This indicator shows the exposure of roe deer to metals (lead (Pb), cadmium (Cd)) and fluorides), indicating the level of air and soil pollution in areas of Slovenia, for which relevant data is available, for various periods between 1925 and 2008.

As a bioindicator species, roe deer is suitable for monitoring air and soil pollution with cadmium, lead and fluorides, as it is exposed to a considerable intake of pollutants from its environment due to its specific feeding habits (herbivorous, selective browser with numerous feeding cycles). In addition, territorial behaviour and a very small area of activity of the species guarantee that individual specimens reflect the quality of a spatially limited habitat.

Due to its specific feeding habits (herbivorous, selective browser with numerous feeding cycles) and sedentary life (very small area of activity), roe deer are exposed to a considerable intake of pollutants from the environment. Consequently, roe deer are a bioindicator species suitable for monitoring air and soil pollution with cadmium, lead and fluorides. Pollutants that enter a roe deer's organism accumulate in its internal organs (cadmium in kidneys and liver, in particular) or bones (lead and fluorides). Some of them cause various histological, anatomical and pathological reactions in certain tissues (e.g. the occurrence of dental fluorosis as a specific indicator of fluoride exposure).

In Slovenia, cadmium is the metal to which roe deer are particularly exposed. Cadmium concentrations in the kidneys and liver reflect the input of this element into the sampled specimen's body during its entire lifespan due to a long-term (several-years) presence of cadmium in the soft tissues of the mammal. Although concentrations of cadmium in the internal organs of roe deer do not reach levels that would directly affect the health of the animals, reproductive potential of individual animals or even sub-populations could be seriously compromised in certain cases. Cadmium concentrations in the kidneys of adult roe deer are high throughout Slovenia. In 1998, cadmium load was highest in the roe deer population of the Pokljuka Plateau (among five studied areas). The highest measured concentration of cadmium in roe deer kidneys in Slovenia was 76.0 mg/kg in the Upper Meža Valley in 1997. Over the recent decade, exposure of roe deer to cadmium has slightly increased (figure ZD08-1).

In contrast, lead concentrations in the internal organs of roe deer were comparable to those in other European countries. Lead concentrations in the liver and kidneys indicate a short-term (several days) exposure to this element, as it tends to be quickly excreted from soft tissues (up to 40 days). In 1998, lead concentrations in the majority of analysed kidney and liver samples throughout Slovenia were below the admissible values determined by law (taking into consideration the suitability for human consumption), while in 2006, none of the analysed samples of internal organs in the Šalek Valley as a selected model area were contaminated with lead (figure ZD08-2).

Due to the properties of roe deer antlers (bone structure), the tendency of lead and fluorides to be permanently deposited in bones and due to the cyclic annual natural growth of antlers, concentrations of lead and fluorides in roe deer antlers reflect exposure of individuals to pollution during the antler growth period within each year, i.e. between November and April. After fluorides have been ingested by roe deer, most are absorbed into the blood (through the stomach and small intestine); after that, fluoride ions (which are extremely negatively charged) bind with calcite ions, which is why 97–99% of absorbed fluorides accumulate in the bone tissues and teeth of the organism, where they cause various pathological changes (e.g. osteofluorosis, dental fluorosis). During antler formation, some of the fluorides that have accumulated in the skeleton are resorbed from the skeleton into the antlers, where they accumulate along with fluoride ions that entered the organism in the same period through food. Similar processes take place in the case of lead.

Since the 1960s, concentrations of lead in roe deer antlers have been showing a steep and continuous decrease in all areas where data is available (Šalek Valley, Postojna Basin, Poljane Valley, Upper Meža Valley), which indicates a decrease in lead contamination of the environment. The combined effect of the introduction of unleaded petrol and the implementation of certain remediation measures at large emission sources contributed to this change (figures ZD08-3 and ZD08-4). An identical trend was determined by analysing roe deer and red deer antlers in other European countries (Germany, Austria, Poland, the Czech Republic, Sweden, United Kingdom). As a rule, contamination of the environment with lead in Slovenia in comparable periods was lower than elsewhere in Europe. An exception is the Upper Meža Valley, where the concentrations of lead in roe deer or red deer antlers in the period of the greatest emissions (1970s, 1980s) were higher than anywhere in Europe measured so far. However, over the recent couple of decades, exposure of roe deer to lead has decreased drastically in this area (figure ZD08-3).

In line with decreasing emissions from large point sources, exposure of roe deer to fluorides has been continuously and noticeably decreasing over the last three decades. In contrast to lead, which is characterised by long-range transmission, fluorides in the environment are of local origin. In the case of the Šalek Valley, concentrations of fluorides in antlers very well reflect the reduction of emissions from the Šoštanj thermal power plant that peaked in the 1980s. Emissions in this area, and consequently the concentrations of fluorides in roe deer antlers, decreased considerably over recent decades and, particularly, after the years of 1995 and 2000 when flue gas scrubbers were installed at the Šoštanj thermal power plant (figure ZD08-5).

A noticeable reduction in roe deer exposure to fluorides has also been confirmed by the decrease in the incidence of dental fluorosis in the recent decade. In the Šalek Valley, its average rate dropped by a whole category in the period 1998–2007, i.e. from moderate to slight. The dental fluorosis rate (DLI: dental lesion index) represents the sum (DLI = 0–30) of visual estimates of change/damage observed in three permanent premolars and three molars (each on the 6-grade scale) of roe deer lower jaws due to exposure to fluorides during the growth and development of teeth, i.e. within the first 18 months of life. Compared to Germany and the Czech Republic, where studying dental fluorosis in roe deer was given the most attention in the past, it was (in general) considerably lower in Slovenia in 2007. The incidence, frequency and intensity of dental fluorosis were very high in the Drava-Ptuj Plain and the Haloze region (i.e. the potential impact area of the Talum aluminium plant in Kidričevo) in 2007 and 2008. Also, dental fluorosis was detected in a significant percentage of jaws in the vicinity of some other local emission sources (the Zasavje region, the Primorska [Littoral] region, the Celje Basin, the Škofja Loka Mountains). Elsewhere in Slovenia, dental fluorosis in roe deer only appears sporadically and is of very low intensity.