Even low-level air pollution may harm health

A hazy cityscape with the world in the foreground and a factory burning fossil fuels with a dark cloud of pollution rising into the sky

A new scientific report supports research suggesting that even low levels of pollution — well below the current national regulatory cutoffs — may harm our health.

Outdoor air pollution stems largely from the burning of fossil fuels (coal, gas, oil), which generate noxious gases, smog, and soot. Smog, which makes air look hazy, is created by ground-level ozone. Soot is fine particles — you may see a dusting of soot on a windowsill, for example. The burning of fossil fuels is a major contributor to climate change that occurs over years, but it has more immediate health effects.

How can air pollution affect our health?

Research links increased levels of fine particles in the air that are tiny enough to be easily inhaled (called PM2.5) to more hospitalizations for heart disease, stroke, diabetes, and pneumonia. It also worsens existing lung disease, known as chronic obstructive pulmonary disease (COPD), and may cause other serious health problems. Both long-term exposure and short-term exposure seem to matter to our health.

A 2021 study looked at global models of pollution levels and risk assessments of the world population over 14 years. It tied fossil fuel alone to nearly nine million premature deaths worldwide in 2018 — that’s one in five deaths — including more than 350,000 in the United States. Most of these deaths are due to heart attacks and strokes.

People with underlying health conditions like asthma, heart disease, or diabetes, older adults, and people who live in low-income communities, which are often situated near polluting sources, are among those who are more likely to be harmed by air pollution.

How does low-level pollution affect us?

In the US, air pollution has improved quite a bit since the passage of the 1970 Clean Air Act. Current air quality standards set by the Environmental Protection Agency (EPA) spell out a certain annual threshold of particulates aimed at protecting health. But as we learn more about complex relationships between pollution and our ecosystem, growing evidence suggests that harm may occur at PM2.5 levels lower than the current standard.

The new Health Effects Institute report (note: automatic download) studied 68 million older Americans from all but two states across the US over a 16-year period.

The researchers had set themselves an incredibly challenging question to answer. There are innumerable variables to calculate: an individual’s exposure to pollution based on where they live, the independent contribution of the major air pollutants separately, health and behavior confounders that factor into mortality, and more.

The study drew on Medicare demographic and mortality data from more than 68 million Americans ages 65 and older. Calculations of yearly average pollution exposures came from multiple sources, including the EPA Air Quality System monitoring and satellite-derived data. The authors adjusted for many factors known to affect health, such as socioeconomic status, smoking, and body mass index. They developed several statistical models, all of which demonstrated similar results: between 2000 and 2016, death rates rose by 6% to 8% for each incremental increase in PM2.5 exposure.

Just how small were these increases in exposure to air pollution? Particle pollution is measured in micrograms per cubic meter of air (μg/m3). Each time exposure levels rose by 10 μg/m3, death rates also rose by 6% to 8%. Excess deaths occurred even at low levels of PM2.5 exposure (2.8 μg/m3), which is well below the current EPA standards cutoff. The study authors estimate that adjusting the cutoff down from the current level of 12 μg/m3 to 10 μg/m3 could save more than 143,000 lives over 10 years.

What are the limitations of this study?

One limitation is that the variety of data are compiled at different levels: the individual, zip code, and county level. For example, pollution exposure is estimated in clusters by zip code. Yet someone living near a highway may have higher exposure than another person living further from the highway in the same zip code.

Additionally, the groups with the lowest PM2.5 exposure most likely exclude many cities and include a higher proportion of rural areas. Rural areas tend to be less dense, have fewer air quality data points, and may have zip codes spanning greater distances. Details like these may affect the certainty of conclusions that can be drawn. Nonetheless, this study has many groundbreaking features with sound science.

Staying healthy: The bottom line

Air pollution is known to contribute to disease and death. Now we have more evidence suggesting that this is true even at low levels of pollution. Currently the US is considering whether to adjust regulatory cutoffs for annual fine particulate matter pollution known as PM2.5 to protect human health.

But don’t wait. You can take steps described in my previous blog post to reduce your exposure (and contribution) to pollution, and thus your health risks. And some of these steps have the added benefit of combatting climate change and improving planetary health.

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Strong legs help power summer activities: Hiking, biking, swimming, and more

Older woman wearing black cycling clothes and a blue helmet riding a bicycle on a roadway with flowering trees bushes and tress lining the roadside

My favorite summer activities officially kick in when the calendar flips to May. It’s prime time for open water swimming, running, cycling, hiking, and anything else that gets me outside and moving. Yet, my first step is to get my legs in shape.

“Legs are the foundation for most activities,” says Vijay Daryanani, a physical therapist at Harvard-affiliated Spaulding Rehabilitation Hospital. “They’re home to some of the body’s largest muscles, and building healthy legs can improve one’s performance, reduce injury, and increase endurance.”

Four leg muscle groups to build for summer activities

Four muscles do the most leg work: quadriceps, gluteus maximus (glutes), hamstrings, and calves. Here is a look at each.

Quadriceps (quads). Also known as the thigh muscles, the quads are a group of four muscles (hence the prefix “quad’). They extend your leg at the knee and power every leg action: stand, walk, run, kick, and climb.

Glutes. The body’s largest muscles, the glutes (your buttock muscles) keep you upright and help the hips and thighs propel your body forward.

Hamstrings. The hamstrings are a group of three muscles that run along the back of your thighs from the hip to just below the knee. They allow you to extend your leg straight behind your body and support hip and knee movements.

Calves. Three muscles make up the calf, which sits in the back of the lower leg, beginning below the knee and extending to the ankle. They work together to move your foot and lower leg and push you forward when you walk or run.

Spotlight muscle strength and length

Strength and length are the most important focus for building summer-ready legs, says Daryanani. “Strengthening leg muscles increases power and endurance, and lengthening them improves flexibility to protect against injury.”

If you are new to exercise or returning to it after time off, first get your legs accustomed to daily movement. “Start simply by walking around your home nonstop for several minutes each day, or climbing up and down stairs,” says Daryanani.

After that, adopt a walking routine. Every day, walk at a moderate pace for 20 to 30 minutes. You can focus on covering a specific distance (like one or two miles) or taking a certain number of steps by tracking them on your smartphone or fitness tracker. You won’t just build leg strength — you’ll reap a wide range of health benefits.

There are many different leg muscle-building exercises, some focused on specific activities or sports. Below is a three-move routine that targets the four key leg muscles. Add them to your regular workout or do them as a leg-only routine several times a week. (If you have any mobility issues, especially knee or ankle problems, check with your doctor before starting.)

To help lengthen your leg muscles and increase flexibility, try this daily stretching routine that includes several lower-body stretches.

Dumbbell squats

Muscles worked: glutes and quads

Reps: 8-12

Sets: 1-2

Rest: 30-90 seconds between sets

Starting position: Stand with your feet apart. Hold a weight in each hand with your arms at your sides and palms facing inward.

Movement: Slowly bend your hips and knees, leaning forward no more than 45 degrees and lowering your buttocks down and back about eight inches. Pause. Slowly rise to an upright position.

Tips and techniques:

  • Don’t round or excessively arch your back

Make it easier: Do the move without holding weights.

Make it harder: Lower yourself at a normal pace. Hold briefly. Stand up quickly.

Reverse lunge

Muscles worked: quads, glutes, hamstrings

Reps: 8-12

Sets: 1-3

Rest: 30-90 seconds between sets

Starting position: Stand straight with your feet together and your arms at your sides, holding dumbbells.

Movement: Step back onto the ball of your left foot, bend your knees, and lower into a lunge. Your right knee should align over your right ankle, and your left knee should point toward (but not touch) the floor. Push off your left foot to stand and return to the starting position. Repeat, stepping back with your right foot to do the lunge on the opposite side. This is one rep.

Tips and techniques:

  • Keep your spine neutral when lowering into the lunge.
  • Don’t lean forward or back.
  • As you bend your knees, lower the back knee directly down toward the floor with the thigh perpendicular to the floor.

Make it easier: Do lunges without weights.

Make it harder: Step forward into the lunges, or use heavier weights.

Calf raises

Muscles worked: calves

Reps: 8-12

Sets: 1-2

Rest: 30 seconds between sets

Starting position: Stand with your feet flat on the floor. Hold on to the back of a chair for balance.

Movement: Raise yourself up on the balls of your feet as high as possible. Hold briefly, then lower yourself.

Make it easier: Lift your heels less high off the floor.

Make it harder: Do one-leg calf raises. Tuck one foot behind the other calf before rising on the ball of your foot; do sets for each leg. Or try doing calf raises without holding on to a chair.