Why should a medical student be interested in conservation?
According to a growing body of evidence, including a recent study co-authored by William & Mary biologist John Swaddle, the seemingly distinct fields of health science and conservation are inextricably linked.
The new study, published in the journal Environmental science and technology, Lead levels measured in blood of house sparrows (Passer domesticus) in Australian mining towns to accurately predict blood lead levels in children living in the same areas.
“This shows that wildlife and human health are so intimately linked that when something like lead, which we know is a toxin, gets into the environment and affects wildlife, it also affects humans,” said Swaddle, professor of biology and faculty director of the William & Mary Institute for Integrative Conservation (IIC).
The study illustrates the growing relevance of the “One Health” concept, which brings together aspects of public health, veterinary health and conservation.
Several One Health student projects are already underway at the IIC, which plans to work with curatorial partners to expand their availability in the future. The One Health opportunities will provide additional research avenues for students in W&M’s popular pre-med and kinesiology programs.
“Many W&M students are interested in health sciences or health practices. We want to show them that studying the environment and conservation is very important to public health and human health.”
John Swaddle
“It’s an effective approach,” Swaddle said, “because we know that the same living things inhabiting the same area will be exposed to the same risks. Whether those risks come from a toxin like lead or a pathogen, researchers can use wildlife as sentinels to detect human disease.”
It demonstrated the role of One Health in opening up an interest in conservation to a whole new group of people.
“A lot of W&M students are interested in health sciences or health practices,” he said. “We want to show them that studying the environment and conservation is very important to public health and human health.”
Swaddle explained that biodiversity conservation aligned with human well-being is the core business of the IIC.
“The Institute promotes and, through partnerships, implements conservation solutions that promote the well-being of ecosystems and the diverse species that live in them,” he said. “At the same time, it promotes equitable social and sustainable practices that improve human health and well-being,” he added.
The relationship between lead mining, house sparrows and children
For centuries, industrial activities have released significant amounts of lead and other heavy metals into the environment around the world, including the United States.
Swaddle explained that there is a growing awareness of the inextricable links between humans and nature and a deeper recognition of the essential ecosystem services that healthy ecosystems provide.
“This awareness is critically important because humans need these services to survive as a species and to thrive as communities,” he said.
According to the World Health Organization, children are particularly vulnerable to the effects of lead exposure, with health consequences that can last into adulthood. Finding ways to identify areas of the world where children are at high risk of lead contamination allows health officials to determine appropriate measures to address and prevent this problem.
Throughout history, animal sentinels have detected dangerous conditions. For example, canaries were carried into mines as early as 1896 to warn coal miners of the presence of carbon monoxide. Sentinel species that have alerted humans to environmental hazards range from lichens to mammals to crustaceans.
Swaddle, for his part, has studied the effects of heavy metal contamination on birds. In the locations examined in his most recent paper, significant amounts of lead were released into the environment during the mining, processing and transportation of lead ore.
Choosing an appropriate sentinel species for research requires careful consideration.
“You don’t want a species that’s moving around everywhere, because otherwise its lead load could be miles and miles away,” Swaddle said.
House sparrows were identified as ideal for this research because they are non-migratory, stay in localized territories and live in close proximity to humans. Swaddle added that they also feed on the ground and frequently dust bathe, making their exposure to lead in soil similar to that of children crawling or playing on the ground.
“The lead that you can detect in the blood of a house sparrow in a particular location will be associated with that particular location,” Swaddle said. “So that can give you an idea of how people who live within that small radius will be exposed to that type and amount of lead.”
The researchers, led by PhD student Max Gillings and Professor Simon Griffith from Macquarie University in Sydney, began their study in Broken Hill, New South Wales, where they collected blood samples from sparrows captured at sites across the city. They then compared the lead levels in these samples to data from a 30-year children’s blood lead monitoring program, and found a strong relationship between the two datasets across all sites sampled. For example, levels in sparrows and children were higher near mining sites and declined similarly as distance from the mining sites increased.
The researchers then took blood samples from sparrows in Mount Isa, Queensland, a place with similar levels of lead contamination to Broken Hill. This time, they used the patterns discovered in Broken Hill to successfully predict blood lead levels in Mount Isa, later confirmed by data from the Child Blood Lead Monitoring Program.
“So it’s not just about looking at a specific area and saying, ‘Oh, look, there’s a correlation between the two,'” he said. “It’s actually using it as an indicator of childhood exposure.”
The authors point out that these types of studies could help determine the effectiveness of measures used to reduce lead exposure in children. For example, the correlation between lead levels in sparrows and in children was stronger when compared to data from 1991, the first year of the childhood blood lead monitoring program.
At that time, annual mining rates and children’s blood lead levels were at their highest, the authors explain. Subsequent efforts to reduce children’s exposure to lead may have contributed to the less strong correlation between sparrows’ and children’s blood lead levels in recent years.
Swaddle explained that the research results show the strength of the bonds between humans and wildlife.
“This study helps show people that humans are part of nature, not separate from it,” Swaddle said. “We are intimately connected.”
Laura Grove, Research Editor
