Animals—Living and Dead—Can Help Track Humanity’s Toxic Legacy

Natural history museum collections can help backfill environmental pollution data, a new study argues.

In the early 20th century, more than a million miners in Britain made a daily descent into the depths of the Earth to extract coal, the country’s main source of energy at the time. Joining them on their journey to the harsh, dark underground: bright yellow canaries, about the size of a coffee cup. 

These typically loquacious birds were used as a tool. When the canaries fell silent or passed out, miners knew that toxic carbon monoxide was permeating the air and they had to evacuate quickly. The species and this technique gave rise to the phrase “canary in the coal mine”—a refrain used to refer to early indicators of potential hazards. 

A wide body of research shows that a variety of other animals and plants also hold clues for how heavy metals, noxious gases and other toxic substances spread through our environment and what it could mean for human health. 

A new study argues that preserved natural history museum collections are a largely untapped resource for mapping the pollutants of our past, which could inform how they are managed in the present.

Environmental Sentinels: In recent years, engineers have developed high-tech sensors to monitor environmental hazards like gas or heavy metals, but these tools can be expensive to implement at a broad scale. Sometimes the best and most cost-effective way to monitor threats is by testing the species that are immersed in these ecosystems and often live alongside humans, experts say. 

For example, testing fish like gar can help measure toxic metals like mercury and cadmium in the Lower Mississippi River, which pose public health concerns to local communities. 

Meanwhile, research published in 2024 shows the dark toxic burden that house sparrows and children share in lead-mining cities around Australia. Blood samples from hundreds of sparrows captured at more than 40 sites showed high levels of lead in the birds, which live in close proximity with humans. 

With this in mind, the scientists compared their findings to data of blood-lead levels in children in the area and saw a strong correlation. 

The birds and the children with the highest levels of lead in their blood were located in the same areas. The study also showed that blood-lead levels in birds could roughly predict lead exposure in children in different communities. 

Animals could also help us track the history of human-driven climate change. Corals provide a wealth of environmental data for scientists due to their consistent growth and long lifespans. For a 2024 study, researchers took samples from coral skeletons from a reef in the Mediterranean Sea off Spain and tested the marine creatures for spheroidal carbonaceous particles, a pollutant emitted from burning fossil fuels. 

The researchers found that the corals showed a significant increase of contamination between 1969 and 1992, a period of industrialization and high coal consumption in Europe. They say that this provides evidence for the start of the Anthropocene epoch—the modern geological era in which human activities have posed a dominant impact on Earth’s climate and ecosystems. 

“The discovery of these pollutants embedded in coral skeletons extend over decades and paint a clear picture of how extensive human influence is on the environment,” lead author Lucy Roberts, an environmental geochemist at University College London, said in a press release. “​​This is valuable to researchers trying to better understand the history of human impact on the natural world and serves as a powerful reminder of how extensive human influence is over the environment.”

Pollution Time Machine: It’s not just living animals that carry remnants of humanity’s toxic footprint. Samples of bird feathers, fish tissues and other materials hold traces of pollutants that can serve as “environmental archives,” according to a study published in May. 

This strategy could be crucial for filling in data gaps on the historical pollution record, lead author Shane DuBay told me. 

“We really only start monitoring pollutants in the environment once they’re already a problem, so once they’re already having adverse effects on animals [and] on humans, and at that point we really have no understanding … of how we got to where we are,” said DuBay, a biologist at the University of Texas at Arlington. “These specimens that exist in collections around the world have incidentally captured environmental samples from places and times that we can never return to, so we can use them to backfill the environmental record.” 

He added that this approach has already been used to influence public health policy. In the mid-20th century, researchers analyzed a time series of bird eggs from natural history collections to uncover how the insecticide DDT was causing bird eggshells to thin, so much so that they would crack when parents sat to incubate them. 

This finding, featured in scientist Rachel Carson’s famous book “Silent Spring,” contributed to an eventual ban on DDT. The new study argues that this type of data can also reveal a legacy of environmental justice issues in low-income and minority communities, which bear an outsized brunt of pollution in the U.S.

There are limitations to the strategy of tracking toxics through museum collections. Sometimes historical collection data doesn’t include exactly where or when a sample was collected, and the preserved animals may not be evenly distributed across geographic locations. But each bit of data adds a crucial piece to the pollution puzzle, DuBay says. 

“We can put regulations now on how much is being emitted into the environment, but that doesn’t really say anything about what already has been in the environment and will stay in the environment and we will continue to interact with,” DuBay said. “So knowing where that is and which communities, both human and nonhuman, are interacting with those [pollutants] can help us really design a future that mitigates their harm on us.”

Cover photo:  House sparrows are frequently found living near humans—and exposed to many of the same toxic materials in the environment that we are. Credit: Silas Stein/picture alliance via Getty Images