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Beyond Heatwaves: How Rising Temperatures Affect Our Health

Yale Public Health Magazine, Focus: Spring 2024
by Kai Chen


When we talk about heat, what are we talking about? The health effects of temperature are really two-fold, if it gets either too hot or too cold, people can die, and people can get sick.

Heat does not have to be extreme to become deadly. Moderately hot temperatures can also cause substantial health burdens because we typically experience more moderately hot days than days of extreme heat.

We recently studied the health effects of extreme heat in Connecticut using data from the state’s mortality database. We found that the number of deaths from extreme heat and moderate heat in Connecticut was 31 (extreme heat, defined as temperature above the 90th percentile of the warm season temperatures from May to September) and 43 (moderate heat) deaths per year from 2005 to 2016, resulting in a total of 74 heat-related deaths per year. This result can help support state-wide action to lessen the negative health effects of moderate and extreme heat.

The challenge is not only that the climate is getting warmer, but that the world’s population is aging. We recently published a study that shows that an aging global population is expected to be a major driver of climate-related deaths.

For the study, we looked at 800 locations from 50 countries/regions of the world. When we look at the temperature and mortality relationship, we see that, relatively speaking, older adults compared to younger adults have higher risks not only from heat, but also from cold.

Older adults are among the most vulnerable populations when it comes to extreme temperatures due to their more limited thermoregulatory responses, a relatively high prevalence of chronic conditions, and a higher likelihood that they are socially isolated. Understanding the impact of population aging and climate change can provide important insights into future health burdens.

So what are some effective interventions to reduce heat? To answer that question, we first need to find out which communities are more vulnerable to heat. We recently developed a national metric to gauge heat vulnerability at the census-tract level and created a color-coded interactive map for public use.

When we looked statewide or nationwide, we found that people living in communities that are historically redlined, or cities with more Black or Latino populations, are more vulnerable to heat. We are indeed looking at an issue that is impacting all of us, but that is impacting us in different ways because of residential disparities.

We want this tool to be used by the public so that we can raise awareness of how vulnerable their communities are and help them take appropriate action. But also, we want this to be used by policymakers so that they can see the distribution within their state, or even nationally, so that they can have certain communities in mind when they implement climate adaptation policies.

One final note about smoke waves. Last year, New York City’s sky turned orange due to wildfire smoke from Canada. What was in the smoke? Small particles that we call fine particulate matter. The wildfire smoke had such a high concentration of these particles that it turned the sky orange, which tells you how polluted the air is during a smoke wave.

We did a study to look at the EPA monitor stations and saw that in New York City, the daily average level of fine particulate matter pollution was roughly above 150 micrograms per cubic meter on June 7, 2023. Usually in New York City, that level should be well below 35 micrograms per cubic meter – the EPA daily air quality standard.

What does that mean for our health? Well, those small particles are small enough to penetrate the lungs and circulate throughout the body. This can lead to respiratory illness but also can trigger heart attacks and strokes, aggravate kidney disease, and damage brain health leading to cognitive decline and dementia.

What makes it worse is that extreme heat could enhance the health effects of wildfire smoke. With a warming climate, the health burden of exposure to extreme heat and wildfire smoke is expected to increase.

Your Action Item For Change:

Review the heat vulnerability map. Search for your city and zip code. How vulnerable is your neighborhood to heat?

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