Rider Trail I-70, Near Road, Air Monitoring Site

The Rider Trail site off Interstate 70 at Exit 231B, Earth City, is the second air monitoring station in the St. Louis area to provide near-road data. The site is in compliance with the one-hour NO₂ standard of 100 parts per billion (ppb). The department began monitoring SO₂ at the site in May 2016. Preliminary data show that the site is in compliance with the one-hour SO₂ standard of 75 parts per billion (ppb). Both pollutants negatively affect respiration.

Pollutants

Nitrogen Dioxide

Nitrogen dioxide is a foul-smelling gas. It comes primarily from the burning of fossil fuels — coal, oil and gas. NO₂combines with volatile organic compounds (VOCs) in the presence of sunlight and heat to create ozone. (VOCs are compounds with carbon that easily become vapors or gases.)

In 2010, EPA revised the one-hour NO₂ standard to 100 parts per billion. An area is in compliance if the design value is at or below the standard. The one-hour standard is based on a three-year design value, which is calculated by taking the 98th percentile of the daily high one-hour average concentrations recorded each year, for three years, and averaging the three years together. The annual standard of 0.053 parts per million is based on the annual arithmetic mean and is not to be exceeded.

Departmental information about nitrogen dioxide (NO₂)

2010 standard and related documents

Air Quality Analysis Nitrogen Dioxide - Weekly Monitor Data

One-hour NO₂ design values
Eight highest one-hour NO₂ values, year-to-date
Map of monitoring sites

Preliminary one-hour NO2 data from all sites, parts per billion, CST

Air Pollutant Design Values Quarterly Report - Nitrogen Dioxide

Additional information about nitrogen dioxide and state planning efforts

Table of Symbols - Flags Air Monitoring Data

Technical issues can affect ability to deliver quality data. Access a table of symbols with explanation of the problems they represent.

Nitrogen dioxide preliminary one-hour averages from Rider Trail

NO₂ data in the fifth column
Data from previous 10 days through current data
Central Standard Time

Sulfur Dioxide

EPA not only established a new one-hour standard in 2010, but it also introduced a new form for determining compliance. The new form requires three years of data — the average SO₂ concentration from each hour of the year. The department and EPA calculate the design value, using the 99th percentile of one-hour daily maximum concentrations, averaged over three years.

Departmental information about sulfur dioxide (SO₂)