Month: January 2023

Here’s a new fact about spring, summer, fall, and sometimes even winter, now that climate change has blurred seasonal boundaries: sizzling heat may be on the way, or currently blanketing your community.

High temperatures stress the body, leading to thousands of heat-related illnesses and deaths every year in the US. Creating a personal heat plan can help you stay safe when the heat index soars.

Caleb Dresser, MD, MPH, is the health care solutions lead for C-CHANGE, the Center for Climate Health and the Global Environment at the Harvard T.H. Chan School of Public Health, and an emergency medicine doctor at Harvard-affiliated Beth Israel Deaconess Medical Center. Below we interview him about who, how, and why heat harms. Then we’ll help you create your personal heat safety plan.

Interview edited for clarity

Who is especially vulnerable during hot weather?

High temperatures can affect anyone. But some people — children, outdoor workers, people who are pregnant or have health problems or disabilities, and older people — are more likely to experience harm when temperatures rise. For example:

• Young children, especially babies, have less physical capacity to deal with very high temperatures.
• People working outdoors may not have access to shade and could be performing physically intensive labor. They need adequate hydration, adequate breaks, and access to a cool space during break time, as OSHA guidelines spell out.
• People with chronic medical conditions, such as kidney disease or heart disease, may have difficulty adapting physiologically to hot weather, or may be more susceptible to its health impacts.
• And some people living with disabilities or certain neurological conditions may have difficulty with thermoregulation — that is, controlling the temperature of their bodies — or may not be able to take actions that keep them safe, such as taking off layers or moving to a cool area.

Which weather patterns create dangerous levels of heat?

Dangerous heat is the result of both high temperatures and high humidity, which interfere with our ability to cool off by sweating. In dry areas, extremely hot temperatures can be dangerous on their own.

Danger zones vary across the United States and around the world. But hospital use and deaths rise once we get above threshold temperatures. The threshold varies in different places depending on whether bodies, cultures, and architecture are adapted to heat.

For example, here in New England, where some people (particularly those of limited means) may not have access to air conditioning, we see increases in healthcare use and deaths at a lower temperature than in the American South, where people and organizations may be more used to dealing with hot weather.

When does hot weather become dangerous to our health?

Risk goes up the longer hot weather sticks around.

One hot day can put some people at risk. A stretch of several hot days in a row during a heat wave is particularly dangerous because it can overwhelm people’s ability to adapt. Eventually people run out of physiological reserves, leading to greater health harms and greater need for medical care.

Surprisingly, spring and early summer are particularly dangerous times because people and organizations aren’t as prepared for hot weather.

How to create your personal heat safety plan

Five key points to help you create a personal heat plan are below. Americares offers further information through heat tip sheets developed with the Harvard C-CHANGE team that are tailored to people in different health circumstances.

Planning is important because intense heat is occurring more often: a Climate Central analysis found 21 additional risky heat days, on average, for 232 out of 249 locations between 1970 and 2022.

• Stay ahead of hot weather. Check apps, websites, TV, or radio for updates on weather today and in coming days. If local weather alerts are available by phone or text, sign up.
• Have a cooling plan. When temperatures soar, you need to spend as much time as possible in cool spaces. Plan options if your home is likely to be too hot and unsafe to stay in. You may be able to stay with a neighbor or family member who has air conditioning until a heat wave passes. Many cities and towns have neighborhood splash pads for children, and open cooling centers or air-conditioned libraries, public buildings, or community centers to everyone — sometimes even overnight. Spending time in air-conditioned businesses or malls, or in a shady green space like a park, may help too.
• Sip plenty of fluids. Water is the best choice. Skip sugary drinks and avoid caffeine or alcohol.
• Use fans correctly. Fans help if surrounding air is relatively cool. If air temperatures are very high, it’s important to dampen your clothes or skin to help keep your body from overheating, and move to a cooler location, if possible.
• Know your personal risks and the signs of heat-related illness. If you have health problems or disabilities, or take certain medicines such as diuretics, talk to your doctor about the best ways for you to cope with heat. It’s also essential to know the signs of heat-related illnesses, which range from heat rash and sunburn to heat cramps, heat exhaustion, and heat stroke. This chart from the Centers for Disease Control and Prevention describes the signs to look for and what you can do, particularly when heat becomes an emergency.

About the Author

Francesca Coltrera, Editor, Harvard Health Blog

Francesca Coltrera is editor of the Harvard Health Blog, and a senior content writer and editor for Harvard Health Publishing. She is an award-winning medical writer and co-author of Living Through Breast Cancer and The Breast … See Full Bio View all posts by Francesca Coltrera

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

There are warnings just about everywhere you look: The coffee you're about to drink is hot! Construction ahead! This product may contain peanuts!

In many cases, the reasons for these warnings are clear. But sometimes warnings raise more questions than they answer. When I was at the gym recently, these warnings on the exercise bike and treadmill were hard to miss in a bright red font:

• Obtain a medical exam before beginning any exercise program.
• Overexercise may result in serious injury or death.
• If you feel faint, dizzy, or have pain stop exercising immediately.

What exactly did the warning writers mean by "any exercise program"? What constitutes overexercise? Does having any pain anywhere mean you should stop working out?

Finally, I wonder: might these warnings cause unnecessary worry that actually discourages people from exercising?

Is it safe to start exercising without checking with a doctor?

A doctor's approval isn't necessary for most of us. Most people can safely begin a low-intensity exercise program and slowly increase their efforts over time. Choose activities that would allow you to carry on a conversation, such as:

• using light weights that are easy for you to lift
• walking at a leisurely pace
• biking at a leisurely pace (less than 5 mph)
• stretching and balancing activities
• light housework or yard work.

If you're starting at a low fitness level, make small increases in your workout over time. For example, if you start out walking 10 minutes a day, add one minute to your walk every week or two. Once you're walking 20 minutes a day, try picking up the pace a bit.

Who should be careful about exercising?

Of course, exercise is riskier if you have certain health conditions. It makes sense to ask a health care professional to make exercise recommendations if you're concerned about your health or have any of these conditions:

• Coronary artery disease, including symptoms of angina or a previous heart attack. Exercise that's too much too soon could stress the heart and trigger a heart attack or dangerous heart rhythm. Lower-intensity workouts (such as short walks at a comfortable pace) may be preferable, at least until it's clear that you can tolerate more.
• Exercise-induced asthma. Your doctor may recommend inhaled treatment to open up airways in your lungs just before or during exercise.
• Muscle disease, such as a metabolic myopathy. Your doctor may discourage you from engaging in certain exercises, such as sprinting or long-distance running.
• Back pain. Low impact exercise, such as biking or swimming, may be a better choice for people with back pain than higher-impact options, such as jogging or basketball.

If exercise is so good for you, why the warnings?

Let's review possible reasons for certain warnings:

• Having a medical examination before starting an exercise program might uncover a condition that makes exercise risky. The best example is probably coronary artery disease, which could trigger a heart attack during intense exercise. Fortunately, sudden heart problems during exercise are relatively rare (though you might think otherwise based on TV and movies, including an episode from the Sex and the City reboot).
• Overexercise is not a well-defined medical term. But it's true that suddenly exercising at high intensity when you're not used to it might be hazardous.
• Stopping exercise if you're feeling faint or dizzy presumably refers to concerns about severe dehydration or other causes of low blood pressure.
• Warnings about pain could refer to chest pain that might be a sign of heart trouble. Or it could be a warning about a type of severe muscle damage called rhabdomyolysis (which may complicate prolonged or intense exercise).

Of course, it's also possible these warnings have little to do with your health and everything to do with lawyers! That is, the equipment manufacturers might hope these warnings will ward off lawsuits from people who suffer a medical problem while using their equipment.

Are these warnings helpful?

Probably not.

All the warnings, alerts, and cautions in our everyday lives can become background noise. Despite red letters and bold fonts, warnings like these are easily overlooked.

Nor do they add much. My guess is that most people experiencing significant dizziness or pain during a workout will stop what they're doing even without reading a warning label. And serious medical conditions arising during exercise are rather rare, so the impact of warning everyone about them is likely small.

The bottom line

Don't be overly alarmed by alerts slapped on exercise equipment. True, it's best not to drop weights on your foot or exercise way too hard or long. If you are worried about workout risks or have been advised to be especially careful about exercising, it's reasonable to talk about it with your doctor.

But that conversation isn't necessary for most people, including those with well-controlled chronic illness such as high blood pressure, diabetes, or coronary artery disease. In fact, regular exercise helps treat many illnesses.

Exercise is among the most important things you can do to improve your health. And inactivity is a generally a much bigger risk than exercising.

So, if you see warnings on the gym equipment at your next workout, keep this in mind: there are much riskier things to worry about. Like hot coffee.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

Heavy rains and sea level rise contribute to major flooding events that are one effect of climate change. Surging water rushing into buildings often causes immediate harms, such as drowning deaths, injuries sustained while seeking shelter or fleeing, and hypothermia after exposure to cold waters with no shelter or heat.

But long after news trucks leave and public attention moves on, flooding continues to affect communities in visible and less visible ways. Among the less visible threats is a higher risk of respiratory health problems like asthma and allergic reactions. Fortunately, you can take steps to minimize or avoid flooding, or to reduce respiratory health risks after flooding occurs.

How does flooding trigger respiratory health issues?

Flooding may bring water contaminated with toxic chemicals, heavy metals, pesticides, biotoxins, sewage, and water-borne pathogens into buildings. Afterward, some toxic contaminants remain in dried sediments left behind. When disturbed through everyday actions like walking and cleaning, this turns into microscopic airborne dust. Anything in that dried flood sediment — the toxic chemicals, the metals, the biotoxins — is now in the air you breathe into your lungs, potentially affecting your respiratory health.

Buildings needn’t be submerged during flooding to spur respiratory problems. Many homes we studied after Hurricane Ida suffered water intrusion through roofs, windows, and ventilation ducts — and some were more than 100 miles away from coastal regions that bore the brunt of the storm.

The growth of mold can also affect health

Another common hazard is mold, a fungal growth that forms and spreads on damp or decaying organic matter. Indoor mold generally grows due to extensive dampness, and signals a problem with water or moisture. Damp materials inside buildings following a flood create perfect conditions for rapid mold growth.

Mold can be found indoors and outdoors in all climates. It spreads by making tiny spores that float through the air to land in other locations. No indoor space is entirely free from mold spores, but exposure to high concentrations is linked with respiratory complications such as asthma, allergic rhinitis, and sinusitis. Thus, flooding affects respiratory health by increasing the risk of exposure to higher concentrations of mold spores outdoors and indoors.

For example, after Hurricane Katrina in New Orleans in 2005, the average outdoor concentration of mold spores in flooded areas was roughly double that of non-flooded areas, and the highest concentrations of mold spores were measured indoors. A study on the aftermath of Hurricane Katrina and the flooding in the UK in 2007 showed that water damage accelerated mold growth and respiratory allergies.

Children are especially vulnerable to health problems triggered by mold. All respiratory symptoms — including asthma, bronchitis, eye irritation, and cough — occurred more often in homes reporting mold or dampness, according to a study on the respiratory health of young children in 30 Canadian communities. Other research demonstrates that mold contributes to development of asthma in children.

What can you do to protect against the health harms of flooding?

Our research in New Orleans, LA after Hurricane Ida in 2021 identified common factors — both in housing and flooding events — with great impact on respiratory health. Preliminary results suggest two deciding factors in whether substantial indoor mold appeared were the age of a building’s roof and how many precautionary measures people took after flooding from the hurricane. The impact on respiratory health also varied with flood water height, days per week spent at home, and how many precautionary measures were taken after Ida swept through.

Informed by this and other research, we offer the following tips — some to tackle before flooding or heavy rains, and some to take afterward. While you may not be able to entirely prevent flooding from hurricanes or major storms, taking these and other steps can help.

Before seasonal storms, flooding, or heavy rains start: Protect against water intrusion

• Repair the roof, clean gutters, and seal around skylights, vent pipes, and chimneys to prevent leaks. These are some of the most vulnerable components of a building during storms and hurricanes.
• Declutter drains and empty septic tanks.
• Construct barriers and seal cracks in outer walls and around windows, to prevent heavy rain and floodwater from entering.
• Install a sump pump to drain water from the basement, and backflow valves on sewer lines to prevent water from backing up into the home.

After flooding or major rainstorms: Move quickly to reduce dampness and mold growth

The Environmental Protection Agency recommends limiting contact with flood water, which may have electrical hazards and hazardous substances, including raw sewage. Additionally:

• Minimize your stay in flooded regions (particularly after hurricanes) or buildings until they are dry and safe.
• Check building for traces of water intrusion, dampness, and mold growth immediately after flooding.
• Drain floodwater and dispose of remaining sediment.
• Remove affected porous materials. If possible, dry them outdoors under sunlight.
• Increase the ventilation rate by leaving all windows and doors open, or use a large exhaust fan to dry out the building as fast as possible.
• Use dehumidifiers in damp spaces such as basements.
• Upgrade the air filters in your HVAC system to at least MERV 13, or use portable air cleaners with HEPA filters to reduce your exposure to airborne mold spores.

What to do if you spot mold growth

• Wear a well-fitted N95 face mask, gloves, and rubber boots to clean.
• Clean and disinfect anything that has been in contact with water using soap, detergents, and/or antibacterial cleaning products.
• Dispose of moldy materials in sealed heavy-duty plastic bags.

Taking steps like these — before and after a major storm — goes a long way toward protecting your respiratory health.

Read Flooding Brings Deep Trouble in Harvard Medicine magazine to learn more about the health hazards related to floods.

About the Authors

Parham Azimi, PhD, Contributor

Dr. Parham Azimi is a research associate in the department of environmental health at the Harvard T.H. Chan School of Public Health, investigating the indoor environment’s impact on occupant health and wellness and strategies to improve … See Full Bio View all posts by Parham Azimi, PhD

Joseph Allen, DSc, MPH, CIH, Contributor

Dr. Joseph Allen is an associate professor in the department of environmental health at the Harvard T.H. Chan School of Public Health, and the director of Harvard’s Healthy Buildings Program. He is the coauthor of Healthy … See Full Bio View all posts by Joseph Allen, DSc, MPH, CIH

There are certain things our bodies do so often and so automatically that we barely notice them. Yawning, growling stomachs, and runny noses are good examples. Each is a universal part of our daily human experience.

But did you ever wonder why? Below are a few things we know and a few we suspect.

Why do you yawn?

Perhaps you associate yawning only with being tired or bored. While we don’t know exactly why people yawn, there’s no shortage of theories. Yawning may

• stretch out our lungs and nearby tissues, preventing tiny airways in the lungs from collapsing
• distribute a chemical called surfactant, a gooey liquid that coats the tiny air pockets in the lungs and helps keep them open
• help prepare our bodies for transitions between wakefulness and rest: For example, yawning often occurs after a period of relaxation and when awakening from sleep. And it may serve as an internal signal that it’s time to sleep, or time to take a break from activities (such as driving).
• play a role in maintaining proper brain temperature: Our brain functions best within a narrow range of temperatures. Some experts believe yawning can help cool the brain through complex effects on nearby circulation and the sinuses.

It’s also unclear why yawning is contagious. In the animal kingdom, it’s common to see contagious yawning among members of a group, perhaps as a signal for collective behavior (such as moving from activity to rest).

Why does your stomach growl?

That rumbling in your stomach is known medically as borborygmi — an excellent Scrabble word if you have the right letters. We usually assume it reflects hunger. And it’s true that the experience of hunger can make itself heard in anticipation of a meal.

But your stomach may also growl after a meal, when the stomach and intestines propel liquids and food through the digestive tract. Stress can also trigger stomach rumbling.

What’s causing all that noise — and is it ever a problem? It may be due to gas moving around in response to muscular contractions of the intestinal walls. Occasionally, noises from the abdomen may be a sign of an intestinal infection or other trouble. If you’re experiencing other symptoms, such as pain or fever, check in with your doctor. But the vast majority of noises are harmless and a sign that your gut is working normally.

Why does your nose run?

Sometimes it can seem like your nose is running for no reason. But there are some well-known triggers, such as:

• Infection. When you have a cold, mucous membranes produce more mucus as part of your defense system: more mucous flowing out means fewer germs getting in.
• Allergies. Pollen, ragweed, or other triggers stimulate immune cells that produce histamine. Histamine opens up blood vessels just beneath the mucous membranes, and that leads to increased production and release of fluid and mucus. As with infection, this response may be helpful to dilute the offending trigger and rid it from the area.
• Cold, dry air. The inside surface of the nose is covered with mucous membranes that warm and humidify air well before it reaches the lungs. When you inhale dry, cold air through your nose, these membranes humidify the air by secreting water and mucus.
• Spicy foods. Spices like capsaicin act as an irritant to the sinuses and mucous membranes, which release fluid in response.

The bottom line

Some of the most common everyday human experiences are also some of the least understood. There are many other examples, of course: Why are we ticklish? What purpose do hiccups serve? What’s the deal with brain freeze? Perhaps topics for another day.

It may seem like a leap of faith, but it’s likely there are very good reasons for the way our bodies work — even when we don’t know what those reasons are.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD