Biomonitoring of metals and metalloids with raptors from Portugal and Spain: a review

The analysis of metals in different tissues of raptors has been an important tool for assessing metal pollution. Several studies using a range of sentinel raptor species have been carried out in Portugal and Spain since the 1980s to identify the adverse effects in the animals themselves and on their populations, to identify the contamination of the food chain, to determine the levels of environmental contamination and to estimate human health risks. The aim of this work is to provide synthesized information of the studies carried out in Portugal and Spain in the direct biomonitoring of metals and metalloids using raptors, through a systematic search of the published literature. The information is summarized taking into account specific issues, such as monitored raptor species, sampling periods, monitored areas, type of samples, analytical techniques used in the determination of the metals and metalloids, the analysed metals and metalloids, and overall analysis of the concentrations obtained. There is a striking difference between the number of studies performed in Portugal and Spain, and most of them have been carried out in Spain. The eagle owl, black kite, and common buzzard were the species from which the greatest number of individuals have been analysed. Among the most analyzed biological samples, the blood and liver samples were used to measure the concentrations of all studied metals, while bone was mainly collected to evaluate chronic exposure to lead and feathers to evaluate exposure to mercury during feather growth. Atomic absorption spectrometry has been the most frequently performed technique to determine the majority of metals and arsenic. In general, the concentrations of metals detected in raptor samples from Portugal and Spain are low and insufficient to produce toxic side effects. Only lead, in certain cases, can be related with toxic side effects. However, particular attention should be given to mercury due to its high toxicity, its transport from an aquatic environment to the adjacent terrestrial food web, and because the mercury toxicity threshold has yet to be established for raptors. This work confirms the need for further biomonitoring studies of metals with raptors, especially in Portugal; the establishing of national programs to conduct long-term studies; and creating a network between Portugal and Spain to study environmental contamination using raptors.