % of all the analyzed samples came from Germany. The percentage of German-grown samples containing perchlorate residues over 0.005 mg/kg was 22.3 %, close to the average of 23.4 % for all samples. The percentages of samples from Spain and Turkey were significantly higher than the average, at 38,7 % and 37,5 % respectively, while those from the Netherlands and non-EU countries showed 19 % and 18.6 % respectively. Among EU countries excluding Germany, Spain, France, Belgium, Netherlands and Italy, the percentage of samples with residues over 0.005 mg/kg was just 2 %. Samples without information as to their country of origin were detected with residues over 0.005 mg/kg in 19.9 % of cases. Table 4 presents an overview of the countries of origin, the average number of samples containing residues in different concentrations, and the maximum amounts detected.

 

Table 4: Overview of all samples analyzed for perchlorate, by country of origin (March 2014 to Feb¬ruary 2015).
Country of Origin
No. Samples
Findings > 0.005 mg/kg
Findings > 0.05 mg/kg
Findings > 0.1 mg/kg
Average* mg/kg
Maximum mg/kg
Germany
708
158 (22,3%)
26 (3,7%)
13 (1,8%)
0,070
3,9
Non-EU
393
73 (18,6%)
11 (2,8%)
4 (1,0%)
0,031
0,40
Spain
225
87 (38,7%)
4 (1,8%)
3 (1,3%)
0,022
0,28
Unknown
196
39 (19,9%)
10 (5,1%)
4 (2,0%)
0,041
0,18
Italy
145
37 (25,5%)
5 (3,4%)
1 (0,7%)
0,026
0,21
Turkey
64
24 (37,5%)
3 (4,7%)
2 (3,1%)
0,033
0,35
Netherlands
63
12 (19%)
4 (6,3%)
1 (1,6%)
0,045
0,19
Other EU countries
49
1 (2,0%)
0
0
0,010
0,010
France
37
9 (24,3%)
0
0
0,016
0,029
Belgium
20
5 (25,0%)
2 (10,0%)
0
0,038
0,094
Total
1900
445 (23,4%)
65 (3,4%)
28 (1,5%)
0,044
3,9

*Average of all samples with residues

 

Perchlorate and Chlorate Residues

In the current reporting period of March 2014 to February 2015 perchlorate residues in amounts over 0.005 mg/kg were detected in 445 of 1,900 (23.4 %) plant-based food samples. In addition to perchlorate, 109 samples (5.7 %) also contained chlorate residues (>0.005 mg/kg). In 16 samples (0.8 %) that already contained perchlorate residues the amount of chlorate residues exceeded 0.1 mg/kg.

 

Perchlorate residues over 0.1 mg/kg were detected in 28 samples; 14 of these – that is, half of all the samples with high levels of perchlorate – also contained chlorate (>0.005 mg/kg). Two samples (0.1 %) contained both perchlorate and chlorate residues in amounts exceeding 0.1 mg/kg. These concerned green beans from Spain, with 0.16 mg/kg perchlorate and 0.22 mg/kg chlorate, and rucola from Italy, with 0.21 mg/kg perchlorate and 0.36 mg/kg chlorate (see also Table 3).

 

Infokasten

Contaminants

“Contaminant” means any substance not intentionally added to food which is present in such food as a result of the production (including operations carried out in crop husbandry, animal husbandry and veterinary medicine), manufacture, processing, preparation, treatment, packing, packaging, transport or holding of such food, or as a result of environmental contamination (Article 1 of (EEC) Regulation No. 315/93).

 

Contaminants can end up in food at every level, from manufacturing to consumption.

 

Contaminant levels shall be kept as low as can reasonably be achieved by following good practices at all stages (Article 2) (ALARA-Principle: as low as reasonably achievable).

 

Tolerable Daily Intake (TDI)

Contaminants are undesirable substances. The toxicological reference value for a contaminant is thus designated as Tolerable Daily Intake (TDI), and not as Acceptable Daily Intake (ADI) as is used, for example, for plant protection substances.
The TDI stipulates the daily amount that can be ingested over a life span, without any risk of undesirable health effects.

 

Acute Reference Dose (ARfD)

An acute reference dose (ARfD) is normally derived for substances that have an acute toxicity (harmful effect after a single ingestion). The ARfD is defined as the amount of a substance a person can consume, over the period of one day, at one meal, or over several meals without any recognizable health risk. Short-term studies are usually used for the determination of the ARfD.

 

Legal evaluation of perchlorate residues

Reference value of the Standing Committee:

On 16 July, 2013 the Standing Committee for the Food Chain and Animal Health (SCoFCAH) made a joint declaration regarding perchlorate reference values for plant-based food for intra-Community trade [2]. Table 5 shows the perchlorate amounts measured at over 0.1 mg/kg in various samples during the time period of March 2014 to February 2015, in comparison to the reference values of SCoFCAH from 16 July, 2013.

 

Table 5: Samples with higher perchlorate residues from the time period of March 2014 to February 2015, in relation to the reference values established by SCoFCAH on 16 July, 2013.
Category
Perchlorate Reference Value
(SCoFCAH, 16.7.13)
Perchlorate amounts in various samples in mg/kg
(March 2014 – February 2015)
(only samples > 0.1 mg/kg)
No. samples verified as exceeding reference value**
Herbs from greenhouses or fields under plastic
1,0
Basil 0.69; 0.27; 0.19; 0.14;
Tarragon 0.4;
Chives 0.6; 0.24;
Thyme 0.18;
Dill 0.13
*
0
Leafy vegetables (excluding spinach), celery from greenhouses or fields under plastic
1,0
Lamb’s lettuce 0,54;
Rucola 0,21,
Lamb’s lettuce 0,19;
*
0
Citrus, pome fruit, root and tuber vegetables, table grapes, spinach, melons, watermelons
0,2
Spinach 3,9; 0,64;
Melons 0,19;
Table grapes 0,14;
2
Fruit and vegetables other than the above-mentioned categories
0,5
Jasmine tea 0,4;
Tomatoes 0,35; 0,3;
Green beans 0,28; 0,16; 0,15;
Pointed peppers 0,19;
Raisins 0,14;
Broccoli 0,13;
Bell peppers 0,11;
0

* Allocated with the assumption that these samples came from greenhouses or fields under plastic.
** For the determination of whether a reference value was exceeded, an analytical variability of 50% for plant-based samples must be taken into consideration. This is based on the findings of a large scale, EU-wide comparison of laboratories regarding the investigation of pesticide residues.

 

From a total of 1,900 samples analyzed for the presence of perchlorate residues in the time period of March 2014 to February 2015, just two spinach samples (0.1 %) were verified as having exceeded the reference value established by SCoFCAH. This is also based on the assumption that the lamb’s lettuce, rucola and fresh herbs were grown outdoors.

 

Application of the reference values from SCoFCAH listed in Table 5 were limited to the time until which the European Food Safety Authority (EFSA) provided a risk analysis for perchlorate.

 

Scientific Opinion of EFSA:

The European Food Safety Authority’s panel for Contaminants in the Food Chain (CONTAM) presented its scientific opinion [3] on the health risks related to perchlorate in food, especially in fruit and vegetables, on 17 October, 2014. A newly derived Tolerable Daily Intake (TDI) of 0.3 µg per kg bodyweight per day was thereby established, based on the inhibition of iodine intake by the thyroid in healthy adults (EFSA Journal 2014, 12(10); p. 3,869). This value is significantly lower than the Provisional Maximum Tolerable Daily Intake (PMTDI) of 10 µg per kg bodyweight per day, derived for perchlorate in 2010 by the Joint FAO/WHO Expert Committee on Food Additives (JECFA).

 

The derivation of an acute reference dose (ARfD) was not deemed necessary by EFSA. It is not expected by EFSA that the short-term intake of perchlorate in amounts typically found in food and water would result in unwanted health effects, also when consumed by sensitive groups of people. Nevertheless, EFSA expressed certain concern about the chronic intake of perchlorate by younger people with low to middle levels of iodine deficiency and the short-term exposure by breast-fed babies and young children who get little iodine in their diet.

 

Based on EFSA’s risk evaluation, the Standing Committee for Plants, Animals, Food and Feed (SCoPAFF) set new reference values [4] for intra-Community trade at their session on 10 March, 2015 (see Table 6). These values are to be used from 16 March, 2015. At the same time, member states should provide further data on perchlorate residues in food in order to faciliate a more exact risk evaluation.

 

Table 6: Reference values for perchlorate residues in plant-based foods, in accordance with the decision of SC PAFF from 10 March, 2015.
Categories
Perchlorate Reference Values (SC PAFF, 10.03.2015) mg/kg
Fruit and vegetables, with exception of:    
0,1
  Pumpkin family and leafy vegetables, with exception of:  
0,2
    Celery and spinach from greenhouse/ field under plastic
0,5
    Herbs, rucola, head lettuce, lettuce from greenhouse/field under plastic
1,0
Dried spices, dried hops    
0,5
Tea (Camilla sinensis)    
0,75
Herbal and Fruit Tea    
1,0
Ready-to-eat food for babies and young children    
0,02
Other food    
0,05

 

If we applied the new reference values to the investigative results from the previously mentioned time period (March 2014 to February 2015), we would see a picture that was only slightly changed. Among the total of 1,900 analyzed samples, depending on whether the commodities were grown under glass/plastic or in open fields, just 4 (0.2%) or 7 (0.4%) respectively would then be verified as having exceeded the new reference values.

 

In accordance with the contaminants ordinance, CVUA Stuttgart will continue to evaluate food for elevated perchlorate residues and to refer investigative results to the official food inspection authorities. This is in keeping with the minimization imperative as found in Article 2, Paragraph 2 of Regulation (EC) No. 315/93 and the reference values established by the Standing Committee, in order to achieve a minimization of residues from these unwanted contaminants.

 

Photo credits:

CVUA Stuttgart.

 

Sources:

[1] New Discovery: Perchlorate Contamination in Foods of Plant Origin
[2] http://ec.europa.eu/food/food/chemicalsafety/contaminants/statement-perchlorate_en.pdf
[3] www.efsa.europa.eu/efsajournal
[4] http://ec.europa.eu/food/food/chemicalsafety/contaminants/ docs/statement_perchlorate_in_food_en.pdf

 

Artikel erstmals erschienen am 01.06.2015