Study documents unhealthy noise in Portland, provides research framework for other cities

CORVALLIS, Ore. – A groundbreaking study led by Oregon State University scientists shows that multiple Portland neighborhoods have levels of noise that are likely unhealthy.

The research, the first of its kind in the United States, provides a framework for studying noise pollution in other cities in the U.S., which lags behind European nations in examining the effects of noise on human health.

The project directed by assistant professor Matthew Bozigar and graduate student Carson Mowrer of the OSU College of Health indicates that the loudest parts of Portland are also the most socially vulnerable, with lower incomes and higher proportions of non-white residents.

Findings of the research, which involved sound pressure level monitoring at a mix of locations and a novel modeling technique based on machine learning, were published in the Journal of Exposure Science and Environmental Epidemiology.

“Many people in the United States still think of noise as just a nuisance, not a real health risk,” said Bozigar, an environmental epidemiologist. “But in Europe, research shows that noise is the second biggest environmental threat to health after air pollution – linked to more illness and early death than things like unsafe water, lead, chemicals or other pollutants.”

European studies suggest that noise exposure is associated with sleep disturbance, cognitive impairment, mental health disorders, high blood pressure, cardiovascular disease, metabolic disorders, hearing impairment/loss and adverse pregnancy outcomes, he said. In the U.S., however, far less is known about the health effects of noise because very little research has been done here, and since American cities, transportation systems and traffic patterns are significantly different from those in Europe, it’s not fair to assume the same levels of risk apply.

“And most communities, including Portland, don’t have a clear understanding of how noisy they really are,” Bozigar said.

As a starting point for changing that, a collaboration that included OSU’s Andrew Larkin and Perry Hystad partnered with the Multnomah County Health Department on one of the most comprehensive citywide noise assessments conducted in the U.S. Recording 24 hours a day with high-quality, low-cost digital monitors, the scientists captured critical patterns, especially at night when noise can disrupt sleep and have some of its largest health impacts.

The scientists found that most of the monitored locations in Portland, a 145-square-mile city with 635,000 residents and a metro area population of more than 2.1 million, exceeded noise guidelines set by both the U.S. Environmental Protection Agency and the World Health Organization.

“The analysis helped us identify several distinct types of noise environments across the city, such as consistently quiet areas, areas with loud but irregular bursts of noise, and areas with steadily high noise levels,” Mowrer said. “These patterns didn’t always align with traditional city zoning categories, like residential or commercial zones, and in some cases could differ even from one block to the next. The strongest factor influencing noise patterns seemed to be how close a location was to a high-traffic road.”

The findings provide a much-improved understanding of noise exposure across diverse neighborhoods and land uses in a medium-large U.S. city, the researchers say, and the datasets serve as a foundation for both local decision-making and future health studies. Further research on noise exposure and the ways people experience noise in cities could help planners and public health officials take more targeted and effective steps to reduce exposure, particularly in the places that need it most.

“Even as a native of the metro area, I saw many new parts of the city I hadn’t seen before while setting up and taking down the sound level monitors,” Mowrer said. “I spoke with quite a few residents of the neighborhoods we visited who were curious and supportive of the project. Some of them shared their own experiences with noise and how it had affected their lives.”

Field measurements began in August 2023 and ran through August 2024. Scientists from the Oregon Health & Science University-Portland State University School of Public Health, Boston University and the Multnomah County Health Department also contributed to the research, which was funded by a Centers for Disease Control and Prevention grant awarded to Multnomah County.

This study is part one of a two-part project; the second manuscript, not yet published, will provide a citywide noise picture of Portland at a resolution of 10 meters, and Multnomah County is preparing an interactive online map to share that information.