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DO YOU THINK GOOD HEALTH MAKES YOU impervious to smog? Tell that to 28-year-old 400-meter hurdler Ryan Tolbert-Jackson, who, back in 1997, developed debilitating asthma while competing at the World Track & Field Championships in Athens, Greece.

“My breathing was labored, and I fatigued easier,” she said later. “It was as if I had a virus or severe allergies.”

In fact, she suffered from overexposure to noxious air, which tends to hit exceptionally fit people the hardest.

“It’s not fair,” says Randall Brown, a pulmonologist with Children’s Healthcare of Atlanta, at Scottish Rite Hospital. “The healthiest individuals experience the worst exposure of anyone from exercising in pollution-heavy environments. In effect, they are the canaries in the coal mine, because their lungs are so sensitive.”

But it’s not just elite athletes who are at risk. Roughly 159 million people, more than half the population of the United States, now live in cities with unhealthy levels of pollution, so anyone exerting themselves outdoors should consider what they’re breathing. “The negative effects on health that can come from exercising on a bad day can outweigh the positive benefits of sticking to a training program,” says Ron Allice, director of the track-and-field program at the University of Southern California, in Los Angeles.

Does this mean you should toss out an exercise regimen at the first sign of brown haze? No, but you should be smarter about location and timing. Stick to the following tips and maximize your fresh-air exposure, inhaling the best O2 your city has to offer.

Work out before the morning commute. Pollution from the previous day has dissipated, there are fewer cars on the road, and ozone production (see ““), which requires direct sunlight, hasn’t peaked. Can’t get out early? Wait until after dinner, when rush hour has ended and ozone is on the wane.
Let wind be your friend. Breezes blow away pollutants, so USC track practice is scheduled for 2 p.m., says Allice, because a westerly sets up every day “like clockwork.”
Avoid high-traffic areas. Paths or parks next to freeways or major thoroughfares are trouble. Choose routes along quiet side streets.
Reduce your particulate intake. Exercise at a pace that allows you to breathe through your nose, and drink plenty of water to help produce mucus, a natural filter.
Lengthen your recovery. Follow the program used by Allice on smog-alert days: Triple the time to recover after each sprint, from one minute up to three minutes.
Beware cumulative, long-term exposure. “Lower levels of pollution that didn’t affect you last year will cause wheezing and coughing this year,” says Brown.
Move your workout inside. If the atmosphere is downright hazardous (see ““), skip the outdoors and work out at home, or wait until things improve.

Meet the Villains and the AQ Test

Meet the Villains
OZONE forms naturally when heat from the sun alters oxygen molecules by combining them with oxides, mostly from nitrogen oxides, to form O3. This is the stuff that burns your eyes and throat on dirty days and leads to asthma.
ORIGIN: Nitrogen Oxides, primarily from automobile exhaust, ramp up ozone production to toxic levels.

PARTICULATES, the visible and invisible dust and soot you might see on a white tablecloth at an outdoor bistro, end up in your lungs. This junk causes your throat and nose to constrict, immediately reducing lung capacity. With enough exposure, the effect can be permanent.
ORIGIN: Diesel engines, dust, smoke, coal-fired power plants, industrial factories, and cigarettes.

The AQ Test
On the weather page, your local paper publishes that day’s Air Quality Index (AQI) score on a scale of 0 to 500. Here’s what it means:

AQI: 0–50
HEALTH LEVEL: Good
TRAINING NOTES: High-intensity sports like soccer, basketball, and sprinting are A-OK.

AQI: 51–100
HEALTH LEVEL: Moderate
TRAINING NOTES: All outdoor
activities get a green light, but for high-intensity workouts, you should avoid midday’s peak ozone hours.

AQI: 101–150
HEALTH LEVEL: Unhealthy
for sensitive groups
TRAINING NOTES: Do not engage in any moderate to high-intensity sessions on these days. Easy training—slow and steady exercise—is the limit.

AQI: 151–500
HEALTH LEVEL: Unhealthy
to hazardous
TRAINING NOTES: What are you doing outside, for chrissakes?!

The Oxygen Network

You may now breathe easier: We’ve ranked over a dozen major metropolitan areas in the U.S. according to air quality—with detailed pointers on where and when to exercise.

(Ranked from Best to Worst Air Quality)

Portland, OR
Population: 1.918 million
No. 1 Pollutant: Particulates

Steer Clear: The Rose City scores high on the clean list, but the air becomes worse as you travel south down the Willamette Valley; summer breezes often flow this direction, taking pollution with it. On days when air is stagnant (not normally a problem in Greater Portland), ozone problems come into play and it’s advisable to reduce outdoor exercise.

Play Here: Portland and Beaverton, to the west, get the freshest oxygen. This includes the trails of Forest Park. The Columbia River Gorge, with its strong, channeled winds, is a great boon to the lungs; spring sees windsurfers booking it east to the sport’s mecca in Hood River, about 45 minutes upriver.

Minneapolis-St. Paul, MN
Population: 2.311 million
No. 1 Pollutant: Particulates

Steer Clear: St. Paul bears the brunt of Minneapolis’s pollution, with Ramsey County scoring the worst for air quality. Reduced breathability affects the Midway and Summit University neighborhoods, areas around the Twin Cities Airport, and nearby Fort Snelling State Park.

Play Here: Lake Calhoun is Minneapolis’s backyard playground. The Gateway Trail, which runs east from St. Paul to Stillwater, is free from auto traffic. The city’s American Lung Association chapter has its own jogging club, with a web site () that offers a list of routes and maps; try the six-mile loop around the Mississippi River, starting at St. Thomas University. And though it’s 75 miles away, head to Duluth, where you’ll enjoy the country’s best air quality.

Seattle, WA
Population: 3.125 million
No. 1 Pollutant: Particulates

Steer Clear: Tacoma and South Seattle (with its industrial base) are marked by high levels of bad air and increased rates of asthma. Winter use of woodstoves can foul the sky throughout the area. Though the northern suburbs tend to have the cleanest air, avoid exercising around the mall in Northgate where tailpipe exhaust from the bustling bus station nearby ups pollutants.

Play Here: Seattle’s ample precip, mild maritime temps, and miles of waterfront keep the city lung-friendly. Cleanest air is found on and around Puget Sound and in the city’s northwest. Top spots are the 534-acre Discovery Park and surrounding Magnolia. Or head 45 minutes east of the city to the western Cascades for a variety of hiking trails through Tiger Mountain State Forest and up 4,176-foot Mount Si.

San Francisco, CA
Population: 5.615 million
No. 1 Pollutant: Particulates

Steer Clear: Watch out for traps in the East and South Bay-Livermore, Concord, and San Jose. They bear the brunt of the area’s pollution. Avoid winter evening exercise in towns like Half Moon Bay, where cooler temperatures foster an increase of woodburning stoves and their accompanying particulates.

Play Here: The Bay Area’s notorious fog benefits air quality, thanks to the added moisture, so if you can’t see through it, you benefit from exercising in it. From the Marin Headlands down the peninsula to Palo Alto, you are free to go as hard as you want. Check out new hiking trails around Pacifica, windsurf beneath the Golden Gate, or take your yoga skills to Berkeley’s Tilden Botanic Garden, with ten acres of changing seasonal greenery.

Denver, CO
Population: 1.813 million
No. 1 Pollutant: Particulates

Steer Clear: The winter inversion layer wrecks havoc on Greater Denver, especially western ‘burbs including Golden, Boulder, and Jefferson County. Equally affected this season is the South Platte River Basin drainage area, which threads through downtown and hosts high levels of carbon monoxide. During the summertime, ozone blights much of the metroplex.

Play Here: You’ll find the sweetest air southeast of town, in the area surrounding Cherry Creek State Park. And why spend your free winter hours filling your lungs with city smog when the Rockies beckon with crystal-clear air.

Salt Lake City, UT
Population: 1.372 million
No. 1 Pollutant: Ozone

Steer Clear: Salt Lake City battles the air pollution front from both ends—December through February, an inversion layer traps polluted oxygen, and come summer, harsh ozone affects the basin. A recent Environmental Defense report said the area experiences too many days with worrisome air quality; as a result, the city has been ranked one of the nation’s 50 most-polluted areas for children.

Play Here: The Wasatch Range, and any outlying area above the 5,500-foot pollution layer, is almost always fresh and clear (when it’s not dumping snow). Park City, 31 miles to the east, is heralded for three major ski resorts: Park City Mountain Resort, Deer Valley and the Canyons, and Olympic-caliber cross-country skiing at Soldier Hollow. Summer options are equally bountiful.

New York, NY
Population: 13.671 million
No. 1 Pollutant: Ozone

Steer Clear: Avoid working out in the industrial corridor across the Hudson River—polluted air from upstate New York and central New Jersey blows right over to Staten Island, New York (this borough, part of Richmond County, has had the state’s highest ozone levels for the second consecutive year). And though air cleanup in the Bronx is improving, the borough is farther away from a water source to pull in cooling, cleaning coastal breezes, and its air quality suffers because of it.

Play Here: The challenge in Greater New York is to find a green space away from major traffic routes, but the city has set aside room: Bike through the interior of Central Park; hike through a natural deciduous forest in Inwood Hill Park; or, for one of the city’s most peaceful parks, head to the 243-acre Cunningham Park Preserve in Queens. Exercisers are also breathing pretty in and around Long Island Sound, the Atlantic Ocean, and Upper Hudson River.

Boston, MA
Population: 2.820 million
No. 1 Pollutant: Ozone

Steer Clear: The northeastern suburbs in Essex County score the worst for ozone in the Boston area. And according to a Natural Resources Defense Council Study, air toxins in Suffolk County are 128 times worse than advisable Environmental Protection Agency (EPA) levels.

Play Here: Areas around Boston Harbor and the Charles River are best for working out—just not during rush hour. Paul Revere Park in Charlestown has seven miles of bikeways; sailing lessons are offered from Piers Park in East Boston; and for healthy air and water, head to Carson Beach in South Boston, one of the area’s cleanest beaches. Know before you go: Check out the region’s daily levels of ozone, black carbon, and particulates at .

Detroit, MI
Population: 3.021 million
No. 1 Pollutant: Particulates/Ozone

Steer Clear: Detroit suffers from several forms of pollution, including emissions from power plants and industrial sectors, “transfer” pollution from the Midwest, and high traffic volume passing through the city. Southeasterly winds blow pollution up I-94 into the pricey suburbs northeast of Detroit and all the way to Port Huron. Wayne and Monroe counties have particulate problems.

Play Here: Go west. From Ann Arbor to Pontiac, you’ll be free to breathe hard. Canoers can paddle for hours down Ann Arbor’s Huron River, and the city’s par-72 Leslie Park Golf Course was ranked as one of the state’s best municipal courses. Come winter, drive the 12 miles west of Pontiac to get above it all at Alpine Valley, a ski resort with 25 runs and a snowboard terrain park.

Washington, D.C.
Population: 3.786 million
No. 1 Pollutant: Ozone

Steer Clear: Summer heat turns the nation’s capital into an ozone bath. Inside the Beltway, traffic adds to the problem. Ozone alerts generally fall between May and September when, according to a Natural Resources Defense Council report, air toxins are 207 times greater than what the EPA deems acceptable.

Play Here: That said, fewer toxins are found in the northern Rock Creek Park Area, with cross-country skiing and golf among its fitness options, and around the eastern outskirts of the Potomac River. Northwest of D.C., try the trails of Great Falls Park on the Maryland-Virginia border. Bonus: Montgomery County, Maryland, lays claim to the cleanest suburban air in the region.

Chicago, IL
Population: 8.257 million
No. 1 Pollutant: Particulates

Steer Clear: The factories and mills south of the city center are respiratory danger zones. During the summer, northerly winds, high temps and low moisture levels foul the city’s popular North Shore all the way to the Wisconsin border. Generally, the city experiences between 10 to 15 unhealthy days between May and September. During the winters, three counties violate small particulate regulations: Cook, DuPage, and Will.

Play Here: Fall through spring is the ideal time for lakefront activity. When the winds pull into town, they charge from the southwest to the north, so heading west is the cleanest bet. Try the wilds of the Palos Forest Preserves, 15 miles southwest of the Loop and a nice respite from major expressways. In the summertime, try Cook County’s forest reserve, which offers a great bike path that winds 15 miles through fields and tree-shaded woods.

Phoenix, AZ
Population: 3.303 million
No. 1 Pollutant: Ozone

Steer Clear: A recent report from the Arizona Public Interest Research Group noted that Phoenix had 12 smog-filled days, brought on by ozone, in 2003. Because of wind patterns, most ozone blows east to Fountain Hills. Gilbert and Chandler, southeast of downtown, have dust and particulate problems.

Play Here: Make your way north to the Phoenix Mountains Preserve for trail running and biking along the foothills. Or try a nighttime tryst—monthly moonlight hikes are offered at the Lake Pleasant Regional Park, 30 minutes north of town.

Atlanta, GA
Population: 3.057 million
No. 1 Pollutant: Ozone

Steer Clear: The city center is usually ten degrees warmer, and more polluted, than the surrounding countryside. On top of that, surrounding the metro area are several coal-fire power plants and high levels of intra-state traffic, both of which contribute to pollution. The worst time to exercise outdoors is between May and the end of September, when unhealthy ozone levels are highest.

Play Here: Because higher emission values start mid-state, around Macon, and work northward, exercisers should go 40 miles outside downtown Atlanta, to the leafy outskirts, to notice air improvements. The 26-year-old Chattahoochee River National Recreation Area has 12 different sites, and a combined 50 miles of hiking trails, spread around northern Georgia. Closest to downtown Atlanta is Cochran Shoals, just outside the freeway loop, near Smyrna.

Dallas-Ft. Worth, TX
Population: 3.811 million
No. 1 Pollutant: Ozone

Steer Clear: The worst times to exercise outside are May 1 through October 31, when ozone concentrations linger. If you must, hit the Trinity River parks in Dallas or Ft. Worth early (before 10 a.m.) or late in the day; rush-hour workouts can be a respiratory nightmare even in these urban oases. Additional pollutants tend to hover around the airports: DFW and nearby Grapevine, as well as Arlington Municipal and Denton Airport.

Play Here: The areas southwest of downtown Ft. Worth and its highway loop have fewer industrial areas, and, as a result, better air quality. Head to Benbrook Lake, in the southwest, or recreate in Weatherford, just west of Ft. Worth in Parker County: The 20-mile Lake Mineral Wells State Trailway begins just northwest of Weatherford and heads west through farm and ranch lands. Dallas residents can put sailboats in at Lake Ray Hubbard’s John Paul Jones Park. Or head southeast to Sunnyvale, in Kaufman County, to exercise your pipes.

San Diego, CA
Population: 2.906 million
No. 1 Pollutant: Ozone

Steer Clear: Transfer pollution from both Tijuana, Mexico, and Los Angeles and Orange counties has a history of wafting into San Diego County. Smog from vehicle emissions peaks between 1 p.m. and 4 p.m., is carried eastward and hovers at around 2,000 feet, which is why the mountaintop community of Alpine and surrounding eastern foothills suffer mightily from pollution May through October.

Play Here: Coastal towns from Mission Beach to Oceanside benefit from a steady, ocean breeze. Surfers enjoy fall swells at La Jolla. Hikers can take to the 6,512-foot Cuyamaca Peak at Cuyamaca Rancho State Park, well above the smog line, 40 miles east of the city. Winter offers the best views for miles in every direction.

Philadelphia, PA
Population: 4.646 million
No. 1 Pollutant: Ozone

Steer Clear: According to a Natural Resources Defense Council Study, the levels of air toxins in Philadelphia County are 297 times what the EPA deems safe. Emissions from power plants, automobile traffic, and transfer pollution from other states cause threatening levels of soot and smog. During summer, Camden, New Jersey, across the Delaware River from downtown Philly, sees its ozone levels skyrocket. Avoid Philadelphia’s southern industrial area as well.

Play Here: Stick to Fairmount Park and play hard there in winter, the city’s best time for fresh oxygen. Or while away the hours near the rivers, with their steady pull of air currents: The Schuylkill draws champion rowers from around the region and is the site of several annual regattas. Stick to the lower parts of the river, where there are fewer expressways.

Sacramento, CA
Population: 1.749 million
No. 1 Pollutant: Ozone

Steer Clear: An inversion layer, heavy traffic along Interstate 80 and Highway 50, and easterly winds trap pollution along the Sierra Nevada foothill towns of Colfax, Folsom, and Grass Valley. Summers are the worst time to be in these areas—as of late August this year, the Greater Sacramento area had already suffered 17 eight-hour violation days. For a five-day Greater Sacramento air quality forecast, check out .

Play Here: On the valley floor, exercise early in the morning. A popular choice is the 32-mile, paved American River Bike Trail, which runs from Folsom west to Old Sacramento. Or take in the refreshing winds that run over the Sacramento River; waterskiers put in around Freeport, south of Downtown. Your best bet is heading ten miles west of downtown to Davis, where westerly winds keep Sacramento’s pollution at bay.

Houston, TX
Population: 4.142 million
No. 1 Pollutant: Ozone

Steer Clear: Avoid the oil refineries and industrial plants around the commercial shipping channel. Areas that have reported some of the most eight-hour violation days occur around West Houston, Tom Bass, and near Clear Creek and Clear Lake high schools.

Play Here: Stick to the green spaces west of town, such as Memorial Park, along the Buffalo Bayou. Speed walkers can enjoy a pine-scented jaunt through Mercer Arboretum, in the northern suburb of Humble. And in Lake Jackson, a new 12-hole Wilderness Golf Course opened in late May.

Los Angeles, CA
Population: 14.561 million
No. 1 Pollutant: Ozone

Steer Clear: Because of high levels of ozone, San Bernardino and Riverside County residents should commit to working out at dawn. Regardless the time of day, it’s crucial to exercise away from major roads and freeways. West Siders should refrain from exercising at night, when pollution from the east sifts westward toward the coast. May through October are the worst months for outdoor exercise because fewer coastal breezes mean lingering pollution, higher levels of contaminants, and more occurrences of acid fog.

Play Here: Get thee to the beach between 10 a.m. and 3 p.m., when rush hour is reduced and onshore breezes are blowing away airborne crud. The farther west and north you head to exercise, the more your lungs will thank you. Run, rollerblade, or bike the 17-mile coastal trail that skirts the Pacific from Santa Monica to Hermosa Beach. Some of the eastern hills hold in polluted air pockets, but if you’re an avid hiker, better options include the 10,000-foot-high San Jacinto Mountains, which are fairly clean most of the time, and the wine country around Temecula.

*Air quality statistics and population figures compiled courtesy of The American Lung Association.