The juxtaposed photos above are taken from the same spot near the Golden Gate Bridge in San Francisco, showing an orange sky on Sept. 9, 2020, and a clear sky on Oct. 11, 2020. Use the arrows to toggle between the photos.
SANTA CRUZ, Calif. — Wildfires churning out dense plumes of smoke as they scorch huge swaths of the U.S. West Coast have exposed millions of people to hazardous pollution levels, causing emergency room visits to spike and potentially thousands of deaths among the elderly and infirm, according to an Associated Press analysis of pollution data and interviews with physicians, health authorities and researchers.
Smoke at concentrations that topped the government's charts for health risks and lasted at least a day enshrouded counties inhabited by more than 8 million people across five states in recent weeks, AP's analysis shows.
Major cities in Oregon, which has been especially hard hit, last month suffered the highest pollution levels they've ever recorded when powerful winds supercharged fires that had been burning in remote areas and sent them hurtling to the edge of densely populated Portland.
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Based on prior studies of pollution-related deaths and the number of people exposed to recent fires, researchers at Stanford University estimated that as many as 3,000 people over 65 in California alone died prematurely after being exposed to smoke during a six-week period beginning Aug. 1. Hundreds more deaths could have occurred in Washington over several weeks of poor air caused by the fires, according to University of Washington researchers.
Wildfires are a regular occurrence in Western states but have grown more intense and dangerous as a changing climate dries out forests thick with trees and underbrush from decades of fire suppression. What makes the smoke from these fires dangerous are particles too small for the naked eye to see that can be breathed in and cause respiratory problems.
Fires across the West emitted more than a million tons of the particles in 2012, 2015 and 2017, and almost as much in 2018 — the year a blaze in Paradise, California killed 85 people and burned 14,000 houses, generating a thick plume that blanketed portions of Northern California for weeks.
Below are four more pairs of before-and-after photos. From top to bottom: Crissy Field in San Francisco; Columbus Avenue, San Francisco; downtown Seattle and CenturyLink Field; and T-Mobile Park in Seattle.
Photos: Orange skies, hazardous pollution
These photos show the effects of wildfires that an Associated Press analysis finds have exposed millions of people to hazardous pollution levels.
Photos: Fires create orange skies, hazardous pollution
Wildfire smoke
This Sept. 9, 2020, file photo shows a dark orange sky above Crissy Field and the city of San Francisco due to heavy smoke from wildfires. An Associated Press analysis of air quality data shows 5.2 million people in five states were hit with hazardous levels of pollution for at least a day. (AP Photo/Eric Risberg)
Orange sky
In this Sept. 9, 2020, file photo, an orange sky is seen over Columbus Avenue, the Transamerica Pyramid and Salesforce Tower due to heavy smoke from wildfires in San Francisco. (AP Photo/Eric Risberg)
Golden Gate Bridge
In this Sept. 9, 2020, file photo, people stop near Fort Point by the Golden Gate Bridge to take pictures of an orange sky caused by heavy smoke from wildfires in San Francisco. (AP Photo/Eric Risberg)
Wildfire smoke
In this Sept. 12, 2020, file photo, smoke from wildfires in Oregon and California create hazy skies as the sun is seen above the Washington state Capitol in Olympia, Wash. (AP Photo/Ted S. Warren)
T-Mobile Park in Seattle
In this Sept. 14, 2020, file photo, smoke from wildfires in Oregon and California create hazy conditions at T-Mobile Park in Seattle during a baseball game between the Seattle Mariners and the Oakland Athletics. (AP Photo/Ted S. Warren)
Seattle
In this Sept. 14, 2020, file photo, downtown Seattle is barely visible through wildfire smoke near CenturyLink Field, right, as viewed from an upper deck of T-Mobile Park, home of the Seattle Mariners baseball team. (AP Photo/Ted S. Warren)
Photos: Fires' smoky haze is spreading across country
Western Wildfires Smoke Stretches East
This photo taken at sunrise from Surf City on Long Beach Island in New Jersey shows the sun shrouded in smoke and brown haze Tuesday, Sept. 15, 2020. The smoke from dozens of wildfires in the western United States is stretching clear across the country — and even pushing into Mexico, Canada and Europe. While the dangerous plumes are forcing people inside along the West Coast, residents thousands of miles away in the East are seeing unusually hazy skies and remarkable sunsets. (Elizabeth Laird via AP)
Pacific Northwest Wildfires Smoky Skies
A family of ducks swims on Oswego Lake, which is almost completely obscured by wildfire smoke, in Lake Oswego, Ore. on Monday, Sept. 14, 2020. The entire Portland metropolitan region remains under a thick blanket of smog from wildfires that are burning around the state and residents are being advised to remain indoors due to hazardous air quality. (AP Photo/Gillian Flaccus)
Wildfires Smoky Skies
A worker waters grass at Alamo Square Park as smoke from wildfires and fog obscures the skyline above the "Painted Ladies," a row of historical Victorian homes, in San Francisco, Monday, Sept. 14, 2020. (AP Photo/Jeff Chiu)
WESTERN WILDFIRES SMOKY SKIES
A hummingbird visits a red canna lilly flower to gather nectar while the morning sun in Springfield, Ill., is diffused by smoke from massive wildfires in western states nearly 2,000 miles away. The National Weather Service in Lincoln, Ill., said the sky in central Illinois will remain hazy the next few days. (Ted Schurter/The State Journal-Register via AP)
Western Wildfires Smoky Skies
A sign at a Whole Foods in Lake Oswego, Ore., advises that the store is closed due to poor air quality Monday, Sept. 14, 2020. Another sign said all Whole Foods stores in the Portland Metro area will be closed at least through Thursday due to air quality. People across the West struggled under acrid-yellowish green smog from raging wildfires that seeped into homes and businesses, sneaked into cars through air conditioning vents and caused the temporary closure of iconic locations such as Powell's Books and the Oregon Zoo. And forecasters say the putrid air, measured as the worst on the planet, could last well into the week. (AP Photo/Gillian Flaccus)
Western Wildfires Smoky Skies
The sun sets in a hazy sky over a cornfield in Antrim Township near Greencastle, Pa., Tuesday, Sept. 15, 2020. Smoke from wildfires burning on the West Coast has traveled across the United States through the jet stream and could stay in the region over the next few days. (Colleen McGrath/The Herald-Mail via AP)
Western Wildfires Smoke Stretches East
Traffic flows on Townline Road as a hazy sun sets in Vernon Hills, Ill,, Tuesday, Sept. 15, 2020. The smoke from dozens of wildfires in the western United States has now blanket much of the county along with parts of Mexico and Canada, as residents thousands of miles away on the East Coast are being treated to unusually hazy skies and remarkable sunsets. (John Starks/Daily Herald via AP)
Western Wildfires Smoke Stretches East
A person crosses a bridge against a hazy sunset over Century Park in Vernon Hills, Ill,, Tuesday, Sept. 15, 2020. The smoke from dozens of wildfires in the western United States has now blanket much of the county along with parts of Mexico and Canada, as residents thousands of miles away on the East Coast are being treated to unusually hazy skies and remarkable sunsets. (John Starks/Daily Herald via AP)
Western Wildfires Smoke Stretches East
A man looks a his cell phone while crossing a bridge as a hazy sun sets over Century Park in Vernon Hills, Ill., Tuesday, Sept. 15, 2020. The smoke from dozens of wildfires in the western United States has now blanket much of the county along with parts of Mexico and Canada, as residents thousands of miles away on the East Coast are being treated to unusually hazy skies and remarkable sunsets. (John Starks/Daily Herald via AP)
Western Wildfires Smoke Stretches East
A hazy sun sets over Richmond, Va., Tuesday, Sept. 15, 2020. The smoke from dozens of wildfires in the western United States has now blanket much of the county along with parts of Mexico and Canada, as residents thousands of miles away on the East Coast are being treated to unusually hazy skies and remarkable sunsets. (Bob Brown/Richmond Times-Dispatch via AP)
