Hot days aren’t just a nuisance—they can be deadly. According to a report from the Centers for Disease Control and Prevention, extreme heat kills hundreds of people each year and is the number-one cause of weather-related deaths in the United States, beating out the effects of tornadoes, floods, hurricanes and cold.

Temperatures are on the rise in the Chesapeake watershed, and that can have serious implications for our health. Our atmosphere acts like a blanket surrounding the earth. When we burn fossil fuels for energy, we release carbon dioxide, which thickens the blanket. The additional heat that is trapped is causing global temperatures to rise and disrupting the climate.

Here, we focus on the impacts of rising temperatures on human health. Check out future blogs to learn about impacts to Chesapeake wildlife and agriculture.

How are temperatures changing across the Chesapeake?

The Chesapeake Bay Program tracks air temperature in the Chesapeake watershed using data from 1901-present. These data show that temperatures in the Chesapeake region have been on the rise for years. While certain local conditions may vary, the warming trend across the region is clear. Today, the region experiences 30 more warm summer nights (above 65 degrees Fahrenheit) per year compared to 100 years ago, and a study by U.S. Geological Survey found that from 1960 to 2010, air temperatures in the region have increased an average of 1.98 F.

Though an average increase of a few degrees for daily temperatures might not seem like much, we are also experiencing extreme heat events—defined by the Centers for Disease Control and Prevention as conditions much hotter or more humid than average for the place and time—that are more common, more severe and longer lasting.

Unfortunately, the projected rate of warming for the region isn’t slowing down. Depending on how much we reduce our global emissions, projections indicate warming of 4.5 F to 10 F in the watershed by the 2080s.

These temperature increases have a variety of impacts across the region. For example, the U.S. Department of Agriculture has changed plant hardiness zones—geographic areas with particular climatic conditions that help growers choose which plants to choose for their area—throughout the United States as our region warms, and we now see longer growing seasons and fewer days with frost on average than we did just 25 years ago. Taken together, temperature changes affect conditions for the residents, wildlife and agriculture of the region.

Effects on human health

Heat-related illness

When temperatures are high enough, our bodies aren’t able to cool themselves down fast enough to maintain our ideal 98.6 F temperature. Once we are outside of the healthy body temperature range, we can experience heat exhaustion, characterized by fatigue, dizziness, nausea and heavy sweating. If we can’t cool ourselves down—by moving into air conditioning, taking a cool shower, hydrating or stopping activity—we can move into heat stroke. Heat stroke occurs when body temperature is well above normal (often around 104 F) and can lead to confusion, headaches, unconsciousness or even death.

While extreme heat affects everyone, some populations are at higher risk of negative impact. For example, those in the northern reaches of the watershed or low-income groups may be less likely to have access to air conditioning. Children, the elderly and those with existing medical conditions are also more vulnerable, because they are more susceptible to respiratory problems and/or less able to effectively regulate their body temperature.

Those who live in cities with little tree cover are also more exposed to heat-related impacts due to the phenomenon known as the urban heat island effect. When paved surfaces like roads absorb sunlight during the day, they increase in temperature. That heat is released at night, and when this happens in a city full of paved surfaces, the temperature of the whole city can be much warmer than surrounding areas.

Baltimore Tree Trust staff member waters tree planted in highway median

Staff from Baltimore Tree Trust water and maintain young trees planted by Blue Water Baltimore as part of a green infrastructure project along Route 40 in Baltimore on July 24, 2019. The two nonprofits work in collaboration with Baltimore Department of Recreation and Parks' TreeBaltimore initiative to increase the amount of tree canopy in the city. (Photo by Will Parson/Chesapeake Bay Program)

Respiratory impacts

As temperatures are staying warmer throughout more of the year, pollen season is becoming longer. Longer seasonal exposure to pollen is a nuisance for some but can pose a more serious threat to people with asthma or other breathing conditions.

High temperatures can also increase the formation of ozone. Ground-level ozone forms when pollutants from cars, power plants and more react in heat and sunlight. While the ozone layer in the atmosphere protects us from UV rays, ozone that forms at the ground level can damage lung tissue, cause serious respiratory problems like asthma attacks, and damage plant growth.

Tick-borne illness

Pollen isn’t the only thing that will be around for more of the year—insects like ticks will also be active for longer. A longer season of tick activity can lead to an increase in exposure to Lyme disease and other tick-borne illnesses. Tick-borne illnesses are already unusually common in the Chesapeake watershed, as Pennsylvania, New York, Maryland and Virginia all rank in the top 10 states with the most cases of tick-borne disease (from 2004-2016).

The incidence of Lyme disease across the country has nearly doubled since 1991, and though temperature increases are not the only factor, they do play a part. Symptoms of Lyme disease include fatigue, aches, fever and a rash around the bite—often in the shape of a bulls-eye.

Food safety

The Chesapeake Bay Program’s Scientific and Technical Advisory Committee reports that warmer temperatures can also impact human health through the food we eat. Increased temperatures can, for example, increase the uptake of mercury—a toxic contaminant with human health implications—in fish. Long-term exposure to toxic contaminants in our food can lead to serious health issues, including neurological problems and birth defects.

In addition, fish and shellfish parasites can become more prevalent in warmer waters. Increased parasite exposure can lead to illnesses if the fish is undercooked.

An increase in the incidence of infections from Vibrio is also associated with the Bay’s increasing temperature trend. While Vibrio occurs naturally in the Chesapeake Bay, the increase in human infections in recent years is correlated with rising temperatures and longer warm-weather conditions during the year, as well as the levels of nutrient pollution. These conditions make the Bay habitat more favorable to Vibrio organisms.

A Vibrio infection, called vibriosis, may occur when a person eats tainted shellfish or swims with open wounds in contaminated waters. When ingested, Vibrio can induce symptoms like those of food poisoning or influenza, including nausea, stomach cramping, diarrhea and fever. If Vibrio comes into contact with a wound, you might experience swelling, redness, blistering or pain in the wounded area.

What can we do?

One of the best ways to address these health problems is to reduce our greenhouse gas emissions. By reducing our use of fossil fuels, we produce less carbon dioxide and limit the amount of heat that is trapped by our atmosphere. The degree to which we reduce our emissions will be the biggest factor in determining future temperatures in the region. The impacts from an increase of 10 F by the 2080s will be much more severe than those from an increase of 4.5 F.

Driving or flying less, reducing energy use in your home, adopting a climate-friendly diet and switching to renewable energy are all great ways to reduce your carbon footprint. Check out our How To’s and Tips page for even more ideas.

However, because the carbon dioxide we have already emitted can stay in the atmosphere for a long time, a certain amount of increased warming is inevitable. There are certain actions we can take to try to adapt to this temperature increase.

Planting trees is a great way to make sure people are less impacted by high temperatures. A community science study funded by the National Oceanic and Atmospheric Administration found that on a hot August afternoon in D.C. and Baltimore, the coolest areas of the city—which had the highest amount of tree cover—could be as much as 16 to 17 F cooler than the hottest areas.

Raising awareness of the problem is also key. Many aren’t aware of the severe consequences that a hot day can have. Opening and making people aware of cooling centers in their neighborhood can be vital. Learn the signs of heat exhaustion and heat stroke, and know how to respond.

Learn more about how climate change is impacting the Chesapeake.



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