Fish in Prague’s rivers and ponds are less contaminated with toxic mercury than fish bought in Prague food stores

24.11.2019 - PRAGUE

Two out of 14 fish samples caught in Prague’s River Vltava slightly exceeded the safe levels recommended by US authorities. For purchased fish samples, five out of 28 did not meet the limit, while one sample exceeded the daily recommended dose by more than five times. This was revealed by a study from Arnika investigating mercury contamination in fish in Prague. The highest levels were found in predatory fish, whose frequent consumption should be avoided, especially by high-risk populations, which include pregnant women and small children. Mercury can damage the nervous and cardiovascular systems in particular.

The mercury intake of the general population comes primarily from fish and shellfish. Arnika therefore commissioned an analysis of 14 fish samples from six locations on the River Vltava, as well as the Motolský and Kyjský Ponds, at the State Veterinary Institute in Prague. The safe levels for mercury intake of 0.22 mg/kg [i] were exceeded in two samples – bream caught in still waters of the River Vltava near Libeň (0.281 mg/kg) and perch from Klecánky, located at the first weir after the outlet of the Central Waste Water Treatment Facility in Podbaba (0.254 mg/kg), where mercury is stored in sediments.

In the second part of the study, a total of 28 samples of sea and freshwater fish purchased in Prague food stores and supermarkets were analysed, five of which did not comply with the safe dose recommended by the US authorities. The highest mercury concentrations were found in monkfish caught in the waters of Denmark (0.242 mg/kg) and tuna steak from Sri Lanka (0.317 mg/kg). Moreover, the mercury concentration in swordfish from Sri Lanka (1.117 mg/kg) exceeded the safe level of mercury by more than five times. The mercury concentrations did not exceed the European safe levels in any sample except for the swordfish purchased at the fish and vegetable market. However, the European limits are considered weak as they do not reflect the potential health risk, especially for vulnerable populations, which include pregnant women and small children. [ii].

Additionally, the study revealed mercury contamination of Prague citizens via an analysis of 10 hair samples from women between the ages of 24 and 53 living in Prague and eating fish regularly. Women of childbearing age are the most vulnerable group, because mercury specifically damages the nervous system in the foetus. The most toxic form – methylmercury – can cross the blood-brain and placental barriers, allowing it to react directly with brain and foetal cells.

Fortunately, the measured values from the women’s hair samples were not high, as they consume fish and seafood less frequently than women in maritime states such as Spain.
“Fish is an important source of omega-3 fatty acids. They are essential for healthy brain development in the foetus and small children. This is not to say that we should remove fish from children’s diets completely, but we should specifically avoid predatory fish. Our findings coincide with the withdrawal of 4500 cans of tuna baby food produced by the Hamé group, ordered by the State Veterinary Authority, because of dangerously increased mercury levels,” explains Karolina Brabcova from Arnika.

The largest sources of mercury pollution in Prague are the cement kiln of Ceskomomoravsky cement a.s. in Radotin and the Communal Waste Incinerator at Malesice and Central Waste Water Treatment Facility in Prague, at Podbaba on the River Vltava. The biggest sources of emissions of mercury into the air are brown coal power plants and local heating systems fuelled by coal.

“One of the main sources of mercury contamination in fish comes from industrial activities, including chlor-alkali plants or coal power plants. Toxic mercury travels via the air and water into rivers and oceans while bio-accumulating through the food chain as predators eat other organisms containing mercury and therefore bio-magnifying the mercury burden in their bodies. This way mercury ends up in our bodies primarily from eating certain types of predatory fish.

“By signing the Minamata Convention, the Czech Republic committed itself to restricting mercury emissions into the environment from all sources. It should therefore refrain from expanding coal mining and reject requested exemptions for coal-fired power plants in particular, as they constitute a significant source of mercury emissions globally,” adds Jindrich Petrlik, the head of Arnika’s Toxics and Waste Programme. The Conference of the Parties to the Minamata Convention meets in Geneva on 24th and 25th November 2019. Arnika will participate as an observer to influence politicians in their decisions toward a rapid phase-out of the use of mercury in products and processes, strict control of mercury emissions and the cleaning up of sites contaminated by mercury.

[i]  The recommended maximum levels of mercury in fish were calculated from the maximum daily intake level of 0,22 mg/kg  of mercury for consumers with average weight of 70 kg and above average fish consumption referring to one fish meal a week. (defined by US EPA)

[ii]  The EU limits for mercury in fish are 1 mg/kg for predatory fish and for the other fish  0,5 mg/kg of fresh weight.

Mercury concentrations in fish samples caught in water bodies in the Prague

Fish specie

N. of units in sample

Location

Mercury concentrations

(mg/kg of raw fish weight)

Roach

2

Podbaba – Roztocká. Vltava River below the outlet from the Central Waste Water Treatment Facility

0.161

Bream

2

Libeň. Povltavská. Vltava River

0.281

Perch

3

Libeň.  still water of Vltava River next to Rokytka Creek estuary

0.193

Perch

1

Klecánky. Vltava River

0.254

Roach

1

Klecánky. Vltava River

0.132

Carp

1

Kyjský Pond

0.117

Roach

1

Kyjský Pond

0.084

Roach

2

Motolský Pond

0.053

Carp

1

Motolský Pond

0.019

Mercury concentrations in fish samples bought in food stores in Prague

Specie

Country/place of origin

Mercury concentrations

(mg/kg of raw fish weight)

Turbot

Spain / sea (ocean)

0.037

Nile Perch

Tanzania / Lake Victoria

0.138

Yellow Fin Tuna

Oman/  sea (ocean)

0.317

Pike

Czech Republic / Chlumec nad Cidlinou (Pond)

0.067

Cod filets

USA / Pacific Ocean

0.081

Rainbow Trout

Turkey / freshwater fish farm

0.008

Rainbow Trout

Turkey / freshwater fish farm

0.010

Rainbow Trout filets

Turkey / freshwater fish farm

0.011

Canned cod liver

North East Atlantic Ocean

0.020

Canned Tuna

North East Atlantic Ocean

0.020

Canned Tuna

North East Atlantic Ocean

0.018

Cod filets

Bering Sea

0.012

Canned Tuna

Spain / sea (ocean)

0.269

Smoked Mackerel

Northern Sea

0.125

Swordfish filets

Srí Lanka / Indian Ocean

1.117

Eel

Czech Republic / Chlumec nad Cidlinou (Pond)

0.179

Monkfish

Denmark / Sea

0.242

Yellow Fin Tuna

Srí Lanka / Indian Ocean

0.296

Haddock filets

Norway / Atlantic Ocean

0.042

Tench

Czech Republic / Chlumec nad Cidlinou (Pond)

0.018

Salmon filets

Norway / fish farm

0.018

Rainbow Trout

Czech Republic / Chlumec nad Cidlinou (Pond)

0.029

Canned Cod liver

Norway / South East Atlantic Ocean

0.015

Canned Tuna

Ecuador / Pacific Ocean

0.119

Canned Cod liver

Island / Atlantic Ocean

0.021

Canned Sardines

Poland / Baltic Sea

0.011

Cod (fish fingers)

Pacific Ocean

0.006

Mercury concentrations in hair samples of Prague residents

Gender

Age

Heating Type

Fish Consumption/ Meals per week

Smoker

Smoker living in the family

Mercury concentrations (mg/kg)

Female

52

Gas heating

Yes/1-2

No

No

0.217

Female

41

Central heating

Yes/1-3

No

No

0.300

Female

53

Electric heating

Yes

No

Yes

0.102

Female

28

Gas heating

Yes/1-2

No

No

0.250

Female

28

Central heating

Yes/1-2

Yes

No

0.121

Female

27

Central heating

Yes/1-2

No

No

0.507

Female

37

Combined heating

Yes

No

No

0.120

Female

44

Central heating

Yes

No

No

0.287

Female

25

Gas heating

Yes

Yes

No

0.332

Female

24

Gas heating

Yes

No

No

0.146

International activities