Researchers interested in children’s exposure to heavy metals

14.11.2018 07:54

Risk assessments conducted by the Finnish Food Safety Authority Evira about the exposure of Finnish children to heavy metals and about the combined effects of heavy metals have attracted international interest: results from the multi-year research have recently been published in two scientifically peer-reviewed journals. According to the results, Finnish children get less heavy metals from food than did their parents at the same age. However, as stricter limits have been introduced for the safe intake of cadmium, lead and arsenic after 2008, some children get more heavy metals from food and tap water than what is considered safe according to current knowledge. The combined effects of cadmium, lead, arsenic and mercury have not been studied in other countries.

Finnish Food Safety Authority Evira's risk assessment study about children's heavy metal exposure was based on food intake information collected from Pirkanmaa and on monitoring data on foodstuffs. The study investigated the amount of heavy metals that Finnish children get from food and water. The combined effects of cadmium, lead, arsenic and mercury, which have not been studied earlier elsewhere in the world, were also investigated. According to the study, which was completed in 2015, the exposure of Finnish children to heavy metals was smaller than assessed by the European Food Safety Authority EFSA earlier.

Boys are exposed to heavy metals more than girls

Children today get less heavy metals from food than the previous generation. The lead contents of foodstuffs, for instance, have decreased, thanks to switching over to unleaded petrol, for example. According to the published article, differences in the heavy metal exposure of children aged 3 and 6 years were due to the different eating habits of girls and boys: the boys are exposed to heavy metals more than the girls.

"Finnish boys aged three years got much more cadmium and lead from the food than did the girls, and the same trend was also observed for inorganic arsenic among boys aged six years. This is due to differences between girls and boys in portion size, consumption frequency and the foodstuffs consumed. The heavy metal concentrations measured from foodstuffs in the calculations were the same regardless of gender", says Docent, Ph.D. Johanna Suomi from Evira.

The study focused on five heavy metals or forms of heavy metals: cadmium, lead, inorganic arsenic, inorganic mercury and methylmercury.

Large quantities of cadmium and inorganic mercury are harmful to kidneys. Lead and methylmercury are especially harmful to children's central nervous system, which is not yet fully developed. Of Finnish children aged 3-6 years, as many as over a half get so much cadmium from food that it exceeds the tolerable weekly intake. With the same assessment, the toxicological limit value for lead is exceeded for every seventh child aged 3 years and one per cent of children aged 6 years.

A toxicological limit value has been defined for inorganic arsenic, indicating an one per cent increased risk of specific cancers, as compared with the risk among population not exposed to arsenic. The European Food Safety Authority EFSA uses a broad value range in determining toxicological limit values for inorganic arsenic. In Finland, inorganic arsenic intake exceeds the lower limit of EFSA's value range among 43 per cent of children aged under 3 years and 29 per cent of children aged 6 years.

"In contrast, the limit value defined by the joint expert body of the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organisation (WHO) was not exceeded for any of the children participating in Evira's study. The tolerable weekly intake limit for methylmercury defined by EFSA was only exceeded for a couple of per cent of the children, while the intake of inorganic mercury was at a safe level among all the children studied", says Suomi.

Everyday food the primary source of heavy metals

Foodstuffs consumed in large quantities were the primary source of heavy metals even though the concentrations in them are not particularly high.

According to the study, cereal products and rice were the main sources of inorganic arsenic. In addition, one third of total exposure to cadmium and lead was from cereal products, and several other sources were also identified for them.

Vegetables in particular were major sources of inorganic mercury. Juices on whose concentrations domestic information was not available were sources of inorganic mercury according to concentration data collected from the EU area. Methylmercury was mainly found in fish and other seafood.

Combined effects of heavy metals have not been studied elsewhere

According to Evira's study, the heavy metals affecting kidney damage risk among Finnish children under school age are cadmium and lead.

Of the various heavy metals, lead has the most powerful impact on the central nervous system of the mixture of heavy metals in food. Children get more lead than mercury from food, and the effective dose of lead is approximately a half smaller than that of methylmercury.

"By developing production practices and further lowering the lead concentrations of different foodstuff groups from the present level, the population can be protected more efficiently against central nervous system damage than by limiting the amount of mercury in food", says Suomi.

Careful assumptions have been used in combining information on the toxicity of different heavy metals, because the experimental designs on which they are based have not been mutually fully comparable. The combined effects of cadmium, lead, arsenic and mercury have not been studied earlier elsewhere in the world.

"This is a good start that can be complemented when the effects of heavy metals have been studied globally using the same experimental designs and observing the same factor", Suomi says.

The research results of the exposure of Finnish children to heavy metals have been published in a scientifically peer-reviewed journal:
Suomi, J., Tuominen, P., Niinistö, S., Virtanen, S.M., Savela, K.
Dietary heavy metal exposure of Finnish children of 3 to 6 years. Food Additives and Contaminants Part A 2018: Vol 35, No. 7, pp. 1305 - 1315. 

A study of the combined effects of heavy metals has been published in a scientifically peer-reviewed journal:
Suomi, J., Tuominen, P., Savela, K.
Dietary exposure of Finnish children to heavy metal mixture – a cumulative assessment. Human and Ecological Risk Assessment: An International Journal 2017: Vol. 23, No.5, pp. 1234 - 1248. 

Further information in Evira publication (description in English)

Risk assessment of the exposure of Finnish children to heavy metals in foodstuffs and tap water 

For further information, please contact:
Senior Researcher Johanna Suomi, Risk Assessment Research Unit, tel. +358 40 822 5629

The Finnish Food Safety Authority, the Finnish Agency for Rural Affairs and a part of the National Land Survey of Finland's Centre for ICT Services become the Finnish Food Authority on 1 January 2019.

 

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