Sparrows with elevated lead levels sentinels of environmental and human health

Fleur Connick: You may have read the recent ABC article on how the house sparrow could help sound the alarm on lead poisoning in kids. An Australian study found the small brown birds accurately predicted the likely incidence of lead poisoning in nearby children in two regional towns impacted by lead mining. Today we’ll be speaking to one of the study’s authors, Simon Griffith, who is an evolutionary biologist and professor at Macquarie University’s School of Natural Sciences. Not only are sparrows useful sentinels for monitoring environmental and human health, Simon and his team have also discovered genetic hints which suggest that the sparrows may have started adapting to become less sensitive to the toxic effects of lead.

Simon Griffith: So, many people are familiar with sparrows. A lot of people in Australia particularly think sparrows are these nasty invasive species, but sparrows aren’t really impacting any of our native wildlife. I grew up in Southeast London, and sparrows were very abundant, they used to nest under the eaves of our house. I was interested in birds and other animals from a very early age, and I’ve been very fortunate in managing to follow that kind of interest throughout my career. I’m an evolutionary biologist, and there’s a number of interesting questions about how they’ve actually adapted to the Australian landscape.

Fleur Connick: So what makes the house sparrow unique and, I guess, a useful species in terms of monitoring environmental pollution and also identifying when there could be potential risks to human health?

Simon Griffith: So one of the key things about sparrows is for around 10,000 years they’ve actually adapted to live really closely alongside people. In fact they’re almost completely dependent on people. In Australia they only live in urban areas, they don’t live out in the bush, and that’s because they eat food which they get from us, it’s either food that we’re actually feeding them, or food that they can scavenge like crumbs in cafes and things like that. So it’s that intimate connection that they have with people which means they can tell us something about the state of the environment in which they’re living, which is of course the environment in which we live ourselves. 

One of the things that is useful from a practical point of view is that they do live in people’s gardens. They have these small home ranges. So if we go into someone’s garden and catch the birds that are in that garden, a sparrow has a home range of around about 300 metres. So we know that that bird has essentially been living in all of the gardens within about 300 metres of that property. So, for example, in Broken Hill we’ve been able to target birds at 45 different locations across the city, which is a really good way of capturing the variation in the environment. And so over the course of a few years we sampled well over 1,000 birds, which helped us characterise those levels of contamination across the environment.

Fleur Connick: What did you find? What were the blood levels of these sparrows in Broken Hill?

Simon Griffith: All of the birds that we captured and sampled, these were all birds that were flying around, they were apparently healthy birds. We put bands on them, and many of them we saw over subsequent years. So they’re all birds that were effectively healthy, but they had really, really high levels of lead, obviously particularly in the most contaminated parts of town. 

Fleur Connick: I think it’s really fascinating. A lot of people might not think about that, even though these birds have really high lead levels, those signs of lead poisoning in birds aren’t as obvious. And I understand with children, the initial signs of lead poisoning can be quite subtle, or they might not have any signs at all. And that’s what I was going to ask you, is it the same in birds basically, are those signs quite subtle? 

Simon Griffith: Yeah, that’s absolutely right. It doesn’t mean that…because those birds were flying around apparently normally, it doesn’t mean that they’re not being damaged. So again, globally in humans it’s been estimated that lead poisoning is killing almost a million people a year around the world, and it will have effects right across your physiology. So it will actually lead to things like elevated heart disease, elevated levels of anaemia. So it means that you don’t necessarily get really chronically sick, but it’s essentially kind of wearing you out physiologically. It will take years off your life. 

This is a really good indication of how birds that are in our urban environment, like sparrows, they can actually serve a purpose. They can tell us something about the state of that environment, and that is the environment, of course, we should care about and try and make that as healthy as we can, not just for the animals that share that environment, but obviously more importantly for the people that are living in it. So this is one of the first studies in Australia where we’ve looked at the level of contamination in a bird. That’s really just scratching the tip of the iceberg, given how important and widespread the mining industry is, and the sources of contamination for wildlife, that’s certainly something that would be worthy of follow-up. 

Fleur Connick: Some people might say testing or measuring lead in the environment, that you can test the soil or you can test the water. What’s different about understanding that exposure in people, how much lead is actually getting into people and kids?

Simon Griffith: We can go out there and we can dig the soil up and find out how much lead is actually in the soil, but that doesn’t represent the risk to people potentially of that lead, and that’s because some of that lead might be buried in the soil and it might not actually be available to animals. And of course we’re animals in that sense. So the idea of actually using a sparrow is that they’re an animal that’s living in the environment, they’re moving around, they’re breathing in, they’re eating food that potentially has been contaminated with lead. And so the pathway to exposure of a sparrow is actually very similar to the pathway of exposure to people. And so particularly with little kids that are very sensitive to the toxic effects of lead, a lot of those pathways, kids going outside and playing, picking up lead particles in the dust that they’re playing in, and ingesting it with their food or snacks that they’re eating, also breathing it in on dusty days. So the sparrows are actually really giving us a good idea of the risk to an animal. There will be environments where the lead might be present in the soil, but it might not be as available to animals and people.

Fleur Connick: In the study you often refer to the sparrows as sentinels, and there’s other wildlife sentinels, but would you mind just explaining what you mean by that in the purpose of this study, and more broadly as well?

Simon Griffith: Your listeners are probably familiar with the idea of the canary in the coal mine, and that was used back in the 1800s as kind of a sentinel. So, miners would take a canary in a cage down into the coal mine. They would keep an eye on the canary as they were working. If the levels of carbon monoxide or carbon dioxide got too high, the canary was a little bit more sensitive than the people, and so it worked really well as a sentinel to tell them that the environment in which they were working was becoming too toxic, and then they would quickly get out of that area. So the sparrows, in this sense, are acting as sentinels in exactly the same way. 

We can go into those urban landscapes, and if there’s something wrong with those birds, if they’ve got high levels of contaminants that we can detect in their blood or if we find that there are birds that are sick in urban environments, that’s telling us something about that environment has some level of toxicity that’s affecting animals. If it’s affecting animals, we’re not immune to it, we’re animals ourselves, we’re breathing, we have the same roots of contamination as things like sparrows. So in that sense we’ve kind of taken the canary out of the mine and we’re actually using these sparrows as a sentinel for our environments. 

The other thing that we can learn from these animal studies is that we can actually try and further investigate the effects of these contaminants on animals. And things like sparrows, they have a very short life history, so they only live for three or four years, obviously compared to humans that’s very short, and that means that the damage that these contaminants are doing can be seen much more quickly.

Fleur Connick: You spoke earlier about how sparrows are one of those species that have easily adapted alongside humans, and when it comes to environmental pollution and the impact we can have on the environment, how have the sparrows in those towns that you looked at, how have they changed over time? Was there anything you noticed there in terms of comparing them to other sparrows in areas that might not be affected by lead mining, for example?

Simon Griffith: Yeah, that is one that we’re certainly working on further at the moment. We have levels of blood lead in these particular sparrows that are very, very high on a kind of international level in terms of other birds. Now, partly that might be because sparrows actually have something in their physiology that has made them a little bit more resilient. So, because they’ve been associated with humans for 10,000 years, and lead has been something that humans have been mining and using in manufacture and industry for many thousands of years, it means that sparrows have potentially had the capacity to adapt to lead poisoning over thousands of generations, and, in an evolutionary sense, that could well be enough time for them to actually somehow reduce the damaging effects of lead on their physiology. So that’s an intriguing question.

We have compared the genetics of the birds from Broken Hill and Mount Isa with another 15 populations in other towns that were similarly situated out in the arid zone or remote from big cities that don’t have background levels of lead contamination that are as high. And what we found were there were 12 genes, basically, that were different in Mount Isa and Broken Hill compared to those other populations. And about nine of those genes, through genome work in other organisms, had been associated, in some cases, with lead poisoning in things like worms and rats, but also with other things like metal transport through cells. So there is a kind of hint that the birds in these mining towns (and they’ve been there for over 100 generations), they may have actually started adapting, which is super cool, because that shows just how fast evolutionary responses can be. So we’re following that up at the moment, we’re doing some whole-genome work, which is a much better way of looking at that genetic adaptation. 

And we’re also comparing the ability of birds in these towns or Broken Hill with other towns where they haven’t got that history of potential adaptation to see how resilient they actually are. It will be super cool if we can show how fast evolution is. So in one sense, as an evolutionary biologist I find it fascinating that they may have changed, and they may have actually started adapting to become less sensitive to the toxic effects of lead. So that’s really cool. I guess the thing that isn’t so cool is it just shows the kind of really nasty effects that humans are having on their environment, if we’re actually changing, modifying organisms in that way. 

Robyn Williams: And Professor Simon Griffith at Macquarie University is also looking for hot spots in cities to see how much lead (left over from when it was in paint and petrol) still lingers in hot spots. That report from Fleur Connick.