Study uses great tits to measure air pollution

Czech researchers captured dozens of free-living birds to map the extent of heavy metal contamination in various regions around the country.

Great tit, photo: © Francis C. Franklin / CC-BY-SA-3.0Great tit, photo: © Francis C. Franklin / CC-BY-SA-3.0 Czech scientists have captured around sixty great tits all around the country to measure the level of heavy metals in their bodies and their impact on the birds’ health. At the same time, they used the birds to map the extent of heavy metal contamination in various regions around the country. The results of the study were published in a prestigious international magazine called Science of the Total Environment.

I met with one of the authors, zoologist Michal Vinkler, to find out more about the study:

“The main goal of the study was to find association between the contamination with heavy metals in the free-living birds, in our case the great tits, and the state of their health. In other words, the traits in the birds that indicate their condition and health.”

Why did you choose birds as an indicator of air pollution? Is this a common method?

“The method is not really common. It has been proposed about 30 years ago and now and then there are attempts in the research to apply birds as bio-indicator of heavy metal contamination.

“The reason for this is that birds are situated pretty high in the food chain and during their life they accumulate heavy metals. These heavy metals, when you study them for instance in blood or feathers, can tell us something about the environment in which the birds are living.”

Why did you choose the great tit in particular?

“Great tit is a very common European passerine. You can find them basically in every park and forest which is very convenient for similar studies because wherever you go, you can sample.

“The other aspect is that great tit is a model species of evolutionary biology as well as ecological research, meaning that we have very extensive knowledge about various aspects of biology of this particular species.

Michal Vinkler, photo: archive of Michal VinklerMichal Vinkler, photo: archive of Michal Vinkler “We are aware of the food chain links, we are aware of the birds’ genetics. The great tit is actually one of the species with annotated genome. So whatever we do with great tits, we can find very strong support with other findings by other researchers.”

How extensive was this research?

“This research was something like a sub-project of a different study, which focused on slightly different questions, but we decided to use the material we collected to answer some environmental questions.

“The whole field-work took us about one month, which was very convenient, because what you typically need in the research is to accumulate as much data in the shortest possible time. We went through cities in the Czech Republic which differ in the level of air pollution with dust particles.

“It is known that these particles are coated with heavy metals, so we had the dust contamination of the air as a proxy trait to heavy metal contamination in the environment.”

“So we went through the cities to collect five individuals, in total it made 57 birds, where we had the profile of heavy metal contamination.”

So what kind of metals did you focus on?

“These heavy metals were arsenic, copper, cadmium, lead and chrome. Some of them naturally occur in the environment and some of them are even essential, such as cooper or chromium, and then there are some toxic heavy metals like arsenic for instance or cadmium or eve lead.

“But the main question was to find out if what we see in the birds really affects them. Typically if you go outside and sample heavy metals in the air or in the soil, it doesn’t tell you so much about the effect of the contamination of the environment on the living creatures.”

What were the main findings and did you find them surprising?

“They were quite surprising in several aspects. First of all we really found out the association between a heavy metal contamination in animals and their health, which was quite surprising.

“We didn’t expect that if you do research on such a large territory that it will actually tell you so much about the effect of contamination on health.

Photo: Alena PalečkováPhoto: Alena Palečková “However, we really found the highest contamination of blood with heavy metals in the region where we have the highest contamination of environment with dust particles, and that is Bohumín.”

“And this then was linked to the production of blood cells in bone marrow of the birds. So in these birds we found decreased total numbers of red blood cells.

"And the other surprising thing was that it appears that in the Czech Republic there is slightly increased contamination with some heavy metals and most cities are equal in this contamination.”

So you haven’t found any significant regional differences?

“Across most cities not, with the exception of Bohumín region, where the contamination was higher.”

As you said, you found out that heavy metals really have an impact on birds’ health. Does it mean they affect human health in a similar way?

“This is an interesting question and the short answer is: we don’t know yet. In the future we would be very glad to make a direct link between animal health, in our case bird health, and human health.

“The trouble is that humans, although they share the environment with free living animals, have for instance a very different diet. In the diet of humans you have product that were used at very distant places, so people accumulate heavy metals in slightly different rates.

“The thing we don’t know is if air pollution with heavy metals has the most important effect on the their accumulation in humans or if food sources are of more importance.”

What is also surprising is the fact that Europe actually has pretty strict air pollution regulations but despite that there is a significant pollution with heavy metals.

“Yes, indeed. With heavy metals the situation is slightly worse than with dust particles per se, because heavy metals are non-degradable. So you cannot really get rid of them. What happens is that they slowly deposit into soil.

“If they are in the soil, they are up-taken by plants and then through these plants they enter the food chain of animals. The thing you can do is to use particular plants to accumulate heavy metals.

“You then deposit the biomass in certain areas and not to allow these heavy metals to enter the food chain, for instance. But otherwise it is pretty difficult to get rid of heavy metals.”

Photo: Filip JandourekPhoto: Filip Jandourek Do you actually plan to continue with your study in the future and if so, would you like to widen the scope across the whole of Europe?

“Yes, we would be very glad to continue. What we would like to do at this moment is to make some kind of a map of heavy metal contamination in great tits both in the Czech Republic and Europe.

“Last week I was at a conference of European Evolutionary Biology Society and I met a couple of people who study great tits and they were all very keen to collaborate with us and provide us with samples.

“So the nice thing about further research is that we can basically use the genetic material, meaning blood, that was already collected for the purpose of other studies and use it to investigate the heavy metal contamination.

“The plan emerging for the Czech Republic is a directed aimed collection of samples in as many sites as possible. However, for this research we will need to find some financial support.”