A pair of air pollution sensors in Indiana have become casualties of the U.S. Environmental Protection Agency’s budget crunch, and the nation’s long-term environmental monitoring could suffer as a result.

The EPA plans to suspend operations for 41 air quality and atmospheric deposition monitoring sites throughout the country, including two located in Indianapolis and Roush Lake in Huntington County, as part of an effort to reduce costs for its 2023 budget.

“These sites provide air quality data on ozone, nitrogen (e.g., ammonia, ammonium, nitrate), sulfur and other pollutants in rural and ecologically sensitive areas. The agency has taken this action in response to current fiscal constraints,” the EPA told the Indiana Environmental Reporter in an email. “EPA’s Office of Atmospheric Programs will undertake a scientific review of long-term rural air quality and atmospheric deposition monitoring assets to inform next steps.”

The EPA requested $11.9 billion for its yearly budget, about 9% of which will be allocated to improve air quality. Accounting for inflation, the EPA has experienced a downward trend in its buying power since 2000, except for a large budget infusion in the 2010 fiscal year.

Despite budgeting more money for the agency, the EPA has less buying power than it did during the Trump administration, necessitating cuts in some agency programs, like the two sensor sites in Indiana.

The sensor sites collect information on ammonia gas concentrations for the Ammonia Monitoring Network, a part of the National Atmospheric Deposition Program. The EPA has said the data collected by the NADP and its own long-term monitoring networks the “cornerstone for tracking the extent to which emissions reductions are having their intended effects on improving human and ecosystem health.”

Ammonia is the most prevalent base gas in the atmosphere, but is also released from agricultural and industrial sources, emissions from vehicles and the loss of nitrogen gas from soils, vegetation and oceans.

The largest source of ammonia pollution in the country comes from the agricultural sector, primarily from animal waste and commercial fertilizer application. Indiana’s AMoN sensors detected yearly spikes in ammonia levels in May and June between 2013 and 2022, right at the tail end of the soybean and corn planting season.

Excess ammonia can negatively affect waterways through acidification, where ecosystems become more acidic, and eutrophication, the excess enrichment of aquatic ecosystems by phosphorus and nitrogen nutrients that can lead to oxygen loss or the production of algae.

Ammonia also mixes with other gases in the air to form particulate matter pollution, pollution so small that it can enter the human bloodstream.

Particulate matter pollution can cause cardiovascular effects, like cardiac arrhythmias and heart attacks, and respiratory effects, like asthma attacks and bronchitis. Exposure to the smallest forms of fine particulate matter has been linked with an increased risk of COVID-19 death in the U.S.

The suspension of the sites will create a hole in the information network that could affect the EPA’s ability to warn the state to prepare for ammonia effects.

“[The measurements are] used in models that follow air quality for the regions and nation and go into model estimates of dry deposition of nitrogen, which is influential in several different environmental issues,” said NADP coordinator David Gay.

“With the suspension of these two monitoring sites, the entire northern half of Indiana will have no monitoring for ammonia within the NADP/AMoN. If this situation persists, then the trend determinations will not be complete, nor will the site be used in our annual average data products and the data will not qualify for a year’s worth of data and, therefore, any research using this data won’t be complete. Additionally, modeling scenarios for current and future time periods will not have this data and result in less-than-ideal modeling.”

The Indiana Department of Environmental Management said it has not used data from the Washington Park or Roush Lake sites for its air programs, so the suspension will not affect IDEM’s ability to evaluate particulate matter levels.

The NADP will still have one active AMoN sensor in Vincennes. The EPA will continue to operate two Clean Air Status and Trends Network sensor sites, which monitor pollutant concentrations, atmospheric deposition and ecological effects due to changes in air pollutant emissions.