Community air quality monitoring shows periods of ‘unhealthy’ air in Sioux City

Exposure to the type of air pollutants measured by the monitors, particulate matter 2.5, or PM2.5, can contribute to “a wide range of adverse health outcomes” including respiratory illnesses and cardiovascular disease, strokes and certain types of cancer. 

SUBSCRIBE: GET THE MORNING HEADLINES DELIVERED TO YOUR INBOX.

While the report notes multiple pollution sources impacting PM2.5 levels in the region, it also finds correlation between periods of high PM2.5 levels and reported emissions from the George Neal North and George Neal South power plants. 

One of Iowa Environmental Council’s main priorities is pushing for continued transition from coal-powered energy to renewable energy sources like wind and solar. In a news release about the report, council staff members called for a phaseout of the coal plants, which are both owned and operated by MidAmerican Energy Company. 

“Air pollution is an issue across Iowa, but the effects are not felt uniformly,” Jordan Oster, the council’s energy program director said. “The Sioux City community is bearing the health impacts of MidAmerican Energy’s dirty coal plants. We need our utilities to transition away from coal, and until they do so, our utilities should be held responsible for the cost of their pollution.” 

Geoff Greenwood, the media relations manager for MidAmerican Energy Company, said in a statement the report draws “broad conclusions” on the causes of local air quality conditions. 

“To put it plainly, the report encourages readers to focus on a few selected sources while overlooking the fact that many other factors may have contributed to the measured air quality conditions,” Greenwood said. 

What are PM2.5 monitors?

Iowa Environmental Council helped residents install six PurpleAir monitors for PM 2.5 in Woodbury County shortly after the council published a report that listed the county as having the highest rates of asthma in adults over 18, compared to other Iowa counties. 

PurpleAir monitors are wifi-enabled monitors that measure particulate air pollutants and report to a global air quality database to enable citizen-led, near real-time monitoring of air quality. 

Particulate matter is a mixture of solid and liquid particles in the air, like dust, dirt, smoke and other smaller particles. PM2.5 refers to “fine inhalable particles” with a diameter of 2.5 micrometers or smaller – about 30 times smaller than the diameter of a single human hair, according to the U.S. Environmental Protection Agency. 

EPA holds these smaller particles pose the greatest health problems as the fine particles can be absorbed “deep” into the lungs and even enter the bloodstream. Exposure to these particles, according to EPA, is linked to aggravated asthma, premature death in people with heart or lung conditions, heart attacks and decreased lung function. 

A year’s worth of data from the monitors shows a “highly synchronized, city-wide problem” according to the report. 

“Rather than experiencing isolated local incidents, the entire Greater Sioux City area undergoes simultaneous, acute pollution events,” the report said. 

A sensor installed on Market Street in downtown Sioux City showed a “concerning pattern of long-term exposure” where PM2.5 levels formed a “continuous block of pollution” through the spring and summer months rather than periodic spikes that exceed EPA thresholds for “unhealthy” and “unhealthy for certain groups.” 

Sources of PM2.5 

Some sources of particulate matter are directly emitted, but most, per EPA, are in the atmosphere as a result of “complex reactions” of chemicals emitted from power plants, industries and vehicles, like sulfur dioxide SO2 and nitrogen oxides, NOx. 

The report tracked a correlation between increased SO2 and NOx emissions and higher PM2.5 levels in the region. This correlation, it argues means a connection between increased coal plant emissions and PM2.5 levels. 

“Although this correlation does not equal causation, it does underscore the coal plants’ role as a key contributor to regional particulate pollution during this timeframe,” the report said. 

It also notes that things like wildfire smoke contribute to regional increases in fine particulate matter and that other local sources, like industrial facilities, commercial operations, transportation “also contribute to ambient air quality.” 

A chart of major local polluters shows that a fertilizer facility actually pollutes more than either of the George Neal power plants, though not more than the emissions of the two combined. 

“Recognizing multiple pollution sources does not diminish the severe impact of coal emissions on community air quality,” the report said. “Instead, the data reveal a layered environment in which coal emissions elevate baseline PM2.5 levels and stack on top of other local sources of pollution.” 

Greenwood with MidAmerican said the report’s conclusions are “based primarily on correlations.” He said the report acknowledges the role that other emission sources have on PM2.5 levels but  “inaccurately attributed air quality conditions to a single source without a comprehensive evaluation of all contributing factors.”

“Some of those factors could have had an equal or even greater impact, but the report does not quantify their contribution,” Greenwood said. “As a result, readers may be left with the impression that these other influences were insignificant when, in reality, the report does not provide the analysis needed to support that conclusion.” 

Greenwood said all MidAmerican facilities “comply with federal and state environmental laws and regulations” and that the company will continue to do so and “invest in cleaner energy resources, and provide the safe, reliable and affordable energy our customers depend on every day.” 

He said the company’s investments into wind energy have related to considerable reductions in carbon dioxide, sulfur oxides and nitrogen oxides emissions. 

“Similar reductions in particulate matter emissions have occurred during the same timeframe,” Greenwood said. 

Health impacts and recommendations 

The report notes that long-term exposure to elevated PM2.5 pollution is linked to increased hospitalizations, chronic illness and mortality. 

Asthma-related emergency room visits have increased in Woodbury County over the past several years, according to the report.

Data from the Iowa Department of Health and Human Services, however, show Woodbury County rates of emergency room visits due to asthma are fairly consistent with overall rates for the state. The rate of asthma hospitalizations has been higher in Woodbury County than the state average since 2022, however. 

The Iowa Environmental Council report called for coordinated action to “reduce emissions, improve exposure monitoring, and strengthen public health protections.” 

Recommendations in the report include: expanding air quality monitoring, adding air pollution exposure screenings in healthcare assessments, sending public text message alerts during air quality index spikes, adopting electric vehicles, advocating for emissions controls and clean energy investments. 

The council will host a free presentation and panel on the report and air pollution health effects Thursday from 5:30 to 6:30 at the Sioux City Public Museum. 

SUPPORT: YOU MAKE OUR WORK POSSIBLE