Heat Waves and Pollution

Heat Waves and Pollution Photo credit: Clipart.com

Heat waves and poor air quality go hand and hand.


Heat waves and pollution. I’m Bob Hirshon and this is Science Update.

In the summer of 2006, hundreds died as temperatures reached the 120’s as far north as South Dakota. Princeton atmospheric scientist Jordan Schnell says heat waves kill partly because they co-occur with pollution, chiefly ground-level ozone and particulates.

And what happens is we don’t have a whole lot of winds at the surface, we don’t have any rain to clear anything out, so basically nothing’s being diluted and it just builds up over the course of the multiple days.

In the Proceedings of the National Academy of Sciences, Schnell reports on research done while at UC Irvine studying 15 years of heat waves and modeling how the heat and pollution spread and persist. The work will help provide early warnings of life-threatening events and predict the longer term effects of climate change. I’m Bob Hirshon for AAAS, the science society.

Making Sense of the Research

Heat-related deaths are a cause for concern in many countries, especially among vulnerable populations, like older adults and young children. According to the Centers for Disease Control, there were a total of 7,233 heat-related deaths in the U.S. between the years of 1999 and 2009. In that time, an average of 658 people died of heat-related causes in the U.S. each year. Worldwide, nine of the top 10 heat waves with the most fatalities have occurred since 2000, according to data in EM-DAT, an international disaster database. These nine heat waves caused 128,885 deaths around the world.

What happens, though, when a heat wave is combined with air pollution? That is the question that Schnell and his colleagues wanted to understand. In order to carry out this study, the researchers examined 15 years of surface observations (1999–2013) for the eastern United States and Canada. The researchers overlaid a grid of one-degree-square segments onto a map of the region and analyzed the recorded levels of surface ozone, amounts of fine particulate matter (pollution), and maximum temperatures between April and September for each year. This allowed them to construct a climatological picture of the duration, coincidence, and overlap of each of these factors.

The research suggests that slow-moving high-pressure systems in summer accumulate pollutants and heat. Scorching temperatures, low precipitation, strong sunlight, and low wind speeds allow heat and poor-quality air to stagnate in a given location for an extended period of time.

“These conditions increase the emission of biogenic volatile organic compounds, which boost the production of surface ozone and other aerosols,” said Schnell. “The droughtlike conditions that exist in heat waves reduce soil moisture, making near-surface temperatures hotter and inhibiting the role played by vegetation in absorbing ozone, resulting in lower air quality.” These factors combine to worsen the health impacts on humans, leading to more heat-related deaths.

The scientists hope that their reserach will help us understand how heat waves combined with pollution can affect human health because they expect the conditions that lead to human mortality will only increase in the future with a warming climate.

Now try and answer these questions:

  1. How does a heat wave affect the level of pollutants in a given area?
  2. Worldwide, how many people died from the nine of the top 10 heat waves since 2000?
  3. How did Schnell and his colleagues conduct their research?
  4. What were some of their conclusions?
  5. Can you think of another way scientists could study the impact of heat on human health? What about how cold temperatures affect people?

You can learn more about how climate change can affect human populations by listening to Climate Change & Conflict.

Going Further

For Educators

This Science Update could be a good way to get your students interested in the research being done in the area of climate change and how it affects humans. It could also be used to show how the factors associated with a warming world and pollution can feed off of each other and produce effects that might not have been anticipated.

You could supplement this Science Update with these other Science NetLinks resources:

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Endocrine Disruptors
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Toxicology 1: Toxicology and Living Systems
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Antibacterial Pollution
6-12 | Audio

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