Experts have warned that more needs to be done to understand the extent of harmful lead exposure in wild mammals after a study revealed how widespread it is among species across the planet.
Wildlife population health experts at Nottingham Trent University analysed almost 200 previous studies spanning more than 60 years and 35 countries to better understand the scale of the problem.
Although more is known about the extent of lead exposure in birds – where the first poisonings were recognised almost 150 years ago – this was the first review to focus on wild mammals.
According to the findings, there was lead in all 153 mammal species previously studied, with the most-researched species being red deer, European roe deer, wild boar, the wood mouse and brown bear.
Other species with lead poisoning included ringed seal, beluga whale, common wombat, European hare, Tasmanian devil, American manatee and stump-tailed macaque.
Dr Helle Hydeskov, a scientist in Nottingham Trent University’s school of animal, rural and environmental sciences, said: “Lead exposure in wild mammals is an extremely serious issue.
“It is clear that this is occurring in many species, across many countries and over many years.
“Little is known about lead exposure and its health effects on mammals, so more research is urgently needed.
“We need to better understand the impact on carnivores and scavengers.
“These animals are important for monitoring ecosystem health as lead accumulates in the body, and so it makes sense to study animals that eat other animals and that live for a longer period of time.
“More focus also needs to be put on countries expected to have the highest lead pollution, as well as developing countries with no or few regulations on lead.
“Helping to determine the impacts of lead on different species will add to our knowledge of this toxic metal and provide us with the necessary evidence to help with vital regulation.”
Experts suggest the sources of environmental lead are varied and depend on the geographical context as different countries permit or ban different products containing the metal.
For herbivores, the ingestion of lead is likely to happen via water or consumption of plants grown on soils containing the metal.
For carnivores and scavengers, it is likely they also potentially drink contaminated water or eat contaminated plants, but also consume meat from animals that might have ingested lead via water or vegetation, or their prey has been hunted using ammunition containing lead.
All of the studies looked at by the researchers reported lead concentrations in wild mammals, but only a quarter investigated its health effects.
However, the health effects were always negative and ranged from minor to fatal, and were found to have affected the nervous, circulatory and reproductive systems, the kidney, liver and teeth.
Lead is a toxic, non-essential metal that occurs naturally in the Earth’s crust and has historically been used in many products, including water pipes, paints, petrol, ammunition, aviation fuel, motor vehicle batteries, glassware and cosmetics.
It is believed these human activities have increased the amount of environmental lead to around 1,000 times the natural levels, thereby increasing the exposure and risk to wildlife.
Despite legislation banning or reducing the use of lead, it is still present in many products, including ammunition used to hunt game species.
The researchers hope further study of this area will create stronger evidence to influence policymakers involved in the regulation of products which contain lead.
The findings are published in the Journal of Wildlife Diseases.