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Monitoring Overview

Ambient (outdoor) air monitoring refers to the collection and analysis of pollutants in physical air samples collected from one or more specific locations within an area of interest. Ambient air monitoring provides the most definitive answer to the question, “What is in the air?”

IDEM operates a statewide air monitoring network that includes air toxics monitoring sites at several locations in Indiana. IDEM’s air toxics monitor siting process includes an evaluation of emission sources and population density. IDEM maintains an in-house air toxics laboratory where it measures and analyzes monitored compounds in air samples it collects. IDEM enters the data into its Office of Air Quality Toxics Data Collection (OAQTDC) database and submits quality assured data to U.S. EPA’s Air Quality System (AQS), which is a database of ambient air monitoring data from around the nation. IDEM’s Air Toxics Data map provides links to data for each monitoring site. The Air Toxics Program provides a description of current air toxics monitoring sites.

The Air Toxics Program utilizes this air toxics monitoring data in routine monthly screenings for potential air quality problems in monitored areas and the ToxWatch Monitoring Data Analysis concerning potential impacts from air toxics. If monitoring data show air toxics concentrations may be higher than normal in a monitored area, IDEM may conduct an air risk assessment to further investigate potential sources of the chemical(s) of concern, determine how residents living, working and going to school in the area may be exposed to harmful levels, identify what if any increased health risks they may face, and identify what if any emission reductions may be necessary. In some cases, IDEM may conduct additional air toxics monitoring as part of a special studies.

Although monitoring provides accurate measurements of pollutants in the air, monitoring has certain limitations because it generally requires expensive equipment that may need to operate for months or years before sufficient data is collected in order to reach conclusions about air quality. In addition, results are limited to the specific locations being monitored and the specific timeframes for which samples are collected. Another alternative used to provide useful data screening, air risk assessments, and air quality evaluations is modeling. Modeling is a mathematical simulation of air quality using a computer program and inputs such as emissions data. The benefits of modeling are that it is less expensive than air monitoring and enables air risk staff to explore air quality at thousands of points, over multiple years, in a matter of hours or days. As such, air risk staff may utilize a combination of monitoring and modeling data to analyze air quality impacts from air toxics.