Ludwig De Temmerman

Transfer of soil contaminants to home-produced eggs and preventive measures to reduce contamination

Uptake studies have shown that chickens foraging on soils contaminated with environmental pollutants accumulate these compounds into their eggs. Home-produced eggs thereby show higher contamination levels than commercially produced eggs. It was the aim of this study to identify the major source of two environmental pollutants in home-produced eggs, i.e. dioxins and lead, to formulate preventive measures to reduce the contamination levels of such eggs, and to assess the feasibility of the formulated measures in terms of the perception and behavior of private egg producers towards such measures. The major source of dioxins and lead in eggs, i.e. the soil, was identified by transfer calculations of the pollutants from the feed and soil towards eggs. Preventive measures to reduce soil intake or geophagy and hence egg contamination levels, were formulated and their feasibility evaluated through interviews with private chicken owners. The results show that a paved surface inside the henhouse, an indoor feeding place and providing a sufficient surface area per chicken were considered the most appropriate in terms of feasibility and willingness to apply the measures by the private chicken owners. To enhance the effect of the measures, a combination of measures supported and promoted at policy level is considered as a good strategy to reduce contamination levels in home-produced eggs.

Selenium content of Belgian cultivated soils and its uptake by field crops and vegetables

A series of 695 food crops were collected on 539 soils throughout Belgium. All samples were collected on commercial production fields, omitting private gardens. All crops were analyzed for their selenium (Se) concentration. The soils represent different soil types occurring in Belgium, with soil textures ranging from sand to silt loam, and including a few clay soils. They were analyzed for Se concentration, organic carbon content, cation exchange capacity and extractable sulphur (S) concentration. The Se concentrations in the soils were low (range 0.14-0.70 mg kg(-1) dw), but increasing soil Se concentrations were observed with increasing clay content. Stepwise multiple regressions were applied to determine relations between Se concentrations in crops and soil characteristics. Among field crops, wheat is the most important accumulator of selenium but the concentration remains rather low on the Belgian low Se-soils. Based on dry weight, leafy vegetables contain more Se than wheat. The soil is the most important source of Se and the element is transported with the water stream to the leaves, where it is accumulated. Vegetables rich in S, e.g. some Brassica and Allium species, have a higher capacity to accumulate Se as it can replace S in the proteins, although this accumulation is still limited at low soil Se concentrations. In loamy soils, weak correlations were found between the soil Se concentration and its concentration in wheat and potato. The uptake of Se increased with increasing pH. The Se concentrations in Belgian soils are far too low to generate a driving force on Se uptake. General climatic conditions such as temperature, air humidity and soil moisture are also important for the transfer of Se within the plant, and plant linked factors such as cultivar, growth stage and edible part are important as well, although their influence remains limited at low soil Se concentrations.

Trace elements in home-produced eggs in Belgium: levels and spatiotemporal distribution.

The purpose of this study was to evaluate the levels of arsenic, cadmium, lead, copper and zinc in home-produced eggs, soils and kitchen waste samples of private chicken owners in Belgium, and to determine spatiotemporal differences in trace element contents in eggs. Eggs were sampled in all provinces of Belgium in autumn 2006 and spring 2007. A total number of 59 private chicken owners participated in the study. Trace elements were determined by inductively coupled plasma-mass spectrometry except for mercury, which was determined by atomic absorption of mercury vapour. The mean fresh weight concentrations in eggs in autumn and spring respectively were <8.0 and <8.0 microg/kg for arsenic, 0.5 and <0.5 microg/kg for cadmium, 116 and 74 microg/kg for lead, 0.43 and 0.52 mg/kg for copper, 20.3 and 19.2 mg/kg for zinc, and 3.15 and 4.44 microg/kg for mercury. Analysis of variance determined significant differences in some trace element concentrations in eggs among seasons and regions in Belgium. Average concentrations of arsenic, cadmium and mercury corresponded well with values measured in other countries, while copper and zinc concentrations were within the same order of magnitude as in other countries. Average lead concentrations were high compared to concentrations in eggs from other countries and correlated well with lead concentrations in soil, indicating that the soil is an important source. Other sources of trace elements in eggs might be home-grown vegetables and forage (grass and herbs), and indirectly, air pollution.

Impact of atmospheric deposition of As, Cd and Pb on their concentration in carrot and celeriac.

Root crops, carrot and celeriac, were exposed to atmospheric deposition in a polluted versus reference area. An effect was observed on the As, Cd and Pb concentrations of the leaves and the storage organs. The concentrations in the whole storage organs correlated well with atmospheric deposition, which shows that they even could be used for biomonitoring. Nevertheless, leaves remain much more appropriate. The results revealed also a significant increase of the As and Cd concentration in the consumable part of the storage organs as a function of their atmospheric deposition. As such the experiments allowed deriving regression equations, useful for modeling the atmospheric impact of trace elements on the edible parts of root crops. For Pb, however, there was hardly any significant impact on the inner parts of the storage organs and as such the transfer of Pb in the food chain through root crops can be considered to be negligible.

Predicted dietary intake of selenium by the general adult population in Belgium

The total selenium content of about 800 food products purchased in Belgium was determined and combined with food records to determine the nutritional selenium status of Belgian people. The largest selenium concentrations (>1 mg kg−1) were found in Brazil nuts and offal, of which the consumption is limited. Usually consumed food groups with the highest selenium concentrations were fish and shellfish (0.2–0.9 mg kg−1), eggs, poultry meat, cheese, mushrooms and pasta (approximately 0.2 mg kg−1). The mean dietary selenium intake was calculated to be 60 µg day−1, which is at the lower end but within the range recommended by the Superior Health Council in Belgium (60–70 µg day−1), and adequate according to the 55 µg day−1 recommended by the Scientific Committee on Food (SCF) of the European Commission. The major sources of selenium intake are meat and meat products (31%), fish and shellfish (20%), pasta and rice (12%), and bread and breakfast cereals (11%).

A dynamic model to calculate cadmium concentrations in bovine tissues from basic soil characteristics

A chain model was developed to calculate the flow of cadmium from soil, drinking water and feed towards bovine tissues. The data used for model development were tissue Cd concentrations of 57 bovines and Cd concentrations in soil, feed and drinking water, sampled at the farms were the bovines were reared. Validation of the model occurred with a second set of measured tissue Cd concentrations of 93 bovines of which age and farm location were known. The exposure part of the chain model consists of two parts: (1) a soil-plant transfer model, deriving cadmium concentrations in feed from basic soil characteristics (pH and organic matter content) and soil Cd concentrations, and (2) bovine intake calculations, based on typical feed and water consumption patterns for cattle and Cd concentrations in feed and drinking water. The output of the exposure model is an animal-specific average daily Cd intake, which is then taken forward to a kinetic uptake model in which time-dependent Cd concentrations in bovine tissues are calculated. The chain model was able to account for 65%, 42% and 32% of the variation in observed kidney, liver and meat Cd concentrations in the validation study.