A Scientist's Life: Tarik Benmarhnia

Climate change epidemiologist considers human health hazards

Tarik Benmarhnia is a climate change epidemiologist with a joint appointment at the University of California San Diego’s Scripps institution of Oceanography and School of Medicine. He finished his PhD jointly from the University of Montreal and Paris Sud and finished two master’s degrees, one in environmental health sciences engineering from the French School of Higher Education in Public Health and another in pharmacy and ecotoxicology from Montpellier University in France. He completed his bachelor of arts in environmental sciences from Montpellier University.

explorations now: What do you do for a living?

Tarik Benmarhnia: Most of my work is dedicated to understanding the relationship between climate change and population health, with a focus on vulnerable populations. I try to understand to what extent air pollution, heat waves, and some vector-borne diseases affect population health, to what extent some specific populations and communities are more affected, and what we can do in terms of policies to address that.

en: What are some of the major questions in your field?

TB: Today I would say the most important question is to understand how climate change is going to affect specific environmental hazards, such as heat waves, to try to understand how they're going to affect population health and how we can adapt today to try to address these issues and try to minimize what would be the health burden related to future heat waves that will happen in the context of climate change.

Another important challenge is to try to understand how we could mix different mitigation policies with beneficial health implications. For example, because climate change is caused by anthropogenic greenhouse gas emissions, we can try to reduce these emissions and at the same time to maximize the health benefits associated with mitigation policies. For example, encouraging vegetarian practices or active transportation can have a lot of implications both on health and on reducing greenhouse gas emissions. I think these kinds of links are very important.

en: What are some of the specific health hazards you’re investigating now?

TB: Right now, we are working on a research project in California, with a specific focus in San Diego, to study droughts in the context of climate change. Climate change will exacerbate drought so we are trying to understand how that could affect population health through different mechanisms. For example, we are interested in how drought is going to cause wildfires, and how wildfire through smoke is going to affect population health. We are also trying to understand how drought in association with extreme precipitation is going to increase water and sanitation problems in the coastal zones for swimmers and beachgoers. We are also trying to understand to what extent drought is going to change the spatial distribution of vectors for certain infectious diseases. Vectors are animals such as mosquitoes that can transmit specific diseases so all of these diseases that can be transmitted by mosquitoes or other animals are called vector-borne diseases (the most famous examples are malaria, Zika and Dengue). One of the most important vector-borne diseases in California is West Nile virus. So in this project, working with colleagues from UCLA, UC Berkeley and UC Merced, we are trying to understand to what extent climate change is going to affect droughts and extreme precipitation, and how this is going to influence the spatial distribution of vectors and the probability of vector-borne diseases in California.

en: What tools do you use for your research?

TB: As I am an epidemiologist, most of my tools are statistical. For example, I use a lot of statistical methods and try to apply these methods by connecting some existing data from electronic medical records that I then try to mix with air pollution measures or satellite images to reconstitute a kind of cohort, and try to see what would be the link between being exposed to specific air pollutants, and what health effects could be directly linked to this exposure.

One of the methods and approaches I use to evaluate environmental policy and its health implications is to rely on the notion of natural experiment. Because we can't conduct a classical experiment in which we're going to expose one group and make another group the control group, we try to find some natural variations. For example, we try to look at a recent volcanic eruption or earthquake to see to what extent it's going to increase exposure to something like unsanitary water, and we use this natural experiment to evaluate to what extent it's going to potentially affect population health.

An experiment could also be related to economic crisis. If you take Cleveland, for example, there was a huge iron industry there for many years; but during the Great Recession a few years ago, a lot of industrial facilities were shut down. It has been a very interesting natural experiment to evaluate the specific health impact of iron on population health. Because nothing else happened except closure of the facilities, we’re performing research now to see if we can distinguish the specific impact of iron particles contained in air pollution on people, for example.

en: Why did you come to Scripps?

TB: I came to UC San Diego through a joint appointment between the faculty of medicine and Scripps. This is a very interesting position because as an epidemiologist, my natural work environment would be mostly in medicine but because all of my interests are related to environmental futures and the context of climate change, it’s very interesting to be here, to collaborate with climatologists and meteorologists to use advanced climate modeling approaches mixed with advanced epidemiological modeling. So I see this as a very nice collaboration and situation to take the best of both worlds to address the same question.

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