Sept. 14 (UPI) -- Air quality ranked the worst in the world Monday in Oregon, Washington and Vancouver, B.C. as smoke from hundreds of western wildfires choked the air in the Pacific Northwest.
The U.S. Environmental Protection Agency's Air Quality Index was ranked as "hazardous" for cities in Portland, Ore., Seattle and Spokane, Wash., and Vancouver, the agency's website said.
Portland was ranked the big city with the worst air quality in the world Monday by air quality site IQAir. Following were Vancouver, B.C. and Seattle, as well as Jakarta, Indonesia and Delhi, India.
Smoke from wildfires turns the sky orange in mid-day and mixes toxic gases plus fine particles from burning trees and other plant materials, the Oregon Health Authority said. Smoke causes eyes to burn, and can irritate the respiratory system, worsening chronic lung and heart diseases.
Hazardous level air quality is recorded on the EPA's Air Quality Index at levels above 300, where the entire population is more likely to be affected and an emergency health warning is triggered.
On Monday, areas in the Pacific Northwest recorded "beyond index" hazardous air quality levels at up to and above 500.
In Chelan, Wash., west of Seattle, fine particle levels measured at 510 on the index scale on Monday. Vancouver, Wash., recorded 477 on the index scale.
An interactive map from the Washington State Department of Ecology showed air quality throughout most of the Puget Sound region ranking as "hazardous" as of Monday.
Sweet Home, Ore., northeast of Eugene, recorded an index measurement of 469.
In these ranges, everyone should take steps to reduce their exposure by staying indoors - in a room or building with filtered air and reduce activity levels to avoid breathing in particulates, the EPA said.
Even healthy people may experience temporary symptoms such as irritation of the eyes, nose, and throat as well as coughing, phlegm, chest tightness and shortness of breath, the agency said.
Those at risk include children, the elderly and people with lung disease such as asthma and COPD, who may experience difficulty breathing. Those with heart disease or vascular disease run an increased risk of heart attack or stroke, which could strike in a short period of time exposed.
Health departments recommend staying in rooms with filtered air or air conditioners with filters and to avoid smoking.
Wildfires in Oregon have killed at least 10 people and left 22 missing. More than 40,000 Oregonians have been forced to evacuate and about half a million are on some level of evacuation status as fires have burned more than 1 million acres in the state, Oregon's Gov. Kate Brown reported Sunday.
"Without question, our state has been pushed to its limits," Brown told the Washington Post on Monday.
"The smoke blanketing the state is a constant reminder that this tragedy has not yet come to an end," Brown added.