Phoenix residents are breathing unhealthy levels of pollutants that can cause lung damage, asthma and even premature death, according to a new report, released as the respiratory disease COVID-19 tightens its hold on Arizona.

Phoenix once again ranked among the nation’s 10 worst cities for two widespread and dangerous air pollutants: ozone, better known as smog, and particle pollution, often referred to as soot. Both pollutants can cause significant lung damage over time.

The report, released by the American Lung Association, also found that five out of 10 Americans are living in communities impacted by high levels of pollution in the form of more unhealthy ozone days, more particle pollution days and higher annual particle levels than in previous years.

The health organization, which tracks air quality data across the nation, released its 21st annual State of the Air report this week.

“The nation needs stronger limits on ozone and particle pollution to safeguard our health, especially our children and people with lung disease,” said JoAnna Strother, the Lung Association's director of advocacy for the Southwest region.

“Every family has the right to breathe clean air and the right to know when air pollution levels are unhealthy," she said. "So we're really telling the Trump administration to follow the science and set stronger limits on dangerous air pollution.”

The study doesn’t include the impact the COVID-19 stay-at-home restrictions have had on air quality, but Strother said the reduced pollution many cities are experiencing is only another indication that bold actions from both the private and public sectors could make a significant difference in air quality.

Report: Phoenix ranks 7th for worst pollution

For the report, the Lung Association analyzed air quality data from cities, counties, state, tribal and federal agencies between 2016 and 2018, then gave each city and county an air quality report card with a letter grade.

For the second year in a row, Phoenix ranked as the seventh most ozone-polluted metropolitan area in the country and received an "F" from the health organization.

MORE:Winter air really is worse in south, west Phoenix. Here's why

The city also jumped from 32nd place to seventh place for pollution from the smallest year-round particulate matter, tiny particles known as PM2.5 that infiltrate deep into the lungs and can cause severe health issues over time.

In Arizona, PM2.5 is primarily produced by wood burning in fireplaces and fireworks during the winter holidays, but also comes from car and truck exhaust.

Maricopa and Pinal Counties each received an “F” for number of days with high particulate matter pollution.

Part of the reason why Phoenix’s PM 2.5 count seems to have risen so sharply is because the holiday season of 2017-2018 was one of the worst on record, according to the Arizona Department of Environmental Quality.

“The main source of that particulate matter was smoke from burning wood in fire pits and fireplaces and setting off fireworks,” said Erin Jordan, a spokesperson for the agency in a press release. “A period of calm, cool weather created a stagnation event with little wind and no rain that led to the buildup of smoke over the Valley.”

Between Dec. 23, 2017, and Jan. 1, 2018, particulate matter from smoke exceeded the federal health standard six times, setting new daily records for five of those days. The levels of PM2.5 during that time were 77% higher than average. Jan. 1, 2018 was the highest exceedance on record.

Are stay-at-home orders helping pollution?

In the past month, many cities have reported significantly cleaner skies since stay at home orders were issued, but the effects underscore the need for action, Strother said.

“The big headline right now is that air quality has dramatically improved because of all of the stay-at-home orders,” she said. “I think it speaks to what happens when people do commit to driving less or even investing in mass transit or using energy efficient cars so that there's less emissions on the road.”

Strother described the pandemic as a brief moment in time that can give policymakers and the public a glimpse into what the result of certain measures to reduce air quality could be.

“It speaks to what could happen if people really committed to driving less, if employers allowed their workforce to work from home more,” Strother said. “So we're seeing this temporary pause on air pollution, which is good for lung health, but we need to keep in mind that at some point there will be a big spike in pollution again and we really need to double down on improving our air quality for the long term problem.”

CLEARER SKIES? Air pollution levels ease as people stay home, but heat could reverse trend

As the days get longer, ozone pollution will worsen in Phoenix. Most of Arizona's ozone is caused by vehicle exhaust, which produces nitrogen oxides, or NOx. Ozone, a colorless, odorless gas, forms when NOx and volatile organic compounds (VOCs) react in sunlight.

Global heating adds to the problem with an uptick of warmer temperatures across the country, which speeds up ozone production, Strother said. The three years of this report were three of the five hottest years on record.

How air pollution impacts us

The deadliness of COVID-19, a respiratory illness, and the plethora of studies linking air pollution with declining health and even death, is a further reminder of the need to act, she said.

New research links air pollution to the development of serious diseases, such as asthma and dementia. Ozone and particulate matter exposure have been linked to premature death. For example, a 2017 nationwide scientific study found that older adults faced a higher risk of premature death even when levels of ozone pollution remained well below the current national standard.

The Phoenix area's ozone has actually dropped 11.2 percent on average from 1990 to 2018, according to the Maricopa County Air Quality Department. Air quality experts point to two reasons for the decrease: The national Clean Air Act, which reached its 50th anniversary this year, and more fuel-efficient cars.

The report emphasizes the need for such regulations to remain intact and argues that the Trump administration’s attempts to dismantle the Clean Air Act and successes in weakening clean car standards are major hits to public health.

“Everyone has to play a role, but certainly the federal government needs to set stronger standards,” Strother said. “These are health protections that have been put in place that we really can't afford to roll back.”

Erin Stone covers the environment for The Arizona Republic and azcentral.com. Send her story tips and ideas at erin.stone@arizonarepublic.com and follow her on Twitter @Erstone7.

Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.